Chapter 13: Evolution

Evolution Evolution – the idea that life changes over time (not a theory). Example: Megalodon jaw compared to a modern Great White jaw.

We see life change over time due to selective breeding (by humans) - Examples: Dogs, Corn

African elephant tusk size - poaching - Down by 50% in last 150 years. - Elephants with small tusks survive better.

History of Theories of Evolution Roman named Lucretius 1,900 years ago 1809 Jean Baptiste Lamarck - Suggested that evolution happens because of use or disuse of a structure. - Acquired traits are passed on - Example: Giraffe necks

1831 Charles Darwin became Naturalist on the Beagle (a ship). - 5 year voyage collecting samples of life from different places. - Others published ideas about evolution, but none could explain HOW it occurs.

- Darwin saw that life in different places has different characteristics. – finches - Fossils of past life are different from present life forms. – giant armadillo

Natural Selection In 1859, Darwin published his book On the Origin of Species by Means of Natural Selection

Natural selection has 4 major points: All populations have variation among individuals.

2) More offspring are created than can survive in the environment – competition & survival of the fittest

3) Individuals within a population that are better able to survive in their environment are more likely to reproduce.

4) Beneficial traits will increase in a population over time.

Evidence for Evolution Fossils: Fossil links have been found between fish & amphibians, reptiles & birds, and reptiles & mammals

Changes in Proteins and Nucleic Acids: Proteins and nucleic acids change over time from mutations. The more amino acid or nucleotide differences, the further separated the species are.

Phylogenetic tree – diagram that shows how organisms are related through evolution.

Similar anatomy: Homologous structures – structures that share common ancestry. - Arm bones of birds, lizards, and mammals have the same structure.

Vestigial structures – structures that are of no use today, but show a link to a previous ancestor. - Tailbones in humans - Leg bones in snakes - Pelvic bones in whales

Embryology – Embryos show evolutionary similarities that agree with the fossil record and protein or DNA changes.

How is a New Species Made? Divergence - the accumulation of differences between two groups. Speciation – The two groups can no longer breed and are considered two separate species.

Isolation – two populations of a species cannot breed with each other because of location, will cause divergence.

Gradualism – many small changes over a long period of time lead to new species.

Punctuated equilibrium – periods of rapid change separated by periods of little or no change. Thought to be caused by major changes in the environment.

Extinctions – leave openings in the ecosystem where new organisms can be successful. (food sources, habitats, etc.)

Human activities – Humans change the environment and animals adapt. - Peppered moths changed color after the industrial revolution because the trees they lived on were covered in soot.