B.9A Evidence of Common Ancestry on level – 04

 
The continents 250 million years ago were a single landmass called Pangea. Over time, the continents moved apart from one another. This is called continental drift.

Identical crocodile fossils were found on both Africa and South America, thousands of miles apart. This shows that the crocodiles lived there when the continents were joined. The continents split after these crocodiles died and their bones became fossils.

 
Islands are separated from other landforms by oceans. Many islands have living things that are unique to those islands.

 

 

Homologies

Homology refers to the similarities in body structures, body functions, and development of different species of living things. These similarities are evidence that living things have a common ancestor.

Homologous Anatomical Structures

Homologous structures are similar physical features in organisms.

 
All of the animals in this picture have the same kinds of bones in their limbs. Each of the limbs may serve a different function, but the bones inside the limb are very similar.

Molecular Homology

Molecular homology is the similarities in the genome of different organisms.

A genome is an organisms complete set of genes. Scientists can compare genomes of different organisms to see how similar or different they are from each other. Any time there is a change in the gene sequence of an organism, those changes are passed on to the offspring. By looking at the changes in the gene sequence between organisms, scientists can determine how closely or distantly those organisms are related to a common ancestor.

Genes code for amino acids. Chains of amino acids produce proteins. Below is a chart of the amino acids that produce the protein Cytochrome-c, which is a protein found in the mitochondria of cells.