VL 5 The power of natural selection Flashcards
How does selection act as a transformative force in evolution on differet levels?
Selection influences:
- Microevolution: Small changes within a species.
- Macroevolution: Large-scale changes that can lead to new species.
- Sexual Selection: Traits that increase mating success.
- Artificial Selection: Human-driven selection for desired traits.
What are the limits of selection?
The optimal genotype might not become fixed due to:
- Genetic Constraints: Issues like heterozygote advantage and pleiotropy.
- Historical Constraints: Traits that were adaptive in the past but are not anymore.
- Ontogenetic Constraints: Developmental limitations that restrict changes.
Pleiotrpy: One gene, two functions. utation is beneficial for one function might be detrimental for the other function
What is altruism, and how is it explained by kin selection?
Altruism is cooperative behavior that decreases the fitness of the actor but increases the fitness of the recipient. Should be selected against, but us frequently found in nature.
Kin selection favors traits that benefit relatives, explained by Hamilton’s rule:
𝑟𝐵 >𝐶,
where 𝑟 is relatedness,
𝐵 is the benefit to the recipient, and
𝐶 is the cost to the actor.
Favored in family-structured populations, with limited dispersal, leading to interacting individuals being related.
Selection against the altruistic individual BUT selection for family groups with altruists!
“With kin selection, it’s the bee hive that becomes better adapted, not the individual bees.” -> Inclusive fitness = direct + indirect fitness.
Extreme form: multicellularity
“I am prepared to lay down my life for eight cousins or two brothers.”
JBS Haldane
What is the Red Queen hypothesis?
The Red Queen hypothesis states that organisms must constantly evolve to keep up with coevolving organisms, such as parasites.
Sexual reproduction creates genetic variation, helping populations adapt to changing environments and escape coevolving pathogens.
Explains why sexual selection, because asexuall selection -> more effective and allel transmission guaranteed
What is the difference between absolute fitness and relative fitness and inclusive fitness?
Absolute fitness: Total reproductive success of an individual.
Relative fitness: Performance of a genotype relative to others, with the highest value set to 1.
Inclusive fitness: Sum of an individual’s direct and indirect fitness components.
- Direct fitness: own surviving offspring.
- Indirect fitness: surviving offspring of genetic relatives due to altruistic behavior, weighted by degree of relatedness.
What are genetic constraints in selection?
- Heterozygote advantage: Heterozygotes cannot produce only heterozygotes.
- Pleiotropy: One gene affects multiple traits; a mutation beneficial for one trait may be detrimental for another.
- Heterozygote disadvantage: A beneficial mutation cannot spread to fixation if heterozygotes have lower fitness.
What are historical constraints in selection?
Traits that were adaptive in a past environment may no longer be beneficial, such as plants with seemingly maladaptive seed traits that were once advantageous.
e.g. avocado with huge seeds (megafauna adaption)
What are ontogenetic constraints in selection?
Ontogenic constraints in selection, as illustrated by the example of flatfish like the halibut, highlight how an organism’s developmental pathway and resulting morphology can restrict the range of possible evolutionary adaptations available to it.
-> mutation that would bring more speed for example, but is interferring with the migration of one eye to the other side will be a bigger decraese in fitness than increase
What is punctuated equilibrium?
A theory proposed by Eldredge and Gould that suggests evolutionary change occurs in bursts, leading to speciation, rather than gradually over time.
What is the paradox of sex?
Asexual reproduction is more effective in increasing population size and guaranteeing allele transmission, yet sexual reproduction is common due to its benefits in creating genetic variation and adaptation.
What is the role of phenotypic plasticity in evolution?
Phenotypic plasticity is a powerful mechanism that influences the evolutionary trajectory of organisms by enhancing their ability to respond to environmental challenges and opportunities. It interacts closely with genetic evolution, shaping how populations adapt and diversify in a dynamic world.
What is mutualistic coevolution?
A process where two species evolve reciprocal adaptations that benefit both, such as plants and their pollinators or ants and fungi.
What is the difference between mutualists and enemies in coevolution?
Mutualists: Species that benefit from each other through reciprocal adaptations.
Enemies: Species that interact antagonistically, such as herbivores and plants, or predators and prey, leading to evolutionary arms races.
