Biology - Excretion

Introduction

• The biological process that involves in the removal of the harmful metabolic wastes from the human body is known as excretion.

• Different species (organisms) use different processes for the excretion. E.g. many unicellular organisms remove their wastes by simple diffusion process from the body surface into the surrounding water.

Excretion in Human Beings

• The body parts that the excretory system (of human beings) includes are −

  • A pair of kidneys

  • A pair of ureters

  • A urinary bladder

  • A urethra

• Kidneys are located in the abdomen (see the image given below), one on either side of the backbone.

• Urine that produced in the kidneys passes through the ureters into the urinary bladder where it gets stored until released through the urethra.

• On the other hand, plants have completely different process for excretion than those of animals.

• Oxygen (released in the day-time) itself can be considered as a waste product generated during photosynthesis.

• Many plant waste products are stored in leaves that fall off.

• Some other waste products, in plants, are stored as resins and gums, especially in old xylem.