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Biology - IGCSE > Ch 18 - (Variation & Selection) > Flashcards

Ch 18 - (Variation & Selection) Flashcards

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1
Q

Define Variation.

A

differences between individuals of the same species

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2
Q

What is phenotypic variation?

A

difference in features between individuals of the same species

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3
Q

How are the differences in phenotypic variation caused?

A

differences in genes, which is genetic variation

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4
Q

What are the 2 types of phenotypic variations?

A

1.Continuous Variation

  1. Discontinuous Variation
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5
Q

What is continuous variation?

A
  • very many small degrees of difference for a particular characteristic between individuals
  • they are arranged in order and can usually be measured on a scale

Ex- height, mass, finger

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6
Q

What is discontinuous variation?

A

distinct differences for a characteristic

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7
Q

How is phenotypic variation caused?

A
  1. It can be genetic - controlled entirely by genes
  2. environmental - caused entirely by the environment in which the organism lives
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8
Q

What are examples of genetic variation in humans?

A
  • blood group
  • eye colour
  • gender
  • ability to roll tongue
  • whether ear lobes are free or fixed
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9
Q

What are characteristics of all species affected by?

A

environmental factors such as climate, diet, accidents, culture and lifestyle

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10
Q

What is discontinuous variation caused by?

A

genetic variation alone

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11
Q

What are mutations?

A

genetic changes

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12
Q

What do mutations lead to?

A
  • o effect on the phenotype
  • development of new alleles and so new phenotypes and if they do, most have a small effect
  • harmful changes (Ex- sickle cell anaemia)
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13
Q

What do alleles give an individual?

A

survival advantage over other members of the species

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14
Q

How do mutations happen?

A

spontaneously and continuously

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15
Q

How can the frequency of mutations be increased?

A
  1. Ionising radiation (e.g. gamma rays and X - rays) - which can damage bonds and cause changes in base sequences
  2. non-ionising radiation (e.g. ultra-violet) - can also damage bonds and cause changes in base sequences
  3. Certain types of chemicals - for example chemicals such as tar in tobacco
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16
Q

What can increased rates of mutations lead to?

A

cancerous

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17
Q

What re the ways in which genetic variation happens?

A
  1. Mutations:
    - random genetic changes to the base sequence of DNA
  • New alleles form through these random changes to
    DNA
  1. Meiosis
    - New allele combinations form through segregation
  2. Random mating
    - Which partnerships form for sexual reproduction
  3. Random fertilization
    Which sperm and egg combinations occur during sexual reproduction
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18
Q

What are adaptive features?

A

inherited functional features of an organism that increase its fitness

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19
Q

what is fitness?

A

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

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20
Q

What is hydrophytes?

A

Plants adapted to live in extremely wet conditions

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21
Q

What are common adaptations in hydrophytes?

A
  1. Large air spaces in their leaves
  2. Small roots
  3. Stomata
22
Q

What does Large air spaces in their leaves do as an adaptation for hydrophytes?

A

for flotation, to keep the leaves close to the surface of the water where there is more light for photosynthesis

23
Q

What does Small roots do as an adaptation for hydrophytes?

A

extract nutrients from the surrounding water through their tissues

24
Q

What does stomata do as an adaptation for hydrophytes?

A

open all the time and mainly found on the upper epidermis of the leaf where they can exchange gases much more easily with the air

25
Q

What is xerophytes?

A

Plant adapted to live in extremely dry conditions

26
Q

What are common adaptations in xerophytes?

A
  1. Thick waxy cuticle
  2. Sunken stomata
  3. Leaf rolled
  4. Small leaves:

5.Extensive shallow roots

6.Thickened leaves or stems

27
Q

What does thick waxy cuticle do as an adaptation for xerophytes?

A
  • the cuticle cuts down water loss in two ways:
  1. it acts as a barrier to evaporation and also the shiny
  2. surface reflects heat and so lowers the temperature
28
Q

What does Sunken stomata do as an adaptation for xerophytes?

A
  • stomata may be sunk in pits in the epidermis
  • moist air trapped here lengthens the diffusion pathway
  • reduces the evaporation rate
29
Q

What does Leaf rolled
do as an adaptation for xerophytes?

A
  • stomata inside and an inner surface covered in hairs
  • traps moist air and prevents air movement across stomata
  • reduces transpiration
30
Q

What does Small leaves do as an adaptation for xerophytes?

A
  • small, needle-shaped leaves
  • reduce the surface area and therefore the evaporating surface
31
Q

What does Extensive shallow roots do as an adaptation for xerophytes?

A

allow for the quick absorption of large quantities of water when it rains

32
Q

What does thicken leaves or stems do as an adaptation for xerophytes?

A

contain cells that store water

33
Q

What results in natural selection?

A

individuals that have the best adaptive features are the ones most likely to survive and reproduce

34
Q

What do individual species show?

A

range of variation caused by differences in genes

35
Q

What happens when species reproduce?

A
  • produce more offspring than the environment is able to support
  • competition for food and other resources which results in a ‘struggle for survival’
36
Q

Which individuals have a high chance of survival and to reproduce?

A

characteristics most suited to the environment

37
Q

What does more chances of survival and reproduce lead to?

A
  • alleles resulting in these characteristics are passed to their offspring at a higher rate
  • next generation, will hv greater number of individuals with the better adapted variations in characteristics
38
Q

Who is survival of the fittest?

A

theory of natural selection was put forward by Charles Darwin

39
Q

What happens if environment does not changes in adaptation?

A

selection does not change

40
Q

what happens if environment changes in adaptation?

A
  • a chance mutation produces a new allele,
  • selection might now favor individuals with different characteristics or with the new allele
41
Q

What Favours individuals when environment does not change?

A

same characteristics as their parents

42
Q

What happens to individual that survive and reproduce?

A
  • different set of alleles that they pass on to their offspring
  • change in the characteristics of the species - it will produce evolution
43
Q

Define evolution.

A

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

44
Q

What does natural selection result in?

A

process of adaptation

45
Q

What happens as a result of evolution?

A

populations of organisms become better suited to their environment

46
Q

What does selective breeding mean?

A

elect individuals with desirable characteristics and breed them together

47
Q

Why does the selective breeding process not stop?

A

not all of the offspring will show the characteristics you want so offspring that do show the desired characteristics are selected and bred together

48
Q

Does selective breeding process hv to be repeated?

A

repeated for many successive generations

49
Q

What happens in natural selection?

A
  • occurs naturally
  • results in development of populations with features that are better adapted to their environment and survival
  • usually take a longer time to occur
50
Q

What happens in artificial selection?

A
  • only occurs when humans intervene
  • results in development of populations with features that are useful to humans and not necessarily to survival of individual
  • take less time as only individuals with the desired features are allowed to reproduce

Biology - IGCSE (19 decks)

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