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IGCSE Biology > Reproduction and Inheritance > Flashcards

Reproduction and Inheritance Flashcards

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1
Q

What are the adaptations of insect pollinated plants?

A
  • Brightly coloured petals: attract insects.
  • Scented flowers and nectaries: attract insects.
  • Big and sticky pollen grains: attach to insects as they go from plant to plant.
  • Sticky stigmas: any pollen picked up by insect will stick to the stigma.
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2
Q

Adaptations or wind pollinated plants?

A
  • Small, dull petals: do not need to attract insects.
  • no scented flowers or nectaries ^^^^^^^^^^^
  • small and light pollen grains: can easily be picked up by the wind.
  • long filaments that hang anthers out of plant: pollen can be blown away by wind.
  • large feathery stigma: catches pollen carried by the wind.
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3
Q

Process of seed and fruit formation

A

1) pollen grain lands on the stigma of a flower by wind or insects.
2) causes a pollen tube to grow out of the grain and down to the style and into the ovary to meet ovule.
3) The nucleus of a male gamete travels down the pollen tube and meets the ovules in the ovary= FERTILISATION.
* ovary—> fruit * ovule—> seed.

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4
Q

What conditions are needed for a seed to germinate?

A

1) water- taken in my micropyle to burst the testa and activate the enzymes needed to break down food reserves in the cotyledon—> first root grows down into the soil.
2) oxygen- needed for respiration—>energy for the seed’s growth.
3) temperature: to give the exudes in the seed their optimum temperature to work.

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5
Q

What is germination?

A

The change of a seed into a seedling or plant.

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6
Q

What is seed dormancy?

A

The point where the seed has very little metabolic activity.

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7
Q

What are the two ways that plants can reproduce?

A

Asexually by natural methods: e.g runners
Or
Asexually by artificial methods: e.g. cuttings

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8
Q

How do plants reproduce naturally?

A

1) A horizontal stem grows along the surface of the ground.
2) At certain points, small roots (adventitious roots) grow into the soil.
3) These soon take over the function of the main root of the plant. They hold the young plant in the soil and absorb water and nutrients from the soil.
4) eventually the horizontal root dies and a new plant is established.
* for this, all plant cell divisions have taken place by mitosis.

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9
Q

How can plants be reproduced artificially by cuttings?

A

A small length of stem is cut from the main plant and placed directly into soil or in water.
* just like natural methods, all plant cell divisions are by mitosis so the plant is identical to the parent.

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10
Q

What is the function of the bladder in the male reproductive system?

A

Stores urine produced by kidneys which is then released at intervals out of the body via the urethra.

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11
Q

What is the function of the prostate gland in the male reproductive system?

A

This is where the vas deferens meets the urethra. It produces semen, the fluid which sperm swim in.

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12
Q

What is the function of the testis in the male reproductive system?

A

The site of sperm production as a result of meiotic cell division inside the small tubules.
It only happens below body temperature, which is why the testes are suspended in the scrotum to keep them cool.

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13
Q

What is the function of the scrotum in the male reproductive system?

A

A sack of skin that suspends the testes outside the abdominal cavity.

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14
Q

What is the function of the urethra in the male reproductive system?

A

Carries urine or sperm from the body.

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15
Q

What is the function of the penis in the male reproductive system?

A

Contains erectile tissue and is used to introduce sperm into the vagina during sexual intercourse. The sperm are carried along the urethra during ejaculation.

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16
Q

What is the function of the vas deferens in the male reproductive system?

A
  • stores sperm before ejaculation

- sperm is passed with semen into the urethra.

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17
Q

What is the function of the pubic bone in the male reproductive system?

A

Forms part of the pelvic girdle.

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18
Q

What is the function of the vagina in the female reproduction system?

A

Where sperm is deposited. It is the route taken by the baby during birth.

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19
Q

What is the function of the cervix in the female reproduction system?

A

Entrance to the uterus thorough which the sperm must swim if they are to fertilise an egg.

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20
Q

What is the function of the ovary in the female reproduction system?

A

Site of egg and hormone production as part of the menstrual cycle.

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21
Q

What is the function of the uterus’ muscular wall in the female reproduction system?

A

Stretches to allow the growth of an embryo and later on, pushes the foetus out during labour.

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22
Q

What is the function of the oviduct in the female reproduction system?

A

Carries the egg released by the ovary towards the uterus (2-4 days)

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23
Q

What is the function of the lining of the uterus in the female reproduction system?

A

Provides a site of development for the placenta.

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24
Q

What is the function of the placenta in the female reproduction system?

A

An organ which allows the exchange of material between the mother’s blood and baby’s blood.

25
Q

What happens on day one of the menstrual cycle?

A

The day the woman sheds the lining of her uterus= menstruation.

26
Q

What is the purpose of the hormone oestrogen and where is it produced?

A

This is produced by the follicle cells in the ovary. (First 14 days= high levels of oestrogen)

It’s function is to form a new lining in the uterus.

27
Q

What is ovulation?

A

The release of an egg from its ovary. It is moved by the cilia hairs to the oviduct

28
Q

What is the function of the hormone progesterone? What is it triggered by?

A

This is triggered by the hormone LH.

It promotes the further growth of the uterus lining.

29
Q

What happens if fertilisation doesn’t take place?

A

The released egg travels along the oviduct for a period of 14 days. It is eventually shed with the lining of the uterus at the start of the next cycle.

30
Q

What is implantation? And why does it occur ?

A

Implantation occurs because the hormone HCG prevents the shedding of the uterus lining. This makes it thick and allows the embryo to attach and implant itself. When this happens a placenta is formed.

31
Q

What is exchange between the mother’s blood and the baby’s blood?

A

The developing embryo requires oxygen, glucose, amino acids, vitamins, minerals and ions.
But it also needs to get rid of waste products eg carbon dioxide and urea.

32
Q

What is the developing embryo protected by?

A

Amniotic fluid held in by the amniotic membrane.

It’s acts as a cushion or shock absorber so protect the baby from knocks and bumps from the body of the mother.

33
Q

What are male secondary characteristics and what causes these developments?

A
  • Pelvis remains narrow.
  • no development of breasts.
  • greater proportion of body mass converts to fat.
  • hair develops in pubic region and face.
  • voice box grows larger= deeper voice
  • these are all developed as a result of the hormone testosterone*
34
Q

What are female secondary characteristics?

A
  • pelvis widens
  • breasts grow with fat deposits (also provides milk for baby)
  • greater proportion of body mass converts to fat.
  • hair develops in pubic region.
  • oestrogen and progesterone cause these developments*
35
Q

What does the nucleus of a cell contain?

A

Chromosomes, which are where genes are located.

36
Q

What is a gene?

A

A section of a molecule of DNA. It is what codes for a specific protein.

37
Q

What does a DNA molecule have?

A

1) Two polynucleotide strands that are coiled to form a double helix.
2) Strands that are linked together.
3) Bases called Adenine (A) which links with Thymine (T), Cytosine (C) which links with Guanine (G)

38
Q

What are different forms of the same gene called? And what do they cause?

A

Alleles and they are what cause differences in inherited characteristics.

39
Q

What does a dominant allele mean?

A

Only one of these alleles are needed for its characteristic to appear.

40
Q

What does recessive mean?

A

Both alleles need to be like this in order for the characteristic to appear.

41
Q

What does it mean to be Homozygous

A

When both alleles in a pair are the same.

42
Q

What does it mean to heterozygous

A

When two alleles in a pair are different.

43
Q

What does phenotype mean?

A

Physical characteristics of an organism. (What you look like)

44
Q

What does a genotype mean?

A

The collection of genes inside a nucleus.

45
Q

What does codominance mean?

A

When both alleles working in the combination affect your phenotype

46
Q

What is a monohybrid inheritance?

A

The inheritance of one gene.

47
Q

Which chromosome controls the sex of a person?

A

The 23rd chromosome.
XX= female
XY= male.

48
Q

Describe the process of cell division by mitosis

A

1) a diploid cell (23 chromosomes) duplicates its genetic material.
2) chromosomes align themselves in the centre of the cell
3) the cell splits in half - becoming a haploid
4) the two cells produced are genetically identical. (Have the same chromosomes)

49
Q

When does mitosis happen?

A

During the growth, repair, cloning and asexual reproduction.

50
Q

Describe cell division by meiosis

A

1) a diploid cell (23 chromosomes) duplicates its genetic material.
2) chromosomes align in the centre of the cell.
3) the cell splits in half. (Haploid)
4) the cells split in half again to form cells, each with half the genetic information of a haploid.
5) each of the four cells are genetically unique gametes.

51
Q

Why are offspring genetically different to their parents?

A

Because gametes contain a random selection of genetic information from each parent. This means that the fertilised egg will be a mix of different genotypes.

52
Q

In human cells, what is the diploid and haploid number of chromosomes?

A

46- diploid

23- haploid

53
Q

Variations within species can be?

A

1) genetic (e,g eye colour)
2) environmental (e.g sun giving a tan)
3) combination of both (e,g, obesity, sunburn)

54
Q

What are mutations?

A

These are rare and random changes in genes that are passed on to descendant cells on the chromosome during cell division.

55
Q

What is the process of evolution by natural selection?

A

1) A mutation is brought about by either meiotic cell division or the random process of fertilisation. This brings variation amongst species.
2) these can bring about advantages and disadvantages to species, making access to resources either easier or harder.
3) because of these +/-, there is competition between species.
4) those with + survive and reproduce, producing offspring with their advantages and those that were weaker die out as they lose in the ‘survival of the fittest’

56
Q

How can mutations be harmful or beneficial or neutral?

A

Harmful: more visible = easily caught by prey.
Beneficial: camouflaged= not seen as easily
Neutral: change in eye colour

57
Q

What is the problem with bacteria becoming increasingly resistant to antibiotics?

A

By bacteria developing mutations, they are becoming resistant to many antibiotics. This means that they have an increased chance of survival and therefore live longer and reproduce offspring that are also resistant. This creates a problem to organisms that are affected by the mutated organism as antibiotics will not work on them. Therefore, new antibiotics need to be made and this requires time and money.

58
Q

In what ways can the incidence of mutations be increase by?

A

Ionising radiation: gamma rays, X-rays and ultraviolet rays.
Some chemical mutagens: chemicals in tobacco.

IGCSE Biology (11 decks)

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