Biology - 11 Hormonal Coordination - 11.7 The Artificial Control of Fertility & 11.8 Infertility Treatment & 11.9 Plant Hormones and responses & 11.10 Using Plant Hormones

Types of hormone-based contraception [3]:

- contraceptive pill
- contraceptive implant
- contraceptive patch

Mixed pill [3]

- contraceptive pill containing oestrogen and progesterone
- inhibit release of FSH and LH to stop eggs maturing
- makes cervical mucus thick

Progesterone-only pill [4]

- contraceptive pill containing only progesterone
- fewer side effects
- must be taken regularly
- inhibits FSH and LH

Contraceptive implant [3]

- inserted under the skin
- slowly releases progesterone
- inhibits FSH and LH

Contraceptive patch [3]

- patch containing oestrogen and progesterone
- replaced once a week
- inhibits FSH and LH

Spermicide [2]

- kills or disables sperm
- not very effective

Barrier methods [2]:

- condom
- diaphragm

Intrauterine device (IUD) [3]

- inserted into the uterus
- last 3-5 years
- can be copper or contain progesterone

Abstinence

not having sex

Surgical methods [2]

- vasectomy (male sterilisation)
- female sterilisation

Vasectomy

sperm ducts are cut and tied

Female sterilisation

oviducts are cut and tied

Treatment for lack of ovulation [2]

- artificial FSH is given to stimulate maturation of an egg
- artificial LH is given to cause ovulation

Why would IVF be used? [3]

- damage to oviducts
- use of donor egg
- no obvious cause for infertility

IVF process [4]:

- artificial FSH and then LH given to cause eggs to mature and come to point of ovulation
- eggs are collected and fertilised with sperm
- fertilised eggs are kept in warm solution to form embryos
- one or two embryos are inserted into the womb

Disadvantages of IVF [6]:

- expensive for society and individuals
- not always successful
- fertility drugs have health risks
- process is stressful for mother
- increases chance of multiple pregnancy
- ethical problems with excess embryos

Tropism

growth response of a plant toward or away from a stimulus

Phototropism

growth response to light

Gravitropism/geotropism

growth response to gravity

Auxin

a plant hormone that promotes root formation and bud growth

How does auxin distribution cause phototropism? [2]

- auxin moves to the shadowed side
- the shadowed side grows causing the plant to bend

How do shoots react to auxin?

shoots grow more with more auxin

How do roots react to auxin?

roots grow less with more auxin

How does auxin distribution cause gravitropism? [3]

- auxin moves downward due to gravity
- roots are inhibited, so they bend downwards
- shoots grow more, so they bend upwards

Rooting powder [3]

- also called IAA
- powder containing auxin
- cuttings are dipped to promote root growth

Auxin weed killer [3]

- auxin causes plants to grow uncontrollably, killing them
- most weeds are broad-leaved, while crops are narrow-leaved
- weeds are killed while crops are spared

Uses of auxins [3]

- promote root growth in cuttings
- weed killer
- cloning plant tissue cultures

Gibberellins [3]

- promote flowering
- promote germination/end seed dormancy
- increase size of fruit

Uses of gibberellins [3]

- in brewing industry to speed up germination for growth of barley for malt
- to promote flowering throughout the year
- to increase the size of fruit (especially seedless)

Ethene

promotes fruit ripening so fruits can be safely transported