Limits of Adaptation Flashcards
What determines the phenotype of an individual?
Phenotype is a function of genetics (including additive genetic effects, dominance effects, and interaction effects) and environment.
What are proximal processes that influence traits?
Proximal processes include genes, gene interactions, environment, gene-environment interactions, and present evolutionary processes like drift and mutation.
What are historical processes that influence traits?
Historical processes include past evolutionary events or lineage history.
Why are traits often imperfect?
Traits can be by-products of other processes (e.g., the red color of blood due to iron), vestigial (e.g., human appendix, coccyx), or constrained by evolutionary history.
Give an example of a vestigial trait and explain its origin.
The human coccyx (tailbone) is vestigial; it is a remnant of a tail present in our tetrapod ancestors.
What are the two ways to think about adaptation?
Adaptation can refer to:
A process of evolution resulting in better survival/reproduction.
A trait or set of traits that evolved through natural selection for a specific function.
What is the difference between “an adaptation” and “adaptation”?
“An adaptation” is a specific trait evolved for a purpose, while “adaptation” refers to the evolutionary process itself.
What is exaptation?
Exaptation is when a trait that originally evolved for one purpose is later coopted for a different function, such as feathers initially for insulation being used for flight.
What evidence is needed to show a trait is maintained by natural selection?
vidence includes:
Variation in the trait within the population.
Heritability of the trait.
Functional relevance to a selective mechanism.
Measurable effects on survival or reproduction.
Why should we be cautious when interpreting traits as adaptations?
A trait might:
Be an adaptation but not for the stated function.
Not be an adaptation at all (e.g., due to ancestral constraints or trade-offs).
How do ancestral constraints limit adaptation?
Traits inherited from ancestors can be difficult to change and may limit future adaptations, like the crossing of food and air pathways in humans.
What is an adaptive landscape?
It is a conceptual model where each phenotype corresponds to fitness, represented as elevation; natural selection moves populations to adaptive peaks.
Why can populations get stuck on suboptimal adaptive peaks?
Moving to a higher peak requires crossing an adaptive valley (maladaptive intermediates), which selection often avoids.
How can a population cross an adaptive valley?
Through genetic drift in small populations or changes in the environment temporarily raising the valley.
What are trade-offs in evolutionary biology?
Trade-offs occur because resources are finite, forcing organisms to allocate them between competing needs like reproduction, longevity, or seed size.
