phylogeny Flashcards
phylogeny
Phylogeny is the name given to the evolutionary relationships between organisms. The study of the evolutionary history of groups of organisms is known as phylogenetics. It reveals which group a particular organism is related to, and how closely related these organisms are. You will learn more about the evidence that scientists use to study evolutionary relationships in the next topic.
Classification can occur without any knowledge of phylogeny, as occurred in the past. However, it is the objective of many scientists to develop a classification system that also correctly takes into account the phylogeny of an organism.
phylogenetic trees
A phylogenetic tree (or evolutionary tree) is a diagram used to represent the evolutionary relationships between organisms. They are branched diagrams, which show that different species have evolved from a common ancestor.
The diagram is similar in structure to that of a branching tree - the earliest species is found at the base of the tree and the most recent species are found at the tips of the branches.
Phylogenetic trees are produced by looking at similarities and differences in species’ physical characteristics and genetic makeup.
Much of the evidence has been gained from fossils.
advantages of phylogenetic classification
phylogeny can be done without reference to Linnaean classification. Classification uses knowledge of phylogeny in order to confirm the classification groups are correct or causes them to be changed. For example, a dolphin has many of the Pleistocene
same characteristics as a fish, so in theory a dolphin could be classified as a fish. However, knowledge of the phylogeny of dolphins confirms its classification as a mammal.
Pliocene
Other advantages:
• Phylogeny produces a continuous tree whereas classification Miocene
requires discrete taxonomical groups. Scientists are not forced to put organisms into a specific group that they do not quite fit.
-The hierarchal nature of Linnaean classification can be Oligocene
misleading as it implies different groups within the same rank are equivalent. For example, the cats (Felidae) and the orchids (Orchidaceae) are both families. However, the two groups are not comparable one has a longer history than the other (cats have existed for around 30 million years, but orchids have been in existence for over 100 million years).
The two families also have different levels of diversity (with approximately 35 cat species and 20000 orchid species) and different degrees of biological differentiation (many orchids of different genera are able to hybridise, but cats cannot).
