more biology model answers

excercise causes an increase in heart rate, describe the role of receptors and of the nervous system in this process

• chemo receptors detect a rise in carbon dioxide and so a fall in pH

• sends impulses to the cardiac centre

• more impulses to the SAN

• by the sympathetic nervous system

explain why an increase in biomass can be taken as a measurement of net primary productivity

represents dry mass, represents gross production minus respiratory losses

what is meant by phenotype

genetic consititution and the expression due to the environment

what is a gene pool

all the alleles in a population

how does sympatric speciation occur

• occurs in the same habitat

• mutations cause different fertile times

• reproductive isolation so no gene flow

• different alleles passed on, so change in frequency of allels

• disruptive selection

• eventually different species cannot interbreed to produce fertile offspring

describe and explain how succession occurs

• colonisation by pioneer species

• pioneer species change the enviroment

• making it less hostile for other species

• changes, or increases biodiversity

• to climax community

explain how a decrease in the concentration of calcium ions within muscle tissues could cause a decrease in the force of muscle contractions

• less tropomyosin moved from binding site

• fewer actin myosin cross bridges formed

• myosin head does not move

• less ATP hydrolase

explain how inhibiting adenylate cyclase may help lower the blood glucose concentration

• less ATP will be converted to cyclic AMP

• so the enzyme protein kinase will not be activates so less glycogen will be hydrolysed into glucose

describe what happens during photoionisation

• chlorophyll absorbs light

• light excites electrons in the cholrophyll

• electrons are lost

what is a DNA probe

short single strand of DNA

bases complementary with DNA

suggest and explain how the interaction between the muscles labels in figure one could cause the pupils to constrict

circular muscles contract

radial muscles relax

how can an eagle see its prey in detail due to the high density of cones

• high visual acuity

• cone is connected to a single neurone

• separate impulses to the brain

why some light isn’t photosythesised

• light is reflected

• light is wrong wavelength

• light misses chlorophyll

how could you produce a calibration curve

• use water and (solution your testing ) to produce a dilution series

• add the deleting

• using a known volume of a solution

• record absorbance using a colorimeter

• plot dilution on calibration curve

describe how you could determine a concentration of creatine in a sample of urine using a calibration curve

• use same volumes of solution as used in producing calibration curve

• read off concentration against absorbance obtained

describe the sequence of events involved in transission across a cholinergic synapse

• depolarisation of presynaptic membrane

• calcium channles open and calcium ions enter

• synaptic vesicles move to fuse with presynaptic membrane and release acetyl choline

• acetylene choline diffuses across synaptic cleft

• it attaches on postsynaptic membrane

• sodium ions eneter neurone leading to depolarisation

use IAA to explain the growth of a shoot tip towards light

• tip produces IAA

• IAA diffuses into shoot

• elongation of cells on one side more than the other

descrive and explain how the PCR is used to amplify a DNA fragment

• DNa polymerase, nucleotides and primers required

• heat to 95 to break hydrogen bonds

• reduce temperature to 55 so primers bind to DNA

• increase temperature, DNA polymerase joins nucleotides and repeate method

describe the light interdependent reaction of photosynthesis

• carbon dioxide combines with RuBP

• produces two gylcerate phosphate using rubisco

• GP reduced to tripse phosphate

• using reduces NADP

• using energy from tap

• trips phosphate converted to glucose

give two reasons why the transission across a cholinergic synapse is unidirectional

• presynaptic neurone has acetyl choline

• post synaptic neurone has receptors

describe the effect of ADH on the collecting ducts in kidneys

• stimulates increase in addition of channel pritens to the membrane

• increases permeability to water

• by osmosis

three features of how the cells In the proximal convoluted tubule allow the rapid reabsorption of glucose into the blood

microvilli provide a large surface area

mamy carrier protiens for facilitated diffusion

many mitochondria produce ATP

suggest two reasons for conserving rainforests

• conserve species, for biodiversity

• reduces climate change

give three reasons for the low efficiency of energy transfer from secondary consumer to tertiary consumer in an ecosystem

• heat loss from respiration

• food not digested

• excretion