Adaptations Flashcards
What is an example of an evolutionary anachronism?
Many neotropical plants with large, tough seeds are not adapted for seed dispersal now because they relied on large herbivore dispersers that are now extinct
How can adaptation be a part of sexual selection?
Mate attraction or competition. Adaptations to draw in a mate or to fight to get access to mates
What data supports the human eye being a complex adaptation?
Computer simulation showed it took 400,000 generations for an eye to evolve to a complex vertebrate eye
Linkage among traits
Pleiotropy
What is poor design evidence of?
Natural selection
What is an example of a genetic constraint to adaptation?
Heterozygote advantage
Things from a different time that existed due to selective pressures then that don’t exist now
Evolutionary anachronisms
How are adaptation, fitness, and natural selection related?
All three are linked to each other
Why is it not advantageous to get rid of vestigial structures?
Flightless bird wings are a good example. Getting rid of the wings gets rids of the genes and getting rid of the genes is a bad idea
What is needed to show a correlation is an adaptation?
Fitness data is needed to support it
What is the only known explanation for adaptations?
Natural selection. Natural selection leads to adaptations
Share the same development patterns but are modified for specific species through selection
Homologous structures
Are complex adaptations related to the best solution?
No. Complex doesn’t mean best and simple doesn’t mean worst
Feeding specializations and crypsis (allowing organisms to blend in) are examples of what?
Adaptations (noun)
Can individuals adapt?
No
What are adaptations the result of?
They are the result of evolution by natural selection
Why do developmental constraints exist for adaptations?
Certain morphologies are impossible developmentally
What are products of convergent evolution?
Analogous structures
An existing structure modified to serve a new function
Preadaptation
What do trade offs lead to?
Stabilizing selection. Finding the balance between what you’re selecting for and the other function compromised as a result
What can a significant shift in phenotype cause for an organism?
It could push the organism off and over the adaptive peak
Example of a trade off
Longer legs = faster but more fragile bones
How is poor design proof of selection?
Mutation is random and selection can only act on what exists so if the mutation is poor but functional, selection will still act on it
Something is this if it scales with size
Allometry
Adaptation for one function may compromise another function
Trade offs
The process by which features that enhance fitness are fixed in a population or species
Adaptation (verb)
What happens when you go up a peak (“decide” on a solution) in the fitness landscape?
You cant go back down to get to an optimal peak, you are stuck with the one you have
Functionally similar but structurally and historically different. Have independent evolutionary origins
Analogous structures
Why is it difficult to determine what selection has selected for, thus making it hard to determine whether something is an adaptation?
Linkage of traits (pleiotropy) and passage of time
What is heterozygote advantage?
The form with the highest fitness cant breed true. A heterozygote crossed with a heterozygote doesn’t produce all high fitness heterozygotes, it produces 50% homozygotes that are lower in fitness
Valleys in the fitness landscape represent this
Low fitness
What are two types of constraint to adaptation?
Genetic and developmental
When are adaptations most apparent?
Most apparent from comparisons of related species specialized for different niches
What is an example of poor design in humans but selection still acting on it?
The eye. The blind spot and having muscles stretch to focus are not optimal. The male urogenital system also is not optimal.
Way of visualizing adaptations in potential solutions
Fitness landscape
An adaptation that has arisen via preadaptation
Exaptation
What makes adaptation unique from usually occurring selective evolution?
Adaptation occurs gradually with directional selection over several generations
These two are the effects of differences in fitness
Differential reproductive success and survival
What two things must be present for something to be considered an adaptation?
- Improve fitness such that organisms with the trait have higher fitness than those without (all other things being equal)
- Show correlation between the presence of the feature and the hypothesized selective pressure (ex: larger beaks survive food shortage from drought)
Structures with little or no current function but are retained due to common ancestry
Vestigial structures
Peaks in the fitness landscape represent this
High fitness
Specialized features that enhance fitness
Adaptations (noun)
How does selection act in an adaptive landscape?
Selection cant look across the landscape and choose the path to the highest peak. Selection operates on existing variation and chooses the local peak, it probably won’t cross a non-adaptive valley
What can be products of divergent evolution?
Homologous structures
How does adaptation occur over time?
It is usually gradual. Slight adjustments over multiple generations
What is an example of a developmental constraint to adaptation?
Allometry. Animals with antlers, selection exists for large body size but large body size comes with large antlers which are unfavorable (neck cant support it) so it is against it
Structurally similar but can be functionally different. Have evolutionary shared ancestry
Homologous structures
What is an example of convergent evolution in cave dwelling animals? How does this occur?
Loss of sight and pigmentation is the convergent evolution. This occurs due to the absence of selective pressures for these things
