Paper 2 Flashcards
How do you investigate respiration?
add some soda lime granules to 2 test tubes, this absorbs the CO2 produced by respiration. Place a ball of cotton wool above the soda lime, then add woodlice on top of the cotton wool in one test tube, whilst glass beads with the same mass as the woodlice are placed within the other test tube to act as a control. Afterwards, set up a respirometer. Then use a syringe to set the fluid in the manometer to a known level. The apparatus is then left for a set amount of time in a water bath set to 15C. During this time, there’ll be a decrease in the volume of air with the woodlice as they respire (since the soda lime will absorb the CO2). The decrease in volume of air also decreases the pressure, this causes the coloured liquid in the manometer to move towards the test tube containing the wood lice. The distance moved by the liquid in a given time is measured. This value can then be used to determine the volume of oxygen taken in per minute. Repeat this experiment with different temperatures.
How do you measure the amount of organisms in a set area?
Firstly place two tape measures out in the shape of a Y and X axis, using a random co-ordinates generator, go to the set of co-ordinates and place the quadrat down. Then count all the organisms you’re interested in within the quadrat, record this number. Repeat the experiment 4-6 more times. Work out the average number of organisms in each area. For an estimated population size multiple the average by the total area you were measuring.
What is eutrophication?
Firstly, the fertilisers that farmers used are washed into rivers and lakes when it rains. The excess nitrates from the fertilisers causes the algae to grow rapidly and block out the light. Since the underwater plants now can’t photosynthesise due to lack of light, they die off. Due to more food now being available, decomposers rapidly reproduce and use up the available oxygen when they aerobically respire. This means that other underwater organisms that respire (eg fish) die off too since they now can’t respire.
what are some examples of mutualism?
Sea anemones and clown fish:
Clown fish hide in the sea anemones stinging tentacles for protection, in return the clown fish provide nutrients for the sea anemones in their faeces
Algae and coral animals:
The coral animals allow algae to grow inside them, providing protection from predators. In return the algae provide food for the coral animals, which they make when they photosynthesise
Nitrogen fixing bacteria and pea plants:
The nitrogen fixing bacteria are protected in the nodules of the pea plant, in return the plant receives nitrates, which it needs for growth.
what happens inside the nephron?
Stage 1 - Filtration:
The blood flows into the glomerulus, here small molecules (urea, glucose, salts, water) are forced out the glomerulus and into the bowman’s capsule. This liquid is known as the filtrate.
Stage 2 - Selective Reabsorption:
The filtrate flows into the first convoluted tubule. Here useful substances (glucose) are reabsorbed into the capillaries, this is done by active transport. This does mean that no glucose should normally be left in the urine.
Stage 3 - Water reabsorption:
Water is reabsorbed by osmosis in the loop of Henle and collecting duct. The amount of water reabsorbed is dependent on ADH. More mineral ions are then absorbed in the second convoluted tubule.
what happens when the thyroxine level strays away from normal?
When the blood thyroxine level is less than normal the hypothalamus is stimulated to release TRH (thyroxine releasing hormone). TRH then stimulates the pituitary gland to release TSH (thyroxine stimulating hormone). TSH stimulates the thyroid to release thyroxine, so the thyroxine level returns to normal.
When the blood thyroxine level becomes higher than usual, the release of TRH is inhibited, which reduces the production of TSH, so the blood thyroxine level falls.
what hormones are released during the menstrual cycle and why?
Firstly FSH is released by the pituitary gland, it causes a follicle to mature in one of the ovaries, which stimulates oestrogen production. This oestrogen production causes the lining of the uterus to thicken and grow, a high level causes an LH surge. This LH is released by the pituitary gland, it stimulates ovulation at day 14 - the follicle ruptures and the egg is released. The ruptured follicle develops into a corpus luteum, which secretes progesterone. This progesterone maintains the uterus lining, whilst also inhibiting the production of FSH and LH.
Devise a plan to investigate the effect of light intensity on the rate of photosynthesis
1) place a white light source a set distance away from the conical flask that contains some pondweed.
2) leave the pondweed to photosynthesise for a set amount of time
3) as the pondweed in photosynthesising the oxygen produced from the photosynthesis will collect in the gas syringe
4) jot down the volume of oxygen produced and repeat the experiment at a range of different distances from the light source.
5) The higher the light intensity, the more photosynthesis should occur.
Explain how hormones control the menstrual cycle
- FSH = released by the pituitary gland
- oestrogen = released by the ovaries
- LH = released by the pituitary gland
- progesterone = released by the corpus luteum
Once the FSH is released, it stimulates a follicle to mature and be released from an ovary, it also stimulates oestrogen production. The oestrogen rebuilds the uterus lining from the previous menstruation period, and in high enough concentrations, triggers an LH surge. This LH surge leads to ovulation, where the follicle releases the egg so it can travel through to the uterus, the LH then breaks the follicle into a corpus luteum. This corpus luteum secretes progesterone, which maintains the uterus lining and inhibits the production of FSH and LH. This makes it so that there isn’t multiple eggs at once. If the egg is fertilised progesterone levels stay high to maintain the uterus lining, if not, menstruation occurs and the uterus lining is shed.
Explain how the human body maintains blood glucose levels within a narrow range
After eating the blood glucose levels spike, so the pancreas release insulin into the blood. This makes the liver store the glucose as glycogen, making the glucose levels return to normal.
After exercise the blood glucose levels tend to drop, so the pancreas releases glucagon into the blood, making it so that the liver releases its glucose store, causing glucose levels to return to normal.
Describe how the water content in the blood is controlled in the nephron
Different amounts of ADH are released into the bloodstream according to the concentration of water in the
blood plasma
. ADH is released by the pituitary gland when the blood is too concentrated and it causes the kidney tubules to become more
permeable
. This allows more water to be reabsorbed back into the blood during selective reabsorption.
If a person has consumed a large volume of water and has not lost much as sweat, too much water might be detected in the blood plasma. If this occurs, less ADH will be released, which results in less water being reabsorbed and a dilute and larger volume of urine will be produced.
Explain using Ficks law the factors that affect the diffusion rate of molecules in and out of cells
Ficks law states that:
rate of diffusion is directly proportional to (surface area x concentration difference) / thickness of membrane
This means that increasing the surface area or concentration, increases the rate of diffusion, as they are directly proportional. This also means that increasing the thickness of the membrane, decreases the rate of diffusion, as they are inversely proportional. Increasing the surface area also increases the rate of diffusion as there is more space available for reactions and movement. Also, the larger the concentration gradient, the faster the rate of diffusion.
