Taxonomy and Cladograms

Taxonomy Definition: is the grouping of objects or organisms based on a set of criteria.

Classification - A. Order and Example Human example: Kingdom Animalia Phylum Chordata Class Mammalia Order Primates Family Hominidae Genus Homo Species sapiens

I. CLASSIFICATION Which organisms are more related, same family or same genus? Answer: Genus

Q: Which level of classification is the largest? Q: Which level of classification is the smallest?

Mice and rats belong to the same family Mice and rats belong to the same family. Which of these is NOT the same between mice and rats? Species Kingdom Order Phylum

Cladograms

What is a species anyway? A species is often defined as a group of individuals that actually or potentially interbreed in nature. In this sense, a species is the biggest gene pool possible under natural conditions In other words, produce fertile offspring (fertile- reproduce)

Species example: Happy face spiders look different, but since they can interbreed, they are considered the same species: Theridion grallator.

Species example: Dogs. There are 5000 different breeds of dogs, but they are all of the same species.

The Dog Fossil evidence shows that all dogs, Canis familiaris, have a common ancestor - the wild grey wolf. Over 14,000 years humans have 'designed' some 5,000 breeds of domestic dog, artificially selecting the looks and behavior of each breed.

Species example: These Spotted Owls look similar, but are two different species, unable to interbreed with one another.

Speciation Speciation is an event that produces two or more separate species.

Reproductive isolation- the evolution of gene flow is necessary for speciation to be complete. Speciation requires that the two similar species be unable to produce viable offspring together or that they avoid mating with members of the another group.

Examples of Reproductive Isolation The evolution of different mating location, mating time, or mating rituals:                                             

Examples of Reproductive Isolation Lack of "fit" between sexual organs These damselfly penises illustrate just how complex insect genitalia may be.

Examples of Reproductive Isolation Offspring inviability or sterility: All that courting and mating is wasted if the offspring of matings between the two groups do not survive or cannot reproduce. STERILE Horse Donkey Mule

Examples of Reproductive Isolation Ligers and Tigons ohh my! Hybrids can form when two species cross mating zones. The magority of males are sterile and are considered “unsuccessful” as a species. S T E R I L E

Cladogram Definition – an evolutionary tree tracing common ancestors through the process of speciation

How to read a cladogram Common Ancestor

According to the diagram, which species is the direct ancestor to Tyrannosaurus? Answer: Tetanurae

Human Cladogram