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56 Cards in this Set

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First evidence of oxygenic photosynthesis? Photosynthetic prokaryote?
First undisputed fossil of living organisms were cyanobacteria stromatolites (colonies of bacteria) formed ~2.7 bya (Archaean Eon).
When did oxygen levels significantly rose?
~2.4-2.2 bya. Significant rise in oxygen levels is a factor for development of eukaryote.
How have photosynthetic prokaryotes contribute to change in oxygen levels and lead to evolution of new life forms?
Cyanobacteria led to increase in O2, which led to development of eukaryotes. O2 levels remained constant until algae appeared. Algae contribute to more than half of O2 today, enough for the evolution of land plants and mammals.
What are the three domains of life?
Bacteria, Archaea, and Eukarya
Differences between the three domains of life pertaining to presence/absence of nuclear envelop, circular DNA, and DNA with histones.
Nuclear envelop: only Eukarya
Circular chromosome: Bacteria and Archaea
DNA w/histones: Archaea and Eukarya
Is prokaryotes a monophyletic group?
No because organisms in the three domains of life have a common ancestor but Eukarya are not prokaryotes, while Bacteria and Archaea are.
How do prokaryotes and eukaryotes differ in structure?
Prokaryotes are smaller, have a nucleoid and not a membrane bound nucleus, and do not have organelles like eukaryotes.
How do we identify never been seen prokaryote species?
Direct sequencing:
1) Collect sample and purify DNA.
2) Amplify DNA using PCR.
3) Purify amplified genes and insert into plasmid.
4) Insert plasmid into cells and culture different species.
5) Purify genes from plasmid and sequence them.
6) Compare unknown with known sequences.
How does Bacteria and Archaea affect our lives?
Most bacteria are good; only a small % are pathogenic. Photosynthetic prokaryotes were responsible for oxygen atmosphere. They cycle nutrients in terrestrial and aquatic environments. Some species can clean up pollution.
Life on Earth after Snowball Earth thanks to..
Archaea's extremophiles. They were able to survive the extremely cold weather and when volcanic eruptions occurred, CO2 levels increased, and snow melted, extremophiles jumpstarted life.
Archaea
Ancient prokaryotes. Extremophiles such as methanogens, thermophiles, halophiles, and sulfate reducers.
Cell Wall in Bacteria and Archaea
Bacteria: cell walls made of peptidoglycans (amino acids and sugars). Two types: GRAM POSITIVE stains purple (90% peptidoglycan) and GRAM NEGATIVE stains pink (small peptidoglycan layer between outer layer of lipopolysaccharide and plasma membrane).
Archaea: different peptidoglycan or just proteins.
Differences between Archaea and Bacteria
Archaea's membranes have branched chains of fatty acids but Bacteria's membranes have unbranched chains of fatty acids. They both have no nuclear membranes and have circular DNA. Bacteria has no histones but Archaea's DNA coil around histones.
Metabolic diversity of prokaryotes
All organisms need chemical energy (ATP).
All organisms need carbon in form they can use to make fatty acids, proteins, DNA, RNA, etc.
Bacteria and Archaea DIVERSE in ways they acquire both.
Autotrophs
Absorbs organic compounds and make their own food for ATP. Photoautotrophs (use light), chemoorganoautotrophs (use organic molecules), and chemolitho[auto]trophs (use inorganic molecules).
Heterotrophs
Use molecules produced by other organisms for energy. Photoheterotrophs, chemoorganoheterotrophs, and chemolithotrophic heterotrophs.
Photosynthesis and phylogeny. Do photosynthetic organisms form a monophyletic group?
We would expect that photosynthetic organisms to form a monophyletic group but they're paraphyletic. LATERAL GENE TRANSFER can explain this phenomenon. Photosynthetic gene transferred via TRANSFORMATION and TRANSDUCTION.
Lateral gene transfer: transformation and transduction
Transformation: taking up foreign pieces of DNA from environment.
Transduction: viral vector transfers DNA from one bacterium to another.
Chemolitho[auto]troph
Use inorganic molecules with high potential energy.
Ex. Sulfur-oxidizing archaea that live in Yellowstone geyser and Deep Sea.
Ex. Nitrifying bacteria
Chemolithotroph: Rhizobium
Nitrogen-fixing bacteria in root nodules with symbiotic relationship with plant they live on.
Oxygen and Prokaryotes: Three types
Obligate aerobes: need O2 to live (majority of prokaryotes)
Facultative anaerobes: Use O2 if present but can grow by fermentation in anaerobic environment.
Obligate anaerobes: poisoned by oxygen by not extinct. Ex. Archaea: methanogens (use organic compounds for respiration; by-product is methane).
Who are eukaryotes?
Protists (paraphyletic), plants, fungi, and animals.
First eukaryotic cell fossils?
About 2.1 billion years ago.
Mitochondira
Eukaryotic organelle with double membrane with the inner membrane folded, own circular DNA, is 1 um similar to the size of a bacteria, and it divides by fission.
Chloroplast
Organelle in photosynthetic eukaryotes with a double membrane, an inner membrane system with grana, has its own circular DNA, is ~1 um similar to a bacteria's size, and it divides by fission.
Evolution of the nuclear membrane in eukaryotes?
Hypothesis: Eukaryotic cell's endomembrane system (ER) and nucleus evolved from inward folds of plasma membrane of an ancestral prokaryotic cell.
Endosymbiosis Theory
Endosymbiosis: when one species lives inside another species. Proposes that the mitochondria was a bacterium engulfed by a eukaryote about 2 mya. The eukaryote supplies the bacterium with protection and organic compounds and bacterium supplies eukaryote with ATP. Applies to chloroplasts also.
Selective advantage of endosymbiosis?
ATP synthesis more efficient because bacterium engulfed is aerobic and goes through the electron transport chain and produces a high ATP yield, whereas the anaerobic eukaryote goes through fermentation and and produces a low ATP yield.
What data support the Endosymbiosis Theory?
Size of mitochondria and chloroplasts are similar to bacteria's. Both organelles have their own circular DNA like circular DNA in prokaryotes and divide by itself via fission. Both organelles have double membranes, consistent with the engulfing mechanism. Genetic sequencing show that mitochondrial DNA is more similar to a bacteria than eukaryote's DNA and that chloroplasts are closely related to cyanobacteria.
Serial/Secondary Endosymbiosis Theory
Photosynthesis in protists due to engulfing of cyanobacteria, then spread among lineages by serial endosymbiosis, which proposes that some photosynthetic protists obtain chloroplasts by engulfing other photosynthetic protists! Meaning chloroplasts with FOUR membranes.
Diverse Traits of Protists
Vary in types of organelles contained, uni- or multi-cellular (multicellularity evolved independently several times in protists), microscopic to large, cell wall, other covering or no covering, produce asexually or sexually, parasitic and photosynthesis.
How do protists reproduce?
Most undergo asexual reproduction via mitosis (diploid mother produces 2 diploid daughter cells). Sexual reproduction evolved in protists (meiosis: diploid mother produces 4 haploid cells). ALTERATION of GENERATION in those that have 2N and N phases of life cycle.
Summary: Key morphological changes in protist diversification
1. Nuclear envelop from membrane inward folding.
2. Multicellularity evolved multiple times.
3. Structures that function in cell support/protection.
4. Mitochondria and chloroplasts from endosymbiosis.
Why do biologists study protists?
1. Impacts on human health and welfare (e.g. Irish potato famine, Malaria, harmful algal blooms).
2. Ecological importance (primary producers/food chain/global warming).
Protists' impact on human health and welfare: Irish potato famine (1845-47)
Caused by Phytophthora infestans, a water mould that develop on leaves in warm, moist weather. Infected tubers. Up to 2 million died and 2 million migrated out of 9-10 million population.
Protist' impact on human health and welfare: Malaria
Caused by Plasmodium, a unicellular protist with a complex life cycle. Apicomplexa "apex complex": apex of cell with complex organelles used to get into host. Transferred to humans by mosquitoes.
Protists' impact on human health and welfare: harmful algal bloom
Occurs when toxin-producing protists reach high densities in an area. Ex. algal blooms of dinoflagellates (red tides) can poison fish. Dinoflagellates-symbiosis relationship with coral polyp cells (chloroplasts have 4 membranes).
Ecological importance of protists
1. Protists are most abundant primary producers.
Ex. Diatoms are primary producers of the ocean.
2. Protists produce organic molecules that represent ~50% of CO2 fixed on Earth.
3. Make up base of aquatic food chain. Ex. phytoplankton (photosynthetic)
4. Carbon sinks produced by protists (sedimentary rocks & petroleum) help reduce C --> global warming.
Photosynthesis and Protists Groups Distinguished by Pigment
Most are photosynthetic. Major groups of protists distinguished by pigments they contained.
Brown algae: Chlorophyll a, c, and xanthins.
Red algae: Chlorophyll a and phycoerythrins
Green algae: Chlorophyll a and b
What are fungi?
Most = multicellular, sexual/asexual, heterotrophs (saprobic, parasitic, mutualistic), non-motile with filaments extending from cell walls made out of chitin, cells usually divided by septa with pores that allow mitochondria, ribosomes, and nuclei to pass, and have mycelium (networks of threadlike structures--hyphae).
Fungi Evolutionary past: When did it radiate from common ancestor with animal lineage? Date of fossil of microscopic fungal spores and threads in sediments?
Radiated from common ancestor with animal lineage ~1 bya. Fossil of fungal spores and threads ~ 460 mya, showing that fungi and land plants moved onto land around same time (supports theory that fungi aided plants in moving onto land).
Three types of fungal heterotrophs
1. Saprobic: absorb non-living organic material (e.g. dead organisms).
2. Parasitic: use living host cells to absorb nutrients.
3. Mutualistic: absorb nutrients from host and gives hosts something in return.
Fungal haustoria
Some parasitic and mutualistic fungi have this structure which allows them to penetrate plant host cells but stay outside plant cell's plasma membrane.
Fungi's adaptations for absorption
Fungi can only absorb small organic molecules from environment so they have structures that help them.
1) Have hydrolytic enzymes that break down complex molecules. 2) Rapid-growing mycelium increases SA. 3) Thin, hyphal tubes provide high SA:V.
Four main lineages of Fungi
1. Chytridiomycota (water molds)
2. Zygomycota (bread molds)
3. Basidiomycota (mushrooms, puffballs)
4. Ascomycota (Penicillium, yeasts)
Four ways fungi can perform sexual reproduction
1) Chytrids: swimming gametes and spores.
2) Zygomycetes: zygote when diff. haploid hyphae meet.
3) Basidiomycetes: spores in pedestal-like structures (basidia) at end of hyphae.
4. Ascomycetes: spores with specialized cells called asci.
Fungi: Chytridiomycetes "kid-rids" (Water mold)
ONLY fungi with flagella and live in water. World-wide decline of amphibians: B.dendrobatidis attacks skin of adults, teeth and jaws of tadpoles-->suffocation, poison or dehydration.
Fungi: Zygomycota (e.g. bread mold)
Most are MYCORRHIZAL: symbiotic relationship between mycelium and plant roots (80% angiosperm, 100% gymnosperms). Ectotrophic (EMF): infect trees but don't penetrate roots. Endotrophic/Vesicular arbuscular (AMF): infect flowering plants and penetrate roots. Some PREDATORY (ex. Arthobotrys --> roundworms).
Fungi: Ascomycetes "sac fungi" (e.g. yeast, Penicillium)
Most are unicellular. Some MYCORRHIZAL e.g. edible morel that's considered as delicacy. Some PATHOGENIC e.g. Chestnut blights that enter through cracks in bark, grow through trees' vascular tissues & slowly kills trees. Some TOXIC e.g. Claviceps purpurea that kills rye and causes, in animals, gangrenous pain in limbs, hallucinations (acid from fungus in LSD), convulsions and nausea.
Fungi: Ascomycetes: Yeast
Ex. S. cerevisiae (Brewer's yeast) which are facultative anaerobe. If grown in O2, give off CO2 and make bread rise. Ferment sugars in fruits: wine. Ferment sugars in grain: beer.
Fungi: Ascomycetes: Penicillium
Brush like structure produces spores. Most produce toxins, which is known as penicillin. Flavors Brie, Camembart, and other cheeses.
Fungi: Basidiomycetes (e.g. mushrooms and puffballs)
Some are EMF. Some are PARASITIC (smuts and rusts). Many for food and many produce toxins that are used for drugs.
Mollusca (Sea slugs, squid, snails, bivalves)
Triploblast and protostome. Soft bodies with a "head" region and a "foot" region. Often their bodies covered by hard calcium carbonate shell (slugs, squids, & octopuses have reduced or lost shell) and a mantle. Class Bivalvia includes clams and oysters.
Annelida (segmented worms e.g. earthworms, leeches and polychaetes)
Triploblast and protostome. Polychaetes "many bristles": clam worms, sea mice, fire worms; most have planktonic larvae. Earthworms and leeches have no fee larval stage.
Nematoda (roundworms)
Triploblast and protostome. Unsegmented and has psuedocoelom. Reproduce sexually. Nutrient cyclers, plant parasites (hookworms Trichinella, etc.), decomposers.
Platyhelminthes (flatworms)
1. Free-living Turbellaria (e.g. planaria)
2. Parasitic Trematoda/flukes (e.g. human lung fluke)
3. Parasitic Cestoda/tapeworms: intestinal parasites in vertebrates.