Higher Biology
Unit 2: Metabolism and Survival
(2.3) Metabolic Rate (2.4) Metabolism in Conformers and Regulators
Higher Biology Unit 2 Pupil Course Notes
Unit 2: Metabolism and Survival
Sub-Topic (2.3) Metabolic rate (2.4) Metabolism in Conformers and Regulators
On completion of this subtopic I will be able to
State that metabolic rate is the quantity of energy consumed by an organism per unit of time. Metabolic rate can be measured as oxygen consumption per of unit time, carbon dioxide production per unit of time or energy production as heat per unit of time. State that different types of organisms have different metabolic rates. Compare the metabolic rate of different organisms. Animals have various physiological adaptations to deliver oxygen to cells. High metabolic rates require efficient delivery of oxygen to cells. Describe the structure and circulation of the fish heart and lung structure. Describe the structure and circulation of the amphibian and reptile heart and structure of lungs Describe the structure and circulation in the mammalian and bird heart and structure of the lungs Describe physiological adaptations that animals have to survive in low oxygen niches.
The maximum uptake of oxygen (VO2 max) can be used as a measure of human fitness. Conformers’ internal environment is dependent on external factors such as temperature, salinity and pH. Conformers may have low metabolic costs and narrow ecological niches. Describe behavioural responses in conformers to maintain optimum metabolic rate. Regulators can control their internal environment, increasing their range of ecological niches. Regulation requires energy to achieve homeostasis. Describe the process of negative feedback control and thermoregulation in mammals including the role of the hypothalamus, nerves, effectors and skin. State the importance of regulating temperature for optimal enzyme controlled reaction rates and diffusion rates to maintain metabolism.
Duncanrig Secondary School LS 2015 page 1 of 22
Higher Biology Unit 2 Pupil Course Notes
Multicellular Organisms Sub-Topic 2.6(b)
Animal Transport & Exchange Systems
Prior Learning
In mammals a transport system is required to deliver essential substances to cells and
take waste materials away from cells In mammals, nutrients, oxygen and carbon dioxide are transported in the blood The heart is made up of four chambers, the right and left atria and the right and left ventricles Valves which prevent the backflow of blood are located between the atria and ventricles and also found in the pulmonary artery and aorta
Blood vessels associated with the heart include the aorta, vena cava, pulmonary
arteries, pulmonary veins and coronary arteries
Deoxygenated blood comes back to the heart from circulating around the body and flows into the vena cava, then flows through the right atrium and right ventricle before leaving the heart through the pulmonary artery to go to the lungs In the lungs the blood becomes oxygenated and returns to the heart via the pulmonary vein, then flows through the left atrium and left ventricle leaving the heart through the aorta to circulate around the body
Duncanrig Secondary School LS 2015 page 2 of 22
Higher Biology Unit 2 Pupil Course Notes
(2.3) Metabolic rate
Metabolism is the set of chemical reactions that happen in living organisms to sustain life.
The quantity of energy consumed by an organism per unit of time is called its metabolic rate.
Energy is generated by cells during aerobic respiration:
glucose + oxygen carbon dioxide + water + ENERGY
Metabolic rate can be measured as
The rate of energy production as heat The rate at which an organism consumes oxygen The rate at which an organism produces carbon dioxide
Metabolic rate can be measured using calorimeters
A calorimeter is a well insulated container containing a pipe through which water flows. Heat generated by the organism causes a rise in temperature of the water in the pipe. Measuring the temperature of the water entering and leaving the calorimeter for a given period of time, allows the calculation of the organism’s metabolic rate from the data collected.
Duncanrig Secondary School LS 2015 page 3 of 22
Higher Biology Unit 2 Pupil Course Notes
Indirect calorimetry measures the respiration rate in an organism by measuring O2 uptake or CO2 production.
Label the diagram. Use the space below to explain how a respirometer
works.
Different types of organisms have different metabolic rates.
Use Torrance text book, chapter 10, to find out the metabolic rates of various animals at rest.
Volume of oxygen consumed
Animal animal group (mm3g-1 body mass h-1)
The oxygen consumption is then used to calculate the basal metabolic rate (BMR). This is a measure of the energy consumed by an organism when at rest. Any increase in activity by the organism will use more energy in addition to the BMR.
Duncanrig Secondary School LS 2015 page 4 of 22
Higher Biology Unit 2 Pupil Course Notes
The energy needed by an organism can be broken down into 3 main parts
1. BMR 2. Physical activity- the more activity, the higher the energy cost 3. The cost of digesting and processing food
Oxygen delivery
An organism’s metabolic rate will increase to meet an increasing demand for energy.
Its rate of aerobic respiration will increase and consumption of oxygen will increase as it is important that oxygen rapidly reaches all body cells.
Aerobic organisms with high metabolic rates have efficient transport systems capable of delivering large supplies of oxygen to respiring cells.
Each vertebrate group has specific adaptations of the circulatory system to cope with their own aerobic demands and metabolic rates.
Vertebrates use closed circulation systems – a muscular heart pumps blood through a closed system of blood vessels.
Duncanrig Secondary School LS 2015 page 5 of 22
Higher Biology Unit 2 Pupil Course Notes
(1) Circulatory systems
Fish
Circulation Blood travels though a two chamber pump in a and blood single circuit from the heart to the gills and then on pressure around the body. Since blood pressure decreases as the blood passes through the gills, body tissues receive blood under low pressure. Blood flow is aided by body movements during swimming. Heart Atrium A single atrium receives deoxygenated blood from the body. Ventricle A single ventricle pumps deoxygenated blood to the gills.
Using information from the power point presentation: Limitations of this system are: ______
Amphibians and Reptiles
Circulation Three chamber, double cycle pump with one circulation and blood loop pumping to the lungs and skin and another loop pumping pressure to the body. Although blood loses pressure as it passes through the capillary beds, in the lungs and skin, the pressure increases again as it passes through the heart for a second time. Heart Atria A right atrium receives deoxygenated blood from the body. A left atrium receives oxygenated blood from the lungs and skin. Ventricle A single ventricle receives blood from both atria. Mixing of oxygenated and deoxygenated blood can take place but is reduced by internal ridges that divert deoxygenated blood from the right atrium towards the lungs and skin and oxygenated blood from the left atrium towards the rest of the body.
Using information from the power point presentation: Limitations of this system are: ______
Duncanrig Secondary School LS 2015 page 6 of 22
Higher Biology Unit 2 Pupil Course Notes
Mammals and Birds
Circulation and Four chambered double cycle pump. There is a blood pressure double circuit with the right side of the heart pumping blood to the lungs and the left side pumping blood to the body. Pumping blood through the heart after it has been through the lungs ensures that the body tissues receive blood under high pressure. Heart Atrium A right atrium receives deoxygenated blood from the body. A left atrium receives oxygenated blood from the lungs. Ventricles A right ventricle pumps deoxygenated blood from the right atrium to the lungs.
A left ventricle pumps oxygenated blood to the body. By having two ventricles, mixing of the oxygenated and deoxygenated blood is prevented. This is important to maintain the high metabolic rate required in these animals.
Why is this kind of system essential in warm blooded animals? ______
Duncanrig Secondary School LS 2015 page 7 of 22
Higher Biology Unit 2 Pupil Course Notes
Oxygen Delivery
(2) Lung Systems
Amphibians
The lungs in amphibians are small balloon-like thin walled sacs. The surface area available for diffusion is low as it is limited only to the outer surface area. This means that the amount of oxygen obtained through the amphibian lung is small. To ensure they have enough oxygen to support their metabolic rate amphibians exchange gases through their skin and mouth cavity and only use their lungs during vigorous activity.
Reptiles
Reptiles are more active than amphibians and have a greater metabolic oxygen demand. They have a basic bronchiole system with alveoli clustered at the ends, increasing surface area over which diffusion can take place.
Mammals
Mammals have an even greater oxygen demand with the evolution of regulated temperature. The bronchioles have many branches leading to many clusters of alveoli which provide a large surface area for diffusion. This enables large quantities of oxygen needed for aerobic respiration to pass into the bloodstream and be transported to metabolising tissues and organs. Breathing movements of the lungs and diaphragm bring about the emptying and filling of the lungs.
Duncanrig Secondary School LS 2015 page 8 of 22
Higher Biology Unit 2 Pupil Course Notes
Birds
Birds are the most active of the vertebrate groups and need more oxygen relative to their body size compared to all other vertebrates. In addition to their lungs they possess several large air sacs that keep air flowing through the lungs acting like bellows.
When a bird inhales air, its posterior air sacs fill with fresh air while its anterior air sacs become filled with stale air from the lungs. When the bird exhales, the fresh air passes from the posterior air sacs to the lungs and the stale air passes from the anterior sacs to the external environment. Air is forced in one direction preventing the mixing of inhaled and exhaled air and maximising the oxygen content of the air and allows them to maintain a very high metabolic rate.
Physiological Adaptations of animals for low oxygen niches
The human body functions best at sea level where the concentration of oxygen in the air is around 20%. Read Torrance text book, chapter 10, then write a statement describing the how the human body responds when a person moves to a high altitude and why this response is important. ______
Duncanrig Secondary School LS 2015 page 9 of 22
Higher Biology Unit 2 Pupil Course Notes
Case Study
Animal Adaptations to Survive Low Oxygen Niches.
You are going to research and write an article on organisms’ adaptations to survive in low oxygen niches. You will take on the role of an editor of a science magazine who is to write an article about how vertebrates adapt to survive in low oxygen niches. You must include information that explains the adaptations and any underlying biology.
Oxygen Levels Over Geological Timescale.
The amount of oxygen in Earth’s atmosphere is determined by a wide range of physical and biological processes. The level of oxygen in the atmosphere has fluctuated significantly until relatively recently in geological time. The oxygen available for metabolism directly affects the energy available in an organism and so affects the size of the organism that can be sustained. Fossil records show that when oxygen levels rose to current levels of around 20% many different groups of animals ‘suddenly’ increased in size as only then was the oxygen level rich enough to maintain their metabolism. However, as evolution continued eventually body size of terrestrial animals reached a maximum determined by other limiting factors.
Read Torrance chapter 10 to find out what other factors might limit the size of a terrestrial animal. Write a note about what you found out in the space below ______
Timescale Oxygen level Organisms (years ago) ~ 3.5 -2.45 billion Virtually none Very little present, simple archaea forms.
2.45-0.85 billion O2 produced but absorbed Micro-organisms. Evolution of into oxygen sinks cyanobacteria which can photosynthesise and produce oxygen 850 -300 million Free oxygen in Multicellular organisms evolve such as atmosphere (up to 35%) invertebrates. 300 million - present Current levels ~20% Large biodiversity of organisms now present. Biggest organisms are large mammals.
Duncanrig Secondary School LS 2015 page 10 of 22
Higher Biology Unit 2 Pupil Course Notes
Fitness and Maximum Oxygen Uptake
VO2 max is the volume of oxygen used per kilogram of body mass per minute (ml/kg/min) while exercising at maximum capacity.
VO2 max can be used to measure fitness in humans.
The greater the VO2 max the greater the fitness of a person
Duncanrig Secondary School LS 2015 page 11 of 22
Higher Biology Unit 2 Pupil Course Notes
(2.4) Metabolism in Conformers and Regulators
The ability of an organism to maintain its metabolic rate is affected by external abiotic factors such as temperature, salinity and pH. Animals can be divided into two groups: conformers and regulators.
(1) Conformers
Conformers are animals that allow their internal body conditions for a particular factor to vary with the external environment.
The advantage to this way of life is that the animal’s metabolic costs are low as it does not need to use up energy maintaining a stable internal environment. However, the disadvantage is that they are restricted to a narrow range of ecological niches and are less adaptable to environmental change. Such organisms may employ behaviour responses to maintain their optimum metabolic rates.
Osmoconformers
Marine invertebrates such crabs, shrimp and jellyfish are osmoconformers. Their body fluids are isotonic with their environment. The solutes in their body tissues are equal to those in their surroundings.
Thermoconformers
Lizards are thermoconformers. Their body temperature varies with the temperature of the environment.
Read Torrance text book chapter 10 and from your findings describe how lizards use a behavioural response to maintain their optimal metabolic rate.
Duncanrig Secondary School LS 2015 page 12 of 22
Higher Biology Unit 2 Pupil Course Notes
(2) Regulators
Regulators are animals that use physiological mechanisms (homeostasis) to maintain their internal body conditions at optimal levels.
The advantage of this way of life is that it allows the organism to increase the range of possible ecological niches. However, the disadvantage is that it is costly in terms of energy requirements as energy is consumed to maintain the physiological mechanisms at a steady state.
On the graph below draw a line that would represent the internal environment of i) a rigid regulator ii) a rigid conformer.
Duncanrig Secondary School LS 2015 page 13 of 22
Higher Biology Unit 2 Pupil Course Notes
Summarise the key features of conformers and regulators in the table below.
Advantages Disadvantages Mechanisms used to control the internal environment
Conformers
Regulators
What is our internal environment?
Complete the diagram below to show 3 aspects of the human internal environment that need to be maintained at a steady state.
internal
environment
Duncanrig Secondary School LS 2015 page 14 of 22
Higher Biology Unit 2 Pupil Course Notes
Physiological Homeostasis
Physiological homeostasis is the maintenance of the body’s internal environment within certain tolerable limits despite changes in the body’s external environment. To allow homeostasis there must be a corrective mechanism that acts when any variable of the internal environment changes too much. Such a mechanism uses negative feedback.
Aspects of the internal environment are monitored by receptor cells in the monitoring centres of the body. Deviations away from the normal level (called the norm or set point) are detected by receptor cells. These send out nerve or hormonal messages which are received by effectors.
The effectors bring about a response which counteracts the original deviation away from the norm to return the system back to its set point.
Thermoregulation
Animals vary in their ability to regulate their temperature. The process is best developed in birds and mammals which are endothermic. Endotherms rely entirely on heat which is produced internally as a by-product of their metabolism.
Endotherms regulate body temperature within narrow limits, by balancing heat production and heat loss. They are able to maintain their body temperature at a relatively constant level independent of the temperature of the external environment.
Ectotherms also produce metabolic heat but they are less able to retain it and require external heat from the sun. They are unable to regulate their body temperatures by physiological means. Ectotherms’ body temperature may fluctuate considerably depending on the environmental temperature.
Duncanrig Secondary School LS 2015 page 15 of 22
Higher Biology Unit 2 Pupil Course Notes
The Importance of Temperature Regulation
Maintaining an optimum temperature within the body is essential to ensure that diffusion and all enzyme controlled reactions are working at an efficient metabolic rate.
When body temperature is below the optimum temperature for enzyme function metabolism is slow. Above the optimum, enzymes start to denature; the metabolism slows down and eventually stops.
Temperature regulation is only possible if there is some sort of ‘thermostat’ which is activated if the temperature varies from a fixed point (the norm).
The hypothalamus is the body’s temperature monitoring centre. It acts like a thermostat and is sensitive to nerve impulses that it receives from heat and cold receptors (thermoreceptors) in the skin. These convey information to it about the surface temperature of the body. In addition receptors (thermoreceptors) in the hypothalamus detect changes in blood temperature which reflect changes in core body temperature.
The thermoregulatory centre of the hypothalamus responds to this information by sending nerve impulses to effector organs in the skin and body muscles. The effectors bring about a response to return the temperature back to normal.
Duncanrig Secondary School LS 2015 page 16 of 22
Higher Biology Unit 2 Pupil Course Notes
Warming-up Mechanisms (Too cold!)
Vasoconstriction (narrowing) of the arterioles in the skin to reduce blood flow away from the skin and so reduce heat-loss by radiation and conduction from the blood.
Shivering to increase muscle activity and generate heat.
Contraction of hair erector muscles causing the hairs to be raised, so trapping a layer of insulating air to reduce heat loss.
Little sweat is produced.
Increased metabolic rate to produce more heat.
Duncanrig Secondary School LS 2015 page 17 of 22
Higher Biology Unit 2 Pupil Course Notes
Cooling-down Mechanisms (Too hot!)
Vasodilation (widening) of the blood vessels in the skin to increase blood flow to the skin and so promote heat-loss by radiation and conduction from the blood.
No shivering.
Hair erector muscles are relaxed allowing body hair to lie flat against the skin minimising the insulating effect.
Increased activity of the sweat glands to release sweat which evaporates using heat from the body to do so, and so helps to lower body temperature.
Decreased metabolic rate to reduce heat production.
Duncanrig Secondary School LS 2015 page 18 of 22
Higher Biology Unit 2 Pupil Course Notes
Negative Feedback in Temperature Regulation
Using the information from the power point presentation complete the diagram below to summarise negative feedback mechanism in temperature regulation.
Receptors
Type of Message
Effector
Corrective Heating up Cooling down mechanisms mechanisms Responses
Result
Answer the following questions
Duncanrig Secondary School LS 2015 page 19 of 22
Higher Biology Unit 2 Pupil Course Notes
1. Give the term used for animals which can control their internal temperature by negative feedback. ______
2. State the two ways that the hypothalamus obtains information about the temperature of the body. ______
3. Name two effectors to which the hypothalamus sends nerve impulses in order for them to respond and return body temperature back to normal. ______
4. Why is body temperature important in carrying out metabolic processes? ______
Duncanrig Secondary School LS 2015 page 20 of 22
Higher Biology Unit 2 Pupil Course Notes
(2.3) Metabolic Rate (2.4) Metabolism in Conformers and Regulators
Complete: Column 1 before your Unit assessment Column 2 before your Prelim Column 3 before your May exam
1 2 3 State that metabolic rate is the quantity of energy consumed by an organism per unit of time. Metabolic rate can be measured as oxygen consumption per of unit time, carbon dioxide production per unit of time or energy production as heat per unit of time. State that different types of organisms have different metabolic rates.
Compare the metabolic rate of different organisms.
Animals have various physiological adaptations to deliver oxygen to cells.
High metabolic rates require efficient delivery of oxygen to cells.
Describe the structure and circulation of the fish heart and lung structure.
Describe the structure and circulation of the amphibian and reptile heart and structure of the lungs. Describe the structure and circulation in the mammalian and bird heart and structure of the lungs. Describe physiological adaptations that animals have to survive in low oxygen niches. The maximum uptake of oxygen (VO2 max) can be used as a measure of human fitness Conformers’ internal environment is dependent on external factors such as temperature, salinity and pH. Conformers may have low metabolic costs and narrow ecological niches.
Describe behavioural responses in conformers to maintain optimum metabolic rate. Regulators can control their internal environment, increasing their range of ecological niches. Regulation requires energy to achieve homeostasis. Describe the process of negative feedback control and thermoregulation in mammals including the role of the hypothalamus, nerves, effectors and skin. State the importance of regulating temperature for optimal enzyme controlled reactions rates and diffusion rates to maintain metabolism. Duncanrig Secondary School LS 2015 page 21 of 22