biology paper 2 Flashcards
excersixe and increased heart rate
exercise increase the carbon dioxide in blood
detected by chemoreceptors in the carotid artery
impulses sent to the cardiac control centre
along the sympathetic nervous system
noradrenaline stimulates the SA node
why is higher light intensity required in ganglion than bipolar
more rods connect to bipolar but one cone connects bipolar cells therefore retinal convergance so depolarisation occurs in bipolar ces
rods have more pigments than cones
how is an epsp stimulated
impulse arrives at presynaptic terminal
calcuim chanels open
vesicles move to presynmaptic membrane
exiatory neurotransmiter diffuses acroos synapse
binding to receptors on postsynaptic memrbane opening sodium channels
myogenic stimulation of heart
(myogenic means) no external nerve impulses
(contraction initiated by) SAN
{depolarisation / wave of excitation} causes {atria to contract / atrial systole}
delay at the AVN
(depolarisation) through the {bundle of His / Purkyne
fibres}
(depolarisation) causing {ventricle to contract /ventricular systole} from base/apex of heart
how does paralytics affect the pd of a neurone
lower change in pd
no action potential
voltage gates sodium channels do not open
sodium ions cannot pass through membrane
no nerve impulses to muscles
latency
virus genome incorperated into host cell
virus is dormant
reporduces when cell reproduces
genetic diagram question
parent genotype
possible genotypes
percentage
seed banks
-variety of seeds from each species are kept
kept at low temperature
-kept in low humidity
kept in airtight containers
seeds tested for viability
structure of glycogen uses
glucose molecules joined {1,4 glycosidic} bonds
compact for storage
branched for rapid / breakdown
{large / insoluble} molecule which does not affect osmosis
primary succession
colonisation of bare rock by pioneer species that withstand low water
primary succession occurs
soil produced
therefore provides minerals for plants to
grow
provides niches / food / habitats for animals
climax community
emerging
how do birds increase biodiversity
carry/move seeds
excretion carries minerals
negative feedback in control of blood plasma after drinking
blood has a high(er) water potential)
detected by {osmoreceptors / hypothalamus}
therefore less ADH released by pituitary
collecting duct is less permeable
therefore less reabsorption of water
how does mass flow account for movent of sugars
- sugars are pumped into phloem sieve tubes in leaf
- lowering water potential so that water enters phloem
- pressure in phloem increases
- sugars are converted to (insoluble) starch in root cells
- increasing the water potential, so water moves out
variation in meiosis
crossing over
* which swaps DNA / genes between
homologous chromosomes
* independent assortment because it is random movement of homologous
chromosomes to poles
haploid cells
chromasome is same as chromatid
