Invertebrates

INVERTEBRATES

Natural Science 1 ESO.

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The main

characteristics of invertebrates are:

They are

multicellular.

They don’t

Most

have

an internal

of them reproduce

skeleton.

sexually.

Most invertebrates can move Most invertebrates are organized in a way called symmetrical.

Invertebrates are

heterotrophic.

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Invertebrates can be classified into eight groups: PORIFERA

CNIDARIA

PHATYHELMINTHES

NEMATODES

ANNELIDS

MOLLUSK ECHINODERM

ARTHROPODS

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HOW DO YOU KNOW IT IS A PORIFERA? It is a porifera because...

 Sponges are simplest of all animals with many cells.  Their body is perforated by pores.  They have an internal cavity with an upper hole called osculum.

 They are filtering animals. They feed filtering water and retaining food particles.  They can reproduce sexually or asexually (fragmentation).  Sponges move when they are very young and very small. Once they settle down they don't move anymore.  Includes marine & freshwater sponges. .

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HOW DO YOU KNOW IT IS A CNIDARIA?

It is a cnidaria because...  They Have 2 basic body forms Swimming medusae and Sessile polyps: a bag shape fixed to the ground. 

They have a mouth with tentacles with stinging cells called cnidocytes.

 They have a gastrovascular cavity, a body cavity with a single opening to the outside; it functions as a digestive system.  All carnivorous.  They can reproduce sexually or asexually (budding).  Includes marine organisms such as jelllyfish, coral, sea anemone.

Hydra is a freshwater cnidarians.

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HOW DO YOU KNOW IT IS A WORM?

It is a worm because...

Worm includes animals with a soft, elongated body, bilateral symmetry.

Three types:

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HOW DO YOU KNOW IT IS A MOLLUSK?

It is a mollusk because...  They are soft-bodied animals.  They have bilateral symmetry.  They usually, but not always, have a shell, which is secreted by a body wall called the mantle. Many mollusks have a tongue, called a radula.

 They have a "muscular foot" that is used to move around, excavate or catch the prey. 

They are the second-largest group of invertebrates, with 50,000 living species.



They live in ocean, freshwater and terrestrial habitats.



They include snails, slugs, octopus, squid, mussels, oysters, etc. The Giant Squid and the Colossal Squid are the largest animals without a backbone.

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Mollusc functions: 

Respiration. They breathe through lungs (terrestrial) or gills

(aquatic). 

Nutrition. Carnivores and herbivores.

 Reproduction. Most are hermaphrodite and oviparous.

Three groups: Bivalves Their shells have two valves.

Gastropods They have a spiralshaped shell with a

Cephalopods They have tentacles, but not shell.

single valve.

clams

Snails

Squids

Oysters

Slugs

Octopuses

Mussels

Sea snails

Nautiluses

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HOW DO YOU KNOW IT IS AN ECHINODERM?

It is an equinoderm because...  They are marine animals.  Adults are radially symmetrical while larvae are bilaterally symmetrical.  They have hard skeleton, generally with spines .  They have an ambulacral system to move around. Tube feet are present for locomotion and respiration.

 They reproduce sexually or by fragmentation like starfish. Show very high power of regeneration.

Examples:

sea urchins

sea cucumber

brittle star

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HOW DO YOU KNOW IT IS AN ARTHROPOD?

It is an arthropod because...  They are the largest group of animals in the world. They live both in the ocean and on the land.  They have many different body shapes and sizes, but they all have: paired, jointed legs or appendages. a hard, armored exoskeleton that protects them and prevents water loss. bilateral symmetry.  They have a body divided into three parts: head, thorax and abdomen.

 In order to grow, arthropods shed their exoskeletons in a process called molting.

 They are oviparous. Some hatch as a larvae and undergo metamorphosis.

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1.What is the main difference between vertebrates and invertebrates?

2. True or false? a) Porifera live freely, floating on sea water. b) Porifera can reproduce sexually or asexually. c) Corals are porifera with the shape of a polyp. d) Cnidaria can reproduce sexually from eggs.

3. Complete this sentence.

Annelids’ bodies are…………. And divided into ………. or ……….. They live in ………

4. What is the main function of the exoskeleton?

5. Which system is exclusive to echinoderms? What is it used for?

6.True or false? a) The body of many echinoderms is covered by spines. b) Ambulacral system is used for reproduction. c) Echinoderms can reproduce sexually through eggs.

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7. Match each kind of invertebrate to its main characteristic. a) Mollusks

1.They have an ambulacral system.

b) Arthropods

2.They have pores.

c) Porifera

3.They have exoskeleton.

d) Annelids

4.The mouth is sourronded by tentacles

e) Echinoderms

5.Its body is very long and divided into segments.

f) Cnidaria

6. Most of them have a shell.

8. True or false? a) Echinoderms have an internal shell. b) All terrestrial arthropods breathe by lungs. c) All invertebrates have an endoskeleton. d) An annelid’s body is divided into rings.

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ENGLISH

CATALÀ

DEFINITION

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