Biology - Invertebrates

Invertebrate

An animal that lacks a vertebral column/ an animal without a backbone

Annelid

One of the phyla of the animal kingdom containing segmented worms (earth worms)

Cephalopod

One of the phyla of the animal kingdom containing squids, octopus and cuttlefish

Mollusc

One of the phyla of the animal kingdom containing slugs, squids and snails

Platyhelminth

One of the phyla of the animal kingdom containing flat worms

Hydrostatic skeleton

A fluid filled chamber surrounded by muscles that is commonly found in worms and other invertebrates

Hydrostatic skeleton working method

It works by using internal fluid pressure generated by muscle contractions to provide support and facilitate movement

Coelem

A long, hollow compartment running throughout the length of an earth worms body

Circular muscles

The muscle that encircles the coelom and when it contracts, the worm gets longer and thinner

Longitudinal muscles

The muscle that runs along the length of it and when it contracts, the worm gets shorter and fatter

Clitellum

Secretes an egg sac that surrounds the worm’s body then slips off

Chaetae

Tiny bristles that hold onto the earth to move

Siphon

Propels water for locomotion (pushes water out to move) and respiration

Jet propulsion

A movement that propels the squid by drawing water into the mantle cavity (when it flaps open) then forcefully expelling it from the siphon

Parasite

An organism that lives in or on another for its own benefit, usually to gain food

Tapeworms

Endoparasites in the platyhelminths phylum of invertebrates that live in the small intestine of many animals. They absorb nutrients directly through the body wall of the tapeworm by a process called diffusion