What are metazoans??

hi kartik ,Metazoan animals are multicellular, mitochondrial eukaryotes. Today Metazoa encompasses all animals with differentiated tissues, including nerves and muscles. They evolved from the protists approximately 700 million years ago. There are two prominent theories dealing with how the metazoans came to be, although one, the syncytial theory, has been somewhat discredited. The other, the colonial theory proposed by Ernst Haeckel in 1874 states basically that multicellular organisms have a colonial ancestor. This is in keeping with the idea that the choanoflagellates, a group of colonial protists, created the colonies from which multicelled organisms first evolved. This evolution occured sometime during the Precambrian period; the oldest known animal fossils were discovered in Precambrian rocks in 1946.

Hi Kartik Srivastav

Protozoa:

1. They are single celled organisms.

2. 2. A single cell performs all functions; therefore there is no division of labour.

3. They have a cellular grade of organization, e.g. Amoeba paramecium.

Metazoa:

1. They are multi-cellular organisms.

2. They show division labour as different cells or organs perform different functions.

3. They have cellular tissue, organ and system grade of organization, e.g Sponges to chordates.

Hope this might helps you.

All the Best.