What is Phylogeny?

Biologists estimate that there are about 5 to 100 million species of organisms living on Earth today. Evidence from morphological, biochemical, and gene sequence data suggests that all organisms on Earth are genetically related, and the genealogical relationships of living things can be represented by a vast evolutionary tree, the Tree of Life.

The Tree of Life then represents the phylogeny of organisms, i. e., the history of organismal lineages as they change through time. It implies that different species arise from previous forms via descent, and that all organisms, from the smallest microbe to the largest plants and vertebrates.

Organisms have evolved through the ages from ancestral forms into more derived forms. New lineages generally retain many of their ancestral features, which are then gradually modified and supplemented with novel traits that help them to better adjust to the environment they live in. Studying the phylogeny of organisms can help us explain similarities and differences among plants, animals, and microorganisms.

The Tree of Life thus provides a rigorous framework to guide research in all biological subdisciplines, and it is therefore an ideal model for the organization of biological knowledge.



HOMEWORK:

Read and take detaield notes from textbook on pages 403 - 408.

Answer questions 1 - 7 on page 408