Energy and ecosystems Flashcards
When starfish feed on muscles they leave behind the empty shell. Explain how quadrats could be used to determine the percentage of mussels that have been eaten by starfish on a rocky shore. (3 marks)
- Use of random numbers
- Large number of quadrats
- Count number of dead and live mussels in unit area
The percentage of barnacles in the diet is much higher than the percentage of energy they provide. Suggest one explanation for this difference. (1 mark)
- Different size organism
- Low digestibility
The gross productivity of the plants in the field was highest in July. Use the data in the table to explain why. (2 marks)
- High temps = allows enzymes to work faster
- PHS reactions are faster = more
Give the equation that links gross productivity and net productivity (1 mark)
NPP = GPP - R
The net productivity of the plants in the field was higher in August than in July. Use the equation NPP = GPP - R and your knowledge of PHS and respiration to suggest why.(2 marks)
- Respiration slower
- LDR/ PHS less affected by temp increase
- Lower energy loss
A horse was kept in the field from March to October. During the summer months, the horse was able to eat more than it needed to meet its minimum daily requirements.
Suggest how the horse used the extra nutrients absorbed. (1 mark)
- Fat
- Used for growth
The horse’s mean energy expenditure was higher in March than it was in August. Use information in the table to suggest why. (2 marks)
- Colder in march
- Maintain body temperature
- By respiration
Keeping cattle indoors, in barns, leads to higher efficiency of energy transfer. Explain why. (1 mark)
- Less energy lost = less movement
In some countries, pigs are reared in intensive units in which the temperature is controlled. Agricultural scientists investigated the effect of temperature on pig growth and on the efficiency with which the pigs converted food to biomass.
In the investigation, the scientists used pigs of the same breed, with similar genotypes.
Explain why. (2 marks)
- Same breed so similar alleles
- Removes variables - any difference would be due to temperature.
The pigs were allowed to eat as much food as they wanted. How could this have decreased the reliability of any conclusions drawn from the investigation? (2 marks)
- Different growth rates
- Not due to temperature
A student concluded from these data that the mean growth rate of the pigs was fastest at 20 degrees.
Do you agree with this conclusion? Explain your answer. (2 marks)
- Temperature may be between 10 and 30
- Intervals are large
Pigs can survive at temperatures above 35 degrees. Use the data to suggest why scientists did not carry out any investigations at temperatures higher than 35 degrees. 2 marks
- Growth rate decreasing
- Wastes time
The efficiency of conversion of food to biomass is lower at 0 degrees than it is at 20 degrees. Suggest an explanation for the lower efficiency. ( 2 marks)
- Temperature increases more heat will be wasted
- From respiration
A farmer saw these results and concluded that he should replace his pigs’ usual food with food B.
Evaluate this conclusion. (4 marks)
- Food B produces greater mass than control
- Overlap of error bars for B and A
- Experiment on ran for 10 days
- No information about cost
Residual food intake (RFI) is the difference between the amount of food an animal actually eats and its expected food intake based on its size and growth rate. Scientists have selectively bred cattle for low RFI.
Explain the advantage to farmers of having cattle with a low RFI (2 marks)
- Reduced cost
- Less feed
