Marine Invertebrates

What are the four main types of skeletal structures in invertebrates?

1) Skeleton made of calcium, silica, and organic fibres (Sea sponges);

2) Skeleton of interlocked calcium-carbonate plates and spines (Sea stars and urchins);

3) Skeleton made of chitin (arthropods);

4) Skeleton made of a calcium-carbonate shell (many molluscs).

What does symmetry describe in animals?

The balanced distribution of an animal's parts around an axis.

What is bilateral symmetry?

Body parts are arranged in the same way on their left and right sides (most animals).

What is radial symmetry?

Body parts are arranged in a circle around a central axis.

What is asymmetry?

Body parts are shaped irregularly and can't be split into equal parts.

Name the major phyla of invertebrates.

Porifera, Cnidaria, Nematoda, Platyhelminthes, Annelida, Mollusca, Echinodermata, Arthropoda.

What are the characteristics of Poriferans?

Pore bearing animals, asymmetrical, simple body form supported by spicules, no true organs, body made of canals through which water is pumped by ciliated cells.

What Phyla do animas belong to with the following characteistics?

▸Radial symmetry

▸Animals can be attached (coral) or free swimming medusa (jellyfish).

▸Mouth is surrounded with tentacles that have nematocysts.

▸Reproduce sexually and asexually.

Cnidaria

How do Cnidarians reproduce?

They reproduce sexually and asexually.

What are the characteristics of Platyhelminthes (Flatworms)?

Bilateral symmetry, unsegmented, distinct body and head, free swimming or parasitic, most are hermaphroditic.

What are the characteristics of Nematoda (Roundworms)?

Bilateral symmetry, unsegmented elongated bodies, complete digestive tract (mouth and anus), free living or parasitic, separate sexes.

What defines Annelids (Segmented Worms)?

Bilateral symmetry, segmented body parts, free living, hermaphroditic or separate sexes.

What are the main features of Molluscs?

Bilateral symmetry, unsegmented soft skin, most protected by a shell, complete digestive tract, specialized feeding organ (radula), gas exchange through gills.

What are the characteristics of Echinoderms?

Radial symmetry, spiny skin, tube feet, endoskeleton made of calcareous plates (ossicles), no distinct head or brain, can regenerate lost appendages.

What defines Arthropods?

Bilateral symmetry, segmented bodies, jointed legs, exoskeleton made of chitin, complete digestive tract, central nerve cord, open circulatory system.

Cnidaria

Corals, anenomes, jellyfish

Platyhelminthes

Flat worms

Nematoda

Round worms

Annelida

Bristle worms, leeches

Mollusca

squid, octopus, clams, snails, nudibranchs, clams, mussels

Arthropoda

Lobster, crayfish, crabs, prawns, copepods

Echinodermata

Sea stars, urchins, sea cucumbers

Porifera

Sea sponges