Lecture 10: Natural Selection Flashcards
non-adaptive mechanisms of evolution (3)
- Genetic drift
- Migration
- Mutation
an adaptive mechanism of evolution
Natural Selection
What was Darwin’s contribution regarding population speciation?
Natural selection driving population speciation.
Why do organisms produce too many offspring?
To increase chances of survival in competitive environments.
What causes limited resources and competition in populations?
Scarce environmental resources lead to competition among individuals.
What is the significance of variation in a population?
It provides the raw material for natural selection to act upon.
How do better-adapted individuals fare in natural selection?
They are more likely to survive and reproduce.
What happens to the average character of a population over time due to natural selection?
It changes as better-adapted traits become more prevalent.
What does natural selection entail?
Differential survival and reproduction of genetically-based traits.
What determines the fitness of different phenotypes in natural selection?
Their suitability to the environment and their heritability.
Natural selection leads to __, NOT random, but __
- adaptation
- deterministic (favoring traits best suited to the environment)
What distinguishes traits subject to natural selection from plastic phenotypes?
Genetically-based inheritance, rather than environmental influence.
Traits subject to natural selection are distinguished from __ __ primarily by their mode of inheritance. Traits subject to natural selection are primarily determined by __-__ __.
- plastic phenotypes
- genetically-based inheritance
important factor in natural selection
fitness
An organism’s ability to survive and reproduce in a particular environment
Fitness
Higher fitness means that greater numbers of __ survive in the next generation
offspring
What happens when mutations arise in the reverse transcriptase gene of HIV?
The enzyme gains the ability to recognize and evade the effects of AZT.
How do drugs like AZT (Azidothymidine) impose selection on viruses?
They create pressure favoring mutations that confer resistance.
What role does genetic variation play in the evolution of drug resistance in viruses?
It allows the virus to respond to selection pressures by generating mutations that confer resistance.
How does natural selection act in the presence of AZT?
It favors the survival and reproduction of HIV variants that can resist the effects of the drug.
How can the direction of selection affect the evolution of virulence?
It can change with shifts in the environment.
Phenomenon: Traits that enhance a pathogen’s fitness in one environment or under certain conditions may be disadvantageous in others, leading to shifts in the direction of selection.
Evolutionary tradeoffs
Selection imposed by Transmission Rate on Virulence of HIV
Explain the evolutionary tradeoff: Need to keep host alive long enough to get passed on to the next host
Evolutionary tradeoff between fast population growth and keeping the host alive
High Transmission rate : __ __
High Virulence