Paper 2 Flashcards
(232 cards)
1
Q
what are the products of the light dependant reaction
A
ATP and NADP
2
Q
What are the processes of LDR
A
1.photolysis
2.chemiosmosis
3.photoionisation
4.ATP formation
3
Q
where does the light dependant reaction takes place in the chlorolast
A
in the thylacoids (grana)
4
Q
where does the light independant reaction take place
A
in the stroma
5
Q
what are the limiting factors for photosynthesis
A
temperature,light intensity and c02 concentration
6
Q
What are the 4 steps of aerobic respiration
A
Glycolysis, Link,Krebs,Oxidative Phosophorylation
7
Q
Where in the mitochondria do these steps occur
A
glycolysis in the cytoplasm
link-mitochondrial matrix
krebs-mitochondrial matric
oxidative phosphorylation- mitochondrial inner membrane cristae
8
Q
what are receptors what do they do and which ones do u need to know about
A
receptors detect stimuli
each receptor is specific to a stimuli-stimulation leads to the creation of a generator potential which is capable of causing change
pacinian corpuscle- pressure receptor
rods and cones
9
Q
what happens when pressure is applied to the pacinian corpuscle
A
when pressure is applied the plasma membrane of the neurone difforms, stretches and widens the Na+channels threby Na+ can diffuse into the neurone so a generator potential created
10
Q
Rods
A
-process images in black and white
-have poor visual acuity- this means that the brain can not distinguish between seperate sources of light
-can detect light of very low intensity asd many rod cells connect to one sensoty neurone (retinal convergence)
11
Q
Cones
A
process images in colour
there are three types which contain different types of iodopsin pigment (red,green,blue) which all absorb different wavelengths of light
iodopsin is only broken down if theirs high light intensity so action potentials can only be generated with high enough light intensity
12
Q
define trophism
A
refers to when plants respond to stimuli via growth
13
Q
what are the different types of trophism
A
phototrophism- in responce to light
gravitophism-gravity
positive and negative grwoing towardr against the stimulus
14
Q
Whats trophism controlled by?
A
Growth factors- IAA
15
Q
Whats IAA
A
its a type of auxin which controls cell elongation in shoots and inhibits growth of cells in roots. it is made in the tips of roots and shoots but can diffuse to other parts
16
Q
wheres IAA produced
A
its produced in the tips of shoots and roots however it can diffuse to other cells
17
Q
explain the process of phototrophism in shoots
A
shoot tip cells produce IAA which causes cell elongation
The IAA diffuses to other cells
if their unilateral light the IAA will diffuse towards the shaded side of the shoot resulting in higher concentration of IAA there
this causes the cells of the shaded side to elongate towards the light source
18
Q
Explain phototrophism in roots
A
because roots do not photosynthesise they do not require light.their role is to ancher the roots deep into the soil
so in roots high concentration of IAA inhibits cell elongation causing, cells elongate on the light side so they bend against the light source
this is negavtive photrophism
19
Q
define taxis
A
when an organism moves their entire body towards a favourable stimulus or away from an unfavourable stimulus
when an organism moves towards the favourable taxis its referred to as positive taxis
miving away- negative taxis
20
Q
define kinesis
A
when an organism changes the speed of movement and rate it changes direction
20
Q
whats the rate of contraction of the heart controlled by
A
an electrical wave of activity
21
Q
whats refered to as the pacemaker in the heart
A
the sinoatrioal node which is located in the right atrium
22
Q
wheres the atrioventricular node?
A
still within the atria but within the borders of the atria and the ventricles
23
Q
which part of the brain controls the rate of the contraction in the heart
A
the medulla oblongata via the autonomic nervous system
24
what are the two parts of the regulation of heart rate
to increase heart rate theirs a centre linked to the sinoatrial node via the sympathetic branch
to decrease heart rate thia the parasympathetic branch
25
what stimuli cause changes to the heart rate
responds in responce to ph and blood pressure
25
where are chemoreceptors and pressure receptors found
found in aorta and carotoid arteries
26
describe the heart responce to change in ph(lowered ph)
The Ph of the blood will decrease during times of high respiratory rate due to the production of carbon dioxide and lactic acid. excess blood must be removed from the blood in order to prevent the denaturing of enzymes
this is achieved by increasing the heart rate more impulses send via the sympathetic branch of nervous system so carbon dioxide can diffuse into the alveoli
27
describe what happens if pressure is too high
28
define speciation
the process which results in the creation of new species
29
whats geographical seperation
allopatric speciation
30
what type of speciation is caused by changes in the reproductive mechanisms caused by behaviour
sympatric speciation
31
Whats GPP?
is the chemical energy store in plant biomass in a given area or volume. it is the total energy resulting from photosynthesis
32
whats net primary production
the chemical energy stored in a plant biomass taking into account the energy lost due to respiration
33
equation for npp
npp=gpp-r
34
npp is equation for consumers
N= I- (F+R)
i- the chemical energy in ingested food
the chemical energy lost of the environment in faeces and urine
r=respiratory losses
35
what are rates of productivity recorded in
kJ ha-1 year-1
kj because thats the standard unit or energy but this also include per unit area and per year
it is recorded as per unit area to standardize the resuults to enable environments to be compared- takes into account that different environment will vary in size
the units are also per year to take into account the impact of seasons- rainfall,light heat. it provides an annual average to allow comparison
36
why cant plants and animals obtain N2 through gas exchange
due to nitrogen's triple bond and we dont have the enzymes to break these bonds
37
which biological molecules contains n2
proteins, atp, nucleic acids
38
what are the key processes in nitrogen cycle
ammonification, nitrification, nitrogen fixation, denitrification
39
whats the process of converting nitrogen gas into ammonia and what does it involve.
nitrogen fixation
nitrogen fixing bacteria found in leguminous plants directly convert n2 gas into ammonia. or free living nitrogen fixing bacteria in soil
40
what happens after ammonia is produced
nitrification. this is when nitrifying bacteria oxidise ammonium into nitrites then oxidise further into nitrates. nitrates can then be absorbed by active transport into plants roots and then animal can absorb via digestion and absorption.
41
-------- will be breaking down the nitrogen containing compounds in the dead plants or animal material and in the waste produced
waste- urea dead plants and animal material- proteins
decomposers (aerobic and anaerobic bacteria fungi) breakdown the proteins to release nitrogen and it converts back to ammonium
42
what happens if theirs lack of oxygen in the soil
anaerobic denitrifying bacteria taking over. nitrates converted back to nitrogen gas
43
what is phosphorus used for in organisms
DNA,RNA, ATP, phospholipid bilayer
44
where is phosphorus mainly found
found as a phosphate ion, in mineral form in sedimentary rocks
45
# mutualistic relationship
what are mycorrhizae
fungal associations between plant roots and beneficial fungi
46
how are mycorrhizae beneicial for plant growth
* the fungi increase the surface area for water and mineral absorbtion
* the mycorrhizae acts like a sponge so holds water and minerals around roots
* this makes plants more drough resistant and ablw to take p inorganic ions
47
phopshorus cycle steps
1.phosphtae ions in oceansd or soil
2.plants can absorbe the phosphate ions through root hair cells via active transport
3.animals will then eat the plants so they consume and absorbe the material to get the phosphtae ions
4.animals excrete= releasing phosphorus back into oceans or soil in form of phosphate ions
5.decomposition from animal remains - animals brken down (ones that have bones) eroded to release phosphate ions
48
# mineral deficinet soils
fertilisers
chemicals added to the soil to replace the nitrate and phosphate ion lost when planst are harvested and removed from nutrient cycycles
49
types of fertiliser
natural-animal manure
artificial- solubkle chemicals (inorganic chemicals) exact proportions
50
pros and cons of natural and artificial fertilisers
natural fertilisers are cheaper and often free if the farmer also owns animals
however the **exact minerals and proportions cannot be controlled. **
wheras artificial fertilisers **contain exact proportions of minerals **
inorganic substances are **more water soluble** and therefore more of these **ions dissolve in the water** surrounding the soil
whilst this is an advantage to the** plant for absorbing the nitrates and phosphtates** the downside is thsat their high solubility means that larger quantities are washed away with rainfall and therefore have a greater impact on the enviorment
51
leaching
when water soluble compounds are washed away often intio rivers and ponds
if nitrogen fertilisers leach into waterways it causes eutrophication
52
eutrophication
when nitrates leached from fertilisers **stimulate growth** of **algae** in a pond
* the excessive growth of **algae creates a blanket **on the surface of the water which blocks out light
* as a result plants below cannot photosynthesis and die
* bacteria within the water feed and respire on the dead plant matter
* this results in an increase in bacteria which are all respiring and using up the oxygen within the water
* eventually fish and other aquatics organisms die due to the lack of dissolved oxygen in the water
53
stimulus
detectable change in the enviornment detected by receptors
54
# negative so moving up
gravitophism in shoots
IAA will diffuse from the upper side to the lower side of a shoot
if a plant is vertical this causes the plants cells to elongate and plant grows upwards
if a plant is on its side it will cause the shoot to bend upwards.
55
# positive
gravitosphism in roots
IAA moves to the lower side of roots so that the upper side elongates and the roots bend downwards towards gravity and anchors plant in
56
a relex
rapid,automatic response to protect you from fanger
57
how is a generator potential established in rods
the pigment rhodopsin must be broken down by light
58
what gives cones high visual acuity
each cone cell is connected to A SINGLE BIPOLR CELL therefoe brain can seperate between different sources of light
59
control of heart rate step by step
* san releases a wave of depolarization across the atria causing it to contract
* once the first wave of depolarization reaches the AVN the AVN releases a second wave of depolarization.
* a non-conductive layer prevents between the atria and ventricles prevents the wave of depolarization travelling down to the ventricles
* instead the bundle of his conducts the wave of depolarization down the septum and pyrkyne fibres
* as a result the apex and then walls of the ventricles contract. there is a short delay before this happens whilst the avn transmits the second wave of depolarization
* this allows enough time for the atria to pump all the blood into the ventricles. finally the cells repolarize and the cartdiac muscle relaxes
60
what part of the brain controls the heart rate
the medulla oblongata via the autonomic nervous system
61
to increase heart rate
centre connected to sinoiatrial node to increase heart rate via the sympathetic branch
62
to decrease heart rate
centre connected to sinoatrial node- via parasympathetic ns
63
what two things does heart rate change in responce to
and what are these stimuli detected by
pressure and ph
chemoreceptors and pressure receptors
64
where are chemoreceptors and pressure receptors found
aiorta and carotid artery
65
describe the responce to ph in heart rate control
* during times of high respiratory rate the blood ph decreases, thius is because of the production of lactic acid and carbon dioxide.
* the excess acid must be removed from the blood rapidly in order to prevent enzymes denaturing
* this is achieved by increaseing th heart rate- more impulses via sympathetic branch to san released so carbon dioxide can more rapidly diffuse out the alveoli
66
whats the risk of high blood pressure and howis it brought back to normal
high blood pressure can cause damage to the walls of the arteries so its important to put mechanisms in place to reduce blood pressure
more impulses are send via the parsaympathetic nervou system in order to decrease heart rate
67
whats the risk of low pressure
unsufficient supply of oxygen to respiring cells and removal of waste
so increased impulses via the sympathetic branch in order to invcrease heart rate
68
what does the cell body of a neurone contain
all the organelles youd find in a normal cell
proteins and neurotransmitters are made there
69
dendrites
carry action potential to surrounding cells
70
axon
the conductive long fibre that carries the nervous impulse along the motor neurone
71
shwann cells
wrap around the axon and form the myelin shleath which a lipid non-conductive. so doesnt allow charged ions through
72
resting potential
when a neurone isnt conducting an impulse
**theirs a difference in electrical charge inside and outside the neurone **
there are morre positive ions Na+ and K+ outside than inside therefore the inside of neurone is comparitevely negtaive than outside
-70mv
73
how is the resting potential maintained
a sodium potassium pump maintains the resting potential. involves active transport using atp
this pump moves 2ka+ inside whilst 3na+ out
this creates an electrochemical gradient causing K+ to diffuse out whilst NA+ moves in
however the membranbe is more permeable to potaassium so more move out
74
action potential
when the neurones voltage increases beyond a set point from resting potential
an increase in voltage (depolarization) is due to the neurone membrane being more permeable to Na+
75
all or nothing principle
if depolarization doesnt exceed -55mv (threshold value) and action potential is not generated and theirs no impulse
however any stimulus which reaches depolarization -55mv will always peak at the same maximum voltage
## Footnote
this is important as it ensure that animals are responding to larger stimuli rather than every slight change of the environment
76
what do bigger stimuli do
they increase the frequency of action potentials
77
what happens after an action potential has been generated
the membrane eneters a refractory period where it cant be stimulated because sodim gates channelsa re recovering
78
three reasons the refractory period is important
1. an action potential can not be genberated after another this makes sure that each is seperate
ensures discrete impulses are created
2. it ensures that action potentials travel in one direction. this prevents the action potential of spreading to two different directions which might prevent a responce
3. it limits the number of impulse transmission so prevents overeaction to atimulu
79
factors affecting the speed of conductance
axon diameter
temperature
myelination and saltatory conduction
80
myelination and saltatoru conduction effect of transmission
the AP can jump fron node to node which means that ap travels along the axon faster
81
axon diameter effect
the wider the diameter the faster the rate of conductio
this is because theirs less leakage of ions out
82
temperature effect on conduction
higher temperature increases the speed of conduction for 2 reasons
1. ions diffuse faster
2. the enzymes involed in respiration work faster so more production of ATP. so more ATP for active transport of na and k pump
83
synapse
gaps betwen the end of the axon of one neurone and the dendrite of another. here the AP is transmitter via neurotransmitters which diffuse across synapse #
84
function at synapse steps
1. *action potential arrives at synaptic knob *
2. AP causes the synaptic knob to become* depolarised *which leads to the opening of calcum channels. *calcium diffuses into the synaptic knob*
3. the calcium ions cause the vesicles which contain* neurotransmitters to fuse *with the presynaptic membrane therefore releasing neurotransmitters in synaptic cleft
4. neurotransmitters diffuse down conc gradient across synaptic cleft to post synaptic membrane. t**hey bind to complementary in shape receptor**s on the surface of post synsptic membrane
5. sodium channels on post synaptic membrane open and na diffuses in . if enough diffuses in to reach threshold and exceed it then post synaptic membrane will depolarise
6. ap generated in post synaptic so travels
7.
85
unidirectional transmission
the vesicles containing the neurotransmitters are only found on pre synaptic neuron
cocn gradient etsablished so diffusion will be from pre to post
the receptors are alwatys on post synaptic neurone
86
what does a cholinergic synapse involve. what type of neurotransmitter
## Footnote
acetylcholinesterase
**acetylcholine **
binds to its receptor. however not permanently bound because this means that the sodium channels will be continually open and continually triggering an action potential and a responce even tho stimulus isnt there anymore
so their is an enzyme whihc will breakdown acetylcholine (neurotransmitter) into choline and acetate which can be reabsorbed by pre synaptic neuroine and reabsorbed
87
whats acetylcholine broken down into
acetate and choline
88
inhibitory synapse
inhibitory synapses cauases chloride i
89
types of summation explained
summation is the rapid build up of neurotransmitters at a synapse which helps to generate an action potential
*smatial summation is when **many different neurons** collectively trigger a new action potential by combining the **neurotransmitters they release to exceed threshold value.
temporal summation- is when one neurone release neurotransmitters rapiudly over shor period of time to add up enough to exceed threshold
90
what happens at inhibitory synapses
inhibitory synapses causes chloride ions to move into postsynaptic neurone whilst pottasium ions move out into the synaptic cleft .
this makes the memvrane potentially decrease -80mv hyperpolarisation making it less likely an actoin potentil can be generated
91
neuromuscular junction
this is a synapse which occurs between a motor neurone and a muscle
92
differences and similarities between neuromusculur junction and cholinergic synapse
Both unidirectional
* cholinergic synapse can be inhibitory or excitatory whereas neuromuscualr junction is only excitatory
* cholinergic connects two neurones can be sensory and relay whereas neuromuscular is always motor and muscle connected
* neuromuscualr- this is the end point of the action potential whereas cholinergic ap geenrated again and travels along nnext neurone
* acetylcholine binds to receptors on **muscle fibre memebrane** whereas acetylcholine binds to receptors on post synapric memebrane
93
muscle fibres made up of
## Footnote
are made up of millions of myofibrils collectively bring movement
shared nuclei and cytoplasm also known as sarcoplasm and has high number of mitochondria
94
two key types of proteins involved in muscles
actin and myosin
95
positioning of A band during contraction
theirs no change in length of a band as the myosin length never moves
96
h zone
shortens decreases during contraction only contains myosin
97
# light band
i band
just actin when relaxed its bigger when it contrcts it shortens due to the overlap of action with myosin
98
what do z line indicate
the start and end of a sarcomere
z lines cloder together when contraction
98
sliding filamen theory
99
slow twitch vs fast twitch muscle fibres
Slow twitch- contract more slowly than fast twitch fibres and provide less powerful contractions but over a longer period. They’re adapted for endurance work running a marathon. (Calf muscle which must contract constantly to maintain body upright) they’re suited for this role by being adapted for aerobic respiration in order to prevent build up of lactic acid
Large storage of myoglobin (bright red molecule that stores oxygen which accounts for red colloid of slow twitch muscle fibres)
A rich supply of blood vessels to deliver oxygen and glucose for aerobic respiration
Numerous mitochondria for atp
Fast twitch adapted for powerful contractions + rapid but for short periods of time. Adapted for intense expertise (weight lifting)
Thick and more numerous myosin filaments
A high conc of glycogen
A high conc of enzymes involved in ANAEROBIC RESPIRATION which produce ATP rapidly
A store of phosphocrestinr. A molecule which can produce at from adp
100
structure of slow twitch muscle fibres compared to fast twitch
slow twitch contains a large store of **myoglobin**, a rich blood supply and many mitochondria
fast twitch- much thicker and more myosin filaments, has a large store of glycogen a store of phosphpcreating to create atp from adp and high conc of enzymes involved in aerobic respiration
101
general properties of each type of muscle fibre
slow muscle fibres contract slowerand respire aerobicsally for longder periods of timre due to the rich blood supply and myoglobin. stmf are adapted for endurance
fast twitch contract faster to provide strong bursts of powerful contractions . these are for intense excersize such as sprints and weight lifting
102
location of slow twitch and fast twitch
slow twitch- calve
fast twitch- biceps
103
function of pancreas
detects changes in blood glucose conc in the blood.
islets of langerhans release glucagon and insulin to bring levels back to normal
104
islets of langerhans consist of
alpha cells and beta cells
alpha cells secrete the hormone glucagon into blood stream in order to increase blood glucose levels (happens when blood glucose is low)
beta cells also in pancrete and part of cells of langerhans but responsible for decreasing blood glucose levels when its too huigh. beta cells produce and relesse insulin
105
adrenaline location of effect and whats the effect
adrenaline is released from adrenal glands when the bidy anticipates danger this resuls in more hydrolysis of glycogen into glucose in the liver
106
# general
when you eat food containing carbohydrates....
the blood glucose levels in blood increase. this is detected by beta cells of ilset of langerhans. beta cells then release inuslin. liver cells become more permeable to glucose and enzymes are activated to convery glucose into glycogen (insoluble store of glucose) glucose is removed from blood and stored as glycogen in cells
107
when youve been excersizing
blood glucose levels are low.this is detected by alpha cells. alpha cells releases glucagon into the blood stream. adrenal gland releases adrenaline. then the second messeneger occurs to activate enezymes to hydrolyse glycogen into glucose.
108
whats the way that insulin will decrease blood glucose
insulin **attaches to receptors** on target cells.
this results in a change to the **tertiatry structure of channel proteins** resulting in more glucose **being absorbed by fascilitated diffusion **
**more channel proteins are incorporated into cell membranes** so that so that more glucose is reabsorbed by the cells from the blood
glucose which is now in the cells will be converted to glycogen as enzymes involved in the conversion are activated
this results in** glycogenesis. **
109
whats the action of glucagon
1. glucagon attaches to receptors on target cell (liver cells)
2. when glucagon binds it causes a protein to be activated into adenyl cyclase and converts atp to cyclic AMP (camp)
3. camp activates an enzyme called protein kinase that can hydrolyse glycogen into glucose
4. activates other enzymes to convery glycerol from lipids and amino acids from proteins ionto glucose
110
# *
whats the second messenger
cyclic amp
111
glucagon and adrenaline
both secondary messenger model
112
# when glucose levels too high
role of liver
glycogenisis
converting glucose into glycogen. occurs in the liver
113
role of liver
glycogenolysis
hydrolysis of glycogen into glucose. occurs in liver due to second messenger
114
gluconegenesis
creating of glucose from other molecules like glycerol and amino acids
115
type 1 diabetes
when your unable to produce insulin
usually starts in childhood but could be as a result of an autoimmune disease affecting the beta cells. treatment involves insulin
116
type 2 diabetes
receptors on target cells loose their responsiveness to insulin. usually develops in adulthood because of obesity and poor diet. it is controlled by regulating consumption of carbohydrates,increasing physical acticity
117
osmoregulation
what happens if water potential of blood is too low (hypertonic) too much solue
water from cells will leave via osmosis causing themn to shrivel (crenation)
118
lysis
osmoregulation
hypotonic
when water potential of blood is high it will cause water to move in by osmosis
cells will become larger and burst
119
what causes blood to be hypertonic (too low water potential) and whats the corrective mechanism
dehydration
lots of ions in diet (salt)
sweating a lot
more water is reabsorbed by osmosis into the blood from the tubules (distal convoluted tubule) of the nephron. this means that urine is more concentrated as theirs less water
120
what causes hypotonic blood (high water potential) and whats the corrective mechanism
drinking too much water and not enough salt in your diet
less water is reabsorbed by osmosi by the blood from the tubules of the nephron, so water is less concentrated more diluted
121
where does osmoregulation occur
and what are the structures
in the nephron of the kidney
nephrons are long tubules surrounded by capillaries
## Footnote
blood is filetred and useful substances are reabsrobed back into the blood
122
what are the different parts of the kidney
glomerelus,
proximal convoluted tubule, descending limb and ascending limp of loop of henle, collecting duct
123
what does the glomerulusm do
filters small solutes from the blood
124
what happens in proximal convoluted tubule
water,ions,nutrients afe reabsorbed toxins are removed and ph adjusted
125
descneding limb of loop of henle
aquaporins allow water to pass from the filtrate into the intertersetrial space
126
ascending limb
reabsorbs na+ and calcium ions from the filtrate into the interterestrial space
127
why does ultrafiltration occur
it occurs due to **high hydrostatic pressure **forcing small ions and water out of the glomerulus cappilaries and into the renal capsule
128
where does selective reasborbtion occur
occurs in the proximal convoluted tubule
129
distal convoluted tubule
water moves out the distal convoluted tubule and collecting duct to return back to the blood
130
collecting duct
carried the remaining liquid (urine) to the ureter
131
what part of the brain detects changes in the water potential of the blood and produces hormone adh
hypothalamus
132
osmoreceptors
detect changes in water potential of the blood
133
what happens if water potential in blood is too low
osmorecpetors detect this and water will leave them by osmosis causing them to shrivel. this stimulates the hypothalamus to produce more of the hormone ADH
134
what hormone is involved in osmoregulation
ADH
135
what happens if water potential of blood is too high
water potential will enter the osmoreceptors and this stimulates the hypothalmus to produce less adh
136
describe the travellinf of the hormone ADH
ADH is produced in hypothalmus. then it travels to the posterior pituarity and from here its released into the capillaries and into the blood adh travels in the blood until it reaches target organ of the kidney
137
ADH effect
ADH causes an increase of the permeability of the walls of the collecting duct and the distal convoluted tubule
this causes more water to leave nephron and be reabsorbed into the blood so the urine is more concentrated
138
phenotype
the expression of the genes and interaction with environment
139
homozygous
a pait of homologous chromasomes carrying tge same alleles for a single gene
140
heterozygous
a pair of homologous chromasomes carrying different alleles for the same gene
141
co dominant
when the two alleles are equally dominant as eachother so both displayed in phenotype
142
sex linkage
a gene whos locus is on x chromasome
143
epistasis
when one gene modifies or masks the expression of another gene at a different locus
144
monohybrid
genetic inheritance cross determined by one gene
145
genetic inheritance of a characteristic based upon many genes
dihybrid
146
whats the statement you say for chi squared difference in frequency
theirs a significant difference between frequency you expect and frequency you observe.
or for a null hypothesis their is no significant difference between the expected observed frequency od the colour
the difference is likely due to chance
147
gene pool
All the alleles of all the genes within a population at a given time
148
population
all the individuals of one species in one area at one time that can interbreedb to make fertile offspring
149
hardy weinberg equation and each part explained
p2+2pq+q2=1
p- frequency of dominant allele
p2= frequency of homozygous allele dominant
q=recessive
q2= homozygous recessive gene frequency
2pq= heterozygous
150
disruptive selection
is when individuals containing allelles coding for **either extreme trait **are more likely to survive and pass on their alleles. as a result the allele frequency changes and more individuals possess the allele for the extrem trait and the middling trait allele becomes less frequenct
151
what causes speciation
continuated disruprive speciation
152
when does speciation occur
when the original population of the same species become reproductively isolated. this isolation means that theirs now two populations of the same specie which cannot breed together
accumulation of differences in gene pools occur to the extend where the species can not produce fertile offspring
153
example of sympatric speciation
random mutation occurs which impacts reproductive behaviour for example it may cause individuals to perform different courtship behaviours or being fertile at different times of the year
due to this individuals will not reproduce so there will be no gene flow between the groups within the population
overtime these reproductively isolated peopulations will accumulate different mutations to the extend where their gene are so different so theyre classified as two distinct species
154
abiotioc factors
non-living conditions in an ecosystem
155
carrying capacity
the maximum population size an ecosystem can support
156
interspecific competition
when memebrs of different species are in competition for the same resource that is in limited supply.this could be a competition oif a habitat,food,water. the individual better adapted for their envionment more likely to suceed in competition.
157
intraspecific
when individuals of the same species are competing for the same resources and mates. competition for a mate is linked to courtship rituals. individuals who have more energy will produce a more impressive ritual or may have feathers or fur in better condition
158
how would you sample motile organisms
sample using mark release recapture
159
step by step random sampling
lie two tape measures at 90% to eachother
using a random number generator to generate two coordinates
place the quadrat at coordinates and take the sample
repeat at least 30 times and collect a mean
160
what are the two types of line transects
belt transects- the quadrat is placed at every position along the tape measure
interrupted belt transect-the quadrat is placed at uniform intervals along the tape measure
161
mark release recapture method
1. an initial sample of the population in question is capture
2. these individuals are then marked and the number caught is recorded. the mark must be weather resistant
3. these marked individuals are then released again and time is given for them to disperse randomly around the habitat
4.then a second sample is recaptured
5.the total number recaptured and the number od those recaptured with the mark is recorded
6. the size of the population is then estimated
162
ethics of capture recapture
how you capture and how you mark the organism must not cause any harm
mark must be non toxic
must not increase chances of predation
must not reduce chances of reproduction
163
whats sucesssion
the change in an ecological community over time
164
how does primary succession begin
* when pioneer species colonise bare rock/sand
pioneer species such as lichen are *adapted to survive harsh abiotic* conditions and *through their death and decomposition* the abiotic factors *become less harsh* and form a thin layer of soil/humus
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primary succesion part 2 after humus/soil formed as a result of death of pioneers
*moses and smaller plants* can now survive and they *further increase the depth and nutrients within the soil.* this pattern continues and as the abiotic factors become less harsh plants can now survive and changes the environment further.*
each new specie changes the may change the envionment in such a way that it becomes less suitable for previous specie. therefore each existing specie becomes outcompeted by a new specie colony
more biodiversity less hostile envionment
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final stage of sucession
climax community- dominated by trees
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secondary succession
the succession is disrupted and the plants are destroyed
- succesion starts again however the soil is already created so we do not start from bare rock
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how to conserve habitats
succession is managed
by maintaining *earlier stages* of succesion and *preventing a climax community* a greater variety of *habitats are conserved *and therefore a greater range of species
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gene mutation
a change in the dna base sequence of a gene
- mainly occurs in dna replication
- occurs spontaneously but frequency can be increased by mutatgenic agents
- this can result in a different amino acid sequency- change in primary structure of a protein
- location of bonds ions,hydrogen,duslphide bridges will change therefore different 3d structure
- diff shape= diff function of non functioning protein
-
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6 types of gene mutations
addition,inversion,deletion,substitution,dublication,translocation of bases
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what does an addition of a base lead to
frameshift.all subsequent codons are altered. this type of mutation can be very harmful because all the altered codons can code for a different amino acid and resukt in a very different sequency of amino acids.
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what does deletion lead to
frameshift to the left. one base sequence is removed. results in a different polypeptide chain or non functioning protein
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substitution
one base is substituded/replaced by another. *this causes a change to only one codon.* and because of the degenerate feature of dna it might still code for the same amino acid therefore have no impact
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inversion mutation
a section of bases dettach from dna sequence. however when they reattach theyre inverted so section of code is back to front. this results in a different amino acid being coded for
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dublication
one partilcular base is repeated more than once. this causes a frameshift to the right. new amino acid sequence is coded for
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translocation
when a section of bases from one chromasomes dettach and attach to another chromasomes.
## Footnote
this is a substantial alteration and can cause significant impact on gene expression
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stem cells definition
undefferentiated cells which can continually divide and become specialised
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whats the process by wich stem cells become specialised
differentiation
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theirs different types of stem cells and they have different differentiation abilities- what are the 4 types
totipotent,pluripotent,multipotent and unipotent
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totipotent stem cells
| these only occur for a limited time period during embyo development
## Footnote
mammalian embryo early
can divide and produce any type of cell
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pluripotent cells
found in embros and can divide into unlimited numbers and be used in treating human disorders
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(1 type) unipotent and multipotent stem cellls
## Footnote
multipotent in bone marrow-white blood cells
are found in mature mammals and can divide to form a limited number of different cell types
## Footnote
unipotent cells make cardiomyocytes
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what technique is used to overcome tyhe ethical issues from using embrionic stem cells
induced pluripotent stem cells (IPS) can be produced from an adult somatic cell using appropriate protein transcribtion factors
to do this the gene whitch switched off to make these cells specialised are switched on
## Footnote
transcribtion factors
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control of transcribtion factors general
## Footnote
if transcrption factor hasnt bound to particular part of dna gene is inactive no transcribtion
in eukaryotes transcribtion of target cells can be stimulated or inhibited when specific transcribtion factors move from the cytoplasm to the nucleous. this can switch on or off a gene causing only certain proteins to be produced
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role of oestrogen in transcribtion
| oestrogen lipid base can diffuse through cell surface membrane
oestrogen is a steriod hormone that can initiate transcribtion by binding to receptor on transcribtion factor. when it binds it causes the transcribtion factor to slightly change shape making it complementary so it binds to dna and it initiated transcribtion
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epigenetics
is the heritable change in gene function without changing the dna base sequence. these changes are caused by the environment and can inhibit transcribtion
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increased -------- inhibits transcrbtion of dna
when ------ groups are added to DNA they attach to cytosine base
This prevents ----- from binding and attracts proteins that---- the DNA HISTONE complex
IN THIS WAY METHYLATION PREVENTS A SECTION OF DNA BEING TRANSCRIBED
methylation, methyl groups,transcribtion factors,condense
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SO INCREASED WHAT AND DECREASED WHAT INHIBITS TRANSCRIBTION
increased methylation and decreased acetylation
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decreased acetylation effect
if acetyl groups are removed from dna then the histones become more positive and are attracted more to the phosphate group of dna.
this makes the dna and histones more strongly associated anf hard for the transcribtion factor to bind
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increased acteylation and decreased methylation
transcribtion occurs
histones more loosely wrapped
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how can translation of MRNA be inhibited
by rna interferance
this is when an mrna molecule which has been transcribed gets destroyed before translated intop polypeptide chain this is done by small interfering siRNA
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process of siRNA
An enzyme can cut the the MRNA into siRNA
one strand of the siRNA combines with another enzyme
this siRNA- enzyme complex will bind via complementary base pairing to another MRNA molecule
once bound the enzyme will cut up the MRNA so cannot be translated
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what can cancer be a result of
mutations in genes which regulate mitosis
if these genes mutate and non-functionak proteins are made then mitosis is not regulated so uncontrollable cell division and tumour development
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bening tumours
*non-cancereous* because they produce ADHESIVE molecules sticking them together and to a particular tissue
often *surrounded by a capsule* so they *remain compact *and can be *removed by surgery *and rarely return
impact is localised
these can grow very large but at a very slow rate and usually are non-threatening depending on location
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# these are cancerous. grow fast and big quickly
malignant
the cell *nucleous becomes large *and they can become unspecialised cells again.
they do not* produce the adhesive layer meaning metastasise so tumour breaks off and spreads to other tissues in the body *
the tumour is *not encapsulated *so can *grow projections into surrounding tissues *and develop its own blood supply
## Footnote
can be life threatening treatment might be needed chemo etc after surgery
more likely to reoccur
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tumours develop due to
due to a gene mutation in either the tumour supressor gene or the oncogene, abnormal methylation of tumour supressor genes,oncogenes or increased oestrogen conc
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oncogenes
are the mutated version of the protoncogene
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whats the protoncogene responsible for normally
for the production of a protein involved in initistion of dna replication and cell division when the body needs new cells.
oncogene mutations can result in this process being permantly activated to make new cells
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whats the role of tumour supressor genes
tumour supressor produces proteins to slow down cell division and to cause cell death if theirs anty errors in copying of dna
if a mutation results in the tumour supressor gene not producing the proteins to csrry out this function then cell division will contiue and mutated cells will not be indentified and destroyed
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increased oestrogen conc
normally ovaries will produce oestrogen to regulate the menstrual cycle. when it stops after menopause FAT CELLS in breast tissue can produce oestrogen and this has been linked to causing breastcancer in women post menopause
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sequencing of genome
is working out the Dna base sequences fro all the dna in each cell
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sanger sequencing
type of dna sequencing
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recombinant dna
the combining of different organisms dna which could enable scientists to manipulate and alter genes to improve industrial processes.
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whats the process of making a protein using the dna technology
1. isolation of dna fragments that have the gene for the desired protein
2. insertion of the dna inside a vector
3. transformtaion of dna inside a suitabke host
4. indentification of the hosts cells that have succesffuly taken up the gene by gene markers
5. growth/cloning of population of host cells
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what are the different ways u can produce dna fragments
1. conversion of mrna into cdna using reverse transcriptase
2. using restriction endonucleases to cut fragments containing desired gene from dna
3. creating the gene in a gene machine usually based on a known protein structure #
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process of using reverse transcriptase
* a cell that readily produces the protein is selected (b cells of islets of langerhans from pancrease used to produce insulin)
*these cells have large quantities of the relevant mRNA which is therefore more easily extracted
- reverse transcriptase is then used to produce DNA from RNA. this is known as cDNA because its made up of nucleotides complementary to mrna
- single stranded cdna is isolated by hydrolysis of the mrna using an enzyme
- double stranded dna is formed on the template of cdna using dna polymerase
-
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restriction endonucleases
* are enzymes which cut the DNA
* these naturally occur in bacteria as a defence mechanism
* there are many different types of restriction enzymes that have an active site complementary in shape to a range of different DNA sequences (recognition sites) and therefore the enzyme cuts at a specific location on DNA
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blunt ends
when the restriction enzyme cuts at the same locstion
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other enzymes create a staggered cut creating ...
sticky ends
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gene machine
**when dna fragments can be created in a lab using a computerised machine.**
first- scientists examine the protein of interest to* determine its amino acid sequence *and from that work out what the *MRNA sequence* would be and then* dna equence*
DNA sequence is entered into a computer whichc checks for biosafety and biosecurity and ensures the dna is created safely and ethically
* the computer can create samll sections of overlapping single strands of nucleotides that make uo the gene called oligonucleotides
* oligonucleotides can be joined up create dna for an entire gene
* pcr can be used to quantyify dna
*
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what are the ways to clone and amplify a sample
in vivo- using vector or in vitro using pct
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modification of dna fragment in vivo
promoter region must be added at start of dna fragment. this is a sequence of dna which is the binding side for rna polymerase to enable transcribtio to occur
and terminator region must be added- at the end of the gene. it causes rna polymerase to dettach and stop transcribtion so only 1 gene at a time is copied
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whats a vector
something that carries the isolated dna into the host cell. most common vector is a plasmid. plasmid is a seperate bit of dna in a bacteria which only contains a few genes
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to insert dna into vector
youd use the same restriction enzymes u used to cut the dna fragments to cut the plasmid open.
this creates the same sticky ends.
therefore the dna fragments sticky ends are complementary to the sticky ends on the plasmid
enzyme ligase sticks the dna fragment to the cut plasmid (anneals them)
ligase catalyses a condensation reaction and phosphodiester bonds form between nucleotides
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the transformation of the vector
the vector (the plasmid and recombinant dna ) next need to be inserted into the host cells where the gene will be expressed and the protein created
to do this the cell membrane of the host cell must be more permeable
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how do u increase the permeability of the cell membrane of the host cell
host cells are mixed with Ca2+ and heat shocked
this enables the vector to enter hosts cell cytoplasm
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not all the host cells will succesfully take up the recominant plasmid
what are the three issues that could occur
1. the recombinant plamid doesnt get inside the host cell
2. the plasmid rejoins before the dna fragments enetered
3. the dna frgament sticks to itself rather than inserting itself in the plasmid
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what can be used to indentify which bacteria have taken up the recombinant plasmid
marker genes
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what are the three types of marker genes
Antibiotic resistance genes
genes containig fluorescent proteins
genes coding for enzymes
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calorimetry
used to estimate a plants biomass
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pcr equipment
thermocycler- the machine
the dna fragments that need to be amplified
dna nucleotides
dna polymerase TAQ polymerase
primers
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pcr method
1. increase temperature to 95 degrees in order for thr hydrogen bonds between complementary bases to break. splits dna to two strands
2. temperature is then decreased to 55 degrees so primers can attach
3. temp then increased to 72. dna polymerase rejoins complementary dna nucleotides to template strands. thats the opt temp for taq
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advantages of pcr
doesnt require living organisms- faster technique
quicker- 100 billion copies of dna can be made in two hoirs
automated
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what are dna probes
short single stranded pieces of DNA that are labelled radioactively or fluorecently in order to be indentified
| this is used to locate alleles on a gene and to screen patients for
## Footnote
heritable conditions
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whats dna hybridisation
when dna is heated to seperate the double strands into single strands and then probes are mixed with the dna. lowered temperature to allow them to anneal
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VNTRS
95% of human dna is made from introns which consist of many variable number tandem repeats VNTRS
the propability of two individuals having the same vntrs is very low however the more closely related you are the more similar theyre.
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genetic fingerprinting is
the analysis of vntrs in fingerprinting. can be used to determine genetic relattionships and variability within a pop
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WHATS THE LIGHT INDEPENDANT REACTION ALSO KNOWN AS
CALVIN CYCLE
