Reproduction in Humans Flashcards
What are the differences between sexual and asexual reproduction?
Sexual : two types of gametes produced, produce variation in offspring
Asexual: no gametes or fertilisation, produce genetically identical offspring
What is fertilisation?
The fusion of a male and female gamete to produce a zygote that undergoes cell division and develops into an embryo
Describe the structures of an insect-pollinated and a wind-pollinated flower and explain how each is adapted for pollination
Insect: stamen and stigma enclosed within flower so insect must make contact. Stigma is sticky so pollen grains attach. Petals large and colourful to attract insects. Nectaries present to produce nectar as a reward. Pollen grains are large and sticky to stick to insects bodies.
Wind: stamen is exposed so wind can easily blow pollen away, stigma exposed and feathery to catch pollen blowing in wind. Petals are small and green, nectaries absent and pollen grains are smaller and smooth.
Describe seed and fruit formation
Once fertilisation has occurred, the zygote develops into an embryonic plant with small radicle and plumule. The other contents of the ovule develop into cotyledons which will be a food store for the young plant when the seed germinates. The ovule wall becomes the seed coat or testa and the ovary wall becomes the fruit coat.
What conditions are needed for seed germination? (paper 2)
Warm temperatures - so that enzymes can act efficiently
Water - for chemical reactions to take place in solution
Oxygen - for respiration
How do germinating seeds utilise food reserves? (Paper 2)
During germination, the food store provides nutrients to allow the radicle and plumule to grow. The radicle grows down into the soil, where it will absorb water and mineral ions. The plumule grows upwards towards the light, where it can start photosynthesis.
How do plants reproduce asexually?
Artificial: a piece of a plants stem, with a few leaves attached is cut from a healthy plant. This is planted in damp compost, where it will grow roots and develop into a new plant.
Natural: Runners
describe the structure and explain the function of the male reproductive system
Urethra: tube which carries sperm through the penis during ejaculation. Urine passes through this.
Glands: produce the liquid thats added to sperm to make semen
Erectile tissue: swells when filled with blood to make the penis erect
Vas defernes: muscular tube that carries sperm from testis towards the urethra
Testis: sperm made
Scrotal sac: contains testes, hangs behind penis
describe the structure and explain the function of the female reproductive system
Fallopian tube: muscular tube that carries ovum from ovary to uterus
Ovary: organ that produces ova and sex hormones
Uterus: organ where an embryo grows
Endometrium: good blood supply for implantation of an embryo
Cervix: neck of uterus
Vagina: sperm deposited
What are the roles of oestrogen and progesterone?
Oestrogen: repairs and thickens the lining of the uterus after menstruation. Slows down production of LSH and stimulates the secretion of LH
Progesterone: completes the development of the uterus lining which thickens ready for the fertilised egg to sink into it and develop into an embryo. Inhibits the released of FSH and LH, stopping ovulation.
Describe the role of the placenta (Paper 2)
Allows the embryo to obtain materials such as oxygen and nutrients from the mothers blood. Allows the embryo to get rid of waste products such as urea and carbon dioxide
Describe the role of amniotic fluid (Paper 2)
Protects the developing embryo against jolts and bumps.
What are the roles of oestrogen and testosterone?
Oestrogen: produces the female secondary sex characterises
Testosterone: controls the development of the male secondary sexual characterisitcs
