Characteristics of living organisms
Monacia Williams, Contributor

Well here we are, together again for the second in our series of lessons. By now you would have met your new teacher and settled down in your biology class, ready to rekindle your fascination with this fantastic subject! Having done so, I promise that you will not be bored!

Last week, you were introduced to the general requirements of the subject, as well as the SBAs. This week, I want to remind you of a few facts that will help you in your quest to do well in this subject.

Remember when you learnt the characteristics of living things? I am sure you thought that you were just studying them for 'learning sake', however, this was not so, as these characteristics will form the basis of your studies over the next two years.

Let's remind ourselves of these characteristics. Living organisms:

1. feed

Plants feed on food that they have manufactured in photosynthesis and hence are known as autotrophs. Animals feed on already manufactured food and are known as heterotrophs.

2. respire

Respiration of the food that is consumed provides living organisms with the energy needed to carry out their activities.

3. excrete

Excretion rids the organism's internal environment of the waste material produced from the chemical reactions taking place there.

4. reproduce

Reproduction enables the organism to produce offspring, allowing the species to continue.

5. move

Animals move about to find food and mates, plants make their own food and have developed unique reproductive strategies which have reduced the need for movement. There are, however, unicellular plants which still retain this ability.

6. grow

They increase in both mass and complexity. Unlike the increase in non-living things, this increase is irreversible.

7. respond to stimuli

The response to stimuli is known as irritability and occurs as a result of changes in the organism's external environment.

Do not forget these characteristics, and do not continue to take them for granted because they form the basis for the following topics - nutrition, respiration, excretion, reproduction, growth, locomotion, coordination and control. You will be investigating these in more details as you continue your studies in biology.

Remember also that organisms do not live in isolation, but in close association with their own kind, with others that are of different kinds and also with the environment in which they live. In doing this, they form relationships, one of which is a feeding relationship.

Plants form the base of all feeding relationships because they are the only living organisms that are capable of converting the sun's energy to the chemical energy stored in the products of photosynthesis. The products of photosynthesis are the only sources of energy for living organisms, and because plants are the organisms that can convert the sun's energy, they are known as producers. All other organisms are, therefore, known as consumers.

Consumers are of different types:

• Primary consumers feed directly on plant material and are also known as herbivores
• Secondary consumers feed on the primary consumers and can be either carnivores or omnivores
• Carnivores are secondary consumers that are flesh eaters
• Omnivores are secondary consumers that feed on both plant and animals.

In our next lesson, we will continue to examine these relationships.

National top science teacher, Lillieth Wilson, instructs her grade-10 students. - FILE

Monacia Williams is a teacher of biology at Glenmuir High School.