8.1 Transport Systems in Multicellular Animals Flashcards Preview

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Flashcards in 8.1 Transport Systems in Multicellular Animals Deck (11):

Why do multicellular animals need specialised transport systems?

High metabolic demands so diffusion over long distance is not enough to supply quantities needed

Surface area to volume ratio is small

Molecules ( eg hormones , enzymes ) may be made in one place but needed in another

Food digested in one organ system, but needs to be transported to every cell for use in respiration and other aspects of cell metabolism

Waste products of metabolism need to be removed from the cells and transported to excretory organs


Define mass transport

When substances are transported in a mass of fluid


Describe open circulatory systems

Very few vessels to contain transport medium

Pumped straight from heart into body cavity (haemocoel) of animal

Comes into direct contact with tissues and cells


Describe the circulatory system of insects


Insect blood (haemolymph) transports food and nitrogenous water products and immune system cells

Body cavity is split by membrane

Heart extends along the length of the thorax and abdomen


What are the disadvantages of open circulatory systems?

Steep diffusion gradients cannot be maintained for efficient diffusion

Amount of blood flowing to a particular tissue cannot be varied to meet changing demands


Describe closed circulatory systems

Blood is enclosed in blood vessels

Doesn’t come into contact with cells of the body

Heart pumps blood around the body under pressure and relatively quickly

Substances leave and enter the blood by diffusion


What are the advantages of closed circulatory systems

Amount of blood flowing to a particular tissue can be adjusted by widening or narrowing blood vessels

Blood transported under pressure so it is fast and efficient


Describe single circulatory systems

The blood flows through the heart once

The blood passes through two sets of capillaries before it returns to the heart


What are the disadvantages of single circulatory systems ?

As it passes through two sets of narrow vessels the blood pressure drops so blood returns to the heart slowly


Describe double circulatory systems

Blood travels twice through the heart

Once to the lungs and once to the body


What is the advantage of double circulatory systems ?

Each circuit only travels through one capillary network, which means a high pressure and fast flow of blood can be maintained