Evidence of evolution

What are the three main sources of evidence used to study the process of evolution?

Palaeontology (study of fossils/fossil record), comparative anatomy (similarities/differences in anatomy), and comparative biochemistry (similarities/differences in chemical makeup).

What evidence do fossils of the simplest vs. most complex organisms provide for evolution?

Fossils of the simplest organisms (e.g., bacteria) are found in the oldest rocks, while fossils of complex organisms (e.g., vertebrates) appear in more recent rocks, supporting the theory that simple life forms gradually evolved into complex ones.

Why is the fossil record considered incomplete?

Many organisms are soft-bodied and decompose before fossilising, conditions required for fossilisation are rare, and many fossils have been destroyed by geological movements (like volcanoes) or remain undiscovered.

What is a homologous structure, and what type of evolution does it provide evidence for?

A structure that appears superficially different and may perform different functions in different organisms, but has the same underlying structure (e.g., the pentadactyl limb). It provides evidence for divergent evolution.

What is divergent evolution?

How species evolve from a common ancestor, each adapting with different features to suit new habitats as a result of migration or loss of habitat.

How does evolutionary embryology support the theory of evolution?

Embryos of different animals (e.g., vertebrates) look remarkably similar in their earliest stages, implying that embryonic development processes share a common origin and that the animals share common ancestry.

Which two molecules are commonly studied in comparative biochemistry to determine evolutionary links?

Cytochrome c (a protein involved in respiration) and ribosomal RNA (rRNA).