Animal and Plant Nutrition: Processes and Adaptations
Nutrition
Nutrition describes the processes by which living things take in external substances and turn them into matter and energy.
Autotrophs
Autotrophs produce their own organic matter from inorganic substances taken from the environment. They can be:
- Photosynthetic: Obtain energy from sunlight.
- Chemosynthetic: Obtain energy from chemical reactions.
Heterotrophs
Heterotrophs feed on other organisms or their remains. They can be carnivores, herbivores, omnivores, filter feeders, scavengers, etc.
Processes in Animal Nutrition
Digestion, gas exchange, transport, metabolism, and excretion.
Processes in Plant Nutrition
Absorption, transport, evapotranspiration, gas exchange, photosynthesis, transport of organic substances, metabolism, cellular respiration, and elimination.
Digestive Process of Animals
These are the phenomena that occur in the digestive system to capture food, transform it into useful substances, and expel waste material.
Phases in the Digestive Process
- Ingestion: Taking food from the outside.
- Digestion: Food processing to obtain nutrients. It can be:
- Intracellular: Within the cell.
- Extracellular: Occurs outside the cells in the gastrointestinal tract.
- Absorption: Passage of nutrients into the blood.
- Egestion: The elimination of undigested residues to the exterior.
Types of Digestive Systems
- Gastric Cavity: A sac lined with cells that communicates with the outside through an opening that functions as both mouth and anus.
- Digestive Tract: A tube that begins in the mouth and ends in the anus. Along the tube are regions that have different specific functions.
Digestive Process of Invertebrates
Sponges
Sponges capture food through pores that have choanocytes, cells responsible for digestion.
Coelenterates
Coelenterates catch food with their tentacles, inject and paralyze it, and then introduce it into an opening that functions as both mouth and anus.
Mollusks
Mollusks have extracellular digestion. They possess a digestive tract with a mouth and anus, and glands that secrete enzymes.
Arthropods
Arthropods have external digestion that begins in the mouth and continues through the esophagus, crop, gizzard, intestine, and finally the anus.
Digestive Process in Vertebrates
Vertebrates have extracellular digestion in the digestive tract. It consists of the mouth, pharynx, larynx, stomach, intestine, and anus. Attached glands include salivary, hepatic, and pancreatic glands.
Respiration in Animals
Respiration occurs inside the cells. Nutrients are degraded in the mitochondria, requiring oxygen. Energy is obtained, and waste substances are removed. This exchange occurs in the respiratory tract.
Gas Exchange Surfaces
These surfaces must be thin, moist, and covered with a large number of blood vessels.
- Cutaneous Respiration: Gas exchange takes place through the skin, which is supplied with numerous blood vessels.
- Branchial Respiration: Takes place through gills, thin extensions with many blood vessels. They can be external (outside the animal, without protection) or internal (protected by a cavity that communicates with the outside).
- Tracheal Respiration: Occurs through tracheae, branching tubes that reach all organs of the animal and open to the outside through spiracles. The tracheae decrease in diameter to reach the cells where the exchange takes place.
- Pulmonary Respiration: Occurs in the lungs, internal cavities that are very thin, moist, and have many blood vessels. Involves inspiration and expiration. Examples include:
- Amphibians: Smooth-walled lungs.
- Reptiles: Partitioned lungs.
- Birds: Air sacs.
- Mammals: Tiny sacs called alveoli.
Circulatory System of Animals
The circulatory system carries nutrients and oxygen to cells and removes carbon dioxide and metabolic waste. It includes:
- Transport Fluid: Liquid flowing through the interior, formed by water, proteins, and various cells. It is called blood.
- Vessels:
- Arteries: Carry blood away from the heart.
- Veins: Return blood to the heart.
- Capillaries: Vessels that connect veins and arteries where the exchange takes place.
- Heart: Organ that drives the transport fluid through the vessels via contraction and dilation.
Types of Circulatory Systems
- Open Circulatory System: Vessels do not form a closed circuit. Exchange is done directly on the cells, and then blood returns to the heart through ostioles.
- Closed Circulatory System: Blood always circulates inside the vessels. It can be simple or double.
Excretion in Animals
Excretion is the process that allows the collection of waste products and their removal to the outside.
Types
- Insects: Use Malpighian tubules where waste products are dumped.
- Crustaceans: Have green glands that collect substances and remove them to the outside.
- Vertebrates: Possess kidneys that form urine, which travels through the ureters to the bladder and exits through the urethra.
- Reptiles and Birds: Those that drink salt water have special salt-secreting glands that eliminate excess salt.
Absorption of Sap in Plants
Absorption occurs through absorbent root hairs, taking water and minerals from the ground. This raw sap then rises to other parts of the plant through conducting vessels called xylem.
Gas Exchange in Plants
Gas exchange occurs through the stomata of the leaves, where carbon dioxide enters and oxygen is released. During photosynthesis, the oxygen produced is released.
Photosynthesis and Transport of Elaborated Sap
Transport of elaborated sap occurs through conducting vessels called phloem, which are formed by living cells.
Metabolism and Cellular Respiration in Plants
Organic nutrients are used through anabolic reactions and degraded in catabolic reactions, obtaining energy and building the plant’s own matter.
Excretion in Plants
Plants eliminate waste products generated during metabolism. They lack an excretory system.