8.1 Flashcards
3 factors needed for a population of organisms to evolve are:
Variation
Heredity
Means of selection
What is meant by variation?
there must be differences between the individuals in a population
What is meant by heredity?
The differences between organisms must be heritable
What is meant by means of selection?
must be a mechanism or pressure that selects some variables for the next generation at the expense of others
Genotype is?
The genetic composition of an organism
What 2 factors can both determine phenotype?
Genotype
Environment
2 causes of genetic variation?
Mutation
Sexual recombination
4 factors of mutation for genetic variation:
- Deletion, addition or substitution of nucleotides
- Deletion or translocation of part of a chromosome
- Aneuploidy- loss or gain of whole chromosome set
- Polyploidy - the addition of whole chromosome set
What are the 3 factors for sexual recombination in genetic variation:
- Independent assortment of chromosomes (metaphase) in meiosis
- Crossing over during meiosis (prophase)
- Random fertilisation
What are the 3 factors for environmental variation:
- Organisms can be affected by the environment
- Food availability
- Can evolve to be flexible to environment
In certain environments, individuals that may inherit a mutant allele may be at a selective advantage as they are:
more likely to survive and produce offspring that also carry the mutant allele, this leads to an increase in the frequency of the mutant allele in the population (increasing allele frequency) - population is evolving
Gene pool is defined as:
All the genetic information present within a population at a given time
Gene pool composition changes from one generation to the next as the…
relative proportions of alleles vary
(Gene pool) if there is a consistent change in allele frequency then a population is…
evolving
Allele frequency is:
The number or times an allele occurs within the gene pool
