SPECIES AND SPECIATION Objectives: Identify factors that have contributed to the diversity of species. Explain how new species form. Explain how scientists infer evolutionary relationships among species. Explain what causes the extinction of species.

What is a species? Morphological Species Concept Phylogenetic Species Concept Biological Species Concept

Morphological Species Concept Use physical similarities to classify species Morpho: form, structure

Phylogenetic Species Concept Use shared, unique genetic history to classify species The term phylogenetics is of Greek origin from the terms phyle/phylon (φυλή/φῦλον), meaning "tribe, race," and genetikos (γενετικός), meaning "relative to birth" from genesis (γένεσις, "birth"). Def. A species is a group of organisms with a shared, unique genetic history. A monophyletic group contains all of the descendents of a single common ancestor.

Biological Species Concept Use ability to mate and produce offspring that can also mate and reproduce to classify species Species: a group of organisms that are physically similar and can mate with each other and produce offspring that can also mate and reproduce. Def. A group of populations that is reproductively compatible with one another, but not compatible with other species. Mules are the result of the love shared by a male donkey and a female horse. These two animals evolved from the same creature so they are still genetically similar enough to produce offspring. Only one problem - horses and donkeys have a differing number of chromosomes (64 and 62, respectively) which means the mule is actually a genetic mess. One major side effect of this darwinistic God-playing is that mules can never reproduce - they are born sterile.  A mule is an example of a “hybrid.”

How do species form? When a group of individuals remains isolated from the rest of its species long enough to evolve different traits How can some members of a species become separated from the main group? Once isolated, members can no longer mate with the rest of their species (if they don’t mate, their DNA will not mix and they will diverge).

Geographical Isolation Physical barrier Ex. River, mountains, ocean, volcano

Temporal Isolation Reproduce at different times Temporal: of or relating to time Temporal isolation is a prezygotic barrier in which the two species reproduce at different times of the day, season, or year. Wood and leopard frogs are an example of two similar species whose ranges overlap.

Habitat/Spatial Isolation Occupy different habitats in the same area The cassowary (genus Casuarius) is a very large flightless bird native to the tropical forests of New Guinea, nearby islands and northeastern Australia. Yellow-crested Cockatoo (Cacatua sulphurea). Also known as the Lesser Sulphur-crested or Citron-crested Cockatoo, this popular pet species is endemic to Indonesia.

Behavioral Isolation Different courtship displays The Western meadowlark (left) and the Eastern meadowlark (right) appear to be identical, and their ranges overlap, but their distinct songs prevent interbreeding. Organisms may appear to be alike and be different species. For example, Western meadowlarks (Sturnella neglecta) and Eastern meadowlarks (Sturnella magna) look almost identical to one another, yet do not interbreed with each other—thus, they are separate species according to this definition.

Resource Isolation Use different resources in the same area

Mechanical Isolation Physically incompatible

Activity Draw a diagram of your method of speciation Write a description of what is happening Organize students into groups of 4-6. Assign each group a different method of isolation to draw. Organisms in the drawings can be real or imaginary. Ask the students to write a description of their drawing. If time permits, have groups present their picture to the class and have the other students guess the method of isolation.