Evolution Flashcards
What is evolution
evolution is the change overtime in the proportion of individuals in a population differing in one or more inherited traits
How do change sin allele frequency occur
Through non-random processes of natural selection and sexual selection, and the random process of genetic drift
What does natural selection act on
Acts on genetic variation in populations
What is sexual selection
The non-random process involving the selection of alleles that increase the individuals chances of mating and producing offspring
What could sexual selection lead to
Sexual dimorphism
What can sexual selection be due to
Male-male rivalry and female choice
What is genetic drift
The random increase or decrease in frequency of inherited traits over a number of generations
How does genetic drift occur
Genetic drift occurs when chance events cause unpredictable fluctuations in allele frequencies from one generation to the next
Why is genetic drift more improtant in small populations
As alleles are more likely to be lost from the gene pool
Why is genetic drift important in the bottleneck effect
As a population size is reduced dramatically for at least a generation, causing genetic drift, particularly in alleles not being selected for or against.
What is the importance of founder effects on genetic drift
Where a few members of the population are isolated from the larger population, the gene pool of the new population population is not representative of the original one
What size of population is genetic drift important in and why
Small populations as alleles are most likely to be lost from the gene pool
How can a gene pool be altered by genetic drift
As certain alleles may be under-represented or over-represented and allele frequencies change
What does the Hardy-Weinberg principle state
It states that in the absence of evolutionary influences, alleles and genotype frequencies in a population will remain constant over the generations
What can the Hardy-Weinberg principle be used for
Can determine whether a change in allele frequency is occurring in a population over time
What do changes suggest
Evolution is occurring
What is fitness an indication of
Indication of an individuals ability to be successful at surviving and reproducing
What is natural selection
A non-random process which selects individuals based on their survival chances and therefor increase their chances of passing on their inherited traits
What is sexual selection
The non-random increase in the frequency of alleles that make mating and reproduction more likley
What are the causes of evolution
evolution
Random process Non-random process
Genetic drift. Natural selec/sexual selec
How can fitness be defined
Absolute or relative terms
What is absolute fitness
The ratio between the frequency of individuals of a particular genotype after selection, to those before selection
What is relative fitness
The ratio of the number of surviving offspring per individual of a particular genotype to the number of surviving offspring per individual of the most successful genotype
What can sexual selection be due to
Male-male rivalry and female choice
What are honest signals
Characteristics that allow potential mates to assess the genetic quality or fitness of the males
Sexual dimorphism
Usually males: larger in size, colouration, structures of behaviours
What occurs in some species
Reversed sexual dimorphism
What are selection pressures
The environmental factors tat influence which individuals in a population pass on their alleles
What happens when selection pressures are strong
The rate of evolution will be more rapid
What are biotic selection pressures
Competition
Predation
Disease
Parasitism
What are abiotic selection pressures
Changes in temperature
Light
Humidity
pH or salinity
How do you calculate absolute fitness
AbF = frequency of particular genotype after selec
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Frequency of particular genotype before selec
How do you calculate relative fitness
RF = no. Of surviving offspring per individual of particular genotype
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No. Of surviving offspring per individual of the most successful genotype
What is co-evolution
The process by which two or more species evolve in response to selection pressures imposed by each other
How may species show co-evolution
If there are two species which have frequent or close interactions, they my show co-evolution
What does the red queen hypothesis state
It states that in a co-evolutionary relationship, change in the traits of one species can act as a selection pressure on the other species
What is symbiosis
Symbiosis is the co-evolved intimate relationship between members of two different species
What are the types of symbiotic interactions and the impact of their relationships
-Parasitism
-commensalism
-mutualism
Impacts of them can be positive, negative or neutral for the individuals involved
What impact does a parasitism symbiosis have
+/- symbiosis
What is parasitic symbiosis
When one species (the parasite) benefits in terms of energy or nutrients.
The Other species (the host) is harmed and loses energy and resources
Parasite uses host for growth and reproduction
What impact does commensalism symbiosis have
+/0 symbiosis
0 = neutral
What is a commensalism symbiosis
Commensalism symbiosis is when one species gets a nutritional benefit (the commensal) and the other species (the host) is unaffected
What impact does mutualism symbiosis have
+/+ symbiosis
What is mutualism symbiosis
In mutualistic symbiosis, both species involved are interdependent on each other for resources or other services
Both species benefit —> reuslts in co-evolution generating structural compatibility between mutualistic partners and an exchange of metabolic products occurs
