Download Arthropods Natural Sciences - Grade 7

Natural Sciences
Grade 7
Term 1: Life and Living
Biodiversity
(PPT 4)
Topic 2
Biodiversity
Diversity of Animals:
Invertebrates
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
Natural Sciences - Grade 7
Invertebrates: Arthropods
• All arthropods have jointed legs andan
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.
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.
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.
Natural Sciences - Grade 7
Arthropods: Insects
Natural Sciences - Grade 7
Arthropods: Arachnids
• Arachnids consist of over 100 000 different
species.
• Examples: spiders, scorpions, harvestmen,
ticks and mites
Natural Sciences - Grade 7
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.
Natural Sciences - Grade 7
Arthropods: Arachnids (spider)
Natural Sciences - Grade 7
Arthropods: Crustaceans
• There are about 67 000 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.
Natural Sciences - Grade 7
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
Natural Sciences - Grade 7
Arthropods: Crustaceans (crab)
Natural Sciences - Grade 7
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.
Natural Sciences - Grade 7
Invertebrates: Molluscs (land snail)
Natural Sciences - Grade 7
Natural Sciences - Grade 7