Is variation always caused by the surroundings?

Some variation is the result of differences in the surroundings, or what an individual does. This is called environmental variation.

Question:

Is variation always caused by the surroundings?

Some variation is the result of differences in the surroundings, or what an individual does. This is called environmental variation.

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organisms that lack symmetry are called asymmetrical and belong to phylum porifera/sponges.

organisms with specialized stinging cells belong to phylum cnidaria. stinging cells are called cnidoblast cells.

cnidarians show two morphological forms : polyp (sessile) and medusa (mobile)

filter feeding is observed in porifera members.  

alternation of generation is observed in coelenterata or cnidaria. there is alternation of asexual polyp form and sexual medusoid form. it is also referred as metagenesis.

your body is trying to warm itself up. or more precisely, sensors in your skin send messages to your brain to generate heat to your body.