S7 - Reproduction and Inheritance

Question 1

asexual reproduction: + some advantages and disadvantages

Answer 1

-> involves only one parent, the offspring have identical genes to the parent
-more efficient in both time (faster) and energy (less energy required)
-since they’re identical, their is risk that they could all die if conditions become unfavorable
-mitosis: produce genetically identical cells

Question 2

sexual repoduction: + some advantages and disadvantages

Answer 2

-> involves the fusion of male and female gametes, because there are two parents, the offspirng contains a mixture of their parents’ genes
-produces variation of offspring
-requires time (longer) and energy (more energy is required)
-meiosis: produce genetically different cells

Question 3

what is fertilisation?

Answer 3

-> involves the fusion of a male and female gamete to produce a zygote that undergoes cell division and develops into an embryo

Question 4

sexual reproduction in plants:

Answer 4

structures of plants:
the stamen: (male part of the reproductive part in a plant)
-the anther -> contains pollen grain, these produce the male gametes (sperm)
-the filament -> is the stalk that supports the anther
the carpel: (female part of the reproductive part in a plant)
-the stigma -> the end bit that the pollen grains attach to
-the style -> the rod-like section that supports the stigma
-the ovary -> contains the female gametes (eggs) inside ovules

Question 5

insect pollinate: adaptations of features for pollination

Answer 5

petals: large and bright to attract insects
nectar: scanted with nectar to attract insects
pollen grains: sticky and in moderate amounts
anthers: inside flower, stiff and attached so that insects can brush apart
stigma: inside flower, sticky pollen grains stick to it when an insect brushes past

Question 6

wind pollinated: adaptations of features for pollination

Answer 6

petals: small and dull-usually green or brown
nectar: no scent or nectar
pollen grains: smooth and light so they can be easily carried in the wind and in large amounts to make sure some reach other flowers
anthers: outside flower, loose on long filaments so that pollen can be released easily
stigma: outside flower, forms network to catch pollen grains drifting in the wind
filament: long filaments that hang the anthers outside flower so that a lot of pollen gets blown away

Question 7

seed and fruit formation:

Answer 7

pollen grains land on stigma
pollen tube grows out of the pollen grain into the ovule
the ovary will become the fruit of the plant which will be the method of transport of the cell

Question 8

practical: understand the conditions needed for seed germination

Answer 8

germination is the process in which seeds begin to develop into a new young plant
-water: needed to activate enzymes to break down the starch food reserves in the seeds
-oxygen: needed for aerobic respiration to release energy for growth
-warmth: optimum temperature for enzymes will increase growth rate

Question 9

practical: understand the conditions needed for seed germination/ method

Answer 9

1) set up 4 boiling point with 10 cress seeds in each, sitting on a cotton wool
2) Tube A should have dry cotton wool and kept at 20ºC
3) Tube B should have moist cotton wool and kept at 20ºC
4) Tube C should have boiled water that has been cooled, covered with a layer of oil and kept at 20ºC
5) Tube D should have moist cotton wool but is kept at lower temperature (4ºC)
-the results will show that seeds germinate in test tube B only because it has the water, temperature and oxygen required for germination. Tube A does not have water, the oil in tube C does not allow for oxygen and tube D is not kept at optimum temperature

Question 10

germination:

Answer 10

-> process in which seeds begin to develop into a new young plant
conditions they need:
1) water -> to activate the enzymes that break down the food reserves in the seed
2) oxygen -> for respiration, which transfers the energy from food for growth
3) suitable temp. - for the enzymes inside the seed to work

Question 11

structures of seeds:

Answer 11

-embryo: young root and shoot become the adult plant
-food store: starch for the plant to use until it is able to carry out photosynthesis
-seed coat: a protective covering

Question 12

asexual reproduction: natural & artificial

Answer 12

1) Natural: runners
-eg: strawberry plants

2) Artificially (cloning): cuttings
-can be produced faster and cheaper
-the resulting plant will achieve maturity faster with a.r + diversity

Question 13

structure of the male reproductive system:

Answer 13

structure, description:
-sex gland: produces semen that contains sperm cells
-sperm duct: sperm passes through this
-testis: contains in scrotum (bag of skin) and produces sperm and testosterone
-penis: passes urine and semen out of the body
-urethra: tube inside the penis to carry urine or semen, a ring of muscle inside stops the two mixing

Question 14

structure of female reproductive system:

Answer 14

structure, description:
-ovary: contains ova (female gametes) which develop when FSH is released
-oviduct: connects ovary to the uterus and is lined with ciliated cells that push the ovum towards the uterus for fertilisation
-uterus: has a thick lining so that fertilised eggs can be implanted
-cervix: ring of muscle at lower end of uterus to ensure foetus remains in place during pregnancy
-vagina: muscular tube that leads to the inside of the body

Question 15

secondary sexual characteristics:

Answer 15

females: oestrogen
-breast development
-menstrual cycle begins
-growth of body hair
-widening of hips
-increased height
males: testosterone
-growth of penis and testes
-production of sperm
-growth of facial and body hair
-muscle development
-voice lowering and breaking

Question 16

the menstrual cycle:

Answer 16

the menstrual cycle last 28 days and the egg is usually released on day 14 (ovulation)
oestrogen:
-causes thickening of the uterus in preparation for implantation of an egg
-levels peak on day 10 and then begin to fall
progesterone:
-maintains the thick lining of the uterus
-inhibits the release of LH and FSH
-the egg matures on day 14 and progesterone starts increasing after this until it reaches its peak 3 days later
if the egg is not fertilised progesterone levels fall and the uterus lining breaks down in a period that lasts for around 5 days

Question 17

developing an embryo:

Answer 17

-the placenta allows diffusion of glucose, oxygen and amino acids from the mother’s blood to the developing foetus for growth, carbon dioxide and urea from the foetus are passed into the mother’s blood to be removes and it also takes over the production of progesterone
-amniotic fluid is a liquid contained in a bag (amnion) in the uterus that surrounds the foetus, it protects the foetus and cushions any rough movement, when labour begins the amnion breaks and the fluid come out-often known as a woman’s ‘water breaking’