The earliest animals were marine invertebrates, that is, vertebrates came later. Animals are multicellular eukaryotes, and are … See more

Invertebrates are grouped into different phyla. Informally phyla can be thought of as a way of grouping organisms according to their body plan. A body plan refers to a blueprint which describes the shape or morphology of … See more

Sponges are animals of the phylum Porifera (Modern Latin for bearing pores ). They are multicellular organisms that have bodies full of pores and channels allowing water to circulate through them, consisting of jelly-like … See more

Cnidarians (Greek for nettle) are distinguished by the presence of stinging cells, specialized cells that they use mainly for capturing prey. Cnidarians include corals, sea anemones, jellyfish and hydrozoans. They form a … See more

Worms (Old English for serpent) typically have long cylindrical tube-like bodies and no limbs. Marine worms vary in size from microscopic to over 1 metre (3.3 ft) in length for some marine polychaete worms (bristle worms) … See more