NUTRITION AND DIGESTIVE PROCESS

Animals are classified as heterotrophs. They cannot make their own food. They need to feed on other organisms.

Heterotrophic nutrition, organic substances are obtained from the plants and animals. Converted into matter and energy.

Several processes are involved in heterotrophic nutrition:

-Digestion. Food is converted into nutrients.

-Respiration. Oxygen is taken from the environment and carbon dioxide is expelled.

-Transport. Nutrients and oxygen are distributed all through the body to the cells.

-Metabolism. Cells convert nutrients into energy. Complex substances are broken down into simpler substances. Reactions convert simple substances into more complex.

-Egestion. Carbon dioxide and other waste products are eliminated from the body.

THE DIGESTIVE PROCESS IN ANIMALS.

Digestive process has  four stages:

Stage 1:Ingestion. Food is taken into the body.

Stage 2:Digestion. Nutrients are extracted from food.

Two types of digestion:

-Intracellular digestion takes placeinside the individual cells.

-Extracellular digestion takes place inside the digestive tube.

-Stage 3: Absorption. Nutrients pass from the digestive system. Blood carries the nutrients to cells.

-Stage 4: Egestion. Matter and waste products eliminated from the body.

THE DIGESTIVE PROCESS IN INVERTEBRATES.

Digestion in invertebrates can be intracellular, extracellular or a mixture.

Intracellular:

-Typical of porifera.

-Digestion accurs inside cells.

-Water is pulled through the pores into the central cavity.

-Specialized cells called choanocytes capture food particles and digest them.

Mixed:

-Typical of cnidaria.

-Prey is captured with the tentacles and ingested through the mouth.

-Two stages of digestion:

Extracellular: in the gastrovascular cavity.

Intracellular: inside cells.

Extracellular:

-Typical of invertebrates.

-Digestion occurs outside cells in the digestive tube.

-The digestive tube is divided into several parts, each with a different function.

THE DIGESTIVE PROCESS IN VERTEBRATES.

Vertebrates have extracellular digestion. Takes place in the digestive system, consists of:

-A digestive tube divided into a mouth, the pharynx, the oesophagus, the stomach and the intestines.

-Accessory glands. The salivary glands, the liver and the pancreas aid digestion.