An Overview of Living Organisms and their Characteristics.

Peter M. Williams, Elizabeth Friedl, Christianlly Cena
  • Author
    Peter M. Williams

    Peter holds a Bachelor's degree in Microbiology and Biotechnology, and a Master's degree in Applied Microbiology. In addition, Peter has more than two years of experience in tutoring and writing academic materials for senior and junior schools, mainly in Sciences, Languages, and Humanities.

  • Instructor
    Elizabeth Friedl

    Elizabeth, a Licensed Massage Therapist, has a Master's in Zoology from North Carolina State, one in GIS from Florida State University, and a Bachelor's in Biology from Eastern Michigan University. She has taught college level Physical Science and Biology.

  • Expert Contributor
    Christianlly Cena

    Christianlly has taught college Physics, Natural science, Earth science, and facilitated laboratory courses. He has a master's degree in Physics and is currently pursuing his doctorate degree.

Learn the characteristics of living organisms in this lesson. Understand the definition of a living organism and the characteristics that are present in all known living things. Updated: 11/28/2021

Table of Contents


Living Organism Definition

The world is composed of both living and non-living things. For instance, rocks, metals, plastics, wind, sun, water, and rocks are considered non-living or inanimate objects since they do not have life. On the other hand, a cow, snail, plant, human beings, bacteria, and birds are considered living things, thus living organisms. A living thing is anything that has all the characteristics of life, such as reproduction, growth, and nutrition. An organism is known to be a living thing.

A living organism can therefore be defined as anything that has life, consisting of cells as its basic unit of organization. Some examples of living organisms include:

  • Humans
  • Fungi
  • Algae
  • Trees
  • Animals
  • Bacteria
  • Protozoa
  • Insects

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A butterfly is an example of a living thing.


What are the Characteristics of Living Organisms?

All living organisms have common characteristics that make them differ from non-living things. Some of these features present in all living organisms include cellular organization, reproduction, growth and development, regulation, evolutionary adaptation, and nutrition. Other features include locomotion, excretion, and respiration.

The thick fur of a polar bear is an example of evolutionary adaptation.

Polar Bear

Cellular Organization

All living organisms have cellular organization. Living things have a level of organization that ranges from the simplest to complex, i.e., atoms and molecules, organelles, cells, tissues, organs, organ systems, and finally an entire organism.

Cells are considered to be the basic unit of organization in living things. Inside the cells are various components known as the organelles, and each performs a different role. Some of these organelles include the nucleus, mitochondria, ribosomes, and Golgi bodies. How these organelles are arranged inside the cell is referred to as cellular organization.

Living organisms can either be unicellular or multicellular. The unicellular organism is composed of one cell, while multicellular have numerous cells. Unicellular organisms such as bacteria form the simplest form of life, while multicellular organisms such as a cow display complex forms of life.

The cells of living organisms are classified as either eukaryotic or prokaryotic. Eukaryotic cells have their organelles surrounded by a membrane, e.g., in plants and animals. On the other hand, prokaryotic cells' organelles are not surrounded by a membrane, including the nucleus. Bacteria have these types of cells.


All living things must reproduce to ensure the continuation of their generation. This is a common trait in all living organisms. Reproduction usually results in a new individual, and it can either be sexual or asexual. Sexual reproduction involves the fusion of male and female gametes. This is common in humans and animals.

On the other hand, asexual reproduction may involve spore production, fragmentation, binary fission, and budding. This form of reproduction is common in fungi, bacteria, and protozoa. Reproduction also ensures population growth among living organisms.

In asexual reproduction, the offspring are produced by one parent, and their genetic makeup is identical to that of the parent. Sexual reproduction involves the fusion of two gametes from different parents; thus, the genetic make-up of the offspring is quite diverse.

Growth and Development

All living tends to increase in size irreversibly. This is referred to as growth. In addition, they can also increase in complexity through development. Development can also be defined as changes or transformation. Growth and development bring differentiation in living things. Some living things, such as plants, continue to grow throughout their lifetime, while growth in some living organisms such as humans has a limitation, i.e., growth ceases when one becomes an adult. This trait is absent in non-living things.


Energy is the ability to do work. All living organisms require energy for them to remain alive. The energy is obtained from the breakdown of food. The energy produced is utilized by living organisms to perform various activities. A living organism can either be heterotrophic or autotrophic. Autotrophic organisms such as plants can make their food, while heterotrophic organisms, such as animals, feed on already formed complex organic molecules. This food is then broken down through various pathways to release energy. This feature is missing in non-living things.

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  • Activities
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Characteristics of Living Organisms Word Scramble Activity

In this activity, you will check your knowledge regarding the seven common characteristics present in all living organisms as presented in the lesson.


For this activity, study the scrambled letters and try to unscramble or rearrange the letters to form a word or phrase that fits the given clues. To do this, you must right-click and print this page. With a pencil and an eraser, neatly write your answers in the blank space provided.

Scrambled Words



  1. In sexual reproduction, the reproductive cell of a male and a female, known as _____, are combined to form an offspring.
  2. _____ are single-celled microbes whose cell structure contains no nucleus.
  3. _____ are organisms that can synthesize their food from inorganic substances, using heat or light as a source of energy.
  4. Gradual directional change, especially one leading to a more advanced or complex form, is referred to as _____.
  5. _____ processes, such as blinking, are examples of regulations in our body to maintain internal balance.
  6. An __________ is something external that elicits or triggers a physiological activity or response on an organism.
  7. Cells are the basic structural, functional, and biological unit of all known _____.
  8. Living things are all created through the process of _____.
  9. Humans are considered as __________ because of their complex and incredible cellular organization.
  10. The ability of a system or living organism to adjust its internal environment to maintain a state of dynamic constancy is known as _____.

Answer Key


What are the 7 characteristics of a living organism?

The seven characteristics of a living organism include reproduction, response to environmental change, energy, regulation or homeostasis, growth and development, cellular organization, and evolutionary adaptation.

What are living things?

Living things are anything that have the characteristics of life, such as reproduction, nutrition, and cellular organization. Examples of living things include humans, animals, insects, bacteria, trees, and fungi.

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