Poriferans are animals that have numerous pores (i.e., pori) on their body. Generally we know them as Sponges. They may be either marine or freshwater animals. They have a body fixed witha a substratum like rock, wood etc. Examples- Sycon, Glass-rope sponge, Hexactenellida etc . Food enters through numerous body pores (ostia) and undigested matterexits through the single big axial pore (osculum)
Coelenterates are animals which have a body cavity as their digestive system (coel- body cavity or coelom; enteron- gut). These animals have numerous cnidoblast cells (spine cells) on their body. These animals are also called Cnidarians (cnidi-spines or thorns). Examples- Hydra, Obelia, Aurelia etc. Food enters through mouth (also called Hypostome) and undigested matter exits through it also.
ability of an extracellular solution to make water move in or out of a cell by osmosis is known as its tonicity.
A hypertonic solution is a particular type of solution that has a greater concentration of solutes on the outside of a cell when compared with the inside of a cell.
A hypotonic solution is a particular type of solution that has a lower concentration of solutes on the outside of a cell when compared with the inside of a cell.
A simple pendulum is represented by a mass of no size attached to an string of with no mass. A compound pendulum represents a real object that is swinging about a point other than its center of gravity. For the compound pendulum you need to know its mass, its moment of inertia about the pivot point.
Electrolytes are substances which, when dissolved in water, break up into cations (positively charged ions) and anions (negatively charged ions). We can say they are ionize. Strong electrolytes ionize completely (100%), whereas weak electrolytes ionize only partially (usually on the order of 1–10%).