Adaptation Flashcards
What is Futuyma’s description of adaptation?
Characteristic that enhances the survival or reproduction of organisms that bear it, relative alternative character states
What is the historical definition of adaptation?
Derived character evolved in response to a specific selective agent
What is the ahistorical definition of adaptation?
Phenotypic variant resulting in highest fitness among a specified set of variants in a given environment
What three things are needed for adaptation to occur?
Variation in phenotypic traits, fitness differences between different phenotypes, variation in traits have to be heritable.
What happened between 1976-1978 that Peter and Rosemary Grant observed?
Severe drought, vegetation death, 90 survivors, beak depth average size 0.5mm deeper than before.
What was the shift driven by?
Selection by loss of food resources as the only food left were very tough seeds and only strongest beaks able to utilise them
What happens if a mutation creates an advantageous allele?
Shift from low frequency to high frequency, becomes polymorphic
What happens if a mutation is disadvantageous?
Selected out, mutation-selection-balance, continual input of mutation, continually selected out
What are the two types of balanced selection?
Heterozygote advantage and frequency dependent
What is heterozygote advantage?
When the heterozygote has higher fitness compared to homozygote, will go to equilibrium and variation is maintained (sickle cell anaemia in malaria prevalent areas)
What is frequency dependent selection?
Fitness depends on frequency (genes associated with host parasitic interactions, fitness for rare allele because parasite won’t be adapted)
How did Darwin say eye might develop?
Through small steps
What did Paley say regarding eyes?
Evidence for god
What did Dawkins say regarding eyes?
Blind watchmaker, evolved without any foresight just driven by natural selection
How many steps did it take to go from a small patch of cells with light sensing capability to a small concave dish?
362 steps
What are the further steps for eye development?
Small concave dish, deeper pit, smaller and smaller aperture like a pinhole camera. Light forms semi resolved image on back surface. Optical properties of liquid inside pit make a higher resolution image.
How many years to make a complex eye?
364,000
What sort of eye does the Nautilus mollusc have?
Pinhole camera eye
What animal shares a similar hearing mechanism to us?
Katydids (bush cricket)
How do we hear?
External membrane where sound vibrations are transferred by a physical structure into an internal structure. A fluid filled medium is there and is filled with mechanical receptor cells (hair cells).
Describe what happened with Atlantic Killifish?
Can persist in unusually toxic environments filled with PHA’s and PCA’s. An experiment involved taking sample populations from a non toxic environment and a toxic one and sequencing and comparing the genomes. Found that those in the toxic environment had the same genes involved in the metabolism of organic contaminants which allowed them to persist in polluted environments.
Why did they adapt so quickly?
Because they have a large population size with high levels of genetic diversity, likely that already have the genetic variant that makes them adapted to the environment so can readily respond to the selection pressure.
What did Gould and Lewontin say regarding adaptation?
Spandrels! Not everything has to have an adaptive explanation
What are three examples of evolutionary spandrels?
Blood colour, due to Hb, doesn’t give any sort of fitness. Size of T.rex arms, when driving size increase arms didn’t increase proportionally. Pandas have useless projections on their feet with similar morphology to the ones on their hands they use to shear off bamboo, but they don’t use their feet to eat, so useless?
