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522 Cards in this Set
- Front
- Back
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invertebrate
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an animal that lacks a backbone
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What percentage of known animal species are invertebrates?
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95%
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What differentiates animals from other kingdoms?
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Body plans
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body plan
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a set of morphological and developmental traits
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radial symmetry
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radiate from center; any slice through central axis divides into mirror images
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bilateral symmetry
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only one slice through central axis divides into mirror images
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bilateral symmetry implies...
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a right and left side, a dorsal and ventral side, an anterior and posterior end, and usually cephalization
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cephalization
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the development of a head
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How do bilateral animals usually move?
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Actively
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What kind of nervous system do bilateral animals tend to have?
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A central nervous system
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Bilateria include the (majority/minority) of animal species
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majority
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Bilaterians are (diploblastic/triploblastic)
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triploblastic
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diploblasts
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have the germ layers ectoderm and endoderm
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triploblasts
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have the germ layers ectoderm, endoderm, and mesoderm
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ectoderm
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the germ layer covering the embryo's surface
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endoderm
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the innermost germ layer; lines the developing digestive tube (the archenteron)
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mesoderm
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the intervening layer
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Many triploblastic animals possess what?
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a body cavity
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coelom
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a true body cavity; derived from mesoderm
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coelomates
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animals that possess a true coelom
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Lophotrochozoa
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bilateral symmetry and triploblastic; name derives from two morphological characteristics:
lophophore and trochophore |
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Lophophorates
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2 phyla under lophotrochozoa; includes ectoprocts and brachipods
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lophophore
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crown of ciliated tentacles used for feeeding
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ectoprocts
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sessile, colonial; hard exoskeleton; reef builder; 4,500 species
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brachiopods
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hinged shell; dorsal and ventral halves (unlike molluscs that have lateral halves); 335 species
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flatworms
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phylum under lophotrochozoa; 20,00 species, includes planarians and tapeworms;
thin bodies between dorsal and ventral surface acoelomates |
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acoelomates
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no body cavity between digestive tract and outer body wall
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worms are (mono/para/poly)phyletic
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paraphyletic
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planarians
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gastrovascular cavity with only one opening, many fine branches
light-sensitive eyespots and centralized nerve nets gas exchange takes place across the surface hermaphrodites (sexual reproduction by cross-fertilization, exchange sperm) asexual reproduction through fission and regeneration of missing parts |
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tapeworms
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parasites of vertebrates; leave the host's body in feces, food contamination (cysts in undercooked meat)
lack a digestive system, absorb nutrients from the host's intestine fertilized eggs, produced by sexual reproduction attach to the host with hooks and sucker |
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rotifers
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1 phylum under lophotrochozoa; 1,800 species; very tiny; have an alimentary canal
pseudocoelomates some reproduce by parthenogenesis (these can enter long periods of dessication) |
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alimentary canal
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2 openings, separate mouth and anus
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pseudocoelomates
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body cavity partially lined by tissue derived from mesoderm
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parthogenesis
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offspring from unfertilized eggs
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annelids
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1 phylum under lophotrochozoa; 16,500 species
segmented worms coelomates from very tiny to very long |
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classes of annelids
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oligochaetes, polychaetes, leeches
distinguished by the type of chaete and the presence or absence of parapodia |
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chaete
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bristles made of chitin, polymer of NAG
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parapodia
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almost feet, paddle-like or ridge-like
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oligochaetes
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"few long hair"; no parapodia, reduced head
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polychaetes
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"many long hair"; parapodia with chaete; well developed head
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leeches
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no chaete; reduced segmentation; parasites and predators
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anatomy of an earthworm
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internal structures (partitioned by septa) are repeated within each segment
some reproduce asexually by fragmentation followed by regeneration |
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molluscs
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1 phylum under lophotrochozoa; 93,000 species (second among animals, after arthropods)
soft-bodied animals most are protected by a hard shell, some (slugs, octopuses) lost during evolution most are aquatic, some (snails, slugs) are terrestrial most have separate sexes, some (snails) are herms |
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basic body plan of a mollusc
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most molluscs have a muscular foot, visceral mass, and mantle
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muscular foot
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used for movement
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visceral mass
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contains most of the internal organs
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mantle
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secretes shell
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radula
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backward-curved teeth used by many molluscs for feeding; slide back and forth, scraping and scooping like a backhoe
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classes of molluscs
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chitons, gastropods, bivalves, cephalopods
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gastropods
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slugs, snails
3/4 of all molluscs distinct head with eyes |
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bivalves
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clams, oysters, mussels, scallops
suspension feeders sedentary no head no radula |
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cephalopods
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octopi, squids, cuttlefish, nautiluses
distinct head with eyes well-developed sense organs, complex brain closed circulatory system active predators (tentacles) shell is reduced or internal (only nautiluses have external shells) |
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ammonites
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shelled cephalopods that went extinct 65.5 mya
dominant invertebrate predators during cretaceous period |
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chitons
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shell with 8 plates, no head
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Ecdysozoans
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the most species-rich animal group
two largest phyla are nematodes and arthropods have a cuticle and undergo molting |
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cuticle
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tough coat that covers the body
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molting
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cuticle is shed and a new larger one is produced
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larva
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sexually immature and morphologically distinct from the adult
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metamorphosis
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transition from larval stage to sexually mature stage (adult)
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nematodes
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1 phylum under ecdysozoans; 25,000 species
non-segmented worms pseudocoelomates important role in decomposition sexual reproduction - female is larger lack circulatory system |
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Caenorhabitis elegans
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nematode and model organism in research
1 mm in length and transparent (good for microscopy) 959 cells in adult herm, 1031 cells in adult male ~20,000 protein-coding genes free-living organisms in the soil, eats bacteria can be frozen simple nervous system |
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What was the first multicellular eukaryote to have its full genome sequenced?
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c. elegans
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GFP
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green fluorescent protein
absorbs blue light and emits green light |
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What is GFP used for?
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method to study protein localization
can be fused to a protein of interest and the localization of the resulting fusion analyzed by fluorescent microscopy |
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RNAi
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RNA interference
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What is RNAi used for?
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method to study gene function
when C. elegans is fed with bacteria expressing RNA complementary to the gene of interest, the function of that gene is lost in the animal |
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arthropods
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1 phylum under ecdysozoans; over 1,000,000 species
name means jointed feet hard exoskeleton and jointed appendages segmented coelomates |
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arthropod origins
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body plan dates to the Cambrian explosion
early arthropods (trilobites) have extensive segmentation, but little variation from segment to segment |
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Cambrian explosion
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appearance of many major groups of living animals (535-525 mya) = sudden increase in diversity
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Paleozoic Era
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(542-251 MYA)
Cambrian explosion rise in atmospheric oxygen new predator-prey relationships evolution of the hox gene complex diversity continued to increase, punctuated by mass extinctions |
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hox genes
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homeotic genes; control the identity of body parts
most animals have them highly conserved but can produce a wide diversity of morphology provide positional information during development if expression is perturbed, body parts can be produced at the wrong location |
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arthropod evolution
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decrease in the number of segments
segments fused and appendages became specialized changes may have been caused by changes in hox gene sequence or regulation |
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external anatomy of an arthropod
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pincers - defense
mouthparts - feeding antennae - sensory reception walking legs swimming appendages cephalothorax (head and thorax) abdomen |
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What kind of circulatory system do arthropods have?
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open circulatory system
has a hear (porous pump) and arteries fluid is hemolymph |
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Subphyla of arthropods
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chelicerates
myriapods hexapods crustaceans |
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chelicerates
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horseshoe crabs, scorpions, spiders, mites, ticks
"cheilos" = lips, "cheir" = arm chelicerae = claw-like feeding appendages (pincers or fangs) two-part body: anterior cephalothorax + posterior abdomen lack antennae, have simple eyes |
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arachnids
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scorpions, spiders, ticks and mites
cephalothorax with six pairs of appendages (4 pairs of legs) chelicera have poison glands and digestive juices use pedipalp for sensing and feeding |
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myriapods
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millipedes (herbivores)
centipedes (carnivores) |
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hexapods
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insects
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crustaceans
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crabs, lobsters, crayfishes, shrimps, barnacles
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insects
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oldest fossils from ~416 mya (Devonian period)
body has three regions: abdomen, thorax, head most reproduce sexually and have separate males and females (no herms) recognize members of their own species by bright colors, sound, or odor beneficial as pollinators harmful as carriers of disease (vectors), or pests of crops |
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anatomy of a grasshoper
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three pairs of legs
cerebral ganglion (antennae, eyes, and other sense organs concentrated on the head) insect mouthparts (include mandibles, which grasshoppers use for chewing) |
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flight
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one key to the great success of insects
can escape predators, find food, disperse to new habitats much faster one or two pairs of wings form the dorsal side of the thorax fly without sacrificing walking legs |
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incomplete metamorphosis
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when young (nymphs) resemble adults but are smaller and lack wings
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complete metamorphosis
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when larval stage looks entirely different from adult stage
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adult (end of metamorphosis)
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specialized for dispersal and reproduction
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drosophila melanogaster
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a model animal
fruit fly, vinegar fly 3 mm long 14,000 genes used to study developmental genetics maternal > gap > pair rule > segment polarity |
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deutorostomes
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characterized by radial cleavage, enterocoelous development, anus develops from blastospore
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protostome vs. deuterostome: cleavage (protosome)
8 cell stage |
protostome has spiral cleavage
planes of division are diagonal to the vertical axis of the embryo determinate |
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protostome vs. deuterostome: cleavage (deuterostome)
8 cell stage |
deuterostome has radial cleavage
planes of division are parallel or perpendicular to the vertical axis of the embryo indeterminate (each cell retains the capacity to develop a complete embryo) |
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protstome vs. deuterostome: coelom formation
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protostome: solid masses of mesoderm split and form coelom
deuterostome: folds of mesoderm form coelem |
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blastospore
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indentation formed during gastrulation
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protostome vs. deuterostome: fate of blastospore
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protostome: mouth develops from blastospore
deuterostome: anus develops from blastospore |
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echinoderms and chordates are...
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deuterostomes
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echinoderms
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slow-moving or sessile marine animals
"echin" = spiny, "derma" = skin endoskeleton of hard calcareous plates water vascular system separate male and female individuals (release gametes into water) radiate from the center (often as 5 spokes), but larvae have bilateral symmetry |
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water vascular system
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network of hydraulic canals (locomotion, feeding and gas exchange)
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classes of echinoderms
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sea stars
brittle stars sea urchins feather stars sea cucumbers |
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water vascular system of a sea star
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ring canal + 5 radial canals
gills are responsible for gas exchange water flows in and out of madreporites |
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vertebrates
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have a backbone
52,000 species include the largest organisms ever to live on earth mostly aquatic until 365 mya evolution of legs and feet, move to land |
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vertebrae
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series of bones that make up the vertebral column (backbone)
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chordates
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first appeared during the cambrian period
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Major Charactersistics of chordates
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notochord
nerve cord pharyngeal slits tail (some of these may only be present during embryonic development) |
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notochord
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longitudinal, flexible rod
located between digestive tube and nerve cord provides skeletal support (in most vertebrates, a more complex skeleton develops) |
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nerve cord
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dorsal, hollow
usually solid and ventral in invetebrates |
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pharyngeal slits
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pouches separated by grooves
water can enter the mouth without passing through digestive tract chordates have pharyngeal slits, vertebrates have gill slits |
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pharynx
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organ located posterior to mouth in digestive tube
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tail
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muscular and post-anal
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cephalochordates
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chordates with a brain (can be primitive, swollen tip on the anterior end of nerve cord)
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lancelets
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cephalochordates; marine suspension feeders
have a blade-like shape |
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early chordate evolution
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ancestral chordates may have resembled lancelets
the same hox genes are expressed in the nerve cord tip of the lancelet and in the brain of the vertebrate embryo |
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genes associated with transmission of nerve impulses are unique to
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vertebrates
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genes associated with the heart and thyroid are common to
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all chordates
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tunicates (urochordates)
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exhibit chordate characteristics during their larval stage
"sea squirts" - marine suspension feeders draw in water through an incurrent siphon, filtering food particles shoots water through excurrent siphon |
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What organism is a model tunicate?
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Ciona intestinalis
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craniates
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chordates with a cranium (skull) (head has evolved independently in other lineages)
pharyngeal clefts evolved into gill slits more muscular than tunicates and lancelets have two clusters of hox genes heart with at least two chambers red blood cells with hemoglobin kidneys (to remove waste products) |
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craniates in the fossil record
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Haikouella - eyes and a bran but no skull
Haikouichthys - skull, true craniate 530 mya (Cambrian) |
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hagfish
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a craniate; head with small brain
eyes sensory organs (ears, nasal opening) skull (cartilage) active predation; bottom-dwelling scavenger lack jaws and vertebrae not actually a fish |
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neural crest
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a collection of cells near the dorsal margins of the closing neural tube in an embryo; the source of many unique vertebrate characters (teeth, some of the bones and cartilage of the skull, dermis of the facial region, several types of neurons)
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lampreys
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the oldest living lineage of vertebrates
skeleton made of cartilage cartilaginous pipe around notochord with dorsal extensions partially enclosing the nerve chord jawless mouth notochord remains the main axial skeleton |
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cartilage
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stiff matrix of proteins (usually includes collagen, except in lampreys)
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origin of teeth
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mineralization of the body began in the mouth
transition of feeding mechanisms? ingestion of larger preys conodont ("cone teeth") late cambrian (500 mya) |
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gnathostomes
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have a mouth with jaws (jawed vertebrates)
"gnathos" = jaw, stoma = mouth additional duplication of hox genes (4 clusters) enlarged forebrain (for smell and vision) mineralized endoskeleton |
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jaws
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hinged structures with teeth
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placoderms
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early gnathosomes (450 mya)
paired fins and tail lead to efficient swimming |
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chondrichthyans
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cartilage fishes; 1,000 species
"chondr" = cartilage, "ichthys" = fish among the largest and most successful predators blacktip reef shark southern stingray |
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blacktip reef shark
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paired pectoral and pelvic fins
sharp vision, but can't distinguish colors more dense than water, sinks if it stops swimming |
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southern stingray
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flattened bottom-dwellers
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ray-finned fishes
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fins with long, flexible rays, modified for maneuvering and defense (>27,000 species)
ossified endoskeleton (bony fish) breathe by drawing water over 4-5 pairs of gills covered by operculum control of buoyancy by swim bladder most species are oviparious yellowfin tuna, sea horse, fine-spotted moray eel |
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yellowfin tuna
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fast-swimming, schooling fish
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sea horse
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male carries the young during embryonic development
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fine-spotted moray eel
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predator that ambushes prey (from crevices in coral reef)
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operculum
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protective body flap
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swim bladder
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air sac, lung derivative
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modes of embryo development
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oviparous, ovoviviparous, vivparous
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oviparous
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eggs hatch outside the mother's body; fertilization may be either internal or external
most fishes, amphibians, reptiles (including birds) |
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ovoviviparous
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the embryo (in an egg) develops within the mother's body
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viviparous
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the embryo develops within the mother's uterus and is nourished through a yolk sac placenta from the mother's blood (mammals)
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zebrafish
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a model vertebrate
tropical freshwater large quantities of eggs are produced embryos are transparent (good for microscopy) develop quickly (24 hours) |
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lobed fins
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pectoral and pelvic fins have rod-shaped bones surrounded by a thick layer of muscle
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coelacanth
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lobe-fin fish; believed extinct until caught in 1938 off the Comoros Islands and again in 1999 near Indonesia
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lungfishes
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only 6 species
modified swim bladder (lungs) functions: buoyancy, absorbs oxygen, removes waste live in stagnant ponds and swamps |
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When did the first terrestrial vertebrate appear?
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385 mya
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tetrapods
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four feet, move to land; terrestrial vertebrates
pectoral and pelvic fins evolved into limbs and feet with digits bones of the pelvic girdle (hind legs) fused to backbone no gill slits, evolved into ears (for detecting airborne sounds), glands and other structures use lungs to breath air neck and shoulders, to allow separate movement of the head |
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Tiktaalik
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a "fishapod"
fish: scales, fins, gills and lungs tetrapod: neck, ribs, fin skeleton, flat skull, eyes on top of skull |
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amphibians
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both ways of life (aquatic and terrestrial); refers to the metamorphosis of frogs
salamanders frogs caecilians |
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frogs
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tail-less amphibians; 5,400 species
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tadpole
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aquatic, larval stage (fishlike tail and internal gills), herbivore
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frog (stage)
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terrestrial, legs, lungs, carnivore
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salamanders
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amphibians with tails; 550 species
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caecilians
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legless amphibians; 170 species
absence of legs is a secondary adaptation resemble earthworms, legless and blind |
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amniotic egg
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embryo sits inside an amniotic cavity with amniotic fluid
usually has a shell (except in mammals) |
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shell (amniotic egg)
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inflexible
made of CaCO3 in birds Permeable to oxygen and carbon dioxide |
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amniotic egg has...
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extraembryonic membranes
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extraembryonic membranes
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specialized membranes protecting the embryo
amnion chorion allantois yolk sac |
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amnion
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surrounds a fluid-filled cavity
cushions against shocks |
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chorion
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gas exchange
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allantois
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disposal sac for certain metabolic wastes produced by the embryo
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yolk sac
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nutrients; blood vessels transport nutrients into the embryo
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reptiles
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scales that contain keratin create a waterproof barrier to prevent dehydration in dry air
rely on lungs for gas exchange (except turtles) oviparous (lay eggs on land but fertilize internally) most (except birds) are ectothermic |
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keratin
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fibrous protein, also found in human skin
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ectothermic
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absorption of external heat as the main source of body heat, "cold-blooded"
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origin of reptile
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oldest fossil 300 mya (carboniferous period, mid to late paleozoic)
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mesozoic era
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251-66 mya = age of reptiles (dinosaurs)
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lepidosaurs
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include tuataras and squamates
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tuataras
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found only on a few islands of the coast of New Zealand
eggs are eaten by rodents |
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squamates
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include lizards and snakes
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lizards
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most numerous and diverse reptiles after birds
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snakes
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legless (some species retain vestigial pelvic and limb bones)
carnivorous have toxins in their sharp teeth |
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archosaurs
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include crocodilians and birds
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alligators and crocodiles
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represent adaptation to aquatic habitats
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birds
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reptilian anatomy extensively modified by adaptation to flight; 10,000 species
wings and feathers lack a urinary bladder, only one ovary (small gonads), toothless, light skull, hollow bones flying requires great expenditure of energy birds are endothermic |
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endothermic
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keep the body warm through metabolism (hot blooded)
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archeopteryx
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fossil closely related to birds
feathers with vanes (evolved before powered flight) retains teeth, clawed digits and long tail |
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avian wing
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wings evolved from forelimbs
feathers are made of keratin honeycomb internal structure (air-filled bones) |
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mammals
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mammary glands produce milk for offspring
have hair >5,300 species endothermic (high metabolic rate, fat layer under skin to retain body heat) circulatory system with four-chambered heart respiratory system with diaphragm (muscle) to help lungs ventilate large brain specialized teeth for shearing and grinding long duration of parental care |
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synapsids
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have single hole (temporal fenestra) on each side of the skull
mammals are synapsids |
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diapsids
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have two holes on each side of the skull
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evolution of mammalian ear
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quadrate and articular bones become incorporated into the middle ear
quadrate became incus articular became malleus |
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monotremes
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one species of platypus and four species of echidnas (spiny anteaters)
only mammals that lay eggs have hair and produce milk but lack nipples |
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marsupials
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mammals with a pouch (marsupium)
born very early and complete development while nursing |
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eutherians
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placental mammals
marsupials also have a placenta but it is less complex longer period of pregnancy (complete embryonic development in uterus) |
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placenta
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structure formed by the extraembryonic membranes and the uterus; facilitates diffusion of nutrients from the mother's blood into the embryo
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primates
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lemurs, tarsiers, anthropoids (monkeys and apes)
hands and feet adapted for grasping opposable thumb digits with flat nails instead of claws large brain and short jaws developed parental care and social behavior |
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opposable thumb
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big toe separated from other toes
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hominins
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species that are closer to humans than chimpanzees
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humans
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bipedal
large brain (language, symbolic thought, manufacture and use of complex tools reduced jawbones and canine teeth shorter digestive tract genomes of chimpanzees and humans are 99% identical |
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bipedalism
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stand upright and walk on two legs
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paleoanthropology
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study of human origins
several species of hominins coexisted, only one lineage survives today (us, homo sapiens) |
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oldest hominin fossil
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Sahelanthropus tchadensis
6-7mya reduced canine teeth small brain |
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"Ardi"
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Ardipithecus ramidus
4.4 mya reduced canine teeth bipedal, but still with grasping feet small brain |
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"Lucy"
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Australopithecus afarensis
3.2 mya walked fully erect small brain |
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The Homo genus
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oldest fossils ~2.4 mya
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Homo ergaster
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1.7 mya
fully bipedal short and straight fingers (probably did not climb trees) large brain |
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Homo sapiens
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oldest fossil 160,000 ya
Found in Ethiopia (2003) |
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biogenesis
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every living organisms comes from a pre-existing living organism (single root, vertical transmission)
tree of life, one root |
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heterogenesis
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the belief that some life form can arise spontaneously from non-living matter (spontaneous generation, many roots)
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Aristotle
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new animals arise whenever vital heat was enclosed in anything; animals can also come from parents, but not of different kinds
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spontaneous generation controversy
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Pasteur challenged spontaneous generation
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What makes a good experiment?
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novelty
impact (universality, simplicity) not just descriptive, but predictive power quality of the data and controls objectivity (validity of the interpretation) reproducibility |
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Jan Baptist van Helmont
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recipe for mice; cover wheat with a soiled shirt for 21 days
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Francesco Redi
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physician at the court of the Medici
poet and naturalist all worms found in meat were derived directly from the droppings of flies conducted the first modern experiment in biology by leaving meat exposed and covering meat and then testing for the presence of maggots |
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systematics
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branch of biology that classifies organisms and determines their evolutionary relationships
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Carolus Linnaeus
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Systema Naturae - a formal classification of all living things
hierarchical organization binomial nomenclature |
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taxonomy
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ordered division and naming of organisms
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taxon
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taxonomic unit at any level
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Hooke
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first compound optical microscope, using two sets of lenses
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What did microscopy do for classification?
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Changed from plant/animal system to five kingdoms (prokaryotes, protists, plants, fungi, and animals)
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What did DNA sequencing do for classification?
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Changed from 5 kingdoms to 3 domains (bacteria, archaea, eukarya)
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phylogeny
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the evolutionary history of a species or group of related species; can be represented in a phylogenetic tree
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How does morphology relate to phylogeny?
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organisms with similar morphologies are likely to be more closely related than organisms with different structures
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homology
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similarity due to shared ancestry
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analogy
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similarity due to convergent evolution
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convergent evolution
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similar environmental pressures and natural selection produce analogous adaptations in organisms from different evolutionary lineages
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homoplasies
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analogous structures that have evolved independently
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molecular clock
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the higher the number of mutations, the older the divergence time
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phylogenetic analyses with DNA sequences
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using ribosomal RNA sequence (small subunit) to determine evolutionary relationships
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Using DNA sequence to determine phylogenies
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1. align corresponding sequences to account for insertions and deletions
2. find evolutionary distance (differences out of total bases between two sequences) 3. corrected evolutionary distance (because more than one change may have occurred at any given site; done by computer) |
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Lengths on phylogenetic trees can be...
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proportional to evolutionary distance (but don't have to be)
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phylogenetic tree
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represents a hypothesis about evolutionary relationships
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branch point (node)
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represents a divergence of two species
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sister taxa
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groups that share an immediate common ancestor
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rooted tree
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includes a branch to represent the last common ancestor of all taxa in the tree
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polytomy
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a branch from which more than two groups emerge
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phylogenetic trees do show
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patterns of descent
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phylogenetic trees do not show
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when species evolved or how much genetic change occurred in a lineage
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What shouldn't be assumed with phylogenetic trees?
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that a taxon evolved from the taxon next to it
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maximum parsimony hypothesis
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tree is built assuming the fewest evolutionary events
appearances of shared derived characters is the most likely |
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maximum likelihood hypothesis
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tree is built assuming the most likely sequence of evolutionary events
given certain rules about how DNA changes over time |
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orthologous genes
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different species, common functionality and ancestry (speciation)
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paralogous genes
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same species, gene duplication and divergence
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Oparin-Haldane hypothesis
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spontaneous generation of life occurred once when atmospheric conditions found on earth were largely different from today
primitive atmosphere made of methane, carbon dioxide, ammonia, hydrogen gas, water, and solar radiation allowed reactions leading to synthesis of amino acids |
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Miller-Urey experiment
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simulated conditions thought to be present in the early earth
chemical analysis of compounds formed revealed that amino acids were present claimed that life had never been made, but only that the necessary molecules for life could form spontaneously |
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history of prokaryotes
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had the planet to themselves for about 80% of the time life existed one earth; the ancestors of all other life forms
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prokaryote
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any organism that is not a eukaryote
cells do not have a nucleus two domains: bacteria and archaea |
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oxygen revolution
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2.7 bya
most atmospheric oxygen is of biological origin source was likely bacteria similar to modern cyanobacteria |
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obligate aerobes
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cannot grow without oxygen
undergo cellular respiration |
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facultative anaerobes
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use oxygen if present, but don't have to
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obligate anaerobes
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grow exclusively by fermentation or use different electron acceptor for respiration
oxygen is poisonous |
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autotrophs
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producers of the biosphere
synthesis of organic molecules from carbon dioxide and other inorganic molecules |
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heterotrophs
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consumers of the biosphere
obtain their organic material from other organisms |
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phototrophs
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obtain energy from light
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chemotrophs
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obtain energy from chemicals (organic or inorganic)
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photoautotrophs
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plants, algae, cyanobacteria
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chemoautotrophs
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unique to certain prokarytoes
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photoheterotrophs
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unique to certain prokaryotes
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chemoheterotrophs
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animals, fungi, several prokaryotes
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microbe
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any microscopic organism
large majority of organisms are microbes small, unicellular, and free-living organism (although there are exceptions) |
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Antonie van Leeuwenhoek
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first person to describe microbes, designed one of the first microscopes
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categories of microbes
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prokaryotic microbes (bacteria, archaea)
eukaryotic microbes (most protists, some fungi) viruses (not living organisms; cannot replicate autonomously, disassemble during reproductive cycle) |
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nuclear envelope
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P-
E+ |
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membrane-enclosed organelles
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P-
E+ |
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introns
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P rare
E+ |
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chromosome
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P circular
E linear |
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Impact of prokaryotes on our world
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ubiquitous (found everywhere on earth)
transform all sorts of compounds into molecules that can be used by other organisms symbiotic relationships with plants and animals can cause diseases industrial applications (biotechnology, bioremediation) |
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thermophiles
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very hot environments
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halophiles
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highly saline environments
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psychrophiles
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very cold environments
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piezophiles
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high pressure environments
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ecological role of prokaryotes
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cycles of conversion of the biologically important elements (C, O, N, S, P)
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mutualistic relationships
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rhizobia with legumes; act as nitrogen fixing factories
vibrio colonizes light organ of squid; bacterial luciferase converts ATP hydrolysis into light, camouflaging squid |
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bacteria and humans
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more bacteria in and on our bodies than all our human cells
internal tissues are free of microbes in healthy hosts |
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largest microbial populations in humans
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gastro-intestinal tract
mouth skin |
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mutualistic relationship between bacteria and humans
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microbes gain nutrients, and benefit from a stable environment and constant temperature
host obtains nutritional benefits, colonization prevents invasion by pathogens, immune system is stimulated |
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tuberculosis
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caused by Mycobacterium tuberculosis
most common bacterial infectious disease 1/3 of the world population death rate >2mil/year affects principally the lungs |
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cholera
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caused by Vibrio cholerae
contaminated water or sea food bacteria emits cholera toxin, causing an opening of chloride channels which leads to diarrhea, dehydration, and death |
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lyme disease
|
caused by Borrelia burgdorferi
transmitted to humans by tick bite most commonly reported vector-borne disease and NA and EU Skin rash, recurring fever If untreated, arthritis and death |
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diversity of sizes in bacteria
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smallest (mycoplasma) =.3 micrometers
largest (Thiomargarita namibiensis) = 750 micrometers |
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diversity of shapes in bacteria
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sphere - coccus
rod - bacillus spiral |
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interior of bacterial cell
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no true nucleus
DNA is packaged in a fibrous structure known as the nucleoid transcription and translation are coupled |
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bacterial chromosome
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length of DNA molecule is ~1,000x the length of the cell
genome size can vary from <1 Mb to >9 Mb generally circular but a few have linear chromosomes generally only one, although some have genome distributed on more than one chromosome |
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plasmid
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extrachromosomal pieces of DNA (short and circular) that replicate independently
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plasma membrane
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phospholipid bilayer and proteins
>200 diff. kinds of proteins |
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functions of the plasma membrane
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osmotic barrier
transport of solute electron transport cell wall synthesis lipid synthesis protein secretion pohotosynthesis |
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3 types of bacteria, distinguished by cell wall
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gram-positive
gram-negative mycoplasma |
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mycoplasma
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no cell wall
plasma-like structure round morphology parasitic nature depend on host for nutrients attached to host cells, absence of cell wall facilitates interaction |
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Gram positive
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lots of peptidoglycan
violet dye (crystal violet) is trapped in peptidoglycan, red dye (safranin) is masked stains violet |
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Gram negative
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less/no peptidoglycan
violet dye washes away, red dye stains the cell |
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peptidoglycan
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modified sugar polymers (glycan) crosslinked by short peptides
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NAM
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N-acetylmuramic acid
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NAG
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N-acetylglucosamine
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lysozyme
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enzyme that hydrolyzes the glycosidic bond between NAM and NAG
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How does peptidoglycan crosslink?
|
Peptidoglycan is made of alternating chains of NAM and NAG; cross-links form between the N-acetyl groups of these monomers
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penicillin
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antibiotic that inactivates the transpeptidase the introduces crosslinks
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bacterial appendages
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capsule, flagellum, pili
not necessary and many species do not have them |
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capsule
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shield against host immune system
can be made of polysaccharide (e.g. dextran in dental plaque and meningitis) or a polymer of amino acids (e.g. poly-g-glutamate in anthrax |
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flagellum
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confer directional movement
rotate (like propellers) fitted with a motor structurally very different from eukaryotic flagella |
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pili
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fimbriae; hair-like appendages
attachment to host membranes, transfer of molecules (proteins and/or nucleic acids, specifically), twitching motility |
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taxis
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movement toward or away from a stimulus
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4 parts of the bacterial motor
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filament
hook basal body motor |
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filament
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long and hollow, composed of flagellin
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hook
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short and curved
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basal body
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4 rings for gram-, 2 rings for gram+
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motor
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driven by proton motive force
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twitching motility
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grappling hook model, 3 steps:
1. pilus fiber extends 2. fiber binds to substrates 3. fiber retracts |
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growth and division of bacteria
|
growth depends on nutrient availability
divide by binary fission (division at midcell) number of cells (N) after n generations: N=(2^n)*Ni N doubles after each generation |
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endospore formation / sporulation (bacteria)
|
adaptation to nutrient limitation
endospore is formed within a mother cell only some bacterial species can form endospores |
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what is the basis for cellular differentiation (particularly in endospore formation)?
|
asymmetric division
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What triggers sporulation?
|
starvation (addition of nutrients triggers germination)
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spore structure
|
spore is a dormant cell resistant to chemicals, enzymes, heat, and UV radiation
protective layers include the cortex (cell wall structure) and multi-layer coat (>70 proteins) |
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Robert Koch
|
worked on Anthrax, Tuberculosis, and Cholera
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Koch's Postulates
|
definition of a microbial pathogen
1. organism should be present in all cases of disease and absent from healthy animals 2. organism should be grown in pure culture 3. cells from pure culture should cause disease in healthy animal 4. organism should be reisolated and shown to be the same as the original |
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anthrax
|
spore is the delivery vehicle, the vegetative cell is causing the disease (toxins are produced by vegetative cells)
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Louis Pasteur
|
worked on chirality, alcoholic fermentation, disproving spontaneous generation, pasteurization, immunization method, and created vaccines for anthrax and rabies
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Pasteur's Experiment
|
1. Nonsterile liquid poured into flask
2. Neck of flask drawn out in flame 3. Liquid sterilized by heating 4. Liquid cooled slowly while dust and microorganisms are trapped in the bend; liquid remains sterile indefinitely 5. If the flask is tipped so microorganism-laden dust contacts the sterile liquid, then the microorganisms grow in the liquid after a short time |
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Multicellularity in bacteria
|
endospore formation
heterocyst formation in cyanobacteria biofilm formation (examples of cellular differentiation and/or communal behavior) |
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cyanobacteria
|
photosynthetic bacteria
oxygen interferes with nitrogen fixation process because nitrogenase is inactivated by oxygen |
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nitrogenase
|
converts atmospheric nitrogen to ammonium
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Anabaena
|
a colonial cyanobacterium with specialized cell types (photosynthetic cells and heterocysts)
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photosynthetic cells in Anabaena
|
vegetative cells that perform photosynthesis
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heterocysts in Anabaena
|
cells responsible for fixation of atmospheric nitrogen; separate from oxygen-producing photosynthesis cells
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|
metabolic cooperation in bacteria
|
heterocysts and vegetative cells exchange metabolites
heterocysts provide nitrogen source vegetative cells provide carbon source |
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|
biofilm
|
matrix-encased microbial community
formed at interfaces (solid-air, solid-liquid, air-liquid) most bacteria can form biofilms |
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biofilm formation
|
transition from planktonic (free-living cells) to sessile (surface-attached) cells
transition from loner to community-based existence 1. attachment 2. colonization 3. growth (matrix formation, with fluid filled channels) 4. detachment |
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|
benefits of biofilm formation
|
1. protection - resistance to physical forces and phagocytosis
2. colonization of a favorable niche 3. communal behavior - division of the metabolic burden, gene transfer is favored |
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Archaea
|
first were categorized as extremophiles
cell membranes differ from bacterial membranes in that they have a pseudo-petidoglycan known as pseudomurein that formes branched chains (isoprenoid), allowing for more stability (resistant to high temperature, high salt and low pH) |
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|
peptidoglycan in cell wall
|
B most
A no/pseudo |
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sensitivity to antibiotics
|
B yes
A no |
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|
membrane lipids
|
B unbranched hydrocarbons
A branched hydrocarbons (isoprenoid) |
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|
RNA polymerase
|
B one kind
A several kinds |
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|
Ernest Haeckel
|
introduced the terms protists and phylogeny
|
|
|
Single-celled eukaryotes appeared 1 (billion/million/hundred thousand) years after the appearance of atmospheric oxygen
|
1 billion years
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endosymbiosis
|
proposes that mitochondria and plastids were formerly small prokaryotes living within larger host cells
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endosymbiont
|
a cell that lives within a host cell
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symbiosis
|
ecological relationship between organisms of different species
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mutualism
|
both organisms benefit
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commensalism
|
one organism benefits, the other is unaffected
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parasitism
|
one organism benefits at the expense of the host
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host
|
larger organism
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symbiont
|
smaller organism
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endosymbiosis and the origin of mitochondria
|
ancestral prokaryote evolves a nucleus and engulfs an aerobic heterotrophic prokaryote; the aerobic heterotrophic prokaryote became a mitochondrian
|
|
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endosymbosis and the origin of plastids
|
after ingesting an aerobic heterotrophic prokaryote (mitochondrion), the ancestral eukaryote engulfed a photosynthetic prokaryote (cyanobacterium), which became a plastid
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|
plastid
|
chloroplasts and related organelles, usually photosynthetic
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|
protist
|
no longer constitute a kingdom; they are distributed in five supergroups of eukaryotes
def: a eukaryote that is neither a fungus, a plant, nor an animal |
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|
characteristics of protists
|
mostly unicellular, mostly microscopic, mostly aquatic, nutritionally diverse
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algae
|
photosynthetic protists
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protozoa
|
ingestive protists
|
|
|
pigments
|
substances that absorb visible light
|
|
|
different pigments absorb (similar/different) wavelengths
|
different wavelengths
|
|
|
wavelengths that are not absorbed are...
|
reflected or transmitted
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|
|
chlorophyll
|
chlorophyll alpha is the main photosynthetic pigment
|
|
|
accessory pigments
|
chlorophyll b and d
phycoerythrin (red algae) phycocyanin (cyanobacteria) carotenoids |
|
|
What is the purpose of accessory pigments?
|
broaden the spectrum used for photosynthesis
|
|
|
structure of chlorophyll
|
porphyrin ring with a hydrocarbon tail
|
|
|
chlorophyll d
|
absorbs far red light
|
|
|
porphyrin ring
|
light-absorbing center
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|
|
hydrocarbon tail
|
interacts with hydrophobic regions of proteins inside thylakoid membranes of chloroplasts
|
|
|
excitation of chlorophyll by light
|
photon strikes chlorophyll molecule, exciting an electron; as the electron falls down to ground state, heat and photons are given off
|
|
|
evolution of green and red algae
|
heterotrophic eukaryote with mitochondria engulfed a cyanobacterium (primary endosymbiosis); descended to red algae and green algae
|
|
|
pigment in red algae
|
phycoerythrin
|
|
|
green algae pigment
|
chlorophyll a and b
|
|
|
rhodophyta
|
red algae
phycoerythrin can live at great depths mostly multicellular no flagellum filamentous "leafy" form "rhodon" = rose porphyra = nori |
|
|
phycoerythrin
|
absorbs blue light, reflects red light
|
|
|
cyanidioschyzon merolae
|
unicellular red algae
small one plastid and one mitochondrion first complete algal genome calvin cycle enzymes are identical in plants additional evidence that primary endosymbiosis occurred before the separation of the red and green algae lineages |
|
|
Chlorophyta
|
green pigment (chlorophyll a and b)
plant-like chloroplast complex life cycles (sexual and asexual reproductive stages) aquatic |
|
|
Volvox
|
colonial chlorophytes
hollow ball 100-1000 bi-flagellated cells |
|
|
Caulerpa
|
fiiamentous chlorophytes
|
|
|
Ulva
|
leafy chlorophytes
edible |
|
|
Chlamydomonas reinhardtii
|
a unicellular green alga
bi-flagellated large genome single chloroplast model organism for study of photosynthesis great for genetic analyses (photosynthetic mutants can grow in presence of acetate) |
|
|
eukaryotic flagella
|
ring of microtubules (tubulin)
9 + 2 microtubule acts like a whip |
|
|
prokaryotic flagella
|
flagellin
propeller motion |
|
|
endosymbiosis with green alga symbiont
|
the nucleus of the endosymbiont is lost; many genes are transferred to the host nucleus
engulfing the green alga lead to the secondary endosymbiosis that crated Euglenids |
|
|
How were Euglenids evolved?
|
secondary endosymbiosis with green alga as a symbiont
|
|
|
Euglena
|
photoautotroph capable of movement
have long flagellum (for movement) and short flagellum light detector and eyespot |
|
|
What are the eyespot and light detector in Euglena for?
|
directed movement toward light
|
|
|
What happens to Euglena when sunlight is unavailable?
|
Euglena becomes heterotrophic (mixotroph)
|
|
|
When did kinetoplastids diverge from Euglenids?
|
before secondary endosymbiosis
|
|
|
Euglenozoans
|
flagellated
flagella contain a crystalline rod alongside a microtubules ring |
|
|
kinetoplastid
|
has a kinetoplast and a flagellum (composed of microtubules and crystalline rod)
|
|
|
kinetoplast
|
large mitochondrion that contains an organized mass of DNA
|
|
|
Trypanosoma brucei
|
causes sleeping sickness
|
|
|
Trypanosoma cruzi
|
causes Chagas' disease
|
|
|
Leishmania major
|
causes leishmaniasis
|
|
|
two-host life cycle of Trypanosoma brucei
|
host 1: tsetse fly
host 2: humans and other mammals |
|
|
Where does T. brucei live in the tsetse fly?
|
midgut and salivary gland
|
|
|
Where does T. brucei live in humans (and other mammals)?
|
bloodstream
|
|
|
T. brucei surface coat
|
monolayer of 10 million molecules of a single glycoprotein (VSG)
VSG contain a variable region only one VSG variant is produced at any one time >1,000 VSG sequences |
|
|
antigenic variation
|
a mechanism to escape the host immune response
|
|
|
How does T. brucei use antigenic variation?
|
at regular intervals, T. brucei switches to a new VSG; leads to the periodicity of the symptoms of sleeping sickness
|
|
|
endosymbiosis with red alga symbiont
|
after secondary endosymbiosis, alveolates and stramenopiles diverged; in some cases, plastids lost the ability to perform photosynthesis
|
|
|
alveolates
|
all have plastids resulting from endosymbiosis (but not all are photosynthetic
each group characterized by the type of motility alveoli |
|
|
alveoli
|
membrane-bounded sacs
|
|
|
Dinoflagellate
|
alveolates with flagella located in perpendicular grooves
spin as they move "dinos" = rotation important component of the phytoplankton carotenoid pigment in plastid (red tide) have cellulose armor |
|
|
phytoplankton
|
aquatic photosynthetic microbes
|
|
|
apicomplexa
|
alveolates that are animal parasites
have apex and apicoplast |
|
|
apex
|
specialized structure for penetration of host cells
|
|
|
apicoplast
|
non-photosynthetic plastid
|
|
|
Plasmodium falciparum
|
causes malaria; enters red blood cell
|
|
|
two-host life cycle of Plasmodium
|
sexual stage (combination of gametes into zygote) takes place in mosquito, cell cycle takes place in humans
|
|
|
malaria
|
2.7 mio deaths per year
no vaccine resistance to drugs increasing (parasite and vector) |
|
|
methods of vector control of malaria
|
insecticide treated bed nets (ITNs)
pesticides |
|
|
Ciliate
|
alveolate that uses cilia to move and feed
has a micronucleus, macronucleus, and plastid |
|
|
ciliate micronucleus
|
involved in the germline
silent diploid |
|
|
ciliate macronucleus
|
somatic
highly polyploid several hundreds of chromosomes |
|
|
Paramecium
|
alveolate that feeds via cilia
cilia move food (bacteria) into the cell mouth (phagocytosis) have oral groove, cell mouth, and food vacuoles (lysosomes) |
|
|
Stramenopila
|
have flagellum with numerous fine hairline projections
plastids are photosynthetic |
|
|
Diatom
|
stramenopile unicellular alga
important component of the phytoplankton silica shells (glass-like wall) with complex geometric patterns (protection against crushing jaws of predators) large size range |
|
|
How much global carbon fixation is photosynthesis by diatoms responsible for?
|
20%
|
|
|
Thalassiosira pseudonana
|
genome released in 2004
35 MB 24 chromosomes 11,500 genes novel genes for silicic acid transport and formation of silica-based cell walls |
|
|
Chrysophyta
|
golden algae; stramenopiles
"chryso" = gold yellow and brown pigments (carotenoids) motile - free-swimming, bi-flagellated all are photosynthetic, some mixotrophs mostly unicellular, some colonial |
|
|
mixotrophs
|
facultative heterotrophs
|
|
|
Phaeophyta
|
brown algae; stramenopile
"phaeo" = brown macroscopic (largest known algae are brown algae) non-motile multicellular (specialized tissue and organs) alternation of generations |
|
|
alternation of generations
|
alternation of haploid and diploid forms
|
|
|
specialized anatomical features of brown algae
|
blade, stipe, holdfast
analagous to roots, stems and leaves in plants |
|
|
homoplasy between brown algae and roots
|
holdfast
|
|
|
homoplasy between brown algae and stems
|
stipe
|
|
|
homoplasy between brown algae and leaves
|
blade
|
|
|
Amoebozoa are a sister group to...
|
the Animals and Fungi
|
|
|
Dictyostelium
|
a social amoebozoa
a model organism for the evolution of multicellularity inhabits forest soil, feed on bacteria solitary cells aggregate and differentiate upon starvation |
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prokaryotic microbes
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bacteria, archaea
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eukaryotic microbes
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protists, some fungi
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viruses
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cannot replicate autonomously, disassemble during their reproductive cycle (not a living organism)
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1918 flu epidemic
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50 million people died, 500 million people were infected
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epidemiology
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study of disease in populations (occurrence, distribution, and control)
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epidemic
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occurrence of a disease in unusually high numbers in a localized population
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pandemic
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a worldwide epidemic
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endemic
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disease is constantly present (usually in low numbers)
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John Snow
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founding father of epidemiology
identified the source of a cholera epidemic in London to a public water pump in 1854 |
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water treatment
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critical to public health
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host/pathogen balance
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co-evolution of the pathogen and its host until steady-state
it is advantageous to a pathogen not to kill its host |
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chronic infection
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long term infection
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Most dangerous pathogens to humans
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emerging pathogens and pathogens that are not dependent on human host for survival
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why are emerging pathogens dangerous?
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resistance has not yet developed
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why are pathogens not dependent on the human host dangerous?
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other hosts can carry the pathogen
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Martinus Beijerinck
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disease of tobacco leaves is caused by "something smaller than a bacterium"
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Wendell Stanley
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isolation of the TMV as "a nucleoprotein particle"
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How did they know TMV was a virus?
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from the juice of tobacco leaves infected with tobacco mosaic disease, a filtrate free of bacteria retains ability to cause disease in plants
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structure of viruses
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nucleic acid enclosed in a protein coat, sometimes a membranous envelope
viruses are not cells |
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viral genomes
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may consist of double or single stranded DNA or double or single stranded RNA
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viral genome size
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smallest viral genomes contain only four genes (Rous Sarcoma Virus)
largest viral genomes contain about a thousand genes (mimivirus) |
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oncogenic viruses
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cause tumors
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capsid
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the protein shell that encloses the viral genome
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capsid shapes
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rod-shaped (helical) and made of a single type of protein
icosahedral |
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icosahedral viruses
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human papilloma virus (HPV)
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HPV
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causes cervical cancer
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membranous envelopes
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viral envelope that surrounds the capsid
derived from the host cell's membrane (display a combination of viral and host cell molecules) |
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what are the advantages of host cell-derived membranous envelopes on viruses?
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fools the immune system, allowing the virus to remain undetected
facilitates the fusion of the virus with the host cell membrane |
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structure of viral membranous envelopes
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surround capsid
covered in glycoproteins (some derived from host cell, some viral) |
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obligate intracellular parasites
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can reproduce only within a host cell (viruses)
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what do viruses do during their reproductive cycle?
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disassemble
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host range
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a limited number of host cells that it can infect
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the gist of a viral reproductive cycle
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virus enters cell and disassembles; viral proteins are expressed using cellular machinery; viral proteins self-assemble into new viruses and exit the cell
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general features of viral reproductive cycles
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hi-jacking of the host cell
after viral genome enters, the cell begins to manufacture viral proteins virus uses host's enzymes, ribosomes, tRNAs, amino acids, ATP, and other molecules viral nucleic acid molecules and proteins spontaneously self-assemble into new viruses |
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retroviruses
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class of RNA viruses that use reverse transcriptase to copy their RNA genome into DNA
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reverse transcription
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uses RNA to synthesize DNA
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HIV
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retrovirus that causes AIDS
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HIV reproductive cycle
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virus enters cell; viral RNA is transcribed to DNA through reverse transcription; viral DNA integrated into cellular chromosomal DNA; RNA is created from new DNA and viral parts self-assemble; glycoproteins gather on surface as cell prepares to pinch off
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AZT
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azidothymine, nucleoside analog drug used to combat HIV; should be taken in combination with other drugs to avoid development of resistant viruses
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how do nucleoside analogs stop retroviruses?
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interrupts reverse transcription by terminating RNA dependent DNA polymerization (replaces normal base and ceases function)
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vaccines
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harmless derivatives of pathogenic microbes that stimulate the immune system to mount defenses against the actual pathogen
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Smallpox
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caused by the dsDNA virus Variola major
highly contagious causes severe skin lesions invades and damages internal organs as well 1979 - declared eradicated by WHO strains still conserved in 2 labs in USA and Russia |
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Edward Jenner
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noted that milkmaids usually don't get smallpox
immune to disease because they previously contracted cowpox 1796 - inoculates material from cowpox blisters to a young boy, later injected virus but no infection developed |
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modern smallpox vaccine uses...
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vaccinia virus
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Louis Pasteur's vaccine work
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anthrax vaccine, first patient cured of rabies by vaccination
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attenuation
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preparation of a vaccine
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attenuation of rabies vaccine
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Pasteur took spinal cord material from rabid rabbits and inoculated it into dogs, who were then unaffected by rabies
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Joseph Meister
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bitten by dogs, inoculated by Pasteur, no rabies developed
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viroids
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circular RNA molecules that infect plants and disrupt their growth
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prions
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slow-acting virtually indestructible infectious particles that cause brain diseases in mammals (scrapie, mad cow disease, Creutzfeldt-Jakob disease)
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how do prions propagate?
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converting normal proteins into the prion version
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bacteriophages
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aka phages
viruses that infect bacteria |
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importance of phages in molecular biology
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helped prove that DNA is the genetic material (Hershey and Chase)
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structure of bacteriophages
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most complex capsids of all viruses
have an elongated capsid head enclosing their DNA protein tail piece attaches the phage to the host and injects the phage DNA inside |
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lytic cycle
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a phage reproductive cycle that culminates in the death of the host cell
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lysogenic cycle
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replicates the phage genome without destroying the host
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basic steps of the lytic cycle
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attachment
injection of phage DNA and degredation of host DNA synthesis of viral genomes and proteins assembly cell lysis - release of phage particles |
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How does the lytic cycle work (one sentence)?
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produces new phages and digests the host's cell wall, releasing the progeny virus
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virulent phage
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a phage that reproduces only by the lytic cycle
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What defenses do bacteria have against phages
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restriction enzymes
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restriction enzymes
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recognize and cut up certain phage DNA
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lysogenic cycle (summary)
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viral DNA molecule is incorporated into the host cell's chromosome; every time the host divides, it copies the phage DNA and passes the copies to daughter cells
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prophage
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integrated viral DNA
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what triggers the switch to lytic mode from the lysogenic mode?
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an environmental signal; virus genome exits the bacterial chromosome and switches to the lytic cycle
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temperate phages
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phages that use both the lytic and lysogenic cycles
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how do bacterial genomes evolve?
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vertical gene transfer and horizontal gene transfer
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vertical gene transfer
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from mother to progeny cells
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horizontal gene transfer
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from one cell to another; can potentially happen between distantly related species
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what are important factors in dictating bacterial evolution?
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mutation rates
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modes of HGT
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conjugation, transduction, transformation
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conjugation
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formation of a sex pilus through which proteins and DNA are sent; requires physical contact
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F
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a plasmid that carries genes that direct the synthesis of the pilus
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F+
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donors (male)
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F-
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recipients (female)
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transduction
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chromosome from donor is broken up, pieces of DNA from donor incorporated into phage head, DNA from donor is injected into recipient, recombination occurs
(genes passed by virus) |
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transformation
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donor cell lyses, free DNA fragments are taken up by new bacterium (recipient) which then recombines
some bacteria are naturally competent some bacteria are rendered competent artificially (through ions, heat shock, electroporation) |
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How does HGT relate to phylogeny?
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HGT confuses phylogeny, though it increases bacterial diversity
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immune system
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recognizes and responds to pathogens
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pathogens
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agents that cause disease (usually microbes or toxins)
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two types of immune responses
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innate immunity, adaptive immunity
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innate immunity
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present before any exposure to pathogens
nonspecific responses recognition of traits common to groups of pathogens (requires only a small set of receptors) first, rapid response to infections |
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innate immunity is found in...
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all plants and animals
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What kinds of innate immunity are found in all animals?
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barrier defenses
chemical defenses cellular defenses |
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what kinds of innate immunity are unique to vertebrates?
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inflammatory response
natural killer cells interferons (inhibition of viral infections) |
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barrier defenses in humans
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body fluids (saliva, tears, mucus)
skin mucous membranes of the respiratory, urinary, and reproductive tracts low pH of skin and the digestive system |
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lysozyme in tears
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dissolves cell walls
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cellular innate defenses rely on...
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PAMP recognition
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PAMP
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pathogen-associated molecular patterns
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structures typically found in bacteria
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peptidoglycan
LPS (lipopolysaccharide) flagellum |
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PRMs
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pattern recognition molecules
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TLRs
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toll-like receptors; usually found on phagocytes
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cytokines
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signaling molecules of the immune response
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how do TLRs work?
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binding of pathogenic particle to TLR triggers cytokine production
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local response to infection
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histamine (produced by mast cells) triggers dilation of blood vessels; permeability of the vessel increases, allowing immune cells to leave and fight infection
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types of phagocytic cells
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macrophages
neutrophils |
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macrophages
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found throughout the body (organs and tissues)
long-lived cells arrive at site of microbes more slowly than neutrophils clear up microbial debris and remaining microbes become activated by cytokines, proteins made in response to microbial invasion make cytokines that attract and activate neutrophils, thus contributing to acute inflammation help initiate specific innate immune responses (cell-mediated immunity) |
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neutrophils
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circulate in the blood, are attracted by signals from infected tissues
short lived cells (live a few weeks) loaded with large lysosomal granules that contain hydrolytic enzymes that can destroy many bacteria and oxidative enzymes that make toxic products, especially hypochlorite (bleach) recruited to the site of the microbes by several chemotaxins, some derived from complement and others products of bacterial metabolism require opsonins to be effective in killing microbes |
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phagocytosis
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pseudopods begin to engulf microbe
encapsulated in phagosome fusion of phagocytic vesicle with a lysosome lysosome combines with phagosome to make phagolysosomal vesicle microbe is killed and digested by phagolysosomal vesicle |
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phagolysosome
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contains lysozyme, proteases, phosphateases, nucleases, lipases, oxidases
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killing of microbes within the phagolysosome involves the use of...
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toxic oxygen species (hydrogen peroxide, nitric oxide); requires increased oxygen uptake (respiratory burst)
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symptoms of inflammatory response
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pain and swelling
increased blood flow outpouring of fluids pus heat (fever) |
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erythema
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reddening, caused by increased blood flow
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edema
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swelling, caused by outpouring of floods
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pus
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fluid rich in white blood cells, dead pathogens, cell debris
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inflammatory response
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can be local or systemic
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systemic
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throughout the body
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fever
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a systemic inflammatory response, triggered by pyrogens
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pyrogens
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molecules released by macrophages, cause elevation in body temperature
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septic shock
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life-threatening condition
caused by an overwhelming inflammatory response |
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natural killer cells
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differentiate and mature in the lymphatic system (lymphocyte)
not phagocytic release chemicals leading to cell death inhibit the spread of virally infected or cancerous cells |
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human lymphatic system
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network that distributes a fluid called lymph
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complement system
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group of ~30 proteins in blood plasma
helps trigger inflammation facilitates phagocytosis causes cell lysis |
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aspects of the complement system
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early pathway is innate
late pathway is adaptive, requires antibody production proteolytic cascade generates ~30 proteins |
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MACs
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membrane attack complexes
complement peptides promote microbial cell lysis by formation of holes in membranes |
