Essential Biological Processes: Excretion and Nutrition

Excretion in Animals and Insects

Excretion is the process of collecting waste products and expelling them outside the body. Some animals don't possess an excretory system and expel waste products directly through the pores.

Insects use Malpighian tubules to expel waste products. The tubules are thin and collect waste. The excretory system in vertebrates consists of various organs: Kidneys (which produce urine), ureters (through which it then flows into the bladder), and the urethra (through which urine is expelled).

How Plants Carry Out Nutrition

Absorption

Absorption is the movement of water and mineral salts from the ground to the inside of the roots. Water and mineral salts are absorbed by the roots. These inorganic nutrients are called raw sap, which consists of water and mineral salts.

Transport of Raw Sap

Transport begins inside the root when the raw sap enters long tubes called xylem vessels. The sap travels up the stem to the leaves and other green parts of the plant.

Photosynthesis

Photosynthesis takes place in the chloroplasts where chlorophyll is found. Chlorophyll absorbs sunlight to produce energy. This energy transforms the elaborated sap.

Transport of Elaborated Sap

Elaborated sap is transported from the green plant cells to all parts of the plant. This sap travels through phloem vessels.

Interaction in Living Beings

All living beings interact with their environment and with other living beings to survive. Interaction enables living beings to receive and respond to a stimulus. Interaction involves different elements:

Stimuli

These are detectable changes in the internal or external environment. They provoke responses. Stimuli can be:

• Physical: Light, sound, temperature, etc.
• Chemical: The presence or absence of chemical substances.
• Biotic: Changes caused by the presence of other living beings.

Receptors

These are structures which receive stimuli from the external or internal environment.

Coordination Systems

These consist of organs which process information received by the receptors and produce a response.

Responsive Organs

These are structures which produce responses.