Syllabus Edition

First teaching 2014

Last exams 2024

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Species, Communities, Ecosystems & Energy Flow (DP IB Biology: SL)

Exam Questions

3 hours36 questions
1a1 mark

Give the definition of a species.

1b1 mark

The image shows a woodland food web.

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What word is used to collectively describe all the interbreeding foxes in the woodland represented by this food web?

1c1 mark

Identify all the primary consumers from the forest food web.

1d2 marks

Consumers in this forest food web obtain organic molecules through eating organisms in the trophic level before.

Which two elements do all organic molecules contain?

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2a2 marks

This is a simple food web found in an ocean ecosystem.

food chain atlantic ocean

Identify an example of an organism from the food web which obtains food using the method of nutrition named in the table.

Autotroph  
Heterotroph  

2b1 mark

Identify an organism (or a group of organisms), not shown in the ocean food web, which feeds on all trophic levels of the food chain.

2c3 marks

Each of the three sentences about ecosystems contains one error.

  • In a functioning ecosystem, organisms are constantly recycled.
  • Detritivores obtain inorganic nutrients from the abiotic environment and convert them to organic molecules during photosynthesis.
  • Decomposition is fundamental in ensuring that ecosystems remain unsustainable over long periods of time.

Identify and replace the incorrect word in each sentence.

2d2 marks

Where does the organism in the first trophic level of this ocean food web obtain the carbon that it uses to build organic molecules?

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3a5 marks

Place a (✓) or (X) in the correct columns for each of the factors listed in the table below:

  Biotic Abiotic
Sunlight    
Predation    
Food availability    
Mineral availability    
Temperature    

3b1 mark

Abiotic factors can be controlled in order to study the response of a naturally occurring ecosystem using the set up below.42_KhR2j_e-3b

What is the name given to the set up shown in the image which allows the study of ecosystems?

3c3 marks

Suggest why the experiment set up in part b) should include the following features:

  • A transparent container
  • A lid to seal the container
  • Minimal primary consumers and no secondary consumers
3d2 marks

A mesocosm was set up to study the effect of increasing global temperatures on the biomass of aquatic autotrophs and heterotrophs.

The graph shows the data collected.

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Describe what happened to the biomass of heterotrophs and autotrophs as temperatures increased from 21 °C to 27 °C.

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4a2 marks

When a consumer eats another organism, it converts chemical energy into other forms of energy, such as heat energy. This is represented in the energy transfer diagram below.

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Complete the diagram to identify the main energy transfer carried out by producers in a food chain.

4b
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2 marks

A blackbird ate snails containing 1150 kJ of energy. Only 10% of this energy was transferred to the blackbird.

Calculate the energy transferred from the snails to the blackbird.

4c3 marks

Identify three functions of life which rely on energy transferred in respiration.

4d2 marks

The diagram shows the movement of energy through a food web.

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Explain why energy is transferred to the environment at each trophic level.

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5a5 marks

One mark is available for clarity of communication throughout this question.

Describe how a quadrat could be used to study the distribution of a particular species of clover plant in a meadow compared to a forest.

5b4 marks

Outline some of the reasons that energy is lost between each trophic level of the food chain.

5c6 marks

Describe, with examples, the different modes of nutrition used by organisms.

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1a1 mark

The diagram shows the flow of energy through a sheep. The figures are in kJ × 106 year–1.

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Suggest what label F represents

1b1 mark

Calculate the value of P. Give your answer in kJ × 106 year–1.

1c2 marks

A sheep farmer wanted to increase the amount of energy used for the production of new tissue (P) in his livestock (his sheep). 

Suggest two methods that could be used by the farmer to achieve this.

1d3 marks

When the sheep have grown to a specific body mass they can be consumed for food by humans. Assume that the sheep consume grass, and that humans gain 0.57 kJ x 106 year-1 from eating sheep meat. 

Draw a labelled pyramid of energy to represent this food chain.

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2a2 marks

Elodea canadensis (Canadian pondweed) is a species of aquatic plant from North America. A student grew Elodea canadensis, along with a pondweed species native to the UK, in water tanks both separately and together. The graphs below show their results.

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State two abiotic factors the student should have controlled throughout the experiment. 

2b1 mark

Calculate the difference in biomass between native pondweed grown separately and native pondweed grown in a tank together with E. canadensis after 15 days. 

2c2 marks

Explain the results for native pondweed for when both species of pondweed are grown together.

2d3 marks

Evaluate the benefit of mesocosm experiments, similar to the one in part (a), in understanding interactions between organisms in their natural environment.

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3a2 marks

Ecologists studied a rocky shore habitat which contained, among other organisms, several barnacle species, purple topshell snails (Gibbula umbilicalis), seaweeds, and lichens. 

State, with a reason, which of the organisms listed above make up a single population. 

3b3 marks

The ecologists wanted to find out whether there was an association between the distributions of purple topshell snails and the common rock barnacle, Semibalanus balanoides. 

Outline the method ecologists would use to collect data to determine whether or not such an association existed.

3c2 marks

A chi-squared test was carried out to determine whether or not there was a significant association between purple topshells and common rock barnacles on a rocky shore. When the calculated chi-squared value was compared to values in a critical values table it was found to be smaller than the critical value at a 0.05 probability level. 

Deduce what can be concluded from this analysis?

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4a3 marks

The diagram below shows a soil food web.

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State the specific mode of nutrition used by the following organisms:

(i)

Plants

(ii)

Fungi

(iii)

Root feeding nematode worms

4b1 mark

Draw a food chain that includes bacteria from the food web shown above

4c2 marks

The longest food chain in the food web above contains 7 organisms. Explain why it is unusual to see food chains of this length.

4d3 marks

Outline how the soil food web will be affected by a farmer harvesting crop plants from a field.

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5a7 marks

One mark is available for clarity of communication throughout this question.

Outline the processes by which energy flows through ecosystems.

5b3 marks

Some plants are parasitic, gaining their carbon compounds by tapping into the roots of other plants, for example. 

Explain how this mode of plant nutrition is unusual.

5c5 marks

Explain the concept of ecosystem sustainability.

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1a4 marks

The images show two organisms from the genus Canis.

Grey wolves, Canis lupus, are wild animals native to Eurasia and North America.

Domestic dogs, Canis familiaris, descended from wolves and became domesticated over many years.B~jb5Ls4_h-1a

A wolfdog is a hybrid produced when a domesticated dog (Canis familiaris) breeds with a wolf (Canis lupus). Genetically, dogs and wolves are very similar and the resulting offspring are fertile. Wolfdog hybrids are rare as natural habitats and territorial behaviours isolate wolves from domestic dogs.

Using the information provided, discuss the validity of the claim that wolves and dogs are the same species.

1b4 marks

Suggest how isolation may result in the development of a new species.

1c2 marks

A taxonomist suggested that the wolf and the domestic dog should be re-categorised as follows:

  • Canis lupus familiaris
  • Canis lupus lupus

Identify the genus name and the species name for the wolf and the domestic dog under this re-categorisation.

1d3 marks

Outline how artificial selection has led to the domestication of wolves over many years to result in the domestic dogs of the modern day.

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2a4 marks

All ecosystems are powered by autotrophic organisms.

Discuss this statement.

2b3 marks

Spirulina (Athrospira platensis) is a blue-green alga that is consumed for its nutritional benefits, which are considered to be good for oral health, eye health and maintaining healthy blood pressure, amongst other benefits.

The graph shows the results from an investigation into the optimum growing conditions for Spirulina. 

Spirulina was grown in a glucose medium and exposed to different intensities of light. The same method was carried out with an autotrophic species of alga.

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Explain how the results show that Spirulina is a mixotrophic organism.

2c2 marks

Compare the growth rate of Spirulina and the autotrophic algal species when light intensity was increased from 0 to 200 lx.

2d2 marks

Suggest how Spirulina may be adapted to function as a mixotroph.

2e2 marks

Another species of alga, Cephaleuros virescens, has been identified as a plant pathogen living on the leaves and fruit of guava plants in Hawaii. C. viscerens is non-photosynthetic and has been shown to cause a disease known as leaf and fruit spots.

Identify, with a reason, the mode of nutrition that is represented by C. viscerens.

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3a4 marks

Many large marine ecosystems across the world's oceans boast high productivity and biodiversity. As a result, they contribute substantially to the global economy through practices such as fishing.

The map below shows 66 large marine ecosystems, which are identified as being key areas of conservational interest, due to the risks associated with their proximity to developed coastlines and the impact this may have on the biodiversity of these ecosystems.

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Suggest four abiotic factors that may impact communities living within large marine ecosystems.

3b4 marks

A basic food web for a large marine ecosystem can be seen below.

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Nutrient-rich sewage from coastal settlements results in rapid growth of algae (algal blooms), which leads to a reduction in light intensity on the ocean floor.

Suggest the general effects this may have on a community in a marine ecosystem.

3c4 marks

Since 2013, numbers of starfish in the large marine ecosystems have been seen to dramatically reduce by up to 80% in some regions.

Starfish act as detritivores in the marine ecosystems, feeding on dead and decaying organic matter, as well as preying on organisms such as mussels and limpets.

Some scientists have suggested that a decline in starfish numbers may have a positive impact on the marine ecosystem.

Evaluate this statement.

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4a4 marks

Scientists investigated the production of high nutrient compost made from organic household waste.

The method they used was as follows:

  1. Place waste in a large container for 125 days
  2. Rotate the container each day
  3. Record the temperature of the waste every 25 days
  4. Remove samples of waste and test nutrient content

The temperature changes that they recorded were as follows:

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Describe and explain what these data show about the processes occurring in the composter.

4b2 marks

Explain the reason for step 2. in the method described in part a).

4c3 marks

Nutrient content of the compost was measured at the start and the end of the process.

The results can be seen in the chart below.0cF3o2T9_h-4c

Suggest reasons for the changes in carbon and nitrogen shown in the graph.

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5a4 marks

One mark is available for clarity of communication in this question.

Outline how scientists may simulate a naturally occurring ecosystem to establish how the sustainability of that ecosystem may be influenced by global warming.

5b3 marks

Explain the use of the chi-squared test to analyse data collected from the simulated ecosystem.

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