The Organism in the Environment

A scientist uses this method to investigate the effect of water quality on the growth of fish.

• fill a pond with filtered water
• fill another pond with unfiltered water
• place the same mass of fish of the same species in each pond
• determine the increase in total mass of fish in each pond after 180 days

The graph shows the scientist’s results.

The mean rate of increase in total mass of the fish in the filtered water is 0.214kg per day.

Calculate the difference between the mean rate of increase in the total mass of the fish in filtered and unfiltered water.

Unfiltered water contains more bacteria.

Explain why unfiltered water containing more bacteria affects the growth of fish.

Give one biotic variable the scientist controlled in the investigation.

Give a method the scientist could use to control interspecific predation in the ponds.

Separate: Biology Only

The biodiversity in an ecosystem can be determined by counting the number of different species present and the number of individuals of each species present.

Give the term that describes the number of individuals of one species present in a habitat at one time.

Separate: Biology Only

Students compared the biodiversity of two fields, A and B.

They determined the number of individual plants of three species in each field.

They also calculated the percentage of each species of plant compared to the total number of plants of all three species for each field.

The table shows the results.

Complete the table by calculating the missing values.

(2)

Explain which field has the greater biodiversity.

(2)

Explain how a shortage of one named mineral could affect the size of plants in the fields.

Deforestation is the cutting down of trees.

After deforestation, many dead leaves are left on the forest floor.

A student investigates the decomposition of these leaves.

This is her method.

• Collect four samples of dead leaves each with a mass of 6.0kg
• Label the samples P, Q, R and S
• Cut sample P into small pieces and keep at 10°C
• Cut sample Q into small pieces and keep at 20°C
• Do not cut sample R and keep it at 10°C
• Do not cut sample S and keep it at 20°C
• Measure the mass of each sample after three months

The graph shows her results.

Explain the results obtained by the student.

Calculate the difference between the rate of decomposition in sample P and the rate of decomposition in sample Q.

Give your answer in kg per month.

The student needs to control biotic variables in her investigation.

Give two biotic variables she should control.

Genetic modification is a process used to improve crop yield.

Describe the role of a named vector in the process of genetic modification.

Weeds are plants that grow where they are not wanted.

Removing weeds reduces competition for mineral ions and improves crop yield.

Name the mineral ion used to make chlorophyll.

(1)

Two different methods can be used to remove weeds to improve crop yield.

• Method A: pull weeds out of the ground by hand

• Method B: spray weeds with a chemical that kills them

Design an investigation to find out which method produces the highest crop yield.

Include experimental details in your answer and write in full sentences.

(6)

The table gives some examples of biological processes.

Complete the table by giving the name of each process.

The first one has been done for you.

Zinc is poisonous to many plants and can affect natural selection.

A scientist investigates the ability of one grass species to survive at different distances from a zinc mine.

The scientist uses a sampling method to measure the percentage cover of this grass species at different distances from the zinc mine.

The graph shows the scientist’s results.

The zinc concentration in soil is higher near the zinc mine than it is further from the zinc mine.

Explain how natural selection could be responsible for the results shown in the graph between 0 and 100 metres.

(4)

Describe a method the scientist could use to compare the population size of the grass species at 50 metres and 100 metres from the mine.

(4)

Separate: Biology Only

A group of students compares the distribution of plant species in two fields using this method.

• Use random sampling
• Use a 0.5m × 0.5m quadrat
• Count the number of each species in a quadrat

Repeat this method for five quadrats in each field.

The tables show the students’ results

Describe how the students would obtain random samples from each field.

Separate: Biology Only

Calculate the mean number of dandelions per quadrat in field B.

(1)

Calculate the number of dandelions per m² in field B

(1)

Separate: Biology Only

Describe the differences in species distribution in field A and field B.

Separate: Biology Only

A teacher suggests that there are no buttercups in field B because of poor water drainage from the field.

Describe what further experiment the students could do to investigate this suggestion.