1. Natural Sciences Grade 7
Term 1: Life and Living
Biodiversity
(PPT 4)

2. Diversity of Animals: Invertebrates
Topic 2 Biodiversity
Diversity of Animals: Invertebrates
Natural Sciences – Grade 7

3. Natural Sciences - Grade 7
Invertebrates
Animals with no backbones.
There are many animals that belong to this group.
We will have a look at 2 phyla
arthropods
molluscs
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4. Invertebrates: Arthropods
All arthropods have jointed legs and an exoskeleton.
The exoskeleton contains chitin which makes it strong - it protects the soft tissues on the inside.
It provides a framework for muscles to attach to.
The body of arthropods are divided into segments.
3 examples of classes of arthropods are insects, arachnids and crustaceans.
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5. Natural Sciences - Grade 7
Arthropods: Insects
This group is very diverse – more than a million different species have been identified.
Examples: beetles, locusts, mosquitoes, bees and ants.
Insects are found in nearly all the different environments on the Earth.
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6. Natural Sciences - Grade 7
Arthropods: Insects
Insects have –
3 pairs of legs
1 pair of antennae on the head
a body that is divided into 3 sections:
head with sense organs: eyes, antennae and a mouth
thorax with legs and wings
abdomen that contains intestines and reproductive organs.
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7. Natural Sciences - Grade 7
Arthropods: Insects
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8. Arthropods: Arachnids
Arachnids consist of over different species.
Examples: spiders, scorpions, harvestmen, ticks and mites
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9. Arthropods: Arachnids
Arachnids have –
4 pairs of legs
no antennae on the head
a body that is divided into 2 sections:
head and thorax (cephalothorax) which is joined into one section;
it carries sense organs, a mouth and legs.
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10. Arthropods: Arachnids (spider)
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11. Arthropods: Crustaceans
There are about different species of crustaceans.
Examples: crabs, lobsters, crayfish, shrimp, krill and barnacles.
They look very different from each other, even though they belong to the same group.
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12. Arthropods: Crustaceans
Crustaceans have –
5 or more pairs of legs
2 pairs of antennae on the head
a body that is divided into 2 sections, but sometimes also 3 sections
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13. Arthropods: Crustaceans (crab)
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14. Invertebrates: Molluscs
Molluscs have soft bodies, for example snails.
They have a head and a foot region.
The body is covered by a hard shell.
The large majority of molluscs live in the sea.
Molluscs range from species that are
microscopically small to the giant squid.
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15. Invertebrates: Molluscs (land snail)
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16. Natural Sciences - Grade 7
This is a simplified classification of the animal kingdom.
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