The water vascular system of a sea star enables movement, digestion and respiration through the use of water to exert force on limbs known as tube feet. The vascular system is primarily water but also contains coelomocytes, protein and potassium salts.
Answer: Well, populations never evolved than one human might have gone extinct due to many different viruses and sicknesses but other animals might not be extinct. If populations never grew more then that would be because we could not overpower dome viruses. If we never. If we never evolved animals like a Carrier pigeon would not be dead or extinct today.
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Explanation:
Wind t Water + Season changing
Answer:
Invertebrates are the organisms in which backbone or vertebral column is absent.
The three macroinvertebrate categories are annelids, mollusks and arthropods.
Annelids are the organisms having segmented body. They are found in moist places. Examples are leeches and earth worms.
Mollusks are the organisms which are enclosed in a calcium carbonate shell. Examples are snails and slugs.
arthropods are the invertebrates which have segmented body and jointed appendages. Examples are insects and crustaceans etc.