These notes contain the details of all aspects of the systems within Transport in Animals that you need to know for the exam. They are a a summary, containing diagrams, of the textbook notes and are much easier to read and understand.
Need for transport systems -
Very small animals (single celled organisms) - do not need a transport system they can rely on
diffusion alone.
They have a large enough surface area to volume ratio so that diffusion is sufficient enough for
their metabolic needs. Diffusion is quick enough to supply oxygen and nutrients.
3 things that influence weather you need a transport system or not:
1) Size - cells in larger organisms are further from the surface, so distance increases
meaning that diffusion is too slow for the requirements. Also in larger organisms the
outer cells will use up all the supplies and it will never reach the cells deep inside the
body.
2) Surface area to volume ratio - organisms with large surface area to volume ratio, there
are a large amount of cells that reach the surface and can take in the cells. Larger
animals have a smaller surface area to volume ratio - each gram of tissue has a smaller
area of body for exchange.
3) Level of metabolic activity - If an animal is very active, its cells need good supplies of
nutrients and oxygen to supply the energy for movement. Animals that keep themselves
warm need even more energy.
A good transport system:
- A fluid or medium to transport: oxygen, nutrients and waste products around the body -
this is blood
- A pump to create pressure that will push the bloody around - this is the heart.
- Exchange surfaces that allow substances to be able to enter and leave the blood - these
are capillaries
- Tubes or vessels to carry the blood by mass flow
- Two circuits, one to pick up the oxygen and another to deliver to the respiring tissues.
Single circulatory systems:
- Fish have these - the blood flows through the heart once for
each circuit of the body.
- The blood takes the following route: Heart - gills - body - heart
- Blood pressure drops as blood passes through the capillaries of
the gills
- Blood has low pressure as it flows towards the body and will not flow very fast otherwise
the gills will be damaged.
- Rate at which oxygen and nutrients are delivered to respiring tissues, and carbon
dioxide and urea are removed.
- Fish are not as metabolically active as mammals and they don’t need to maintain their
body temperature therefore they need less energy. Their system delivers sufficient
oxygen for their needs.
, Double circulatory systems:
- Mammals have these - two seperate circuits. One circuit carries
blood to the lungs to pick up oxygen (pulmonary circulation)
- The other circuit carries the oxygen and nutrients around the body
to the tissues. (systemic circulation)
- Blood flows through the heart twice for each circuit of the body. It
takes this route:
Heart - body - heart - lungs - heart
- Blood pressure must not be too high in the pulmonary circulation,
otherwise it may damage the capillaries in the lungs.
- Heart can increase the pressure of the blood through the systemic system after it has
passed through the lungs, so the blood flows to the body more quickly.
- Systemic circulation can carry blood at higher pressure than the pulmonary circulation.
- Mammals are active animals and maintain their body temperature - supplying the energy
for activity the heat needed
Why is a double circulatory system better?
It will carry and deliver oxygen and nutrients more quickly to the parts of the correct parts of the
body. The blood can be made to flow more easily from pressure created by the heart. - so the
blood travels faster to the body, meaning that it meets the metabolic needs of the mammal.
There are different levels of pressure.
An Open system: (less efficient)
- Consists of a heart that pumps hemolymph through vessels into a cavity called
haemocoel.
- In the haemocoel, the hemolymph directly bathes organs and tissues, enabling the
diffusion of substances.
- When the heart relaxed the hemolymph blood is sucked back in via pores called ostia.
- Haemolymph moves around the haemocoel due to the movement of the organism.
- Circulation of Oxygen transport is slower.
A closed system: (more efficient)
- Blood is fully enclosed within vessels at all times.
- From the heart, the blood is pumped through progressively smaller vessels.
- In the smallest vessels, capillaires, substances diffuse in and out of the blood and into
cells.
- Blood then returns to the heart via a series of progressively larger vessels.
- Blood can be put under pressure, so it travels faster and is able to diffuse into cells
quickly.
- Blood can be directed to where it’s needed the most, instead of travelling through a
whole cavity.
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