Circulatory Systems

Question 1

Why do multicellular organisms need a transport system?

5 reasons

Answer 1

They have:

1) A high metabolic rate as they require more food, energy and oxygen to meet demands
2) Small surface area so diffusion alone is impossible to transport substances
3) Hormones to be transported from cells in one part of the body to another
4) Waste products to be removed all the time
5) Digested food produces glucose and nutrients that travel to every cell

Question 2

What are the 3 features that make up a circulatory system?

Answer 2

A liquid transport medium
Vessels that carry he transport medium
Pumping mechanism to move fluid around the body

Question 3

What is mass transport?

Answer 3

When a substance is transported in a mass of fluid with a pumping mechanism to move the fluid and vessels to carry it.

Question 4

Describe the path in which haemolymph (transport medium) travels through an OPEN CIRCULATORY SYSTEM.

Answer 4

1) Very few vessels to contain medium
2) Transport medium is pumped into body cavity
3) In body cavity, transport medium is in direct contact with tissues and cells at low pressure
4) Transport medium returns to heart via open ended vessels.

Question 5

What is an open circulatory system?

Answer 5

Where blood isn’t isn’t enclosed in blood vessels all the time. The blood flows freely through the body cavity.

Question 6

What is another name for:
Body cavity?
Transport medium?

(In insects and some other invertebrates)

Answer 6

Body cavity- haemocoel

Transport medium- haemolymph

Question 7

What is a closed circulatory system?

Answer 7

Where the blood is enclosed inside blood vessels.

Question 8

Which animals have a:
Closed circulatory system?
Open circulatory system?

Answer 8

All vertebrates (e.g. fish and mammals)
Some invertebrates (e.g. insects)

Question 9

What are the two types of (closed) circulatory system?

Answer 9

Single and double circulatory systems.

Question 10

What is a single circulatory system?

Answer 10

When the blood goes through the heart once.

Question 11

What path does the blood take in a single closed circulatory system?

Answer 11

1) Blood flows through heart
2) Heart pumps it out to the body
3) Blood flows through 2 sets of capillaries
4) Blood returns to heart at low pressure

Question 12

How do birds and mammals maintain their body temperature (being very active animals)?

Answer 12

By having a double circulatory system

Question 13

What is a double circulatory system?

Answer 13

When blood flows through the heart twice.

Question 14

What path does the blood take in a double circulatory system?

Answer 14

1) Blood pumped from heart to lungs
2) Blood is pumped from lungs back to heart
3) Blood flows from heart out to the rest of the body
4) So overall goes through the heart twice

Question 15

Why are land predators good at maintaining their body temperature?

Answer 15

They have a double circulatory system meaning substances are transported more efficiently around the body at a high pressure.

Question 16

Why does a land predator have a double circulatory system?

Answer 16

• Needs to support body against gravity as they get bigger.
• Needs to support needs of foetus (when pregnant)
• High levels of O2 and CO2 come and go from tissues.
• They have a high metabolic rate.

Question 17

Why do aquatic mammals have a single closed circulatory system?

Answer 17

• Body temperature is maintained by environment not the circulatory system
• Single circulatory system is good enough to meet their demands

Question 18

How do nutrients get to cells in a closed circulatory system?

Answer 18

There is no direct contact between cells and nutrients. Instead, nutrients diffuse through capillary walls to each cell.

Question 19

True or False?

A steep diffusion gradient can be maintained in an open circulatory system.

Answer 19

False. A steep diffusion gradient is maintained in a CLOSED circulatory system.

Question 20

What does haemolymph (insect blood) carry around the body?

What does it not carry?

Answer 20

It carries food, nitrogenous waste and cells involved in defence against disease.
It doesn’t carry oxygen and carbon dioxide.

Question 21

Is the haemolymph at a high or low pressure in the haemocoel?

Answer 21

Low pressure

Question 22

What makes the open system less efficient?

Answer 22

1) Haemolymph cannot be varied to meet changing demands of insect
2) Steep diffusion gradient cannot be maintained

Question 23

What are the two circuits called in the double circulatory system?

Answer 23

Pulmonary circuit and Systemic circuit

Question 24

What does blood transport around the body?

Answer 24

Oxygen, carbon dioxide, digested food and cells that defend against disease.

Question 25

What makes the double system more efficient?

Answer 25

1) Steep concentration gradient is maintained

2) Blood flow can be altered to meet changing demands of the body.