Do not have a backbone or an internal skeleton. Some invertebrates have an external skeleton or shell that protects their body. This is called exoskeleton.


Invertebrates are oviparous which means they are born from eggs.


There are six groups:


1.- Arthropods.- The largest group of animals on Earth. All of them have got an exoskeleton and segmented bodies. All of them have got legs. Some have got antennae and wings.


Insects – Arachnids - Crustaceans – Myriapods


2.- Molluscs.- The body of a mollusc is soft and muscular. Molluscs don’t have legs.


Gastropods – Bivalves – Cephalopods


3.- Worms.- Don’t have legs. They have long, soft and moist bodies. They are not protected by exoskeletons or shells.


4.- Echinoderms.- They have hard plates under their skin. Their bodies have radial symmetry. Echinoderms have a mouth at the centre of their bodies.


5.- Cnidarians.- They are aquatic animals and live mostly in the sea. Some of them are soft and others have an exoskeleton. All of them have tentacles that help them to capture food.


6.- Sponges .- They are aquatic animals. Sponges have soft, irregular bodies with no fixed shape. Sponges have a lot of pore, or holes, in their bodies.






Insects have got Antenna, Thorax, Abdomen & 6 legs

Crustaceans have got Antenna, Claw, Cephalotorax, Abdomen & 10 legs

Arachnids have got Abdomen, Cephalothorax & 8 legs

Myriapods have got Antenna, Segments & many legs *


* Fun Facts: Centipedes are kind of myriapods. They are elongated metameric creatures with one pair of legs per body segment. Despite the name, centipedes can have a varying number of legs from under 20 to over 300. Centipedes have an odd number of pairs of legs, e.g. 15 or 17 pairs of legs (30 or 34 legs).A key trait uniting this group is a pair of venom claws or forcipules formed from a modified first appendage. Centipedes are a predominantly carnivorous taxon.







Gastropods have one muscular foot.

Molluscs have no legs.

Gastropods can be Terrestrial or Aquatic. They have got tentacles and a shell.

Bivalves are aquatic and they have a shell.

Cephalopods are aquatic too and they have got tentacles.




Types of Symmetry


Bilateral Symmetry Insect: Grasshopper - Two planes

Radial Symmetry: Starfish – Five planes

Radial Symmetry: Jellyfish – More than five planes




1. Worms have hard bodies. True/False

2. Sponges are aquatic. True/False

3. Sponges live on the land. True/False

4. Jellyfish float in the sea. True/False

5. Corals live on rocks. True/False

(Answers: 1. F; 2. T; 3. F; 4. T; 5. T.)




Fish have a head, an elongated body and a tail. The body is covered with thin, shiny scales which protect it. Fish live in the water and use their fins and tail to move about. Fish breathe through gills located on the sides of their head. Gills enable fish to breath under water. They can extract dissolved oxygen from water.


Fish are oviparous. Female fish lay their eggs in the water. Baby fish, called fry, hatch from the eggs. Most fish are cold-blooded. This means that their body temperature depends on the environment. Fish can be herbivores, carnivores or omnivores.






They have a head, a trunk, limbs and a tail. Their bodies are covered with hard scales. Most reptiles are terrestrial, but few are aquatic. They need external heat, like heat from the Sun, to maintain their body temperature. For this reason, they are called cold-blooded animals.


All reptiles breathe through lungs. For this reason, aquatic reptiles, like crocodiles and alligators, cannot remain underwater for long. They come to the surface to breathe.


They are oviparous but female reptile does not nurture or care for her young. Most reptiles are carnivorous and capture live prey.





How do mammals breathe? (Through lungs)


Do you think polar bears eat plants? Do they hibernate? Why?

Bears eat berries, flowers, pine cones, mushrooms, insects and small mammals. Bears spend most of winter sleeping to save energy and keep warm.


Bats can fly but they are not birds. Why are they mammals? Because they are viviparous*


*Viviparous means that mammals are born from their mothers’ body


 Hippopotamuses and beavers are semi – aquatic mammals. Why?

Because they spend most of the day in water. Hippopotamuses live in rivers and lakes. Their ears, nose and eyes are on the top of their head. This allows them to see and breathe while the rest of their body is under the water. After sunset, a hippopotamus leaves the water and spends most of the night eating. Hippopotamuses are herbivores



Useful Videos
Useful Videos

Maths & Science
Maths & Science

Science Activities
Science Activities