EVOLUTIONARY PROCESSES AND PATTERNS

• Theory of Special Creation– Species unchanged

through time & independent of one another

EVOLUTIONARY PROCESSES AND PATTERNS

• Theory of Spontaneous Generation– New organisms (species)

suddenly appear

EVOLUTIONARY PROCESSES AND PATTERNS

• Prior to Darwin and Wallace - Lamarck

EVOLUTIONARY PROCESSES AND PATTERNS

• Theories of Evolution• Darwin and Wallace

– Species are related to one another, and they change over time, thus species existing today have descended, with modifications, from other preexisting species

Evolution

• What is evolution?

• Microevolution:

• Macroevolution:

Population Characteristics

• Species– A group of

organisms capable of interbreeding

Population Characteristics

• Species– A group of

organisms capable of interbreeding and producing fertile offspring.

– Isolated gene pools

• Isolation– Temporal– Spatial– Mechanical– Behavioral

Genes go in but they don’tCome out!

Evolution

• Allopatric Speciation

Evolution• Sympatric

Speciation

?

Evolution• Parapatric

Speciation

?

Darwinian Selection

• All natural selection results in evolution, but not all evolution is the product of natural selection.

• What is evolution?

• What is natural selection?

• What is an adaptation?

Darwinian Selection• All natural selection results in evolution, but not all evolution is

the product of natural selection.• What is evolution?

Darwinian Selection

• All natural selection results in evolution, but not all evolution is the product of natural selection.

• What is evolution?– Evolution is the change in allele frequencies (or traits)

over time.

• What is natural selection?

• What is an adaptation?

Darwinian Selection• All natural selection results in evolution, but not all

evolution is the product of natural selection.• What is evolution?

– Evolution is the change in allele frequencies (or traits) over time.

• What is natural selection?– Natural selection is the differential reproductive success

resulting from an adaptation.

• What is an adaptation?

Insects, spiders, nectar

Tools use to get insects

Leaves and fruit

Ticks off of iguanas etc.

Seeds

Darwinian Selection

Is there variation about a trait?

Darwinian Selection

Is there an excess of individualsso that only some animals liveto reproduce?

Are resources limited?

Darwinian Selection

- Drought of 1977 eliminated seed set by most of the plants producing small soft seeds. -Large and hard seeds became dominant food item. -Only large birds with deep beaks could defend resources and access the resources

Darwinian Selection

Did evolution occur?

- 1983 El Niño produced 1359 mm of rain and lavish seed set by the small soft seeded plants. -Birds with shallow beaks harvest these seeds more efficiently and thus reproduced better than birds with deep beaks, undoing the selection shown here. - Fluctuating environmental conditions maintained both phenotypes.

Types of Selection

• Directional Selection

• Stabilizing Selection

• Disruptive selection

Directional Selection

• Phenotype at one extreme of population distribution has selective advantage.

• Leave more offspring

Types of Selection

• Directional Selection

• Stabilizing Selection

• Disruptive selection

Stabilizing Selection

• Intermediate phenotypes have selective advantage.

Types of Selection

• Directional Selection

• Stabilizing Selection

• Disruptive selection

Disruptive Selection

• Intermediate phenotypes selected against

Darwinian Selection

• The consequences of natural selection are expressed at the population level.

Genetic drift

• Genetic drift results in a gradual loss of genetic diversity

• Over time an individual locus and gene frequency will drift until one allele becomes fixed

Convergent Evolution

ISOLATION AND CONVERGENT EVOLUTIONConvergence

– Myrmecophagesanteaters, aardvark, aardwolf, numbat,

pangolins

ISOLATION AND CONVERGENT EVOLUTION

Convergence– Cursorial herbivores

pronghorn, capybara, guanaco, kangaroos

digestive tract, dentition, elongated limbs

Convergent Evolution

• Batesian Mimcry– Benign species

resembles a noxious or dangerous species

Convergent Evolution

• Mullerian Mimicry– Noxious species

resemble each other

Convergent Evolution

• Mullerian Mimicry– Noxious species

resemble each other– Pitohui birds in New

Guinea

Convergent Evolution• Aggressive Mimicry

– Noxious or dangerous species resembles a benign one

Coevolution

Association Effect on Species A

Effect on Species B

Parasitism Positive Negative

Commensalism Positive None

Mutualism Positive Positive

Predation Positive Negative

Competition Negative Negative