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 Drift1) 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.

Meet the family!