Speciation How does a species evolve from preexisting

Speciation How does a species evolve from preexisting species?

What is a Species? n 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? ? ü Can interbreed X Produce fertile offspring ü 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? ? ü Can interbreed X Produce fertile offspring X Do so in nature

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

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

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

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

Speciation can occur slowly or quickly 2 theories

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

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

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 n B/c different environments n Have homologous structures n Ex: polar vs. brown bear, Hawaiian honeycreeper n

2. Convergent Evolution n 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 n Bird, bat, butterfly n

Extinctions: n 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 n Beneficial relationships • ex. Acacia plant and stinging ant n Competitive relationships • Crabs and murex snails • Evolutionary arms race newt & snake 2: 208: 26 min https: //www. youtube. com/watch? v=i. Tjk. SDa XF 7 s