Description of invertebrate animals

1. Invertebrates

2. Invertebrate
Characteristics
 Invertebrate animals have no inner
skeleton or backbone.
 SIZE: most invertebrate are very small,
but some are enormous, like the giant
squid.
 BODY COVERING: some invertebrate
bodies are protected by shells or
exoskeletons, but others have no covering

3. Invertebrate
Characteristics
 BODY SHAPE: most invertebrates are
symmetrical:
- Bilateral symmetry: two identical halves or planes
- Radial symmetry: several planes of symmetry
- Asymmetry: the body has no symmetry. It is
irregular

4. WHERE AND HOW
INVERTEBRATES LIVE
 Many invertebrates live in the sea, but
some live in fresh water, and others on
land.
 Most invertebrates can move. However,
some don’t move: they attach themselves
to rocks or the sea floor. Parasites live
inside of other animals and harm them
 Most invertebrates are oviparous. A larva
hatches from an egg.

5. INVERTEBRATE
GROUPS

6. Sponges
Sponges: have irregular bodies and no symmetry.
They cannot move around. They attach themselves to rocks or
the sea floor. They filter seawater and retain the nutritive
substances for food.

7. Cnidarians
Cnidarians: have jelly-like bodies with radial symmetry. They
have tentacles. They are marine animals. Some, like coral and
sea anemone, attach themselves to rocks. Others, such as
jellyfishes, can move about
.

8. Worms:
Flatworms,
Roundworms,
and Segmented
worms
Worms have soft bodies with
bilateral symmetry. Some are
cylindrical, but others are flat.
Some worms are aquatic and
others are terrestrial. Many are
parasites

9. Echinoderms
Echinoderms have five-way symmetry. They
have a skeleton made of hard plates, often
with spines. They are covered by a thin skin.
All are marine animals

10. Molluscs
Molluscs have a soft body with bilateral
symmetry. Many are covered with one
or two shells.

11. Arthropods
Their bodies are totally
covered by an articulated
exoskeleton, like armour.
Some are aquatic and
some
others
are
terrestrial

12. GROUP OF ARTHROPODS
CHARACTERISTICS:
- The exoskeleton is like a human skeleton, it
protects the body, but it is external.
- The exoskeleton is rigid, so from time to time the
arthropod moults ( changes the skin) and grows a
new one. This process is called moulting.
- Arthropods sense organs are well developed. They
have antennae and eyes. The eyes can be simple or
compound. Compound eyes are made up of
thousands of smaller, simple eyes.
- Insects, arachnids, crustacean and myriapods
are arthropods.

13. GROUP OF ARTHROPODS
INSECTS
Insects are the most numerous animal group. An
insect body id divided into three parts: head,
thorax and abdomen. The head has a mouth,
two eyes and two antennae. The thorax has six
legs. Many insects have wings on the thorax

14. GROUP OF ARTHROPODS
INSECTS II
Insects can live everywhere except the open
sea. They eat many different types of food.
Some insects, like bees or silkworms, produce
substances which are useful for people.
Others are harmful, they cause illness,
destroy crops or spoil food.

15. GROUP OF ARTHOPODS
ARACHNIDS
These arthropods have eight legs. An arthropod body is
made up of two parts: the abdomen and the
cephalothorax.
Scorpions and spiders are arachnids. Most are terrestrial,
and some are carnivorous. They hunt and eat other animals.

16. GROUP OF ARTHOPODS
CRUSTACEAN
Most crustaceans are
aquatic. Many have ten
legs, two pairs of
antennae and compound
eyes.
The body is made up of
two parts: abdomen and
the cephalothorax.
Many crustaceans are used
for food: lobster,
shrimp and crabs, for
example

17. GROUP OF ARTHOPODS
MYRIAPODS
These arthropods have long bodies
made up of many identical segments.
Each segment has one or two pairs of
legs. The head has two short
antennae
CENTIPEDE

18. GROUP OF MOLLUSCS
They have soft bodies protected by one
or more shells.
Most molluscs are aquatic, but a few
live on land.
There are three principal groups of
molluscs:
Gastropods, bivalves and cephalopods

19. GROUP OF MOLLUSCS
GASTROPODS I
Gastropods have a head with four tentacles, where
the sense organs are located. They have one foot
to move. Marine gastropods eat algae, but most
terrestrial gastropods are herbivores
Most gastropods have one spiral shell which
protects their internal organs. Some, however,
have no shell: slugs, for example.

20. GROUP OF MOLLUSCS
BIVALVES
Bivalves have a shell made up of two
articulated valves. The valves can
open and close. Bivalves have a soft
body, but no head
Some bivalves, like mussels, attach
themselves to rocks on the ocean
floor. Other like oysters, move
around.
To obtain food, bivalves filter salt
water and retain the nutritive
substances

21. GROUP OF MOLLUSCS
CEPHALOPODS
Cephalopods have a well –developed
brain. They have eight or ten
tentacles.
All cephalopods are marine. They
move their body and expel water
to go from one place to another.
Some of them have a very small
internal skeleton, called a
cartilage.
Cephalopods are carnivorous, they
capture their prey with the
tentacles