Science 4º

The vertebrates animals are those that have a backbone and an internal skeleton. Most of them

have tail. There are five groups of vertebrates: mammals, fish, birds, reptiles and amphibians.

In each group, animals have common characteristics.

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Animals

Mammals

✓ They have hair or fur.

✓ They breathe with lungs and they

usually have four legs.

✓ They born from their mother’s

womb.

✓ They feed their babies with milk.

✓ Most of them live on land, but

some of them live in water

(dolphins or whales) and one of

them can fly (bat).

Birds

✓ They are covered with feathers.

✓ They have beak and two wings.

✓ They breathe with lungs.

✓ They have two legs.

✓ They born from eggs.

✓ Most of them can fly, but some of

them cannot (penguin or ostrich).

Lungs!

They have milk!

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Fish

✓ They are covered with scales.

✓ They breathe with gills and they

use fins to swim.

✓ They born from eggs.

✓ They live in water.

✓ Some of them only can live in

salt water (sea) and others in

fresh water (lakes or rivers).

Reptiles

✓ They are covered with scales.

✓ They have a dry skin.

✓ They breathe with lungs.

✓ Most of them have four legs, but

some of them have no legs

(snakes).

✓ They born from eggs.

✓ They can live on land and in

water.

Fins!

Lungs!

Some of them have no legs!

Science 4ºAnimals

Amphibians

✓ They have a moist skin.

✓ They breathe with gills when

they are young, but later they

develop lungs.

✓ They born from eggs.

✓ They can live on land and in

water.

✓ They have four legs.

Adults: Lungs!

Life cycle of a

frog

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Life cycle of a frog

When they are young, they are aquatic

animals, so they have gills to breathe.

During metamorphosis, their gills

close and they develop lungs.

Adult amphibians can also absorb

oxygen and expel carbon dioxide

through their moist skin.

Science 4ºAnimals

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Unlike plants, animals cannot make their own food. They obtain energy eating other living things

and, for this reason, they are called consumers.

There are three types of consumers.

Herbivores

They only eat plants.

Some herbivores, like cows or sheep, are

ruminants. They eat the grass and is partly

digested in the digestive system, but then it

returns to the mouth. The animal chews the

grass to break it down more and swallows it

again. The grass return to the digestive

system where the process is completed.

Carnivores

They only eat meat.

Some carnivores, like vulture, are

scavengers. They are animals that feed on

dead animals that have died from causes

different than predation.

Scavengers eat carrion.

Omnivores

They can eat plants and meat.

Most of omnivore animals are mammals,

birds and fish.

They have different types of teeth and birds

have different types of beaks depending on

the food they eat.

Goat

Rhino

Sea turtle

Science 4ºAnimals

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When an animal reproduces, it creates a new living thing which is similar to itself. This is called

offspring.

Reproduction is very important because if a species doesn’t reproduce extinct.

Oviparous

Birds, reptiles, amphibians and fish are

oviparous animals. The embryo grows

inside an egg. The egg contains all the

nutrients embryo needs to grow.

These eggs will later hatch into new

offspring.

Mammals that are oviparous are called

monotremes. For example, the platypus.

Viviparous

Almost all mammals are viviparous.

The embryo develops inside the mother and

it gives birth to live offspring.

All baby mammals, including monotremes,

drink their mother’s milk until they can

find their own food.

Ovoviviparous

A few species are ovoviviparous.

These animals produce eggs but the eggs

develop and hatch inside their mother.

Later, the mother gives birth to live

offspring. Some fish, reptiles and

amphibians are ovoviviparous.

Turtle offspring

Cheetah offspring

White shark is ovoviviparous

Science 4ºAnimals

The invertebrates animals are those that haven’t a backbone or an internal skeleton. We going to

study five groups of invertebrates: arthropods, molluscs, cnidarians, echinoderms and sponges.

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Insects

They are the most numerous group of animals

in the world.

✓ Their bodies have three parts: head, thorax

and abdomen.

✓ They have two antennae.

✓ They have three pairs of legs joined to the

thorax.

✓ Most of them have one or two pairs of wings.

Arthropods is the largest invertebrate group and all of them have an external

skelenton called exoskeleton. However, they have some important differences

between them. There are four different groups of arthropods.

Arachnids

✓ Their bodies have two parts: cefalothorax

and abdomen.

✓ The cefalothorax is made up of the head and

the thorax.

✓ They have four pairs of legs and up to eight

eyes.

Antennae Head

Six legs

Abdomen

Wings

Thorax

Eight legs

AbdomenCefalothorax

Science 4ºAnimals

All invertebrate animals are oviparous and they can be carnivores, herbivores or omnivores.

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crustaceans

✓ Most of them have two body parts: a

cefalothorax and an abdomen.

✓ Their exoskeleton is very hard, like a shell.

✓ They have five pairs of legs but the front pair

of legs have claws.

✓ They also have four antennae.

MYRIAPODS

✓ They have a long, thin and segmented bodies.

✓ They have many pairs of legs and two

antennae.

✓ They live in dark and damp places.Many pairs of legs

Segmented bodyAntennae

Ten legs

Claws Antennae

Abdomen

Cefalothorax

Molluscs are another large group of invertebrates. In this group, we can find three different

subgroups distinguished from themselves depending on the number of shells.

All of them have a soft body.

Gastropods

The have one shell.

Bivalves

The have two shell.

Cephalopods

The have a internal shell.

Science 4ºAnimals

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✓ They have a soft and jelly-like body with one

opening.

✓ This opening is surrounded by venomous

tentacles.

✓ They live in the sea and the ocean.

✓ Jellyfish are cnidarians

✓ They are covered by a hard and spiny skin.

✓ They live at the bottom of the sea.

✓ They have like a tiny feet to move about.

✓ Starfish are echinoderms.Tiny feet

Hard and spiny skin

Jelly-like body

Opening

✓ They are the simplest invertebrates.

✓ They live in water.

✓ They have no muscles, nervous system or

circulatory system.

Tentacles

Science 4ºAnimals