Biotic factors are living factors that affect organisms, and abiotic factors are non-living factors that affect organisms.

Biodiversity refers to all the different kinds of life in one area. This includes humans, animals, plants, fungi, microorganisms, etc. All these things combined make up the natural world. In an ecosystem, all the organisms work together to support and maintain a balanced life. Biodiversity is important for the survival of all life on Earth. Without a wide range of organisms working together in an ecosystem, we wouldn’t have healthy ecosystems. 

Both biotic factors and abiotic factors affect diversity and distribution between animals.

What are biotic factors?

Biotic factors are living factors that affect other organisms in an ecosystem or shape the environment. These are basic ways in which living organisms can affect one, such as animals, plants, bacteria, fungi, etc.

There are different biotic factors. Examples of biotic factors are:

• Predation
• Grazing
• Food availability
• Disease
• Competition
• Grazing

Predation

The number of predators in an environment is a biotic factor. Predation is a living process that can influence another species. An increase in predators can result in the reduction of a population. Likewise, a decrease in predators can lead to an increase in prey. High numbers of prey can result in overgrazing, which can ultimately reduce biodiversity.  Grazing is a biotic factor as it is when animals graze or are grazed. The animals eat grass or other plants that are growing in an ecosystem. Animals that graze on plant species can influence the species of plants that survive. This is the same as predation. 

Food availability

Food availability is a biotic factor. If the availability of food reduces, then the number of organisms will also reduce as there will be more organisms competing for the resources.

Disease

Disease is a biotic factor, especially infectious diseases. Diseases can affect organisms, potentially resulting in a reduced population in an ecosystem. 

Competition

Competition is a biotic factor. Organisms compete for different things, such as food, water, mates, and space. Organisms competing for resources can also affect the population. Organisms that are out-competed can result in extinction. So essentially, the organisms that are able to are successful in competing for resources will survive, whereas the out-competed organisms will die. 

An easy way to identify biotic factors in an ecosystem is to think about all the ways that the organisms can affect one another. 

What are abiotic factors?

Abiotic factors are non-living factors that affect organisms. These include chemical or physical factors in an environment. 

There are different abiotic factors. Examples of abiotic factors are:

• Temperature
• Light intensity
• Water
• Soil PH & mineral content
• Gases
• Wind intensity/direction

Organisms are well adapted to live in specific environments; therefore, any change in these factors can affect organisms. 

Temperature

Temperature is an abiotic factor. Plants and animals have evolved to grow best at their optimum temperatures. Both an increase and decrease in temperature can affect organisms that are well-adapted to live in specific climates. This can result in migration. 

Light intensity 

Light intensity is an abiotic factor. Plants require sunlight in order to survive and grow via the process of photosynthesis. Photosynthesis is the process by which plants use sunlight, water, and carbon dioxide to produce oxygen and glucose. Some animals feed on plants (herbivores and omnivores). The intensity of light can affect the rate of photosynthesis, which will ultimately affect food availability. An increase in light intensity will lead to an increase in the rate of photosynthesis because the enzymes involved in this process will work faster. This can result in an increased rate of plant growth. On the other hand, a decrease in light intensity can lead to a decrease in the rate of photosynthesis which can affect plant growth as well as food availability for animals. 

Light intensity is also important for animals (cold-blooded and warm-blooded) as they use sunlight to stay warm. As animals spend more time in the sunlight, they will use less energy trying to stay warm or searching for food. Ultimately these animals can use the energy for growth instead. 

Water availability 

Water availability is an abiotic factor. The reason for this is that both plants and animals need water for survival; therefore, a change in the water level can also affect organisms.

Soil PH and mineral content 

Soil PH and mineral content are abiotic factors. Soil PH and mineral content are important as different plants need a specific PH and minerals in the soil in order for them to grow and survive. For example, some plants grow best in acidic soils, whilst other plants grow best in alkaline soils. 

Gases 

Gas is an abiotic factor. Carbon dioxide and oxygen are gases. Plants require carbon dioxide for photosynthesis, so an increase in the level of carbon dioxide will increase plant growth. On the other hand, a decrease in carbon dioxide level will also affect the rate of photosynthesis resulting in a decreased rate of plant growth. However, as carbon dioxide is an acidic gas and some plants are sensitive to acidic soil, an increase in carbon dioxide concentration may not be suitable for all plants.

A fall in the level of oxygen can affect organisms. Oxygen is dissolved in water and is used by animals for respiration.  

Now let’s look at examples of biotic factors and abiotic factors in an ecosystem.

A clownfish lives in the sea and oceans by the sea anemone. These fish feed off small invertebrates, algae, and some food scraps from the anemone. Clownfish are unable to survive in the wild thus they are protected by the species of sea anemone. Sea anemone has tentacles that sting and kill other species of fish; however, the clownfish is protected from its sting as it has a mucus coat on the outside of its skin. 

So what are the biotic factors and abiotic factors? What will happen if these change?

The biotic factors are:

1. Predation
2. Competition
3. Disease

The number of predators that prey on the clownfish can affect its population. Alongside this, competition for resources such as food and habitat can affect the clownfish. A lack of food or habitat can cause the clownfish to die. Lastly, disease is a biotic factor that can affect the clownfish. 

The abiotic factors are:

1. Oxygen and carbon dioxide concentration of water
2. Temperature of the water
3. Levels of acidity and salt
4. Light intensity
5. Pollution 

Clownfish require oxygen to breathe underwater; therefore, they require a food supply of oxygen. Dissolved oxygen is also required by other organisms, bacteria, and plants in aquatic ecosystems. Organisms use oxygen to breathe, and plants use oxygen to photosynthesise. A lack of oxygen will result in plant death which will lead to less food for organisms to eat. Moreover, a lack of oxygen will lead to organism death. 

The temperature of the water should also be optimum as anything too high or too low can cause the death of the clownfish is unable to survive. The levels of acidity can affect clownfish as it can lead to skin damage such as chemical burns of the fish’s skin. The PH level is affected by pollution such as acid rain or any waste discharged into the water. Acid rain is the result of burning fossil fuels. Industrial waste and coal mining produce acidic waste, which enters the water and affects aquatic ecosystems.  

Any factors that affect the sea anemone will also affect the clownfish, as this is the clownfish’s habitat and protection. Sea anemones require sunlight in order to survive and grow.