Evolution and Populations EVIDENCE OF EVOLUTION STRUCTURAL ADAPTATIONS

EVIDENCE OF EVOLUTION • STRUCTURAL ADAPTATIONS – MIMICRY – CAMOUFLAGE http: //evolution. berkeley. edu/evolibrary/home.

EVIDENCE OF EVOLUTION • STRUCTURAL ADAPTATIONS – MIMICRY – CAMOUFLAGE – MILLIONS OF YEARS

http: //evolution. berkeley. edu/evolibrary/home. php WHAT OTHER INDUSTRIES WOULD BE WORRIED ABOUT RESISTANCE? Life

OTHER EVIDENCE OF EVOLUTION • • FOSSILS ANATOMY – HOMOLOGOUS STRUCTURES indicate a related

OTHER EVIDENCE OF EVOLUTION • FOSSILS • ANATOMY – HOMOLOGOUS STRUCTURES – ANALOGOUS STRUCTURES

Convergent Evolution • Species from different evolutionary branches may come to resemble one another

CONVERGENT EVOLUTION – WHAT IS AN EXAMPLE? http: //evolution. berkeley. edu/evolibrary/home. php Life Sciences-HHMI

Chapter 16—Populations • 16. 1 • A population consists of all the individuals of

• Though a population’s growth is limited by factors such as predation and

• Some populations grow quickly in response to –density-independent factors (weather, climate). Ex.

Mutation • random, heritable changes in DNA that introduces new alleles into a gene

• Gene pool– is the set of possible gene combinations in a given

• 16. 2 • Natural selection means one species has a benefit that

• Polygenic traits are those which are influenced by several genes. Ex. Skin

• 2 Types of Natural selection: • Directional selection—shift phenotypes toward one extreme

Directional selection Beak size selection in a Galápagos population of the medium ground finch

2. Directional Selection • Favors variants of one extreme Number of Individuals Small Large

3. Diversifying Selection • Favors variants of opposite extremes Number of Individuals Small Large

• Stabalizing selection—range of phenotypes narrows • Ex. Increase the number of “average”

1. Stabilizing Selection • Acts upon extremes and favors the intermediate Number of Individuals

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Evolution and Populations

EVIDENCE OF EVOLUTION • STRUCTURAL ADAPTATIONS – MIMICRY – CAMOUFLAGE http: //evolution. berkeley. edu/evolibrary/home. php http: //science. howstuffworks. com/animal-camouflage 2. htm Life Sciences-HHMI Outreach. Copyright 2006 President and Fellows of Harvard College.

EVIDENCE OF EVOLUTION • STRUCTURAL ADAPTATIONS – MIMICRY – CAMOUFLAGE – MILLIONS OF YEARS • PHYSIOLOGICAL ADAPTATIONS – CHANGE IN A METABOLIC PROCESS – WHAT DO YOU HEAR ABOUT IN THE NEWS ABOUT SOME BACTERIA? Life Sciences-HHMI Outreach. Copyright 2006 President and Fellows of Harvard College.

OTHER EVIDENCE OF EVOLUTION • • FOSSILS ANATOMY – HOMOLOGOUS STRUCTURES indicate a related evolutionary ancestry, not just similarity http: //evolution. berkeley. edu/evolibrary/home. php Life Sciences-HHMI Outreach. Copyright 2006 President and Fellows of Harvard College.

OTHER EVIDENCE OF EVOLUTION • FOSSILS • ANATOMY – HOMOLOGOUS STRUCTURES – ANALOGOUS STRUCTURES similar in appearance and function but are not the result of shared ancestry. http: //evolution. berkeley. edu/evolibrary/home. php Life Sciences-HHMI Outreach. Copyright 2006 President and Fellows of Harvard College.

Convergent Evolution • Species from different evolutionary branches may come to resemble one another if they live in very similar environments. • Example: 1. Ostrich (Africa) and Emu (Australia). 2. Sidewinder (Mojave Desert) and Horned Viper (Middle East Desert)

Chapter 16—Populations • 16. 1 • A population consists of all the individuals of a species that live together in one place at one time. • • Population density is the number of individuals in a given area. • • A population’s future survival is determined by its size, density, and dispersion. •

• Though a population’s growth is limited by factors such as predation and available sources, a population can grow rapidly and may eventually stabilize at a size that the environment can sustain. • Species - a group of populations whose individuals have the ability to breed and produce fertile offspring.

• Some populations grow quickly in response to –density-independent factors (weather, climate). Ex. Mosquito populations • • Some populations grow more slowly and their size is controlled by density dependent factors (limited resources—food, water).

Mutation • random, heritable changes in DNA that introduces new alleles into a gene pool

• Gene pool– is the set of possible gene combinations in a given population (breeding options—different offspring trait choices/combinations)

• 16. 2 • Natural selection means one species has a benefit that allows them to survive more than another. • Natural selection acts only on phenotype, not on genotype.

Modes of natural selection

Modes of selection

• Polygenic traits are those which are influenced by several genes. Ex. Skin color, height • The range of phenotypes controlled by polygenic traits results in a normal distribution when plotted on a chart. Figure 16 -12.

• 2 Types of Natural selection: • Directional selection—shift phenotypes toward one extreme • Ex. Pesticide or antibiotic resistance

Directional selection Beak size selection in a Galápagos population of the medium ground finch

2. Directional Selection • Favors variants of one extreme Number of Individuals Small Large Size of individuals

3. Diversifying Selection • Favors variants of opposite extremes Number of Individuals Small Large Size of individuals

Stabilizing selection

• Stabalizing selection—range of phenotypes narrows • Ex. Increase the number of “average” individuals

1. Stabilizing Selection • Acts upon extremes and favors the intermediate Number of Individuals Small Large Size of individuals

Diversifying selection