Unit 18

Question 1

what is variation

Answer 1

the differences between individuals of the same species

Question 2

result of continuous variation

Answer 2

when theres a range of phenotypes between two extremes

Question 3

result of discontinuous variation

Answer 3

a limited number of phenotypes with no intermediates(blood groups etc)

Question 4

what is discontinuous variation usually caused by

Answer 4

genes

Question 5

what is continuous variation usually caused by

Answer 5

by both genes and environment

Question 6

what is continuous variation

Answer 6

when there are small degrees of differences for a particular characteristic between individuals

Question 7

what is discontinuous variation

Answer 7

when there are distinct differences for a characteristic with no ‘inbetweens’

Question 8

what does the graph of continuous variation look like

Answer 8

smooth curves

Question 9

what does the graph of discontinuous variation look like

Answer 9

blocks, step like shapes

Question 10

what is phenotypic variation

Answer 10

when the variation is caused by genetics or environment

Question 11

what is genetic variation

Answer 11

when the variation is completely controlled by genes

Question 12

what is mutation

Answer 12

genetic changes

Question 13

what is the result of mutation

Answer 13

occasionally new alleles are formed

Question 14

what is gene mutation

Answer 14

the random change in the base sequence of DNA

Question 15

what increases the chance/rate of mutation

Answer 15

ionising radiation(gamma and Xrays)
certain types of chemicals

Question 16

what are the sources of genetic variation in populations

Answer 16

mutation,meiosis,random mating and random fertilization

Question 17

what are adaptive features

Answer 17

an inherited feature that helps an organism to survive and reproduce in its environment

Question 18

what is fitness

Answer 18

the probability of an organism surviving and reproducing in the environment in which it is found

Question 19

what are hydrophytes

Answer 19

plants adapted to live in extremely wet conditions

Question 20

what are the adaptations of hydrophytes

Answer 20

large air spaces in the leaves- keep them close to the surface of the water for more photosynthesis
small roots- they can extract nutrients from the surrounding water
stomata usually open all the time and found on the upper epidermis

Question 21

what are xerophytes

Answer 21

they are plants adapted to live in extremely dry conditions

Question 22

common adaptations of xerophytes

Answer 22

thick waxy cuticle- cuts down water loss
sunken stomata- reduces evaporation rate
small leaves-many have small needle shaped leaves
extensive shallow roots
thickened leaves or stems

Question 23

what is natural selection

Answer 23

the individuals that have the best adaptive features are the ones most likely to survive and reproduce

Question 24

why is there a ‘struggle for survival’ in many environments

Answer 24

many organisms produce more offspring than the environment is able to support which leads to competition for foods and other resources

Question 25

what is survival of the fittest

Answer 25

individuals with characteristics most suited to the environment have a higher chance of survival and reproduction. These characteristics are then passed down to their offspring leads to a greater number of individuals with the better adapted variations

Question 26

what is adaptation

Answer 26

the process,resulting from natural selection, by which populations become more suited to their environment over many generations

Question 27

how is the development of antibiotic resistant bacteria an example of natural selection

Answer 27

the bacteria that possess the characteristics that make it resistant to antibiotics reproduce and pass it on the next generation

Question 28

what is selective breeding

Answer 28

to select individuals with desirable characteristics and breed them together

Question 29

outline the process of selective breeding

Answer 29

the offspring with desirable characteristics are bred together again and again until their offspring reliably show the selected characteristics

Question 30

differences between natural selection and artificial selection

Answer 30

artificial selection only occurs when humans intervene in natural, the features are better adapted for survival in artificial, the features are useful to humans natural takes a long time to occur artificial takes a shorter amount of time