1. Where did life come from?

2. First, where did the earth come from? Everything appears to have started with the Big Bang – about 14 billion years ago. The solar system formed about 5 bya. Earth formed from an accumulation of materials orbiting the sun – about 4.5 bya.

3. And life??? Conditions were not suitable for life – –Hot –Much radiation –No organic molecules Conditions had to change Organic molecules had to be synthesized How???

4. Evolution of Life Early Earth was hot; atmosphere contained poisonous gases. Earth cooled and oceans condensed. Simple organic molecules may have formed in the oceans.. Small sequences of RNA may have formed and replicated. First prokaryotes may have formed when RNA or DNA was enclosed in microspheres. Later prokaryotes were photosynthetic and produced oxygen. An oxygenated atmosphere capped by the ozone layer protected Earth. First eukaryotes may have been communities of prokaryotes. Multicellular eukaryotes evolved. Sexual reproduction increased genetic variability, hastening evolution.

5. Building Life The early earth had no organic compounds: Where did these come from? 1953 – Miller and Urey hypothesized that conditions could produce chemical reactions to synthesize organic compounds from inorganic. –The did the experiment and it worked.

6. Mixture of gases simulating atmospheres of early Earth Spark simulating lightning storms Condensation chamber Cold water cools chamber, causing droplets to form Water vapor Liquid containing amino acids and other organic compounds Miller and Urey Experiment: Simulated early earth conditions to model formation of organic molecules.

7. Now that we have the building materials, what makes a cell? A membrane - can build this in a dish! Nucleic acids: DNA (originally RNA?) – can assemble these in a dish. Protein synthesis machinery – A little more complicated. Enzymes for energy transfer – can make these work in a dish - sort of - and definitely work in a proteinoid microsphere.

8. Nutrition? Simplest organisms just absorb organic compounds –Heterotroph hypothesis – Oparin Photosynthesis – big advance! –Byproduct (oxygen) changed everything. Availability of free oxygen permitted more efficient release of energy from food. –Aerobic respiration

9. Endosymbiotic Theory- making a eukaryote from prokaryotes Aerobic bacteria Ancient Prokaryotes Ancient Anaerobic Prokaryote Primitive Aerobic Eukaryote Primitive Photosynthetic Eukaryote Chloroplast Photosynthetic bacteria Nuclear envelope evolving Mitochondrion Plants and plantlike protists Animals, fungi, and non-plantlike protists

10. DOMAIN KINGDOM CELL TYPE CELL STRUCTURES NUMBER OF CELLS MODE OF NUTRITION EXAMPLES Bacteria Eubacteria Prokaryote Cell walls with peptidoglycan Unicellular Autotroph or heterotroph Streptococcus, Escherichia coli Archaea Archaebacteria Prokaryote Cell walls without peptidoglycan Unicellular Autotroph or heterotroph Methanogens, halophiles Protista Eukaryote Cell walls of cellulose in some; some have chloroplasts Most unicellular; some colonial; some multicellular Autotroph or heterotroph Amoeba, Paramecium, slime molds, giant kelp Fungi Eukaryote Cell walls of chitin Most multicellular; some unicellular Heterotroph Mushrooms, yeasts Plantae Eukaryote Cell walls of cellulose; chloroplasts Multicellular Autotroph Mosses, ferns, flowering plants Animalia Eukaryote No cell walls or chloroplasts Multicellular Heterotroph Sponges, worms, insects, fishes, mammals Eukarya Classification of Living Things

11. Eubacteria Archaebacteria Protista Plantae Fungi Animalia Kingdoms DOMAIN EUKARYA DOMAIN ARCHAEA DOMAIN BACTERIA