paper 2 biology Flashcards
process of menstruation cycle
1) FSH by pituitary gland, egg maturation, stimulates ovaries to produce oestrogen
2) oestrogen causes lining of uterus to thicken, stimulates production of LH, inhibits release of FSH
3) LH by pituitary gland, ovulation
4) progesterone in ovaries by remains of the follicle after ovulation, maintains lining of uterus, as level falls, lining breaks down, inhibits release of FSH and LH
process of how the CNS coordinates a response
1) stimulus
2) receptors detect stimuli
3) sensory neurons carry the info from receptor to CNS
4) CNS decides what to do about it
5) CNS sends the info to the effector along motor neurones
6) effector carries out response
describe the reflex arc
1) stimulus detected by receptor
2) impulses sent along a sensory neuron to the CNS
3) impulses reach synapse between sensory neuron and relay neuron
4) they trigger chemicals to be released, chemicals cause impulses to be sent along the relay neuron
5) impulses then travel along motor neuron via a synapse
6) impulses then reach effector and it carries out response
controlling blood glucose levels when too high
1) too much glucose in blood
2) insulin secreted by pancreas
3) insulin causes glucose to move from the blood into the liver and muscle cells
4) liver turns glucose into glycogen
5) blood glucose level returns back to normal
Controlling blood glucose levels when too low
1) too little glucose in blood
2) glucagon secreted by pancreas
3) liver turns glycogen into glucose
4) glucose released into blood by the liver
5) blood glucose increased
IVF process
1) mother is given FSH and LH to stimulate maturation of several eggs
2) eggs are collected from mother and fertilised by sperm from feather in laboratory
3) fertilised eggs develop into embryos
4) once the embryos are a tiny ball of cells, one or two embryos are inserted into the mother’s uterus (womb)
meiosis
1) Copies of the cell’s genetic information are made forming 46 pairs of chromosomes
2) in the 1st division, the chromosome pairs line up in the centre of the cell
3) the pairs are then pulled apart so each new cell has one copy of each chromosome with 46 chromosomes
4) in the 2nd division, the chromosomes line up again in the centre of the cell and the arms of the chromosomes are pulled apart
5) this forms 4 genetically different gametes each with only a single set of chromosomes in it (23)
describe the theory of evolution by natural selection
1) Within a population, there is wide phenotypic variation
2) the organisms with the most suitable characteristics for the environment would be most likely to survive in the ecosystem
3) the organisms that survive are more likely to reproduce and pass on the genes for their characteristics to their offspring
4) these offspring also breed and continue to pass down the favourable characteristics
5) organisms that are less well adapted would be less likely to survive and reproduce so less likely to pass their genes to next generation
6) overtime, the adapted phenotype would become more common within the population and the species evolves
selective breeding process
1) from the existing stock, select the ones which have the preferred characteristics
2) breed these stock with each other
3) select the best offspring and breed them together
4) continue this process over several generations and eventually all offspring will have this characteristic
how genetic engineering is used to transfer genes between organisms
1) a useful gene is isolated and cut from an organism’s genome using enzymes and is inserted into a vector
2) the vector is usually a virus or bacterial plasmid
3) when the vector is introduced to the target organism, the useful gene is inserted into its cells
how fossils are formed from the gradual replacement by minerals
1) parts of animals and plants which don’t decay easily last a long time when buried
2) they’re eventually replaced minerals as they decay forming a rock-like substance shaped like the original hard part
3) the surrounding sediments also turn to rock, but the fossil stays distinct inside the rock and someone digs it up
how fossils form from casts and impressions
1) when an organism is buried or died in a soft material, the material hardens around it
2) the organism then decays leaving a ast of itself
3) footprints can also be pressed into soft materials when soft, leaving an impression when it hardens
water cycle
1) energy from the sun makes water evaporate from the land and sea turning it into water vapour
2) water also evaporates from plants known as transpiration
3) the warm water vapour is carried upwards, as it gets higher up it cools and condenses to form clouds
4) water falls from the clouds as precipitation onto land
5) this provides fresh water for plants and animals
6) this water then drains into the sea, before the whole process starts again
carbon cycle
1) CO2 is removed from the atmosphere by green plants and algae during photosynthesis
2) This carbon is used to make glucose, which can be turned into carbohydrates, fats and proteins which make up the plant’s and algae’s biomass
3) when the plants and algae aerobically respire, some carbon is returned to the atmosphere as CO2
4) when plants and algae are eaten by animals, some carbon becomes part of the fats and proteins of their bodies
5) the carbon then moves through the food chain
6) animals then respire and carbon is returned to the atmosphere as CO2
7) when plants, algae and animals die microorganisms feed on their remains and decompose them
8) when these decomposers respire, CO2 is returned to the atmosphere
9) in some conditions, decomposers cannot function properly, leading to the carbon in dead remains being converted to fossil fuels
10) the combustion of fossil fuels releases CO2 back into the air
