3.1 - Energy in Ecosystems & 3.4 - Energy in Ecosystems
Name the process carried out by producers that allows energy to enter a food chain.
Photosynthesis
What name is given to species whose presence or absence provides information about pollution levels?
Indicator species
What captures light energy for photosynthesis?
Chlorophyll
Nematode worms are used to prey upon insects that damage crops. Name this method of pest control.
Biological control
What is the only source of new alleles in a population?
Mutation
Name one resource, other than water, for which plants may compete.
Light / mineral nutrients / space
Name the type of factors, such as pH, that can affect the distribution of organisms.
Abiotic factors
State the source of energy for the first stage of photosynthesis.
Light
Over time, pesticides can build up in the cells of living organisms. State the term given to this build-up.
Bioaccumulation
Name one environmental factor that can increase the rate of mutation.
Radiation / certain chemicals
Explain why competition between members of the same species is described as intraspecific.
The organisms competing belong to the same species.
Students sampled plants using a quadrat three times. Describe how they could improve the reliability of their results.
Take more quadrat samples / repeat more times.
Describe how the hydrogen required for carbon fixation is produced.
Light energy is used to split water into hydrogen and oxygen.
Describe the use that plants make of nitrates.
Nitrates are used to make amino acids/proteins, required for growth.
Give a definition of the term mutation.
A random change to genetic material.
An ecosystem receives 6,000,000 units of energy from the Sun. 95% is not used in photosynthesis. Calculate the energy captured by producers.
6,000,000 x 0.5 = 300,000 units
Name one abiotic factor, other than temperature, and describe how it could be measured.
Light intensity using a light meter / soil moisture using a moisture meter / pH using a pH meter.
Explain why temperatures above 50°C would prevent photosynthesis reactions from taking place.
Enzymes become denatured / their active sites change shape.
A crop yield increased from 35 kg to 42 kg. Calculate the percentage increase in yield.
20%
Explain why variation is important for the survival of a population.
Some individuals may be better adapted to changes in conditions, allowing them to survive and reproduce.
Explain why pyramids of energy always have the same shape.
Energy is lost at each trophic level, so less energy is available at each successive trophic level.
Describe how the reliability of quadrat sampling could be improved and explain why this makes the results more reliable.
Take more samples/repeat sampling and calculate an average, reducing the effect of anomalous results.
Describe how sugar is produced during the second stage of photosynthesis.
Hydrogen combines with carbon dioxide to produce sugar.
A crop yield increased from 35 kg to 42 kg. Calculate the percentage increase in yield.
Nitrates cause an algal bloom → light is blocked → plants/algae die → bacteria increase → bacteria use oxygen during respiration → oxygen levels fall → freshwater organisms die.
Explain how natural selection results in the evolution of a species.
Individuals with favourable alleles survive and reproduce → pass these alleles to offspring → favourable alleles increase in frequency over generations → the population evolves.