Evidence for Evolution

Biology 12

Evolution

An error in DNA can be silent causing no changes in an organism or, if it occurs in the sex cells, can result in mutations in the next generation.

Some mutations have no good or bad effects on an organism unless the environment changes.

Then, some individuals might be better able to withstand the changes and survive to reproduce.

Evidence for Evolution

By looking at Artificial Selection (ex. Animal husbandry, development of new plant varieties), Darwin suggested that Natural Selection could take place.

Charles Darwin knew about fossils and the work of Cuvier who noticed that older remains were usually found in deeper sedimentary rock.

Evidence for Evolution

Anatomy homologous features like the forelimbs of

mammals, embryo development across species, analogous features like wings and vestigal features like a third eyelid.

Homologous Features

Evidence for Evolution

Fossils

Dinosaur bones, imprints of organisms(tracks), insects in amber, coprolites

Fossils are actually quite rare because they are formed under special conditions, must survive

Evidence for Evolution

Biogeography

similar fossils and rocks found in different parts of the world due to the movement of tectonic plates.

Evidence for Evolution

Radiometric dating of rocks and fossils

The half-life of certain elements such as Carbon-14, Uranium-235 and Potassium-40 can be measured very accurately.

Carbon-14 dating is for materials which are 100 – 100 000 years old (younger).

Uranium- 235 dates materials which are 10 million – 4.6 billion years old.

Evidence for Evolution

DNA research

Genetic markers in the human genome allow scientists to track how closely related different populations are.

Recent research has tracked the movement of human ancestors out of Africa at various times in the distant past.

The Pace of Evolution

• Evolution can be slow or fast because it depends on changes in the environment. For example, the rise of the Polar Bear as a species is quite recent since the beginning of the last Ice Age.

• As the climate changes, and the polar caps recede, what might happen to this species? Is this necessarily a bad thing?

Do all organisms evolve continually?

• Some groups of organisms such as the crocodile have changed little since when they first appeared before the Age of Dinosaurs.

• Why might this be so?

Looking ahead….

• Some scientists believe that the disappearance of species due to climate change is the beginning of another major extinction.

• What does this mean for life on Earth?