Macroevolution and population genetics Flashcards
What is symbiosis?
Living together - type of close and long term biological interaction between two different biological organisms.
What happens during symbiosis?
At least one species benefits, relationship for the other species may be positive, negative or neutral.
What is mutualism?
Both species benefit.
What is commensalism?
One species benefits while the other species is not affected.
What is parasitism?
One species benefits while the other species is harmed.
Summarise symbiosis in sloths (mutualism).
Difficult to digest diet, highly digestible lipid rich algae in fur, consume from fur, moths colonise fur, carry nutrients increasing growth, moths to sloth dung, reproduction of moth.
Examples of obligate mutualism symbiosis?
Pollinator-plant mutualisms, frugivore plant mutualisms.
Why do we expect there to be co-evolution between partners of mutualism and parasitism?
Due to 2-way selection, selection is mainly 1-way in case of commensalism.
Why may mutualism lead to co-evolution?
2-way selection resulting in coadaptation such as marriage.
Why may parasitism lead to co-evolution?
2-way selection resulting in counter adaptation such as an arms race.
Describe the fine scale co-evolution: co-speciation.
Host specialties, associated specialist mutualist or parasite does too, tree topologies match, complete co-cladogenesis.
What are reasons for incongruence?
Cospeciation, failure to speciate, duplication, extinction, missing boat, host switching.
What are Hox genes?
In animals, master control genes and conductors of gene orchestra, example of epistasis.
What do Hox genes do?
Involved in embryogenesis, control differentiation along longitudinal body axis in most species, control differentiation of limbs along axis.
Role of Hox genes?
Know whereabouts in body it is, inform builder genes, construct structures like antennae, legs, wings.
Explain the homologous between fly and mouse homeotic genes.
Different nomenclature used for these very similar but not identical, distant ancestors had most or all genes that are now involved in developmental processes.
In what way have some homeotic genes retained their original function?
Gene controlling eye development, human version of gene could theoretically be inserted into fly and still trigger insect eye building.
What is population genetics?
The body of mathematical principles that explain how genetic variation changes in populations over space and time.
What do we need to consider to predict fate of genes over time?
Gene transmission in populations, change of genetic variation.
What will affect the fitness of individuals carrying particular genes?
Characteristics of the population such as gene frequency and population size.
What is a population defined as?
A group of sexually interbreeding individuals.
What are the two important attributes of a population?
Gene allele frequencies = proportion of an allele in a population and gene pool (sum of all alleles within a population).
What causes genetic variation?
Mutations in DNA sequence, recombination, random mating.
What is recombination?
Reshuffling of genes.
What three things can influence the frequency of variation?
Natural selection, migration, genetic drift.
What is natural selection?
Process that modifies the reproductive success of an organism in its natural environment; process through which populations of living organisms adapt to change.
What is migration?
Gain or loss of individuals that make up the gene pool.
What is genetic drift?
Random fluctuations in gene frequencies, small population size.
Where do genes occur?
At definite sites referred to as LOCI.
Characteristics of Loci?
Scattered along chromosomes, carry several variant genes called alleles.
Characteristics of alleles?
One allele of chromosome pair is maternally derived, other copy is paternally inherited.
What does the Hardy-Weinberg principle state?
That alleles and genotype frequencies in a population will remain constant from generation to generation in absence of their evolutionary factors.
Characteristics of HWP?
May include mate choice, mutation, selection, genetic drift, gene flow, describes ideal conditions.
What formula is used to calculate allele frequencies (diploid organisms)?
Allele frequency = frequency (homozygotes) + ½ frequency (heterozygotes).
What is the expected ration of crosses involving dominant and recessive alleles?
3:1
What does the HWP show?
Explains why recessive genes do not disappear over time, in population at eqm both gene and genotype frequencies remain constant from generation to generation.
When are rare recessive phenotypes common?
Carriers present at high frequencies.
Why may we have to rely on phenotypes to calculate frequencies?
In real populations, the genotypes frequencies may not be available.
Can the HWP be applied when there are more than two alleles present at locus?
Yes.
What is sickle cell anaemia?
An interesting genetic disease, normal homozygous individuals have normal blood cells that are easily infected with the malarial parasite.
