A Biologist Explains: What Is Life
Is Mimivirus alive?
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Although biology is the study of life, even biologists don’t agree on what ‘life’ actually is. While scientists have proposed hundreds of ways to define it, none have been widely accepted. And for the general public, a dictionary won’t help because definitions will use terms like organisms or animals and plants — synonyms or examples of life — which sends you round in circles.
Instead of defining the word, textbooks will describe life with a list of half a dozen features based on what it has or what it does. For what life has, one feature is the cell, a compartment to contain biochemical processes. Cells are often listed because of the influential cell theory developed in 1837-1838, which states that all living things are composed of cells, and the cell is the basic unit of life. From single-celled bacteria to the trillions of cells that make up a human body, it does seem as though all life has compartments.
A list of features will also mention what life does — processes like growth, reproduction, ability to adapt and metabolism . Such views are echoed by experts such as biochemist Daniel Koshland, who listed his seven pillars of life as program, improvization, compartmentalization, energy, regeneration, adaptability and seclusion.
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Life is an entity with the ability to adapt to its environment.
Characteristics Of Living And Non Living Things
We can find many things around us, from mountains and oceans to plants and animals. The earth in which we live is made up of several things. These things can be categorized into two different types Living and Non-living Things.
- All living things breathe, eat, grow, move, reproduce and have senses.
- Non-living things do not eat, grow, breathe, move and reproduce. They do not have senses.
Living things have life, though some might not show its evident signs. For instance, a tree would probably not react the same way a human would. It would not react when we hit it, and it might not be able to walk around. Though the signs of life displayed by them are not very observable, it does not make them non-living.
Let us have a detailed look at the important characteristics of living and non-living things and the difference between the two.
The Classification Of Living Things
Some scientists estimate that there are roughly 14 million species on Earth, though only approximately 1.9 million have been identified. For centuries scientists divided living things into two kingdomsplants and animals. Most organisms classified in the plant kingdom had chlorophyll and cellulose. The animal kingdom consisted of species that lacked chlorophyll or cellulose. This classification system was formalized in the 18th century by the biologist Carolus Linnaeus.
The system of Linnaeus was based on similarities in body structure, and it was completed more than a hundred years before the work of Charles Darwin, whose theory of evolution showed that the similarities and differences of organisms could be viewed as a product of evolution by natural selection. As biologists in the 20th century learned more about microorganisms and fungi, they recognized the need for a different classification system that would draw on the evolutionary relationships among organisms. A five-kingdom system began to be adopted in the 1970s that separated fungi into their own kingdom. It also created a kingdom called Monera for all prokaryotes and a kingdom called Protista for all eukaryotes that did not belong in the plant, animal, or fungi kingdoms.
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What Makes Something Living
All living organisms share several key characteristics or functions: order, sensitivity or response to the environment, reproduction, adaptation, growth and development, homeostasis, energy processing, and evolution. When viewed together, these characteristics serve to define life. Different sources may use slightly different terms to describe these characteristics, but the basic ideas are always present.
Is There Anything To Suggest That Viruses Might Be Alive
Its a little more complicated. In short, yes. Or at least theres plenty to suggest that the line between living and non-living might be a little blurry.
For one thing, some viruses do contain parts of the molecular machinery required to replicate themselves. The gigantic mimivirus an example so large that it was initially mistaken for a bacterium, and has a genome larger than that of some bacteria carries genes that enable the production of amino acids and other proteins that are required for translation, the process that for viruses turns genetic code into new viruses.
Read more:What happens in a virology lab?
Another sign of the fuzzy boundaries between living and non-living is that viruses share a lot of their genetics with their host cells. A 2015 study of protein folds, structures that change little during evolution, in thousands of organisms and viruses, found 442 folds shared across all and only 66 that were specific to viruses.
These findings suggest that viruses may have evolved alongside the very first living cells. As Gustavo Caetano-Anollés, one of the authors of the protein fold study, explains, We need to broaden how we define life and its associated activities.
The Royal Institution of Australia has an Education resource based on this article. You can access it here.
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If Viruses Are Not Alive How Can We Destroy Them
No matter what side of the debate you might be on, we know that viruses can be deactivated. Once they are inactive, they cannot infect a host cell.
There are two types of viruses, those with a lipid, or fatty outer shell and those that have a protein coating called a capsid. For the viruses that have a lipid shell you can use common soap to basically tear apart the outer coating and deactivate the virus. The remaining parts can then be washed down the sink and are harmless. The great thing about this is it only takes about 20 seconds of thorough hand washing with soap and water to do this. The virus that causes COVID-19 has a lipid shell so it can be deactivated using soap.
Viruses with protein coatings like the rhinoviruses and adenoviruses that cause the common cold are not deactivated by soap, but are still dislodged from our skin and surfaces so that they can be washed down the sink. This is also why washing your hands with soap and water is better than using a hand sanitizer. Hand sanitizers do not have the same effect of removing the viruses from our skin so they can be washed down the sink.
While we know many of you came to this page to find out whether viruses are alive or not, we’ve also been receiving many follow-up questions about the Coronavirus. Here are some resources we think may be helpful:
How Animals Obtain Food
Although many animals are green, animals do not contain chlorophyll. Therefore they cannot make food from carbon dioxide and water. This means that animals must get their food from other organisms, such as plants or other animals.
Like plants and algae, animals use food to produce different kinds of substances after they eat it. Animals use these substances for energy. They can turn sugary food into a starch called glycogen and store it in the liver, where it is ready for use when needed. When they eat more food than they need, they can store the extra food as fat.
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Securing Energy From Food
When plants make glucose from water and carbon dioxide, some atoms of oxygen are released from the combined materials. More oxygen is lost when glucose is converted into common sugar, starch, fat, or other food substances. As oxygen is removed, energy is stored in the made-over molecules.
The stored energy can later be obtained by cells through what is essentially a reverse process called oxidation. In a complex series of steps, oxygen is combined with food molecules, which change into simpler substances and give up energy. If complete oxidation takes place, the food becomes water and carbon dioxide again and gives up all its stored energy. Part of this energy is lost, but most of it remains available to the cell to carry out the functions of living.
Some organisms, especially microorganisms, can live in environments with little to no oxygen. These organisms also secure energy through chemical processes that change foods into simpler compounds. In one such process, called alcoholic fermentation, food gives up stored energy and changes into ethanol and carbon dioxide. Alcoholic fermentation by yeast organisms in bread dough, for example, changes sugar into alcohol and carbon dioxide. The carbon dioxide is what makes the dough rise, and the alcohol evaporates as the bread is baked.
Criteria For Differentiating Living Things From Non
For easy differentiation between living things and non-living things, scientists have come up with traits or characteristics that are unique to them.
The criterion for classification is necessary to avoid the wrong grouping. Hence, science developed a basis for classification. Anything that has life is considered as living beings.
For example humans, trees, dogs, etc.
Things which have no life in it are considered as non-living.
For example stone, mountain, watch, etc.
Scientists have discovered a few criteria for differentiating living things from non-living things.
Here are some of them:
Non-living things do not have any of the life processes, unlike living beings.
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Collaboration And The Diversity Of Life
The collaborative nature of living entities and processes is our essential starting point. Darwins theory of natural selection has, quite appropriately, focused a great deal of theoretical interest on questions of competition. This focus, however, has had the less salutary consequence of diverting attention from the equally important topic of cooperation and has culminated in the assumption that altruism, understood as the conferral of a benefit by one biological entity on another, is a profound theoretical problem. Although this is generally seen as a problem pertaining to organisms, a similar argument has notoriously been applied to the topic of genes. Richard Dawkins made famous the idea that genes are fundamentally selfish entities in competition with one another. From this point of view, it is truly remarkable that the whole consortium of genes in an organisms genome can nevertheless manage to collaborate on a task as momentous as development.
Atoms In Living Molecules
When atoms, the basic units of chemical elements, combine into chemical compounds, they form molecules. Organisms have many different kinds of molecules, from water and simple salts to complex molecules such as carbohydrates, fats, proteins, and deoxyribonucleic acid . One protein, called hemoglobin, carries oxygen in the blood and is what makes blood red. Hemoglobin contains atoms of six different elementscarbon, hydrogen, oxygen, nitrogen, sulfur, and iron.
The complexity of molecules in living things is made possible by carbon, which may be called the framework element. Because of its structure, carbon can link different kinds of atoms in various proportions and arrangements. Carbon atoms also join with each other in long chains and other arrays to make some of the most complex compounds known to chemistry.
Three other commonly found elements, oxygen, hydrogen, and nitrogen, are also important in the structure and function of living things. In the human body, for example, these elements, together with carbon, make up about 96% of the bodys weight. Oxygen and hydrogen are highly important in body processes that obtain and use energy from food. Water, a compound of oxygen and hydrogen, plays a very important role in life processes. Large amounts of nitrogen are found in protein, or body-building compounds. Nitrogen also is found in wood and in the substance called chitin that forms the shells of crustaceans, insects, jointed worms, and related creatures.
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Branches Of Biological Study
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The scope of biology is broad and therefore contains many branches and sub disciplines. Biologists may pursue one of those sub disciplines and work in a more focused field. For instance, molecular biology studies biological processes at the molecular level, including interactions among molecules such as DNA, RNA, and proteins, as well as the way they are regulated. Microbiology is the study of the structure and function of microorganisms. It is quite a broad branch itself, and depending on the subject of study, there are also microbial physiologists, ecologists, and geneticists, among others.
Another field of biological study, neurobiology, studies the biology of the nervous system, and although it is considered a branch of biology, it is also recognized as an interdisciplinary field of study known as neuroscience. Because of its interdisciplinary nature, this sub discipline studies different functions of the nervous system using molecular, cellular, developmental, medical, and computational approaches.
Characteristics Of Living Things:
The best way to understand these living characteristics criteria is to think about ourselves.
Imagine a human baby named Moo. Like other babies, Moo eats, drinks, and sleeps. This satisfies the first bullet point: Use materials and energy. Moo then grows bigger, learns how to walk and talk, and goes to school. He grows and develops. When his mother calls for him to wake up for school, Moo groggily rolls over in his bed. He responds to stimuli. When Moo is sick with the flu, his immune system is battling against the virus and is helping maintain a constant internal environment.
Eventually, Moo grows up, goes to college, gets a job, and gets married to his high school sweetheart. They have a baby named Moo Jr., Moos offspring whom he has passed down his traits to.
In general, humans adapt to their environments, and over generations, the species evolve.
And, of course, Mr. Moo and his son are made of cells.
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List The Defining Characteristics Of Biological Life
Biology is the science that studies life, but what exactly is life? This may sound like a silly question with an obvious response, but it is not always easy to define life. For example, a branch of biology called virology studies viruses, which exhibit some of the characteristics of living entities but lack others. It turns out that although viruses can attack living organisms, cause diseases, and even reproduce, they do not meet the criteria that biologists use to define life. Consequently, virologists are not biologists, strictly speaking. Similarly, some biologists study the early molecular evolution that gave rise to life since the events that preceded life are not biological events, these scientists are also excluded from biology in the strict sense of the term.
From its earliest beginnings, biology has wrestled with these questions: What are the shared properties that make something alive? And once we know something is alive, how do we find meaningful levels of organization in its structure?
What Are The Characteristics Of Life
The things that live here on Earth all have a lot in common. The tiny parts inside you that are responsible for helping you do everything you do, like walking, breathing, and digesting your food those tiny parts are almost exactly the same in all types of life, from flies and fish to trees and cows. All types of life have other things in common, too. All living things have a body of some kind. Some things have body parts that allow them to walk or fly or swim. These are things like legs and wings and fins. All of the living creatures we know have to eat food in order to have the energy to move and to grow. All living things can respond to their surroundings, just like you can taste something awful then spit it out and shout YUCK! And all life comes from other life just like how you came from your mother and father. So even though we look so different from other living things, we are much more the same than different.
Disciplinary Core Ideas
LS1.A: Structure and Function: All organisms have external parts that they use to perform daily functions. Different animals use their body parts in different ways to see, hear, grasp objects, protect themselves, move from place to place, and seek, find, and take in food, water and air. Plants also have different parts that help them survive and grow.
LS3.A: Inheritance of Traits: Young animals are very much, but not exactly, like their parents. Plants also are very much, but not exactly, like their parents.
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What Do We Mean By Alive
There is no single undisputed definition of life. Some of the more common questions to distinguish between living and non-living things are Does it have its own biological machinery to replicate? Does it multiply through cellular division? Does it have a metabolism?
For each of these questions, viruses receive a fail.