5.2 Natural Selection

Question 1

what is variation

Answer 1

this is differences characteristics between organisms and it is key to natural selection as natural selection is based on variation

if there was no variation all individuals would be identical as there would no way to favour organisms with beneficial characteristics

Question 2

what are the sources of variation

Answer 2

1. mutatations - changes in DNA leads to new alleles being created - enlarges gene pool of the population
2. meiosis - during gamete production the genetic material is mixed up due to crossing over adn independent bivalent orientation so that each sperm and egg cell has a different combination of DNA
3. sexual reproduction - fusion of male and female gametes during fertilization results i offsprinf with geneti cmaterial form both mom and dad

for organisms that do asexual reproduction teh only source of variation is mutation (disadvantage)

Question 3

what are adaptations

Answer 3

characteristics that make an organism suited to its environement and increase its chance of survival

e.g. polar bear thick fur

these develop over millions of years at a species level

Question 4

what are acquired characteristics

Answer 4

these are characteristics in organisms that are developed on response to their enviornment e.g. higher rate of RBC production at high altitude

this are not inherited and are not part of evolution

Question 5

why do species overproduce offspring

Answer 5

species produce more offspring than the environment can support which results in competition for resources e.g. food and water

this means only the best survive so the species evovles better

Question 6

what are the steps of natural selection

Answer 6

1. variation
2. some are better and worse adapted
3. well adapted are more likely to survive, reproduce, pass on beneficial genes / characteristics
4. over time this means in increase in the proportion of individuals inthe population wiht the beneficial characteristics
5. this is evolution by natural selection

Question 7

2 more detailed examples of natural selection through evolutio

Answer 7

finches on the galapagoes have evovled to have larger beaks so be able to eat large seeds

bacteria have evolved antibiotic resistance in response to over prescription of antibiotics - through mutatations - happens so quickyl because bacteria reproduce a lot and all teh ones who do not have it die so it is self fullfilling