Main causes of evolution - 7.3 Flashcards
(31 cards)
What is a gene pool?
The combined genetic information of all the members of a particular population.
What are the two types of alleles in a gene pool?
- Dominant alleles
- Recessive alleles
What does homozygous mean?
Having two identical alleles for a given trait.
What does heterozygous mean?
Having two different alleles for a given trait.
What are homozygous lethal traits?
Traits that can be carried by heterozygous individuals and thus remain in a gene pool.
Define relative frequency in genetics.
The number of times an allele occurs in a gene pool compared with the number of times other alleles occur.
What are the two main sources of variation?
- Mutations
- Gene shuffling
What are mutations in genetics?
Changes in DNA sequence that may or may not affect an organism’s fitness.
What is gene shuffling?
The random shuffling of genes caused by sexual reproduction.
What is genetic drift?
In small populations, individuals carrying a particular allele may leave more descendants by chance, causing that allele to become common over time.
What is sexual recombination?
The process contributing to most of the genetic variation in a population.
What is the Hardy-Weinberg Principle?
Genetic equilibrium occurs when allele frequencies remain constant.
List the five conditions necessary for Hardy-Weinberg equilibrium.
- Random mating
- Large population
- No movement in or out of the population
- No mutations
- No natural selection
If one condition for Hardy-Weinberg equilibrium is not met, what does it indicate?
The population is evolving.
In the Hardy-Weinberg equations, what does p represent?
Frequency of the dominant allele (A).
In the Hardy-Weinberg equations, what does q represent?
Frequency of the recessive allele (a).
What are the genotypic frequencies in Hardy-Weinberg equations?
- p² = AA (homozygous dominant)
- 2pq = Aa (heterozygous)
- q² = aa (homozygous recessive)
- p² + 2pq + q² = 1
What is Neutralism in evolution?
The theory that natural selection acts neutrally over many mutant genes, neither favoring nor eliminating them.
What does Punctuated Equilibrium propose?
The rate of evolution is not gradual and continuous, but occurs in ‘jumps’.
What is speciation?
The process by which a population forms a new species that cannot reproduce with the original population.
What is allopatric speciation?
Formation of a new species due to a population being divided by a geographic barrier.
What is sympatric speciation?
Occurs when a species diversifies into sub-populations in the same geographic territory, generating mechanisms that impede breeding.
What are pre-zygotic mechanisms of reproductive isolation?
- Ecological isolation
- Seasonal isolation
- Behavioral isolation
- Mechanical isolation
- Gametic isolation
