Animal and Plant Hormones- biology paper 2 Flashcards
What happens at puberty?
The body starts releasing sex hormones that trigger off secondary sexual characteristics and cause eggs to mature in women
What’s the reproductive hormone in men?
Testosterone
What’s the reproductive hormone in women?
Oestrogen
What’s the menstrual cyclce?
The monthly sequence of events in which the female body releases an egg and prepares the uterus(womb) in case it releases a fertilised egg
How many stages does the menstrual cycle have?
4
What happens during stage 1 of the menstrual cycle?
Menstruation (bleeding) starts and the uterus lining breaks down for about 4 days
What happens during stage 2 of the menstrual cycle?
The lining of the uterus builds up again, from day 4 to day 14, into a thick spongy layer full of blood vessels, ready to receive a fertilised egg.
What happens during stage 3 of the menstrual cycle?
An egg is released from the ovary at day 14. This is called ovulation
What happens during day 4 of the menstrual cycle?
The uterus is maintained for about 14 days, until day 28 If no fertilised egg has landed on the uterus wall by day 28, the spongy lining starts to break down again and the whole cycle starts again.
What does FSH do?
causes an egg to mature in one of the ovaries in a structure called a follicle. It also stimulates the production of oestrogen
What does LH do?
stimulates the release of an egg at dy 14.
What does oestrogen do?
stops FSH being produced, repairs thickens and maintains the uterus lining, stimulates the release of LH
What does progesterone do?
Maintains the lining of the uterus during the middle part of the menstrual cycle and during pregnancy.Also stops the release of LH and FSH
What produces FSH?
The pituitary gland
What produces oestrogen?
The ovaries
What produces LH?
The pituitary gland
What produces progesterone?
The ovaries
What are contraceptives?
Things that are used to prevent pregnancy
What hormones are usually used in contraceptives?
Oestrogen and Progesterone
How does oestrogen reduce fertility?
Although oestrogen stimulates the release of an egg, if taken every day to keep the level permanently high, it stops the production of FSH. So, after a while, egg maturation is stopped and therefore egg release stops.
How does progesterone reduce fertility?
It stimulates the production of thick cervical mucus which prevents any sperm getting through and reaching an egg. It can also stop egg maturation and the release of an egg.
Why does the pill now contain lower levels of oestrogen?
So that there’s fewer side effects, like blood clots
Why is there now a progesterone-only pill?
So that there’s fewer side effects than the combined pill.
What are the benefits of taking the oral contraceptive pill?
- Over 99% effective at preventing pregnancy
- Reduces risk of getting certain cancers
What are the problems with taking the oral contraceptive pill?
- Not 100% effective, so still a slight chance of getting pregnant
- Can cause side effects like headaches, nausea, irregular menstrual bleeding, and fluid retention
- Doesn’t protect against STD’s
Describe the contraception patch
It’s a small patch containing oestrogen and progesterone that is stuck to the skin and lasts about a week
Describe the contraceptive implant (arm)
The implant is inserted under the skin of the arm and continuously produces progesterone. This progesterone stops the ovaries from releasing eggs, makes it hard for the sperm to swim to the eggs and stops any fertilised eggs implanting in the uterus. An implant can last for three years.
Describe the contraceptive injection
This injection contains progesterone and each dose lasts 2 to 3 months
What are barrier methods of contraception?
Non-hormonal barrier forms of contraception that are designed to stop the sperm from getting to the egg.
Describe condoms
Condoms are worn over the penis during intercourse to prevent the sperm from entering the vagina. Condoms are the only form of contraception that protect against STD’s
Describe a diaphragm
A shallow plastic cup that fits over the cervix (the entrance to the uterus) to form a barrier. It has to be used with spermicide.
Why isn’t spermicide usually used alone as a contraceptive?
Because it’s not as effective as when used with a diaphragm
How effective are condoms?
98%
How effective is a diaphragm with spermicide?
92-96%
How effective is spermicide by itself?
70-80%
What is an IUD?
a T-shaped device that is inserted into the uterus to kill sperm and to prevent implantation of a fertilised egg.
What are the 2 types of IUD’s?
plastic IUD’s that release progesterone and copper IUD’s that prevent the sperm from surviving in the uterus
What is the surgical method of contraception?
Sterilisation
What does sterilisation involve?
Cutting or tying the fallopian tubes , or cutting or tying the sperm duct
Is sterilisation a permanent procedure?
Yes
What are natural methods of contraception?
Avoiding sexual intercourse during menstruation, not having sex
What hormones can be injected into women to increase fertility?
LH and FSH
What are the problems with using fertility drugs like FSH and LH?
- They don’t always work- some women may have to use the treatment many rimes, which can be expensive
- Too many eggs could be stimulated , resulting in unexpected multiple pregnancies
What is IVF?
A process that can be used to help couples who are having difficulty having children
Describe the steps of IVF
1) FSH and LH are given to the woman to stimulate the maturation of multiple eggs
2) Eggs are then collected from the woman’s ovaries
3) The eggs are then fertilised in a lab using the man’s sperm
4) The fertilised eggs then grow into embryos in a lab incubator
5) Once the embryos have formed, one or two of them are transferred to the woman’s uterus. Transferring more than one improves the chance of pregnancy
What is a pro of IVF?
It helps to give an infertile couple a child
What are the cons of IVF?
- Multiple births can occur, which can become risky for the mother and babies
- The sucess rate is low, which can make the process incredibly stressful and upsetting if there’s multiple failures
- As well as being emotionally stressful, the process is also physically stressful for the woman. This is because some women may have a strong reaction to the hormones
What can be the side effects of IVF?
abdominal pain, vomiting, dehydration
What advances in technology have helped to improve the success and technique of IVF?
the development of specialised micro tools and the development of time lapse imaging
Why do some people think IVF is wrong?
Because unused embryos end up destroyed, also the genetic testing of embryos before implantation can lead to people selecting embryos based on preferred characteristics
What gland releases thyroxine?
The thyroid gland
What’s the difference between IUI and IVF?
During IUI, the sperm is put in the uterus
What triggers thyroxine to be released?
TSH, which is released from the pituitary gland
What does TSH stand for?
thyroid stimulating hormone
What keeps the amount of thyroxine in our blood at the right level?
Negative feedback
What happen when the thyroxine level in our blood is too high?
the secretion of TSH is stopped, which reduces the amount of thyroxine released by the thyroid gland
What happens when the thyroxine level in our blood is too low?
the secretion of TSH from the pituitary gland is stimulated again, which increases the amount of thyroxine released by the thyroid gland
What does thyroxine do?
It controls the metabolic rate
What gland releases adrenaline?
The adrenal glands
Do plants need to be able to respond to changes in the environment in order to survive?
Yes
What is auxin?
A plant hormone that controls growth near the tips of shoots and roots. It controls the growth of a plant in response to different stimuli.
What does auxin control?
Phototropism and gravitropism
What is phototropism?
how a plant grows in response to light
What is gravitropism/geotropism?
how a plant grows in response to gravity
Where is auxin produced?
in the tips of roots and shoots
How does auxin cause shoots to grow towards light?
- Light causes auxin to concentrate on the darker side of the shoot tip
- Auxin then spreads down the shoot
- This results in cells on the darker side of the shoot growing faster than cells on the lighter side of the shoot
- This causes the shoot to grow towards the light
How does auxin cause roots to grow towards gravity?
- Gravity causes auxin to concentrate on the lower side of the root
- In roots, auxin stops cell growth
- So, the lower side of the root will grow slower than the upper side of the root
- This causes the root to grow towards the force of gravity and bend downwards
How does auxin cause shoots to grow away from gravity?
- Gravity causes auxin to accumulate on the lower side of the shoot
- This causes the lower side of the shoot to grow faster , bending the shoot upwards and away from gravity
What is auxin used for?
- Killing weeds
- Growing from cuttings with rooting powder
- Growing cells in tissue culture
What are gibberellins used for?
controlling dormancy, inducing flowering, growing larger fruit
What are gibberellins?
A plant growth hormone that stimulates seed germination, stem growth and flowering
What does ethene do?
controls cell division and stimulates enzymes that cause fruit to ripen.
What experiment can be used to investigate the effect of light on plants?
1) Put 10 cress seeds in 3 different petri dishes, each lined with moist filter paper.
2) Shine a light onto one of the dishes from above and 2 of the dishes from different directions.
3) Leave the cress seeds alone for one week until you can observe their responses- you’ll find that the seedlings grow towards the light
4) You’ll know that the growth response of the cress seedlings is due to light, only if you control all the other variables
What variables need to be controlled when seeing the effect of light on plants?
- The number of seeds used
- The type of seed used
- The temperature
- The amount of water each petri dish gets
- The light intensity
What experiment can be used to investigate the effect of gravity on plants?
1) Put 4 cress seedlings into a petri dish that’s lined with damp cotton wool. The roots of the cress seedlings should all be pointing in different directions
2) Store the petri dish vertically for a few days in the dark
3) You should find that the roots of each seedling grow downwards towards gravity and the shoots grow upwards away from gravity
