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29 Cards in this Set

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  • Back
multicellular, heterotrophic eukaryotes that obtain nutrition by ingestion

--evolved from colonial flagellated protist about 700 mya
radial symmetry
identical all around a central axis (sea anemone)

--sessile animals (stationary)
bilateral symmetry
only one way to split into two equal halves--down the midline

--motile animals (mobile)
major events in animal evolution
1. distinguishes sponges from all other animals based on structural complexity. sponges, though multicellular, lack the true tissues, such as nervous tissue, that characterize more complex animals
2. split based on body symmetry
3. evolution of body cavities
4. protostomes vs. deuterostomes
body cavity
a fluid-filled space separating the digestive tract from the outer body wall
protostomes vs deuterostomes
-2 distinctively different ways the coelom is formed during embryonic development
mullusks, annelids, and arthropods
echinoderms and chordates
animals without backbones

95% of all known animal species are invertebrate4s
the sponges..sessile animals that appear so sedate to human eye that ancient greeks believed them to be plants

--body resembles sac with holes in it

--flagellated cells lining central cavity trap and engulf bacteria
jellyfish, corals, and anemones

--characterized by the presence of body tissues as well as by radial symmetry and tentacles with stinging cells
gastrovascular cavity
basic body plan of of a cnidarian is a sac with a central digestive compartment

--tentacles with cnidocytes

--polyps and medusas
one of two types of cnidarian body forms; a columnar, hydra-like body
one of two types of cnidarian body forms; an umbrella-like body form; also called a jelly
phylum platyhelminthes

1. simplest bilaterally symmetrical animals
2. digestive tract with single opening
3. some are parasites (fluke and tapeworms)
roundworms get common name from their cylindrical body, usually tapered at both ends

--important as decomposers
--90,000 species
--parasites--hookworms, pinworms, trichina worms
complete digestive tract
a digestive tube with two openings, a mouth and anus
a body cavity not completely lined by mesoderm-derived tissue
protostomes with true coelom

-soft-bodied animals but more are protected by a hard shell
3 major groups of mollusks
1. gastropods
2. bivalves
3. cephalopods
snails and slugs

protected by a single spiraled shell into which the animal can retreat when threatened
clams, oysters, mussels

have shells divided into two halves hinged together

most are sedentary, living in sand or mud in marine and freshwater environments
squids and octopuses

built for speed and agility

some have large, heavy shells, but in most the shell is small and internal (squids), or missing altogether (octopuses)
earthworms and leeches

worms with body segmentation

coelom divided into segements by septa
subdivision of the body along its length into a series of repeated segments. looks like a set of fused rings
most diverse and successful animal group

named for jointed appendages

-grabs, lobsters, spiders, scorpions, grasshoppers, moths
reasons for success of arthropods
1. segmentation and specialization
2. hard exoskeleton (chitin)
3. jointed appendages
metamorphosis of arthropods
larva, pupa, then adult
major groups of arthropods
1. arachnids (spiders, mites)
2. crustaceans (lobsters, shrimp, crabs)
3. insects (beetles, flies, bees, wasps, ants)