Question

as multicellular organisms sponges jellyfish and earthworms all face the same challenge of getting nutrients and oxygen to cells. explain how each group overcomes this challenge highlighting the differences in their solution

Answer 1

Sponges adaptation- Sponges do not have specialised organs to do things! The shape of their body is a kind of adaptation because it is constructed with a central cavity so that maximum water could flow through it and bring them the nutrients. They feed by using specialised cells called choanocytes which has the flagellum. the flagellum helps in preying on bacteria and other food particles surrounding the sponges. Phagocytosis is a means of nutrition here. Bacteria which is smaller in size (less than 0.5micron) is captured by the choanocytes. Gas exchange, nutrition, circulation, excretion - everything happens through diffusion.. Sponge breathe by diffusion of gases through the pores they have in the body called Ostia. Since they are sessile they can't move for oxygen and nutrients. But they take these things from the surrounding water and animals. Once the water with diffused oxygen is spread in sponges body it diffuses oxygen inside whereas letting carbon dioxide outside (movement of gases from higher concentration to lower concentration)

Jellyfish adaptation- jellyfish do not have any specialised organs. their body wall is so thin that gases can diffuse through the body. through the gastrodermis, food and oxygen reach the jellyfish. it has tentacle with cnidocytes which have the toxin. it is used to capture the prey or as defence line. the gastrodermis lining the gastrovascular cavity helps in both diffusion and nutrient absorption.

earthworm adaptation- In earthworm, oxygen is taken in through diffusion. the oxygen present inside the earthworm is always lesser than the surrounding, so constantly they receive oxygen inside and the carbon dioxide is also expelled out. Air diffuses and dissolves through mucous of the skin which is then taken inside to the respiratory system where it pumps oxygen diffused blood to the head and other parts of the body. their movement is another adaptation which spreads the blood and oxygen everywhere. this is why the earthworms are always moist. If they become dry, they will suffocate. Worms have strong and muscular teeth at the anterior part called as prostomium through which it takes in the dead and decaying leaves. It is digested by the digestive system in the worm. the mouth is so strong that they can pull the leaves out.

Basically all the three uses diffusion for survival.