Adaptations, Interdependence & Competition (AQA GCSE Biology: Combined Science)

Limpets are a type of aquatic snail found along coastlines in the UK.

They can attach themselves to rocky surfaces using their muscular foot, as shown in Figure 1.

Figure 1

Suggest why it is essential that limpets can attach themselves to surfaces like a rock by exerting a large force. 

A group of scientists investigated the distribution of different species of limpet over various parts of a rocky shore. 

The high tide water mark is the highest level that seawater reaches along a shoreline. 

Each bar in Table 1 represents where limpets were found along the shore. 

Table 1

Identify which two species of limpet would be most likely to be in competition with each other. Give a reason for your choice. 

L. digitalis cannot survive higher up the shore, whereas L. paradigitalis can.

Suggest two reasons why L. digitalis cannot survive higher up the shore.

Like fish, limpets exchange oxygen and carbon dioxide from water drawn through their gills. Although some species of limpet take in oxygen directly from the air, all limpets should avoid drying out.

Limpet species found near the high-tide water mark tend to have a more domed shell, whereas those found nearer the low-tide water mark tend to have wider, flatter shells. 

Suggest, with reasons, a possible explanation for this. 

Figure 2 shows an example of a food web which includes limpets.

Figure 2

Use organisms from the food web in Figure 2 to explain what is meant by the term, 'interdependence'.

A student wanted to investigate how different abiotic factors affect the growth and distribution of daisies in the field behind his school.

The distribution of daisies in the field could be affected by environmental factors such as sunlight. 

Give three other abiotic factors that might affect the distribution of daisies in a field. 

Explain how the amount of sunlight could affect the distribution of daisies in the field.

Desert animals are adapted to survive in very hot, dry conditions. 

Many are nocturnal (only active at night) or crepuscular (only active at dawn and dusk).

Some animals do not sweat, or sweat only after a significant increase in body temperature. 

Others have adapted in more extreme ways, with organs such as the heart and liver shrinking at the height of the dry season, reducing the energy demand of these organisms. 

Suggest how some of the adaptations described above help desert animals survive in hot, dry conditions. 

Figure 3 below shows an arctic fox (left) and a desert fox (right).

Figure 3

Animals living in cold climates tend to have different body shapes to those living in hotter climates.

Identify a difference in body shape between these two types of fox and explain the difference based on the habitat that each fox occupies.  

It has been observed that there are far fewer living species at higher latitudes, closer to the poles, than there are living species a lower latitudes, closer to the equator. 

The time taken for evolution to occur at higher latitudes is also considered to be much shorter than at lower latitudes.

Suggest explanations for these two observations. 

The Norris Geyser Basin in Yellowstone National Park is a pool of boiling, acidic water. 

A number of species of bacteria have been found living in the geyser, including Thermus aquaticus.

What term is used to describe organisms that can survive in severe conditions such as the boiling, acidic water of the Norris Geyser Basin?

Taq polymerase is a thermostable enzyme found in Thermus aquaticus in the Norris Geyser Basin.

Suggest an explanation why most microorganisms cannot survive at high temperatures such as those found in the Norris Geyser Basin, but Thermus aquaticus can survive. 

In the 18th Century, an English settler in Australia released a number of rabbits into the wild for hunting purposes. 

Rabbits are not native to Australia. 

There are now millions of rabbits in Australia, and they are thought to be responsible for the loss of a number of native species. 

In the 1990s, a number of lionfish escaped into the Atlantic Ocean from an aquarium; their population in the Atlantic now numbers in the thousands. 

Suggest explanations for the large increases in population size of both species described above. 

Define the following two terms:

(i) Adaptation

[1 Mark]

(ii) Ecosystem

[1 Mark]

Desert plants have many adaptations for surviving in desert areas.

Some plants have a dual-root system, with a small number of deep, bulbous roots and a large number of shallow roots spread out over a wide area.

Suggest how the dual-root system allows desert plants to survive.

Suggest and explain three possible adaptations that the leaves of desert plants may have. 

Extremophiles are (most commonly) microorganisms; these are adapted to live in extreme chemical or geophysical conditions. 

In some cases, scientists attempting to discover the genetic composition of extremophiles have struggled to break open their cells in an attempt to isolate their DNA.

Suggest why it has been difficult to access the DNA of certain extremophiles for research purposes.

Figure 1 is a sketch graph showing the effect of increasing temperature on the activity of a typical human enzyme.

Figure 1

The thermophilic microorganism Methanopyrus kandleri thrives at temperatures around 120°C

Sketch a line on the graph in Figure 1 to show the effect of increasing temperature on the activity of an enzyme from Methanopyrus kandleri.

Certain thermophilic bacteria are known as obligate thermophiles.

Choose A - D which best defines the term 'obligate thermophiles'.

Thermophilic organisms have been used in the following processes

• • The manufacturing of biological washing powder
  • The degradation of pollutants
  • Bioremediation of oil-contaminated soil in the desert
  • Removal of heavy metals in the soil
  • The conversion of biomass to biofuels
  • The degradation of toxic textile dyes

Explain why thermophilic bacteria are chosen for these roles over bacteria that are adapted for life at more moderate temperatures. 

Figure 2 shows two species of squirrel, the red squirrel (Sciurus vulgaris) and the grey squirrel (Sciurus carolinensis).

Figure 2

Grey squirrels were introduced to the UK mainland as an ornamental species in the 19^th century but have since replaced the native red squirrel as the dominant species in the UK. Red squirrels have now receded from Wales and much of England, but they remain present in the far north of England and Scotland. 

What evidence from Figure 2 shows that this is an example of interspecific competition?

Because of differences in the two species' digestive systems, grey squirrels are able to feed on 'green' (immature) acorns, whereas red squirrels require the acorns to be ripe (mature). 

Suggest how this affects competition between the two species of squirrel. 

Another factor that favours the grey squirrel is that the red squirrel is susceptible to the squirrelpox (Parapox) virus, which is carried by greys but does not affect them. 

The red squirrel's plight can be helped by a number of human interventions designed to prevent its extinction. Two of these are:

• Understanding the red and grey squirrels' genes by analysing all of its DNA
• Creating a captive breeding programme for red squirrels in partnership with zoos and wildlife organisations

Explain how each of these two measures can contribute to saving the red squirrel from extinction. 

All squirrels have a varied diet which consists of tree seeds, acorns, nuts and berries. Squirrels can be prey to owls, pine martens and stoats.

Apart from any effect on the red squirrel population, predict one effect that a decrease in the grey squirrel population will have on a woodland ecosystem. 

Researchers looking into the effects of climate change investigated the effect of changes in the amount of rainfall on the number of plant species found growing naturally in a piece of woodland.

Over a 20-year period, the overall rainfall was recorded annually, along with the number of different plant species found and identified in the test area.

The results are shown in a scatter graph in Figure 3. Each data point represents a separate year. A line of best fit has been plotted with the data. 

Figure 3

Apart from this scientific work, no human activity took place in the piece of woodland during the study.

Give two other precautions that the researchers would have taken to make sure this was a valid investigation. 

The tourist office in the area of the study in question 3a) saw the researchers' data and used it to promote the area as a venue for eco-tourism. A section of their tourist brochure is shown in Figure 4 below.

Figure 4

Evaluate the claim (circled in Figure 4) made by the tourist office. 

Referring to the data shown in Figure 3, choose the statement from A - D that could be a valid conclusion from the data in the investigation. 

For the data in Figure 4, calculate the median number of plant species found throughout the course of the investigation.

Figure 4 is reproduced below for convenience. 

Show your working. 

Figure 4 (repeated)

Figure 5 shows a coypu (Myocastor coypus), a large rodent native to South American countries. Coypus are large, semi-aquatic rodents that feed on vegetation and tree bark. 

Figure 5

Coypus were introduced into North America in the 20^th century, in order for them to be farmed for their fur. Some escaped into the wild and they have become a major nuisance species. Coypus feed on tall grasses and rushes, which are a source of food, nesting sites, and shelter for many organisms. These plants also help to stabilise sediment and soil. Coypus have caused widespread damage to the area’s food web and habitats by consuming the wetland grasses.

Explain how the introduction of coypus might have caused their population, and those of wetland grasses and the animals that live within them, to fluctuate over subsequent years. 

Apart from the availability of food, give two other biotic factors that could influence the size of the coypu population. 

Describe and explain the following phrase:

In a predator-prey relationship, their populations are always out of phase.

Figure 6 shows five instruments used commonly to measure and record abiotic factors in ecological investigations. The boxes to the right show five abiotic factors measured using these instruments.

Figure 6

Draw lines to link each instrument to the abiotic factor that it is used to measure and record.  

An important abiotic factor for aquatic ecosystems is the dissolved oxygen level (in water). A good level of dissolved oxygen allows fish and other aquatic animals to breathe successfully underwater. Figure 7 shows a dissolved oxygen meter. Its probe can be immersed to measure the level of dissolved oxygen in a body of water. 

Figure 7

Describe two conditions that will ensure that a good level of dissolved oxygen can exist in a stream. 

An oxygen meter like the one shown in 5b) was used to record oxygen levels in a river. Two points were sampled , A and B, upstream and downstream from a sewage treatment plant. The layout is shown in Figure 8.

Figure 8

The dissolved oxygen levels were measured and recorded in Table 1.

Table 1

Location	Dissolved oxygen level in mg per litre	Flow rate in cubic metres per minute
A	11.2	33
B	4.4	19

Suggest a reason for the drop in dissolved oxygen between sampling points A and B. 

Explain why turbulent river water is better for aquatic wildlife in some respects, yet worse in others. 

Compare and contrast intraspecific and interspecific competition, in a biological setting. You may choose to refer to named examples of organisms in your answer.

For lions in countries like Kenya, two male lions would fight for the right to mate with the females in that pride. The loser is driven away from the pride by the winner, and so does not get the chance to mate; he must try to find a mate in another pride. 

Explain why males fight for a mate and the genetic consequences of such conflicts.