What does it mean to be alive?

You are alive, and so am I. My cat, Charlie, is purring and is very much alive.  The tree just outside my window has new leaves which are emerging for the spring. Although sometimes I wonder, I don’t believe that my computer is alive nor is my desk and chair.

What is it that defines life? How can we tell that one thing is alive and another is not?, Amazingly, it is surprisingly difficult to come up with a precise definition of life.  Many definitions allow us to separate living things from nonliving ones, but they don’t actually pin down what life is. With so many human beings dying from covid-19, this is a question we should be asking.

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So what allows living organisms to survive?

Biologists have identified various traits common to all the living organisms. Although nonliving things may show some of these characteristic traits, only living things show all of them.

  • Living things are highly organized, meaning they contain specialized, coordinated parts. All living organisms are made up of one or more cells, which are considered the fundamental units of life.
  • Life depends on an enormous number of interlocking chemical reactions. These reactions make it possible for organisms to do work—such as moving around or catching prey—as well as growing, reproducing, and maintaining the structure of their bodies. Living things must use energy and consume nutrients to carry out the chemical reactions that sustain life.  
  • Living organisms regulate their internal environment to maintain the relatively narrow range of conditions needed for cell function. For instance, your body temperature needs to be kept relatively close to 98.6 degrees Fahrenheit or 37 degrees Celsius.  
  • Living organisms undergo regulated growth. Individual cells become larger in size, and multicellular organisms accumulate many cells through cell division. You yourself started out as a single cell and now have tens of trillions of cells in your body. Growth depends on pathways that build large, complex molecules such as proteins and DNA.
  • Living organisms can reproduce themselves to create new organisms. Reproduction can be either asexual, involving a single parent organism, or sexual, requiring two parents. Single-celled organisms can reproduce themselves simply by splitting in two! In sexual reproduction, two parent organisms produce sperm and egg cells containing half of their genetic information, and these cells fuse to form a new individual with a full genetic set.
  • Living organisms show “irritability,” meaning that they respond to stimuli or changes in their environment. For instance, people run from bumblebees, many plants turn toward the sun; and unicellular organisms may migrate toward a source of nutrients or away from a noxious chemical.
  • Populations of living organisms can undergo evolution, meaning that the genetic makeup of a population may change over time. In some cases, evolution involves natural selection, in which a heritable trait, such as darker fur color or narrower beak shape, lets organisms survive and reproduce better in a particular environment. Over generations, a heritable trait that provides a fitness advantage may become more and more common in a population, making the population better suited to its environment.

Living organisms have many different properties related to being alive, and it can be hard to decide on the exact set that best defines life. Thus, different thinkers have developed different lists of the properties of life. For instance, some lists might include movement as a defining characteristic, while others might specify that living things carry their genetic information in the form of DNA. Still others might emphasize that life is carbon-based. Me, well I can talk and think and feel so I must be alive

How well do the properties above allow us to determine whether or not something is alive?  The living things we talked about earlier—humans, cats, and trees—easily fulfill all seven criteria of life. We, along with our feline friends and the plants in our yards, are made of cells, metabolize, maintain homeostasis, grow, and respond. Humans, dogs, and trees are also capable of reproducing, and their populations undergo biological evolution.

Nonliving things may show some, but not all, properties of life. For instance, ice cystals are organized—though they don’t have cells—and can grow but don’t meet the other criteria of life. Similarly, a fire can grow, reproduce by creating new fires, and respond to stimuli and can arguably even be said to “metabolize.” However, fire is not organized, does not maintain homeostasis, and lacks the genetic information required for evolution.

The question of what it means to be alive remains unresolved. For instance, viruses like the coronavirus—tiny protein and nucleic acid structures that can only reproduce inside host cells—have many of the properties of life. However, they do not have a cellular structure, nor can they reproduce without a host.

For these reasons, viruses are not generally considered to be alive. However, not everyone agrees with this conclusion, and whether they count as life remains a topic of debate.  Right now, I think most consider covid-19 to be very much alive, particularly if you become the host.

So, what about the idea of love?

Life and love are intertwined. Love brings joy to the living and without it, life often lacks meaning and purpose.   Love is a complex set of emotions, behaviors, and beliefs associated with strong feelings of affection, protectiveness, warmth, and respect for another person. Love can also be used to apply to animals, to principles, and to religious beliefs. For example, a person might say he or she loves his or her dog, loves freedom, or loves God.

Love has been a favored topic of philosophers, poets, writers, and scientists for generations, and they have often debated its meaning. While most people agree that love implies strong feelings of affection, there are many disagreements about its precise meaning, and one person’s “I love you” might mean something quite different than another’s. Some possible definitions of love include:

  • A willingness to prioritize another’s well-being or happiness above your own.
  • Extreme feelings of attachment, affection, and need.
  • Dramatic, sudden feelings of attraction and respect.
  • A fleeting emotion of care, affection, and like.
  • A choice to commit to helping, respecting, and caring for another.
  • All or some of the above.

“life and love are very precious when both are in full bloom.”

― Louisa May Alcott, Little Women

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