Variation

Question 1

Explain variation

Answer 1

Difference of individuals in the same species.

Question 2

What is continuous variation

Answer 2

In a range of phenotypes between two extremes.

Question 3

Provide examples of variation

Answer 3

Body length
Body height
Body masses

Question 4

What is discontinuous variation

Answer 4

Results in limited number of phenotypes without intermediates.

Question 5

Provide examples of discontinuous variation

Answer 5

ABO Blood groups
Seed shape in peas
Seed color in peas

Question 6

What is usually causes discontinuous variation

Answer 6

Genes only

Question 7

What usually causes continuous variation

Answer 7

Genes
Environment

Question 8

What type of graph is usually for continuous variation

Answer 8

Histograms , usual trend

Question 9

What type of graph is used for discontinuous variation

Answer 9

Unusual trend, bar graphs

Question 10

What is mutation

Answer 10

The way new alleles are formed

Question 11

What is gene mutation

Answer 11

A change in the base sequence of DNA

Question 12

What are sources of genetic variation in the population. (4)

Answer 12

Mutation
Meiosis
Random fertilization
Random mating

Question 12

What increases the rate of mutation

Answer 12

Ionizing radiation
Exposure to some chemicals

Question 13

What are adaptive features

Answer 13

An inherited (structural) feature that helps an organism to survive and reproduce in its environment.

Question 14

Process of natural selection(5)

Answer 14

• genetic variation within populations
• production of many offspring
• struggle for survival+ competition for resources
• a greater chance of reproduction by individuals that are better adapted to an environment than the other
• these individuals pass on their allele to the next generation.

Question 15

More on natural selection

Answer 15

• Species evolve
• development of anti-biotic -resistance strains in bacteria by natural selection.
• Better adapted organisms thrive

Question 16

Process of selective breeding

Answer 16

1. Selecting by individuals with desirable features
2. Crossing these individuals to produce the next generation
3. Selection of offspring showing the desirable features

Question 16

What is selective breeding done by

Answer 16

Artificial selection

Question 17

When it carried over many generations to: (2)

Answer 17

• Improve crop plants , more economic value
• improve domesticated animals e.g. more cows produce more milk , dogs have better appearance , wheat that is easier to separate from grain.

Question 18

What is artificial selection

Answer 18

Organisms with valued characteristics come together and produce offspring that share these valuable characteristics.

Question 19

What is adaption

Answer 19

The process resulting in natural selection in which populations become more suited to their environment and many generations

Question 20

What is a xerophyte

Answer 20

A organism that lives in desert areas where water is scarce and windy , rapid evaporation habitats . E.g. cactus , marram grass

Question 21

What is a hydrophyte

Answer 21

An organism that lives in partly or fully submerged in water

Question 22

Describe plants that are xerophytes (6)

Answer 22

Stomata- open at night and closed during midday when evaporation is at its highest. Stomata is sunk into the pits.

Cuticle- Waxy cuticle, impermeable to water.

Roots- deep roots to reach for water underground.

Leaves - reduced spines for less, surface area for transpiration

Roots- shallow spreading roots collect occasional rain.

Leaves- rolled leaves , leaf hairs and sunk stomata , sunk in pits to trap moist air.

Question 23

Describe hydrophytes

Answer 23

• Roots are often reduced and root hairs are often absent.
• Stomata on upper surface , waxy thick cuticle that repels water away from stomata keeping it clear and open
• Lack of xylem tubes, no stomata underside of leaves.
• minimal cuticle formation.
• Leaves are are highly divided for maximum absorption + photosynthesis with large surface area.