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Biology IGCSE CIE Extended > 16.1. Types of Reproduction > Flashcards

16.1. Types of Reproduction Flashcards

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1
Q

What does asexual reproduction NOT require?

A

Asexual reproduction does not involve sex cells or fertilisation

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2
Q

What does asexual reproduction require?

A

Only one parent is required

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3
Q

Due to only one parent being required, what is different from sexual reproduction?

A

there is no fusion of gametes and no mixing of genetic information

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4
Q

What is a similarity between the parent and the offspring in asexual reproduction?

A

As a result, the offspring are genetically identical to the parent and to each other (clones)

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5
Q

Asexual reproduction defintion

A

Asexual reproduction is defined as a process resulting in genetically identical offspring from one parent

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6
Q

How do bacteria reproduce?

A

Bacteria produce exact genetic copies of themselves in a type of asexual reproduction called binary fission:

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7
Q

How can plants reproduce asexually?

A

Plants can reproduce asexually using bulbs and tubers

- by using runners

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8
Q

What are bulbs and tubers?

A

these are food storage organs from which budding can occur, producing new plants which are genetically identical to the parent plant

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9
Q

What are runners?

A

Some plants grow side shoots called runners that contain tiny plantlets on them (a good example of this are strawberry plants. These will grow roots and develop into separate plants, again being genetically identical to the parent plant

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10
Q

What are 4 advantages of asexual reproduction?

A
  • population can be increased rapidly when conditions are right
  • can exploit suitable environments quickly
  • more time and energy efficient
  • reproduction completed much faster than sexual reproduction
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11
Q

What are 3 disadvantages of asexual reproduction?

A
  • limited genetic variation in population - offspring are genetically identical to their parents
  • population is vulnerable to changes in conditions and may only be suited for one habitat
  • disease is likely to affect the whole population as there is no genetic variation
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12
Q

When (in what organism) is asexual reproduction particularly advantageous and why?

A

Specifically in crop plants, asexual reproduction can be advantageous as it means that a plant that has good characteristics (high yield, disease-resistant, hardy) can be made to reproduce asexually and the entire crop will show the same characteristics

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13
Q

sexual reproduction definition

A

Sexual reproduction is a process involving the fusion of the nuclei of two gametes (sex cells) to form a zygote (fertilised egg cell) and the production of offspring that are genetically different from each other

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14
Q

Fertilisation definition

A

Fertilisation is defined as the fusion of gamete nuclei, and as each gamete comes from a different parent, there is variation in the offspring

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15
Q

What is a gamete?

A

A gamete is a sex cell

in animals: sperm and ovum; in plants pollen nucleus and ovum

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16
Q

How do gametes differ from normal cells? What is this called?

A

Gametes differ from normal cells as they contain half the number of chromosomes found in other body cells – we say they have a haploid nucleus

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17
Q

How do gametes only have half the number of chromosomes found in the body?

A

This is because they only contain one copy of each chromosome, rather than the two copies found in other body cells

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18
Q

How many chromosomes does a normal cell have compared to a gamete?

A

In human beings, a normal body cell contains 46 chromosomes but each gamete contains 23 chromosomes

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19
Q

What is a zygote?

A

When the male and female gametes fuse, they become a zygote (fertilised egg cell)

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20
Q

How many chromosomes does a zygote have and what is this called?

A

This contains the full 46 chromosomes, half of which came from the father and half from the mother – we say the zygote has a diploid nucleus

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21
Q

What are 3 advantages of sexual reproduction?

A
  • increases genetic variation
  • the species can adapt to new environments due to variation, giving them a survival advantage
  • disease is less likely to affect population (due to variation)
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22
Q

What are 2 disadvantages of sexual reproduction?

A
  • takes time and energy to find mates

- difficult for isolates members of the species to reproduce

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23
Q

In what way do most crop plants reproduce and how is this beneficial?

A

Most crop plants reproduce sexually and this is an advantage as it means variation is increased and a genetic variant may be produced which is better able to cope with weather changes, or produces significantly higher yield

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24
Q

What may be a disadvantage as a result of crop plants reproducing sexually?

A

The disadvantage is that the variation may lead to offspring that are less successful than the parent plant at growing well or producing a good harvest

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25
Q

What are the reproductive organ of the plant?

A

flowers

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26
Q

What do flowers contain?

A

They usually contain both male and female reproductive parts

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27
Q

What do plants produce which acts as the male gamete?

A

Plants produce pollen which contains a nucleus inside that is the male gamete

28
Q

What is a difference between pollen and sperm?

A

Unlike the male gamete in humans (sperm), pollen is not capable of locomotion (moving from one place to another)

29
Q

What is pollination?

A

plants have to have mechanisms in place to transfer pollen from the anther to the stigma
This process is known as pollination

30
Q

In what two ways can pollination occur?

A

here are two main mechanisms by which it occurs: transferred by insects (or other animals like birds) or transferred by wind

31
Q

Does the structure of insect and wind=pollinated flowers differ?

A

YES
The structure of insect and wind-pollinated flowers are slightly different as each is adapted for their specific function

32
Q

Sepal definition

A

protects unopened flower

33
Q

petals definition

A

brightly coloured in insect-pollinated flowers to attract insects

34
Q

anther definition

A

produces and releases the male sex cell (pollen grain)

35
Q

stigma definition

A

top of the female part of the flower which collects pollen grains

36
Q

ovary definition

A

produces the female sex cell (ovum)

37
Q

ovule definition

A

contains the female sex cells (found inside the ovary)

38
Q

How do the petals differ in an insect vs wind pollinated flower?

A

🦟 - large and brightly coloured to attract insects

🌬 - small and dull, often green or brown in colour

39
Q

How does the scent and nectar differ in an insect vs wind pollinated flower?

A

🦟- present - entices insect to visit the flower and push past stamen to get to nectar
🌬 - absent - no need to waste energy producing these as no need to attract insects

40
Q

How does the number of pollen grains differ in an insect vs wind pollinated flower?

A

🦟 - moderate - insects transfer pollen grains efficiently with a high chance of successful pollination
🌬 - large amounts - most pollen grains are not transferred to another flower so the more produced, the better the chance of some successful pollination occurring

41
Q

How do the pollen grains differ in an insect vs wind pollinated flower?

A

🦟 - larger, sticky and / or spiky to attach to insects and be carried away
🌬 - smooth, small and light so they are easily blown by the wind

42
Q

How do the anthers differ in an insect vs wind pollinated flower?

A

🦟 - inside flower, stiff and firmly attached to brush against insects
🌬 - outside flower, swinging loose on long filaments to release pollen grains easily

43
Q

How does the stigma differ in an insect vs wind pollinated flower?

A

🦟 - inside flower, sticky so pollen grains stick to it when an insect brushes past
🌬 - outside flower, feathery t catch drifting pollen grains

44
Q

When does cross-pollination occur?

A

Cross-pollination occurs when the pollen from one plant is transferred to the stigma of another plant of the same species

45
Q

Why do most plant carry out cross-pollination?

A

This is the way most plants carry out pollination as it improves genetic variation

46
Q

What is self-pollination?

A

Occasionally, the pollen from a flower can land on its own stigma or on the stigma of another flower on the same plant – this is known as self-pollination

47
Q

What is a disadvantage of self-pollination?

A

Self-pollination reduces genetic variety of the offspring as all the gametes come from the same parent (and are therefore genetically identical)

48
Q

Why is a lack of variation in offspring a disadvantage?

A

Lack of variation in the offspring is a disadvantage if environmental conditions change, as it is less likely that any offspring will have adaptations that suit the new conditions well

49
Q

What is a disadvantage of cross-pollination?

A

On the other hand, cross-pollination relies completely on the presence of pollinators and this can be a problem if those pollinators are missing (eg the reduction in bee numbers is of great importance to humans as bees pollinate a large number of food crops) – this doesn’t apply to wind-pollinated plants

50
Q

When does fertilisation occur?

A

Fertilisation occurs when a pollen nucleus fuses with an ovum nucleus in the ovule

51
Q

How does the pollen travel to the ovary, if it can’t move?

A

As the pollen has no ‘tail’ to swim to the ovary of a plant, in order to reach the ‘female’ nucleus in the ovary it has to grow a pollen tube

52
Q

What condition is necessary for the pollen to grow a pollen tube?

A

This only happens if the pollen grain has landed on the right kind of stigma (i.e. of the same species as the flower the pollen came from)

53
Q

What happens once the pollen has grown a pollen tube?

A

The nucleus inside the pollen grain slips down the tube as it grows down the style towards the ovary

54
Q

What does the ovary contain?

A

The ovary contains one or more ovules which each contain an ovum with a female nucleus that a male pollen nucleus can fuse with

55
Q

What happens once the nucleus has travelled down the pollen tube?

A

the nuclei (pl) have joined together, that ovule has been fertilised and a zygote has been formed

56
Q

What happens to the zygote in the ovary? (plants)

A

The zygote will start to divide and eventually form a seed within the ovule

57
Q

Why do different fruits have different numbers of seeds?

A

As different plants have different numbers of ovules, this explains why different fruits (which develop from the ovary) have different numbers of seeds (which develop from the ovules)

58
Q

What is germination?

A

Germination is the start of growth in the seed

59
Q

What three factors are required for successful germination?

A
  • water
  • oxygen
  • warmth
60
Q

Why is water needed for germination?

A

allows the seed to swell up and the enzymes in the embryo to start working so that growth can occur

61
Q

Why is oxygen needed for germination?

A

so that energy can be released for germination

62
Q

Why is warmth needed for germination?

A

germination improves as temperature rises (up to a maximum) as the reactions which take place are controlled by enzymes

63
Q

What factor does not make a difference for germination?

A

As carbon dioxide is not necessary for germination but also does not inhibit it, it makes no difference whether it is present or not

64
Q

How could you set up an experiment to investigate germination?

A
  • Set up 4 boiling tubes each containing 10 cress seeds on cotton wool
  • Set each test tube as shown in diagram below
  • Leave tubes in set environment for a period of time: A, B and C incubated at 20°C; D placed in a fridge at 4°C
  • Compare results and see which tube has the greatest number of germinated seeds
65
Q

Will a seed germinate if it has 1 factor present e.g oxygen but not any others?

A

NO - needs all 3 factors

Biology IGCSE CIE Extended (22 decks)

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