Unit 2 Flashcards
What is evolution
Evolution is the change over time in the proportion of individuals in a population differing in one or more inherited traits
What is evolution
Evolution is the change over time in the proportion of individuals in a population differing in one or more inherited traits
What is selection pressures?
Environmental conditions that can influence which individuals in a population can pass on their alleles
What are biotic factors? Give 4 examples?
Living factors - eg. Competition, predation, disease and parasitism
What are Abiotic factors? Give 4 examples?
Non-living factors - eg. Changes in temperature, light, humidity, pH and salinity
What are the two types of evolution?
Random and non-random
What is an example of random evolution?
Genetic Drift
What is Non-random evolution influenced by?
Selection pressures, and the traits that are selected by these pressures
Give 2 examples of non-random evolution?
Natural selection and sexual selection
What is variation within a population a result of?
Mutations
What are mutations?
The original source of new DNA sequences, which can result in novel alleles
Natural selection timeline.
- populations always produce more offspring than the environment can support.
- variation exists within the species (due to different mutations)
- Organisms struggle for survival and are influenced by selection pressures like competition and predation
- those organisms best suited to the environment survive as they have a selective advantage. Those organisms less suited due off. This process is called natural selection (or survival of the fittest)
- The surviving organisms mate, reproduce and pass on useful allelesthat conferred an advantage to the next generation
What do selection pressures influence?
The traits in a population based on if they confer a selective advantage or not in that particular environment
What is sexual selection?
A form of natural selection, where the increase in allele frequency is determined through the selection of mating partners.
What does the selection for mates lead to?
Extreme physical (or behavioural) adaptations to attract mates - this can cause sexual dimorphism in males and females
What are the two sub-categories of sexual selection?
Male-male rivalry and Female choice
What is male-male rivalry? Give an example?
Large size or weaponry increases access to females through conflict. An example being stags and deer.
What is female choice? Give an example?
Female choice involves females assessing the fitness of males. An example being peacocks and peahens
What is genetic Drift?
Genetic Drift leads for variation in the relative frequency of different genotypes in a population, when chance events cause unpredictable fluctuations in allele frequencies from one generation to the next.
Certain alleles can be under represented, others over-represented
What populations are particularly at risk of losing alleles due to genetic Drift?
Small populations
What is a population bottleneck?
An event that drastically reduces the size of a population for at least one generation
What is a population bottleneck caused by?
Environmental disaster, overhunting or habitat destruction
What is the effect of a population bottleneck?
Reduce the gene pool as many allele types are lost, this leaves a population with a much reduced diversity
What is the founder affect?
The founder effect occurs through the isolation of a few members of a population from a larger population.
What happens to the gene pool of a new population after the founder effect?
It’s not representative of that in the original gene pool
What does the Hardy-Wienberg principle state?
In the absence of evolutionary influences, allele and genotype frequencies in a population will remain constant over the generations
What 5 conditions must be met for the HW principle to apply?
No selection, no mutation, no migration, a large population and random mating
Name the 2 Hardy-Wienberg equations?
p + q = 1
p² + 2pq + q² = 1.0
What does all the letters in the 2 Hardy-Wienberg equations stand for ? (p + q = 1 and p² + 2pq + q² = 1.0)
p = frequency of dominant allele
q = frequency of recessive allele
p² = frequency of homozygous dominant genotype
2pq = frequency of heterozygous genotype
q² = frequency of homozygous recessive geneotype
What is fitness?
The measure of the tendency of some organisms to produce more surviving offspring than competing members of the same species.
What two terms is fitness defined by?
Absolute or relative terms
What happens to alleles with the highest fitness?
They would become more common in a population.
What is the overall fitness of an individual affected by?
It’s enviroment
The fitness of a phenotype and genotype will differ where?
Different environments
What is absolute fitness?
The ratio between the frequencies of individuals of a particular genotype after selection, to those before selection (from one generation to the next)
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 (from one genotype to the next)
What is coevolution?
The process by which two or more species evolve in response to selection pressures imposed by each other.
A change in the traits of one species acts as what?
A selection pressure on the other species
Give 4 examples of co-evolutions?
Herbivores and plants, pollinators and plants, predators and prey and parasites and hosts
What is symbiotic interactions?
Co-evolved intimate relationships between members of two different species.
What is mutualism?
Both organisms in the interaction are independent on eachother for resources or other services. Both organisms gain something from the relationships - shown as (+/+)
What is commensalism?
Only one of the organisms benefits but the interaction doesn’t negatively affect the other organism. This interaction can be shown as (+/0)
What is parasitism?
The parasite benefits in terms of energy or nutrients and the host is harmed as the result of the loss of these resources. This interaction can be shown as (+/-)
What does the red queen hypothesis state?
In a co-evolutionary relationship, change in the traits of one species can act as a selection pressure on the other species
What does the red queen hypothesis mean?
Species in these relationships must adapt to avoid extinction. Both organisms must “keep running in order to stay still”
