Environmental selection pressures Flashcards
environmental seleciton pressures
environmental selection pressures are selection pressures that influence the survivability of a species within a given environment eg. compeittion, predation, disease, climate change
What factors allow for the process of naturla seleciton
compeitition, predation, disease and climate chnage
Natural selection
natural selection is a mechanism for evolution in which the individuals best adapted to the selection pressures in their enviornment survive and pass on their alleles to their offspring.
What does it mean when a phenotype has a higher fitness value and is “at a selective advantage”?
A phenotype with a higher fitness value contributes more to the gene pool in the next generation, meaning it is more likely to survive and reproduce. This selective advantage allows favorable genes to be passed on to future generations.
What happens to a phenotype with a lower fitness value in terms of natural selection?
A phenotype with a lower fitness value makes a lesser contribution to the gene pool in the next generation and is said to be “selected against,” meaning it is less likely to survive and reproduce, leading to a decrease in its frequency over time.
The four conditions of Natural Selection
- variation (physical, biochemical, behavioural) in phenotypes within a population which is heritable.
2.A selection pressure exists that causes a struggle for survival in some individuals.
3.Organisms with a favourable phenotype will be selected for and have a selective advantage that helps them overcome the selection pressure. The unfavoured phenotype is selected against and their numbers are reduced in the gene pool.
4.Those with the favourable phenotype pass their alleles to their offspring and inherit these traits. The frequency of the favourable allele increases.
Natural Selection in peppered moths
1.There is variation in phenotypes within a population Light and dark coloured moths
2.A selection pressure exists (predation from birds) that causes a struggle for survival in some individuals.
3.Organisms with a favourable phenotype (dark moths in dark environments) will be selected for and have an advantageous phonotype that helps them overcome the selection pressure. The unfavoured phenotype (light coloured moths in dark environment) is selected against and their numbers are reduced in the gene pool.
4.Those with the favourable phenotype pass their alleles to their offspring. The frequency of the favourable allele increases.
How do environmental selection pressures influence the adaptation of a population through natural selection?
Environmental selection pressures determine which phenotypes are considered fitter and more advantageous, allowing them to pass on their favorable traits to their offspring. This leads to an increase in the allele frequency of favorable traits and alters genetic diversity by increasing favorable alleles and decreasing less favorable ones.
Natural selection in mice
1, variation exists within a population of mice
2,the fox acts as a selection pressure
- selective advatnage is conferred upon the grey mice
4.the grey mice will have an increased chance of surviving and reproducing, allowing them to pass on their advantageious alleles ot the next generation
Explain the process of natural selection that has occurred in the population of southern blue mussels over the last 15 years that has resulted in thicker shells. (3 marks)
Assume that the Asian shore crab is unable to migrate past the northern limit line into the northern blue mussel area. What would you expect to happen to the shell thickness of the northern blue mussels over time? Explain your reasoning. (2 marks)
