The Evolutionary Story

A story of life...

At the beginning Atmosphere of carbon monoxide, carbon dioxide, nitrogen, methane, hydrogen, ammonia, water vapour and little or no oxygen Active volcanoes, lightning and UV radiation from the sun were all very intense

How did life begin? Primary Abiogenesis Theory hypothesized in the 1920’s by both Alexander Oparin and JBS Haldane independently States that the first living things on Earth arose from non-living material (organic molecules).

1. Formation of Organic Molecules

Life beginnings cntd... 2) Small molecules joined into large ones such as proteins and nucleic acids. 3) Molecules that could copy themselves arose providing a basis for inheritance of molecular info 4) The molecules became packaged within mebranes (pre-cells).

Under the sea... Earth’s surface was too hot for pre-cells to survive. Deep-sea hydrothermal vents probably best place to supply energy and chemical raw materials required for origin of life.

The oldest fossils Prokaryotic bacteria that could function without oxygen (anaerobic). Chemoautotrophs- synthesize organic molecules from inorganic materials without needing light energy. Some chemoautotrophs must have released oxygen as a by-product (Free Oxygen becomes available). As raw chemicals are used up, an organism that can photosynthesize and then use the by-product to release energy evolved and became adapted (aerobic). Stromatolites- thin layers of sediment bound together into rocks by photosynthetic prokaryotes (3.5 billion yrs ago)

The Prokaryotes Gave rise to first Archaebacteria and Eubacteria.

Endosymbiotic Theory: How Eukaryotes Evolved? Some prokaryotes lost their cell walls. Engulfed another aerobic heterotrophic bacteria (but did not digest).

Support for Endosymbiosis Mitochondria and chloroplasts are different from other organelles Surrounded by 2 membranes Have their own DNA Replicate their own DNA and undergo division independently from host cell

Continental Drift 1) Formation of Pangea 250 mill yrs ago plate movements brought all land masses together into one supercontinent (Pangaea). Caused many environmental changes which lead to the extinction of a number of species 2) Breakup of Pangea 180 mill yrs ago continents drifted apart and each became a separate and isolated evolutionary arena Species on different continents diverged as they adapted on the now separate continents

In Context

Phylogenetic Relationships Phylogeny- The evolutionary development or history of a species or group. Phylogenetic Tree- A branching diagram that represents the evolutionary relationships among species or groups. Taxonomy- The science concerned with classifying organisms.

Constructing a phylogenetic tree Structural Anatomy of organism’s body. Use Homologous structures to establish relationships. Molecular data. Compare genes (DNA) and proteins expressed across organisms. Best trees are constructed by using supporting evidence from multiple sources.

Constructing a Phylogenetic Tree

Cladistics Each evolutionary branch in a phylogenetic tree is called a clade. Clades can nest within larger clades. All organisms within a clade must share homologous structures (also called derived characters) that do not occur outside the clade.

A Cladogram A phylogenetic diagram that specifies the derived characters of clades.

Primate Phylogeny Primate: have grasping hands and feet with opposable first digits.

Primate Phylogeny cntd. Hominoids- Large brains, no tails and swinging arms. Hominids- Ancestral species and humans that arose after split from chimpanzees. Bipedalism- ability to walk on two feet.

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