Unit 2 (KA3-5)

Question 1

Metabolic rate

Answer 1

The speed of chemical reactions in an organism.

It is the quantity of energy used by the body in a given time, in kj or kcal.

Measured by measuring oxygen consumption, or production of carbon dioxide or heat.

Question 2

Calorimeter

Answer 2

Used to measure the heat produced by an organism.

The organism is placed in a well insulated container, and the temperature difference between water flowing in and out is measured.

Question 3

Respirometer

Answer 3

Used to measure oxygen uptake of an organism.

Carbon dioxide must be absorbed using soda lime/sodium hydroxide, so that the liquid moves along the scale.

Question 4

Oxygen/carbon dioxide probes

Answer 4

Used to accurately measure oxygen uptake and carbon dioxide production over time.

Linked to computers to collect data over a longer time period.

Question 5

BMR

Answer 5

Basal metabolic rate.

The minimum rate of energy release needed to maintain life.

Question 6

Surface area : volume ratio

Answer 6

As volume (or body size) increases, the SA : volume ratio of an organism decreases.

It has a smaller surface area compared to its volume.

Tiny endothermic (warm blooded) organisms with a high SA : volume ratio tend to lose heat faster, so have a higher BMR.

They need to use more energy to maintain their body temperature.

Question 7

Organisms with a low metabolic rate

Answer 7

Organisms that are sessile (don’t move), ectothermic (cold blooded) and aquatic (live in water) tend to have a lower BMR.

eg. fish, sea anemones.

Question 8

Organisms with a high metabolic rate

Answer 8

Organisms that live on land (or in the air), are endothermic (warm blooded), highly active (eg. flying) and are tiny (high SA : volume ratio) tend to have a very high BMR.

eg. mice, bats, hummingbirds.

Question 9

Circulatory system

Answer 9

Heart, blood vessels and blood.

Needed to deliver oxygen to respiring tissues.

Organisms with a high BMR need a more efficient circulatory system.

Question 10

Single circulatory system

Answer 10

The blood passes through the heart once on each circuit of the body.

The heart has 2 chambers - one atrium, one ventricle.

Blood travels to the gills at high pressure, but then loses pressure in the permeable gill capillaries, and passes to the tissues at low pressure.

It is a primitive and inefficient system, but is adequate for fish which have a low BMR.

Question 11

Double circulatory system

Answer 11

The blood passes through the heart twice on each circuit of the body.

There are 2 separate circuits - to the lungs (pulmonary circuit) and the body tissues (systemic circuit).

Blood is pumped to the lungs and body tissues at high pressure, making it a more efficient system for the delivery of oxygen.

Question 12

Incomplete double circulation

Answer 12

Found in amphibians (which have no septum, and one ventricle) and reptiles (which have a partial septum).

The oxygenated and deoxygenated blood mix in the shared ventricle, making oxygen delivery less efficient than complete double circulation.

Question 13

Septum

Answer 13

A strip of tissue separating the left and right sides of the heart.

Prevents oxygenated and deoxygenated blood from mixing.

Question 14

Complete double circulation

Answer 14

The septum completely separates the left and right sides of the heart, preventing oxygenated and deoxygenated blood from mixing.

There are 2 separate atria and 2 separate ventricles.

This is much more efficient, and ensures that oxygen is supplied to respiring tissues rapidly.

Found in organisms with a high BMR - mammals and birds.

Question 15

Abiotic factor

Answer 15

A factor in an organism’s external environment, which can fluctuate and affect its internal environment.

eg. temperature, pH, salinity

Question 16

Conformers

Answer 16

Organisms whose internal environment is dependent on abiotic factors in their external environment.

Conformers have low metabolic costs and are found in stable environments.

They are restricted to narrow ecological niches, and cannot easily adapt to changing environments.

They use behavioural responses (eg. basking in lizards) to respond to variation in their environment.

Question 17

Regulators

Answer 17

The internal environment of a regulator is independent of the external environment.

Regulators use their metabolism to control their internal environment (homeostasis).

They can exploit a much wider range of ecological niches.

Their metabolic costs are higher, as energy is expended to regulate their internal environment.

Question 18

Homeostasis

Answer 18

The maintenance of a constant internal environment, within tolerable limits.

Regulation is brought about by negative feedback control, and requires energy.

Question 19

Negative feedback control

Answer 19

Any change away from a set level is detected by receptors.

Corrective mechanisms (effectors) are set in motion to return conditions back to set level.

The corrective mechanism is then switched off.

Question 20

Thermoregulation

Answer 20

Control of body temperature

Question 21

Ectotherms

Answer 21

These are conformers, that are unable to regulate their body temperature.

They rely on behavioural thermoregulation. eg. basking in lizards.

Their body temperature depends on the external environment and they obtain most of their heat by absorbing it from their surroundings.

Ectotherms include all invertebrates and some vertebrates - fish, amphibians and reptiles.

Question 22

Endotherms

Answer 22

Organisms that can maintain their internal temperature at a relatively constant level, which is independent of the external environment.

They have a high metabolic rate, which generates heat, but uses a lot of energy.

They have an efficient metabolism, since body temperature is kept at a level for optimum enzyme activity and diffusion rates.

They can exploit a wide variety of niches and can be active at any time of day or night.

Question 23

Hypothalamus

Answer 23

The body’s temperature monitoring (thermoregulatory) centre in the brain.

Receives nerve impulses from the skin and internal organs.

Contains internal thermoreceptors which detect changes in blood temperature.

Responds to changes by sending nerve impulses to effectors.

Question 24

Effectors

Answer 24

Muscles or glands that respond to nerve impulses.

Question 25

Vasoconstriction

Answer 25

In cold conditions, arterioles leading to the surface of the skin become constricted by contraction of circular muscles.

Blood is redirected away from the surface of the skin, reducing heat loss by radiation.

Question 26

Vasodilation

Answer 26

In hot conditions, the arterioles leading to the surface of the skin dilate due to relaxation of circular muscles in the arteriole wall.

Blood is diverted towards the skin, and when hot blood flows near to cool air in the environment, heat can be lost by radiation, which cools the blood.

Question 27

Hair erector muscles

Answer 27

Every hair has its own muscle, known as a hair erector muscle.

In cold conditions, the muscle contracts, pulling the hair upright.

When many hairs stand upright, a layer of air is trapped against the skin, which acts an insulator, reducing heat loss.

This is very effective in organisms with a thick layer of fur or feathers.

Question 28

Sweat glands

Answer 28

In hot conditions, sweat is released onto the surface of the skin by sweat glands.

Heat energy from the skin is used to turn the sweat into water vapour, which has a cooling effect on the skin.

Question 29

Shivering

Answer 29

Rapid skeletal muscle contractions in cold conditions generate heat as a result of friction between muscle fibres.

Question 30

Changes in metabolic rate

Answer 30

Metabolic rate can be increased in cold conditions to generate heat, and can be decreased in hot conditions, to produce less heat.

It is controlled by the hormone thyroxine.

Question 31

Adverse

Answer 31

Unfavourable or disadvantageous

Question 32

Structural adaptation

Answer 32

A modification to body structure to improve survival chances

Question 33

Physiological adaptation

Answer 33

A change to the body’s internal processes or chemical reactions to improve survival chances, eg. dormancy.

Question 34

Behavioural adaptation

Answer 34

A change in an animal’s behaviour to improve its survival chances, eg. migration or huddling in penguins

Question 35

Dormancy

Answer 35

An organism’s metabolic rate decreases to the minimum level required to sustain life, in order to survive a period of harsh (adverse) conditions by saving energy. In mammals, there is a reduction in body temperature, breathing and heart rate.

Question 36

Predictive dormancy

Answer 36

Occurs before the arrival of adverse conditions, eg. trees shedding their leaves in the autumn due to decreasing day length.

Question 37

Consequential dormancy

Answer 37

An organism becomes dormant after the arrival of adverse conditions, eg. aestivation in lungfish

Question 38

Hibernation

Answer 38

A period of dormancy used to survive harsh winter conditions.

Question 39

Aestivation

Answer 39

A period of dormancy used to survive high temperatures or drought.

Question 40

Daily torpor

Answer 40

A period of reduced activity within a 24 hour period, used by animals with very high metabolic rates to conserve energy. eg. bats

Question 41

Migration

Answer 41

The regular movement of members of a species from one place to another, over a long distance to avoid low temperatures and food shortages. eg. humpback whale, monarch butterfly.

Involves the expenditure of large quantities of energy, so the benefit of migration must outweigh the cost.

Question 42

Studying migration

Answer 42

Bird ringing, coded tags, coloured bands or satellite transmitters are used to track migratory species in order to learn about their route, the timing of migration and details of the individual animals.

Question 43

Innate behaviour

Answer 43

Behaviour that is inherited from parents.

It is inflexible, and is performed in the same way by every member of a species, in response to an external stimulus eg. day length

It is the main factor influencing migration.

Question 44

Learned behaviour

Answer 44

Begins after birth/hatching and is gained by experience and trial and error learning.

It can be learned from parents or members of a social group, and is more flexible than innate behaviour.

It has a secondary role in influencing migration.

Question 45

Displacement experiment

Answer 45

Birds are captured on their migration route, and are transported somewhere else before being released.

Juveniles continue on the same course and get lost (innate behaviour only)

Adults change course as a result of experience (innate behaviour is modified by learning)

Question 46

Ink pad experiment

Answer 46

Birds that have been hatched in an incubator and kept apart from their parents show an innate tendency to fly in the same direction.

The direction can be recorded on a filter paper cone above a cage with an ink pad on the floor.

Question 47

Cross fostering experiment

Answer 47

Eggs from the nests of non-migratory herring gulls are swapped with eggs from the nests of migratory black backed gulls.

The herring gull chicks follow their migrating foster parents.

The black backed chicks left their foster parents and migrated, leaving their parents behind.

This shows that innate behaviour is a more important factor influencing migration than learned behaviour, but both have an influence.

Question 48

Tolerable limits

Answer 48

Conditions beyond which homeostasis is no longer able to maintain a constant internal environment. eg. extreme heat/cold.