Lecture 4- Chapter 6: Flashcards
Georges Cuvier
- came before Darwin
- discovered extinction in 1813
- extinction was a wild notion
Carl
- father of taxonomy
- made thousands of species
- coined the term homosapiens
- christian
- believed he was doing God’s work
Charles Darwin
- 1859: The Origin of Species
- used the phrase “descent with modification”
- natural selection (ex in book include hunting of bog horn sheep and cod fisheries)
What is Evolution (3 points)
- 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. Arizona desert white sand mostly certain mice want to be cryptic from their predators so they are less visible than other mice within the population
Ecology Definition
- the interaction between organisms
Populations Evolve, Individuals Do Not
- evolution never follows over evolutionary time
What are the Mechanisms of Evolution
- Mutation
- Natural Selection
- Genetic Drift
- Gene Flow
Mechanism of Evolution 1. Mutation
-Individuals in populations differ in their phenotypes
-Different alleles arise by mutation
-Ex. Elephants utilize their tusks for manipulating their ecology
-Recently, poaching has been very popular in places where they live
-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
Mechanism of Evolution 2. Natural Selection
-beaks of birds
-Finches have massive bills used for cracking seeds
3 Types of Natural Selection
- Directional Selection
- Stabalizing Selection
- Disruptive Selection
Directional Selection
-individuals at one phenotypic extreme are favoured
-Ex. large size
-Ex. the finches
Stabalizing 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
Natural selection is the Mechanism of Adaptive Evolution
- What is Adaptive Evolution
- Adaptations results from natural selection
- Adaptive Evolution can Occur Rapidly
- Adaptations are not perfect
Mechanism of Natural Selection 4. Gene Flow
-alleles move between populations via movement of individuals or gametes
-this causes:
1. Populations to become more similar
2. New alleles can be introduced into a population
-Ex. gene flow introducing alleles for insecticide resistance
Key Conceot 3: Natural Selection is the Mechanism of Adaptive Evolution
- What is adaptive Evolution
- Adaptations result from natural slection
- Adaptive evolution can occur rapidly
- Adaptations are not perfect
Adaptations Results from Natural Selection
-Selects of traits that confer advantages
-alleles increase in frequency over time
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
Why Evolution isn’t Perfect
- lack of genetic variation
- evolutionary history
- ecological trade-offs
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 Ecolution 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
Key Concept 4: 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
George Cuvier
- discovered extinction
- Over evolutionary time we have rates of extinction and speciation
Adaptive Radiation Definition
- Repeated speciation events increases the number of speciation in a group
Extinction Definition
- species are also lost
An Evolutionary Tree Definiton
- a branching diagram that represents the evolutionary history of a group
Extant Definition
- is the opposite of extinct (means they are alive today)
What does the Cambrian Explosion mean?
- adaptive radiation in animals
Key Concept 5: Ecological Interactions and Evolution Exert a Profound Influence on one Another
Evolution observed patterns of change
- Bacteria and archaea
- Multicellular life - red algae
- Animal life
