Natural and Artificial Selection

Question 1

Darwin’s theory of evolution by natural selection

Answer 1

-All populations contain genetic variation
-Genetic variants with advantageous characteristics have increased survival chances
-Surviving individuals are more likely to reproduce and pass on advantageous traits
-Over generations these traits become common in the population

Question 2

MVASRGGE
Steps of evolution

Answer 2

Mutation
Variation
Adapted
Survived
Reproduced
Genes
Generations
Evolution

Question 3

Bacterial resistance due to antibiotics

Answer 3

-Random mutation leads to new allele coding for antibiotic resistance
-When bacterial population is exposed to an antibiotic, unresistant bacteria die, while resistant bacteria survive
-Surviving bacteria are more likely to reproduce, passing on the resistant allele to their offspring
-Over generations the frequency of the allele increases, leading to a resistant strain of bacteria

Question 4

Difficulty of controlling resistant bacterial strains

Answer 4

-Bacterial population can only be treated with a different antibiotic (sometimes several antibiotics)
-New antibiotics can take time to be developed

Question 5

Evolution definition

Answer 5

When there is a cumulative change in heritable characteristics OVER TIME in a population (occurring via natural selection)

Question 6

What can be affected by environmental factors

Answer 6

Characteristics determined by polygenic inheritance

Question 7

Natural Selection definition

Answer 7

The process where organisms that are better adapted to an environment will survive and reproduce

Question 8

Causes of variation

Answer 8

-Genetics
-Mutations
-Meiosis
-Random fertilisation
-Environment

Question 9

Artificial selection definition:

Answer 9

When HUMANS artificially select organisms they want to breed together so that the genes with desirable characteristics can remain in a population

Question 10

Selective breeding steps

Answer 10

Choose male and female with desired characteristics
Breed them together
Choose offspring which display desired characteristics
Breed these offspring together
Repeat this for several generations until all offspring have desired characteristics

Question 11

Benefits of selective breeding

Answer 11

Desired characteristics can be obtained
Can use semen from one male to mate with many females
Safer for female animals
Cheaper/quicker to transport semen
Semen can be stored even after death of male

Question 12

Problems with selective breeding

Answer 12

Reduction in gene pool (less alleles in a population) can lead to ‘inbreeding’
Prone to new diseases/genetic defects
Reduced genetic variation -> less likelihood to adapt

Question 13

Natural Selection vs Selective Breeding

Answer 13

Occurs naturally vs occurs when humans intervene
Features adapted to environment and survival vs features useful to humans and not survival
Long time to occur vs less time to occur

Question 14

Desired characteristics in plants

Answer 14

Disease resistance
Increased crop yield
Tolerance of weather conditions
Better tasting fruits
Large/unusual flowers

Question 15

Desired characteristics in animals

Answer 15

Quantity of milk/meat
Large eggs
Domesticated animals
Quality wool
Horses with fine features and pace

Question 16

Clone definition

Answer 16

Groups of cells/organisms that are genetically identical

Question 17

Micropropagation

Answer 17

Explant cells cut from parent plant using sterile tools
The tissue is placed in sterile nutrient agar, containing a high concentration of hormones to stimulate cell growth
A mass of cells (callus) grows
Some callus cells can be transferred to a different medium with a diff. combination of minerals and auxins to develop roots/shoots
They grow into plantlets and can be grown in compost

Question 18

Advantages of micropropagation

Answer 18

Clones are genetically identical
Can produce plants with desirable characteristics:
Cheaply
With a greater yield
Quickly (faster growth)
At any time of the year
Identically (maintain characteristics)
Disease free/resistant

Question 19

Disadvantages of micropropagation

Answer 19

Trained personnel and sterile lab required
All plants produces are genetically identical i.e. all are vulnerable to the same diseases and pests

Question 20

Embryo cloning e.g. cattle

Answer 20

The best (prize) cow is given hormones to make it produce egg cells
Sperm from a prize bull is collected and the cow is artificially inseminated
The fertilised egg divides into an embryo, which is then removed from the prize cow
The embryo is split up and each piece starts dividing into genetically identical embryos
The embryos are implanted into surrogate cows
Several clone calves are born

Question 21

Adult cell cloning (nuclear transfer)

Answer 21

Exact copy of parent
Egg cells removed from ovaries with nucleus removed
Somatic (body) cells from animal B are grown in starvation conditions (return to embryonic state)
Nucleus from the somatic cell is injected into egg cell
Cell is stimulated (electric shock) to divide by mitosis
Embryo is implanted into surrogate mother
Cloned animal is identical to somatic cell donor

Question 22

Benefits of animal cloning

Answer 22

Can be used to preserve endangered species or resurrect extinct animals
Could be used to grow new organs genetically identical to parent cells i.e. transplant patients could get identical organs to save their lives

Question 23

Callus definition

Answer 23

A mass of undifferentiated/unspecialized cells

Question 24

Callus definition

Answer 24

A mass of undifferentiated/unspecialized cells

Question 25

Explant definition

Answer 25

Fragments of plant tissue that are transferred to a different medium

Question 26

In vitro definition

Answer 26

Something that is grown outside a living organism