Exchange And Transpor

Question 1

What surface area to volume ratio do single cell organisms have?

Answer 1

a high SA:V ratio which allows for the exchange of substances to occur via simple diffusion

The large surface area allows for maximum absorption of nutrients and gases and secretion of waste products
The small volume means the diffusion distance to all organelles is short

Question 2

As organisms increase in size, what happens to their surface area to volume ratio?

Answer 2

their SA:V ratio decreases
There is less surface area for the absorption of nutrients and gases and secretion of waste products
The greater volume results in a longer diffusion distance to the cells and tissues of the organism

Question 3

Why is oxygen required for specialised systems for gas exchange?

Answer 3

Supply of Oxygen:

Organisms require ATP in order to carry out the biochemical processes required for survival. The majority of ATP is produced through aerobic respiration which requires oxygen

Question 4

Why is the removal of carbon dioxide needed for specialised systems gas exchange

Answer 4

Removal of Carbon Dioxide:

Carbon dioxide is a toxic waste product of aerobic respiration
If it accumulates in cells/tissues it alters the pH

Question 5

Why is diffusion a viable transport mechanism for single-celled organisms but not for larger multicellular organisms

Answer 5

The time taken for oxygen to diffuse from the cell-surface membrane to the tissues would be too long

Question 6

Body mass affecting metabolic rate

Answer 6

Experiments conducted by scientists have shown that the greater the mass of an organism, the higher the metabolic rate

Therefore, a single rhino consumes more oxygen within a given period of time compared to a single mouse

Question 7

SA:V Ratio affecting metabolism

Answer 7

Although metabolic rate increases with body mass the BMR per unit of body mass is higher in smaller animals than in larger animals

Smaller animals have a greater SA:V ratio so they lose more heat, meaning they have to use up more energy to maintain their body temperature

Question 8

What is metabolic rate

Answer 8

The metabolic rate of an organism is the amount of energy expended by that organism within a given period of time

Question 9

What is the basal metabolic rate

Answer 9

The basal metabolic rate (BMR) is the metabolic rate of an organism when at rest. The BMR is significantly lower than when an organism is actively moving

Question 10

How can the metabolic rate of an organism be measured

Answer 10

The metabolic rate of an organism can be measured/estimate using different methods:
Oxygen consumption
Carbon dioxide production
Heat production

Question 11

What features that organism surfaces have that make them effective exchange surfaces have

Answer 11

A large surface area
Short diffusion distance
Concentration gradient (maintained)

Question 12

What does all trachael insect systems contain

Answer 12

All insects possess a rigid exoskeleton with a waxy coating that is impermeable to gases

Insects have evolved a breathing system that delivers oxygen directly to all the organs and tissues of their bodies

Question 13

What is a spiracle

Answer 13

A spiracle is an opening in the exoskeleton of an insect which has valves

It allows air to enter the insect and flow into the system of tracheae

Most of the time, the spiracle is closed to reduce water loss

Question 14

What are the tracheae

Answer 14

Tracheae are tubes within the insect breathing system which lead to tracheoles (narrower tubes)

The tracheae walls have reinforcement that keeps them open as the air pressure inside them fluctuates

Question 15

Where do the tracheoles go?

Answer 15

A large number of tracheoles run between cells and into the muscle fibres - the site of gas exchange

For smaller insects, this system provides sufficient oxygen via diffusion

Question 16

How is a concentration gradient created in insects?

Answer 16

A concentration gradient is created as oxygen is used by respiring tissues allowing more to move in through the spiracles by diffusion

Carbon dioxide produced by the respiring tissues moves out through the spiracles down a concentration gradient

Question 17

How do insects create a mass flow of air into the tracheal system

Answer 17

flying insects need a more rapid supply/intake of oxygen.
They create a mass flow of air into the tracheal system by:
Closing the spiracles
Using muscles to create a pumping movement for ventilation

Question 18

What happens during flight in an insect

Answer 18

During flight, the production of lactate in the respiring muscles, lowers the water potential of muscle cells

water found at the narrow ends of the tracheoles is then drawn into the respiring muscle by osmosis

This allows gases to diffuse across more quickly

Question 19

Structure of fish gills in bony fish

Answer 19

Series of gills on each side of the head
Each gill arch is attached to two stacks of filaments

On the surface of each filament, there are rows of lamellae

The lamellae surface consists of a single layer of flattened cells that cover a vast network of capillaries

Question 20

Explain the mechanism of the structure of bony fish

Answer 20

The capillary system within the lamellae ensures that the blood flow is in the opposite direction to the flow of water - it is a counter-current system

The counter-current system ensures the concentration gradient is maintained along the whole length of the capillary

The water with the lowest oxygen concentration is found adjacent to the most deoxygenated blood

Question 21

Structure of a leaf:

Answer 21

Waterproof cuticle
Upper epidermis - layer of tightly packed cells
Palisade mesophyll layer - layer of elongated cells containing chloroplasts
Spongy mesophyll layer - layer of cells that contains an extensive network of air spaces
Stomata - pores (usually) on the underside of the leaf which allow air to enter
Guard cells - pairs of cells that control the opening and closing of the stomata
Lower epidermis - layer of tightly packed cells

Question 22

Mechanism of the structure of the leaf

Answer 22

When the guard cells are turgid (full of water) the stoma remains open allowing air to enter the leaf

The air spaces within the spongy mesophyll layer allows carbon dioxide to rapidly diffuse into cells

The carbon dioxide is quickly used up in photosynthesis by cells containing chloroplasts - maintaining the concentration gradient

No active ventilation is required as the thinness of the plant tissues and the presence of stomata helps to create a short diffusion pathway

Question 23

Why is the exchange of gases from the atmosphere essential for the survival of organisms

Answer 23

Oxygen is required for respiration
Carbon dioxide is required for photosynthesis

Question 24

What range of vital functions within organisms does water have

Answer 24

It is a solvent that facilitates the transport of essential nutrients

Extreme water loss can lead to death

It is a solvent that facilitates the transport of essential nutrients
Extreme water loss can lead to death

Question 25

What do terrestrial insects have that prevents water loss

Answer 25

The waterproof waxy coating of the exoskeleton makes gas exchange by diffusion very difficult

As a result, insects have evolved a breathing system (the tracheal system)which consists of many tubes that carry oxygen directly to all tissues and cells of the body

Spiracle are openings in the exoskeleton of insects that are connected to the tracheal system

Question 26

Why are xerophytic plants vulnerable to water loss

Answer 26

Plants that live in conditions with a plentiful supply of freshwater have leaves with a short diffusion distance through the stomata and a large surface area provided by the air spaces in the spongy mesophyll

Question 27

What adaptations do xerophytic plants have

Answer 27

adaptations to conserve water:
Very few stomata
Sunken stomata
Hairs surrounding stomata
Needle-shaped or small leaves
Waxy cuticle

Question 28

Characteristics of cacti

Answer 28

Their leaves have become spines that can no longer photosynthesise

Photosynthesis occurs in the green stem which possesses chloroplasts

The stem has a thick cuticle and is very large in diameter which allows it to store water

There are both shallow and deep penetrating roots which allow it to access all available water

Question 29

Marram Grass sand dune grass adaptions

Answer 29

Leaves can roll up to reduce the exposure of surfaces to the wind

The rolling of the leaf provides deep grooves which protect the stomata

The exposed surface has no stomata and a thick cuticle

The inner surface of the leaf possesses a large number of hairs