How is metabolic rate measured, and how do conformers and regulators cope with their environment?
Metabolic rate and the ways it is measured, the relationship between metabolic rate and body structures in different animal groups, and the contrast between conformers and regulators in how they maintain their internal environment, including the costs and benefits of each strategy.
An SQA Higher Biology answer on metabolic rate and how it is measured, how metabolic rate relates to body structure across animal groups, and the contrast between conformers and regulators including the energy costs and benefits of each strategy.
Reviewed by: AI editorial process; not yet individually human-reviewed
Have a quick question? Jump to the Q&A page
Jump to a section
What this key area is asking
The SQA wants you to describe metabolic rate and how it is measured, explain how metabolic rate relates to the body structures of different animal groups, and contrast conformers and regulators, including the energy costs and benefits of each strategy.
Metabolic rate and how it is measured
Metabolic rate and body structure
Higher metabolic demands are matched by features that supply tissues with oxygen efficiently. The circulatory systems of vertebrate groups differ, and the trend is towards keeping oxygenated and deoxygenated blood more separate so that tissues receive fully oxygenated blood:
- Fish have a single circulation with a two-chambered heart. Blood passes through the heart once per circuit, and pressure drops after the gills.
- Amphibians and most reptiles have an incomplete double circulation with a three-chambered heart, so oxygenated and deoxygenated blood mix a little.
- Birds and mammals have a complete double circulation with a four-chambered heart, fully separating oxygenated and deoxygenated blood. This delivers oxygen efficiently at high pressure and supports the high metabolic rate needed to maintain a constant body temperature.
Conformers and regulators
The two strategies have different costs and benefits:
- Conformers use little energy to control their internal state, but they depend on a narrow range of stable environments and may become less active when conditions change. Many use behaviour (such as moving to shade or basking in the sun) to cope, which is cheaper than physiological regulation.
- Regulators use more energy maintaining their internal environment, but this lets them stay active across a wider range of conditions and occupy more ecological niches. For example, a mammal can stay active in a cold climate where a conformer would become sluggish.
Regulation depends on negative feedback control, where a change is detected by a receptor, information is sent to a control centre, and an effector triggers a response that reverses the change back towards the norm.
Examples in context
Example 1. The desert lizard as a conformer. A lizard's body temperature largely follows the temperature of its surroundings, so it is a conformer for temperature. To cope, it uses behaviour: it basks on warm rocks in the morning to raise its temperature and moves into shade or burrows when it is too hot. This costs almost no energy compared with internal regulation, but it ties the lizard to environments where it can find suitable conditions.
Example 2. Mammals as regulators in cold climates. An Arctic fox keeps its core body temperature near 38 degrees Celsius even when the air is far below freezing. Its high metabolic rate, supported by a four-chambered heart and complete double circulation, generates heat, while thick fur reduces heat loss. Maintaining this constant internal temperature costs a great deal of energy, but it lets the fox stay active and hunt all year round in a habitat that would force a conformer into dormancy.
Try this
Q1. State three ways metabolic rate can be measured. [1 mark]
- Cue. Oxygen consumption, carbon dioxide production, or heat (energy) released.
Q2. Give one advantage and one disadvantage of being a regulator. [2 marks]
- Cue. Advantage: stays active over a wide range of conditions and more niches. Disadvantage: it costs energy to maintain the internal environment.
Exam-style practice questions
Practice questions written in the style of SQA exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
SQA Higher 20194 marksExplain the difference between a conformer and a regulator, and describe the costs and benefits of each strategy.Show worked answer →
A 4-mark answer needs both definitions plus a cost and benefit for each.
A conformer has an internal environment that changes along with the external environment. This costs little energy, which is an advantage, but it limits the conformer to a narrow range of fairly stable environments and it may become less active when conditions change.
A regulator keeps its internal environment relatively constant despite external change, using homeostasis. This costs energy, which is a disadvantage, but it allows the regulator to stay active across a wide range of conditions and to occupy more ecological niches.
Markers reward the two definitions, plus a cost and a benefit for each strategy.
SQA Higher 20224 marksAn animal at rest consumes 18 cubic centimetres of oxygen per minute. Each cubic centimetre of oxygen releases 20 joules of energy. Calculate the animal's metabolic rate in joules per hour, and state two other ways metabolic rate could be measured.Show worked answer →
This is a metabolic rate calculation.
Step 1. Work out the energy released per minute: joules per minute.
Step 2. Convert to per hour by multiplying by 60: joules per hour.
Step 3. Metabolic rate could instead be measured by the rate of carbon dioxide production, or by the amount of heat (energy) released directly by the organism.
Markers reward the working (), the value of 21600 joules per hour, and two valid alternative measures.
Related dot points
- The stages of cellular respiration (glycolysis, the citric acid cycle and the electron transport chain), the role of ATP, NAD and dehydrogenase enzymes, the net energy yield of glycolysis, and the use of alternative respiratory substrates and fermentation in the absence of oxygen.
An SQA Higher Biology answer on cellular respiration, covering glycolysis, the citric acid cycle and the electron transport chain, the role of ATP, NAD and dehydrogenase enzymes, the net ATP yield of glycolysis, and fermentation when oxygen is absent.
- Metabolic pathways as integrated networks of enzyme-controlled reactions, anabolic and catabolic reactions, the control of pathways by enzymes, induced fit, competitive and non-competitive inhibition, feedback inhibition, and the role of membranes in metabolism.
An SQA Higher Biology answer on metabolic pathways and their control, covering anabolic and catabolic reactions, enzyme action and induced fit, competitive and non-competitive inhibition, feedback inhibition, and the role of membranes in metabolism.
- Survival strategies that maintain metabolism when conditions are adverse, including dormancy (predictive and consequential), hibernation, aestivation and daily torpor, and migration as a way of avoiding unfavourable conditions, together with how migration is studied.
An SQA Higher Biology answer on surviving adverse conditions, covering predictive and consequential dormancy, hibernation, aestivation and daily torpor, and migration as a way of avoiding unfavourable conditions including how migratory behaviour is studied.
- The use of microorganisms in research and industry, their diverse metabolism and ability to use a range of substrates, growth in culture media and the phases of a growth curve, the production of primary and secondary metabolites, and the control of growth conditions in fermenters.
An SQA Higher Biology answer on the environmental control of metabolism in microorganisms, covering their use in research and industry, growth requirements and the phases of a growth curve, primary and secondary metabolites, and the control of conditions in fermenters.
- Improving wild strains of microorganisms by mutagenesis and selective breeding, recombinant DNA technology and the use of plasmids and artificial chromosomes as vectors, the role of restriction endonucleases, ligase and marker genes, and the need for regulatory sequences and import of useful genes.
An SQA Higher Biology answer on the genetic control of metabolism, covering the improvement of microbial strains by mutagenesis and selective breeding, recombinant DNA technology, plasmid and artificial chromosome vectors, restriction endonucleases, ligase and marker genes.
Sources & how we know this
- SQA Higher Biology Course Specification — SQA (2018)