Evolution on a short time scale Guppies are red or gray Killifish is green Pike cichlid is blue Doesn’t eat much Does eat

Biological Species concept Group of actually or potentially interbreeding natural populations which are reproductively isolated from other such groups If they cannot mate = reproductively isolated (members of a different species) Several reproductive isolating mechanisms – Prezygotic – before formation of offspring – Postzygotic – after formation of offspring

Prezygotic isolating mechanisms Geographic isolation Ecological isolation Temporal isolation Behavioral Isolation Mechanical isolation Prevention of gamete fusion POSTZYGOTIC – Hybrid infertility

Chapter 15 Scientific name (or species name) – Homo sapiens We call this the binomial system of naming First word is the genus (means group) Second word is the species

Linnean system of Classification Each level is called a taxon Taxonomy is the study of such organization King Philip Came Over For Green Spaghetti Each level above includes more animals than the one below For example, Phylum Chordata refers to organisms with a backbone – Class Mammal – Class Sauropsida (lizards and birds) – Class Amphibia – Etc.

What is a species? We defined it earlier as a group of organism that can interbreed and produce fertile offspring – Problem! – Some organisms do NOT sexually reproduce – Others produce hybrids We define a species as a group of organisms that share similar features

How to build a family tree Phylogenetic tree (cladogram) Clade – group of organisms that share a derived trait Derived trait (character) – trait that arose in a common ancestor Cladogram is comparative – something with fur versus something without fur Outgroup – organism that differs in its derived trait (hagfish) compared to all other organisms (ones that have jaws) Ingroup – organisms being compared to ingroup (ones that have jaws) Sometimes cladograms are ‘weighted’ to show that some characters are more important (example birds and lizards)

Kingdoms Bacteria – cell wall Archaea – cell wall, live in extreme environment Protista – single cell that doesn’t fit anywhere else Plantae – cell wall, energy from light Fungi – cell wall, energy from absorption Animalia – no cell wall, energy from digestion Domains Bacteria Archaea Eukarya