How does a species evolve from preexisting species? Speciation How does a species evolve from preexisting species?

What is a Species? Group of organisms that look alike, can interbreed, & mate to produce fertile offspring in nature

What do you get when you breed a donkey and a horse? A MULE!!! Does the mule fit the definition of a species?

Why does a MULE NOT fit the definition of a species?? Can interbreed X Produce fertile offspring Do so in nature

What do get when you breed a tiger and a lion? A LIGER!!! Does the liger fit the definition of a species?

Why does a LIGER NOT fit the definition of a species?? Can interbreed X Produce fertile offspring X Do so in nature

Speciation = evolution of a new species Happens b/c reproductive isolation 3 ways

1. Behavioral Isolation B/C different courtship rituals or other reproductive behaviors, like bird calls/songs Ex. Eastern & Western Meadowlark

2. Geographical Isolation When physical barriers (mountains, rivers, highways) separate populations Ex: Grand Canyon squirrels, Darwin’s finches

3. Temporal Isolation B/C pops reproduce @ different times Ex. species of orchids & frogs

Speciation can occur slowly or quickly 2 theories

Gradualism Species originate through a slow, steady change in adaptations Proposed by Darwin Supported by the fossil record

Punctuated Equilibrium Speciation occurs quickly in rapid bursts, with long periods of stability Caused by environmental changes (ex. 3 isolations) Supported by fossil record

2 Patterns of Macroevolution Species will diversify when introduced to a new environment or become extinct. 2 Patterns of Macroevolution

1. Divergent Evolution (adaptive radiation) When species evolves into diverse new species B/c different environments Have homologous structures Ex: polar vs. brown bear, Hawaiian honeycreeper

2. Convergent Evolution Distantly related (or unrelated) organisms evolve similar traits B/C similar environments Have analogous structures

Examples Dolphin, penguin, fish - Streamlined shape b/c need to move thru water efficiently Bird, bat, butterfly

Extinctions: 1. Background extinction - normal extinction rate, species that go extinct simply because not all life can be sustained on Earth and some species simply cannot survive.  2. Mass extinction  - widespread event that wipes out the majority (over 50%) of living plants and animals.

Coevolution - the process by which two or more interacting species evolve together, each changing as a result of changes in the other or others Beneficial relationships ex. Acacia plant and stinging ant Competitive relationships Crabs and murex snails Evolutionary arms race newt & snake 2:20-8:26min https://www.youtube.com/watch?v=iTjkSDaXF7s Bull horn acacia and ants have a mutualistic relationship with many facets: a. large thorns provide nesting for ants, b. Beltian bodies (and nectar) provide food for ants, c. ants swarm to defend anything eating the tree, and d. the ants also clear an area around the base of the tree to reduce competition for nutrients. Artist: Emily Harrington.  For example, many molluscs, such as Murex snails, have evolved thick shells and spines to avoid being eaten by animals such as crabs and fish. These predators have, in turn, evolved powerful claws and jaws that compensate for the snails' thick shells and spines.