The Organism in the Environment (Edexcel GCSE Biology: Combined Science)

Figure 1 shows some apparatus set up to test the effect of an abiotic factor on the rate of photosynthesis in pondweed.

Identify the abiotic factor being tested in this investigation.

Figure 2 shows the number of bubbles produced when the light source was placed at different distances away from the pondweed. 

Calculate the mean number of bubbles per minute when the light source was 20 cm from the pondweed.

Explain why the mean number of bubbles per minute can be used to reflect the rate of photosynthesis in pondweed.

Identify one other relevant abiotic factor and explain how it would affect the rate of bubbles being produced by the plant.

Describe the key features of a parasitic relationship.

The survival of some organisms may depend on mutualism.

Explain, using three examples, how some organisms benefit from mutualism.

A tapeworm is a parasite which attaches to its host's intestinal wall and absorbs ready-digested nutrients into it's body by diffusion.

Suggest why this may cause harm to the host organism.

Figure 1 shows the data collected about the populations of two species of small mammal in a woodland ecosystem.

Figure 1

Describe and explain the pattern shown in the data in Figure 1.

Calculate the ratio of voles to mice collected in 2007.

In the woodland ecosystem, owls feed on both voles and mice.

Sketch a line on the graph (Figure 1) to represent how populations of owls may change throughout the same period shown in Figure 1.

Explain why the data in Figure 1 could not be collected using a quadrat.

Figure 1 shows a British glow-worm.

Wofl~commonswiki, CC BY-SA 2.0 DE <https://creativecommons.org/licenses/by-sa/2.0/de/deed.en>, via Wikimedia Commons

Figure 1

Read the following extract before answering the questions.

Female glow-worms produce bright lights in the summer to attract males.
Glow-worm larvae are predators of slugs and snails, but adult glow-worms do not feed.
Females only have a few weeks to attract a mate and lay eggs, before the females die.

What will happen if the population of snails decreases?

Female glow-worms are found attached to grass plants in a large field.

The mean number of female glow-worms in 1 m² of the field is 5.

The field has a total area of 800 m².

Estimate the number of female glow-worms in the whole field.

(1)

A student was investigating the populations of organisms in a garden.
Figure 1 shows the estimates of the number and biomass of some of the organisms in the garden.

Hedgehogs eat slugs and earthworms.

Slug pellets were used to kill the slugs.

Explain how killing the slugs would affect the population of earthworms in this garden.

(2)

(iii)

Describe a method that could be used to estimate the population of slugs in the garden.

(3)

Figure 1 shows an area of nettle plants.

FullEdit, CC BY-SA 4.0 <https://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons

Figure 1

Grass does not grow among the nettles.

Explain why grass does not grow where there are nettles.

Devise a method a scientist could use to investigate how temperature affects nettle growth.

The population of native white-clawed crayfish in English rivers is decreasing due to an increasing population of American imported signal crayfish.

Figure 1 shows a white-clawed crayfish.

Figure 1

(1)

American imported signal crayfish may eat white-clawed crayfish.

Explain one other reason why the increasing population of American imported signal crayfish may have caused the decrease in white-clawed crayfish.

(2)

The Environment Agency is developing methods of increasing the population of white-clawed crayfish in English rivers.

Which term describes these methods?

White-clawed crayfish cannot survive in rivers with a low concentration of oxygen.

Explain how eutrophication can cause the population of white-clawed crayfish to decrease.

(3)

Biodiversity is essential for the stability of ecosystems globally.

Explain why this is.

Campanula rotundifolia is a common species of plant found in grasslands in the UK, also known as the harebell. In recent years, number of harebell plants have been declining steadily across England.

A group of scientists decided to carry out an ecological study into the population of harebell found in a region of Wales.

Describe a method that could be used to estimate the size of a harebell population in a meadow in a region of Wales.

In another ecological study, scientists were investigating the effect of road pollution on the distribution of harebells.

Their hypothesis was as follows:

'The abundance of Campanula rotundifolia decreases as the distance from the road decreases'

Suggest how the method used to collect this data would be different from the investigation carried out in part (b).

Figure 1 shows the data collected in the study.

Plot a graph on the axis below to show the data collected in the investigation (Figure 1).

Ecologists carried out a study into the effect of soil moisture level on the distribution of certain species of wildflower in a large meadow.

Figure 1 shows the meadow from the study, bounded by a river to the north and east and by farmland to the west and south.

The meadow slopes down to the river, with the south end of the meadow elevated approximately 10 metres above the north end. 

Figure 1

A quadrat study was carried out to determine the abundance and distribution of wildflowers in the meadow, alongside a measurement of soil moisture levels using a soil moisture probe of the sort shown in Figure 2.

Samples were analysed in four areas of the meadow, W, X, Y and Z as shown in Figure 1.

Figure 2

The data found by the ecologists is shown in Table 1.

Table 1

Suggest reasons for the differing soil moisture levels at W, X, Y and Z.

Using the data in Table 1, assign a rank order 1 - 6 to each of the wildflower species named below in ascending order of being adapted to living in dry conditions. 

Suggest why the answer you gave in part (b) may not be the most accurate rank order of adaptation to dry conditions. 

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.

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.

Explain which field has the greater biodiversity.