Same species Same species Same species Same species

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Same species?

Same species?

Same species?

Same species?

Same species?

Same species?

Same species?

Same species?

Same species?

Same species?

Same species?

Same species?

Same species? Rabbit Horse Different species

Same species? Rabbit Horse Different species

Same species? Chihuaha and Great Dane Same species, different breeds

Same species? Chihuaha and Great Dane Same species, different breeds

Same species? Ostrich and Hummingbird Different species��

Same species? Ostrich and Hummingbird Different species��

Same species? Eastern Meadowlark Western Meadowlark Different species

Same species? Eastern Meadowlark Western Meadowlark Different species

Same species? Pheidole barbata ants Same species, different jobs

Same species? Pheidole barbata ants Same species, different jobs

Same species? Happy Face Spiders Same species

Same species? Happy Face Spiders Same species

A species is usually defined as: A group of similar organisms that can mate

A species is usually defined as: A group of similar organisms that can mate and produce fertile offspring.

What about hybrids?

What about hybrids?

Most bacteria reproduce asexually

Most bacteria reproduce asexually

Ring species

Ring species

Extinct species can’t mate

Extinct species can’t mate

Animals separated by geography don’t mate

Animals separated by geography don’t mate

Another way to define a species Branching tree (phylogenetic tree)

Another way to define a species Branching tree (phylogenetic tree)

Comparing nitrogen base sequences in DNA

Comparing nitrogen base sequences in DNA

Comparing developing embryos of different organisms

Comparing developing embryos of different organisms

Comparing body structures (homologous structures)

Comparing body structures (homologous structures)

How do new species form? Evolution: gradual change in a species’ traits over time.

How do new species form? Evolution: gradual change in a species’ traits over time. Natural selection: individuals who are better suited to the environment are more likely to survive and reproduce.

In order for new species to evolve: Groups within the population need to stop

In order for new species to evolve: Groups within the population need to stop exchanging genes (mating) so that they can evolve separately.

Why might two groups of the same organism stop mating?

Why might two groups of the same organism stop mating?

Separated geographically Continental drift

Separated geographically Continental drift

Placental mammals and marsupials

Placental mammals and marsupials

Separated geographically Different environments on each side of the road

Separated geographically Different environments on each side of the road

Separated by lifestyle? Apple flies and Hawthorn flies

Separated by lifestyle? Apple flies and Hawthorn flies

Changes in environment

Changes in environment

Unusual Hybrids

Unusual Hybrids

Imagine that 10, 000 years in the future there is a new human-like species

Imagine that 10, 000 years in the future there is a new human-like species that is 2 feet tall, covered in hair, and has a beak. What might have happened between now and then to cause this new species to evolve?