Speciation

What is a species? A species is— A group of organisms with similar internal and external structures that can interbreed to produce fully fertile offspring Species that exist today are essentially changed versions of older species

How do species give rise to other different species? Speciation is a word used to describe the process of changes adding up over time and resulting in a new species 1 species branches into 2 closely related species Over time they may stay very similar to the ancestral species or to each other, or they may become very different over time

What causes branching to occur? 1st Isolation Two or more parts of a population (species) stop interbreeding- gene flow between them stops forming 2 different gene pools Types of isolation: Geographic Isolation Post-mating Isolation Behavioral Isolation Temporal Isolation Then The Big 3! 1)Natural Selection 2) Genetic Drift 3) Mutations

Geographic Isolation The original population is separated into two or more populations by physical barriers such as canyons, mountains, bodies of water, deserts, or any geographic feature they can’t cross The Big 3! - Natural selection ,genetic drift and mutations cause different changes to occur in each new population Since they no longer share genes these changes add up over time until they look and behave so different they no longer breed

Geographic Example: Pupfish

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Geographic Example: Grand Canyon Squirrels

Draw AND explain Geographic Isolation in your own words

Post Mating Isolation 1= Mate but can’t produce any offspring OR 2= Mate and produce offspring but the offspring is infertile (can’t have babies)

Behavioral Example In this isolation two populations could breed but have different ways of attracting their mates

Temporal Example The populations reproduce at different times Example:

Speciation Big Ideas!!! Isolation + The Big 3– 1) Natural Selection 2) Genetic Drift 3) Mutations