transport systems in multicellular animals Flashcards

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1
Q

Reasons for multicellular organisms needing a transport system.

A

1- Multicellular organisms are complex and very active. They have a lot of cells requiring oxygen and glucose and also have a lot of waste product to get rid of.
2- The larger the organism, the smaller the SA:volume ratio, so the distance for diffusion to the cells in the centre is too big and that’s is a smaller surface area to do it.
3- Many molecules e.g hormones/enzymes are produced in one part of the body, but need to travel to another- must somehow be transported.
4- Food is digested in the digestive system, but the products of this are needed all over the body.
5- All cells produce water products, which need transporting to the excretory organs.

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2
Q

What are the features that most circulatory systems have in common?

A

-Liquid transport medium, circulates around system (blood).
-Usually have vessels to carry the blood.
- Usually have a pumping mechanism to move the fluid around the system (heart).

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3
Q

What happens during a single circulatory system?

A
  • Blood passes through the heart once during each circuit of the body.
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4
Q

How many sets capillaries does the blood pass through in single circulatory systems and what happens in each?

A
  • Blood passes through 2 sets of capillaries before it returns to the heart.
  • In the first, it exchanges oxygen and carbon dioxide.
  • In the second, substances are exchanged between the blood and cells.
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5
Q

What is a disadvantage of a single circulatory system?

A
  • Blood has to pass through 2 sets of narrow capillaries before returning the heart.
    Pressure is lost along the way, so the flow-rate slows down, less efficient.
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6
Q

How can fishes have a single closed circulation system and still be active?

A
  • They have a countercurrent gaseous exchange mechanism in their gills that allows them to take a lot of oxygen from the water. This reduces metabolic demands.
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7
Q

What happens during a double circulatory system

A
  • Blood passes through the heart twice during each circuit of the body.
  • Left side deals with oxygenated blood and right side deals with deoxygenated blood.
  • Blood is pumped from the right side of heart to the lungs to pick up oxygen, and unload CO2 and then returns to heart.
  • Blood flows through the heart and is pumped out to travel all around the body before returning to heart again.
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8
Q

Advantage of double circulatory system.

A
  • When blood travels through the capillaries of the lung, it’s pressure and flow rates are reduced.
  • In the double system- this blood then flows back to the heart and is re-pressurised before flowing around the body to the cells. This increases the flow rate again, which is more efficient for delivery of oxygen to cells.
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9
Q

What happens during open circulatory system?

A
  • Very few vessels to contain transport medium.
  • It is pumped straight from the heart into the body cavity of the animal.
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10
Q

What is an open body cavity called and what happens in it?

A
  • Open body cavity is called the haemocoel.
  • In haemocoel transport medium is under low pressure. It comes into direct contact with tissues and cells.
  • This is where exchange takes place between transport medium and the cells.
  • Transport medium returns to the heart through an open-ended vessel.
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11
Q

What is a disadvantage of an open system?

A

The blood flow rate to all cells and tissues is the same - the amount of blood reaching a particular tissue cannot be varied to meet demand.

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12
Q

What happens during a closed system?

A
  • The blood is enclosed in blood vessels and does not come into contact directly with the cells of the body.
  • Substances leave and enter the blood by diffusion through walls of the blood vessels.
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13
Q

How can blood flowing to a particular tissue be adjusted in a closed system?

A
  • adjusted by widening or narrowing blood vessels.
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14
Q

Examples of each circulatory system.

A

open = insects
closed single = fish
closed double = mammals and birds
closed = starfish and phyla

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