Lecture 4: Evolutionary Ecology Flashcards
What is evolution?
- Descent with Modification
- Allele Frequency Change
- Populations evolve, individuals do not
Descent with Modification
Fossils: show descent with modification (In terms of teeth and limbs)
- Species do change
Ex: stickleback fish, horses, and dinosaurs being extinct
Allele Frequency Change
- allele frequency changes within a population
- Populations of organisms we do see variation within them
- If there is strong selection on a population, we will see genotype changes
Ex. Animals relying on camouflage – if they are wrong colour, will be selected against
- pocket mice
What are the Mechanisms of Evolution
- Mutation
- Natural Selection
- Genetic Drift
- Gene Flow
Mutation example
-Ex. Elephants utilize their tusks for manipulating their ecology
-To get their tusks, they just slaughter the elephants, take off their faces, and leave the body to rot
-Mutation produces tuskless elephants
Mutation definition
-a change in DNA
-Can result from copying errors during cell division, mechanical damage, exposure to chemicals (mutagens) or high-energy radiation
-Very rare
-Provides the raw material on which evolution is based, while recombination and independent assortment rearrange the raw material into new combinations
Natural Selection example
-beaks of birds
-Finches have massive bills used for cracking seeds
3 Types of Natural Selection
- Directional Selection
- Stabilizing Selection
- Disruptive Selection
Directional Selection
-individuals at one phenotypic extreme are favoured
-Ex. large size
-Ex. the finches
Stabilizing Selection
-individuals with an intermediate phenotype are favoured
-occurs if there is 2 selective agents operating on both sides of the curve
-Ex. 2 predators and the gall
Disruptive Selection
- individuals at both phenotypic extremes are favoured
Genetic Drift
- Occurs when chance events determine which alleles are passed to the next generation
- Significant only for small populations
- Loss of alleles
- Loss of genetic variability
- Easier to go extinct
Adaptive Evolution can Occur Rapidly
- Male bighorn sheep that are bigger with a bigger horn will win the battle
- Have been losing land (habitat has been deteriorating)
- They will continue to be hunted- even tho hunters must pay $100,000
Adaptations are not Perfect
-Natural selection does not result in a perfect match between organisms and their environments
-Environments are constantly changing, and there are constraints on evolution
Lack of genetic variation
- Spraying with DDT killed populations of mosquitoes carrying malaria
- Killed off any form of mutations
Evolutionary History
-Whales perfect example of evolutionary history
-Evolutionary Constraint: Whales always need to return to the surface to breathe
Ecological Trade- offs
Crab: Decreased mobility due to size
Snow Crabs - claws are small but legs are long trying to get away from predators
Adaptive Evolution is Driven by Ecological Interactions
-Organisms interacting with one another and with their environment
-For every fox that caught a bunny, one fox went hungry
-Evolution is constantly in motion, and the ecological context is under constant change
Long-term patterns of evolution are shaped by large-scale patterns
a. Speciation
b. Adaptive radiation
c. Extinction
d. Mass extinction
What Drives Speciation in a Single Population
-Change in gene frequency
-There is gene flow between white mice and dark mice
-But overtime a river continues to grow between the two
-At this particular point, no gene flow would be able to occur
-This would cause the formation of 2 separate daughter species (since gene flow isn’t occurring)
Species Concept Definition
-Those individuals in the population must be able to have offspring, and those offspring should be fertile
Physical Barriers that Result in Reproductive Isolation and Speciation
- Physical Barrier
- Mutualism (behaviour)
- Ecological Barrier
