Fitness Flashcards
• Definition of ‘fitness’ • Example of sickle-cell anaemia and heterozygote advantage • ‘Levels of selection’ debate and solutions • Sexual selection • Why altruism appears a problem for evolutionary biology • Why it isn’t • Hamilton’s rule and criticisms • Example of sociality in social insects
What is ‘fitness’?
The relative probability of SURVIVAL and REPRODUCTION of a given genotype.
Who are the ‘fit’?
Depends on probability of survival and reproduction which both vary according to environmental conditions. It also doesn’t just depend on possession of an allele, it depends on no. of copies of an allele.
Why does the sickle cell trait still exist?
HETEROZYGOUS FITNESS
A single copy of the sickle cell allele increases malarial resistance, so heterozygotes are fitter.
What is the definition of evolution?
A change in allele frequencies of a population over time.
Why are genotypes and phenotypes not directly linked?
Because:
1). Phenotypes may be affected by multiple genes
2). Genes may be linked together so frequencies of ‘useless’ genes physically close to selected genes may increase due to hitchhiking.
Therefore, changes in allele frequency may not be expressed in the phenotype.
What is selected?
Selection operates on individuals in a population who express phenotypes. These individuals interact and express their genotypes differentially. SPECIES ARE NOT SELECTED.
When is there a possibility of evolution in a population?
Where their phenotypes are at least partly determined by genes, there is a possibility for evolution.
