Chapter 16 - Reproduction

Question 1

What is asexual reproduction?

Answer 1

Asexual reproduction is a process resulting in the production of genetically identical offspring from one parent.

Question 2

Can bacteria reproduce asexually?

Answer 2

Yes, bacteria produces exact genetic copies of themselves in a type of asexual reproduction called binary fission.

Question 3

Can plants reproduce asexually?

Answer 3

Yes, plants can reproduce asexually using bulbs and tubers; these are food storage organs from which budding can occur, producing new plants which are genetically identical to the parent plant. Some plants grow side shoots called runners that contain tiny plantlets on them. These are able to grow roots and develop into separate plants

Question 4

What are the advantages of asexual reproduction?

Answer 4

Population can be increased rapidly when conditions are right.
Can exploit suitable environments quickly.
More time and energy efficient.
Asexual reproduction is completed much faster than sexual reproduction.

Question 5

What are the disadvantages of asexual reproduction?

Answer 5

Limited genetic variation in populations. Offspring are genetically identical to their parents.
Population is vulnerable to changes in conditions and may only be suitable for one habitat.
Disease is likely to affect the whole population as there is no genetic variation.

Question 6

Why is asexual reproduction beneficial to crop plants?

Answer 6

Specifically in crop plants, asexual reproduction can be advantageous as it means that a plant that has good characteristics such as high yielding, disease resistant and hardy can reproduce asexually, and the offspring will show the same characteristics.

Question 7

What is sexual reproduction?

Answer 7

Sexual reproduction is a process involving the fusion of the nuclei of two gametes to form a zygote and the production of offspring that are genetically different from each other.

Question 8

What is fertilisation?

Answer 8

Fertilisation is the fusion of the nuclei of gametes.

Question 9

What is a gamete?

Answer 9

A gamete is a sex cell. They contain a haploid nucleus meaning they only have 23 chromosomes. E.g. an egg and sperm in humans and pollen grains and ovules in plants.

Question 10

What happens when two gametes fuse?

Answer 10

When 2 gametes fuse, they become a zygote which contains a diploid nucleus and has 46 chromosomes.

Question 11

What are the advantages of sexual reproduction?

Answer 11

Increases genetic variation.
The species can adapt to new environment due to variation, giving them a survival advantage.
Disease is less likely to affect population due to variation.

Question 12

What are the disadvantages of sexual reproduction?

Answer 12

Takes time and energy to find mates.
Difficult for isolated members of the species to reproduce.

Question 13

What is an advantage of crop plants reproducing sexually?

Answer 13

Most crop plants reproduce sexually which is an advantage because it means variation is increase and a genetic variant may be produced which is better able to cope with weather changes or produce a significantly higher yield.

Question 14

What is a disadvantage of crop plants reproducing sexually?

Answer 14

The disadvantage is that the variation may lead to offspring that are less successful than the parent plant at growing well or having a high yield.

Question 15

Diagram of a flower

Answer 15

Question 16

What is a sepal?

Answer 16

Protects unopened flower.

Question 17

What are petals?

Answer 17

Brightly coloured in insect pollinated flowers to attract insects.

Question 18

What is an anther?

Answer 18

Produces and released the male sex cell (pollen grain).

Question 19

What is a stigma?

Answer 19

Top of the female part of the flower which collects pollen grains.

Question 20

What is an ovary?

Answer 20

Protects the female sex cell (ovum).

Question 21

What is an ovule?

Answer 21

Contains the female sex cells (found inside the ovary).

Question 22

Diagram and characteristics of an insect pollinated flower

Answer 22

Question 23

Diagram and characteristics of a wind pollinated flower

Answer 23

Question 24

What type of pollen do insect pollinated flowers produce?

Answer 24

Insect pollinated flowers produce smaller amounts of larger, heavier pollen grains that often contain spikes or hooks on the outside so they can easier stick to insects.

Question 25

What type of pollen do wind pollinated flowers produce?

Answer 25

Wind pollinated flows produce large amounts of small, lightweight pollen grains that are usually smooth.

Question 26

What is pollination?

Answer 26

Pollination is the transfer of pollen grains from an anther to a stigma.

Question 27

What is self pollination?

Answer 27

Self-pollination is the transfer of pollen grains from the anther of flower to the stigma of the same flower or a different flower on the same plant. This reduces genetic variety of the offspring because all of the gametes come from the same parent and therefore are genetically identical. Due to the lack of variation, it means that they are less likely to have adaptations to respond to changes in the environment.

Question 28

What is cross pollination?

Answer 28

Cross-pollination is the transfer of pollen grains from the anther of a flower to the stigma of a flower of a different plant of the same species. This improves genetic variation as all of the gametes come from different parents. However, cross pollination relies on the presence of pollinators, and this can be a problem if there is a limited number of pollinators.

Question 29

What is fertilisation?

Answer 29

Fertilisation occurs when a pollen nucleus fuses with a nucleus in an ovule.

Question 30

What is germination?

Answer 30

Germination is the start of growth in a seed. Three factors are required for successful germination: Water, oxygen and warmth.

Question 31

Why is water needed for germination?

Answer 31

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

Question 32

Why is oxygen needed for germination?

Answer 32

Oxygen so that energy can be released for germination.

Question 33

Why is warmth needed for germination?

Answer 33

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

Question 34

Diagram of the male reproductive system

Answer 34

Question 35

What is the function of the prostate gland?

Answer 35

Produces fluid called semen that provides sperm cells with nutrients.

Question 36

What is the function of the sperm duct?

Answer 36

Sperm passes through the sperm duct to be mixed with fluids produced by the glands before being passed into the urethra for ejaculation.

Question 37

What is the function of the urethra?

Answer 37

Tube running down the centre of the penis that can carry out urine or semen, a ring of muscle in the urethra prevents the urine and semen from mixing.

Question 38

What is the function of the testis?

Answer 38

Contained in a bag of skin (scrotum) and produces sperm (male gamete) and testosterone (hormone).

Question 39

What is the function of the scrotum?

Answer 39

Sac supporting the testes outside the body to ensure the sperm are kept at a temperature slightly lower than body temperature.

Question 40

What is the function of the penis?

Answer 40

Passes urine out of the body from the bladder and allows semen to pass into the vagina of a women during sexual intercourse.

Question 41

Diagram of the female reproductive system

Answer 41

Question 42

What is the function of the oviduct?

Answer 42

Connects the ovary to the uterus and is lined with ciliated cells to push the released ovum down it. This is where fertilisation occurs.

Question 43

What is the function of the ovary?

Answer 43

Contains ova (female gametes) which will mature and develop when hormones are released. Oestrogen is produced here.

Question 44

What is the function of the uterus?

Answer 44

Muscular bag with a soft lining where the fertilised egg (zygote) will be implanted to develop into a foetus.

Question 45

What is the function of the cervix?

Answer 45

Ring of muscle at the lower end of the uterus to keep the developing foetus in place during pregnancy.

Question 46

What is the function of the vagina?

Answer 46

Muscular tube that leads to the inside of the women’s body where the male’s penis will enter during sexual intercourse and sperm are deposited.

Question 47

What is fertilisation?

Answer 47

Fertilisation is the fusion of the nuclei from a male gamete (sperm) and a female gamete (egg cell).

Question 48

Diagram of a sperm cell

Answer 48

Question 49

Why does a sperm have a flagellum (tail)?

Answer 49

Enables it to swim to the egg.

Question 50

Why does the sperm contain enzymes in the head region (acrosome)?

Answer 50

To digest through the jelly coat and cell membrane of an egg cell when it meets one.

Question 51

Why does the sperm contain many mitochondria?

Answer 51

Provide energy from respiration so the flagellum can move back and forth for locomotion.

Question 52

Diagram of an egg cell

Answer 52

Question 53

Why does an egg cell have cytoplasm containing a store of energy?

Answer 53

Provides energy for the dividing of the zygote after fertilisation.

Question 54

Why does an egg cell have a jelly like coating that changes after fertilisation?

Answer 54

Forms an impenetrable barrier after fertilisation to prevent other sperm nuclei from entering the egg cell.

Question 55

What are the differences between a sperm and an egg cell in terms of size, structure, mobility and numbers?

Answer 55

Question 56

What is an embryo?

Answer 56

After fertilisation in the oviduct, the zygote travels towards the uterus and divides several times to from an embryo which is a ball of cells that implants itself into the lining of the uterus to continue to grow and develop.

Question 57

Diagram of a foetus

Answer 57

Question 58

What is the function of the amniotic sac?

Answer 58

The amniotic sac surrounds the foetus and produces amniotic fluid.

Question 59

What is the function of amniotic fluid?

Answer 59

Amniotic fluid protects the foetus during development by cushioning it from bumps to the mother’s abdomen.

Question 60

What is the function of the umbilical cord?

Answer 60

The umbilical cord joins the foetus’s blood supply to the placenta for the exchange of nutrients (glucose and oxygen) and removal of waste products (carbon dioxide and urea).

Question 61

What is the function of the placenta?

Answer 61

The placenta is connected to the foetus through the umbilical cord and prevents the mothers and foetuses’ blood from mixing, exchanges dissolved nutrients such as glucose and oxygen and waste products such as carbon dioxide and urea and acts as a barrier to prevent toxins and pathogens getting into the foetus’s blood (although sometimes some pathogens such as rubella are passed through).

Question 62

What are the effects of oestrogen?

Answer 62

Effects of oestrogen in females include breasts developing, body hair growth, menstrual cycle begins, and hips get wider.

Question 63

What are the effects of testosterone?

Answer 63

Effects of testosterone in males include the growth of penis and testes, growth of facial and body hair, muscles develop, voice breaks, and testes start to produce sperm.

Question 64

How long is the average menstrual cycle?

Answer 64

The average menstrual cycle is 28 days long.

Question 65

What is ovulation?

Answer 65

Ovulation (the release of the egg) occurs about halfway through the cycle at day 14 and then the egg travels down the oviduct to the uterus.

Question 66

What is menstruation?

Answer 66

Failure to fertilise the egg causes menstruation which is the breakdown of the thickened lining of the uterus. Menstruation lasts about 5-7 days and signals the beginning the next cycle.

Question 67

What happens after menstruation?

Answer 67

After menstruation finished, the lining the uterus starts to thicken again in preparation for possible implantation in the next cycle.

Question 68

Diagram of the menstrual cycle

Answer 68

Question 69

What is the menstrual cycle controlled by?

Answer 69

The menstrual cycle is controlled by hormones released from the ovary and the pituitary gland in the brain

Question 70

What is FSH (follicle stimulating hormone)?

Answer 70

FSH (follicle stimulating hormone) is released by the pituitary glands and stimulates egg maturation in the follicles of the ovary. It also stimulates the follicles in the ovary to start releasing oestrogen.

Question 71

What is LH (luteinising hormone)?

Answer 71

LH (luteinising hormone) causes ovulation to occur when LH is at its peak, this results in the formation of a corpus luteum which stimulates the production of progesterone. The pituitary gland is stimulated to released luteinising hormone when oestrogen levels have reached their peak.

Question 72

What is oestrogen?

Answer 72

Oestrogen stimulates the uterus to develop a lining (to replace the lining lost during menstruation) and post ovulation inhibits (stops) FSH and LH production in the pituitary gland.

Question 73

What is progesterone?

Answer 73

Progesterone maintains the thickens the lining of the uterus, inhibits (stops) FSH and LH products and if fertilisation doesn’t occur, levels drop, and menstruation occurs.

Question 74

What are all the hormones involved in the menstrual cycle and what do they do?

Answer 74

The pituitary gland produces FSH which stimulates the development of a follicle in the ovary. An egg develops inside the follicle and the follicle produces oestrogen. Oestrogen causes the growth and repair of the lining of the uterus wall and inhibits (stops) the production of FSH. When oestrogen rises to a high enough level, it stimulates the released of LH from the pituitary gland which causes ovulation (usually around day 14 of the cycle). The follicle becomes the corpus luteoma and starts producing progesterone which maintains the uterus lining. If the egg is not fertilised, the corpus luteum breaks down and progesterone levels drop. This causes menstruation. However, if fertilization does occur, the corpus luteum continues to produce progesterone preventing the uterus lining from breaking down. This happens until the placenta has developed at which it starts secreting progesterone and continues to do so throughout the pregnancy.

Question 75

Diagram of the hormones involved in the menstrual cycle

Answer 75

Question 76

Diagram of where hormones for the menstrual cycle are produced and where they act

Answer 76

Question 77

What is an STI (sextually transmitted infection)?

Answer 77

A sexually transmitted infection (STI) is an infection that is transmitted through sexual contact.

Question 78

What is HIV (human immunodeficiency virus)?

Answer 78

Human immunodeficiency virus (HIV) is a pathogen that causes an STI. A HIV infection may lead to aids.

Question 79

How can HIV be transmitted?

Answer 79

HIV can be transmitted by the spread of body fluids including blood, semen, vaginal secretions, anal fluids and breast milk. This is often done by anal or vaginal intercourse with a person who has HIV while not using a condom or sharing equipment for injectable drugs, hormones and steroids with a person who has HIV.

Question 80

How can you control the spread of STIs?

Answer 80

You can control the spread of STIs by limiting the number of sexual partners you have, not having unprotected sex, getting tested, raising awareness by education programmes and not sharing needles.