18. Variation And Selection

Question 1

what is variation

Answer 1

the difference between organisms of the same species

Question 2

what causes variation

Answer 2

mutations in the genetic code

Question 3

what is phenotypic variation

Answer 3

the variation in physical traits and characteristics of organisms of the same species

Question 4

what is phenotypic variation caused by

Answer 4

both genes and the environment

Question 5

what is genetic variation

Answer 5

the difference between the genetic makeup of different organisms of the same species

Question 6

what is discontinuous variation

Answer 6

variation that produces distinct categories

Question 7

what is continuous variation

Answer 7

variation that cannot be placed into distinct categories and instead produces a spectrum

Question 8

what is mutation

Answer 8

a random change in the base sequence of the DNA of an organism

Question 9

state 2 things which may increase the rate of mutation

Answer 9

ionizing radiation
certain chemicals

Question 10

state 3 symptoms of sickle cell anaemia

Answer 10

headaches
fatigue
fainting

Question 11

how does sickle cell anaemia arise

Answer 11

• the base sequence in the DNA that codes for the hemoglobin protein changes
• this produces abnormal hemoglobin which leads to sickle shaped red blood cells

Question 12

what disease do people who are heterozygous for sickle cell anaemia have resistance to

Answer 12

malaria

Question 13

use a genetic diagram to sho the 4 offspring produced when two heterozygous sickle cell anaemia carriers reproduce

Answer 13

Question 14

describe the distribution of sickle cell anaemia with reference to the distribution of malaria

Answer 14

sickle cell anaemia tends to be found more in places where malaria is common

Question 15

explain the distribution of sickle cell anaemia with reference to the distribution of malaria

Answer 15

people who have sickle cell anaemia are resistant to malaria

those without sickle cell anaemia are not immune and are more likely to die from malaria

over time a majority of the population will carry the sickle cell anaemia gene

Question 16

what is an adaptive feature

Answer 16

any inherited feature which helps an organism to survive in its environment and pass on its genes

Question 17

what is an adaptive feature

Answer 17

the inherited functional features of an organism that increases the fitness of the organism

Question 18

define fitness

Answer 18

the ability of an organism to survive and pass on its genes in its environment

Question 19

what are hydrophytes

Answer 19

plants which are adapted to live in aquatic condition

Question 20

state 3 advantages of hydrophytes

Answer 20

wide and flat leaves
large air spaces
thin waxy cuticle

Question 21

what are xerophytes

Answer 21

plants which are adapted to live in very arid and dry conditions

Question 22

state 3 adaptations of xerophytes

Answer 22

rolled leaves
thick way cuticle
small needle shaped leaves

Question 23

describe the process of natural selection

Answer 23

• population are naturally varied due to random genetic mutations
• some of these mutations provide a selective advantage
• these organisms survive and reproduce, passing on the successful genes

Question 24

define evolution

Answer 24

a change in the features of organisms over time due to natural selection

Question 25

what is the process of adaptation

Answer 25

populations become suited to their environment over time due to natural selection

Question 26

what is the development of antibiotic resistance an example of

Answer 26

evolution by nature selection

Question 27

describe how antibiotic resistance arises

Answer 27

- a random genetic mutation causes a bacterium to become resistant to the antibiotic - when the antibiotic is used, al the bacteria that do not have the mutation are killed - the population containing just the resistance bacteria then begins to grow

Question 28

describe how selective breeding is carried out

Answer 28

- organisms with the desired traits are selected - these organisms are bred together - this process is repeated until the offspring have the desired characteristics

Question 29

what is the difference between natural selection and artificial selection

Answer 29

natural selection occurs when the selection pressures are created by the environment whereas artificial selection is when humans deliberately create selection pressures