Unit 3 - Circulatory systems

Question 1

Give 5 reasons why specialist transport systems are needed

Answer 1

• metabolic demands of most animals is high
• SA:V decreases as animal size increases so diffusion distances increase whilst SA avaliable becomes relatively smaller
• molecules are made in one place but needed in another
• food will be digested in one organ system but needs to be transported to every cell
• waste products of metabolism need to be removed from cells and transported to excretory systems

Question 2

As an organism gets larger what happens to the diffusion distance?

Answer 2

It gets larger

Question 3

Why does a greater level of activity in an organism increase demand for glucose and oxygen?

Answer 3

• more activity requires more energy
• more energy requires more aerobic respiration
• which requires more reactants (oxygen and glucose)

Question 4

Why does a greater volume of an organism mean a greater demand?

Answer 4

• greater volume means greater number of cells
• each cell requires energy
• so demand for energy/glucose/oxygen increases

Question 5

Define mass flow

Answer 5

the movement of fluids down a pressure or concentration gradient

Question 6

Define circulatory system

Answer 6

the transport system of an organism

Question 7

Define open circulatory system

Answer 7

a transport system with a heart but with few vessels to contain the transport medium

Question 8

Define closed circulatory system

Answer 8

the transport medium is enclosed in vessels and does not come into contact with the cells of the body

Question 9

Define haemolymph

Answer 9

the blood like fluid contained in insects

Question 10

Define single circulatory system

Answer 10

a circulatory system where the blood flows through the heart once during a complete circuit of the body

Question 11

Define double circulatory system

Answer 11

a circulatory system where the blood flows through the heart twice during a complete circuit of the body

Question 12

Define pulmonary circulation

Answer 12

The portion of the circulatory system which carries deoxygenated blood away from the right ventricle of the heart to the lungs and returns oxygenated blood to the left atrium and ventricle

Question 13

Define systemic circulation

Answer 13

The part of the cardiovascular system which carries oxygenated blood away from the heart to the body and returns deoxygenated blood back to the heart

Question 14

Give examples of organisms with a single closed circulatory system

Answer 14

Fish and annelid worms

Question 15

Give examples of organisms with a double closed circulatory system

Answer 15

Birds and most mammals

Question 16

Give an example of an organism with an open circulatory system

Answer 16

Insects

Question 17

Why are fish able to be highly active despite having a single closed circulatory system?

Answer 17

• the countercurrent exchange mechanism means they can take up a lot of O2 from water
• their body weight is supported by the water
• they do not maintain their own body temperatures

Question 18

Why are single closed circulatory systems not very efficient?

Answer 18

Blood pressure drops considerably

so blood flows slowly back to the heart

Question 19

Why are double closed circulatory systems very efficient?

Answer 19

• each circuit passes through only one capillary network
• this maintains relatively high blood pressure
• so fast flow of blood back to the heart is maintained

Question 20

What are the general features of circulatory systems?

Answer 20

• fluid to transport dissolved gases, nutrients, and waste
• a pumping mechanism to move fluid
• sometimes vessels to carry the fluid

Question 21

How are open and closed circulatory systems different?

Answer 21

• blood enclosed in vessels in closed but not in open
• in open circulatory systems the fluid fills body cavities
• open less efficient

Question 22

What is an advantage of having an open circulatory system?

Answer 22

less vulnerable to pressure

Question 23

What is an advantage of closed circulatory systems?

Answer 23

more efficient

Question 24

What is a disadvantage of open circulatory systems?

Answer 24

requires low metabolic rate so does not work for larger animals

Question 25

What is a disadvantage of closed circulatory systems?

Answer 25

requires more energy

Question 26

What are the differences between single and double circulatory systems?

Answer 26

• go through the heart once in one complete circuit in single and twice in double
• single has two sets of capillaries while double has one
• double maintains higher pressure than single

Question 27

What is the disadvantage of single circulatory systems?

Answer 27

They are less efficient