Natural Selection And Evolution Flashcards
What is natural selection?
A process in which selection pressures act on a population so that individuals possessing a particular characteristic (or allele) are more likely to survive and pass on their alleles to their offspring
What caused a change in the colour of peppered moths?
Before 1849 there was little air pollution. The light-coloured peppered moth had good camouflage on lichen covered trees. However, black moths were rare due to their poor camouflage. After 1849 (Industrial revolution) air pollution from coal burning factories covered trees with soot and killed the lichen. The light-coloured peppered moth no longer had the advantage of good camouflage. However, the black moth has good camouflage so their population increased
What has caused bacteria to become resistant to antibiotics?
Humans are now given bacteria for even the most trivial of ailments.
How are bacteria resistant?
Mutations happen all the time in all living organisms. In bacteria this could give the bacterium resistance to an antibiotic. In a situation where antibiotics are widely used this bacteria has an advantage over a non-resistant bacteria of the same type. This will survive and multiply. The generation time of bacteria can be as short as 20 minutes. Very soon a population of bacteria could become almost entirely made up of resistant types.
What is evolution?
A change in characteristics of a population or a species
What does sickle cell anaemia effect?
The formation of haemoglobin in red blood cells. The abnormal haemoglobin causes the red blood cells to become distorted when the oxygen concentration of the surrounding is low.
How can the sickle cell anaemia allele actually benefit people?
Heterozygous ‘carriers’ of the allele usually show no symptoms of the disease at all, even though 50% of the haemoglobin in their blood cells is abnormal. They are however more resistant to malaria.
Why do bacteria become resistant to antibiotics and not immune?
Individuals become immune - they have an immune response (due to an immune system).
Populations of bacteria become resistant as a result of chance mutations.
Example question of how a characteristic on an animal evolved: Peacock’s tails?
1) millions of years ago, there was genetic variation in the population of peacocks as a result of mutation
2) some peacocks had large, colourful tails and others had small, plain-coloured tails
3) the peacocks with large, colourful tails had a selective advantage as it was easier for them to attract females to mate with
4) therefore, the peacocks with small, plain coloured tails died without reproducing and the peacocks with large, colourful tails survived and reproduced, passing on the ‘large, colourful tail’ allele to their offspring
5) over time, this lead to a change in the overall genetic makeup of peacocks
Describe briefly what Charles Darwin did?
It was Charles Darwin who first developed the idea that all life on earth has evolved from common ancestors by he process of natural selection. He developed his ideas based on the animals and plants he saw on his famous voyage of the Beagle along with lots of evidence he collected afterwards
