Gentic Diversity Natural Selection Flashcards
(14 cards)
Define genetic diversity
Total number of alleles in a population
Define population
Group of individuals of the same species that live in the same place that can interbreed
What causes genetic diversity to be low
When species have fewer different alleles as if genes are similar they can resits the same environmental change and one change will effect whole species
What enables natural selection to occur
Genetic diversity- the larger number of alleles the more likely individuals will have characteristics suited to environment to survive change
Natural selection process
-in population of species there is a gene pool containing wide variety if alleles
-mutation of alleles within pool may result in new alleles (most mutations are harmful)
-in certain environments new allele of gene may give possessor advantage over individuals of pop
-these individuals will adapt better more likely survive in competition and obtain Available resources
-have better chance of breeding successfully and producing offspring
-and passing alleles to next generation
-over many generations num of individuals with advantageous allele increases at expense of those with out this.
Over time frequency of advantageous allele increases with that of non advantageous deacreases
What is directional selection
Selection may favour characteristics that vary in one direction from the mean population , it goes towards an extreme
On our bell curve the mean mode median will shift in one direction
Example of how directional selection causes bacteria to be resistant to antibiotics over time
There is variation in the bacterial population due to random mutations. Some bacteria happen to have a mutation that gives them resistance to the antibiotic. When the antibiotic is used, it kills the non-resistant bacteria, while the resistant ones survive and reproduce. The resistance allele is passed on to the next generation. Over time, the frequency of the resistance allele increases, shifting the population in that direction. This is directional selection because one extreme phenotype is being selected for
Define Stabilising selection
In stabilising selection, individuals with phenotypes closest to the mean are more likely to survive and reproduce. Extreme phenotypes are selected against. As a result, the average phenotype is maintained and variation within the population is reduced.this preserves characteristics of a population
Mean median mode stays centered
Explain how stabilising selection could influence the birth weight of human babies in a population.
In human populations, babies with very low or very high birth weights have a lower chance of survival. Low birth weight babies may be underdeveloped, and high birth weight babies may lead to complications during birth. Therefore, babies with an average birth weight are more likely to survive and reproduce. Over time, alleles for extreme birth weights decrease in frequency, and the population maintains a stable average birth weight. This is stabilising selection, as it selects against extremes and favours the mean
Do bacteria mutate due to the presence if antibiotic
No mutations are random
Mutations are usually harmful
What is anatomical adaptation
Physical features -like thick fur or short ears
Physiological adaptations
Internal body processes like producing venom
Behavioural adaptation
Actions , such as migration or hibernation
What does measuring the index of diversity take into account
Species richness - amount of species in an area
Species evenness-how evenly species are disturbed among species
IF HIGH
Many different species
Even distribution (no single species dominates)
Stable ecosystem
