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KS4 Biology B16a / Side 1

Ecosystems-the habitat and communityThe ecosystem is defined as the habitat and the community together.The habitat is the area where organisms are found e.g. a forest.The community describes all the different species of plants and animals within that habitat.Complete the table by choosing the correct word from the list below to match each of the descriptions.

community ecosystem habitat populationDescription Word

A group of organisms of the same species, living and breeding togetherThe place where an organism livesAll the organisms, of many different species, which live together in the same areaA group of living organisms, and their environment, which interact with each otherOrganisms that live in a particular habitat are adapted to live in that place. Use your textbook and http://mbgnet.mobot.org to fill in the table below.

Ecosystem Environmental conditions

Typical organisms in community

Adaptations shown by organisms

Sha Tin College Science Department - May 23

http://mbgnet.mobot.org/

KS4 Biology B16b / Side 1

Feeding Relationships

The organisms within a community feed on one another. The feeding relationship may be mapped out as food chains and webs. A number of different organisms from a microhabitat -under a stone- were placed in different Petri dishes with lids to see how they would behave. The dishes were left for a couple of days in a cool, dark place. This is what happened:

Use the information to complete these sentences:1. A centipede eats __________________________________2. A millipede eats ___________________________________3. A woodlouse eats __________________________________4. Write out the food chain for this microhabitat


KS4 Biology B16c / Side 1

Introduction to Food Chains

Look at the following web pages and in your textbook to remind yourself from key stage 3 about food chains, webs and energy flow. Then try the following questions.www.geog.ouc.bc.ca/physgeog/contents/4e.htmlwww.vtaide.com/png/foodchains.htmhttp://users.rcn.com/jkimball.ma.ultranet/BiologyPages/F/FoodChains.html

1. What do food chains show?

_____________________________________________________________

2. Look at this food chain. What do the arrows in the food chain show? _____________________________________________________________

3. What is meant by a trophic level?

_____________________________________________________________

4. A food chain always starts with a producer. How do producers get food?

_____________________________________________________________


http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/F/FoodChains.html

http://www.vtaide.com/png/foodchains.htm

http://www.geog.ouc.bc.ca/physgeog/contents/4e.html

KS4 Biology B16c / Side 2

5. From the above food chain, give the names of:i. The producer

____________________ii. The primary consumer

____________________iii. The secondary consumer

____________________iv. The herbivores

_____________________________________________________v. The carnivores

_____________________________________________________

6. PRODUCER HERBIVORE CARNIVORE

DEAD MATTER DECOMPOSERS

a. What two groups of organisms do decomposers usually belong to?________________________________________________________

b. What process is represented by the arrows pointing to dead matter?________________________________________________________

c. Why do the arrows run in two directions between decomposers and dead matter?________________________________________________________

d. Decomposers are very important organisms. Describe two problems that would arise if there were no decomposers. ________________________________________________________________________________________________________________


KS4 Biology B16d / Side 1

Food Webs

Below is a simple food web in a pond:

Pike (fish)

Water beetles

Perch (fish)

Tadpoles Minnows (fish)

Weeds

a. Write out three food chains you can see in this web. b. What do water beetles eat?c. What will happen to the water beetles if the minnows die off?d. A food chain is more easily destroyed than a food web. Use the web above

to explain why.


KS4 Biology B16d / Side 2

Answer the following questions by circling the correct letter(s) or by choosing the correct word or phrase to complete the statement correctly.

1. Which letter(s) indicate the producer(s)? A B E F G H L N O P R2. Which letter(s) indicate the secondary consumer(s)? A B E F G H L N O P R 3. If population N suddenly got smaller, population G would increase decrease not change4. If population N suddenly got smaller, population H would increase decrease not change5. If population G suddenly got larger, population A would increase decrease not change6. If population L suddenly got larger, population P would

increase decrease not change7. If population P suddenly got smaller, population L would

increase decrease not change8. If population F suddenly got larger, population R would

increase decrease not change9. Explain how you arrived at your answer to 8


KS4 Biology B16d / Side 3Questions1. Diagram below shows a food web which includes some organisms in the

African grasslands.

(a)(i) In the space below draw a food chain consisting of four organisms.

The organisms must be part of the food web. [2]

(ii) Using examples from the food web, explain the difference between producers and consumers. [4]


giraffe

lion

gazelle

acacia tree

scops owl

elephant shrew

grasshopper

oxpecker bird

tick

water buffalo

chameleon

click beetle

grass

KS4 Biology B16d / Side 42. Aphids are insects which feed on broad bean plants by sucking the sap from

the leaves and stem. The aphids in their turn form a large part of the diet of Blue Tits. Blue Tits

are preyed upon by Sparrow-Hawks.

The bar chart shows the number of these organisms likely to be found in a given habitat at different times of the year.

(a) In the food chain what biological term is given to the broad bean plants?

(b)Explain why there has been an increase in the number of aphids in July?

(c) Suggest why the number of aphids had fallen in August?

(d)Suggest why the blue tit population increased in July but decreased in August?


KS4 Biology B16d / Side 53. Complete this paragraph (which is about energy flow).

(a)Food chains, webs and pyramids are ways of representing the flow of _______________ through an ecosystem. The original source of energy is the _______________. Green plants use this energy to manufacture _______________ in the process of _______________. This energy is transferred along a food chain to the _______________. At each step in the chain energy is lost because each consumer _______________ some of it for its own life processes. During the process of decay, the energy in dead bodies and excretory material is passed on to _______________. [4]

(b)State two ways in which energy is lost along a food chain. [2]

(c) Explain why(i) The number of organisms decreases at each trophic level in an

ecosystem. [2]

(ii) The territories of top predators are usually very large. [2]

(iii) There are rarely more than five links in a food chain. [2]


KS4 Biology B16d / Side 64. Three species of squirrel, known as Loga, Jirit and Soksak, live in trees in the

same forest in Indonesia. The squirrels were observed and a record kept of their heights above ground. Diagram below shows the vertical distribution of these species.

(a)(i) Using the diagram, describe the distribution of each species. [6]

Loga Jirit Soksak

(ii) Suggest why the Soksak may be at greater risk of predation than the other two species. [1]


KS4 Biology B16d / Side 7Diagram below shows the diets of the three species of squirrel.

(b)(i) State which types of food are found in all three diets. [1]

(ii) Suggest two reasons why the three species can survive together in

the same forest, even though they have these types of food in common. [2]1. 2.

(c)(i) The insects in the diet of Loga feed on fruit.

Draw a food web for Loga using information from the above diagram.[3]

(ii) Name the trophic level in this food web for [3]Insects; Fruit; Loga (when feeding on insects)


KS4 Biology B16d / Side 85. Diagram below shows some of the interactions between organisms living in

the North Atlantic Ocean.

(a)(i) Draw a food chain of four organisms, indicating the flow of energy

though the chain by arrows. [1]

(ii) Name the process, carried out by the living organisms, which produces carbon dioxide. [1]

(iii) Name the process in the phytoplankton which uses the energy they absorb. [1]

(iv)State the source of energy for the food web. [1]


phytoplankton (microscopic plants)

seal

small crustaceans

energy

Carbon dioxide

mackerelherring

KS4 Biology B16d / Side 9(b)The flow of energy through a food web is described as non-cyclical while

the flow of carbon through the web is cyclical. Explain the difference between these two statements. [3]

(c) Overfishing of both herring and mackerel has occurred in the North Atlantic. Suggest and explain the effect this could have on the numbers of seals and phytoplankton in the food web. [3]


KS4 Biology B16d / Side 10Extension – supplementary level

PopulationsA biological population is described as the total numbers of any one individual species in a particular habitat.

Population growthIn the simplest case where a single species is allowed to grow in a laboratory, the population will develop more or less as shown below:

The types of organisms grown in a laboratory like this are usually simple organisms such as yeast, flour beetles and a single celled organism known as a Paramecium. The graph above illustrates the growth of Paramecium which reproduces by dividing into two in a type asexual reproduction known as binary fission.

Give three features of asexual reproduction:


KS4 Biology B16d / Side 11Extension – supplementary levelGive two advantages of asexual reproduction: Give one major disadvantage of asexual reproduction:

The different stages of the sigmoid (s-shaped) curve can be explained follows:

Section A:The population increase is exponential i.e. 2, 4, 8, 16, 32 etc. rather than 2, 4, 6, 8 etc.Why is the population able to grow exponentially?

Section B:The population begins to grow but at a steady rate.Explain why this may be happening:

Section C:At this point the population ceases to grow.Explain why:


KS4 Biology B16d / Side 12Extension – supplementary levelAfter this stage the population may start to decline. This can happen because food supply is insufficient, waste products contaminate the habitat or disease spreads through the dense population.

Limits to population growthThe sigmoid curve is a very simplified model of population growth.

Explain this statement above:

The steady state of the population in part C is very rarely reached in nature. In fact the population is unlikely to reach its maximum theoretical level because of many factors which can limit its growth. These are known as limiting factors.

Limiting Factors

CompetitionIn the graph below shows what happens to the populations of two different species of Paramecium. The population of P.Aurelia follows the sigmoid curve but the population of P. caudatum soon declines to zero.


KS4 Biology B16d / Side 13Extension – supplementary levelIn the above example the two species are competing for food.Name some other resources that populations could compete for: Abiotic and Biotic Limiting Factors

Abiotic factors are non-living or non-biological factors than can affect the size of a population.

Name some abiotic factors that will affect plant populations: Name some abiotic factors which will affect animal populations:

Biotic factors are biological or living factors that can affect the size of a population.

Name some biotic factors which will affect plant populations: Name some biotic factors which will affect animal populations:


KS4 Biology B16d / Side 14Extension – supplementary levelPredator-Prey RelationshipA classic example of a predator prey relationship is between the snowshoe hare and the Canadian

Lynx. The Lynx preys on snowshoe hares.

Looking at the graph try to explain the fluctuations in the two populations:


KS4 Biology B16d / Side 15Extension – supplementary levelQuestions1. In the summer of 1998 about 2000 mink were released from captivity into

one area of forest in Southern Britain. Mink are aggressive carnivorous mammals.The graph shows how the population of mink might change over a few years if there were no human interference.

(a)State three factors which would cause the mink population to become constant. [3]1. 2. 3.

(b)It might be expected that a graph for human world population would show a similar pattern. However, it is now thought that the human population will continue to grow steadily. Suggest three reasons why this might happen. [3]1. 2. 3.


KS4 Biology B16d / Side 16Extension – supplementary level2. Sheep were first taken to the island of Tasmania in 1814. Diagram below

shows changes in the size of the sheep population in Tasmania between 1818 and 1930.

(a) State the size of the sheep population in 1842. [1]

(b)(i) Suggest biological reasons for the sheep rise in the number of sheep

between 1830 and 1840. [2]

(ii) Suggest biological reasons for the shape of the curve between 1870 and 1890. [2]


KS4 Biology B16d / Side 17Extension – supplementary level3. Young mosquitoes (larvae) feed on water plants, such as Chlorella.

However, adult female mosquitoes feed on the blood of mammals, such as cows, horses and humans. During the process, they can transmit diseases, such as malaria.The mosquitoes produce only one protease enzyme, called trypsin. Scientists have identified a hormone that switches off the ability of mosquitoes to secrete trypsin. They genetically modified Chlorella to make the hormone and introduced the plant into lakes where mosquitoes are a problem. This reduces the population of mosquitoes and should help to prevent the spread of malaria. Other animals that eat Chlorella are not affected because they do not depend on trypsin alone.(a)

(i) Explain why an adult female mosquito needs to secrete trypsin. [2]

(ii) What product would be present in the gut of a mosquito if trypsin had been active? [1]

(iii) Suggest one use of this product in the body of the mosquito. [1]

(b)Suggest why developing the genetically modified Chlorella may be a better way of killing mosquitoes than using insecticides. [3]

(c) Food supply is one factor that affects the growth of a population.State two other factors that also affect population growth. [2]1. 2.


KS4 Biology B16d / Side 18Extension – supplementary level4. A farmer sprayed fertilisers containing ammonium nitrate onto a field in

which young wheat seedlings were growing.(a)Explain why farmers often add nitrogen-containing fertilisers to the soil

where crops are growing. [2]

(b)(i) Describe how the ammonium and nitrate ions would be absorbed by

the wheat plants. [2]

(ii) Name the tissue that would transport the ammonium and nitrate ions through the plant. [1]

(c) Some of the fertiliser was washed into a river which can alongside the wheat field.Diagram below shows how this affected the numbers of bacteria, algae and fish in the river, downstream from the wheat field. It also shows how it affected the oxygen concentration.

(i) Explain the shape of the curve for the numbers of algae. [2]

(ii) With reference to the curves for the bacteria and oxygen in the above diagram, explain the shape of the curve for fish. [4]


KS4 Biology B16e / Side 1

Energy Flow through a Food Chain

Below is a simplified diagram to show energy flow through a food chain. The numbers below each organism indicate the amount of energy available to the next link in the chain.

1. How much energy is lost as waste products from the herbivore? Show workings.

_________________________________________________________

_________________________________________________________

2. What percentage of energy available to the herbivore passes to the carnivore? Show your workings.

_________________________________________________________

_________________________________________________________

3. What exactly is the function of chlorophyll in the food chain?

_________________________________________________________

4. Explain why it is better for humans to obtain their energy from plants rather than animals.

_________________________________________________________

_________________________________________________________


KS4 Biology B16e / Side 2Extension – supplementary student onlyIn Tanzania, farmers grow and harvest maize as food for people. They also keep Zebu cattle, which feed on grass and other plants. People drink milk from the cattle, and eat them as meat. This can be shown as food chains:

a. Name the trophic level of the following organisms in food chain 2. [2]Grass Zebu cattle

b. The diagram shows the amount of energy passing between each trophic level in the two food chains, for each 100,000kJ of energy entering the food chains.

(i) State the form in which 100,000kJ of energy enters each food chain.[1]

(ii) Explain why, in food chain 2, there is less energy passed on to the humans than to Zebu cattle. [2]

c. Where it is difficult to produce enough food to feed the human population, it has been suggested that it is better to grow crops rather than to keep farm animals.Explain one reason why more people could be fed if farmers grew maize for food, rather than keeping Zebu cattle for milk and meat. [2]


Food chain 1

Food chain 2

Maize humans

Grass zebu cattle humans

Food chain 1

Food chain 2

100 000kJmaizecrop

3000kJhumans

100 000kJgrass and

other plantszebu cattle humans

4000kJ 200kJ

KS4 Biology B16e / Side 3Extension – supplementary student only

Energy Flow through a Meadow

1. Use the information in the diagram to calculate the amount of energy absorbed by plants during photosynthesis each year.

2. Name the process which accounts for the annual transfer of 2000kJ/m from plants to the surroundings.

3. a. Calculate the percentage of the birds` energy transferred to the surroundings.b. The arthropods transfer 84% of their energy to the surroundings. State

one difference between birds and arthropods, which causes the birds to transfer a higher % of their energy to the surroundings.

c. The transfer of energy from plants to herbivores is less efficient than the transfer of energy from herbivores to carnivores. Suggest why the energy transfer from plants to herbivores is less efficient.

4. The energy efficiency of the meadow plants is the energy used for growth as a proportion of the energy from the sun. Calculate the energy efficiency.

5. Some fields are now being sown with oil seed rape. Seeds from oil seed rape can be used to produce diesel oil. The energy efficiency of an oil seed rape field is similar to that of a meadow. The energy efficiency of a solar cell is 10%. Suggest one advantage and 2 disadvantages of using diesel oil from oil seed rape as an energy source instead of using solar cells.


KS4 Biology B16e / Side 4Extension – supplementary student only

Study the diagram above and use it to explain why it might be an advantage to eat plant products rather than animal products, in terms of the amounts of energy available in a food chain.


KS4 Biology B16f / Side 1Extension – supplementary student only

Pyramids of Numbers and Pyramids of Biomass

A pyramid of numbers is a way of showing the number of organisms at each level of a food chain. The numbers of organisms in a woodland chain were counted.

Oak leaves Caterpillars

Blue tits Hawks

20,000 1,800 120 6

A pyramid of number was constructed using this information. Label each level of the diagram.

1. Draw a pyramid of number for this food chain.

Leaves Earthworms

Shrews Owls

30,000 2,000 100 5


KS4 Biology B16f / Side 2

2. Draw a pyramid of number for this food chain.

Rose bush Aphid Ladybird Blue tit6 12,000 150 2

3. Why is this pyramid a funny shape?

_________________________________________________________

4. A more accurate picture is given by a pyramid of biomass. Draw a pyramid of biomass for the same food chain using the following data.

Rose bush Aphid Ladybird Blue tit120kg 8kg 0.5kg 0.08kg



5. Phytyplankton ----- krill---- blue whale

a. It has been estimated that 4 million square kilometres of Antarctic Ocean contains up to 70 million tonnes of krill. If the krill population covers 36 million square kilometres of ocean in summer, what is the total biomass at this time? Show workings.

b. Will the biomass of phytoplankton be greater of smaller than the biomass of the krill? Explain your answer.

c. In winter much of the ocean where the krill live becomes covered in ice and little light penetrates. Explain how this could cause a reduction in the krill population.



6. Monpane trees grow in southern Africa. Some ecologists collected all the organisms living on a small mopane tree. They identified the organisms, and determined which trophic level each of them belonged to. Their results are shown in the table.

Trophic level Number of organismsProducers 1Primary consumers 250,000Secondary consumers 90Tertiary consumers 5

(a)Sketch the shape of a pyramid of biomass to represent the mopane tree ecosystem.Label the parts of the pyramid you have drawn.



(b)Suggest reasons for the shape of the pyramid you drew in (a). [3] The most abundant primary consumers on the mopane tree were caterpillars known as mopane worms. These caterpillars are roasted or dried and then eaten by people in many parts of southern Africa, as they are an excellent source of protein.

(c) State two factors which might limit the growth of the population of mopane worms. [2]1. 2.

(d)Outline the processes by which protein from a mopane worm would be digested and absorbed, after being eaten by a person. [4]



7. Table below shows the nutrient content in 100g of four foods. Wheat flour and cabbage are derived from plants, while chicken and eggs are from animals.

Food Energy /kJ

Protein/ g

Fat/ g

Carbo-hydrate

/gIron/mg

Calcium/mg

Vitamin C/mg

Wheat flour 1340 13.0 2.0 66.0 4.0 35 0

Cabbage 60 1.7 0 2.0 0.4 40 20

Chicken 920 23.0 14.0 0 0.8 0 0

Eggs 630 12.3 10.9 0 2.0 50 0

(a)Calculate how many times greater the carbohydrate content of cabbage is than its vitamin C content. [2]

(b)State the nutrient shown in the table that is found in both plant foods but

neither animal food, and suggest why this is so. [2]

(c) Carbohydrates are a major source of energy of food.(i) Which two other nutrients are sources of energy? [2]

1. 2. (ii) Describe how energy is released from the carbohydrate glucose inside

a cell. [2]



(d)Diagram below shows a food chain and a pyramid of biomass based on this food chain.

(i) Explain why the pyramid of biomass is this shape. [2]

(ii) The pyramid of biomass indicates that we could obtain more energy from the same area of land if we ate plant products rather than animal products. However, in many parts of the world, most farmers keep animals and eat animal products such as milk, eggs and meat.Suggest reasons for this. [2]


cabbage chicken human

humans

chickens

cabbages


8.(a)For each of the following pyramids of numbers choose the correct food

chain which it represents. Write out the food chain below its pyramid.

Food chains:

Wheat rat flea oak tree aphid bird

Grass rabbit fox cabbage caterpillar wasp parasite



(b)(i) If the mass of organisms at each trophic level was measured instead

of numbers, what would the pyramid look like in each case? Draw the shape.

(ii) This is called a pyramid of biomass. What is biomass?

(iii) Why is it important to use the dry mass in such measurements?


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