Transport in animals
Why do large animals require a specialized transport system?
small surface area : volume ratio
large size
high metabolic rate/ activity
longer diffusion distance
A small SA:V ratio = longer diffusion distance. A specialized transport system is required for them to meet demands for their high metabolic rate.
A short diffusion distance allows for the transport of oxygen to respiring cells at a faster rate due to high metabolic activity and removal of carbon dioxide and urea at a constant rate through the process of excretion.
The heart contains:
Pulmonary circuit: Blood flows from the heart to the lungs.
Systemic circuit: Blood flows from the heart to the body cells.
Single circulatory system= Blood flows through the heart once passing through each circuit once.
Double circulatory system= Blood flows through the heart twice passing through each complete circuit.
Mammals have a double circulatory system because they have a high metabolic rate. Blood pressure must not be too high in the pulmonary circuit as it can damage the tiny capillaries leading to the lungs. Systemic circulation has a higher blood pressure than the pulmonary.
Advantages of a double circulatory system:
Higher blood pressure is maintained.
Rate of diffusion of oxygen and nutrients into respiring body cells increases.
Efficient removal of waste products such as CO2 and urea through excretion.
Allows deoxygenated blood to be separated from oxygenated blood in the body separated by septum.
Maintain internal bodily temperature + steeper concentration gradient.
Disadvantages of a single circulatory system:
Lower blood pressure due to thin-walled, narrow capillaries.
Slower rate of diffusion.
Deoxygenated and oxygenated blood is mixed (not separated by septum).
Less efficient transport means.
Rate of oxygen and nutrients supplied to respiring body cells decreases.
Rate of removal of waste products decreases.
Insects:
Single circulatory system, open heart structure.
Made up of tubular.
Haemolymph
Made