Question

(a) What is lymph?
(b) Draw a labelled diagram of human excretory system.
(c) How plants excrete waste products? Explain.

Answer 1

(a)

Lymph is a colourless, mobile fluid connective tissue. It is the tissue fluid that slowly drains into the lymphatic capillaries from the intercellular spaces. The small lymphatic vessels undergo continual rhythmic contractions, the pumping action of which causes a slight negative pressure to develop. This pressure draws the tissue fluid into the lymphatic capillaries. The lymph is usually a clear, transparent fluid. It consists of two parts;' a fluid matrix, the plasma, in which float the amoeboid cells, the leucocytes.

(b)

Human excretory system consists of a pair of kidneys, a pair of ureters, urinary bladder and urethra. The diagram is given above.

(c)

The removal of toxic and waste products from the body is known as excretion. Excretion in plants is a simple process as they lack specialized excretory organs. The major excretory products in plants include the carbon dioxide and water which are formed during respiration and nitrogenous compounds formed during protein metabolism. They also produce oxygen during photosynthesis. The gases are removed through the stomatal pores in leaves. The water is continuously eliminated by the process of transpiration. The plants also produce organic waste products such as gums, resins, tannins , oils etc. which are stored in various plant parts such as barks, stem and leaves. Ultimately the shedding of these plants parts takes place. Thus, excretion in plants is carried out by diffusion, storing and transpiration.