transport in multicellular animals

Question 1

why do multicellular organisms need transport systems?

Answer 1

to supply oxygen and nutrients where they are needed + remove waste products

Question 2

what happens to diffusion rate as organisms get bigger?

Answer 2

larger organisms = larger distance between cells and outside of the body = diffusion is slow

Question 3

suggest 5 reasons why specialised transport systems may be needed

Answer 3

• high metabolic demands (for O2 and food) - diffusion is not sufficient
• SA:V ratio gets smaller as organism gets bigger
• substances are produced in one place but needed in another
• food is digested in one organ system and products need to be transported to all cells (for respiration)
• waste product removal (transport to excretory organs)

Question 4

what is a circulatory system?

Answer 4

a system that carries gases (eg. oxygen, Co2), nutrients, wate products, hormones etc. around the body

Question 5

what are 3 common features of circulatory systems

Answer 5

• liquid transport medium that circulates (eg. blood)
• vessels to pump the medium
• pumping mechanism to move the fluid

Question 6

briefly describe an open circulatory system

Answer 6

where the transport medium is not contained in vessels

Question 7

briefly explain how open circulatory systems work

Answer 7

transport medium is pumped from heart into body cavity

Question 8

what is a haemoceol

Answer 8

the body cavity of an animal

Question 9

what animals have open circulatory systems?

Answer 9

invertebrate animals (eg. insects, molluscs)

Question 10

briefly describe a closed circulatory system

Answer 10

where blood is enclosed in blood vessels and does not directly contact cells

Question 11

briefly describe how a closed circulatory system works (2 points)

Answer 11

• heart pumps blood around under pressure before it returns to the heart directly
• substances leave/enter blood by diffusion through blood vessel walls

Question 12

how can the amount of blood flowing through vessels be adjusted?

Answer 12

through narrowing / widening of blood vessels

Question 13

what animals have closed circulatory systems?

Answer 13

echinoderms (sea urchins, starfish), squid, eathworms and vertebrate groups (mammals)

Question 14

what is a single closed circulatory system?

Answer 14

where blood flows through the heart and travels all around the body before returning to the heart

Question 15

briefly describe the flow of blood in single close circulatory systems (3 points)

Answer 15

• blood passes through 2 sets of capillaries before returning to heart
• 1st: oxygen and CO2 exchanged 2nd: substances are exchanged between blood and cells
• pressure drops considerably so blood returns to the heart at a slower rate - limits efficiency so activity levels are low

Question 16

why do fish have single close circulatory systems?

Answer 16

• countercurrent system - allows a lot of oxygen to be taken from water
• do not maintain/regulate own body temp - lower metabolic demands

Question 17

what is a double closed circulatory system

Answer 17

blood travels through heart twice for each circuit of the body

• 1: to the lungs 2: to the body

Question 18

briefly describe how blood flows through a double closed circulatory system

Answer 18

• blood is pumped from the heart to the lungs - oxygen is picked up and CO2 is unloaded before returning to heart
• blood flows through heart and is pumped out to travel around the body before returning to the heart

Question 19

how are double closed circulatory systems kept at higher pressures/fast flow?

Answer 19

blood only passes through one capillary network