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IGCSE Biology > Chapter 16: Reproduction > Flashcards

Chapter 16: Reproduction Flashcards

(incomplete)

1
Q

Define asexual reproduction

A

the process resulting in the production of genetically identical offspring from one parent.

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2
Q

What does asexual reproduction result in?

A

genetically identical offspring who are clones of their parents

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3
Q

Does asexual reproduction involve gametes?

A

no

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4
Q

How do bacteria reproduce?

A

They reproduce in the process called binary fission.

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5
Q

How does binary fission take place?

A

This involves one bacterium copying its DNA and then dividing it into two to produce an exact copy of itself.

This is an example of asexual reproduction

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6
Q

How do fungi reproduce?

A

They reproduce by producing spores.

The sporangium bursts open dispersing spores into the air and when it lands on an area of favourable conditions, it germinates and grows into an identical fungus.

Another example of asexual reproduction.

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7
Q

What are the ways in which asexual reproduction can take place in plants?

A
  1. Runners -> production of side branches with plantlets on them (e.g. strawberries)
  2. Bulbs and tubers -> develops underground food storage organs that develop into following year’s plants (e.g. potato tubers)
  3. Cuttings -> growth through plant hormones
  4. Tissue culture -> small scrapings from parent plant, grown in agar jelly with plant hormones and nutrients
  5. Artificial cloning
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8
Q

Advantages of asexual reproduction.

A
  1. no mate needed
  2. no gametes needed
  3. population increases rapidly
  4. population can exploit a habitat rapidly
  5. all favourable characteristics are passed onto offspring
  6. possible for an isolated individual
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9
Q

Disadvantages of asexual reproduction.

A
  1. no variation in population
  2. may be only suited to one habitat
  3. unlikely to adapt to environment as it changes
  4. if parent has no resistance to a disease, neither will the offspring.
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10
Q

Define sexual reproduction.

A

process involving the fusion of two gametes to form a zygote.

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11
Q

What type of offspring does sexual reproduction produce?

A

genetically different offspring

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12
Q

What does sexual reproduction involve?

A

The production of gametes (sex cells) which are produced in the process of meiosis

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13
Q

How is a zygote formed?

A

When the nuclei of the male and the female gametes come together and fuse.

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14
Q

Define fertilisation

A

The fusion of the nuclei from two gametes normally from the same species.

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15
Q

What are the male and female gametes in flowers?

A

male: pollen grains
female: ovules

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16
Q

What are the male and female gametes of animals?

A

male: sperm
female: egg

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17
Q

How many chromosomes are there in somatic cells?

A

46 chromosomes (23 pairs)

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18
Q

How many chromosomes are there in human gametes?

A

23 chromosomes. They are haploid.

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19
Q

Advantages of sexual reproduction

A

Offspring are unique
Species can adapt to new environments
More likely to survive a disease outbreak

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20
Q

Disadvantages of sexual reproduction?

A

Time and energy is required to find a mate
Slow
Not possible for an isolated individual

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21
Q

Name the male and female organs of the plant.

A

Stamen (male organs)
Carpels (female organs)

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22
Q

Name the parts of the stamen.

A

Anther
Filament

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23
Q

Name the parts of the carpel.

A

Stigma
Style
Ovary
Ovule

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24
Q

Function of the sepal

A

Protects unopened flower

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25
Q

Function of petals

A

Attracts pollinators, e.g insects

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26
Q

Function of stamen

A

Male organs of the flower consisting of the anther attached to a filament

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27
Q

Function of anther.

A

Production of pollen, male gametes

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28
Q

Function of stigma.

A

Located at the top of the female organs. Collects pollen grains

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29
Q

Function of ovary

A

Produces ova (eggs)

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30
Q

What is the carpel

A

the collective term for the female structures

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31
Q

How do wind pollinated plants transfer pollen?

A

let their pollen blow in the wind and hope they reach another plant for pollination

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32
Q

How do insect pollinated plants transfer pollen?

A

They use insects and other animals to carry their pollen grains to other plants

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33
Q

How are insect pollinated flowers adapted for pollination?

A

Large and brightly coloured petals
Highly scented with nectar
Moderate pollen grain numbers - insects transfer pollen grains efficiently
Sticky to allow attachment to insects
Anthers inside the flower (so the brush against insects and attach pollen while insects drink nectar)
Sticky stigma inside the flower.

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34
Q

How are wind pollinated flowers adapted for pollination?

A

Small, dull-coloured petals
No scent or nectar
Large numbers of pollen (most pollen grains don’t meet another flower)
Smooth, light and aerodynamic to be carried by the wind
Anthers loosely attached to the outside of the flower to aid in easy release
Feathery stigma outside the flower to catch drifting pollen

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35
Q

Define pollination.

A

Pollination is the transfer of pollen grains from the anther to the stigma

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36
Q

What type of offspring does self-pollination produce?

A

Identical offspring

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37
Q

Examples of self-pollinated plants.

A

wheat
beans
tomatoes
lettuce

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38
Q

Effects of self-pollination

A

higher chance of successful pollination
small numbers of pollen
higher chance of fertilisation and seed formation
lower variation in the offspring
lower ability to adapt to environmental change

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39
Q

Examples of cross-pollinated plants

A

apples
pear
strawberries
dandelions

40
Q

Effects of cross-pollination

A

lower chance of successful pollination
large amount of pollen
lower chance of fertilisation
higher variation in offspring
higher ability to adapt to environmental change

41
Q

Describe the process of fertilisation in plants.

A
42
Q

Define germination.

A

The process by which a seed begins to develop into a new plant

43
Q

What is required for germination to occur?

A

Water: Causes the seed to swell and the embryo to begin growing

Oxygen: Aerobic respiration

Warmth: Increases growth rate and enzymatic activity

44
Q

How is water absorbed in a seedling?

A

Water is absorbed firstly through the micropyle and then through the testa as a whole.

Once the radicle has emerged, it will absorb water from the soil through the root hairs.

45
Q

State the uses of water in a seedling.

A

activate enzymes in the seed

conversion of stored starch to sugar and proteins to amino acids

transport sugar in solution from cotyledons to growing regions

expand vacuole of new cells causing root and shoot to grow and leaves to expand

transport salts

photosynthesis

maintain turgor pressure

46
Q

Define reproduction.

A

the process of producing new individuals

47
Q

What are the male and female gametes in humans?

A

sperm (male)
ova/egg (ovum)

48
Q

label the parts of the male reproductive system.

A
49
Q

State the function of testes

A

The gland which produces sperms and the male sex hormone testosterone

50
Q

State the function of scrotum

A

The sac containing the testicles

51
Q

State the function of sperm ducts

A

two muscular tubes connected to a testis. They carry the sperms from the testis to the urethra

52
Q

State function of prostate gland

A

secretes a nutritive fluid to the sperms to form a mixture called semen

53
Q

State the function of urethra (male)

A

The tube inside the penis that carries semen and urine out of the body

54
Q

State the function of penis

A

ejaculates semen into the vagina during sexual intercourse

Passes urine out of the body

55
Q

State the function of seminal vesicles

A

a gland similar to the prostate gland which secretes fluid for the sperm cells to feed on.

56
Q

Label the parts of the female reproductive system.

A
57
Q

State the functions of ovaries.

A

the glands which produce eggs

58
Q

State the function of oviducts

A

the two tubes one connected to each ovary

The site of fertilisation and the pathway for the egg to travel to the uterus

59
Q

State the function of uterus

A

A muscular bag where a foetus develops during pregnancy

60
Q

State the function of cervix

A

A ring of muscular tissue which separates the vagina from the uterus.

Keeps the foetus in the uterus during pregnancy

61
Q

State the function of vagina

A

receives the sperm during sexual intercourse

62
Q

Draw and label the sperm cell.

A
63
Q

How is the sperm adapted for its function?

A
  1. Tip of the cell carries acrosome which secretes enzymes capable of digesting a path into an egg cell, through its jelly coating, to allow the two nuclei to fuse
  2. The cytoplasm contains many mitochondria to carry out respiration
  3. This provides the cell energy to make the tail move and propel the sperm forward
64
Q

Draw and label the egg cell.

A
65
Q

How is the egg cell adapted for its function?

A
  1. Surrounded by a jelly coat to protect the contents of the cell.
  2. Jelly coat also prevents more than one sperm from entering and fertilising the egg
  3. Has a large amount of cytoplasm rich in fats and proteins –> acts as an energy store for growth should the egg be fertilised
66
Q

Describe the process of fertilisation in humans.

A
  1. Sperms swim through the cervix and into the uterus by wriggling movements of their tails
  2. They pass through the uterus and enter the oviduct
  3. If there is an ovum in the oviduct, one of the sperm may bump into it and stick to its surface
  4. Acrosome secretes enzymes which digest part of the egg membrane
  5. Sperm enter the cytoplasm of the ovum and male nucleus fuses with the female nucleus.
67
Q

How does the embryo develop?

A

The zygote first divides into two cells.

Each of these divides again producing four cells.

The cells continue to divide in this way to produce a solid ball of cells.

This is the early stage of the development of the embryo

68
Q

Describe the process of implantation.

A

The early embryo travels down the oviduct to the uterus.

This process is called implantation.

69
Q

How is the foetus formed?

A

The embryo continues to grow and produce new cells that form tissues and organs.

After 8 weeks, all organs are formed and the embryo is called a foetus

70
Q

What is the first organs to be formed?

A

The heart, which pumps blood around the body of the embryo.

71
Q

State the function of the amniotic sac?

A

As the embryo grows, the uterus enlarges to contain it.

Inside the uterus, the embryo becomes enclosed in a fluid-filled sac called the amnion sac.

This sac protects it from damage and prevents unequal pressures from acting on it.

The fluid is call amniotic fluid

72
Q

State the function of the placenta.

A

Where the oxygen and food needed to keep the embryo alive are obtained from the mother’s blood through this structure.

It also prevents some harmful substances in the mother’s blood from reaching the baby.

The placenta is the connection between the embryo and its mother and anchors the embryo to the wall of the uterus via the umbilical cord.

The placenta also produces hormones including oestrogens and progesterone, which are essential to keep the uterus in good condition and stimulate the development of milk-producing tissues in the mother.

73
Q

What is the umbilical cord.

A

The placenta becomes closely attached to the lining of the uterus and is attached to the embryo by a tube called the umbilical cord.

Allows dissolved nutrients and oxygen to move from the mother to the embryo and waste materials and CO2 to move from the embryo to the mother.

74
Q

What dangerous substances can pass through the placenta?

A

alcohol
nicotine
pathogens like rubella and HIV.

The above can affect the developing foetus.

75
Q

How do materials move between the maternal and foetal circulation?

A

By diffusion. This ensures that there is no mixing of maternal and foetal blood.

76
Q

Where is testosterone produced?

A

in the testes

77
Q

What secondary sexual characteristic s are produced by testosterone?

A

Facial and body hair growth
Pubic hair
Increased muscle mass
Deepened voice

78
Q

What gametes are produced by testosterone?

A

Sperm cells

79
Q

Where is oestrogen produced?

A

Ovaries

80
Q

What secondary sexual characteristics are produced by oestrogen?

A

Breast formation
Deepened voice (gradual)
Pubic hair
Hips widen

81
Q

What gametes are produced by oestrogen

A

Ovulation (ovules are produced)
Menstrual cycle

82
Q

What is the menstrual cycle?

A

A recurring process which completes every 28 days approx.

This process is controlled by hormones that peak at different times during the cycle to trigger the different events.

It is divided into 3 phases:

Follicular phase - where the follicle is matured or ripened in the ovary

Ovulatory phase - where the follicle is released from the ovary

Luteal phase - lining of the uterus thickens to prepare for the ovum to implant should it be fertilised.

83
Q

What happens if the egg does not get fertilised?

A

If fertilisation does not occur, then the lining of the uterus is released in the event known as menstruation (menses), indicating the start of a new cycle.

84
Q

State the role of the follicle stimulating hormone in the menstrual cycle.

A

Causes the egg to mature
Stimulates the ovaries to release oestrogen

85
Q

Where is FSH produced?

A

In the pituitary gland in the brain

86
Q

State the role of oestrogen in the menstrual cycle.

A

Stops FSH production so that only one egg matures each cycle.

Repairs and thickens the uterus lining.

Stimulates the pituitary gland to release Lh

87
Q

State the role of LH in the menstrual cycle.

A

Triggers ovulation

88
Q

State the role of progesterone in the menstrual cycle.

A

Maintains the lining of the uterus in the middle part of the cycle and during pregnancy

89
Q

What are sexually transmitted infections?

A

Infections that are transmitted via body fluid through sexual contact.

These include bacteria like Chlamydia and viruses like HIV

90
Q

What is HIV?

A
  1. an example of an STI
  2. present in the bodily fluids of infected people such as blood and semen and can be transmitted during sexual intercourse
  3. Babies born to HIV carries may become infected with it since the virus can cross the placenta
  4. If HIV antibodies are present in the blood, the person is said to be HIV positive.
91
Q

What is the effect of HIV on the immune system?

A
  1. people suffer mild flu-like symptoms and might not know that they are infected.
  2. HIV attacks a particular type of lymphocyte decreasing the number of these in WBCs in the body
  3. These lymphocytes become less effective which make the person more vulnerable to common pathogens
  4. As the HIV progresses, the person becomes more immune-compromised often leading to them dying from an infection which their body is unable to fight.
92
Q

What is AIDS caused by?

A

HIV transmitted by direct infection of blood as well as other body fluids.

Drug users who share needles contaminated with infected blood have a high risk of contracting the diseases

When HIV starts to attack the patient’s immune system, this has resulted in AIDS

93
Q

How is HIV transmitted?

A

Unprotected sexual intercourse with an infected person

Drug use involving the sharing of needles with an infected person

Transfusion of infected blood

Infected mother to foetus

Feeding baby with milk from an infected mother

Unsterilised surgical instruments

94
Q

How do you control the spread of STIs?

A
  1. Avoid having sexual intercourse with an infected person
  2. Use condoms or femidoms
  3. Limiting the number of sexual partners
  4. Get screened for the infection and make partners aware if the test returns positive
  5. Educating people about STIs
  6. STIs like syphilis aand gonorrhoea can be treated with antibiotics when recognised early.
  7. There are medications that can decrease the risk of HIV being passed on to others.
95
Q

Is there a cure for HIV/AIDS?

A

No.

IGCSE Biology (21 decks)

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