8.1 - Transport Systems in Multicellular Animals

Question 1

Why do animals need metabolic transport systems?

Answer 1

• High metabolic demand
  
  • long distance diffusion not enough
• SA:V gets smaller as animals get larger
  
  • results increase in diffusion distance and lower relative SA for diffusion to occur
• Molecules synthesised in one location, need to be transported to another (hormones, enzymes)
• Food digested in one organ system
  
  • must be transported to every cell
• Metabolic waste products need to be removed and transported to excretory organ.

Question 2

Define mass transport system.

Answer 2

Where substances are transported in a fluid mechanism around the body.

Question 3

What are the features of an insect’s open circulatory system?

Answer 3

Haemocoel: An insect’s open body cavity

Haemolymph: Insect blood

• No separate tissue fluid, so haemolymph is in in contact with organs and cells
• Few vessels so blood pumped straight from heart to haemocoel
• Haemolymph holds no O₂ or CO₂ - gas exchange performed in tracheal system
  
  • It transports: nitrogenous waste, disease defence cells
• Oxygenated & deoxygenated blood freely mix
• Body movements affect circulation
• Pressure cannot be changed to support circulation

Question 4

Give features of a closed circulatory system in fish

Answer 4

• Blood in vessels - no direct contact to cells*​*​
  
  • ​Substances leave by diffusion
• Pressure can be maintained and is higher than an open system
• Flow can be directed to different tissues and organs

Question 5

Give features of a single closed circulatory system.

Answer 5

• Blood flows through the heart once per circulation
• Blood flows throgh 2 sets of capillaries before the heart
  
  • 1^st one for gas exchange - e.g. gills
  • 2^nd for substance exchange in organs

LIMITATIONS:

• Blood passes through narrow capillaries, lowering blood pressure
  
  • Blood returns to heart slowly minimising efficiency

Question 6

As opposed to other organisms with single closed circulatory systems, why are fish efficient?

Answer 6

1. Countercurrent flow maximising gas exchange
2. Body weight supported by water
3. Doesn’t maintain own body temperature
   
   1. 2 and 3 reduce metabolic demand

Question 7

What are features of a double circulatory system?

Answer 7

• Blood flows through heart twice for every circuit of circulation
• 2 circuits
  
  • 1^st is the pulmonary circulation - used to carry blood to lungs and oxygenate
  • 2^nd is to carry O₂ and other nutrients around the body
• Per circuit, the blood only passes one capillary network, so pressure is maintained