Biological Nutrition and Vital Functions in Organisms

Animal Nutrition

Performed by the digestive system, this process comprises four phases:

• Ingestion: Taking food from the outside.
• Digestion: Processing food into nutrients.
• Absorption: The passage of nutrients into the blood.
• Egestion: The elimination of undigested waste.

Breathing

Performed by the respiratory system, there are several types of breathing:

• Skin: Gas exchange occurs across the body surface.
• Gill: Carried out through gills, thin extensions of the body surface surrounded by blood vessels.
• Tracheal: Accomplished by tracheae, thin extensions that reach almost all animal cells.
• Pulmonary: Takes place in the lungs, internal cavities with thin, moist walls and blood vessels.

Circulation

The circulatory system performs transport. Types of systems include:

• Open: The transport fluid leaves the blood vessels and spreads through spaces between organs.
• Closed: Blood always circulates inside blood vessels.
• Simple: Blood passes through the heart only once per full circuit.
• Double: Blood passes through the heart twice, involving major and minor circulation.

Excretion

A process that collects waste products from cellular activity to be expelled. This is performed by: Malpighian tubules (insects), green glands (crustaceans), and the excretory apparatus (vertebrates).

Plant Nutrition

Includes the following processes:

• Absorption: Water and minerals (crude sap) pass from the soil into the root hairs.
• Transportation of Crude Sap: Driving sap from roots to green parts via xylem vessels.
• Gas Exchange: Occurs via the stomata.
• Photosynthesis: Occurs in leaves and green stems.
• Transportation of Elaborated Sap: Transporting substances produced in photosynthesis to all plant cells via the phloem.
• Mitochondrial Respiration: Use of organic substances for energy.
• Excretion: Elimination of waste products generated in metabolism.