Life Science: Invertebrates Worksheet and task

Invertebrates

Invertebrates are animals without backbones and can be divided into many different groups. Two of these groups are the arthropods and mollusks. Arthropods are the largest group of invertebrates. 85% of all animal species are Arthropods. The phylum Arthropods can also be divided into different groups, such as (a) insects, (b) arachnids, (c) crustaceans and (d) diplopods (sometimes also called myriapods).

There are more insects on earth than any other kind of animal and they occur almost everywhere. Here is a basic diagram of what an insects body looks like.

In order to classify a living organism as an insect you would use the following criteria.

 Insects have a hard, external skeleton.
 Their bodies are divided into a head, thorax and abdomen (three parts).
 The thorax and abdomen are divided into segments.
 They have six legs and the legs are all connected to the thorax.
 They have two feelers on their head and have two types of jaws.
 The head consists of two large compound eyes and three simple eyes.
 Insect breathe through holes called spiracles which are attached to tubes inside the body called tracheae.
 Insect lay eggs.
 Some insects are poisonous and they are usually brightly colored.

Now use the information in the previous pages and answer the following questions.

1. Name the three parts that the insect body consists of: …………………………………………………………….
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2. Which parts of the body are divided into segments?
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3. To which part of the body are the legs attached? …………………………………………………………….
4. How many legs do an insect have? ……………………………………………………………………………...
5. A typical insect has …………..………. types of jaws and two …………………………… on their heads.
6. Describe the eyes of an insect. ……………………………..…………………………………………………………………...
   ……………………………………………………………………………………………………………………………………………………..
7. Insects do not have lungs, but breathe by means of …………………………………… which are connected to tubes in the body called ……………………………………. .
8. Insects reproduce by ……………………………………………. .

The life-cycle of some common insects.
The young of insects look different from their parents. They develop by going through several different forms after they hatched. Their life-cycle changes from one stage to the other. We call this process metamorphosis.

The life cycle of a house fly.

Look closely at the life-cycle of the common house fly on page 3 and explain each of the different stages of its life-cycle in detail.
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The life-cycle of a butterfly.
Look at the following sketch and fill in the missing words.

Topic Task:
Study and show the life cycle of any insect which you find interesting. (e.g. mosquito, grasshoppers, ants, crickets, dung beetles, bees). You may have to do some research in the library in order to complete this task. (10 marks)

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