Evolution And Natrual Selection Flashcards
(27 cards)
Why are sickle cells an example of overdominance
The sickle cell allele for haemoglobin gives resistance against malaria in heterozygotes but in the case of homozygotes it causes sickle cell disease. Only heterozygotes are fitter but natural selection does not get rid of the gene as it makes people resistant to malaria in poorer regions
What is ‘hitchhiking’
Genes that are on a similar loci on a chromosome are unlikely to be split so if one of them provides a benefit it is likely the other will also be inherited and selected
What is the importance of phenotype and genes in natural selection
Genes are used as an inheritable characteristic but phenotypes is what is selected for not genes
What is sexual selection
Generally female choice leads to the women selecting mates so in the case of some animals characters may seem like they reduce fitness but actually lead to better reproductive success
How do sequences of DNA move in genome and what is it called
Transposons move due to the RNA the DNA produces will be reverse transcribed back into DNA then is inserted into the genome.
Why are transposons relevant to natural selection
Transposons lead to mutations which may make some genes slightly more or less effective relative to their location relative to promoter regions. This could affect fitness.
What adaptation do fish living in polar seas have
Anti-freeze glycoproteins
How are retroviruses relevant to the evolution of animals
Endogenous retroviruses that have infected humans in the past have since been incorporated into the human genome and has changed over time e.g. the placenta in mammals.
What is horizontal gene transfer
The transfer of genetic information without sexual reproduction. For example it could be a virus infection or from bacteria that is then integrated into nuclear DNA
How are Pea aphids an example of horizontal gene transfer
Acquired the gene for carotenoid synthesis from fungus and helps with predatory avoidance due to some food being red.
What is eDNA and it’s uses in observation
It stands for environmental DNA which is helpful as it is non invasive as it is extracted from soil, water and sometimes air. It can be amplified then identified to give insight into the ecology of the animals living in the area.
What is altruism
The behaviour of an animal that benefits another at its own expense
What is inclusive fitness (kin selection)
A additive product of both direct fitness and the indirect fitness which is the fitness of related offspring that are also capable of passing on the characteristics
What is hamilton’s rule
Altruism has a cost to the individual and this cost must be outweighed by the benefit to the recipient multiplied by the relatedness.
What is Haplodiploidy
Species with a diploid female and a haploid male
What does haplodiploidy mean for a species and reproduction
Two sisters are more closely related to each other than they are to offspring therefore due to hamilton’s rule it makes more sense for altruism to occur between sisters than direct offspring..
What is allopatric speciation
Separation due to geographical barrier e.g. squirrels either side of the Grand Canyon leading to speciation
What are the different types of selection
Directional - selects to one extreme
Disruptive - selects to both extremes (can cause speciation)
Stabilising - selects towards the mean, against extremes
What is genetic drift
Especially in small populations major changes can occur due to random effects
What is founder effects and bottlenecks
When a bottleneck event occurs only a small population survives so genetic diversity decreases and the new founding population is less diverse .
What is sympathetic speciation
Speciation occurring between two groups that aren’t separated geographically
What can cause sympatric speciation in animals (Blackcaps)
In blackcaps they migrate from from Germany to the UK OR Spain in winter. Spanish and UK birds arrive back in Germany at different times so they became reproductively isolated. They still reside in the same area but strong genetic and morphological differences have arrived from temporal isolation.
How can sympatric speciation occur in plants
In the event of polyploid events occurring due to failed meiosis making diploid gametes an offspring could be produced with more chromosomes. If this offspring is fertile it may be genetically isolated and therefore become a new species.
Why is speciation not an adaptation
Speciation is an event caused by particular conditions, so it is merely a by-product of chance combined with potentially selections (not always e.g. polyploidy or bottlenecks)
