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Life Process in Plants and Animals

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  • Last Updated : 31 Aug, 2022
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The process that all living organisms perform to maintain their life is called life processes. The basic life processes common to all living organisms are nutrition, respiration, transportation, and excretion. Living creatures must keep repairing and sustaining their structures. Different maintenance functions are required to regulate the proper functioning of a body. Thus, the process which maintains the body’s functions and is necessary for survival are called life processes. Let’s have an overview of all these life-maintaining processes which describe the qualities of organisms, whether alive or not. 


It is a process in which an organism obtains nutrients from food and utilizes them to obtain energy and for building and repair its tissues. Nutrients are defined as the substances required for proper growth and maintenance of the living body, i.e., the materials, which provide energy to organisms. 

All living organisms do not obtain food by the same method, e.g., plants and some bacteria have the green pigment chlorophyll to help synthesize food by the process called photosynthesis. Likewise, animals, fungi, and other bacteria depend on plants and other organisms for food. Based on this, there are two main types of nutrition, i.e, autotrophic and heterotrophic.

Autotrophic Nutrition

The mode of nutrition in which organisms synthesize their food from simple inorganic substances like carbon dioxide and water in the presence of sunlight is called autotrophic, e.g, green plants and some bacteria. This mode of nutrition is called the autotrophic mode of nutrition.

Plant Nutrition: Photosynthesis

It is a complex process by which green parts of the plant synthesize organic food. This food is prepared by green plants from carbon dioxide and water in the presence of sunlight and chlorophyll. It involves the given reaction:

6CO2 + 6H2O → C6H12O6+ 6O2  

The following events occur during the process of photosynthesis:

  • Absorption of light energy by chlorophyll.
  • Conversion of light energy to chemical energy and splitting of water molecules into hydrogen and oxygen.
  • Reduction of carbon dioxide to carbohydrates.

Site of photosynthesis: Chloroplasts

  • The organelles in the cells of the green plant which contain chlorophyll are called chloroplasts.
  • Chloroplasts are the site of photosynthesis, as they contain chlorophyll pigment.
  • Stomata are the tiny pores present on the surface of the leaves. Massive amounts of gaseous exchange take place in the leaves through these pores for the purpose of photosynthesis.

Heterotrophic Nutrition

In the heterotrophic mode of nutrition, organisms cannot prepare their food on their own. These organisms are termed heterotrophs. e.g., human beings, animals, non-green plants, etc. Heterotrophs obtain energy from organic molecules already produced by autotrophs.

Three main types of Heterotrophic modes of nutrition are: 

  1. Holozoic nutrition is a type of heterotrophic nutrition that is characterized by the internalization (ingestion) and internal processing of liquids or solid food particles.e.g. Amoeba, cow, dog, etc.
  2. Saprotrophic nutrition is the mode of nutrition in which organisms feed on dead and decaying matter. Example fungi.
  3. Parasitic nutrition is that nutrition in which an organism derives its food from the body of another living organism called its host without killing it. Example: Plasmodium and roundworms obtain food by parasitic nutrition.

Nutrition in Amoeba

Nutrition in an Amoeba occurs through a process called phagocytosis, where the entire organism pretty much engulfs the food it plans on eating up. The mode of nutrition in amoeba is known as holozoic nutrition. It involves the ingestion, digestion, and egestion of food material.

Nutrition in Human Beings

In human beings, the process of intake of essential nutrients in the form of food takes place through an entire system known as the digestive system. The human digestive system constitutes a long tubular structure called the alimentary canal and various digestive glands.

The major portions of the Alimentary canal are:

  • Mouth-It is the first part of the digestive system from where the food enters the alimentary canal. It is mainly composed of two major parts: Tongue and Teeth.
  • Pharynx-It is the small funnel-shaped chamber located below the oral cavity.
  • Oesophagus-It is a thin and long muscular tube that leads into the stomach.
  • Stomach-the stomach is a large organ that expands when food enters it.
  • Small intestine-It is the longest part of the alimentary canal. It is the site of the complete digestion of food into different components.
  • Large intestine-Although shorter, it is a large intestine because it is wider in diameter than the small intestine.
  • Rectum-It is the last and broad chamber-like structure.
  • Anus-It is the end point of the alimentary canal.

Various glands are associated with the alimentary canals such as salivary glands, gastric glands, liver, intestinal glands, and pancreas.

Mechanism of Digestion of Food

The food we eat contains various components like carbohydrates, proteins, fats, vitamins, minerals, etc. Various steps involved in the digestion of these nutrients are given below:

  1. Ingestion-It is the process of intake of food by mouth.
  2. Digestion-The process of breaking down large organic molecules into smaller molecules is called digestion.
  3. Absorption-It is the process by which digested food passes from the alimentary canal into the blood.
  4. Assimilation-It is the distribution of digested food particles to various cells of the body.
  5. Egestion-It is the removal of undigested food materials.


It is defined as the process of the biochemical oxidation of nutrients at the cellular level. It occurs in the presence of specific enzymes at optimum temperature in the cells to release energy for various metabolic activities.

The process in a complete way can be written in the form of an equation:

Food + oxygen → Carbon dioxide + Water + Energy

Types of Respiration

There are two types of respiration: Aerobic and Anaerobic respiration.

  • Aerobic respiration: It is the process in which a large amount of energy is released in the presence of oxygen (air) from the breakdown of food substances. The equation of Aerobic respiration is given below:

C6H12O6 + 6O2 yields 6CO2 + 6H2O + energy (as ATP)

  • Anaerobic respiration: It is the process in which a small amount of energy is released in the absence of oxygen (air) from the breakdown of food substances. It takes place in yeast, bacteria, and in human muscles. 

On the basis of products form, it is of two types:

  • Alcoholic fermentation: An incomplete breakdown of sugar into ethanol and carbon dioxide to release energy is called as alcoholic fermentation.
  • Lactic Acid fermentation: It is the process of the incomplete breakdown of sugar into lactic acid and energy in some bacteria, is called Lactic acid fermentation.

Stages of Respiration

Generally, respiration consists of the following two basic stages:

  • External Respiration: It is of two types, as follows 
    • Breathing-It is the process by which air rich in oxygen is taken inside the body of an organism and air rich in carbon dioxide is expelled from the body.
    • Gaseous Exchange-It involves the diffusion of O2 from lungs to blood and CO2 from lungs to blood.
  • Internal Respiration: It refers to the gaseous exchange between the arterial blood and the body cells.

Exchange of gases in plants

Exchange of gases in animals

In plants exchange of gases occurs through stomata and large intercellular spaces present throughout the plant body. Animals have evolved different organs for the uptake and out of gases. These organs work together and constitute the respiratory system of an organism.
In leaves, gaseous exchange takes place by diffusion of oxygen through stomata into the cells of the leaf. The aquatic organisms utilize oxygen dissolve in water for respiration where the amount of dissolved oxygen is fairly low than the amount of air oxygen.
The exchange of gases in the roots of a plant takes place by the process of diffusion from the air present in between soil particles. Terrestrial organisms use atmospheric oxygen for respiration. This oxygen is absorbed by different organs in different animals.
In woody plants, gaseous exchange occurs through the small pores found on stems called lenticels. Amoeba and planaria have cell membranes as their respiratory surface. Birds, lizards, and terrestrial organisms have lungs for respiration.
All the parts of a plant perform respiration individually. An animal performs respiration as a single unit.
Respiration occurs at a much slower rate. Respiration occurs at a faster rate.

Human Respiratory System

Like other animals, the respiratory system in human beings serves to provide fresh oxygen to all body cells and removes harmful carbon dioxide from the body. 

The parts of the human respiratory system are as follows:

  • Nostrils: Air is taken into the body through the nostrils.
  • Nasal passage: It is mainly the conducting zone for air.
  • Pharynx: Nasal chamber opens into the pharynx. It passes it to the larynx.
  • Larynx: is located in the neck region and in front of the trachea.
  • Trachea: The air passes from the pharynx and gets into the trachea.
  • Bronchi: The trachea divides into two smaller tubes called Bronchi.
  • Bronchioles: Bronchi are subdivided into two smaller tubes called Bronchioles.
  • Alveoli: These are balloon-like structures located inside the lungs.
  • Ribs: There are 12 pairs of bones that form a cage in the thoracic region.
  • Lungs: These are the primary organs for respiration.


During metabolism, a cell produces some useful and some waste products. The substances that are useful, need to be transported to the other cells, while harmful substances are to be eliminated. This is done by the process of transportation.

Transportation in Human beings

Transportation in plants

The transport system of human beings, also called the circulatory system, comprises a blood vascular system and lymphatic system. Plants lack a regular transport system. The conduction of some materials to short distances occurs through diffusion.
The blood vascular system has three components- blood, blood vessels, and the heart. For longer distances, a need for a proper transportation system arises. Two pathways have developed in plants which comprise Xylem and phloem tissues.
The lymphatic system includes lymph, lymph vessels, and lymph nodes. Two pathways have developed in plants which comprise Xylem and phloem tissues. 
Blood supplies nutrients and oxygen to all living cells. Xylem transports water and minerals obtained from soil and    Phloem transports food.
The heart is a muscular organ that plays the role of a pump. The loss of water in the form of vapors from the aerial parts of the plant is called transpiration.


Excretion is the process by which organisms remove harmful metabolic wastes from the body. The mode of excretion is completely different in unicellular and multicellular organisms.

Excretion in Human beings

Excretion in plants

The main function of human excretory system is to remove nitrogenous wastes such as urea from the body. Plants also excrete various waste products during their life processes.
It includes a pair of kidneys, a pair of ureters, a urinary bladder and a urethra. The waste products are excreted by plants in completely different forms than those of animals.
The main organ of the human excretory system is the kidney. Its main function is to remove excess water and nitrogenous wastes from the blood in the form of urine. Plants release gaseous waste products such as carbon dioxide and water vapor at night and oxygen in the daytime through stomata in leaves and lenticels found in the stem.
Each kidney contains a large number of tiny filtration units called nephrons. Plants get rid of excess water produced as waste during respiration by the process of transpiration.
Kidney failures can be managed by artificial kidneys. It is a device used to remove nitrogenous waste products from the blood through dialysis. Some plants store waste substances in the cellular vacuoles and in tissues with dead cells, e.g., in the heartwood. 

FAQs on Life Processes

Question 1: What do you mean by Respiration?


It is defined as the process of the biochemical oxidation of nutrients at the cellular level. 

Question 2: What is Autotrophic nutrition? Give examples.


The nutrition in which organisms make their own food by the process called photosynthesis is known as autotrophic nutrition. For example, green plants and some bacteria.

Question 3: Which organ plays the main role in excretion in humans?


The main organ of the human excretory system is the kidney.

Question 4: What is the site of photosynthesis?


Chloroplasts are the site of photosynthesis, as they contain chlorophyll pigment.

Question 5: Define transportation in humans.


The transport system of human beings also called the circulatory system, comprises a blood vascular system and lymphatic system.

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