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Biology IGCSE > Chapter 16 > Flashcards

Chapter 16 Flashcards

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1
Q

asexual reproduction

A

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

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2
Q

Discuss the advantages and disadvantages of asexual reproduction to a population of a species in the wild and crop population

A

Advantages:

  • it is fast
  • It takes less energy to find a mate

Disadvantages:

  • compete with parents for resources
  • for crops, since there is little to no variation, if one is affected by a certain disease they all will as they all have no resistance.
  • for wild plants, if the environments change, it is unlikely a new species could adapt to the environment
  • in the wild, if there is more variation there is more chance for a species to adapt and evolve.
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3
Q

sexual reproduction

A

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

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4
Q

the nuclei of gametes are….

A

…haploid

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5
Q

the nucleus of a zygote is….

A

….diploid

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6
Q

Discuss the advantages and disadvantages of sexual reproduction to a population of a species in the wild and crop population

A

Advantages:

  • each offspring is genetically unique, so there is wild diversity
  • each organism is unique so disease cannot spread as easily.
  • organisms can adapt

Disadvantages:
- it may be difficult for some species to find mates,
especially when there is an imbalance of males and females in an area or if the species
is endangered.
- it takes longer and requires more energy to produce
offspring, therefore it is less efficient than asexual reproduction.

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7
Q

Identify and draw, using a hand lens if necessary, the sepals, petals, stamens, filaments and anthers, carpels, style, stigma, ovary and ovules, of an insect-pollinated flower

A

ok

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8
Q

State the functions of the sepals

A

They protect the flower when it is a bud

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9
Q

State the functions of the petals

A

attracts insects to carry their pollen

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10
Q

State the functions of the anthers

A

where the pollen is made

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11
Q

State the functions of the stigma

A

A stalk which helps hold the anther

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12
Q

State the functions of the ovaries

A

They carry the ovules, which contain the egg cell

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13
Q

Distinguish between the pollen grains of insect-pollinated and wind-pollinated flowers

A

The pollen grains of insect pollinated flowers are often spiky and sticky. This helps to attach to the hairs on the insects body.
The pollen grains of wind pollinated flowers are small, smooth and light so they can be easily carried by the wind. There is a lot of pollen produced in wind pollination as it is not entirely likely it will attach to the stigma of another plant.

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14
Q

self-pollination

A

the transfer of pollen grains from the anther of a flower to the stigma of the same flower or different flower on the same plant

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15
Q

cross-pollination

A

transfer of pollen grains from the anther of a flower to the stigma of a flower on a different plant of the same species

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16
Q

Discuss the implications to a species of self-pollination and cross-pollination in terms of variation, capacity to respond to changes in the environment and reliance on pollinators

A

Cross-pollination leads to more variation in plants than self-pollination. With more variation, organisms are more likely to adapt to their environment if it changes. Although, self-pollination does not have to rely on pollinators as they are so close by.

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17
Q

Describe the growth of the pollen tube and its entry into the ovule followed by fertilisation

A

pollen grows a pollen tube to take the male nucleus to the egg. As the pollen tube grows downwards, it gains nutrients from the tissues of the style and carries the male gamete nucleus with it. The first pollen tube reaches the ovary, then enters the ovule through a small hole (the micropyle). The male gamete nucleus then fuses with the egg cell nucleus; leading to fertilisation.

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18
Q

When does fertilisation occur in plants?

A

when a pollen nucleus fuses with a nucleus in an ovule

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19
Q

Describe the structural adaptations of insect-pollinated and wind-pollinated flowers

A

Insect pollinated flowers are bright, colourful, smell nice and produce nectaries to attract insects. Wind-pollinated flowers have their feathery stigmas outside the flower to increase the surface area to catch the pollen.**

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20
Q

Investigate and state the environmental conditions that affect germination of seeds, limited to the requirement for water, oxygen and a suitable temperature

A
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21
Q

Identify and name on diagrams of the male reproductive system: the testes, scrotum, sperm ducts, prostate gland, urethra and penis, and state the functions of these parts

A

rather not ngl

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22
Q

Identify and name on diagrams of the female reproductive system: the ovaries, oviducts, uterus, cervix and vagina, and state the functions of these parts

A

rather not ngl

23
Q

Describe fertilisation in humans

A

the fusion of the nuclei from a male gamete (sperm) and a female gamete (egg cell/ovum)

24
Q

State the adaptive features of sperm

A

Sperm have a flagellum to move, they also contain many mitochondria​ to produce energy for this movement. When the sperm cell reaches the egg cell, it must ​digest the wall of the cell​ so that it can fuse their nuclei.​ This is done using ​enzymes​ located in the ​acrosome.

25
Q

State the adaptive features of egg cells

A

Once fertilisation has occurred, the ​zygote​ undergoes mitosis to produce many cells which make up an ​embryo​. The egg cell contains ​energy stores​ to allow this to happen​. It also contains a ​jelly coat​ which changes after fertilisation ​and ensures that only one sperm cell can enter.

26
Q

What does the zygote form in early development?

A

the zygote forms an embryo which is a ball of cells that implants into the wall of the uterus

27
Q

State the functions of the umbilical cord

A

Connects the fetus to the placenta and contains blood vessels to transport blood to and from the placenta.

28
Q

State the functions of the placenta

A

Connects to the fetus end of the umbilical cord and allows exchange of substances like oxygen and waste. It also produces hormones such as oestrogen and progesterone.

29
Q

State the functions of the amniotic sac

A

Surrounds the fetus and produces amniotic fluid.

30
Q

State the functions of the amniotic fluid

A

protects the foetus from external force

31
Q

Outline the growth and development of the fetus in terms of increasing complexity in the early stages and increasing size towards the end of pregnancy

A

1 month: the human embryo looks like a tadpole. The embryo does not have arms or legs. the heart has started to beat
2 months: the embryo has a face, limbs, fingers and toes and looks more human. Most of the organs have formed. It is now a foetus.
3 months: the nerves and muscles of the fetus develop rapidly
5 months: has eyebrows, fingernails, fingerprints and body hair. 18cm in length
7 months: development is almost complete.

32
Q

Describe the antenatal care of pregnant women

A

The mother needs to have adequate amounts of calcium for the bones, iron to make extra blood cells, carbohydrates to supply the mother with enough energy to move her heavy body and proteins to ensure the child’s growth. The mother should not smoke as it can cause a premature or underweight baby and not drink alcohol to prevent brith defects and mental retardation.

33
Q

Outline the processes involved in labour and birth

A

The baby turns around so its head is facing downwards.

  1. Due to contractions, there is the breaking of the amniotic sac, releasing amniotic fluid
  2. There is contraction of the muscles in the uterus wall to push the baby out while the cervix dilates.
  3. The baby then exits the mother via passage through the vagina
  4. the umbilical chord is then tied and cut.
  5. The placenta then detaches and leaves the mother through the vagina
34
Q

Compare male and female gametes in terms of size, structure, motility and numbers

A

The egg is much larger than the sperm cell. The egg has a nucleus, membrane, cytoplasm and a jelly coat while the sperm has a head, nucleus, middle piece and flagellum. There are more sperm than eggs produced and sperm are more mobile as they have a flagella and eggs need to move via cilia in the uterus.

35
Q

Describe the function of the placenta and umbilical cord in relation to exchange of dissolved nutrients, gases and excretory products and providing a barrier to toxins and pathogens

A

The mother passes​ essential nutrients​ to the foetus through the​ umbilical cord​, such as amino acids, oxygen and glucose. These help​ build cells,​ and hence structures, in the foetus. In addition,​ waste products​ diffuse out of the foetus to be excreted from the mother’s body. This prevents a build-up of​ toxins​ which could harm the foetus. In addition, ​antibodies ​are passed to the foetus, allowing it to develop a​ resistance to pathogens​.The umbilical chord and placenta act like a barrier between the baby and toxins and pathogens.

36
Q

What can pass through the placenta to the fetus?

A

some toxins, e.g. nicotine, and pathogens, e.g. rubella virus, can pass across the placenta and affect the fetus

37
Q

Discuss the advantages and disadvantages of breast-feeding compared with bottle-feeding using formula milk

A

advantages:
- breast milk contains antibodies that give passive immunity to the child.
- helps to form a close bond between the mother and baby
- allows the child and mother to be more safe in terms of cancer threat and diseases.
- some women can not make bottled milk in sterile environments. For them, breast-feeding is better.
- formula milk costs money, breast-feeding doesn’t

disadvantages:

  • some mothers are not able to breast-feed their child
  • some mothers find it embarrassing or difficult
  • bottled milk is more convenient
  • It does not work for single fathers.
38
Q

Describe the roles of testosterone and oestrogen in the development and regulation of secondary sexual characteristics during puberty

A

Testosterone stimulates:

  • the growth of male sex organs
  • the testes to make sperm cells
  • growth of hair on the face
  • deepening of the voice
  • development of muscles in the body

oestrogen stimulates:

  • the growth of female sex organs
  • the start of the first menstrual cycle and first period
  • growth of hair on some parts of the body
  • growth and development of breasts
  • widening of the hips
39
Q

Describe the menstrual cycle in terms of changes in the ovaries and in the lining of the uterus

A

The menstrual cycle happens approximately every ​28 days​. During each cycle, an ​egg cell is released​ from the ovaries. The ​uterus wall thickens​ with blood vessels and glands in preparation for a pregnancy, which would occur if the egg is fertilised. If this egg is not fertilised, the egg dies and ​menstruation​ occurs, where the dead egg cell and old uterus lining is expelled from the body in a ​period​

40
Q

Describe the sites of production of oestrogen and progesterone in the menstrual cycle and in pregnancy

A

The ovaries and produce oestrogen and progesterone in the menstrual cycle and the placenta produces them in pregnancy.

41
Q

Explain the role of hormones in controlling the menstrual cycle and pregnancy

A

FSH​ - Follicle stimulating hormone triggers the development of an egg cell in the ovary, and also stimulates oestrogen production in the ovaries. This is produced in the pituitary gland.
LH​ - Luteinising hormone triggers an egg to be released, as well as stimulating progesterone production in the ovaries.
Progesterone​ - Progesterone is responsible for maintaining the thick uterus lining in the cycle and during pregnancy. It also decreases FSH production.
Oestrogen​ - Stimulates the repair and thickening of the lining of the uterus and LH production, whilst decreasing FSH production.
At the beginning of the cycle, levels of ​FSH and LH are high​ to stimulate egg production and cause the production of oestrogen which thickens the uterus lining. When the egg is released, the levels of ​LH, FSH and oestrogen decrease​, whilst ​progesterone is released​ to maintain the uterus lining. If the egg is​ not fertilised​, ​progesterone levels decrease ​and the uterus lining breaks down, causing menstruation.

42
Q

Outline the methods of birth control

A

– abstinence (not fricking)
– monitoring body temperature and cervical mucus (to determine when to have fricking and when to not during cycle)
– IUD (prevents sperm from entering and preventing the embryo from implanting)
– IUS ( contains progesterone to make the cervix to become thick and sticky so sperm can’t swim through)
– contraceptive pill (contain progesterone and sometimes oestrogen prevent the ovary from releasing eggs)
– implant (release progesterone and prevents the egg from releasing)
– injection (release progesterone and prevents the egg from releasing)
– condom (prevents the sperm from entering the uterus)
– femidom (female condom)
– diaphragm (prevents man’s sperm from entering the uterus, it is paired with sperm-killing cream)
– vasectomy (sperm tubes are cut and tied)
– female sterilisation (oviducts cut and blocked)

43
Q

Outline the use of hormones in contraception and fertility treatments

A

Women may be infertile if they do not produce eggs due to lack of FSH. Therefore, they can be given a fertility drug containing FSH. There are also drugs which make the pituitary insensitive to oestrogen.
In contraception, progesterone can be taken to prevent the release of an egg.

44
Q

Outline artificial insemination (AI)

A

sperm is directly inserted into the uterus. This sperm can be from the partner, or from a sperm bank if their sperm is not of a high enough quality.

45
Q

Outline in vitro fertilisation (IVF)

A

If fertilisation cannot occur due to the sperm count or quality being too low, the egg cell can be fertilised outside of the body and then be implanted back into the uterus.

46
Q

Discuss the social implications of contraception and fertility treatments

A

Some people believe that fertility treatments, such as IVF, and genetic screening of embryos may lead to ‘​designer babies​’, where parents will discard eggs which do not have​ desired characteristics​, for example a certain hair colour or gender. In addition, they may avoid having a child with an inherited disease.
Contraception led to families being able to plan for their future, increase in promiscuity and STIs and women to have more control over their fertility.

47
Q

sexually transmitted infection

A

an infection that is transmitted via body fluids through sexual contact

48
Q

What is an example of an STI?

A

human immunodeficiency virus (HIV)

49
Q

Explain how the spread of STIs is controlled

A
  • Antibiotics
  • Contact tracing (where a person who has gotten HIV identifies who they could have spread it too)
  • use of condoms
  • free needle exchange schemes
  • screening donated blood for HIV antibodies
  • education programmes to make people more aware of the issue
50
Q

Describe the methods of transmission of HIV

A

It can be transmitted through the blood and semen. It can therefore be given to another person, either via unprotected fricking or hypodermic needles. It can also be passed down from the mother to the child.

51
Q

HIV infection may lead to…..

A

AIDS

52
Q

Outline how HIV affects the immune system, decreased

A

In the blood, HIV attaches to ​lymphocytes​ (white blood cells) and enters the cell. Here, it uses the cell to replicate itself and thus the cell cannot carry out its normal functions. Consequently, HIV ​reduces the number of functioning lymphocytes​, as well as ​reducing the body’s ability to produce antibodies​ to fight off infection.

53
Q

Conditions for germination in plants

A

Water​ ​- water moves into the seed, causing it to swell. This allows the embryo to begin growing.
Oxygen​ ​- used in respiration to produce energy for growth.
Temperature​ ​- the seed contains enzymes, e.g. for respiration, which will work faster at
the plant’s optimum temperature. This is why seeds are dormant in the winter and grow again in the spring.

Biology IGCSE (21 decks)

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