Why porifera are considered as animal inspite of that they non-motile?

Porifera, also known as sponges, are indeed considered animals despite their sessile nature. While it is true that most adult porifera are non-motile, this characteristic alone does not exclude them from the animal kingdom. Here are a few reasons why porifera are classified as animals:

1. Multicellularity: Porifera are multicellular organisms, meaning they are composed of multiple cells that work together to perform various functions. This is a defining feature of animals, as opposed to single-celled organisms like bacteria and protists.

2. Heterotrophy: Porifera are heterotrophic, which means they obtain nutrients by consuming other organisms. They filter food particles from the water through their specialized body structures, such as choanocytes.

3. Cellular Organization: Porifera exhibit cellular organization, with different types of cells performing specific functions. These cells include choanocytes, pinacocytes, and archeocytes, each with distinct roles in the sponge's survival.

4. Reproduction: Porifera reproduce both sexually and asexually. Sexual reproduction involves the production of gametes (sperm and eggs), while asexual reproduction occurs through fragmentation or budding. This diversity in reproductive strategies is characteristic of animals.

5. Embryonic Development: Porifera undergo embryonic development, which involves the transformation of a fertilized egg into a complex multicellular organism. This developmental process is similar to that observed in other animal groups.

6. Lack of Cell Walls: Unlike plants and some protists, porifera do not have cell walls. This absence of cell walls is consistent with the animal cell structure.

While porifera's sessile lifestyle may set them apart from many animals, their multicellular nature, heterotrophy, cellular organization, reproduction, embryonic development, and lack of cell walls collectively support their classification as animals.