Classification of invertebrates

Q What are invertebrates? Give examples.A: Animals without backbones are called invertebrates. Ex jellyfish, spider and crabs don’t

have back bones.

Q How many kind of invertebrates are there on the earth?A: Almost 90% of all animals are invertebrates. There are about 1, 200, 000 kinds of

invertebrates.

What are the main groups of invertebrates?A: 1) Invertebrates with jointed legs. 2) Invertebrates without jointed legs.

Classification of invertebratesInsects, Arachnids, Molluscs

Insects: six legs, three body parts, eg ants, wasp, butterfly.

Arachnids: 8 legs, no antennae and two body parts. like spider, scorpion and ticks..

Crustaceans: have two pairs of antennae and more than four pairs of legs. Like woodlice, shrimps, crabs and lobsters.

Molluscs: have a muscular foot for movement and often have a shell. Like snails, octopus, slugs and

squids.

Protozoa: are single celled organisms with a cell membrane and a nucleus.

Types of protozoaSome protozoa are plant like and feed by photosynthesis

like euglena. Others are animal-like and feed on other organisms like amoeba and paramecium.

Differences between protozoa and algae

Coelenterates: are water invertebrates which have a body made up of two layers of cells, with only one body opening which act as both mouth and anus. This opening is usually surrounded with tentacles. Like hydra, jellyfish, corals

ans sea anemones.

Myriapods: are arthropods with one pair of antennae and an elongated body made up of numerous segments. Like centipedes have one pair of

leg per segment and millipedes have two pairs of legs per segment.

Flatworms: have unsegmented bodies. Like planarians, flukes, and tapeworms. Most tapeworm are bisexual means they contain both male and female reproductive organs.

Annelid worm: are segmented worms with round bodies. Like earthworms and leeches. Each segment is internally seperated from

the nextand has stiff bristles which are used as sense organ.

Echinoderms: are marine invertebraets which have spiny skins an sucker feet. These feet have water filled canals which provide hydraulic power movement, feeding and respiration.

Like starfish, sea urchins, sea cucumber and brittle stars.

Q Write the characteristics of invertebrates with jointed legs.A: 1) They have three body parts- head, thorax and abdomen. 2)

Have a hard skin on the outside called exoskeleton. 3) Have 6 legs.

Give examples of invertebrates without jointed legs.A: Three pair of legs = these are the insects. They form about 90% of all invertebrates. Ex butterfly, cockroach,

ants and praying mantis.Four pair of legs = Example spider and scorpion.

More than four pair of legs = Example shrimps, crabs, centipedes and millipedes.

Q Write the characteristic of an insect.A: Insects 1) have six legs. 2) have three body parts- head, thorax and abdomen. 3) have a

pair of feelers on their head. 4) Some have one or two pair of wings. Some don’t have wings.

Name some insects which don’t have wings.A : Ant and silverfish.

Name some insects which have one pair of wings.A: Housefly and mosquito

Name some insects which have two pair of wings. A: Butterfly and dragonfly.

Q Give examples of animals that have four pairs of legs.A: Spider and scorpion.

Q Give examples of animals that have more than four pair of legs.A: Shrimps, crabs, centipedes and millipedes.

Give examples of invertebrates without jointed legs.A: 1) Worm like animals a) Some of these have segmented body like earthworm. b) Others don’t have segmented body like flatworm. 2) Non worm like animalsa) Some have shells like snails and shellfish.b) Some do not have shells like jellyfish and starfish.

How are invertebrates useful?A: 1) They are important as food. 2) Some help to control garden pests.

3) Some like maggots can be used to heal wounds as they eat rotting flesh.