Mass transport in animals

Question 1

Do larger or smaller organisms have a larger surface area?

Answer 1

Smaller

Question 2

How does body size affect heat exchange?

Answer 2

Small mammals have larger SA:VOL so lose heat more easily - have a high metabolic rate to maintain body temp.

Question 3

How does body shape affect heat exchange?

Answer 3

• Large ears = large SA:VOL so more heat loss (hot environment)
• Small ears = small SA:VOL so less heat loss (cold environment)

Question 4

How do physiological adaptations affect heat exchange?

Answer 4

• Hibernation –> lowers metabolic rate and body temp –> less heat loss
• Large ears –> increased SA:VOL –> more heat loss

Question 5

How do behavioural adaptations affect heat exchange?

Answer 5

• Huddling –> reduces SA:VOL –> less heat loss
• Cooling in water

Question 6

What are the 5 features of specialised gas exchange surfaces?

Answer 6

1. Large SA:VOL
2. Very thin (short diffusion distance)
3. Selectively permeable (only CO2/O2 can diffuse through)
4. High concentration gradient
5. Transport system (removes O2)

Question 7

How is a short diffusion distance maintained in mammals?

Answer 7

Capillaries and walls of alveoli are 1 squamous epithelial cell thick, capillaries embedded in alveoli walls

Question 8

How is a large surface area maintained in mammals?

Answer 8

Many small alveoli, many narrow capillaries

Question 9

How is concentration gradient maintained in mammals?

Answer 9

Ventilation and circulation

Question 10

How is a short diffusion distance maintained in plants?

Answer 10

Air spaces in spongy mesophyll

Question 11

How is a large surface area maintained in plants?

Answer 11

Many small stomata, flat and broad shape

Question 12

How is concentration gradient maintained in plants?

Answer 12

Photosynthesis and respiration

Question 13

How is short diffusion distance maintained in fish?

Answer 13

Capillaries and walls of lamellae are 1 squamous epithelial cell thick

Question 14

How is a large surface area maintained in fish?

Answer 14

Many gill filaments with many gill lamellae

Question 15

How is concentration gradient maintained in fish?

Answer 15

Counter-current flow

Question 16

Explain how counter-current flow maintains a high concentration gradient in fish

Answer 16

Blood flows in the opposite direction to water and water has a higher conc. of O2 than blood so O2 diffuses into the blood down a conc. gradient across the whole gill lamellae

Question 17

How is a short diffusion distance maintained in insects?

Answer 17

Tracheoles penetrate muscle tissue and lie next to cells

Question 18

How is a large surface area maintained in insects?

Answer 18

Many small spiracles, many narrow branching tracheoles, anaerobic respiration reduces water potential at the ends of tracheoles

Question 19

How is concentration gradient maintained in insects?

Answer 19

Rhythmical pumping abdomen (in large insects), O2 diffuses down spiracles, tracheae, and tracheoles down conc. gradient (in smaller insects)

Question 20

How is tissue fluid formed and returned to the circulatory system?

Answer 20

1. High hydrostatic pressure at arteriole end
2. Small, soluble molecules and water are forced out into cells
3. Large proteins remain in capillary (too big) so water potential is reduced
4. Water moves back into capillary by osmosis
5. Some tissue fluid returned to lymph vessels

Question 21

Describe inspiration

Answer 21

Diaphragm contracts and moves down, external intercostal muscles contract and lift the rib cage up so volume of thoracic cavity increases and pressure decreases to below atmospheric pressure so air moves in down a pressure gradient

Question 22

Describe expiration

Answer 22

Diaphragm relaxes and moves up, internal intercostal muscles contract and move the rib cage down so volume of thoracic cavity decreases and pressure increases to above atmospheric pressure so air moves out down a pressure gradient