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Notes: SPECIES and SPECIATION. Species - A group of similar organisms Can breed with each other and produce fertile offspring Examples: Human species ( Homo sapiens) Horses and donkeys = two separate species because their offspring (mules) aren’t fertile. Objectives for Class:
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Notes: SPECIES and SPECIATION Species - • A group of similar organisms • Can breed with each other and produce fertile offspring Examples: • Human species (Homo sapiens) • Horses and donkeys = two separate species because their offspring (mules) aren’t fertile • Objectives for Class: • Explain the defining characteristics of a species • Describe the 2 steps of speciation
Speciation - • The formation of new species from a common ancestor • The gene pools of two populations must become separated Ex: The Galapagos Finches • Objectives for Class: • Explain the defining characteristics of a species • Describe the 2 steps of speciation
Two Main Steps of Speciation • Reproductive Isolation • Changes in the Gene Pool • Gene Pools Diverge (become different) • Genetic Barriers to Reproduction Arise (groups can’t interbreed and make fertile offspring) • Objectives for Class: • Explain the defining characteristics of a species • Describe the 2 steps of speciation
Step 1: Reproductive Isolation One population becomes separated and stops breeding with the rest of the species a) Geographic • Geographic barrier splits population (i.e.: river, mountain, body of water, etc.) • Populations are separated and cannot interbreed b) Behavior: • Changes in courtship or other reproductive strategies c) Temporal • Species reproduce at different times or have other behavior that becomes time sensitive (i.e.: feeding) • Objectives for Class: • Explain the defining characteristics of a species • Describe the 2 steps of speciation
Step 2: Changes in the Gene Pool • Gene Pools Diverge (become different): • The isolated populations become genetically different. • The new environments or behaviors favor different genetic traits (natural selection) • Genetic Barriers to Reproduction Arise • The two populations can no longer interbreed • Due to genetic differences in habitat preference, mating behavior, or physical compatibility They are now two separate species! • Objectives for Class: • Explain the defining characteristics of a species • Describe the 2 steps of speciation
Hybrid - • The offspring of a mating between two different species • If a hybrid can’t have offspring, there are still two separate species!
