Light as an abiotic factor

The existence of every individual living organism is affected by two factors:

• Biotic or living factors
• Abiotic or non-living factors

The biotic factors refer to the other living organisms within the environment of an individual. They affect the existence of individuals because it is simply not possible to exist in isolation. Thus, an individual obligately or facultatively interacts with other organisms of the same or different species in the environment. This interaction could be for food, for protection, or for any other thing that could make the existence of organisms more successful.

The abiotic factors refer to all other factors apart from the living organisms found in the environment of individuals. These include factors that have to do with soils (edaphic factors), topographic factors, climatic factors such as temperature, pressure, etc; and hydrological factors. In other words, abiotic factors are otherwise known as environmental factors and these vary depending on the habitats of organisms.

One particular factor that tends to be of great importance to organisms irrespective of the environment where they find themselves is light. Every living organism is affected directly or indirectly by the amount of light that reaches the earth and the only natural source of light is the sun. In actual fact, the sun powers virtually everything else on earth either directly or indirectly.

Because of the non-flat shape of the earth, at every point in time, the sun is either on or off. In other words, when some areas of the world are experiencing darkness as a result of the sun setting, some other areas would be lit with the rays of the sun. Also depending on the location on the globe (poles, northern hemisphere, southern hemisphere, equator), the amount of light received at specific periods of the year varies accordingly.

The variation in the amount of light received has a major impact on the kind of organisms that exist in different regions of the world. Because of the high adaptation attribute of humans, they are able to survive in different regions of the world. However, the same cannot be said for other living organisms. Even in water bodies, the amount of light received varies with depth. Thus, variation exists in the kind of species found at different depths of the various oceans of the world.

Even though light plays a huge role in the distribution of living organisms, the factor does not work in isolation but in combination with other factors. That is, the existence of certain species of organisms in place is a result of complex interaction among the various biotic and abiotic factors.

^{By Dominic Alves - Flickr: Earth Daylight, Twilight and Night, CC BY 2.0, https://commons.wikimedia.org/w/index.php?curid=17084382}

Organisms that are adapted to low light may not be able to survive in intense light while those that are adapted to intense light may find it difficult to survive in low light.

In the case of plants, light is not just an environmental factor but a factor that makes it possible for them to manufacture foods for survival. Using their chlorophyll, plants are able to make use of inorganic materials in the form of carbon dioxide and water to manufacture carbohydrates. This process is otherwise known as photosynthesis and it is not important for just the survival of plants themselves, but for virtually all living organisms.

If plants are the only living organisms that can produce their own foods via photosynthesis, it simply means that all other organisms that are not plants would have to depend on plants directly or indirectly for their foods. This is why plants are generally known as primary producers in every food chain or food web.

When plants photosynthesize, they are able to accumulate more biomass and grow vegetatively with time. For flowering plants, a point is reached when the onset of flowering commences. Without flowering, angiosperms will not be able to produce fruits or seeds (fruits and seeds constitute the bulk of plant-derived foods for humans).

The onset of flowering in angiosperms is also affected by light, with many plants being confined to just vegetative growth if light conditions are not right. There are plants that require a daily period of light exposure of nothing less than 12 hours before they can flower (long-day plant) while some will never flower if they receive up to 12 hours of light per day (short-day plants).

This is one of the reasons why bringing plants from one part of the world to another may lead to the plants not being able to sexually reproduce unless there is a synchrony in the sunlight duration that corresponds to their requirement. In other words, it is easier for plants to adapt to other environmental factors in new environments and continue their vegetative growth. When it comes to flowering and reproducing sexually, however, the required daylight/night must be met before flowers buds will start emerging.

Summary

Light is one of the most important environmental factors as far as the existence of living organisms is concerned. Without light, producers cannot produce, and other organisms that depend on them cannot exist.

Apart from primary productivity, the length of daylight received by plants influences the onset of flowering, fruits, and seeds production. Some plants require more than 12 hours of light for flowering while others require less than 12 hours. If this condition is not fulfilled, such plants may stay in a vegetative state for the foreseeable time.