Unit 3 Organisms exchange with their environment

Question 1

Why are substances transported to the other tissues and cells via the tissue fluid?

Answer 1

The distance between the cells and the substance that are needed to diffuse are too large

Question 2

What is the membrane in which substance s are transferred across within an organism?

Answer 2

The tissue fluid

Question 3

How does the exchange between substances and the tissue fluid occur?

Answer 3

Once absorbed the materials are rapidly distributed to the tissue fluid ad the waste products are returned to the exchange surface for removal

Question 4

During the transfer of substance what is maintained between the cell-surface membrane?

Answer 4

The diffusion gradients have been maintained

Question 5

What are the factors that affect the transport of the materials that are diffused?

Answer 5

The size and metabolic rate of the organisms

Question 6

Why do size and metabolic rate affect the transport of the materials within an organism?

Answer 6

Ann organism with a high m,etabolic rate requires more exchange of materials and therefore requires a large SA : V ratio

Question 7

Give some examples of what is exchanged between the surfaces in the organism?

Answer 7

Useful products: Glucose, oxygen , amino acids, lipids
Waste products: Urea, ammonia, Carbon dioxide

Question 8

What are the transport processes that help the exchanges?

Answer 8

Diffusion, osmosis and active transport

Question 9

Explain the SA:V ratio between small and large organisms and how the transport systems work alongside them?

(small organism)

Answer 9

In small organisms - the SA:V ratio is larger enough as the SA is larger than the volume so they don’t require a transport mechanism for exchanging as there is a shorter diffusion distance between the surface of the organism and the blood

Question 10

Explain the SA:V ratio between small and large organisms and how the transport systems work alongside them?

(large organism)

Answer 10

The large organism has a greater volume than the SA so the SA:V ratio is smaller than of the smaller organisms so it will have a higher metabolic rate and will need a larger exchange of materials.

Thi means that it requires an exchange system so that it can allow the efficient diffusion or active tranpsort materials within an organism so that it cna meet its needs

Question 11

One way that the SA of a leaf can be increased?

Answer 11

A flattened surface so that the distance between the cell and the cell-surface membrane is shorter for the exchange of substances which makes it faster

Question 11

How can large organisms have increased SA? (One way)

Answer 11

Large organisms have specialised exchange surface with the such as lungs in mammals and fish in gills

Question 11

What are the efficiency of exchange surfaces give examples?

Answer 11

Large SA:V ratio = Increased rate of exchange

Thin membrane so there is a short diffusion distance and the materials can diffuse faster

Selectively permembale membrane allows specific materials to oass through

Transport medium such as air allows the maintenace of a concentratuion gradient

Transport system = enable the concnetration gradienct such as the blood

Question 12

What is the direct proportion equation for diffusion?

Answer 12

Diffusion = k(SA x difference in conc grad) / length in diffusion path

Question 13

The increase in gas exchange in other organisms conflicts what else?

Answer 13

The gas exchange conflicts with the conservation of water because it can evaporate

Question 14

How are insects adapted for gas exchange?

Answer 14

Insects have an internal network of tubes called the trachea which are supported by strengthened rings to prevent them fom collapsing

Question 15

How are insects adapted for gas exchange? (2)

Answer 15

The trachea divide into smaller tubes called the tracheoles which extend throughout all the tissues within the insect

Question 16

What happens to the insects whilst they are repsiring explain the process?

Answer 16

The concentration of oxygen falls as they are respiring which leads to

Question 17

Why are the ends of tracheoles contain water?

Answer 17

The muscles cells that respire carry out anaerobic respiration producing lactate which is soluble and lowers the water potential of the muscle cells this means that the volume of water that is taken from the tracheoles is at a fast rate so more air is drawn

Question 18

What happens at the spiracles of insects?

Answer 18

Gases can leave or enter through these tiny pores on the body’s surface when spiracles are open the water can evaporate from the insect this is usually happening to prevent water loss

Question 19

Describe the structure of the gill in fish?

Answer 19

The gills are located behind the head and are made up of gill filaments and are stacked up in a pile. To the right angles of filaments are gill lamellae which increase the SA of the gills

Question 20

What is unusual about the flow of water and the flow of blood along the gill lamellae?

Answer 20

The flow of water and the flow of blood along the gill lamellae are in opposite directions so are in a counter-current flow

Question 21

What would happen if the flow of blood and water are in the same directions?

Answer 21

If the flow of blood and water were in the same direction then there is less gas exchange by 80% of oxygen

Question 22

Explain the counter-current exchange principle works?

Answer 22

The blood with the lowest concentration of oxygen meets the water with the highest concentration of oxygen so there si a diffusion gradient maintained

Question 23

How are the steep diffusion gradient maintained for the fish ?

Answer 23

Ventilation constantly bringing the water along the gill lamellae and the mass transport in the blood can carry away oxygen from the surface

Question 24

Explain how gas exchange occurs during photosynthesis?

Answer 24

During photosynthesis some carbon dioxide comes from the respiration of cells and most of it is retained via the the air. Also some oxygen is produced during photosynthesis and used in respiration but also diffuses out of the cell

Question 25

Explain how gas exchange occurs not during photosynthesis?

Answer 25

When photosynthesis isn’t occurring the oxygen diffuses into the leaf because of the constant need for it during respiration by the cells which means the carbon dioxide being constantly produced diffuses out of the leaf

Question 26

What are the adaptations of a leaf during gas exchange?

Answer 26

Many small pores stomata and each plant cell is close to a stomata so the distance is short

Numerous interconnecting air spaces that occur throughout the mesophyll so they come into contact with the mesophyll cells

Large SA of mesophyll cells for rapid diffusion

Question 27

Describe stomata?

Answer 27

Stomata are usually found on the underside of the leaf because it is shaded from the sun and reduces evaporation

They are surrounded by guard cells that control the entrance and the exit of gases in and out of the leaf

So they control the rate of gaseous exchange so they can control the evaporation of water

Question 28

What are terrestrial organisms and what is the problem with them?

Answer 28

Organisms that live on land and water easily evaporates from the surface of their bodies and they become dehydrated and so they have to evolve to conserve water

Question 29

How have insects evolved to conserve water?

Answer 29

They have a small SA:V ratio to minimise the area of water in which water is lost

Waterproof coating over their bodies surface as rigid exoskeleton of chitin has a waterproof cuticle

Spiracles which can be closed to reduce water loss

Question 30

How do plants limit their water loss?

Answer 30

Plants can close their stomata to reduce their water loss via transpiration

Question 31

What are xerophytes?

Answer 31

Plants that are adapted to minimise their water loss by conserving water

Question 32

What are modification to plants structures that allow the prevention of water via evaporation?

Answer 32

Thick cuticle - less water is able to escape

Rolling up leaves - this protects the lower epidermis as it is usually saturated with water and has a high water potential

Hairy leaves - this traps still air which means the water potential gradient is net zero as the inside and the outside of the leaf allow no water loss

Stomata in pits or grooves - trap still moist air and reduce the water potential gradient

A reduced SA:V ratio of the leaves slower the rate of diffusion which means the water loss is considerably reduced as the cross sectional area is smaller

Question 33

Why is the lungs inside the body as the site of gas exchange?

Answer 33

Air is not dense enough to support and protect these delicate structures and the body as a whole would lose a great deal of water and dehydrate

Question 34

What features of the lungs and around the lungs adapt to efficient gas exchange?

Answer 34

1) Lungs have paired lobes which mens that they contain alveoli
2) The trachea are strengthened by the crtilage c shaped rings that prevent it by