1.5 To understand how animals and insects differ with regard to

Natural sciences

Ecosystems and the environmental balance

Educator section

Memorandum

Sequence:

B;

D;

C;

A

Leaner section

Content

Activity: to understand how animals and insects differ with regard to reproduction/life cycle [lo 2.3]

(i) Animals also differ with regard to their reproduction

Some young look just like the adults when they are born, while others first need to undergo a metamorphosis (change) before they look like the adults. Some animals undergo an incomplete metamorphosis, while others undergo a complete metamorphosis. A complete metamorphosis consists of the following stages: eggs are laid; larvae hatch; then they develop into pupae from which the adults finally develop.

Insects: fruit flies

Fruit flies belong to the Drosophila family and are used extensively as laboratory flies with which experiments are done. In nature, these flies sometimes cause extensive damage in fruit orchards if they are not combated early enough.

Adult fruit flies lay their eggs in the skin of the fruit, which then rot quickly and fall from the trees. The rotting fruit pulp is the source of food for the larvae that hatch. After a few days, the larvae crawl into the ground and change into a pupae. The mature fly appears from the pupa after about two to three weeks.

In order to combat the fruit fly, it is necessary to treat both the adult fly that contaminates the fruit in the trees as well as the soil under the trees, in which the pupae are, with pesticides.

Each female can lay 15 to 50 eggs per day and up to 900 eggs in a lifetime. The entire life cycle of the fruit fly lasts about two weeks. Before mating takes place, the male fly first needs to court the female. The female will accept him only if he is an adult and from the same species that she is. The female recognises a male from the same species by means of her senses of sight, hearing and smell.

Assignment 9

The following sketch represents the life cycle of the fruit fly, but in the incorrect sequence. Place it in the correct sequence and then draw your own sketch of the complete metamorphosis of the fruit fly.

Group assessment

Assessment

Learning Outcome 2: The learner will know and be able to interpret and apply scientific, technological and environmental knowledge.

Assessment Standard 2.3: We know this when the learner interprets information.