Evidence for evolution

Anatomy

Species may share similar physical features because the feature was present in a common ancestor.

Fossils

They document the existence of now extinct past species that are related to present day species

Natural history

Traits present in organisms can be understood only in view of their evolutionary path.

Embryology

Similarities in embryonic development across different species suggest a common ancestor.

Biogeography

The global distribution of organisms reflects evolution and geological change.

Homology

Two traits that have descended from a common ancestral character

Analogy

Character similar function/ not common ancestry due to convergent evolution.

Who is the selector in natural selection?

In natural selection, there is no breeder or selector — survival acts as the selector. It's not about survival of the fittest, but about the survival of the ability to reproduce (e.g., peacocks).

Concept of homology

Applies to genes, proteins and so on

Also provides the basis for phylogenetic trees.

What is the Principle of Superposition?

The principle that deeper rock layers are older than shallower ones because they were laid down first.

How do we date fossils?

We can calculate the date of formation of the igneous rock, using radioactive isotopes decay.

What is found in the fossil record regarding transitional forms?

Transitional forms exist in major groups, showing evolutionary changes.

What can be observed within species in the fossil record?

Variation within each species can be seen.

What does the fossil record reveal about adaptations?

It shows imperfect adaptations in some species.