B17 - Variation and Selection

Question 1

Variation

Answer 1

differences between individuals of the same species

Question 2

mutation

Answer 2

genetic change

Question 3

how are new alleles formed?

Answer 3

mutations (change the sequence of DNA bases which results in different proteins being coded for)

Question 4

what does discontinuous variation result in?

Answer 4

limited number of phenotypes with no intermediates

Question 5

what does continuous variation result in?

Answer 5

range of phenotypes between 2 extremes

Question 6

3 examples of genetic variation

Answer 6

-eye colour
-biological sex
-blood group

Question 7

3 examples of environmental variation

Answer 7

-piercings
-tattoos
-accent

Question 8

3 examples of both environmental and genetic variation

Answer 8

-sporting ability
-height
-weight

Question 9

3 examples of continuous variation

Answer 9

-weight
-height
-leaf surface area

Question 10

3 examples of discontinuous variation

Answer 10

-blood groups
-eye colour
-skin colour

Question 11

2 main causes of variation are?

Answer 11

-genetics (alleles and genotype)
-environment

Question 12

whats the type of variation passed on to our chidren?

Answer 12

genetic variation

Question 13

how does fertilisation lead to more variation?

Answer 13

the fertilised egg contains genes from both parents, which is a new mixture. Mix of alleles from both parents gives more variation

Question 14

how does formation of gametes lead to variation?

Answer 14

during meiosis, sex chromosomes cross over (meiosis) and create new combinations of genes. This leads to all eggs and sperms being genetically different

Question 15

what are 3 factors that cause mutations?

Answer 15

-radiation
-chemical
-natural causes

Question 16

what are the 5 steps of selective breeding?

Answer 16

1) decide which characteristic is most important (desired characteristics / features) and select parents that show high levels of this characteristic
2) breed these individuals
3) select the best offspring
4) breed again
5) repeat the process over many generations and eventually all sheep will have the important characteristic chosen

Question 17

3 desired characteristics in animals

Answer 17

-muscle mass (meat)
-produce more milk
-produce more wool

Question 18

2 desired characteristics in plants

Answer 18

-increased yield (to feed our increasing population)
-disease resistant

Question 19

selective breeding

Answer 19

when humans artificially select the organisms that breed so that the frequency of alleles for desired characteristics increases in a population

Question 20

selective breeding has changed the characteristics of wheat, making it: [2]

Answer 20

-easier to harvest
-giving higher yields

Question 21

2 problems of selective breeding

Answer 21

-increased risk of genetic disease (pugs have short stubby noses and may have breathing problems)
-reduction in variation (if that type of allele is not resistant to a disease, and almost all the organisms have that allele, they may become extinct / the other variations that have not been bred can go extinct)

Question 22

why is it useful to a farmer for a crop to ripen at the same time and grow to the same height?

Answer 22

-farmers use machines that can’t differenciate ripe and not ripe crops so in order to get all the ripe crops and not cut off un-ripe crops
-those machines also cant move according to the height of the crop, it just cuts the crop all in the same place so some crops may have longer, unnecessary stems and others may not get cut all the way
-If done by hand, difficult and troublesome to choose the ripe and not ripe crops

Question 23

formula for percentage increase in yield

Answer 23

(new-old / old) x 100

Question 24

6 steps of natural selection

Answer 24

1) There is genetic VARIATION is every population
2) All organisms OVERPRODUCE (to not go extinct) when conditions are favourable
3) this leads to COMPETITION for resources (water, food, light, mates)
4) competition, predators, and disease means some organisms are better adapted to SURVIVE
5) those organisms that survived REPRODUCE
6) then the ALLELES for the advantageous characteristics (characteristics of organisms that survived) will be passed onto their offspring and become more common in the population over many generations

Question 25

what is natural selection

Answer 25

how organisms adapt from one generation to another

Question 26

4 steps of antibiotic resistance in bacteria

Answer 26

1) there is variation in a population of bacteria so through random mutations, some bacteria are resistant to a particular antibiotic (phenotypes)
2) If the antibiotic is used, all bacteria except for the one with the mutation to be antibiotic is killed. the resistant bacteria will survive
3) this survived bacteria divides and reproduces (asexually) and it’s offspring will also have the mutation for antibiotic resistance
4) over time (few generations) all the bacteria will be resistant to the antibiotic (all will have the advantageous characteristic) and there will be an increase in the frequency of the antibiotic resistance allele