phylogeny and systematics

PHYLOGENY AND SYSTEMATICS

Phylogeny- the evolution history of a species

Systematics- the study of the diversity of life and its phylogenetic history

Fossils

• Fossil record is a substantial but incomplete chronicle of evolutionary history

Zinjanthropus (affectionately known as "Zinj Man", the upper image to the right),

Systematics

• Uses an evolutionary context to study diversity; traces phylogeny using the fossil record, molecular data and other approaches

• Taxonomy is part of systematics

Taxonomy

• Kingdom• Phylum• Class• Order• Family• Genus • Species• The science of classification

Our current system of taxonomy was developed by Carl Linneaus; written in

Latin

Taxon- taxonomic unit at any level

Phylogenic tree represents this taxonomic hierarchy

Binomial nomenclature- Scientific name of an organism consists of its Genus and species (italized)

The lion belongs to the following groups:•Kingdom Animalia (includes all animals)•Phylum Chordata (includes all vertebrate animals, as well as some other more primitive ones)•Class Mammalia (includes all mammals)•Order Carnivora (includes carnivorous mammals, from bears to raccoons to harbor seals)•Family Felidae (includes all cats)•Genus Panthera (includes the great roaring cats: lions, tigers, jaguars, and leopards)•Species leo (lions!)

Cladistic analysis-used to reconstruct evolutionary history and to then construct

phylogenetic trees

A cladogram is a phylogenetic tree with a series of two-way branches (dichotomies). Each dichotomy represents the divergence of two species from a common ancestor.

If the group represents the ancestral species and all of its descendents it is said to be monophyletic taxon (also called a clade)

If the group includes organisms having different ancestry it is said to be polyphyletic taxon

If the group represents some species but excludes some species that share a common ancestor with other species in the taxon it is said to be paraphyletic taxon

A cladogram is based on similarities that reflect relatedness

• For example:

Homology- likeness based on shared ancestry

Homologous structures have the same basic structure but may not have the same function any longer

Analogous structures have the same features without a shared

evolutionary history

This is due to convergent evolution – natural selection leads to similar adaptations because the niche is similar.

Examples of analogous structures :

The jointed leg of insects and vertebrates

The tail fin of fish, whales and lobsters

The eyes of vertebrates and cephalopod

The wings of bats, birds and insects

Shared primitive characters- common to more inclusive taxa

Shared derived characters- unique to a clade (“newly” developed)

Parsimony- the smallest number of evolutionary changes is the simplest explanation and thus the best estimate of the relationships among species

Know these roots:• Analog• Bi• Clado• Homo• Mono• Parsi• Phylo• -geny• nom