ocr as biology F212

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  • Created on: 04-10-12 22:08
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Chapter 5: transport in animals
LO: explain the need for transport systems in multicellur animals in terms of size, activity and surface
area to volume ratio.
Explain the meaning of the terms single and double circulatory systems with reference to the
circulatory systems of fish and mammals.
Large animal transport systems: living animal cells need a supply of oxygen and nutrients to survive.
They need to remove waste products so that they don't build up and become toxic.
Smaller animals do not need a separate transport system because their cells are
surrounded by the environment that they live in. diffusion is sufficient for this
process.
Large animals however need a complicated transport system or bigger to supply
sufficient oxygen and nutrients to other parts of the body. Diffusion alone will be to
slow for this.
There are 3 main factors that affect the need for a transport system:
Size
Surface area to volume ratio
Level of activity
Size: the bigger the animal, more nutrients and oxygen is needed to supply around the body and
diffusion doesn't reach the deeper parts of the body.
Surface area to volume ratio: small animals have a large surface area to volume ratio (which means
their volume it smaller) large animals have small surface area to volume ratio (a larger volume).
Level of activity: animals need energy which they get from food so they can be metabolically active.
Animals release the energy by respiration this requires oxygen. E.g. mammals need more energy to
keep themselves warm etc.
Features of a good transport system:
A fluid to carry nutrients and oxygen around the body ­ blood.
A pump to create pressure that will push the fluid around the body ­ heart.
Exchange surfaces that will help oxygen and nutrients to enter the blood and to take it
where they are needed.
Single and double circulatory systems:
Fish have a single circulatory system. Blood flows from the heart to the gills and then to the rest of
the body before returning to the
heart. Fish are not as active
and are small they do not maintain
their body temperature. They
don't need a lot of energy.

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Mammals on the other hand have a double circulatory system. Which are two separate circuits. Which
are joined up by the heart. One circuit carries blood to the lungs to pick up oxygen, this is the
pulmonary circulation. The other circuit carries oxygen and nutrients around the body to the tissues,
this is systemic circulation. Blood flows through the heart twice for each circulation.
An efficient circulatory system will deliver oxygen and nutrients quickly to the parts of the body.…read more

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The heart can increase the pressure of the blood after it has passed through the lungs so
blood flows quickly to the body tissues.
The systemic circulation can carry blood at a higher pressure than the pulmonary circulation.
The blood pressure must not be too high in the pulmonary circulation; otherwise delicate
capillaries could potentially burst in the lungs.
Chapter 6: the structure of the mammalian heart
LO: describe the external and internal structure of the mammalian heart.…read more

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Arteries: carry blood from the heart to other places.
Internal features of the heart: the heart is
divided into four chambers. The two top
are the atria (atrium) theses receive blood
from major veins. The bottom two is the
ventricles.…read more

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Chapter 7: the cardiac cycle
LO: describe the cardiac cycle with reference to the action of the valves in the heart.
Sequence of contraction: it is important for the heart to maintain a continuous sequence. The
sequence is involved in one heart beat which is called the cardiac cycle. This lasts for 0.8 seconds. The
cycle has no beginning and no end. We use phases to describe this. You heart beats 70 times a
minute.…read more

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Lisa

this is f211

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