Unit 2- Evolution Flashcards
(20 cards)
Describe sexual selection.
Sexual selection is the non random process involving the selection of alleles that increase the chance of mating and producing offspring.
What is sexual dimorphism?
Physical differences between males and females of a species.
What can sexual selection be due to?
Male to male rivalry and female choice.
Describe male to male rivalry.
Larger size or weaponry increases acces to females through conflict.
Describe female choice.
Females asses fitness of male.
Describe genetic drift.
Occurs when chance events cause unpredictable fluctuations in allele frequency from one generation to the next.
Describe the bottleneck effect.
Occur when a population size is reduced for at least one generation causing lower genetic diversity.
Describe the founder effect.
Occurs through the isolation of few members of a population from a larger population. Gene pool of the new is not representative of the original gene pool.
Describe the hardy Weinberg principle.
In the absences of evolutionary influences, allele and genotype frequencies will remain constant over the generations.
What are the conditions for the HW principle?
No natural selection
Random mating
No mutation
Large population size
No gene flow
HW formulas.
p^2 + 2pq + q^2 = 1
p + q = 1
p= frequency of dominant allele
q= frequency of recessive allele
p^2= frequency of homozygous dominant genotype individuals
2pq= frequency of heterozygous genotype
q^2= frequency of homozygous recessive individuals
Describe absolute fitness.
Frequency of a particular genotype after selection / Frequency of a particular genotype before selection.
If the absolute fitness is 1 the frequency of the genotype is stable. >1 means an increase. <1 means a decrease.
Describe relative fitness.
Number of surviving offspring per individual of a particular genotype / Number of surviving offspring per individual of the most successful genotype.
What is co evolution?
The process by which 2 or more species evolve in response to selection pressures imposed by each other.
What is symbiosis?
Co-evolved intimate relationships between members of 2 different species.
What are the types of symbiotic relationships?
Mutualism, commensalism, Parasitism.
Describe mutualism.
Both organisms are independent on each other for resources or services. Both gain (+/+).
Describe commensalism.
Only one of the organisms benefit. (+/0)
Describe parasitism.
The parasite benefits in terms of nutrients or energy and the host is harmed. (+/-).
What is the red queen hypothesis?
In a co-evolutionary relationship, change in the traits of one species can act as a selection pressure on the other species.
So the species must evolve to adapt and avoid extinction.
