This document provides an overview of invertebrates, describing their key characteristics and how they are classified. It notes that invertebrates do not have an internal skeleton, and explores some of the main types including sponges, jellyfish, worms, arthropods, and molluscs. Arthropods are described as the largest and most important group of invertebrates, having an external skeleton and many legs. Within arthropods, insects are discussed in more detail, noting their three-part body structure.

1. UNIT1. INVERTEBRATES

2. INVERTEBRATES
Characteristics of invertebrates
- They eat otherliving things.
- Nearly all of them can move
from one place to another.
- They are oviparousbecause
they lay eggs.
Classifying of invertebrates
Invertebrates don´t have
INTERNALSKELETON.
Types of invertebrates
- Sponges
- Jellyfish
- Worms
- Arthropods
- Molluscs
- Echinoderms

3. ARTHROPODS
- Itisthe biggest and most
important group of
invertebrates.
- They have an EXTERNAL
SKELETONthat protects
their body.
- They also havemany legs.
- They can live on land, in
water andin the air.
Insects
-They are the largest groupof
arthropods.
-Their body isdivided into threeparts:
HEAD,THORAXand ABDOMEN.
-They have two ANTENNAEand
many WINGS.
-They have SIXLEGS
Arachnids
- Their body isdivided into two
parts: CEPHALOTHORAX(it is
formed by the head and thorax
combined) and ABDOMEN.
- They don´t have ANTENNAEor
WINGS.
Crustaceans
- The majority of crustaceans have
a body divided into two parts:
CEPHALOTHORAXand ABDOMEN.
- They have two ANTENNAEand
don´t have WINGS.
Antennae
Thorax
Wings
Abdomen
Legs
Cephalothorax
Antennae
Legs
Abdomen
Ant Ladybird Beetle
Grasshopper Butterfly

4. MORE INVERTEBRATES
Sponges
- They live at thebottom
of the sea.
- They are FIXEDto the
ground.
- Their body isfull of
holes, known asPORES
(Food andwater enter
their body through
these pores).
Jellyfish
- They can be very
dangerous animals.
- They have poisonous
TENTACLESthat they
use to hunt other
animals andto defend
themselves.
Echinoderms (Starfish
and urchins)
They have many small feet
that they use to move along
the bottom of the ocean.
Worms
- They have long soft
segmented bodies
that ismade up of
RINGS.
- Some of them live in
the ground and
others live inthe
water.
Molluscs
- They can live on land
(terrestrial)orinwater
(aquatic).
- They have SOFTMUSCULAR
BODIESto move along the
ground orwater.
- They have a SHELL.
- There are three types of
molluscs that have shells:
•Molluscs with two shells
which are calledVALVES.For
example: Mussels.
• Molluscs with one shell. For
example: Snails.
• Molluscs with aninternal
shell. For example: Squid.