Tuesday 22 May 2012

IS THE SEA SPONGE A PLANT OR ANIMAL?






The sea sponge is classified as an animal, albeit simple in make up.  This is because there are some key characteristics that defines the sea sponge as an animal, rather than a plant.

Their scientific name is Porifera, meaning animals that have pores. There are more than 15,000 varieties, and they live primarily in the ocean, some near the edge, some in deep water, some in fresh water.

The main reasons for classification of sea sponges as animals is outlined below:
  • All plants carry out photosynthesis, but sea sponges do not.  Instead they carry out cellular respiration typical of animals.  
  • Sea sponges do not have cell walls or chloroplast typical of plants, but contain animal cells.
  • However, like a plant, they do attach themselves to rocks, reefs and the ocean floor by rooting themselves to a spot.  This trait is shared by other animals such as mussels, coral and sea anemones.
  • Sea sponges lack a brain and have no true tissues, lacking muscles, nerves, and internal organs. Lacking a brain is not unique in the animal kingdom, and sea sponges share this trait with other creatures such as jellyfish and starfish.
  • Unlike plants, seas sponges have a skeleton. This is made of Calcium Carbonate, Silicon Dioxide or spongin protein.
  • Since it doesn't have much in the way of body functions, such as a digestive, nervous, or even circulatory system, it survives by filtering water through itself and eating the bacteria and microscopic organisms found there for food. It has a specialised cell called the choanocyte which forms an very basic digestive system 

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