1
Q
Ecology
A
study of the inter-relationships between organisims and their environment. The environment includes both living and non-living factors
2
Q
Ecosystems
A
dynamic systems made up of a community and all non-living factors of its environment.
sizes can range
3
Q
Two main proccess to consider in ecosystems
A
- flow of energy through the system
- the cycling of elements within the system
4
Q
Population
A
a group of individuals of one species that occupy the same habitat at the same time potentially able to interbreed
5
Q
Size of a population can vary due to:
A
-the effect of abiotic factors
-the interactions between organisms e.g. intraspecific and interspecific competition and predation
6
Q
Community
A
all the populations of different species living and interacting in a particular place at the same time
7
Q
Habitat
A
a place where an organism normally lives characterised by physical conditions and other types of organisims present.
within habitats there are also smaller micro-habitats
8
Q
Ecological niche
A
describes how an organism fits into the environment- where the organism lives and what it does there- includes all the abiotic and biotic conditions needed for it to survive
9
Q
Abiotic factors that influence the size of a population
A
- temperature
-pH
-water and humidity
when any abiotic factor is below the optimum fo a population, fewer individual is able to survive because there adaptions are not suited to conditions. if no individuals have adaptions that allow survival, the population becomes extinct
10
Q
Nitrogen fixing bacteria
A
- free living nitrogen bacteria reduce nitrogen to ammonia this is used for the production of amino acids
- Mutualistic nitrogen fixing bacteria use carbohydrates from legumes to produce amino acids
-Lightning can also produce nitrogen fixing bacteria in the soil through the rain
11
Q
Nitrification
A
Free living chemosynthetic bacteria produce food by using energy from inorganic chemical reactions
oxidation of Ammonia to nitrate ions NO2
oxidation of NO2 to NO3
bacteria respire aerobically so farmers plough there fields to aerate there fields to create pockets of air
12
Q
Ammonification
A
Production of ammonia from organic nitrogen containing compounds (mannure, rotting plants)
saprobionts digest/hydrolyse protiens, DNA and nitrogen containing compounds using extra cellular digestive enzymes
13
Q
Denitrification
A
-occurs under anerobic conditions by denitrifying bacteria
-nitrates convertded to nitrogen gas
-soil conditions which encourage dentrification: flooding, clay soil, lack of ploughing
farmers should add grit to improve conditions
14
Q
Speciation
A
- Isolation/ gene pool are seperate
- Variety due to mutation
- Different selection pressures
- Selection of advantageous alleles
- Best suited survive and reproduce
- Change in allele frequency
- Eventually populations cannot reproduce successfully with each other
15
Q
Isolation types
A
Allopatric- by geography
Sympatric- by anything other than geography: behaviour, ecological, temporal, mechanical
16
Q
Directional selection:
A
- When 1 trait is selected for e.g. antibiotic resistance, pesticide resistance
- Occurs when there is a change in the situation
17
Q
Stabilising selection:
A
- When both extremes are selected against
- When conditions are stable e.g. birth weight in humans
18
Q
Disruptive selection:
A
- Individuals with intermediate phenotypes or alleles are selected against, whilst extremes are selected for e.g. Galapagos beak sizes
- Can cause polymorphism- continues existence of two or more distinct phenotypes in a species
19
Q
Mutations
Substitution of bases:
A
a nucleotide in a section of DNA is replaced by another nucleotide that has a different base. 3 outcomes: formation of a stop codon- final protein certainly going to be different (not perform normal function) as premature stop. Formation of a different amino acid so protein may now not be complementary so not function properly. Formation of a different codon but produces the same amino acid as before, genetic code is degenerate so most amino acids can code for more than one codon
20
Q
Mutations
- Deletion
A
a loss of a nucleotide base from a DNA sequence, it creates frame shifts to the left, as a result the gene is now read wrong and so the polypeptide will be wrong and so production of a non-functional protein – alter the phenotype
21
Q
Mutations
Addition of bases:
A
an extra base is inserted into the sequence- frame shift to the right- polypeptide produced will be different
22
Q
Mutations
- Duplication of bases
A
one or more bases are repeated. Produces a frame shift to the right
23
Q
Mutations
- Translocation of bases
A
group of bases becomes separated from the DNA sequence one chromosome and becomes inserted into the DNA sequence of a different chromosome. Has significant effects on gene expression leading to an abnormal phenotype- cancer & reduced fertility
24
Q
Consequences of mutations
A
- Formation of a different amino acid sequence
- Frame shift- different sequence of amino acids
- Formation of a stop codon- premature stop
- Silent mutation code is degenerate- different triplet codes can code for the same amino acid
25
Causes of mutation:
- Naturally occurring
- Mutagenic agents: high energy ionising radiation, chemicals
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Positives of mutations
- Genetic diversity required for natural selection & speciation
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Negative of mutations
- Harmful- produce an organism way less suited to its environment
- Occur in body cells rather than in gametes of normal cellular activities e.g. cell division
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Phototropism
1- Cells in the tip produce IAA (auxin), which is then transported down the shoot
2- The IAA initially is transported evenly throughout all regions as it begins to move down the shoot
3- Light causes the movement of IAA from the light side to the shaded side of the shoot
4- A greater concentration of IAA builds up on the shaded side than on the light side
5- As IAA causes elongation of the shoot cells and there is a greater concentration on of IAA on the shaded side of the shoot, the cells on this side elongate more
6- As the shade side elongates faster than the light side the shoot tip bends towards the light
29
Gravitropism
1- Cells in the tip of the root produce IAA, which is then transported along the root
2- IAA is initially transported to all sides of the root
3- Gravity influences the movement of IAA from the upper side to the lower side of the root
4- A greater concentration of IAA builds upon the lower side
5- As IAA inhibits the elongation of root cells and there is a greater concentration of IAA on the lower side, the cells on this side elongate less than those on the upper side
6- The relatively greater elongation of cells on the upper side compared to the lower side causes the root to bend downwards towards the force of gravity
30
Transcription
- Hydrogem bonds between DNA bases break
- One DNA strand acts as a template
- Free RNA nucleotides align by complementary base paring
- In RNA uracil base pairs to adenine on DNA
- RNA polymerase joins adjacent RNA nucleotides by phosphodiester bonds between adjacent nucleotides
- Pre-mRNA is spliced to form mRNA- introns are removed
31
Translation
- mRNA attaches to ribosomes
- tRNA anticcodons bind to complementary mRNA codons
- tRNA brings a specific amino acid
- Amino acids join by peptide bonds with the use of ATP
- tRNA release after amino acid joined to polypeptide
- The ribosomes moves along the mRNA to form the polypeptide
32
Glycolysis
- glucose is phosphorylated into phosphate glucose- 2 ATP are hydrolysed
- phosphate glucose then is split into 2 triose phosphate
- triose phosphate is then oxidised and hydrogen is removed and then captured by NAD which is then reduced
- ATP is then regenerated ADP + PI -- ATP +water pyruvate is produced- condensation reaction
33
links reaction
- Pyruvacte is oxidised hydrogen is removed, NAD is reduced
- CO2 removed
- Coenzyme A is added to acetyl to make acetylcoenzyme A- condensation reaction
34
Krebs Cycle
- Acetylcoenzyme A combines with a 4 carbonate molecule to make a 6 carbon molecule
- 6 carbon looses 2 CO2 picked up by NAD and FAD theses become reduced
- Single ATP molecule produced- cycle continues
6 cycles to produce one glucose
35
Electron transport chain
- Redcuced NAD and FAD pass electrons to first electron carrier- oxidation reaction
- Electrons pass through carries with a series of oxidation and reduction reactions- releasing ATP
- This energy used to actively transport protons from hydrogen across inner membrane- due to concentration gradient hydrogen protons by facilitated diffuses move back across via the ATP synthase channel releasing energy as ADP + PI-- ATP
- End of the chain electrons combine with protons and oxygen to produce water. oxygen is the final electron acceptor
36
Anaerobic respiration in animals
- Only glycolysis occurs
- Pyruvate is converted into latic acid (waste) by reducing pyruvate and oxidised NAD
- Oxidation of NAD allows for glycolysis to continue
37
Reflex arc
- Stimulus detected by receptor
- Impulse sent along sensory neurone
- Then to relay neurone- motor neurone
- To the effector- which stimulates a response
- Response is rapid, short lived, localised, involuntary- brain is not involved
38
Synaptic Transmission
- Action potential arrives depolarising presynaptic membrane
- Calcium ion channel proteins open, calcium ions move in by facilitated diffusion
- Pre-synaptic vesicles fuse with membrane
- ACh released and diffuses across the synaptic cleft
- ACh binds to receptor protein- these open- sodium ions diffuse through
- Post-synaptic membrane depolarised- action potential generated - if threshold is reached
- ACh broken down into acetate + choline by acetycholinesterase
- Choline is recycled into ACh- using energy from mitochondria
39
The eye- cones
- detect colour
- fewer no. rod cells
- fewer at periphery, conc at fovea
- good visual activity
- not sensitive to low-intensity light
- 3 types each responding to differetn wavelengths of lights
40
The eye- Rods
- detect shape
- greater no. than cone cells
- distribution more at periphery of retina, absent at fovea
- give poor visual accuracy
- sensitive to low-intensity light
- one type only
41
Nerous System
- Pass electrical impulses along their length
- stimulate target cells by secreting neurotransmitters
- short lived- local regions of the body- rapid
e.g. moving hand away from unpleasant stimuli
42
Hormonal system
- Produces chemicals- transported in blood system to target cell- has specific receptors- only target response
- slower less specific form of communication
- long lasting, widespread, slow
e.g. control of blood glucose concentration
43
Sensory neurone
- transmits nerve impulses from a receptor to an intermediate or motor neurone
- one dendron- very long
- impulse towards cell body- axon away
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Motor neurone
- nerve impulses transmitted from intermediate/ relay to an effector- gland/ muscle
- long axon, many short dandrites
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Relay neurone
-transmits impulses between neurones
e.g. sensory to motor
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Axon
- long fibre carrying nerve impulses away from cell body
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Myelin Sheath
lipid, membrane of schwann cells
48
Node of Ranvier
2-3 um long
constrictions between adjacent schwann cells no mylein sheath
49
Schwann
surround axon
provide electrical insulation
carry out phagocytosis
build up a layer of membrane around axon
50
Dendrons
extention of cell body, divide into smaller branches- dendrites
51
Dendrites
carry nerve impulses towards cell body
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Cell body
all usual cell organelles- nucleus, rough ER
- production of proteins + neurotransmitters
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Types of receptors e.g.
mechanoreceptor- physical
proprioreceptor- position/ movement
thermoreceptor- temperature
54
Pacinian Corpus
- mechanoreceptors
- respond to pressure or any mechanical stimulus that causes ddeformation of the receptor
- consists of a singular sensory nerve
- stretch mediated sodium ion channels, within the non-mylelinated terminal of sensory nerve fibre, opens in response to an applied pressure
the influx of sodium ions- change in potential- magnitude of generator potential is graded varies with the stimulus intesnsity
55
Resting potential in a neurone
-65/-70 mV
the inside of the cell is negative compared to the outside
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Resting phase in an nerve impusle
sodium potassium is always open and so uses active transport to move 3 Na+ out of the neurone for every 2 K+ ions in
the open potassium ion channel uses facilitated diffusion down a concentration gradient
57
Depolarisation- nerve impulse
stimulus excites the neurone cell membrane
this causes the gated sodium ion channels to open
the membrane becomes more permeable to sodium so there will be an influx of Na+ ions
this results in Na+ entering the neurone- which influences more Na+ gates to open
+- feedback loop
58
Repolarisation- nerve impulse
-potential difference at around 40+ sodium ion channels close, potassium ion channels open
membrane is more permeable to potassium so potassium ions diffuse out of the neurone down the pottassium ion conc gradient
the aim is to try and get the neurone bacak to resting potentioal
59
Hyperpolarisation- nerve impulse
- pottassium ion channels are slow to close so there is a slight 'overshoot' where too many potassium ions diffuse out of the neurone
- the potential difference becomes more negative than the resting potential <-70 mv
60
Refactory period
ensures the impulse is sent in one direction
61
Light dependent reactions
- chlorophyll undergoes photoionisation
- electrons picked up by electron carrier protien
- by a series of oxidation/reduction reactions energy is released and used to make ATP
- photolysis of water occurs producing oxygen, electrons and protons (hydrogen ions)
- oxygen is released
- electrons replace the electrons lost during photoionisation of chlorophyll
- protons picked up by NADP which also picks up the electrons from the last electron carrier and becomes reduced NADP
62
Do green plants absorb green light?
no
63
Light independent reaction- calvin cycle
- carbon dioxide reacts with 5-carobon compound ribulose bisphosphate (RuBP) this reaction is catalysed by the enzyme rubisco
- the reaction produces a 6 carbon intermediate compound
- this compound then produces 2 molecules of 3 carbon glycerate 3 phosphate know as GP
- reduced NADP from the light dependent reaction is used to then reduce GP to triose phosphate using energy supplied by ATP
- NADP is then reformed and goes back to the light-dependent reaction to be reduced again by accepting more protons
- the cycle then continues
1 cycle produces 1 carbon, 6 cycles for 1 glucose
64
where does the light independent reaction take place?
stroma of the chloroplasts
65
Autotrophic
self-feeding- it is able to make its own organic molecules from simple molecules
66
Photoautotrophic
uses light energy
67
chemoautotrophic
uses energy from chemical reactions
68
Hetrotrophic
different feeding- unable to make own organic molecules so must get them from other organisms
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where does glycolysis occur?
cytoplasm
70
where does the link reaction occur?
mitochondria
71
wherer doed the krebs cycle occur?
matrix
72
where does oxidative phosphorylation occur? (electron transport chain)
cristae- stalked particles
73
oxidation?
loss of electrons
74
reducation?
gain of electrons/hydrogen
75
what is affected by temperature/pH
Respiration
76
why is oxygen so important in the electron transport chain?
- no final e- acceptor
- e- start to block carrier
- so less/ no movement so reduced NAD and FAD cannot be oxidised
- so stopped glycolysis, link reaction and krebs cycle
77
what is sugar used for in plants?
respiration and to make make biological molecules- biomass of the plants
78
how is biomass measured?
mass of carbon or dry mass of tissue / area
could calculate chemical energy store using a calorimetry
79
Response to stimuli: Kinesis
form of response in which an organism does not move towards or away from a stimulus. instead it changes the speed at which it moves and the rate at which it changes direction
e.g. woodlice
80
Response to stimuli: taxis
simple reponse whose direction is determined by the direction of the stimulus. motile organisims repond directly to environmental changes by moving its whole body either towards a favourable stimulus or away from an unfavourable one
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positive taxis
movement towards
82
negative taxis
movement away
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the brain: Cerebrum
largest portion- right +left
responsible for intelligence- cerebal cortex
corpus callosum joins them together
84
the brain: cerebellum
2nd largest part
where impulses give rise to movement + coordination- balance, posture
85
the brain: medulla
pathway between brain + spinal cord
controls vomitting, coughing, sneezing, heart beat rate, breathing, blood pressure
every organism has one
86
the heart: key facts
made up of cardiac muscle
this is myogenic so no pulse is required
87
Muscle Contraction
- Nerve impulse generated in muscle
- Calcium released and combines with tropomyosin
- Tropomyosin moves out of the way of the binding site
- Myosin heads fit into binding sites
- Myosin heads then change angle moving actin forward – power stroke
- ATP attached to myosin
- Myosin head released from binding site
- Hydrolysis of ATP to ADP +PI with ATPase
- Energy released is used to recoil myosin head
- To relax the muscle, stop the nerve impulse, calcium are reabsorbed back into the endoplasmic reticulum
- Tropomyosin moves back over the binding site an blocks them again
88
Factors affecting speed at which an action potential travels are:
- myelin sheath
- diameter
- temperature
89
Factors affecting speed at which an action potential travels are: mylein sheath
electrical insulator- preventing action potential forming in part of the axon
instead action potential jumps from one node of ranvier to another
90
Factors affecting speed at which an action potential travels are: Diameter
greater the diameter faster the speed of conductance- less leakage of ions
91
Factors affecting speed at which an action potential travels are: temperature
higher temperature = faster nerve impulse
92
Summation
effect of neurotransmitters released from many neurones added together. Makes it more likely that the post- synaptic membrane will be excited and generate an action potential
93
Spatial summation
two or more presynaptic neurones release there neurotransmitters at the same post-synaptic neurone. need enough to exceed the threshold value. so they can trigger a new action potential
if neurones release an inhibitory neurotransmitter that is not complementary to receptor total effect may be no action potential
94
Acetylcholine
neurotransmitter used by the spinal cord neurone to control muscles
95
Dopamine
produces feelings of pleasure- reward system. usually inhibitory
96
GABA
major inhibitory neurotransmitter in the brain. opens cl- gated channels on post synaptic membrane
97
how do drugs effect neurotransmitters?
-increase number of impulses- improve acction e.g. mucsle contraction
block reuptake of neurotransmitters
release neurotransmitters from vesicles
98
Control of heartbeat
- SAN releases wave of electrical activity
- so atria contract at the same speed as the SAN impulse
-AVN relays electrical activity after a short delay- allowing the blood to flow to the bottom of the heart
- via purkyne tissue and bundle of His
- so ventricles contract from apex upwards
