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INVERTEBRATES

INVERTEBRATES

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What are invertebrates?

• Invertebrates are the most abundant organisms on earth.
• They can be crawl, fly, swim or float.
• Invertebrates don't have backbone.

Characteristics of invertebrates

• The main characteristic is they do not have the spinal column and backbone.
• They are multicelluar organisms.
• Some invertebrates are slow and small in nature.
• The invertebrates can not occupy mulitple environments, though they are found in the harshest of the environments.
• Invertebrates live all over the world in various habitats.
• Body is divided into three parts - head, thorax and the abdomen.
• They do not have lungs for respiration.
• Respiration is through skin.
• Some invertebrate groups have a hard exoskeleton.
• Most of them reproduce sexually by the fusion of the male and female gametes.

Invertebrates classification

Cnidarians

• Habitat.They are aquatic animals.
• Level of organization - They exhibit tissue level of organization.
• Digestion is extracellular and intracellular.
• Some cindarians like corals have skeleton composed of calcium carbonate.
• Locomotion - The body contains nerve network that allows movement of tentacles and body.
• Examples: Aurelia (medusa), Adamsia (polyp)

Annelids

• Habitat - They can be aquatic marine or fresh water; or terrestrial.
• Level of organization - They exhibit organ-system level of body organization and bilateral symmetry.
• Body is segmented in lots of parts.
• Locomotion - They have muscles which help in locomotion.
• Reproduction is sexual.
• Examples: Nereis, Pheretima (earthworm), and Hirudinaria (blood sucking leech

Echinoderms

• They live in the oceans.
• These animals have an endoskeleton.
• The mouth is present on the ventral side and anus on the dorsal side.
• This helps in locomotion, capture and transport of food and respiration.
• Reproduction is by sexual means.
• Example: Star fish, Sea urchin, Brittle star.

Molluscs

• Habitat - Molluscs are terrestrial or aquatic; they can be marine or fresh water.
• Body is covered by a shell.
• Body is unsegmented.
• The radula - Mouth of the molluscs contain tongue called radula.
• They have a soft and spongy skin
• They breathe through gills.
• These gills have respiratory and excretory in functions. Anterior head region has sensory tentacles.
• Example: Pila, Octopus, Pearl oyster, Loligo,

Miryapods

• They live in the ground.
• They have exosqueleton.
• The body have lots of segments.
• They have lots of legs.
• They have two antennae.