Characteristics of Life


Living things all share distinct characteristics that distinguish them from non-living things. If an organism holds all these characteristics, it is said to be living. Let's take a look at 8 different ones.



Living Things are Based on a Universal Genetic Code

external image dna-500.jpg

Organisms rely heavily on a molecule by the name of deoxyribose nucleic acid, or DNA, to contain valuable information regarding how to grow, live, and reproduce. Whenever a parent reproduces, its DNA is copied and passed to the offspring, which is why parents and offspring look quite similar to each other. Everything relating to hair colour, eye colour, or even bone structure is all determined by the information contained in DNA. Without this universal genetic code, organisms would be unable to function, neither have any offspring to make a particular species exist.



Living Things Reproduce

external image cycle2.gif


In order for a species to thrive, the organisms belonging to a particular species must first reproduce. In simplest terms, to reproduce means the production of new similar organisms. This can be achieved in two ways, either by asexual reproduction (only one organism produces), or by sexual reproduction (two organisms produce together). In the above diagram, the frog lays eggs which eventually turn into a tadpole, and ultimately into a frog. This process can continue forever, leaving us with an unlimited amount of one species. Inheritance is a key factor of reproduction, which is the passing of genes from one generation to the next. DNA controls much of the information needed to reproduce, making it one of the most vital molecules of life. Therefore, humans are dependent on DNA for survival as a species.



Living Things Obtain and Use Material and Energy

external image animals_eating_animals_1.jpg

Organisms also differ from non-living things in the sense that they must take in materials, or nutrients (energy) in order to grow, develop, and reproduce. While all organisms need to obtain these, some organisms obtain this in different ways than others (ie. autotrophs vs. heterotrophs). Some organisms use their surroundings or other organisms for energy, while others use the sun as the main source of their energy. While an organism takes in all this material, it must also rid of the excess waste, by use of excretion, also a characteristic of living things only. Perhaps the single most important process of using this energy is metabolism, which is the combination of chemical reactions through which an organism builds up or breaks down materials. Without metabolism, materials and energy would be useless to an organism, such as an organism.



Living Things Grow and Develop

external image Bflylifecycle.GIF


Once new organisms are created after the process of reproduction, they must go through a life cycle, just like their parent did. Each organism differs in their pattern of growth and development. For instance, multicellular (made up of more than 1 cell) organisms grow by adding more cells, by means of cell division. Once these cells begin to divide, they show some differences as well as function differently. An organism's pattern of development is determined by the DNA in which is possesses. If we as humans did not grow nor develop, we would not be sexually mature, resulting in no reproduction and ultimately extinction of mankind.




Living Things Respond to Their Environment

external image stimresp1.jpg

When organisms are in their environment, a variety of activities are occuring in the background. Organisms detect and respond to stimuli in their environment. For example, if an organism hears an unfamiliar noise, its ears will often perk up and will face in the direction of the origin of the unknown noise. Humans must be alert of their surroundings, in case danger lurks or they need to wake up for school (alarm clock).


Living Things Maintain a Stable Internal Environment

In order to survive in even the most extreme environments, all organisms need to keep their internal environment stable, despite major change in the outside environment. This in other words, is known as homeostasis. Without this, organisms would be unable to adapt to these new conditions, ultimately killing the organism. For example, humans have a relatively warm internal temperature, which varies ever so slightly despite harsh conditions externally. If we didn't have homeostasis, we would be unable to adjust to changes in our environment.




Living Things are Made Up of Cells

external image Epithelial-cells.jpg

To be classified as an organism, and to live, it must consist of at least one cell. These are very often considered the smallest unit of life. Cells on their own can grow, respond to stimuli, and reproduce. Cells are composed of smaller substances known as organelles. Most organisms contain tons of cells, but there are some that contain as little as a single cell, known as unicellular. There are two types of cells, prokaryotic and eukaryotic. The cell in a human and most organisms contains alot of information and hold many functions such as DNA, how to make proteins, where to store waste etc. Without the cell, we could not do anything.



Living Things Evolve


external image dn13620-1_300.jpg
Organisms change over time, although usually a very long period of time (millions of years), which is also known as evolution. This has been confirmed through fossil research, and the structure of protein as well as the information in DNA. With evolution comes natural selection, which provides variation in a species, including humans. If many people die from a disease, some may build an immunity to it, and will reproduce in the future with offspring carrying that same trait.




Significance

The significance of these characteristics of life is that we, as humans, must partake in all these activities to survive as a species. We are made up of cells, the basic unit of life, which contains DNA which store all of our genetic information which gets passed down to our offspring in due time. Without this, no species would be able to survive as there would be no offspring to pass down the traits to.




Terms to define:



Unicellular:

Beings made of one cell.

003_Structure_of_an_amoeba.jpg





Multicellular:

Beings made of more than one cell.

images.jpg





Colonial:

Colonial organisms are individual organisms of the same species that live closely together, usually for mutual benefit, such as stronger defence or the ability to attack bigger prey. Some insects (ants and honey bees, for example) live only in colonies. The difference between a multicellular organism and a colonial organism is that individual organisms from a colony can, if separated, survive on their own, while cells from a multicellular lifeform (e.g., cells from a brain) cannot

ant_colony.jpg



Eukaryotic:

Cells with nuclei and membrane-bound organelles that supports them (Eu- means true = true nucleus).

cell_structure.jpg




Prokaryotic:

Cells without nuclei and membrane-bound organelles to support them. (Pro- means before).

300px-Average_prokaryote_cell-_en.svg.png




Autotroph:

An organism that can make its own food by using inorganic molecules around their environment (e.g. plant).

flowrs.jpg





Heterotroph:

A living being that cannot make it’s own food like autotrophs and depends on nutrients around their surroundings to survive.


Herbivore.jpg



Metabolism:

Collection of all chemical reactions inside of an organism, such as human beings (inside of human beings) [e.g. Digestion, blood-clotting, etc.]

blood_clot.jpg



Adaptation:

Physical structure and behaviour of a certain independent living being that allows it to survive and respond to stimuli.

owl_adaptation.jpg




Organic compound:

Compounds that contain the carbon atom.



benzine.jpg






Motile:

The ability to move spontaneously and actively, consuming energy in the process. May also refer to an organism's ability to move food through its digestive tract, i.e., peristaltics (gut motility, intestinal motility, etc.)



biol2420photoatlas047003.jpg




Spore:

A reproductive structure that is adapted for dispersal and surviving for extended periods of time in unfavorable conditions. Spores form part of the life cycles of many bacteria, plants, algae, fungi and some protozoa.

Fern_spores_large.jpg