Chapter 8.1 transport system Flashcards
Why do we need a transport system?
-Large multicellular organisms cannot rely on diffusion to move substances in and around the body
Reasons why transport systems are
needed
- Metabolic rate
- Surface area to volume ratio
- Transporting molecules. E.g. food, hormones, enzymes and waste products
Metabolic rate
- Large multicellular organisms have high metabolic rates
- They require high volume of substances and produce a lot of waste
- Diffusion alone would not be able to intake and expel all these substances
tos slow
surface area to volume ratio
In larger organisms, the diffusion of substances would occur far too slowly to enable them to survive
the rate of diffusion increases with the square of the distance it has to travel.
open circulatory system
An open circulatory system consists of a heart that pumps a
fluid called haemolymph through short vessels and into a
large cavity called the haemocoel.
How does an open circulatory stem allow for diffusion of substances
In the haemocoel, the
haemolymph directly bathes
organs and tissues, enabling
the diffusion of substances.
how is haemolymph sucked back in
When the heart relaxes, the
haemolymph blood is sucked
back in via pores called ostia.
how does Haemolymph move around the haemocoel
Haemolymph moves around the haemocoel as the organisim moves
what is a closed circulatory sytem
when the blood is contained within the vessles at all times
how do substances diffuse in a closed circulatory system?
substances diffuse in and out of the blood into cells
example of an open circulatory system
a locust
an example of a closed circulatory system
a fish
what is a single circulatory system
the blood flows through the heart only once during a complete circuit
what is a double circulatory system?
The blood flows through the heart twice during a complete circuit
advantages of a single circulatory system
- less complex
- doesn’t require organs
