Excahnge Surfaces

Question 1

Do larger animals have a low or high surface area?

Answer 1

-smaller surface area

Question 2

Explain how the size of an organism and its structure relate to its surface area to volume ratio.

Answer 2

As an organism grows larger, its volume increases more rapidly than its surface area because volume is proportional to the cube of the organism’s size, while surface area is proportional to the square of its size.

As a result, larger organisms have a smaller Sa:Vol compared to smaller organisms.

This affects various physiological processes such as gas exchange, nutrient absorption, and heat exchange, as organisms with a smaller surface area to volume ratio may struggle more with these processes.

Question 3

Describe how larger organisms increase their surface area to volume ratio.

Answer 3

Larger organisms increase their surface area to volume ratio through various adaptations such as folding, branching, or specialized structures.

Question 4

What are cell surrounded by?and function?

Answer 4

1-tissue fluid which maintains our internal environment.

2-Once substances are exchanged, they are distributed into the tissue fluid so all cells are supplied and can remove their waste products.

Question 5

What gets exchanged?

Answer 5

Respiratory gases - oxygen, carbon dioxide
➔Nutrients - glucose, amino acids, fatty acids, etc
➔Excretory products - urea, carbon dioxide, etc
➔ Heat

Question 6

How do these exchanges happen?

Answer 6

1. Passively - no metabolic energy is required - diffusion or osmosis
2. Actively - using metabolic energy - active transport

Question 7

Work out surface area and volume of a cube?

Answer 7

SA = 6s2
Vol = s3

Question 8

What features have Organisms evolved to ensure efficient exchange can occur?

Answer 8

1. Flattened shape
2. Specialised exchange surfaces to increase SA:Vol ratio
3. Mass transport system

Question 9

What are the Features of specialised exchange systems?

Answer 9

1. Large SA:Vol ratio
2. Thin
3. Selectively permeable
4. Movement of environmental medium
5. Transportsystem

Question 10

These three organisms live in the same environment and have evolved in different ways. Using your knowledge on exchange with the environment and SA:Vol ratio, identify and explain which organism will struggle the most to maintain its warmth. (4 marks)

Answer 10

1. Arctic Hare
2. Larger ears
3. Increases SA:Vol ratio
4. More heat is lost
   Polar Bear Arctic Fox

Question 11

Work out the Sa and vol of s sphere?

Answer 11

SA = 4𝛑r2
Vol=4/3𝛑r3

Question 12

Diffusion equation:

Answer 12

Diffusion is proportional to surface area * concentration gradient/thickness of membrane

Question 13

Name 3 factors which affect the rate of diffusion.

Answer 13

Concentration gradient
Temperature
Sa

Question 14

What are single celled organisms?

Answer 14

Single-celled organisms are small and therefore have a large SA:Vol ratio

Question 15

Describe how single-celled organisms exchange gases

Answer 15

Oxygen can be absorbed by diffusion across their body surface and carbon dioxide can be released in the same way.

Question 16

Example of single-celled organisms?and do they have a high or low metabolic rate?they have evolved to do what?

Answer 16

-Insects
-are very active organisms meaning they have a relatively high metabolic rate.
-They have evolved to reduce water loss whilst maintaining a highly adapted exchange system.

Question 17

What gas system do insects use?

Answer 17

Tracheal system

Question 18

How is the fish gas exchange system better than the humans?

Answer 18

In fish, blood leaving has more oxygen than water leaving

2. (But) in humans, blood leaving has less oxygen than air leaving
   Difference in oxygen (concentration) between artery and vein is greater in fish than in humans

(So) fish remove a greater proportion from the oxygen they take in

Question 19

Describe and explain the advantages of the counter current principles in gas exchange across a fish gill

Answer 19

1.Water and blood flow in opposite directions
2. Maintains diffusion/concentration gradient of oxygen

Oxygen concentration always higher (in water)
Diffusion happens along length of lamellae/filament/gill/capillary

Question 20

Describe the Path way taken by oxygen from alveolus to the blood

Answer 20

-Across the alveolar epithelium
-Endothelium / epithelium of capillary;

Question 21

Explain 2 ways in which the structure of fish gills are adapted for effective gas exchange.

Answer 21

1-lamella increase the Sa:Vol ration
2-thin surface so short diffusion pathway

Question 22

Describe the processes involved in the absorption and transport of digested lipid molecules from the ileum into lymph vessels

Answer 22

1.Micelles contain bile salts and fatty acids/monoglycerides

2. Make fatty acids/monoglycerides (more) soluble (in water)
3. Fatty acids/monoglycerides absorbed by diffusion
4. Triglycerides (re)formed (in cells)
   Or chylomicrons form
5. Vesicles move to cell membrane