Modue 3: Transport In Animals Flashcards
What is transport?
The movement of oxygen, nutrients, hormones, waste
and heat around the body.
Describe the need for transport systems in multicellular animals.
All organisms need oxygen and nutrients to survive. They also must remove waste products as they can become toxic.
Very small organisms do not need a transport system to do this as all of their cells are close to the environment in which they live ‐ diffusion will be sufficient to supply and remove these things.
In larger organisms, diffusion will be too slow to provide sufficient oxygen and nutrients to meet the requirements of the organisms ‐ they need transport systems.
What factors affect the need for transport systems?
- Size
- Level of activity
- SA:VOL
Explain how 3 factors affect the need for transport systems.
Size:
Any oxygen or nutrients diffusing from the environment would be used up by outer layers of cells of the organism. They would not reach the cells deeper in the body.
SA:VOL:
Larger organisms have a smaller surface‐area‐to‐volume‐ratio.
Outer surface is not large enough to enable oxygen etc. to exchange via diffusion fast enough into the body to keep all the cells alive.
Level of Activity:
The more active an animal, the more glucose and oxygen it needs for aerobic respiration to release enough energy to move around.
Some animals like mammals also need energy to keep themselves warm. Diffusion would not be able to supply enough oxygen and glucose to cells to active organisms.
Explain two reasons why mammals need a circulatory system whilst unicellular organisms, such as that shown in the diagram, do not. (4)
(mammals) larger / AW;
cells deep in the body;
regions requiring materials separated by a distance / need to get materials to all parts;
diffusion too slow / AW;
activity
(mammals) more (metabolically) active / AW;
need more materials / more rapid supply / more removal of wastes;
SA:V ratio
(mammals) surface area:volume ratio reduced / AW;
diffusion alone not effective / AW; must be linked to SA:V max 4.
A good transport system must have…
1) A fluid ‐ blood
2) A pump to create pressure ‐ heart
3) Exchange surfaces
What is an open circulatory system?
The blood is not always in vessels e.g. insects.
What is a closed circulatory system?
The blood always remains inside vessels e.g.
fish and mammals.
What are features of an open circulatory system?
An open circulatory system consists of a heart that pumps
blood through short vessels and into a large body cavity.
The blood bathes the cells and tissues where substances are exchanged with the cells.
The blood then returns to the heart through pores called ostia.
Why do insects have an open system but not e.g. fish and
mammals?
Insects are small ‐ blood doesn’t have to travel far.
Larger organisms use blood to transport O2 and CO2 (insects don’t) ‐ the blood is at very low pressure and so flows too slowly to provide enough O2 to more active organisms like mammals.
What are features of a closed circulatory system?
From the heart, blood is pumped through a series of progressively smaller vessels. In the smallest, the capillaries, substances exchange by diffusing in and out of the blood and into cells (and waste visa versa).
Blood is then returned to the heart via a series of progressively larger vessels.
Why is a closed system more suitable for larger organisms like fish and mammals?
Blood stays at a higher pressure in the vessels and so flows faster ‐ delivering e.g. oxygen and removing waste more quickly.
Tissue fluid bathes cells instead.
Explain the meaning of a single circulatory system.
Blood passes through the heart once for each
circuit of the body e.g. fish.
Explain the meaning of a double circulatory system.
Blood flows twice through the heart for one circuit of the body. Contains a pulmonary circuit and a systemic circuit e.g. mammals.
Pulmonary circuit
Carries blood to lungs to become oxygenated.
Systemic circuit
carries blood containing oxygen and nutrients to the body’s cells.
Advantages of double circulatory systems
- Blood can be maintained at a higher pressure in the systemic circuit, so it is delivered more quickly.
- A slightly lower pressure can be maintained in the pulmonary circuit to prevent damage to capillaries of the lungs.
- Mammals are much more active than fish and also maintain their own body temp ‐ both requiring a lot of energy and therefore a good and quick supply of oxygen and glucose to cells.
- As fish are less active and don’t maintain their body temp, a single circulatory system is sufficient to supply enough oxygen and glucose to meet their energy requirements.
Describe the external features of the heart
- Made out of cardiac muscle.
- Most of heart is the 2 ventricles ‐ very thick walls of muscle.
- Above the ventricles are the atria with thinner walls.
- Coronary arteries lie over the surface of the heart ‐ supply the cardiac muscle with oxygen for aerobic respiration.
- If the coronary artery becomes blocked it restricts blood flow and therefore delivery of oxygen to the muscle. This can cause myocardial infarction (heart attacks).
- At the top of the heart are the arteries (carry blood away) and veins (carry blood towards).
- The bottom of the heart that comes to a point is called the apex.
Describe the internal features of the heart
Semi-lunar valves:
- At base of arteries:
‐ prevents blood flowing backwards into the heart when ventricles relax (as the pressure would be lower there).
AVV:
Prevents blood flowing backwards from ventricles to atria.
Ventricular septum:
- Stops oxygenated and deoxygenated blood mixing;
- Ensures oxygenated blood gets to the body
- There would be a possible drop in blood pressure if hole present.
Explain the differences in thickness of the walls of the different chambers of the heart in terms of their functions.
- The muscle in the walls of each chamber contracts to increase the pressure in the blood.
- The higher the pressure, the further the blood will travel.
- The pressure in the arteries is produced by the contraction of the left ventricular walls.
- Atrial walls ‐ thinnest ‐ don’t need to create high pressure as the blood only needs to be pushed into the ventricles.
- Right ventricular wall ‐ thicker than atria ‐ needs to create enough pressure to pump blood to lungs (pulmonary system). Pressure must not be too high otherwise thin capillary walls in lungs could burst.
- Left ventricular wall ‐ thickest ‐ needs to create most pressure to pump blood through aorta to whole body (systemic system) which is a much greater distance than any other chamber.
What is the cardiac cycle?
The sequence of events in 1 heart beat.
What are the 3 stages of the cardiac cycle?
- Diastole (atria and ventricles relax)
- Atrial systole (atria contract)
- Ventricular systole (venticles contract)
Describe Diastole
- atria and ventricles relax and recoil.
- blood flows from veins into atria.
- pressure in ventricles is lower than in atria.
- blood flows through open A‐V valves into ventricles.
- volume in atria and ventricles increase.
- pressure in atria and ventricles slowly increases.
Describe Atria systole
Both atria contract.
Causes further increase in pressure in the atria.
Increase in pressure causes blood to be pumped through the open A‐V valves into the ventricles.
Causing the volume in the ventricles to increase.
