chapter 18

Question 1

Define variation

Answer 1

differences between organisms of the species

Question 2

describe the properties of continuous variation , its examples and what it is controlled by, type of graph

Answer 2

Properties:
- can be measured
- results in a range of phenotype
- quantitative
- have intermediate value

Examples :
- body mass
- height

Controlled by : genes and environment

graph - bell shaped

Question 3

describe the properties of discontinuous variation , its examples and what it is controlled by

Answer 3

Properties:
- cannot be measured
- distinct phenotype
- no intermediate value

Examples :
- A, B, O blood group
- fingerprint
- ability to roll tongue
- colour of snapdragon flower

Controlled by : genes

graph - bar chart

Question 4

Describe mutation

Answer 4

Change in DNA base sequence

can happen randomly and continously , but their frequency can be increased by exposure to mutagen

Question 5

Mutation can sometimes lead to what?

Answer 5

Development of new allele and so new phenotype. New allele gives individual survival advantages

can also lead to harmful changes like sickle cell anaemia

Question 6

State the different types of mutagen

Answer 6

Physical : all types of ionising radiation which can damage bonds and cause changes in base sequences

Chemical : chemicals like tar in tabacoo

increase rate of mutagen can cause cells to become cancerous

Question 7

what is an adaptive feature

Answer 7

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

Question 8

What is fitness?

Answer 8

the probability for an organism to survive and reproduce in the environment in which it is found

Question 9

Describe what are hydrophytes and their adaptations and functions

Answer 9

Plants adapted to live in extremely wet conditions

Adaptations and functions:
1. Stomata found on upper epidermis of leaf ( faster diffusion of gases )
2. the cuticle is thinner ( no need to prevent water loss . Have plenty of water )
3. Large air spaces in their leaves ( provide buoyancy to keep leaves close to surface of the water for more light for photosynthesis )
4. Small roots ( allow plants to extract nutrients from surrounding water through tissues )

Question 10

Describe what are xerophytes and their adaptations and functions

Answer 10

Plants adapted to live in extremely dry conditions

Adaptation & functions :
1. thick waxy cuticle ( waterproof, reduce water loss, shiny surface reflects heat and so lowers temperature )
2. Sunken stomata ( stomata sunken in pits of epidermis, moist air trapped, increases humidity , reducing rate of transpiration )
3. Rolled leaf ( inner surface covered in hairs, traps moist air which increases humidity and reduces transpiration )
4. Small leaves ( have needle-shaped leaves which reduce surface area and transpiration, reducing water loss )
5. Thickened leaves ( store water )
6. Extensive shallow roots ( allow for absorption of water from the soil surface when it rains )
7. Extensive deep root ( allow root to absorb water from water table )

Question 11

describe natural selection

Answer 11

The individual that has the best adaptive features are the ones most likely to survive and reproduce

Reasons:
1. genetic variation within species
2. Competition for resources ( food, mate, space) , resulting in a struggle for survival
3.Individuals with most suited characteristics have a higher chance of surviving and more chances to reproduce, passing advantages allele to next generation

Question 12

describe the process of natural selection

Answer 12

1. Variation due to mutation in genes
2. Better adapted individual are more likely to survive and reproduce
3. Passing on advantages allele to offpsring
4. The individual that cannot adapt well will eventually decrease in number
5. Overtime, frequency of better adapted individual will increase and all will have the same adaptive feature.

Question 13

describe adaptation

Answer 13

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

Question 14

Describe artificial selection

Answer 14

selective breeding :
1. select individuals with desired features and breed them together
2. offsprings that show desired features are chosen and bred together
3. Process repeated for many generations

Question 15

Describe the difference between natural and artificial selection

Answer 15

Natural selection: Artificial selection:
- selection by environment - selected by humans

• Develop features that has better adaptations - Reduces variation, features
  only useful to humans
• takes longer time - takes shorter

Question 16

Describe the characteristics for selective breeding in plants and example

Answer 16

1. diseases resistance in food crops
2. Increased crop yield
3. Hardiness to weather conditions
4. Better tasting fruit
5. Large or unusual flowers

Wild brassica ( rise in cabbage, brussels, kale, broccoli, cauliflower )

Question 17

Describe the characteristics for selective breeding in animals and example

Answer 17

1. cows goat sheep that produce alot of milk and meat
2. chicken that lay more eggs
3. domestic dogs that have gentler nature
4. Sheep with good quality wool
5. horses with fine features and a very fast running pace

Example : dogs from wolves

Question 18

describe the process of selective breeding

Answer 18

Result: variety of cow that produces lots of milk

Process:
1. chose cows in herd that produce the most milk
2. Let only those cows breed
3. Chose the offspring that produces the most milk
4. Let only these offspring breed
5. keep repeating the process of selection and breeding until goal achieved .