Why do platyhelminthes possess hydrostatic skeleton but lack coelom​

What is point source pollution of an aquatic ecosystem? a) pollution of freshwater sources b) pollution from many sources that combine into one c) pollution that occurs over a wide area; water that runs off from fields, parking lots, and other land surfaces d) pollution that can easily be identified with a single discharge source, such as an open pipe which drains into a body of water

Dr. arenas is a scientist who has been trying to determine if increasing pressure will increase the sound that occurs when two chemicals explode. it measures the volume of the sound that occurs at the minimum pressure at which the explosion will occur. it then increases the pressure and measures the volume of the explosions that occur. what kind of investigation is the scientist conducting?

Which of the following is the smallest unit that would contain a complete copy of the entire human genome? a) one human somatic cell b) one human chromosome c) all of the dna of one human d) one human gene