CHAPTER 3 | TRANSPORTATION

In simple organisms, the required substances of cells such as oxygen and nutrients go directly into the cells by diffusion through cell membranes.

Complex organisms such as humans, vertebrates and multicellular plants have specialised transport systems.

The ‘dub’ sound is produced by the closing of the semilunar valve in the aorta and pulmonary arteries (diastole).

The reading of blood pressure that flows and fills the heart is called diastolic pressure reading.

The ‘lub’ sound is produced by the closing of tricuspid and bicuspid valves between the atrium and the ventricle (sistole).

The reading of blood pressure that flows out of the heart is called systolic pressure reading.

pulse rate is produced by shrinkage and relaxation of the muscular wall of the arteries.

Physical activities, gender, age and health condition affect the rate of pulse

Blood consists of plasma, red blood cells, white blood cells and platelets.

Blood consists of blood cells that float in a fluid called plasma.

Plasma contains dissolved substances such as minerals and digested foods.

There are four human blood groups, i.e. A, B, AB and O.

Blood transfusion is the transfer of blood from a donor to a recipient.

The type of blood transfused to a recipient must be compatible to avoid agglutination.

Blood groups A and B contain antigen A (antibody Anti-B) and B (antibody Anti-A) respectively.

Blood group AB contains both antigen A and B but there is no antibody Anti-A or B. 6. Blood group O does not contain any antigen but the antibodies Anti-A and B are present.

Transpiration is a process in plants through which water is lost in the form of water vapour by evaporation from the stomata (opening) of the leaves of plants.

If the temperature of the environment increases, the rate of transpiration will also increase. The rate of transpiration will drop on a cold or overcast day.

High light intensity increases the rate of transpiration. This is because plants carry out photosynthesis when the stomata are open.

Wind or moving air increases the rate of transpiration. Wind causes water to evaporate faster from the surface of leaves.

Dry air increases the rate of transpiration. The drier (lower humidity) the air in the surroundings is, the faster water will evaporate from the plant.

Transpiration removes excess water from a plant. In this way, the concentration of the cell fluid can be controlled. Besides, transpiration helps to transport water and minerals from the roots to the whole plant.

Other than water loss from plants through transpiration, water is also lost from plants through exudation or guttation.

Exudation or guttation is the water loss from plants in liquid form through hydathodes that are always open at the edges of the leaves.

Guttation usually occurs at night or when the air humidity is high

Guttation is different from dew drops. Dew drops are formed from the condensation process of water vapour in the atmosphere into water.