What Is Life? A Guide to the Common Features of all Living Things

Updated on December 8, 2018
Have you ever thought what separates the horses and grass from the sky and mountain? It's easy - Mrs. Gren
Have you ever thought what separates the horses and grass from the sky and mountain? It's easy - Mrs. Gren | Source

What is Life?

Take a moment and reflect on the huge diversity of the natural living world. Life has taken on a huge variety and complexity of form: bacteria and archaea dominate the microscopic world; plants form the basis of most ecosystems; animals interact with and around each other. Everywhere you look (almost) you see traces of life. Indeed, even locations that have been previously thought to be completely inhospitable to life are starting to reveal their secret ecosystems. Weird and wonderful organisms are being discovered in the depths of the oceans and at the centre of deserts (both hot and cold).

But have you ever stopped to think what links all of these different types of living organisms together? What separates a moss or a plant from a rock? All living things share seven key traits that identifies them as 'living.' We shall explore each trait individually until we have covered the seven characteristics of living things

Move

The most obvious difference between a living and a non-living thing is their ability to move under their own power. Different living things move at different speeds - animals move very quickly whilst plants (with some notable exceptions) generally move slowly.

Fun Facts:

  • The fastest moving animal on Earth is the Peregrine Falcon, which can move at 155mph (250kph).
  • The fastest accelerating organism on Earth is the Hat Thrower Fungus which can go from 0-20mph in 2 millionths of a second.

Respire

Respiration is not simply 'breathing.' Respiration is a series of metabolic processes that releases energy stored in food. All living things need to release the energy from their food to fuel their other activities. There are two types of respiration commonly used in the living world:

  • aerobic respiration releases energy using oxygen
  • anaerobic respiration releases energy in the absence of oxygen

Metabolism is a constant process that begins at the conception of the organism; once metabolism ceases, the organism dies.

Touted as the ultimate in senses - the Eagle Eye. But senses are not just limited to sight - there are many weird and wonderful senses in the living world
Touted as the ultimate in senses - the Eagle Eye. But senses are not just limited to sight - there are many weird and wonderful senses in the living world | Source

Sense

Kick a stone down a path and it doesn't know it has been kicked. Living things are capable of sensing, and responding to, environmental stimuli. It is a myth that humans have 5 senses - a sense is the ability to gather information about the world; humans have more than a dozen senses including pain, pressure, proprioception, hunger and thirst.

Fun Facts:

  • Butterflys taste with their feet, catfish taste with their entire body.
  • Some bizarre senses found in the living world include: sensing electricity (sharks and rays); sensing the Earth's magnetic field (migrating birds); sense polarisation of light (birds and insects); and heat vision (pit vipers)

Grow

Boulders do not spontaneously get bigger, houses do not suddenly grow another storey. On the other hand, all living things grow - they increase their size by assimilating biomolecules from their environment.

Fun Facts:

  • The largest organism on Earth is not the Blue Whale. It is a fungus (Armillaria ostoyae) that measures nearly 10 square kilometers in size. This organism occupies 2384 acres of forest in Oregon's Blue Mountains (this could be one of the oldest organisms on Earth too!)
  • The fastest growing organism on Earth is Giant Kelp (Macrocystis pyrifera) which can grow up to 2 feet per day

The start of animal life - the fertilisation of an egg by a sperm cell. All living things reproduce, something non-living things cannot do.
The start of animal life - the fertilisation of an egg by a sperm cell. All living things reproduce, something non-living things cannot do. | Source

Reproduce

It is probable, as you sit there reading this hub, that you have parents. The chances are that your parents themselves have parents. You may even have children of your own. All living things reproduce - they create fertile offspring that can carry on their genes. There are many different reproductive strategies favoured across the natural world from parthenogenesis in lizards, to asexual reproduction in tapeworms and bacteria, to sexual reproduction favoured by most plants and animals.

Fun Facts:

  • A baby blue whale is born after an entire year inside the womb. They are born weighing in at a hefty 3 tons and 25 feet long
  • Aphids are one of the most versatile reproducers in the natural world. They can lay eggs, or go viviparous and give birth to live young (which can already be pregnant!) They can mate with males or undergo parthenogenesis and skip the need for a man completely. It has been suggested that, in perfect conditions with no predators, a single aphid could produce as many as 600 billion offspring in a single year.

Excrete

Living things take in various chemicals for a series of reactions collectively known as 'metabolism.' The problem with this is that metabolism produces waste products that must be removed. Products that need removal include:

  • Urea
  • Carbon Dioxide
  • Oxygen
  • Undigestable food

Fun Facts:

  • The human organ with the highest blood flow are the kidneys - these filter out waste products from our blood for excretion. Up to 2 litres of urine can be made per day
  • The largest human organ of excretion is the skin

One of the quintessential images of 'eating': A Parrot snake (Leptophis ahaetulla) eating (in this case a frog)
One of the quintessential images of 'eating': A Parrot snake (Leptophis ahaetulla) eating (in this case a frog) | Source

Nutrition

Living things release energy from their food through respiration, but first they must either make or consume this food. Autotrophs create their own food using energy from the sun or from hydrothermal vents. Heterotrophs get their food by consuming other living things.

Fun Facts:

  • The Atlas moth spends its entire life searching for a mate - this time is limited to a few weeks as the adult does not eat...unlike its pupae stage which has a voracious appetite
  • The largest mouth in the animal world belongs to the Bowhead Whale at 16 feet long, 8 feet wide and 12 feet high.

Can't remember all that? The Mneumonic 'Mrs. Gren' can be used to remember the common characteristics of living things

Knowledge Check

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Questions & Answers

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      • profile image

        Randy 

        6 years ago

        Thanks this was very helpful.

      • profile image

        Ricky James 

        6 years ago

        Thank You for all the information

      • profile image

        Harvey_jiang 

        6 years ago

        Gwan Woo is on here

      • TFScientist profile imageAUTHOR

        Rhys Baker 

        6 years ago from Peterborough, UK

        @ Healthy Pursuits - High praise indeed! I am glad you enjoyed it:)

        @Seeker7 - I try to write things that I find interesting in the hope that others feel the same. More than half of the facts here I did not know myself before publishing!

        @am9905d - thanks for stopping by my hub. I hope future hubs are also of interest to you

        Thanks to all for your kind words!

      • Healthy Pursuits profile image

        Karla Iverson 

        6 years ago from Oregon

        You never fail to entertain and inform, TFScientist. This is the only hub that I have ever voted up, and marked interesting, useful AND awesome! Great hub!

      • am9905d profile image

        am9905d 

        6 years ago from Greece

        Some really interesting facts.

        Great Hub!

      • Seeker7 profile image

        Helen Murphy Howell 

        6 years ago from Fife, Scotland

        Wonderful and fascinating hub! In particular about the largest organism in the world being a fungus and also maybe the oldest? Awesome!! This was a thoroughly absorbing and enjoyable read.

        Voted up + interesting + awesome!

      • TFScientist profile imageAUTHOR

        Rhys Baker 

        6 years ago from Peterborough, UK

        Thanks to all for stopping by and reading my latest offering. I loved the comments

        @PegCole17: I am glad you found this interesting and useful

        @dmop: you are quite right that there are much heavier organisms out there, which is why I focussed on the largest by volume. I find it ironic that the largest organism on Earth is, in fact, a micro-organism

        @pinkhawk: thanks for the up vote! I am glad you liked it

      • pinkhawk profile image

        pinkhawk 

        6 years ago from Pearl of the Orient

        Voting this up!^_^ Very educational and interesting..thanks for sharing...

      • dmop profile image

        dmop 

        6 years ago from Cambridge City, IN

        Very good hub, I really enjoyed reading it and learning a bit about life in general. I don't mean to argue, and by land area covered you are correct, but the largest living organism is actually a grove of aspen trees (Populus tremuloides) in Utah nicknamed Pando, which is estimated to weigh 6,000 metric tons. Voted up and awesome.

      • PegCole17 profile image

        Peg Cole 

        6 years ago from Dallas, Texas

        This was fascinating TF Scientist. You presented this in a way that was interesting and made me want to read on through. Great hub!

        I really liked the fun facts part and I did not know this prior to reading your hub, along with a lot of other things you covered.

        "The largest organism on Earth is not the Blue Whale. It is a fungus (Armillaria ostoyae) that measures nearly 10 square kilometers in size."

        Truly enjoyable reading.

        Peg

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