Download Unit 4: Chapter 1: Populations

Unit 4: Populations and the environment
Chapters:
1 – Populations
2 – ATP
3 – Photosynthesis
4 – Respiration
5 – Energy and ecosystems
6 – Nutrients cycles
7 – Ecological succession
8 – Inheritance and selection
Exam dates:
Friday 11th January 2013 – PM
Tuesday 11th June 2013 – AM
Length:
1 hour and 30 minutes
Total marks: 75
Percentage of A2: 16.7%
Unit introduction:
Living organisms form structured communities within dynamic but essentially stable
ecosystems through which energy is transferred and chemical elements are cycled. Humans
are part of the ecological balance and their activities affect it both directly and indirectly.
Consideration of these effects underpins the content of this unit and should lead to an
understanding that sustainability of resources depends on effective management of the conflict
between human needs and conservation.
Unit 4: Chapter 1: Populations
1.1 Populations and ecosystems:
Key words:
What is meant by the terms ‘environment’, ‘biotic’, ‘abiotic’ and ‘biosphere’?
What is an ecosystem?
What is meant by the terms ‘population’, ‘community’ and ‘habitat’?
What is a niche?
ecology, abiotic, biotic,
biosphere, ecosystem,
population, niche, community,
habitat, microhabitat
Explain what is meant by the term ecology:
Explain what is meant by the term community:
Explain what is meant by the term ecosystem:
Explain what is meant by the term habitat:
Explain what is meant by the term populations:
Explain what is meant by the term ecological niche:
Unit 4: Chapter 1: Populations
1.2 Investigating populations:
Key words:
What factors should be considered when using a quadrat?
How is a transect used to obtain quantitative data about changes in communities
along a line?
How is the abundance of different species measured?
How can the mark-release recapture method be used to measure the abundance
of mobile species?
habitat, abundance,
quadrat, sample,
random, transect,
frequency, percentage
cover, mark-releaserecapture, analysis
Explain the factors that should be considered when
using a quadrat:
Explain how you would measure abundance:
Explain what is meant by the term random sampling,
and how you would ensure that a sample is truly
random:
Explain what mark-release-recapture is and how it is
used to estimate population size:
Explain how you wold sample along a transect:
Explain how you would analyse the data:
Unit 4: Chapter 1: Populations
1.3 Variation in population size:
Key words:
What factors determine the size of a population?
Which abiotic factors affect the size of a population?
How does each of these factors affect population size?
population, population growth curve,
limiting factors, abiotic, biotic, pH,
temperature, light, water, humidity
Explain what factors affect the size of a given population:
Explain how the following factors affect
population size:
pH:
light:
Label and explain the stages of the population growth curve:
temperature:
water and humidity:
Unit 4: Chapter 1: Populations
1.4 Competition:
Key words:
What is intraspecific competition?
What factors do different species compete for?
What is interspecific competition?
How does interspecific competition influence population size?
competition, intraspecific,
intraspecific, population, niche,
Explain what intraspecific competition is:
Explain what interspecific completion is, in your
answer include information on the factors different
species complete for:
Explain how interspecific competition influences
population size:
Unit 4: Chapter 1: Populations
1.5 Predation:
Key words:
What is predation?
How does the predator-prey relationship affect the population size of the
predator and the prey?
predator, prey, predation,
population, ecosystem,
selection pressure
Explain what predation is:
Explain what is happening in this graph:
Explain the effect predator-prey
relationships have on population size:
Explain what is happening in this graph:
Unit 4: Chapter 1: Populations
1.6 Human populations:
Key words:
How does the human population growth curve differ from that of
most other organisms?
What factors affect the growth and size of human populations?
migration, emigration, immigration,
birth rate, death rate, survival, life
expectancy
Explain how the following factors that affect human population, and
how they are calculated:
Migration:
Use the graphs to help
you explain:
Stable population:
Birth rate:
Increasing population:
Death rate:
Decreasing population:
Unit 4: Chapter 1: Populations
Exam questions
Blue tits are small birds that live in woods. An ecologist
estimated the size of the blue tit population visiting gardens
near a wood in November.
• She trapped 28 blue tits. She marked all of these birds
with small metal rings on their legs.
• Two weeks later, she trapped another sample of blue tits.
Of these birds, 18 were marked and 20 were not marked.
Use the data to estimate the size of the blue tit population.
Show your working.
Size of population ....................................
(2 marks)
The diagram shows some features of blue tit behaviour at
different times of the year.
Using mark-release-recapture to estimate the size of a blue
tit population in June would not give reliable results. Explain
why.
(2 marks)
Using mark-release-recapture to estimate the size of a blue
tit population in March would not give reliable results.
Explain why.
(2 marks)
Whales spend most of their time deep in the sea but they
come to the surface to breathe. When they are at the
surface, scientists obtain small samples of their skin. The
scientists find the base sequence in some of the DNA from
these samples. The base sequence is different in each
whale. You could use the information about the base
sequence to estimate the size of the whale population by
using mark-release-recapture. Explain why.
(2 marks)
Unit 4: Chapter 1: Populations
Exam questions
Explain what is meant by the ecological term
population.
(1 mark)
Four factors may affect the size of a human
population. They are
• Birth rate (B)
• Death rate (D)
• Emigration rate (E)
• Immigration rate (I).
Use all the letters B, D, E and I to write a formula
showing
a population that stays the same size
The table shows some features relating to the
human population of Mexico in 2007.
In 1990 the life expectancy was 70 years. Suggest
one reason for the change in life expectancy since
1990.
(1 mark)
Use the information in the table to calculate the size
of the population of Mexico in 2008. Show your
working.
(1 mark)
a population that is increasing in size.
Answer .....................................................
(1 mark)
(2 marks)
Unit 4: Chapter 1: Populations
Exam questions
Parasites are organisms that live on or in host organisms. The
populations of many organisms may be reduced by the effects of
parasites.
Feather mites are small parasites found on the wing feathers of
many birds. The mites feed on the oil that the birds produce. This
oil keeps the feathers in good condition. Birds unable to oil their
feathers properly use more energy in maintaining their body
temperature. This results in less energy being available for other
processes.
Scientists investigated the relationship between the numbers of
feather mites and the breeding success of one species of bird, the
great tit.
Use the information above to suggest how feather mites could
affect breeding in great tits.
The scientists calculated the percentage of each pair’s eggs from
which chicks survived to leave the nest. They called this ‘breeding
success per pair’.
The table shows some of the data that the scientists obtained.
Do these data support the hypothesis that the presence of feather
mites reduces the ability of great tits to reproduce successfully?
Give reasons for your answer.
(2 marks)
The scientists located a large number of great tit nests. They
sampled these at random.
For each nest they recorded
• the total number of eggs laid
• the number of chicks that hatched from the eggs
• the number of chicks that survived to leave the nest
• the total number of feather mites on the two parent birds.
Explain why the scientists sampled the nests at random.
(2 marks)
(3 marks)
Unit 4: Chapter 1: Populations
Exam questions
The scientists calculated a correlation coefficient for these data.
State a null hypothesis that would be appropriate for this
investigation.
Describe the relationship between the number of feather mites
present on each great tit and the size of the oil gland.
(1 mark)
The correlation coefficient that they obtained had a negative value.
What does a negative value indicate about these data?
(1 mark)
The oil that a great tit puts on its feathers is made in an oil gland at
the base of the tail. The bird uses its beak to spread the oil over its
feathers. This is called preening. Preening takes place in early
morning and evening and empties the oil gland each time. After
preening, the oil gland is considerably smaller.
At the same time that the scientists recorded the number of feather
mites on each great tit, they also measured the size of the oil
gland. The graph shows their results and includes the scientist’s
line of best fit.
(2 marks)
Explain how measuring the oil gland at the same time as counting
the feather mites may have affected the reliability of the data.
(2 marks)
Feather mites eat pathogenic bacteria and fungi as well as oil.
Explain how this may affect the breeding success of the birds.
(2 marks)
Unit 4: Chapter 2: ATP
2.1 Energy and ATP:
Key words:
What is energy and why do organisms need it?
How does ATP store energy?
How is ATP synthesised?
What is the role of ATP in biological processes?
State what energy is:
Describe how ATP stores energy:
State why organisms
need energy:
Explain how ATP is synthesised:
Explain the role of ATP in biological
processes
Unit 4: Chapter 2: ATP
Exam questions
The table contains statements about three biological processes. Complete the table with a tick if the
statement in the first column is true, for each process.
(3 marks)
1 (b) Write a simple equation to show how ATP is synthesised from ADP.
(1 mark)
1 (c) Give two ways in which the properties of ATP make it a suitable source of energy in biological
processes.
1
2
(2 marks)
Unit 4: Chapter 3: Photosynthesis
3.1 Overview of photosynthesis:
Key words:
How is the plant leaf adapted to carry out photosynthesis?
What are the main stages of photosynthesis?
ATP, photosynthesis, cuticle, light-dependent
reaction, protons, electrons, NADP, grana,
thylakoids, lamellae, stroma, chloroplasts
Label the diagram to explain how a plant leaf is adapted to carry out photosynthesis and the main stages of
photosynthesis:
Unit 4: Chapter 3: Photosynthesis
3.2 The light-dependent reaction:
Key words:
What are oxidation and reduction?
How is ATP made during the light-dependent reaction?
What is the role of photolysis in the light-dependent reaction?
How are chloroplasts adapted to carry out the light-dependent reaction?
ATP, photolysis, oxidation,
reduction, electrons, chlorophyll,
thylakoids,
Describe oxidation and reduction:
Explain how ATP is
made:
Explain photolysis:
Describe how chloroplasts are adapted to carry out the light-dependent reaction:
Unit 4: Chapter 3: Photosynthesis
3.3 The light-independent reaction:
Key words:
How is carbon dioxide absorbed by plants incorporated into organic molecules?
What are the roles of ATP and reduced NADP in the light-independent reaction?
What is the Calvin cycle?
ATP, NADP, Calvin
cycle, stomata, stroma,
Explain the steps of the Calvin cycle:
Describe where the lightindependent reaction takes
place:
Explain the link between the Calvin
cycle and the light-dependent
reaction:
Describe the lollipop
experiment:
Unit 4: Chapter 3: Photosynthesis
3.4 Factors affecting photosynthesis:
Key words:
What is meant by the concept of limiting factors?
How can photosynthesis be measured?
How do temperature, carbon dioxide concentration and light intensity affect the rate
of photosynthesis?
light-intensity, carbon
dioxide, temperature,
limiting factor,
photosynthesis
Explain how light intensity can affect the rate of
photosynthesis:
Explain how carbon dioxide concentration can
affect the rate of photosynthesis:
Explain how temperature can affect the rate of
photosynthesis:
Explain the law of limiting factors:
Unit 4: Chapter 3: Photosynthesis
Exam questions
Scientists investigated the effects of temperature and light
intensity on the rate of photosynthesis in creeping azalea.
They investigated the effect of temperature on the net rate of
photosynthesis at three different light intensities. They also
investigated the effect of temperature on the rate of
respiration. The graph shows the results.
Use information from the graph to find the gross rate of
photosynthesis at 20°C and medium light intensity.
Answer .....................................................
(1 mark)
Creeping azalea is a plant which grows on mountains.
Scientists predict that in the area where this plant grows the
mean summer temperature is likely to rise from 20°C to
23°C. It is also likely to become much cloudier. Describe and
explain how these changes are likely to affect the growth of
creeping azalea.
Name the factors that limited the rate of photosynthesis
between X and Y.
(1 mark)
Use information from the graph to explain your answer.
(2 marks)
(3 marks)
Unit 4: Chapter 3: Photosynthesis
Exam questions
During photosynthesis, carbon dioxide reacts with ribulose
bisphosphate (RuBP) to form two molecules of glycerate 3phosphate (GP). This reaction is catalysed by the enzyme
Rubisco. Rubisco can also catalyse a reaction between
RuBP and oxygen to form one molecule of GP and one
molecule of phosphoglycolate. Both the reactions catalysed
by Rubisco are shown in Figure 1.
Where exactly in a cell is the enzyme Rubisco found?
(1 mark)
Use the information provided to give the number of carbon
atoms in one molecule of phosphoglycolate.
Use Figure 1 to explain the results obtained in Figure 2.
(2 marks)
Use the information provided and your knowledge of the
light-independent reaction to explain why the yield from soya
bean plants is decreased at higher concentrations of
oxygen. Phosphoglycolate is not used in the lightindependent reaction.
(1 mark)
Scientists investigated the effect of different concentrations of
oxygen on the rate of absorption of carbon dioxide by leaves
of soya bean plants. Their results are shown in Figure 2.
(3 marks)
Unit 4: Chapter 4: Respiration
4.1 Glycolysis:
Key words:
Where does glycolysis fit into the overall process of respiration?
What are the main stages of glycolysis?
What are the products of glycolysis?
hydrolysis; activation energy;
glycolysis
State where glycolysis fits in the overall process of
respiration:
Describe the stages of glycolysis:
1)
2)
3)
4)
State the products of glycolysis:
Unit 4: Chapter 4: Respiration
4.2 Link reactions and the Krebs cycle:
Key words:
What is the link reaction?
What happens during the Kerbs cycle?
What are hydrogen carrier molecules and what is their role in the
Krebs cycle?
oxidised; eukaryotic cells; glycolysis;
substrate-level phosphorylation;
Explain the link reaction:
Explain what happens in the
Krebs cycle:
Name the coenzymes and state why they are
important:
Explain the significance of the
Krebs cycle:
Unit 4: Chapter 4: Respiration
4.3 Electron transport chain:
Key words:
Where does the electron transport chain take place?
How is ATP synthesised in the electron transport chain?
What is the role of oxygen in aerobic respiration?
aerobic; electrons; adenosine
triphosphate; eukaryotic cells;
protons; oxidation-reduction
Describe the role of the mitochondria in respiration:
Explain how ATP is synthesised in the electron transport
chain:
Describe the role of oxygen in aerobic
respiration:
Unit 4: Chapter 4: Respiration
4.4 Anaerobic respiration:
Key words:
How is energy released by respiration in the absence of oxygen?
How is ethanol produced by anaerobic respiration?
How is lactate produced by anaerobic respiration?
glycolysis; Krebs cycle;
Explain how energy is released by anaerobic
respiration:
Describe the production of lactate in animals:
Describe the production of ethanol by plants and
microorganisms:
Compare the energy yields from aerobic and
anaerobic respiration:
Unit 4: Chapter 4: Respiration
Exam questions
The biochemical pathway of aerobic respiration
involves an number of different steps. Name one
step in which carbon dioxide is produced
When the apple slices were transferred to nitrogen,
the following biochemical pathway took place:
(1 mark)
In an investigation, scientists transferred slices of
apple from air to anaerobic conditions in pure
nitrogen gas. They measured the rate of carbon
dioxide production.
The scientists kept the temperature constant
throughout the investigation. Explain how a
decrease in temperature would affect the rate of
carbon dioxide production.
Use this pathway to explain the part played by
reduced NAD when the apple slices were
transferred to nitrogen
(2 marks)
(2 marks)
The rate of carbon dioxide production was higher
when the apple slices were in nitrogen than when
they were in the air. Explain why.
(3 marks)
Unit 4: Chapter 4: Respiration
Exam questions
A student measured the rate of aerobic respiration of
a woodlouse using the apparatus shown in the
diagram.
What measurements should the student have taken to
calculate the rate of aerobic respiration in mm3 of oxygen g–1
h–1?
The student closed the tap. After thirty minutes the
drop of coloured liquid had moved to the left. Explain
why the drop of coloured liquid moved to the left.
(3 marks)
DNP inhibits respiration by preventing a proton gradient
being maintained across membranes. When DNP was
added to isolated mitochondria the following changes were
observed
•
less ATP was produced
•
more heat was produced
•
the uptake of oxygen remained constant.
Explain how DNP caused these changes.
(3 marks)
(3 marks)
Unit 4: Chapter 4: Respiration
Exam questions
Yeast is a single-celled organism. A student investigated
respiration in a population of yeast growing in a sealed container.
His results are shown in the graph.
Use the information provided to explain the changes in production
of ethanol during this investigation.
(2 marks)
Sodium azide is a substance that inhibits the electron transport
chain in respiration. The student repeated the investigation but
added sodium azide after 4 hours. Suggest and explain how the
addition of sodium azide would affect oxygen uptake and the
production of ethanol.
Calculate the rate of oxygen uptake in arbitrary units per hour
between 2 and 4 hours.
Answer ...................................... arbitrary units per hour
(1 mark)
Use the information provided to explain the changes in oxygen
uptake during this investigation.
(3 marks)
(3 marks)
Unit 4: Chapter 5: Energy and ecosystems
5.1 Food chains and food webs:
Key words:
How does energy enter an ecosystem?
How is energy transferred between the organisms in the ecosystem?
What is meant by the terms ‘trophic level’, ‘food chain’, ‘food web’;
‘producer’, ‘consumer’ and ‘decomposer’?
How is energy lost from the ecosystem?
producers; consumers;
decomposers; trophic level;
food chain; food web;
habitat; detritivores
Explain the following terms:
Trophic level:
Describe how energy enters an ecosystem:
Food chain:
Food web:
Describe how energy is transferred between
organisms in an ecosystem:
Producer:
Consumer:
Describe how energy is lost from the ecosystem:
Decomposer:
Unit 4: Chapter 5: Energy and ecosystems
5.2 Energy transfer between trophic levels:
Key words:
What percentage of energy is transferred from one trophic level to the next?
How is energy lost along the food chain?
Why do most food chains have no more than five trophic levels?
How is the percentage efficiency of energy transfers calculated?
ecosystem; net production;
energy transfer; percentage
efficiency;
Using the diagram, explain:
What percentage of energy is transferred from one
trophic level to the next:
How energy is lost along the food chain:
Why most food chains have no more than five
trophic levels:
The efficiency of energy transfers is calculated using
the following equation:
𝑒𝑛𝑒𝑟𝑔𝑦 𝑡𝑟𝑎𝑛𝑠𝑓𝑒𝑟 =
𝑒𝑛𝑒𝑟𝑔𝑦 𝑎𝑣𝑎𝑙𝑖𝑎𝑏𝑙𝑒 𝑎𝑓𝑡𝑒𝑟 𝑡ℎ𝑒 𝑡𝑟𝑎𝑛𝑠𝑓𝑒𝑟
× 100
𝑒𝑛𝑒𝑟𝑔𝑦 𝑎𝑣𝑎𝑙𝑖𝑎𝑏𝑙𝑒 𝑏𝑒𝑓𝑜𝑟𝑒 𝑡ℎ𝑒 𝑡𝑟𝑎𝑛𝑠𝑓𝑒𝑟
Calculate the energy efficiency for this example:
Energy available after the transfer = 50kJm-2year-1
Energy available before the transfer = 250kJm-2year-1
Unit 4: Chapter 5: Energy and ecosystems
5.3 Ecological pyramids:
Key words:
What are the different types of ecological pyramid?
What are the relative merits and disadvantages of each?
pyramid of numbers; pyramid of energy;
pyramid of biomass
Explain what a pyramid of
numbers is:
Explain what a pyramid of
biomass is:
Explain what a pyramid of energy
is:
Explain the advantages of using a
pyramid of numbers:
Explain the advantages of using a
pyramid of biomass:
Explain the advantages of using a
pyramid of energy:
Explain the disadvantages of
using a pyramid of numbers:
Explain the disadvantages of
using a pyramid of biomass:
Explain the disadvantages of
using a pyramid of energy:
Unit 4: Chapter 5: Energy and ecosystems
5.4 Agricultural ecosystems:
Key words:
What is an agricultural ecosystem?
How do natural and agricultural ecosystems differ?
What is meant by productivity?
How is productivity calculated?
tropic level; gross productivity; net
productivity;
Describe what an agricultural ecosystem is:
Describe what is meant by productivity and give the
formula:
Explain how natural and agricultural ecosystems
differ:
Unit 4: Chapter 5: Energy and ecosystems
5.5 Chemical and biological control of agricultural pests:
Key words:
What are pests and pesticides?
What are the features of an effective pesticide?
How are biological agents used to control pests?
What is integrated pest management?
pests; pesticides; biodegrade; costeffective; accumulation; monoculture;
conservation;
Describe what pests and pesticides
are:
Explain what biological control is:
Explain what an integrated pest control system is:
State the features of an effective
pesticide
Explain how controlling pests effectively increases productivity:
Unit 4: Chapter 5: Energy and ecosystems
5.6 Intensive rearing of domestic livestock:
Key words:
How does rearing animals intensively increase the efficiency of
energy conservation?
selective breeding; habitats; populations;
antibiotic resistance; species diversity
Explain how rearing animals intensively increases the efficiency of energy conservation:
Unit 4: Chapter 5: Energy and ecosystems
Exam questions
Scientists constructed a mathematical model. They used this
model to estimate the transfer of energy through consumers in a
natural grassland ecosystem. The table shows their results.
The R : A ratio is higher in mammalian primary consumers than in
insect primary consumers. Suggest a reason for this higher value.
(1 mark)
The scientists tested their model by comparing the values it
predicted with actual measured values. The graph shows their
results.
Complete the equation to show how net production is calculated
from the energy in ingested food.
P=
(1 mark)
Describe and explain how intensive rearing of domestic livestock
would affect
the figure for A in the first row of the table
Evaluate the evidence in the graph.
(1 mark)
the figure for R in the first row of the table.
(1 mark)
Calculate the ratio of R : A for mammalian primary consumers.
(1 mark)
(3 marks)
Unit 4: Chapter 5: Energy and ecosystems
Exam questions
Residual food intake (RFI) is the difference between the amount of
food an animal actually eats and its expected food intake based on
its size and growth rate. Scientists have selectively bred cattle for
low RFI. Explain the advantage to farmers of having cattle with a
low RFI.
Bacteria in the digestive systems of cattle break down food and
produce methane. Scientists investigated the relationship
between RFI and methane production. They measured the rate of
methane production of 76 cattle over a fifteen-day period.
Some of the results are shown in Figure 3.
(2 marks)
When RFI is calculated, low values are negative. Explain why they
are negative.
Suggest a null hypothesis for this investigation.
(1 mark)
Scientists have developed a standard procedure for comparing
RFI in cattle. They control two factors. These are type of food and
environmental temperature. Explain why each of these factors
needs to be controlled.
Type of food
(1 mark)
Selectively breeding cattle with a low RFI may help to limit global
warming. Use the information in Figure 3 to explain how.
Environmental temperature
(4 marks)
(2 marks)
Unit 4: Chapter 5: Energy and ecosystems
Exam questions
The diagram shows organisms in a food web.
A pyramid of energy for this food web is shown below. The bars
are drawn to the same scale.
Use the pyramid of energy to calculate the percentage efficiency
of energy transfer between producers and primary consumers.
Show your working.
Name all the secondary consumers in this food web.
(1 mark)
Use the diagram to explain the likely effect of a sudden decrease
in the stickleback population on the population of mayfly larvae.
efficiency = .......................................... %
(2 marks)
The average efficiency of energy transfer between producers and
primary consumers in pyramids of energy is around 10 %.
Suggest why the efficiency of energy transfer from producers to
primary consumers in this food web is higher than 10 %.
(2 marks)
Energy from the sun may ultimately end up in dead plant matter.
Describe how.
(2 marks)
(2 marks)
Unit 4: Chapter 6: Nutrient cycles
6.1 The carbon cycle:
Key words:
Where does carbon enter the living component of the
ecosystem?
Where does carbon enter the non-living component of an
ecosystem?
What role is played by saprobiotic organisms in the carbon cycle?
ecosystem; producers; consumers;;
saprobiotic microorganisms; biomass;
green house gas; photosynthesis;
respiration; combustion; death; decay;
feeding
Explain the basis of all nutrient cycles using the diagram to help:
Describe where carbon enters the living and nonliving components of the ecosystem:
Fill in the carbon cycle:
Describe the role played by saprobiotic organisms in
the carbon cycle:
Unit 4: Chapter 6: Nutrient cycles
6.2 The greenhouse effect and global warming:
Key words:
What is the greenhouse effect?
Which are the major greenhouse gases and where do they come from?
Why is the production of greenhouse gases increasing?
How do greenhouse gases contribute to global warming?
What are the consequences of global warming?
greenhouse effect; greenhouse
gases; global warming; niches;
xerophytes; pathogens;
Describe what the greenhouse effect is:
State the main greenhouse gasses and describe where they
come from:
Describe what global warming is:
Explain the consequences of global
warming:
Unit 4: Chapter 6: Nutrient cycles
6.3 The nitrogen cycle:
Key words:
How is nitrogen recycled in ecosystems?
What is the role of saprobiotic microorganisms in this recycling?
What do you understand by the terms ‘ammonification’, ‘nitrogen fixation’ and
denitrification’?
Where does nitrogen enter the living component of an ecosystem?
Where does nitrogen enter the non-living component of an ecosystem?
ammonification; nitrification;
nitrogen fixation;
denitrification; saprobiotic
microorganisms
Complete the diagram of the nitrogen cycle:
Describe the following steps of the
nitrogen cycle:
Ammonification
Nitrification:
Nitrogen fixation
Denitrification:
Show where nitrogen enters the living and non-living component of
the ecosystem.
Unit 4: Chapter 6: Nutrient cycles
6.4 Use of natural and artificial fertilisers:
Key words:
Why are fertilisers needed in agricultural ecosystems?
How do natural and artificial fertilisers differ?
How do fertilisers increase productivity?
natural/organic fertilisers;
artificial/inorganic fertilisers;
Explain why fertilisers are needed
in agricultural ecosystems:
Explain how fertilisers increase
productivity
Explain how natural and artificial
fertilisers differ:
Unit 4: Chapter 6: Nutrient cycles
6.5 Environmental consequences of using nitrogen fertilisers:
Key words:
What are the main environmental effects of using nitrogen
fertilisers?
What is meant by ‘leaching’ and ‘eutrophication’?
How do these processes affect the environment?
species diversity; leaching;
eutrophication
Describe the main
environmental effects of
using nitrogen fertilisers:
Explain what leaching means and the effects it can have on the environment
Explain what eutrophication means and the effects it can have on the
environment:
Unit 4: Chapter 6: Nutrient cycles
Exam questions
The diagram shows the nitrogen cycle.
Leguminous crop plants have nitrogen-fixing
bacteria in nodules on their roots. On soils with a
low concentration of nitrate ions, leguminous crops
often grow better than other types of crop. Explain
why.
(2 marks)
Applying very high concentrations of fertiliser to the
soil can reduce plant growth. Use your knowledge
of water potential to explain why.
Name process P.
(1 mark)
Name process Q.
(1 mark)
(2 marks)
Unit 4: Chapter 6: Nutrient cycles
Exam questions
Much of Indonesia is covered with forest. Large
areas of forest have been cleared and planted with
oil-palm trees to be used in the production of fuel.
In these forests, nitrogen in dead leaves is made
available to growing plants by the action of bacteria.
Describe the role of bacteria in making the nitrogen
in dead leaves available to growing plants.
(5 marks)
Clearing the forests and burning the vegetation
affects the carbon dioxide concentration in the
atmosphere.
Describe how and explain why.
(4 marks)
Unit 4: Chapter 6: Nutrient cycles
Exam questions
Insect pests of crop plants can be controlled by chemical
pesticides or biological agents.
Give two advantages of using biological agents.
1
The ecologists concluded that in this investigation control of the
two-spotted mite by a biological agent was effective. Explain how
the results support this conclusion.
2
(2 marks)
Two-spotted mites are pests of strawberry plants. Ecologists
investigated the use of predatory mites to control two-spotted
mites. They released predatory mites on strawberry plants infested
with two-spotted mites. They then recorded the percentage of
strawberry leaves occupied by two-spotted mites and by predatory
mites over a 16-week period. The results are shown on the graph.
(2 marks)
Farmers who grow strawberry plants and read about this
investigation might decide not to use these predatory mites.
Suggest two reasons why.
1
2
(2 marks)
The ecologists repeated the investigation but sprayed chemical
pesticide on the strawberry plants after 10 weeks. After 16 weeks
no predatory mites were found but the population of two-spotted
mites had risen significantly. Suggest an explanation for the rise
in the two-spotted mite population.
Describe how the percentage of leaves occupied by predatory
mites changed during the period of this investigation.
(2 marks)
(2 marks)
Unit 4: Chapter 7: Ecological succession
7.1 Succession:
Key words:
What changes occur in the variety of species that occupy an area
over time?
What are meant by the terms succession and climax community?
How can managing succession help to conserve habitats?
abiotic; biotic; ecosystems;
communities; succession habitat;
climax communities; biodiversity;
biomass
Explain what is meant by the
terms:
succession:
Explain what changes occur in the variety of species that occupy an
area over time:
climax community:
Unit 4: Chapter 7: Ecological succession
7.2 Conservation of habitats:
Key words:
What is conversation?
How can managing succession help to conserve habitats?
ecosystem; biodiversity; ethical;
economic; cultural; aesthetic
Explain what conservation is:
Explain how managing succession can help to
conserve habitats:
Unit 4: Chapter 7: Ecological succession
Exam questions
Ecologists investigated succession in some
abandoned crop fields. The data that they collected
are shown in the graph. The curves show the trends
that occurred over a period of 60 years.
Explain the change in soil nitrate concentration
shown on the graph.
The pioneer plants had different characteristics
from the plants that colonised the fields after 50
years. The pioneer plants had seeds that germinate
better when the temperature fluctuates. Explain the
advantage of this to these pioneer plants.
(2 marks)
Explain the advantage to a plant that colonises after
50 years of having a high rate of photosynthesis at
low light intensities.
(1 mark)
Conservation of grassland habitats involves
management of succession. Use the data in the
graph to explain why.
(2 marks)
(2 marks)
Unit 4: Chapter 7: Ecological succession
Exam questions
Succession occurs in natural ecosystems. Describe
and explain how succession occurs.
Describe how you would investigate the distribution
of marram grass from one side of the dune to the
other.
(3 marks)
Marram grass is a pioneer species that grows on
sand dunes. It has long roots and a vertically
growing stem that grows up through the sand. Sand
dunes are easily damaged by visitors and are blown
by the wind. Planting marram grass is useful in
helping sand dune ecosystems to recover from
damage. Use your knowledge of succession to
explain how.
(5 marks)
(2 marks)
Unit 4: Chapter 7: Ecological succession
Exam questions
The diagram shows the dominant plants in
communities formed during a succession from bare
soil to pine forest.
The species that are present change during
succession. Explain why.
Name the pioneer species shown in the diagram.
(2 marks)
The pine trees in the forest have leaves all year.
Explain how this results in a low species diversity of
plants in the forest.
(1 mark)
(1 mark)
Unit 4: Chapter 8: Inheritance and selection
8.1 Studying inheritance:
What are meant by the terms ‘genotype’ and ‘phenotype’?
What are dominant, recessive and co-dominant alleles?
What are multiple alleles?
Key words:
Unit 4: Chapter 8: Inheritance and selection
8.2 Monohybrid inheritance:
How are genetic crosses represented?
How is a single gene inherited?
Key words:
Unit 4: Chapter 8: Inheritance and selection
8.3 Sex inheritance and sex linkage:
How is sex determined genetically?
What is sex linkage?
How are sex linked diseases such as haemophilia inherited?
Key words:
Unit 4: Chapter 8: Inheritance and selection
8.4 Co-dominance and multiple alleles:
How does co-dominance affect the inheritance of characteristics?
How do multiple alleles affect inheritance?
How are blood groups in humans inherited?
Key words:
Unit 4: Chapter 8: Inheritance and selection
8.5 Allelic frequencies and populations:
What are meant by the terms ‘gene pool’ and ‘allelic frequency’?
What is the Hardy-Weinberg principle?
How can the Hardy-Weinberg principle be used to calculate allele,
genotype and phenotype frequencies?
Key words:
Unit 4: Chapter 8: Inheritance and selection
8.6 Selection:
How does reproductive success affect allele frequency within a
gene pool?
What is selection?
What environmental factors exert selection pressure?
What are stabilising selection and directional selection?
Key words:
Unit 4: Chapter 8: Inheritance and selection
8.7 Speciation:
What is speciation?
What is geographical isolation?
How can geographical isolation lead to the formation of new
species?
Key words:
Unit 4: Chapter 8: Inheritance and selection
Exam questions
More exam questions
January 2010
Question 1 – Chapter
Question 2 – Chapter
Question 3 – Chapter
Question 4 – Chapter
Question 5 – Chapter
Question 6 – Chapter
Question 7 – Chapter
Question 8 – Chapter
June 2011
Question 1 – Chapter
Question 2 – Chapter
Question 3 – Chapter
Question 4 – Chapter
Question 5 – Chapter
Question 6 – Chapter
Question 7 – Chapter
Question 8 – Chapter
June 2010
Question 1 – Chapter
Question 2 – Chapter
Question 3 – Chapter
Question 4 – Chapter
Question 5 – Chapter
Question 6 – Chapter
Question 7 – Chapter
Question 8 – Chapter
January 2012
Question 1 – Chapter
Question 2 – Chapter
Question 3 – Chapter
Question 4 – Chapter
Question 5 – Chapter
Question 6 – Chapter
Question 7 – Chapter
Question 8 – Chapter
January 2011
Question 1 – Chapter
Question 2 – Chapter
Question 3 – Chapter
Question 4 – Chapter
Question 5 – Chapter
Question 6 – Chapter
Question 7 – Chapter
Question 8 – Chapter
June 2012
Question 1 – Chapter
Question 2 – Chapter
Question 3 – Chapter
Question 4 – Chapter
Question 5 – Chapter
Question 6 – Chapter
Question 7 – Chapter
Question 8 – Chapter
January 2013
Question 1 – Chapter
Question 2 – Chapter
Question 3 – Chapter
Question 4 – Chapter
Question 5 – Chapter
Question 6 – Chapter
Question 7 – Chapter
Question 8 – Chapter