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Biology > 2 Reproduction in humans > Flashcards

2 Reproduction in humans Flashcards

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1
Q

What is sexual reproduction?

A

It is reproduction involving the fusion of male and female gametes to form a zygote.

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2
Q

What are the characteristics of sexual reproduction?

A
  • Gametes (sperm and egg cells) are produced.
  • The male gamete (sperm) is transferred to the female gamete (egg cell).
  • Fertilisation must occur - the sperm fuses with the egg.
  • A zygote is then formed.
  • This zygote then undergoes cell division (mitosis).
  • It then develops into an embryo.
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3
Q

What is an embryo?

A

A multicellular structure formed by division of a zygote.

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4
Q

How are the offspring in relation to genes created by sexual reproduction?

A

They show a great deal of genetic variation as a result of both gamete production and fertilisation.

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5
Q

What is fertilisation?

A

The fusion of male and female gametes to form a zygote.

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6
Q

What are the main characteristics of fertilisation?

A
  • Sperm approach the egg.
  • The sperm penetrates the cell membrane; the sperms nucleus enters.
  • The sperm nucleus and egg nucleus fuse.
  • An extra membrane (the fertilisation membrane) now prevents any more sperm from entering.
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7
Q

What is a gamete?

A

Male and female sex cells, formed by meiosis.

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8
Q

What are the female gametes?

A

Ova or egg cells.

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9
Q

What is sperm?

A

Male gamete of an animal, with a tail for swimming and a head containing the nucleus.

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10
Q

What are the male gametes?

A

Sperm

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11
Q

What is ovum (ova)?

A

The female gamete.

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12
Q

What is a zygote?

A

A single cell resulting from the fusion of a male and female gamete.

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13
Q

What is asexual reproduction?

A

It is reproduction that does not involve fusion of gametes. New organisms are produced by part of an organism separating into a single part.

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14
Q

What are the characteristics of asexual reproduction?

A
  • Cells in one part of the body divide by mitosis to form a structure that breaks away from the parent body and grows into a new organism.
    -The cells of the new individual are produced by mitosis from just one cell in the body of an adult.
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15
Q

How are the offspring in relation to genes created by asexual reproduction?

A

They are genetically identical - they have exactly the same genes.

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16
Q

Why is asexual useful?

A

It is are useful to a species when the environment in which its lives is relatively stable. Asexual reproduction will produce offspring that are also well adapted if the species itself is well adapted. However, if the environment changes significantly, then all the individuals will be affected equally by the change. The change might be so dramatic that it could cause all the species in that area to die out.

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17
Q

What are the main differences between asexual and sexual reproduction?

A
  • Asexual reproduction involves only one parent organism while sexual reproduction involves two.
  • Offspring produced through asexual reproduction are genetically identical or nearly identical to the parent organism, resulting in limited genetic diversity. While in sexual reproduction, offspring produced through sexual reproduction inherit a combination of genetic material from both parents, resulting in greater genetic diversity.
  • Common methods of asexual reproduction include binary fission, budding, spore formation, and fragmentation. However, sexual reproduction involves the fusion of gametes (sperm and egg cells) and is characterised by processes such as fertilisation.
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18
Q

Where are the male gametes produced?

A

Sperm is produced in the testes.

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19
Q

Where are the female gametes produced?

A

Eggs are produced in the ovaries.

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20
Q

What is mitosis?

A

It is a type of cell division that produces diploid body cells for growth and repair of tissues.

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21
Q

In what kind of reproduction do cells divide by mitosis?

A

Asexual reproduction.

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22
Q

What is meiosis

A

Type of cell division that produces haploid cells (gametes).

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23
Q

In what kind of reproduction do cells divide by meiosis?

A

Sexual reproduction.

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24
Q

What is a diploid cell?

A

Number of chromosomes found in body cells. Diploid cells contain both chromosomes of each homologous pair. Therefore, it contains 46 chromosomes.

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25
Q

What is a haploid cell?

A

Number of chromosomes found in gametes. Haploid cells contain one chromosome from each homologous pair.

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26
Q

How is sperm adapted for its function?

A
  • They have a flagellum which helps for them to swim.
  • Their mid-piece contains mitochondria to release energy for movement.
  • Their head contains a sac of enzymes to penetrate membrane around egg.
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27
Q

What is external fertilisation?

A
  • When female animals release their eggs into the water and the sperm then swim through the water to fertilise the eggs.
  • This is called external fertilisation as it takes place outside of the body.
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28
Q

What is internal fertilisation?

A

It is when birds and mammals ejaculate their sperm in a special fluid into the bodies of females. Internal fertilisation then takes place inside the females body. Fertilisation is much more likely as there are no external factors to prevent the sperm from reaching the eggs.

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29
Q

Why do zygotes undergo mitosis?

A

Each zygote that is formed must divide to produce all the cells that will make up the adult. All these cells must have the full number of chromosomes, so the zygote divides repeatedly by mitosis.

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30
Q

Why must meiosis happen?

A

All cells in the human body have 46 chromosomes in their nucleus. Meiosis must happen to produce gametes, which contain 23 chromosomes - so, fertilisation can then take place, and the two gametes can fuse to form a zygote.

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31
Q

What is differentation?

A

The process taking place during the development of an embryo, where cells become specialised to carry out particular functions.

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32
Q

What kind of cells differentiate?

A

Bone cells, nerve cells and muscle cells.

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33
Q

How does sexual reproduction happen (males)?

A
  • During sexual intercourse, sperm pass along the sperm duct and are mixed with a fluid called semen.
  • Semen, is ejaculated through the urethra into the vagina of the female.
  • The sperm then begins to swim towards the oviducts.
34
Q

How does an egg end up in the oviduct?

A

Through ovulation.

35
Q

What is ovulation?

A

It is when an egg is released into an oviduct from one of the ovaries. This usually happens on the 14th day of the menstrual cycle.

36
Q

How does sexual reproduction happen (females)?

A
  • If an egg is present in the oviduct, then it may be fertilised by sperm introduced during intercourse.
  • The zygote formed will begin to develop into an embryo, which will implant into the lining of the uterus.
  • The embryo will then develop a placenta.
37
Q

What is the placenta?

A

It is an organ in mammals which contains blood vessels of the embryo in close proximity to blood vessels of the mother. Allows exchange of gases, nutrients, waste products and other substances between the maternal blood and the embryo’s blood.

38
Q

What is the function of the placenta?

A

It allows the embryo to obtain materials such as oxygen and nutrients from the mothers blood.
- It also allows the embryo to get rid of waste products such as urea and carbon dioxide, as well as anchoring the embryo in the uterus.
- It also secretes female hormones, like progesterone which maintain the pregnancy and prevent the embryo from aborting.

39
Q

Where does early development occur in the female reproductive organs?

A

In the uterus.

40
Q

How is the placenta adapted for its function?

A
  • Large Surface Area: The placenta has a large surface area due to its numerous villi (finger-like projections). This large surface area facilitates efficient exchange of substances between the maternal and fetal bloodstreams.
  • Rich Blood Supply: The placenta has many blood vessels, like tiny tubes, which helps in the transfer of important substances such as oxygen, sugar, and protective antibodies between the mother’s blood and the baby’s blood.
  • Selective Permeability: The placental membrane is selectively permeable, which means it allows some substances to pass through while blocking others. This adaptation prevents harmful substances, such as certain toxins and pathogens, from reaching the fetus while allowing essential nutrients and gases to pass.
41
Q

What are some labelled pictures of the male reproductive hormones?

A
42
Q

What are some labelled pictures of the female reproductive hormones.

A
43
Q

What is the embryo?

A

The multicellular structure formed by the division of a zygote.

44
Q

What is progesterone?

A

Female sex hormone made in the ovaries, and later by the placenta.

45
Q

What is the function of progesterone?

A

Progesterone causes further thickening of the uterus lining during the menstrual cycle and maintenance of the lining during pregnancy. A drop in progesterone levels stimulates menstruation.

46
Q

What is the amnion?

A
47
Q

When is the amnion secreted?

A

During pregnancy.

48
Q

What does the amnion secrete?

A

Amniotic fluid.

49
Q

What does the amniotic fluid do?

A

It protects the developing embryo against sudden movements and bumps.

50
Q

When does the embryo turn into a fetus?

A

When it becomes recognisably human.

51
Q

What is a fetus?

A

It is unborn offspring of a mammal, in particular an unborn human embryo more than 2 months after fertilisation, when it show recognisable human features.

52
Q

What are the three stages to the birth of a child?

A
  • Dilation of the cervix.
  • Delivery of the baby.
  • Delivery of the afterbirth.
53
Q

What is puberty?

A

A time when developmental changes take place in boys and girls that lead to sexual maturity.

53
Q

What two developments do puberty involve?

A
  • The first is the gametes (eggs and sperm) start to mature and be released.
  • The second is that the bodies of both sexes adapt to allow reproduction to take place.
54
Q

What is testosterone?

A

It is the male sex hormone, made by the testes. It is responsible for the development of the male secondary sex characteristics.

55
Q

What does testosterone control?

A

The development of the male secondary sexual characteristics.

56
Q

What are secondary sexual characteristics?

A

Changes taking place in the bodies of boys and girls at puberty.

57
Q

What are the male secondary sexual characteristics?

A
  • Sperm production starts.
  • Growth and development of male sexual organs.
  • Growth of armpit and pubic hair, and chest and facial hair.
  • Increase in body mass.
  • Voice breaks.
  • Sexual ‘drive’ develops.
58
Q

What is oestrogen?

A

The female sex hormone secreted by the ovaries. Controls the development of the female sex characteristics and the repair of the uterine lining during the menstrual cycle.

59
Q

What does oestrogen control?

A

The development of the female secondary sexual characteristics.

60
Q

What are the female secondary sexual characteristics?

A
  • The menstrual cycle begins, and eggs are released by the ovaries every month.
  • Growth and development of female sexual organs.
  • Growth of armpit and pubic hair.
  • Increase in body mass.
  • Voice deepens without sudden ‘breaking’.
  • Sexual ‘drive’ develops.
  • Breasts develop.
61
Q

Between what ages does puberty take place in girls?

A

11 - 14 years old.

62
Q

Between what ages does puberty take place in boys?

A

13 - 16 years old.

63
Q

What is the menstrual cycle?

A

The monthly cycle of events preparing a woman’s uterus for the possible implantation of a fertilised egg. Controlled by hormones from the pituitary gland.

64
Q

What is ovulation?

A

The release of an ovum from a follicle in the ovary.

65
Q

What does oestrogen do in terms of the menstrual cycle?

A
  • Causes the lining of the uterus to build up. Days 6 - 13.
  • Stimulates another hormone which leads to ovulation.
66
Q

What does progesterone do in terms of the menstrual cycle?

A
  • Maintains the lining of the uterus. Days 15-28.
  • Inhibits the release of further eggs by stopping other hormones from being produced.
  • Completes the development of the uterus lining by thickening and maintaining it, ready for the fertilised egg to sink into it and develop into an embryo.
67
Q

How long does the menstrual cycle last for?

A

28 days.

68
Q

What happens from days 1-5 in the menstrual cycle?

A

Bleeding as uterus lining is shed.

69
Q

What happens from days 6 - 13 in the menstrual cycle?

A

New uterus lining develops, this is due to the oestrogen hormone

70
Q

What happens on day 14 of the menstrual cycle?

A

Ovulation.

71
Q

From which days is the egg in the oviduct?

A

Days 15 - 19

72
Q

From which days can the egg be fertilised?

A

Days 15 - 17

73
Q

When does the egg die if not fertilised?

A

Days 18 - 20

74
Q

What happens from day 15 - 28 in the menstrual cycle?

A

Blood supply develops in new uterus lining. This is due to the progesterone hormone.

75
Q

What is a function of the menstrual cycle when an egg is fertilised?

A

One function of the cycle is to control the development of the lining of the uterus, so that if the egg is fertilised, the lining will be ready to receive the fertilised egg.

76
Q

What is a function of the menstrual cycle when an egg is not fertilised?

A

The lining of the uterus is lost from the woman’s body as the flow of menstrual blood and sales of the lining, called a period.

77
Q
A
78
Q
A
79
Q
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Biology (22 decks)

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