OXYGEN REVOLUTION Eukaryotes Evolved Anaerobic World (4.6 BYA-) No oxygen in the atmosphere; No ozone layer, UV radiation bombards earth Organic Soup Origin of Life Anaerobic Chemosynthetic and/or Heterotrophic Bacteria Anaerobic Photosynthetic Bacteria One Photosystem Aerobic Photosynthesis (Blue-green bacteria) 3.5 BYA Two Photosystems & O2 released Aerobic World (<2.5 BYA) Krebs Cycle evolved, ozone layer developed, land could be occupied Eukaryotes Evolved

OXYGEN REVOLUTION Anaerobic

There are 6 known phyla of photosynthetic bacteria widely distributed almost certainly due to horizontal gene transfer. Only the Cyanobacteria is capable of oxygenic photosynthesis. The others don’t produce O2 Science 31 March 2017

They evolved the Krebs Cycle The oxygen revolution killed most anaerobic prokaryotes. But some prokaryotes evolved a way to deal with the O2. = Oxygen atom + 2 electrons  O = O + 2 H+  H20 They evolved the Krebs Cycle

Anaerobic Aerobic Heterotrophic Nutrition Glucose (6C) Glycolysis Many anaerobic bacteria do this. 2 Pyruvic Acid (3C) Kreb’s Cycle Aerobic Some bacteria can do this

KREBS CYCLE/ ELECTON TRANSPORT H2 O is formed O2 is final e- receptor Pyruvic acid (3C) KREBS CYCLE/ ELECTON TRANSPORT H2 O is formed O2 is final e- receptor Little ATP produced CO2 released Lots of ATP formed 36 ATPs

KREBS CYCLE/ ELECTON TRANSPORT H2 O is formed O2 is final e- receptor Pyruvic acid (3C) KREBS CYCLE/ ELECTON TRANSPORT H2 O is formed O2 is final e- receptor Little ATP produced CO2 released Lots of ATP formed 36 ATPs

Electron Transport System On walls of inner membrane X Y G E N Krebs Cycle In matrix Electron Transport System On walls of inner membrane Pyruvic acid

This could only occur after the oxygen revolution

PROPOSED BACTERIA EVOLUTION ~2.5 BYA 3.5 BYA Chemosynthesis

Where Did Eukaryotes Come From? Answer: They evolved from Prokaryotes Two Hypotheses: 1) Infolding hypothesis 2) Endosymbiotic hypothesis

Evolution of the Eukaryotic Cell IInfolding hypothesis Origin of chloroplasts Origin of mitochondria

Evolution of the Eukaryotic Cell IInfolding hypothesis Notice: the mitochondria and chloroplasts enter the cell after the membrane system of the cell has become established

Evidence for Endosymbiotic Hypothesis of the origin of mitochondria & chloroplasts Similarities between bacteria & mitochondria & chloroplasts: Binary fission Size Single circular naked DNA Same sized ribosomes (small) Protein synthesis inhibited by antibiotics Enzymes for synthesis of DNA, RNA, Protein similar Electron transport system in the walls of the structure

Eukaryotes have both Archaebacteria & Eubacteria genes Archaeal genes run processes involving DNA & RNA (informational functions): replication, transcription, & translation Bacterial genes run metabolic & housekeeping chores (operational functions).

Three Domain Tree

Two Domain Tree

Evolutionary Sequence Prokaryotes

Kingdom Protista

PROTISTA The first Eukaryotes

Problems for Protista Who are the Protista? Where did they come from? How did their structures evolve? How did sex evolve? How did mitosis evolve? How did meiosis evolve?

Who are the Protista? Eukaryotic (= true nucleus) Membrane bound organelles Usually single celled Mostly asexual reproduction

POLYPHYLETIC

Who are the Protista? Three major groups 1) Animal-like Protista = Protozoa (Lack chloroplasts; classified by locomotion; heterotrophic) 2) Fungal-like Protista (Lack chloroplasts; produce spores; heterotrophic) 3) Plant-like Protista = Unicellular algae (Have chloroplasts; photosynthetic; classified by pigments)

Animal-like Protista Protozoa Four major groups 1) Flagellates (move with flagella) 2) Ciliates (move with cilia) 3) Amoebae (move with pseudopods) 4) Sporozoa (lack movement, produce spores)

Flagellates= move with flagella Zooflagellates

How are the Protozoa related to multicellular animals? Choanoflagellates

How are the Protozoa related to multicellular animals? Choanoflagellates = collar cells Sponges

How are the Protozoa related to multicellular animals? Eumetazoa Parazoa Choanoflagellates “True Animals” Sponges

Ciliates= move with cilia Must be closely related to zooflagellates

Amoebae= move with pseudopods Naked species (= without shells)

Amoebae in silicon shells Radiolarians

Amoebae in calcium carbonate shells Foraminiferans

Slime Molds Protista with Fungal-like Characteristics

Cellular Slime Mold Note: Amoebae Could Slime molds be related to amoebae?

Where Do Algae Fit In? Zooflagellates Photoflagellates Ancestral flagellates Since both protozoa & algae have flagella Protozoa Single-celled Algae Chloroplasts

Summary of Algae Relationships Ch a & c Ch a & b ancestors ancestors Phytoflagellates Dinoflagellates Euglenas Diatoms Green Algae Brown Algae Red Algae

Chlorophylls a & c algae Dinoflagellates Ch a & c Red Tides

200,000 species 2. Diatoms Ch a & c silicon shells Most of the oceans’ photosynthesis 20% of world’s photosynthesis by diatoms 200,000 species

Multicellular Algae Brown Algae Phylum Phaeophyta Ch a & c Kelp

Chlorophylls a & b algae Euglenas Ch a & b Many heterotrophs

Multicellular Algae Green Algae Phylum Chlorophyta Ch a & b

Multicellular Algae Red Algae (Phylum Rhodophyta) Ch a & phycoerythrin Reef building = Coraline algae secrete calcium carbonate

Evolutionary Sequence Prokaryotes

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