Life Processes in 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.

1. 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).

2. 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.

3. 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).

4. 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.

5. 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).

6. 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.

7. 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

1. b. Phloem

2. b. Sensitivity

3. c. Nutrition

4. b. Kidney

5. 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.