D3.1 continuity and change organisms reproduction

Question 1

Comparing asexual and sexual reproduction

Answer 1

asexual (one parent, mitosis, genetically identical offsprings, no genetic variation, fast, cheap) sexual (two parents, meiosis, genetically different offsprings, genetic variation, possibility of evolving)

Question 2

Differences in male and female gametes

Answer 2

Male (traveling, smaller, small food reserves, large amounts) Female (sessile, larger, more food for possible embryo, few or one)

Question 3

Meiosis in sexual reproduction

Answer 3

Male and female gametes fuse together, gametes are haploid cells, breaks up parental combinations of cells. Diploid cells -> meiosis -> haploid cells -> fertilisation cycle

Question 4

Ovarian cycle

Answer 4

Follicles develop in the ovary (only one finishes) and releases an egg (ovulation), wall of follicle becomes corpus luteum (luteal phase) which breaks down if no embryo is present and ovary returns to follicular phase

Question 5

Uterine cycle

Answer 5

Endometrium (inner layer of uterus) thickens in preparation for an embryo, thickening breaks down and passes out as menstrual bleeding if no embryo is present

Question 6

In menstrual cycle, hormones produced by the pituitary gland

Answer 6

FSH (high during first 10 days, stimulates development of follicles), LH (sudden sharp peak on day 14, stimulates maturation of the oocyte by bursting of the follicle wall, then stimulates corpus luteum)

Question 7

In menstrual cycle, hormones produced by the wall of the follicle and corpus luteum

Answer 7

Oestradiol (second week, stimulates repairing of the endometrium), Progesterone (rise following ovulation, promotes thickening and maintenance of the endometrium)

Question 8

Fertilisation in humans

Answer 8

Fusion of sperm and egg to form a zygote. Sperms have receptors that detect chemicals released by egg to know where to swim, then push in between cells to reach egg and bind to it

Question 9

Hormones in IVF (in vitro fertilisation) treatment

Answer 9

1. down regulation (2 weeks) to stop FSH and LH to control egg production, 2. FSH injections (7-12 days) to stimulate follicles, 3. hCG injection to tell the body that an embryo is present, 4. egg collection, 5. fertilisation by mixing with 50,000 to 100,000 sperm cells, 6. embryo transfer to uterus

Question 10

Sexual reproduction in flowering plants

Answer 10

meiosis, gamete production and fertilisation happen inside flowers, embryo develops inside a seed in female plant. If both male and female parts are in the same plant – hermaphrodite, self-pollination and fertilisation

Question 11

Cross-pollination

Answer 11

Transferring pollen from the anther of a flower to the stigma of a flower of another plant, by an outside agent like wind or an animal. Promotes genetic variation and evolution

Question 12

Features of an insect-pollinated flower

Answer 12

Brightly coloured petals, spiky pollen grains, anther positioned to deposit pollen on insect, sticky stigma where visiting insect will drop some pollen, nectaries so deep you can’t avoid the other parts

Question 13

Self-incompability mechanisms in hermaphrodite plants

Answer 13

Genotypes have to be compatible – S1 and S2 of the plant are not compatible with the same S1 and S2 of its own, instead they need S3 and S4 to reproduce. E.g. Apple trees – two types are needed in an orchard

Question 14

Seed dispersal

Answer 14

Reduces competition, many strategies; attractive seeds for eating, feathery to catch wind, with hooks to attach to animals, explosive.