Difference Between Holozoic and Saprophytic Nutrition

Main Difference – Holozoic vs Saprophytic Nutrition

Nutrients are the substances that build up body constituents of organisms. The intake of nutrients and their utilization is referred to the nutrition. Holozoic and saprophytic nutrition are two types of nutrition modes in organisms. The main difference between holozoic and saprophytic nutrition is that holozoic nutrition refers to the regular animal nutrition mode that includes internalization and digestion of food particles, absorbing and assimilating the nutrients whereas saprophytic nutrition refers to the nutrition mode of fungi and bacteria that includes external digestion of decaying organic matter, absorbing nutrients through the body wall.

Key Areas Covered

1. What is Holozoic Nutrition
     – Definition, Mechanism, Examples
2. What is Saprophytic Nutrition
     – Definition, Mechanism, Examples
3. What are the Similarities Between Holozoic and Saprophytic Nutrition
     – Outline of Common Features
4. What is the Difference Between Holozoic and Saprophytic Nutrition
     – Comparison of Key Differences

Key Terms: Absorption, Assimilation, Chemical Digestion, Digestion, Excretion. Fungi, Holozoic Nutrition, Ingestion, Mechanical Digestion, Phagocytosis, Saprophytic Nutrition

What is Holozoic Nutrition

Holozoic nutrition refers to a method of nutrition that is involved in the ingestion and digestion of solid or liquid organic material and the absorption and assimilation of nutrients by the animal body. Hence, holozoic nutrition is involved in the uptake of complex substances, converting them into simple substances. The holozoic nutrition is mainly seen in higher animals with well-developed digestive systems. These animals can be herbivores (e.g. cattle, sheep) carnivores (e.g. wolves, lions) or omnivores (e.g. humans, cats). Holozoic nutrition occurs in five steps: ingestion, digestion, absorption, assimilation, and excretion.

Ingestion

Ingestion is the act of consuming liquid or solid food into the body. It may also include the uptake of poisons, pathogens as well as indigestible nutrients. Mouth is the specialized organ for the ingestion in higher animals.

Digestion

The complex food particles are broken down into small substances during digestion. The two types of digestion are mechanical digestion, in which the large food particles are broken down into small particles, and chemical digestion, in which the complex substances such as carbohydrates, proteins, lipids, and nucleic acids are broken down into monosaccharides or disaccharides, amino acids, glycerol and fatty acids, and nucleotides respectively. Mechanical digestion is achieved by the muscular movement of the stomach and small intestine. Chemical digestion is achieved by the action of digestive enzymes.

Absorption

The uptake of nutrients into the bloodstream through the wall of the digestive system is known as absorption. It mainly occurs in the small intestine. The small intestine exhibits adaptations for the absorption of nutrients such as the increased length and the presence of villi.  

Assimilation

The absorbed nutrients are transported to the metabolizing tissues of the body through the blood. They are assimilated into the cytoplasm of the cells from the bloodstream. These nutrients are used in the various functions of the body.

Excretion

The indigestible materials are stored in the rectum and removed through the anus.

Figure 1: Human Digestive System

Holophytic nutrition is the nutrition mode in lower animals such as Hydra that consume liquids as their food. These animals lack a complete digestive system. The mode of nutrition in amoeba-like protozoans is known as phagocytosis.

What is Saprophytic Nutrition

Saprophytic nutrition refers to the method of nutrition in which organisms obtain their nutrients from the decaying organic matter. The source of nutrients can be dead plants, dead animals or other decomposing organic matter. Bread mold, fungi, some protozoans, and many bacteria exhibit saprophytic nutrition. The fungi that grow on decaying organic matter is shown in figure 2.

Figure 2: Fungi Mushrooms on Decaying Organic Matter

Saprophytic nutrition occurs through four major steps: secretion of digestive enzymes, digestion, absorption, and assimilation.

• Secretion of Digestive Enzymes – The organisms that exhibit saprophytic nutrition do not uptake food particles into the body. Thus, the decaying organic matter remains externally to the organism. However, they secrete digestive enzymes through their cell wall onto the decaying organic matter.
• Digestion – The external digestion of decaying organic matter can be observed in saprophytic nutrition by the action of the secreted digestive enzymes. Here, only chemical digestion of organic matter occurs, breaking down the complex organic substances into small nutrients.
• Absorption – The nutrients are directly absorbed into the cytoplasm of the organism through their cell wall.
• Assimilation – The nutrients are then used in the various cellular processes.

Similarities Between Holozoic and Saprophytic Nutrition

• Holozoic and saprophytic nutrition are two types of nutrition modes of organisms.
• Both holozoic and saprophytic nutrition occur belong to the heterotrophic mode of nutrition.
• The digestion of food and absorption of nutrients are common steps in both holozoic and saprophytic nutrition.
• Extracellular digestion occurs in both holozoic and saprophytic nutrition.
• Enzymes are involved in the chemical digestion of food in both holozoic and saprophytic nutrition.

Difference Between Holozoic and Saprophytic Nutrition

Definition

Holozoic Nutrition: Holozoic nutrition refers to a method of nutrition involved in the ingestion and digestion of solid or liquid organic material and the absorption and assimilation of nutrients by the animal body.

Saprophytic Nutrition: Saprophytic nutrition refers to the method of nutrition in which organisms obtain their nutrients from decaying organic matter.

Occurrence

Holozoic Nutrition: Holozoic nutrition occurs in higher forms of animals.

Saprophytic Nutrition: Saprophytic nutrition occurs in fungi and bacteria.

Type of Food Particles

Holozoic Nutrition: Complex organic food material is used in holozoic nutrition.

Saprophytic Nutrition: Dead or decaying organic matter is used in saprophytic nutrition.

Food Particles

Holozoic Nutrition: Food particles are internalized in holozoic nutrition.

Saprophytic Nutrition: Food particles are left external to the organism’s body in saprophytic nutrition.

Digestive System

Holozoic Nutrition: The organisms with holozoic nutrition have a well-developed, complete digestive system.

Saprophytic Nutrition: The organisms with saprophytic nutrition lack a digestive system.

Type of Digestion

Holozoic Nutrition: Food particles are mechanically and chemically digested into small substances in holozoic digestion.

Saprophytic Nutrition: The decaying organic matter is chemically digested into small substances in saprophytic nutrition.

Absorption

Holozoic Nutrition: The digested nutrients are absorbed by the digestive system in holozoic nutrition.

Saprophytic Nutrition: The digested nutrients are absorbed through the cell wall in saprophytic nutrition.

Wastes

Holozoic Nutrition: The wastes are excreted in holozoic nutrition.

Saprophytic Nutrition: The wastes remain outside the organism in saprophytic nutrition.

Role

Holozoic Nutrition: Holozoic nutrition is a type of heterotrophic nutrition.

Saprophytic Nutrition: Saprophytic nutrition is important in recycling nutrients in ecosystems.

Conclusion

Holozoic and saprophytic nutrition are two types of nutrition modes in organisms by which they obtain nutrients required by the functions of the body. Holozoic nutrition is seen in higher animals with a well-developed digestive system. These animals ingest and digest complex food particles, absorb and assimilate nutrients, and finally excrete the waste. Saprophytic nutrition is exhibited by fungi and bacteria. In saprophytic nutrition, the digestive enzymes are secreted onto the decaying organic matter, and the nutrients are absorbed through the body wall. This is the difference between holozoic and saprophytic nutrition.

Reference:

1. Armstrong, John. “What is Holozoic Nutrition? Stages and Features.” Life Persona, 3 July 2017, Available here.
2. Saprophytic Nutrition, Fun Science, Available here.

Image Courtesy:

1. “Digestive-organs,jpg (1)” By Vaagisha – Own work (CC BY-SA 4.0) via Commons Wikimedia
2. “Saprophytes” by Pierre Lardinois (CC BY 2.0) via Flickr