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
Duncanrig Secondary School LS 2015 page 1 of 22
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.
Higher Biology Unit 2 Pupil Course Notes
Duncanrig Secondary School LS 2015 page 2 of 22
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
Higher Biology Unit 2 Pupil Course Notes
Duncanrig Secondary School LS 2015 page 3 of 22
(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.
Higher Biology Unit 2 Pupil Course Notes
Duncanrig Secondary School LS 2015 page 4 of 22
Indirect calorimetry measures the respiration rate in an organism by
measuring O2 uptake or CO2 production.
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.
Animal
animal group
Volume of oxygen consumed
(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.
Label the diagram.
Use the space below to explain how a respirometer
works.
Higher Biology Unit 2 Pupil Course Notes
Duncanrig Secondary School LS 2015 page 5 of 22
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.
Higher Biology Unit 2 Pupil Course Notes
Duncanrig Secondary School LS 2015 page 6 of 22
(1) Circulatory systems
Fish
Using information from the power point presentation: Limitations
of this system are:
_____________________________________________________
_____________________________________________________
Amphibians and Reptiles
Using information from the power point presentation: Limitations of this system are:
____________________________________________________________________
____________________________________________________________________
____________________________________________________________________
Circulation and blood pressure
Blood travels though a two chamber pump in a single circuit from the heart to the gills and then on 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.
Circulation and blood pressure
Three chamber, double cycle pump with one circulation loop pumping to the lungs and skin and another loop pumping 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.
Higher Biology Unit 2 Pupil Course Notes
Duncanrig Secondary School LS 2015 page 7 of 22
Mammals and Birds
Why is this kind of system essential in warm blooded animals?
__________________________________________________________________
__________________________________________________________________
__________________________________________________________________
Circulation and blood pressure
Four chambered double cycle pump. There is a 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.
Higher Biology Unit 2 Pupil Course Notes
Duncanrig Secondary School LS 2015 page 8 of 22
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.
Higher Biology Unit 2 Pupil Course Notes
Duncanrig Secondary School LS 2015 page 9 of 22
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.
________________________________________________________
________________________________________________________
Higher Biology Unit 2 Pupil Course Notes
Duncanrig Secondary School LS 2015 page 10 of 22
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
(years ago)
Oxygen level Organisms
~ 3.5 -2.45 billion Virtually none Very little present, simple archaea forms.
2.45-0.85 billion O2 produced but absorbed
into oxygen sinks
Micro-organisms. Evolution of
cyanobacteria which can photosynthesise
and produce oxygen
850 -300 million Free oxygen in
atmosphere (up to 35%)
Multicellular organisms evolve such as
invertebrates.
300 million - present Current levels ~20% Large biodiversity of organisms now
present. Biggest organisms are large
mammals.
Higher Biology Unit 2 Pupil Course Notes
Duncanrig Secondary School LS 2015 page 11 of 22
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
Higher Biology Unit 2 Pupil Course Notes
Duncanrig Secondary School LS 2015 page 12 of 22
(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.
Higher Biology Unit 2 Pupil Course Notes
Duncanrig Secondary School LS 2015 page 13 of 22
(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.
Higher Biology Unit 2 Pupil Course Notes
Duncanrig Secondary School LS 2015 page 14 of 22
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
Higher Biology Unit 2 Pupil Course Notes
Duncanrig Secondary School LS 2015 page 15 of 22
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.
Higher Biology Unit 2 Pupil Course Notes
Duncanrig Secondary School LS 2015 page 16 of 22
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.
Higher Biology Unit 2 Pupil Course Notes
Duncanrig Secondary School LS 2015 page 17 of 22
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.
Higher Biology Unit 2 Pupil Course Notes
Duncanrig Secondary School LS 2015 page 18 of 22
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.
Higher Biology Unit 2 Pupil Course Notes
Duncanrig Secondary School LS 2015 page 19 of 22
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.
Answer the following questions
Receptors
Type of Message
Effector
Corrective
Responses
Result
Heating up
mechanisms
Cooling down
mechanisms
Higher Biology Unit 2 Pupil Course Notes
Duncanrig Secondary School LS 2015 page 20 of 22
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?
______________________________________________________
______________________________________________________
Higher Biology Unit 2 Pupil Course Notes
Duncanrig Secondary School LS 2015 page 21 of 22
(2.3) Metabolic Rate (2.4) Metabolism in Conformers and Regulators
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.
Complete:
Column 1 before your Unit assessment
Column 2 before your Prelim
Column 3 before your May exam