Describe the two different methods used by the bod
1. Two methods - nervous system and hormones
2. Both send messages to cause the body to respond to change
3. HOW are the messages sent?
In the nervous system, the messages are sent as nervous impulses along neurones
The messages are hormones which travel in the blood
4. SPEED of reaction?
The nervous system is fast - especially reflex actions. Can respond in a few mili/seconds
Hormone responses are slow, except for adrenaline
5. WHAT is targeted?
Nervous impulses only target the effector muscle or gland
Hormones can target several organs
6. HOW LONG does the response last
Responses of the nervous system are temporary, such as the contraction of a muscle
Hormonal responses can be permanent, such as changes brought about in puberty
Which hormones are used in the menstrual cycle?
1. The pituitary secretes FSH
This hormone stimulates egg maturation and the release of OESTROGEN
2. The ovaries secrete OESTROGEN
This hormone causes the uterus lining to thicken. It stops the production of FSH and stimulates the production of LH
3. The pituitary secretes LH
This hormone stimulates ovulation
Oestrogen levels decrease because no FSH is produced. This stimulates FSH production again.
Explain the reflex pathway of someone who touches
1. The pin is the stimulus.
2. Receptors in the skin - such as pain - detect the stimulus
3. A message is sent in the form of a nervous impulse along the sensory neurone
4. The impulse crosses a synapse. A chemical called a neurotransmitter crosses the gap. The response is fast because there are few synapses in the pathway
5. The impulse enters a relay neurone in the CNS
6. The CNS sends a message along the Motor Neurone
7. The impulse reaches the effector: the arm muscle
8. The impulse causes the effector muscle to contract
9. The arm moves away from the pin
Adaptations of Extremeophiles
Extremeophiles are organisms that can survive in areas with extreme conditions.
1. No light - communities survive because the producers are chemosynthesizing bacteria
2. Very hot - special proteins are not denatured by high temperatures
3. Very cold - bacteria contain a special red pigment that absorbs radiation
4. Too many nutrients - microorganisms have lots of sugar in their cells to prevent osmotic effects
5. Very little oxygen - anaerobic respiration takes place
Adaptations of Plants
1. Rainforest - leaves are waxy, curled and have a tip that allows water to run off preventing damage from weight of water.
Short plants have large thin leaves with a large surface area and high concentration of chlorophyll to maximise the absorption of light
2. Cold - plants have a rounded shape for insulation and to prevent the formation of ice crystals in cells
Coniferous tree branches allow snow to slide off preventing damage from the weight of snow
3. Desert - wide or deep root systems to maximise water absorption
Succulents have thick leaves for storing water for droughts
Transpiration rate slowed by having no leaves but stomata in the stem, or burying stomata in ridges, or placing hairs around the stomata
4. Few nutrients in the soil - plants catch and eat insects e.g. Sundew plants
5. Others - bluebells flower early before plants come into leaf to avoid competition for light for photosynthesis
Dandelions have large leaves which compete well with grass, and grow quickly when cut
6. Preventing being eaten - spikes on cacti
Cloning of Animals
There are two methods of cloning animals:
1. EMBRYO SPLITTING
An embryo is split into several balls of cells which are all implanted into host mothers.
Often used for cloning animals, such as the calf of a prize cow.
It is quicker that natural breeding, produces lots of babies from one, can ensure babies are the offspring of prize animals
2. ADULT CELL CLONING
Nucleus of a stem cell, eg skin, removed.
Skin nucleus implanted into 'empty' egg cell
Electric shock causes egg cell to divide by mitosis
Embryo can be implanted in host mother, embryo splitting can be carried out or can be used to produce organs for therapeutic cloning
The clone is genetically identical to the organism that the skin cell was removed from
This method can be used to save animals from extinction but their are worries about using the technique to clone humans.
It limits the gene pool
What are the stages in drug testing?
New drugs must be stable, safe, effective and able to be taken and removed from the body.
There are four stages in drug testing:
1. Testing for toxicity. The drug is tested on tissues, then animals and pregnant animals to make sure it isn't harmful. It is important to test on pregnant animals to see the effects on unborn babies
2. The first clinical phase involves testing on a small number of healthy people to establish the side effects of the drug
3. The second clinical phase involves testing on a small number of patients to establish the optimum dose
4. The third clinical phase involves testing on lots of patients to establish the effectiveness of the drug. The clinical phases use double-blind trials, where neither the doctor nor patient know who has been given a placebo (fake)