The Origin of Species Chapter 22

The Origin of Life Alexander Oparin and coacervates Theory that extends evolution back to the Earth’s beginning to explain how life began.

The Biological Species Concept Individuals in the population can mate and produce fertile offspring Individuals in different populations would mate and produce fertile offspring if they came in contact naturally. Liger

The Nature of Species Two types of speciation: Sympatric Allopatric Within species you also have subspecies.

Reproductive Isolating Mechanisms There are two types: Prezygotic isolating mechanisms Geographic isolation Ecological isolation Behavioral isolation Temporal isolation Mechanical isolation

Behavioral isolation Temporal Isolation Breeds Jan - March Breeds late March - May

Mechanical Isolation

Reproductive Isolating Mechanisms 2. Postzygotic Isolating Mechanisms - “Processes that prevent hybrid zygotes from developing into normal, functioning, fertile adults”.

Problems with the Biological Concept How reproductively isolated are the species? Difficult to apply to allopatric populations. Doesn’t apply to asexual species. Alternative: Ecological Species Concept

Geography of Speciation Speciation is a 2-part process Initially identical populations must diverge Reproductive isolation must evolve to maintain these differences a. b. c.

Allopatric Speciation Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Allopatric Speciation Isolated island population of kingfishers Isolated island population of kingfishers Mainland population of kingfishers NEW GUINEA PACIFIC OCEAN Isolated island population of kingfishers Mainland population of kingfishers

Sympatric speciation

Speciation Adaptive Radiation: Character Displacement: “Natural selection favors those individuals that use resources not used by other species” Adaptive Radiation: “Closely related species that have recently evolved from a common ancestor by adapting to different parts of the environment”

Adaptive Radiation

Character Displacement

Adaptive Radiation and Darwin’s finches Ancestors reached these islands before other land birds. Ground finches Tree finches Vegetarian finch Warbler finches

The Pace of Evolution

Speciation and Extinction Speciation, through time, has surpassed extinction Five mass extinctions have occurred.

Speciation and Extinction Not all groups are affected equally by mass extinctions. Previously dominant groups may perish, changing the course of evolution. The 6th extinction is currently underway.