18: Variation and Selection

Question 1

Process of adaptation

Answer 1

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

Question 2

Natural selection

Answer 2

Organisms with favourable alleles and adv characteristics have a higher probability of surviving & reproducing.

variation & chance of mutation -> competition for resources -> develop phenotype(char) = survival adv:

• live longer
• breed more
• be more likely to pass their genes on

Repeated over gen, the ‘mutated’ phenotype = norm.

Question 3

Selective breeding

Answer 3

• Humans select animals/ plants with desirable features
• breed them
• repeat the selective breeding over many generations
  (artificial selection)

Question 4

Evolution

Answer 4

change in adaptive features of a population over time as the result of natural selection.

Question 5

Antibiotic resistance

Answer 5

• bacteria - evolution occurs in a much shorter time span → variation by mutation in a bacterial cell alllele
• mutation → resistant to antibiotic →
• r bacteria doesn’t die, continue reproduce with < competition = genes for antibiotic resistance are passed
• whole population of bacteria becomes antibiotic-resistant

Question 6

Natural vs Artificial Selection

Answer 6

N:

• occurs naturally
• development of features: better adapted to their environment and survival
• takes a long time to occur

A:

• only occurs when humans intervene
• features: useful to humans, not necessaraly to survival
• takes less time: only individ. with desired features are allowed to reproduce.

Question 7

Variation definition + why beneficial

Answer 7

differences between individuals of the same species

beneficial:
1. allows natural selection to occur
2. reduces the risk of extinction from disease

Question 8

Mutation defition + cause

Answer 8

definition: genetic change which result in a change in the sequence of DNA bases

the way in which new alleles are formed (mutated - altered, change in function - new formed)

exposure to some chemicals & ionising radiation increase rate of mutation

Question 9

Gene mutation

Answer 9

change in the base sequence of DNA

Question 10

Genetic variation

Answer 10

G: differences between individuals of the same species

caused by differences in genes
- increased during meiosis (produces gametes) ➝ each gamete has a dif set of alleles = when 2 gametes fuse ➝ entirely new set of genes is produced.

e.g. blood group, ability to roll tongue, loved/less earlobes, eye colour, gender

Question 11

Phenotypic variation

Answer 11

P: difference in features between individuals of the same species

observable features
caused by both genetic and environmental factors

Continuous v: results in a range of phenotypes between two extremes, e.g. height in humans

Discountinous v: results in a limited number of phenotypes with no intermediates, e.g. tongue rolling
mostly caused by genes alone, e.g. blood groups in humans.

Question 12

Adaptive features definition

Answer 12

• as the inherited functional features of an organism

- that increase its fitness

Question 13

Define Adaptive features

Answer 13

• as the inherited functional features of an organism

- that increase its fitness

Question 14

Define Fitness

Answer 14

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

Question 15

Adaptive features of Xerophytes (4)

Answer 15

very dry climats - cacti
features help to reduce water loss.

• fewer/sunken stomata: bubbles of moist air trapped around; lowers water potential gradient = less water lost
• small, rolled leaves or spines: reduces SA, traps moisture to lower water potential gradient
• deep roots: allow to absorb water from soil
• thick waxy cuticle: waterproof barrier

Question 16

qwer

Answer 16

qwer