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Biology Unit 4 > Biology Unit 4 Model Answers > Flashcards

Biology Unit 4 Model Answers Flashcards

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0
Q

D- Test cross

A

Testing a suspected heterozygote by crossing it with a known homologous recessive

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1
Q

M- What is reproductive isolation

A

when gametes are incompatible - different number of chromosomes so fusion cannot occur

When members of the species no longer recognise each other - different characteristics

When courtship behaviour is different

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2
Q

M- Mark release recapture estimate of population size

A

Capture large sample of organisms
Mark with non toxic paint/ not too obvious to predators/ wont wash up
Count and release
Allow time to disperse throughout population
Recapture large sample
Count total and how many are marked
Population = N1 x N2/ NM in 1st

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3
Q

M- Explain how carbon dioxide is produced during aerobic respiration

A

One CO2 is released during the link reaction when pyruvate 3C is converted t acetyl coA 2C
2 molecules of CO2 are released during the Kreb’s cycle when the 6C compound is decarboxylated to regenerate the 4C compound

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4
Q

M- Synthesis of ATP during the electron transport chain (oxidative phosphorylation

A

Takes place on the inner mitochondrial membrane/cristae
Reduced NAD and FAD are oxidised
Electrons passed from one carrier to another in an electron transport chain ETC
As electrons pass down the chain, they lose energy which is dissipated as heat
Hydrogen ions are pumped into the intermembrane space
Hydrogen ions diffuse back into the matrix down an electrochemical gradient
Via ATP synthase
ATP is made from ADP and Pi
Electrons at the end of the transport chain bind with H+ ion and are accepted by oxygen, the final acceptor, to make water

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5
Q

M- When you are asked to comment on a demographic transition graph what must you refer to?

A

life expectancy

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6
Q

M- How do you decide the number of quadrats to use in order to collect representative data?

A

Large number of quadrats so results are more reliable with repeats

Enough to be able to carry out a statistical test - SR requires a minimum of 7 pairs

Not too many for the available time

Calculate a running mean which changes little when there are enough quadrats.

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7
Q

M- Impact of inefficiency of energy transfer

A

Most food chains only have 4-5 trophic levels because insufficient energy is available to support a large breeding population at the top level
Biomass is less at higher trophic levels
Total amount of energy stored in each level is less at higher trophic levels

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8
Q

M - Factors affecting death rate

A

Age profile/ life expectancy at birth/ food supply/ effective sanitation/ medical care/ natural disasters/ war

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9
Q

M- what are the limitations of collecting plant data as percentage cover?

A

They may overhang where the leaves of larger plants are outside the quadrat
Smaller plants may be difficult to count where overshadowed by larger plants

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9
Q

M- Population pyramids

A

Stable population- birth rate and death rate in balance; no increase or decrease in population size
Increasing population- high birth rate; gives a wider base to the pyramid; fewer older people ; so narrower apex
Decreasig popualtion - lower birth rate; narrower base; more older people; woder apex

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11
Q

M- Pattern of population growth curves

A

Period of slow growth as small numbers reproduce slowly - lag phase

Period of rapid growth - expontential/log phase - population doubles per unit of time

Period where population growth remains stable with cyclic fluctuations

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12
Q

M - effect of predator - prey relationship on population size

A

Predators eat prey and reduce the prey poplation
Predators now in greater competition for food
Predators population is reduced as some individuals cannot compete
Fewer prey are eaten
Prey population increases
More prey for food so predator population increases

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13
Q

M- Adaptations of the leaf

A

Large surface area to absorb light
Arrangement of leaves that avoids shadowing
Thin so short diffusion pathway
Transparent cuticle and epidermis to allow light through to mesophyll
Lots of chloroplasts in upper mesophyll cells
Numerous stomata for gas exchange
Air spaces in lower mesophyll for rapid diffusion
Network of xylem and phloem

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14
Q

M- Describe how carbon in carbon dioxide becomes carbon in triose phosphate

A

Carbon dioxide combines with RuBP to make 2x G3P. This is reduced to TP which requires NADPH to provide the hydrogen for reduction and energy from the breakdown of ATP

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15
Q

M- Information required to calculate growth of a population

A

Birth and deaths

Number of emigrants and immigrants

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16
Q

M- Flow of energy through an ecosystem

A

Light energy converted to chemical energy during photosynthesis
Organic molecules converted to ATP during respiration
ATP used by cells to perform useful work

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18
Q

M- Roles of ATP

A

Energy released in smaller manageable quantities

Hydrolysis of ATP to ADP in a single step reaction so releases immediate energy

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19
Q

M- How NADP is reduced

A

NADP accepts a hydrogen and electron from ohtlysis/breakdown of water using light energy

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20
Q

M- Adaptations of chloroplast to the light independent reaction

A

Fluid of stroma contains enzymes needed to carry out reduction carbon dioxde
Stroma fluid allows easy diffusion of products of light dependent reaction into the stroma
Contains DNA and ribosomes to make proteins quickly

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21
Q

M- Describe how the light dependent reactions produce ATP and reduced NADP

A

Chlorophyll absorbs light energy
Electrons in chlorophyll are excited/energised by light energy/photons
This increases the energy levels in the electrons
Electrons move to an electron acceptor
Electrons lose energy as they are passed from one electron carrier to the next along the electron transfer/transport chain (ETC)
As electrons are passes along the ETC, ATP is formed from ADP and Pi using energy from electrons (photophosphorylation)
NADPH is formed when the electrons from the electron transfer chain and H+ from photolysis combine with NADP
NADP + H+ –> NADPH
The H+ and electron come from photolysis - to reduce NADP to NADPH
O2 is given off and the electrons replace those lost from chlorophyll
Photolysis - the break down of water using light energy
H2) –> @H+ + 1/2O2 + 2e-

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21
Q

M-Decarboxylation in respiration

A

Pyruvate - a 3 carbon compound - loses a carbon atom with co enzyme A, to produce a 2 carbon compound of acetyl coenzyme A
During this conversion decarboxylation occurs and CO2 is released
Acetyl co enzymes A then enters the Krebs cycle and combines with a 4C compound to produce a 6 carbon compound
The 6 C compound is then converted to a 5C compound and decarboxylation occurs
This 5C compound is then converted to a 4C compound and decarboxylation occurs again releasing CO2. NAD and FAD are reduced to give NADH and FADH2

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22
Q

M- Adaptations of the chloroplast to the light dependent reaction

A

Thylakoid membrane provide a large surface area for the attachment of chlorophyll, enzymes and electron carriers
Network of proteins hold chlorophyll in a position to absorb maximum amount of light
Granal membranes have enzymes that help makes ATP
Chloroplasts have their own DNA and ribosomes to make proteins quickly

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23
Q

M- Describe the part played by the inner mitochondrion in producing ATP

A

Cristae contain electron transport proteins that transfer electrons from the carriers NADH and FADH
H+ ions from the carriers are pumped into the intermembrane space using energy lost by electrons
H+ ions move back into the matrix along a concentration gradient by ATPase
Energy from the H+ ion gradient is used to combine ADP and Pi to make ATP

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25
Q

M- How does an increase in carbon dioxide levels in the atmosphere affect yield of grain?

A

Causes an increase in rate of photosynthesis therefore increases the amount of glucose made which increases growth rate - due to an increases rate of respiration and there ATP prodction- and yield
Increase in carbon dioxide levels usually causes an increase in climate temperature which would cause faster reaction rate hence higher yield

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26
Q

M- Significance of Krebs cycle

A

breaks down macromolecules into smaller ones
Produces hydrogen atoms that are carried by NAD to the ETC for oxidative phosphorylation (and the subsequent production of ATP)
Regenerates the 4C compound which would otherwise accumulate
Source of intermediate compounds used in the manufacture of other substances

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27
Q

M- How does the concentration of carbon dioxide in a forest change over time?

A

Low carbon dioxide during the day
As plants are photosynthesising and taking in carbon dioxide
Plants respire all the time but do not photosynthesise at night so carbon dioxide concentrations increase at night
Carbon dioxide levels are increased at the forest floor
Because ground level has less photosynthesising tissue, less light and more respiring animals

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28
Q

M- Glycolysis

A

Glucose is activated - phosphorylated - by the addition of inorganic phosphate
Produced by the breakdown of ATP into ADP and Pi
Glucose splits into 2 molecules of triose phosphate
NAD co enzyme accepts hydrogen from triose phosphate
and becomes reduced
Inorganic phosphorus is removed from triose phosphate to make pyruvate
4 molecules of ATP are produced by substrate level phosphorylation to give a net gain of 2 ATP per glucose molecule

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29
Q

M- Effective pesticides should be…

A

Specific
Biodegradeable
cost effective
will not accumulate in the food chain

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30
Q

M- Link reaction

A

Pyruvate is oxidised to the 2C compound acetyl coA
CO2 is released
NAD accepts hydrogen from pyruvate and so is reduced

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32
Q

M- Krebs cylce

A

2C acetyl coA combines with 4C compound
6C compound loses CO2
5C compound loses CO2
One molecule of ATP is produced by substrate level phosphorylation
FAD and NAD accept hydrogen and electrons
And becomes reduced (FADH and NADH)
4C compound combines with another 2C compound and the cycle begins again

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33
Q

M- Why is it important that samples are collected at random?

A

To avoid bias

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34
Q

M- The true rate of photosynthesis is greater than simply the plants uptake of carbon dioxide, why?

A

Some of the carbon dioxide produced in respiration is used in photosynthesis

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35
Q

M- Light independent reaction

A

Carbon dioxide joins with ribulose bisphosphate (RuBP) a 5 carbon compound- this gives an unstable 6 carbon compound

This quickly breaks down to 2 molecules of a 3 carbon compound glycerate 3-phosphate (GP)

This reaction is catalysed by the enzymes ribulose bisphosphate carboxylase (Rubisco)

ATP from the light dependent reaction is used to provide energy for the reduction of GP into TP - triose phosphate

The reduction reaction needs H+/reducing power

H+ are provided by reduced NADP (NADPH)from the light dependent stage

Two TP join up to form hexose which can combine to form starch and cellulose, 1 in every 6 TP molecules is used to make hexose

TP regenerates RuBP and so the cycle continues, 5 in every 6 TP molecules form RUBP

TP also forms amino acids, fatty acids, glycerol, DNA, RNA, glucose and starch.

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36
Q

M- Fermentation in yeast

A

C6H12O6 –> 2CH3CH2OH + CO2 ( glucose –> ethanol and carbon dioxide)
Anaerobic conditions
Optimum temperatures/pH
Only glycolysis can take place
Glucose –> pyruvate (NAD –>NADH)
Pyruvate –> Ethanol + CO2 (NADH –> NAD)
Nad is recycled/regenerated

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37
Q

M- What happens to pyruvate in anaerobic conditions and why this type of respiration is advantageous to skeletal muscle

A

Pyruvate takes up hydrogen ions from the reduced NAD
To produce lactate and NAD
This ensures that glucose can still be respired
Even in the absence of oxygen

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38
Q

M- Name inorganic nitrogen containing compounds

A

Nitrates
Nitrites
Ammonium

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39
Q

M- Advantages of mitochondria having more cristae

A

Larger surface area to carry out oxidative phosphorylation producing more ATP

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40
Q

M- Role of coenzymes and carrier proteins in synthesis of ATP

A

NAD accepts hydrogen during glycolysis, link reaction and Kreb’s cycle
NAD is reduced
NADH releases hydrogen ions during the electron transport chain, which are pumped across the mitochondrial membrane
Electrons released from the co enzymes are passed along a series of carrier proteins in the membrane
Energy lost from the electrons is used to make ATP from ADP and Pi

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42
Q

M- Why does a reduction in temperature decrease the amount of carbon dioxide in respiration?

A

Enzymes catalyse respiration reactions
Rate of reaction decreases as particles have less kinetic energy
So fewer collisions between enzyme active site and substrate
So fewer ES complexes can form

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43
Q

M- Explain why an increase in temperature leads to a decrease in the rate of respiration

A

Respiration is catalysed by enzymes which are proteins
Hydrogen bonds in the tertiary structure break
Active site is denatured
Substrate can no longer bind to the active site so fewer ES complexes can form

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44
Q

M- Nitrogen cycle

A

Plants take up nitrate ions (NO3^-) from the soil
The nitrates then form amino acids which are used to synthesise proteins which are organic nitrogen containing compounds in plants and animals
The plants are eaten by animals and the proteins are digested
Both plants and animals die, leaving a collection of dead materials (detritus) which contains nitrogen containing compounds
Decomposers decay the excretory products and detritus, releasing ammonia (NH3) and ammonium ions (NH4^+) into the soil
Nitrifying bacteria oxidise the ammonia into nitrites (NO2^-)
Then the nitrites are oxidised into nitrates which are taken up by the plants
Lightning and nitrogen fixing bacteria in the soil and in nodules on the roots of legumes fix nitrogen gas (N2) into ammonia (NH3) which is dissolved into ammonium
Denitrifying bacteria reduce nitrate to nitrogen, in anaerobic soil conditions that escape from the soil and returns to the atmosphere

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45
Q

M- Why does anaerobic respiration produce more carbon dioxide than aerobic respiration

A

Anaerobic respiration produces less ATP so more glucose is respires to generate the same amount of ATP

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46
Q

M- What happens when the rate of respiration is greater than the rate of photosynthesis?

A

The plant will be using more glucose than it is producing. Therefore the plant will not grow as quickly because there is less ATP produced for reactions such as DNA replication and protein synthesis - this will have an impact of total plant biomass and therefore lower yield

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48
Q

M- Why a low percentage of energy is transferred along the food chain

A

Some of the organism is not eaten
Some parts are not digested
Some energy is lost in excretory material e.g. urine
energy is lost as heat from the organisms
Energy is lost in repsiration

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49
Q

D- Abiotic

A

The non-living part of the environment

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50
Q

M- why intensive rearing increases energy conversion rate

A

Movement is restricted therefore less energy used in muscle contraction
Warm environment to reduce heat loss from the body
No wastage in feeding as animals receive optimum amount
Predators are excluded

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51
Q

M- Limitations of using pyramids of numbers

A

No account is taken of size of the organism

Number of individuals may be so great as to not be able to represent them accurately

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52
Q

M- Why organisms need energy

A

Metabolism
Movement - energy for muscle contractions
Active transport - change shape of carrier proteins
Cell division
Production of enzymes or hormones - energy needed to form lysosomes for secretion
Maintenance of internal body temperatures

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53
Q

M- Describe how and explain why the efficiency of energy transfer is different at different stages in the transfer

A

Some light is reflected off the plant or is the wrong wavelength to be absorbed by chlorophyll
Efficiency of photosynthesis is low - less than 2%
energy lost during respiration/excretion or some parts of the plants/animal are not eaten
Heat loss
efficiency f transfer increases with increasing trophic level (along food chain) so efficiency of consumers is greater than efficiency of producers
Efficiency is lower in older animals, primary consumers, warm blooded animals (endotherms)
Carnivores use more of their food than herbivores

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54
Q

M- Deforestation

A

Loss of trees means less photosynthesis
Therefore less CO2 removed from atmosphere
Unwanted trees often burned releasing CO2 into the atmosphere
The concentration of CO2 in the atmosphere increases leading to increased global warming
Reduced input to nitrogen cycle as less recycling of nitrate ions occurs
Increases loss of nitrates by leaching
roots of trees hold fertile part of soil= topsoil together. With no trees, wind erosion occurs causing removal of topsoil
Soil loses fertility so can only support lower numbers and fewer species of plants, giving lower biodiversity

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55
Q

D- Abundance

A

The number of individuals of a species in a given place

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56
Q

M- Factors that affect net productivity

A

The efficiency of the crop

The area of ground covered by the leaves of the crop

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57
Q

M- Disadvantages of chemical psticides

A

always have some effect on non target species
must be re applied therefore expensive
pests may develop resistance

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58
Q

D- Percentage Cover

A

An estimate of the area within a quadrat that a particular plant species covers

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59
Q

M- Comparison of natural and agricultural ecosystems

A

Natural - lower producivity; higher species diversity; more genetic diversity; nutrients recycled naturally; populations controlled by competition or climate; solar energy only; reaches a natural climax community

Artificial - higher productivity; lower species diversity; less genetic diversity within a species; nutrients cycling supplemented by use of fertilizers; population controlled by pesticides and cultivation; energy from food and fossil fuels as well as solar; prevented from reaching a natural climax community

61
Q

M- Why are animals that are more active less likely to survive in winter?

A

Activity increases rate of respiration which uses glucose and depletes food reserves
This is why some animals hibernate - they reduce their activity so reduce their rate of respiration so they do not use food stores

62
Q

M- Advantages of biological control

A

Specific
Control organisms reproduces itself and does not need to be reapplied
Pests do not become resistant

63
Q

M- What are the advantages of collective plant data as percentage cover?

A

Can be collected rapidly

No need to define individual plants

63
Q

M- Disadvantages of biological control

A

time lag as control does not act quickly

control organism itself may become a pest

64
Q

M- Explain how intensive rearing of domestic livestock increases net productivity

A

Slaughtered when young so more energy transferred to biomass
Fed on controlled diet so higher proportion of nutrients are absorbed
Movement restricted so less lost by respiration
Kept inside and heated so less energy lost as heat
Genetically selected for high productivity

65
Q

M- What are nutrient cycles?

A

Nutrient is taken up by producers as simple, inorganic molecules
Produces incorporates nutrient into complex organic molecules
Nutrient passes into consumers when producer is eaten
Nutrient passes along food chain
when producers and consumers die their complex molecules are broken down by saprobiotic microorganisms that release the nutrient in its organic simple form

66
Q

M- Reasons for increase in global levels of carbon dioxide

A

Combustion of fossil fuels releases carbon dioxide

Deforestation means there are less plants to tae in carbon dioxide during photosynthesis

67
Q

M- if the environment changes what would happens to the plants and animals?

A

They would need to adapt
Their niche would change
If plants couldn’t adapt its niche, the it would die our and become extinct
An animals may be forced to migrate

68
Q

M- reasons for the effect of halting succession on animal diversity

A

Prevents growth of woody plants
Decreases plant diversity
Less habitats and niches for animals
Lower variety of food sources

69
Q

M- How do microorganisms make carbon in starch available to plants?

A

These organisms are saprobiotic
Release (secrete) enzymes
Hydrolyse starch to glucose; products are absorbed by the microorganisms
Respire
Release carbon dioxide which is taken into leaves by stomata

70
Q

M- Consequences of global warming

A

Melting ice caps could cause extinction of some species
Rise in sea levels could flood low-lying land
Higher temperature and less rainfall could lead to the failure of crops
Intense storms would be prevalent in some areas leading to changes in wildlife distributon
Life cycles and populations of insects pests would alter and increase spread of tropical diseases towards the poles

71
Q

D- Population

A

A group of interbreeding organisms of one species in one particular habitat

72
Q

M- How reactions occurring in the mitochondrion generates ATP
NB no credit for glycolysis as this occurs in the cytoplasm

A

Pyruvate is actively pumped into the matrix
Pyruvate is decarboxylated to produce acetyl coA and CO2
NADH is also produced, as pyruvate loses hydrogen
Acetyl coA combines with 4C compound to produce 6C compound which is then decarboxylated
One molecule of ATP is produced by substrate level phosphorylation
NADH carries hydrogen and electrons to the crisae
Electrons are passed along the series of carrier proteins in the membrane
Electrons lose energy which is dissipated as heat
Hydrogen ions are pumped into the inter membrane space
Hydrogen ions diffuse back into the matrix down an electrochemical gradient
Via ATP synthase
Electrons at the end of the transport chain bind with H+ ion and are accepted by oxygen, the final acceptor, to make water

72
Q

M- Nitrogen fixation

A

Mutualistic bacteria in the root nodules of leguminous plants fix nitrogen to ammonium, the plant then uses this to create amino acids, proteins, DNA etc

73
Q

M- Why does denitrification not happen as much in sandy soils?

A

Sandy soil contain lots of oxygen

Denitrifying bacteria are anaerobic

75
Q

M - If niches overlap what does this mean?

A

Leads to interspecific competition

One may outcompete the other

76
Q

D- Frequency

A

The likelihood of a particular species occurring within a quadrat

77
Q

M- What do denitrifying bacteria use nitrate for?

A

respiration

77
Q

M- Name organic nitrogen compounds

A 
DNA
RNA
ATP
Protein
Amino acids
Urea
78
Q

M- Reasons for conservation

A

Ethical, economica, cultural, aesthetics

81
Q

M- Explain the advantages of using integrated pest control management

A

Biological agents - Only needs one application (reproduces); specific; maintains a low population; pests do not develop resistance; can use less chemicals (no bioaccumulation)

Chemical pesticides - acts quickly; can apply to a specific area; kill greater variety of pests

81
Q

M- Eutrophication

A

Leaching of fertilisers causes algae to grow exponentially at the surface of water
This absorbs light and prevents it penetrating to lower depths
Light is limiting factor for plant growth at lower depths and so aquatic plants die
Saprobiotic bacteria feed on dead plant mater
And use oxygen for respiration
Oxygen becomes limiting factor for aerobic organisms e.g. fish and so they die

82
Q

M- Features of pioneer species for successful colonization

A 
Produce lots of wind-dispersed seeds/spores
Rapid germination
Ability to photosynthesise 
Ability to fix nitrogen
Tolerance to extreme conditions
83
Q

Nitrogen fixation

A

Some are free living nitrogen fixing bacteria
They reduce N2 gas to NH3 which dissolves to form NH4+ ions

Some are Mutualistic ( symbiotic) nitrogen fixing bacteria
They are found in root nodules of leguminous plants, like peas and clover
This is mutualism because both species benefit from the relationship due to bacteria being protected and the plant being provided with nitrates
They reduce nitrogen gas into ammonia

Lightning also reduces nitrogen gas into ammonia

84
Q

M- Why most of the suns energy is not converted to organic matter

A

Not all wavelengths can be absorbed
Light may not fall on chlorophyll molelcule
Other factors may limit the rate
Most light is reflected back by clouds

84
Q

M- Sequences involved in succession

A

Pioneer species with appropriate adaptations colonise bare land and interact with the environment
Members of pioneer species die and are decomposed by bacteria and fungi
This adds humus to the soil which improves water holding capacity of the soil
Changes in the soil make environment less hostile
Larger plants replace smaller plants (competition)
new niches/habitats produced for new species to form new communities
Increases biodiversity
New communities will form and be replaced by later communities until a climax community is established. Biotic factors are more important than abiotic factors, biodiversity remains constant due to competitions making a stable climax community

85
Q

D- Food chain

A

A feeding relationship in which the producers are eaten by primary consumers which in turn are eaten by secondary consumers

86
Q

M- Correlation and cause

A

Correlation does not establish a cause

There may be another factor

87
Q

D- Loci

A

The position along the chromosome where genes occur

88
Q

M- Other means of increasing the energy conversion rate

A

Selective breeding so animals are more efficient at converting food into body mass
Using hormones to increase growth rates

93
Q

D- Producer

A

photosynthetic organisms that manufacture organic molecules using light enregy, water and carbon dioxide

94
Q

M- What does the Hardy Weinberg predict?

A

That the frequency of alleles will stay constant over time providing no mutations/selection etc

95
Q

D- Recessive allele

A

An allele that affects the phenotype of an organism only when the dominant allele is absent

96
Q

M- Conditions of the Hardy Weinberg equation

A 
No mutations
Population is isolated
No selection - all alleles are equally likely to be passed on
Large population
Mating within the population is random
98
Q

M- reproductive success and allele frequency (natural selection)

A

Variation within the original population
Random spontaneous mutation
Adaptation coded by mutated allele may give survival advantage/disadvantage
Survival to reproduce - differential reproductive success
Pass on alleles for favourable characteristics/adaptation to offspring
Allele frequency increases in population
Moe of the new variants in population

99
Q

M- What is the difference between accuracy and reliability?

A

Accuracy is being free from error, making no mistakes with instruments
Reliability means that there is little variation from the true value i.e. results are concordant when repeated

100
Q

D- Consumer

A

Organisms that obtain energy by feeding on other organisms

101
Q

M- Why is it important to check repeatability of measurements?

A

Identifies anomalies and increases reliability - differences likely to be due to personal error

102
Q

M- How could you use a scatter graph to check repeatability of measurements made by two observers?

A

Plot a scatter graph of X verses Y
Look for overlying points
i.e. points should lie close to the line of best fit in both cases

103
Q

M- Carbon cycle

A

Plants take in carbon dioxide
This is used for photosynthesis
Sugar/starch (carbon compounds) synthesised
Carbon compounds then passed along food chain when primary consumer eats producer, secondary consumer eats primary consumer etc
Organism dies
Decomposers, use extra cellular enzymes to digest and break down organism and use their carbon compounds in respiration
All the living organisms (plants, animals and the decomposers) give off CO2 from respiration and CO2 is returned into the atmosphere this way
Plants take in CO2 again for photosynthesis
Burning trees and fossil fuels releases CO2 also
Burning coal also releases sulphur dioxide (SO2)

103
Q

M- Explain why statistical tests are necessary.

A

Determines the probability of results being due to chance
Determines whether results is biologically significant
Enables null to be accepted or rejected

103
Q

D- Biotic

A

The living part of the environment

104
Q

M- Use the words probability and chance to explain the meaning of ‘differed significantly’ (p<0.05)

A

There is a probability of less than 0.05 (5%) that the difference was due to chance
OR
There is a probability of more than 0.95 (95%) that the difference was not due to chance i.e. was biological

105
Q

D- Ecosystem

A

A self contained unit made up of all the biotic and abiotic features in a specific area

106
Q

Denitrification

A

Reduces nitrates to nitrogen
In anaerobic soil conditions
Which escapes from the soil and returns to the atmosphere

107
Q

D- Predator

A

An organism that feeds on another organism

108
Q

M - Factors affecting birth rates

A

economic conditions/ cultural background/ social conditions/ birth control/ political factors

108
Q

D- Community

A

All the population of different organisms living and interacting in a particular place at the time

108
Q

D- Habitat

A

The place where a community of organisms lives

108
Q

D- Niche

A

How an organism fits into an environment referring to where it lives and what it does there

109
Q

D- Intraspecific

A

Within a particular species - when referring to competition

110
Q

D- Interspecific

A

Between 2 or more different species- when referring to competition

111
Q

M- Outcomes of succession

A 
Environment becomes less hostile
Greater number of variety of habitats
Increased biodiversity
More complex food webs
Increased biomass
112
Q

D- Secondary consumers

A

Organisms that obtain energy by feeding on primary consumers

113
Q

D- Primary consumer

A

Organisms that obtain energy by feeding on producers

114
Q

M- How increasing plant biodiversity causes increases animal biodiversity

A

Increases variety of food sources
Increase number of niches
Increased number of habitats

115
Q

D- Trophic levels

A

The position of an organism in a food chain

115
Q

D- Gross production

A

Total quantity of energy that the plants in a community convert to organic matter

116
Q

M- Describe how you could show whether there is a correlation between 2 variables

A

Plot a scatter graph and draw a line of best fit
OR
Conduct Spearmans Rank Correlation Test - look for figures close to +1 or -1

118
Q

D- Decomposers

A

Microorganisms e.g. bacteria and fungi, that break down complex organic molecules into simple components and release minerals and elements into the soil

118
Q

D- Detritivore

A

Small organisms e.g. woodlice and earthworms, that breakdown the complex organic molecules in dead and decaying plant and animal matter

120
Q

D- Allele

A

One alternative form of a gene occupying a specific position on a chromosome

121
Q

D- Biomass

A

Total mass of plants and/or animals in a particular place

122
Q

D- Dry biomass

A

Mass of plants and/or animals in a particular place minus their water content

123
Q

D- Gene

A

A section of DNA coding for the synthesis of a single polypeptide

124
Q

D- Prey

A

An organism that is consumed by another organism

125
Q

M- How geographical isolation leads to the formation of a new species

A

Individuals of one species can freely interbreed and have a single gene pool
Climate change over time causes a split in the area with different conditions - geographical isolation
Variation within the original population
Random spontaneous mutation
Adaptation coded by mutated allele may give survival advantage/disadvantage
Survival to reproduce - differential reproductive success
Pass on alleles for favourable characteristics/ adaptations to offspring
Allele frequency increases in population
more of the new variants in population
Type of alleles and their frequency in each area/each gene pool changes
And becomes so different that they become a separate species
If species are reunited, they will not be able to interbreed to produce fertile offspring- reproductive isolation

126
Q

D- Net production

A

Rate at which plants store energy

126
Q

D- Homologous

A

A diploid organism that has inherited the same allele for a single gene from both parents

127
Q

D- Genotype

A

The genetic constitution of an organism

127
Q

D- Heteroygous

A

A diploid organism that has inherited different alleles for the same gene from each parent

128
Q

D- Phenotype

A

The characteristics or appearance of an organism ( the way the gene is expressed)

128
Q

D- Dominant allele

A

An allele that affects the phenotype of an organism, whether present in the homologous or heterozygous condition

130
Q

D- Carrier

A

An individual with a recessive allele of a gene that does not affect their phenotype

131
Q

D- Co dominant alleles

A

Pairs of alleles that both affect the phenotype when present in a heterozygote

132
Q

M- Assumptions of mark release recapture techniques

A

proportion of marked to unmarked in the second sample if equal tot he proportion of marked to unmarked in the whole population

Marked individuals from the first sample distribute themselves evenly with enough time to do so

Population has a boundary so no emigration or immigration

Few births and deaths

Method of marking does not make it more liable to predation

Mark is not lost during the investigation

133
Q

M- Random sampling

A

Produce a grid and select coordinates using a random number generator by using a calculator. Place a quadrat at the intersection of each pair of coordinates and record the species within it. Record a mean and the scale up to the entire area.

133
Q

Ammonification

A

Saprobiotic microorganisms like fungi and bacteria, break down organic nitrogen and release ammonium ions into the soil

Fertilisers contain urea and ammonium phosphate.
Urea is converted into NH3 by enzymes in the soil and then converted into ammonium ions by bacteria

134
Q

humptydumpty sat on a wall, humptydumpty had a great fall, all the kings horses and all the kings men, couldn’t put humpty together again

A

hehe

135
Q

M - Abiotic factors

A

Effect of temperature - at low temperature, enzymes work slowly due to having less kinetic energy therefore less movement and less successful collisions between active site and substrate leading to decreased formation of ES complexes; at high temperatures enzymes are denatured - hydrogen bonds break, tertiary structure unfolds leading to less ES complexes forming

Light - rate of photosynthesis increases as light intensity increases; plants grow faster and produce more spores/seeds; animal population that feeds on producers can grow larger

pH - enzymes working in extremes of pH above and below the optimum can denature and tertiary structure unfolds leading to less ES complexes forming

Humidity - affects transpiration rate in plants and rate of evaporation in animals

136
Q

Where does light dependent reaction take place?

A

Thylakoid stacks in the grana

137
Q

Where does the light independent reaction take place?

A

Stroma

138
Q

Nitrification

A

Nitrifying bacteria- free living soil microorganisms
Oxidise ammonium to nitrites(NO2-)
The oxidises nitrites to nitrates
This is an exothermic reaction which means it releases energy

Biology Unit 4 (1 decks)

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