What Are the Seven Life Processes of Living Organisms?
Life processes are fundamental functions carried out by all living organisms to sustain life and ensure the continuity of their species. They include everything from obtaining and utilising nutrients to reproducing and expelling waste. In life processes biology, we examine how plants and animals manage these vital functions so effectively. A strong grasp of these concepts helps us appreciate the diversity of life on Earth, understand our own bodies better, and paves the way for groundbreaking research and innovations.
Below, we will explore the 7 life processes of living things—often remembered by the acronym MRS GREN—alongside additional essential functions such as transportation and metabolism. We will also highlight the life processes of animals and plants to understand how different organisms maintain survival.
The 7 Life Processes of Living Things (MRS GREN)
Biologists commonly summarise the core functions of living organisms as MRS GREN. Each letter stands for a fundamental life process crucial for survival.
Movement
All living things show some form of movement. Animals can move freely, while plants exhibit movement at cellular levels (e.g., opening and closing of stomata, growth movements towards light).
Respiration
This life process involves releasing energy from food. Organisms may respire aerobically (with oxygen) or anaerobically (without oxygen). In life processes of animals, respiration occurs primarily in specialised organs (lungs, gills), whereas plants respire through stomata and lenticels.
Sensitivity (or Response to Stimuli)
Living organisms detect and respond to changes in their environment. Animals possess highly developed sense organs. Plants respond to light (phototropism), touch (thigmotropism), and gravity (gravitropism).
Growth
Growth is an irreversible increase in size and mass. Animals grow until a certain age, while most plants can continue to grow throughout their lifespan.
Reproduction
This ensures the continuation of the species. Animals often use sexual reproduction, though certain lower organisms and simple animals can reproduce asexually. Plants can reproduce both sexually (via pollination and seeds) and asexually (via budding, vegetative propagation).
Excretion
It is the removal of metabolic waste produced during life processes. In life processes of animals, the excretory system filters out nitrogenous and other wastes. Plants eliminate excess water through transpiration, oxygen via stomata, and store other wastes like resins and gums in specific tissues.
Nutrition
This life process involves obtaining food and using it for energy and growth. Green plants (autotrophs) use sunlight, carbon dioxide, and water to produce their own food (photosynthesis). Animals and many microbes (heterotrophs) depend on plants or other organisms for nutrition.
Additional Essential Life Processes
While MRS GREN covers seven fundamental processes, two more key elements—transportation and metabolism—are vital components of life processes biology.
Transportation
In Animals: Transportation occurs through the circulatory system, consisting of the heart, blood, and blood vessels. Nutrients, oxygen, and waste products are moved around the body to maintain stable internal conditions.
In Plants: Plants use xylem to transport water and minerals from the roots to the upper parts. The phloem carries synthesised food from the leaves to various parts of the plant. This vascular system is essential for distributing nutrients and water to all plant cells.
Metabolism
Catabolism: The process where large molecules break down into simpler ones, releasing energy.
Anabolism: The synthesis of complex molecules from simpler ones, which stores energy for future use.
Metabolism is central to a living organism’s energy balance and helps manage every life process effectively.
Comparing Life Processes of Animals and Plants
Also Read: Transportation in Plants and Animals
Homeostasis
Homeostasis refers to an organism’s ability to regulate its internal environment (e.g., temperature, pH levels, water balance) to maintain stable conditions needed for life processes to function optimally. While animals often use systems like sweating, shivering, or hormonal regulation, plants adjust their internal water balance and stomatal opening to maintain ideal conditions for photosynthesis and growth.
Fun Interactive Quiz on Life Processes
Test your knowledge with our quick five-question quiz on life processes biology.
1. Which vascular tissue transports food in plants?
a. Xylem
b. Phloem
c. Epidermis
2. What term is used to describe living organisms responding to a stimulus?
a. Movement
b. Sensitivity
c. Growth
3. Which of the 7 life processes of living things is responsible for making or obtaining food?
a. Excretion
b. Respiration
c. Nutrition
4. Which organ in humans primarily filters out wastes?
a. Heart
b. Kidney
c. Lungs
5. True or False: Green plants perform photosynthesis but do not respire.
Check Your Answers
b. Phloem
b. Sensitivity
c. Nutrition
b. Kidney
False. Plants also respire to release energy from food.
By appreciating how each life process intertwines—whether it be nutrition, respiration, or excretion—you gain a holistic view of life processes biology. Both plants and animals exhibit the 7 life processes of living things, albeit in different manners, underscoring the remarkable variety and adaptability of life on Earth. Keep exploring these processes, engage in experiments, and build a deeper understanding of what makes life function so seamlessly.
FAQs on Life Processes in Biology: 7 Essential Functions Explained
1. What are the main life processes essential for any living organism?
The main life processes are the vital functions performed by living organisms to maintain and sustain life. The key processes as per the CBSE syllabus include:
- Nutrition: The process of taking in food and converting it into energy.
- Respiration: The process of releasing energy from food, which can be aerobic (with oxygen) or anaerobic (without oxygen).
- Transportation: The movement of substances like food, oxygen, and waste products from one part of the body to another.
- Excretion: The removal of metabolic waste products from the body to prevent toxicity.
- Control and Coordination: Responding to stimuli in the environment.
- Growth: An irreversible increase in an organism's size and mass.
- Reproduction: The biological process of producing new offspring.
2. What is the main difference between autotrophic and heterotrophic nutrition? Give examples.
The main difference lies in how organisms obtain their food. Autotrophic nutrition is the process where organisms produce their own food from simple inorganic substances like carbon dioxide and water, typically using light energy (photosynthesis). For example, green plants and algae are autotrophs. In contrast, heterotrophic nutrition is where organisms cannot synthesise their own food and depend directly or indirectly on other organisms for nourishment. Examples include animals, fungi, and most bacteria.
3. What is the importance of respiration for an organism?
Respiration is critically important because it is the metabolic process that releases energy from digested food. This energy, stored in molecules called ATP (Adenosine Triphosphate), is essential to power all other life processes, including growth, movement, substance transport, and maintaining body temperature. Without the constant energy supply from respiration, cells cannot perform their functions, and the organism cannot survive.
4. How are substances like water, food, and minerals transported in plants?
Plants have a specialised transport system made of two main conducting tissues:
- Xylem: This tissue forms a continuous network of vessels that transports water and dissolved minerals absorbed by the roots up to the leaves and other parts of the plant.
- Phloem: This tissue transports the soluble products of photosynthesis, such as sucrose, from the leaves to other parts of the plant for use or storage. This process is known as translocation.
5. Explain the process of excretion in human beings.
In humans, the primary excretory system is the urinary system. Blood containing metabolic wastes, mainly urea, flows into the kidneys. Inside the kidneys are millions of filtering units called nephrons. Here, the blood is filtered; essential substances like glucose, amino acids, and some water are reabsorbed back into the blood. The remaining waste products and excess water form urine, which travels through the ureters to the urinary bladder for storage before being expelled from the body.
6. Why is the process of diffusion insufficient to meet the oxygen requirements of multicellular organisms like humans?
Diffusion is a slow process that is only effective over very short distances. In large multicellular organisms, most cells are not in direct contact with the external environment. The distance between the air and the innermost cells is far too great for oxygen to reach them in time by diffusion alone. Therefore, these organisms need a specialised respiratory system (like lungs) and a circulatory system (blood) to efficiently transport oxygen to every cell in the body.
7. How is the small intestine designed to maximise the absorption of digested food?
The small intestine has several key features to maximise food absorption. Its inner lining is folded into millions of tiny, finger-like projections called villi. These villi, in turn, are covered with even smaller projections called microvilli. This structure vastly increases the internal surface area available for absorption. Additionally, the villi have a rich supply of blood capillaries, which allows for the rapid and efficient transfer of digested nutrients into the bloodstream.
8. If a plant is photosynthesising during the day, does it also respire? Explain why.
Yes, a plant respires continuously, 24 hours a day, including when it is actively photosynthesising. The two processes serve different purposes: photosynthesis uses energy to produce food (glucose), while respiration breaks down that food to release energy for the plant's metabolic activities. During the day, the rate of photosynthesis is typically higher than respiration, so there's a net release of oxygen. At night, only respiration occurs, resulting in a net intake of oxygen.
9. What would be the consequences if platelets were absent in our blood?
If platelets were absent, the body's ability to perform blood clotting (coagulation) would be lost. Platelets are cell fragments that rush to the site of an injury and form a plug to stop bleeding. Without them, even a minor cut could lead to continuous, uncontrolled bleeding, resulting in significant blood loss, a dangerous drop in blood pressure, and a lack of defence against invading pathogens at the wound site.
10. Why is reproduction considered a life process if it is not essential for an individual's survival?
Reproduction is unique because while it is not necessary for the survival of an individual organism, it is absolutely essential for the continuation and survival of a species. An organism can live its entire life without reproducing. However, if a species as a whole stops reproducing, it will not be able to produce a new generation, leading to its eventual extinction. Thus, it is a vital process for the propagation of life itself.
