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Biotic and Abiotic Factors

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Biotic and Abiotic Factors

Organisms must adapt to conditions set by their environments to survive and reproduce. We will discuss the definition of biotic and abiotic factors in an ecosystem. In addition, we will look at how biotic and abiotic factors influence the adaptation of species. Finally, we will present a desert ecosystem as an example.

What Are Biotic and Abiotic Factors in an Ecosystem?

An ecosystem is a biological community composed of all living organisms (biotic factors) and their interaction with the physical environment (abiotic factors). The interaction between biotic and abiotic factors influences species adaptations to their specific environment.

What Is the Definition of Biotic and Abiotic Factors?

In this section, we will briefly discuss the definition and some pertinent examples of biotic and abiotic factors.

Biotic Factors

Biotic factors are living organisms within an ecosystem, for example, animals, plants, and fungi. There are three main types of biotic factors: autotrophs, heterotrophs, and detritivores.

  • Autotrophs are organisms that produce their own food.

    • Plants and algae, for example, use sunlight to produce food from carbon dioxide and water (a process called photosynthesis).

    • Other organisms like bacteria produce food using chemicals instead of sunlight as the energy source (chemosynthesis).

  • Heterotrophs are organisms that consume other organisms.

    • Herbivores like deer and cows feed on plants.

    • Carnivores like lions and tigers feed on other animals.

    • Omnivores like humans and pigs feed on both animals and plants.

  • Detritivores are heterotrophs that consume dead or decaying organisms. By breaking down dead and decaying material into inorganic nutrients, detritivores contribute to nutrient cycling in an ecosystem.

    • Examples of detritivores are earthworms, maggots, sea cucumbers, and crabs.

Abiotic Factors

Abiotic factors are non-living chemical and physical environmental conditions within an ecosystem. Examples include temperature, water, wind, light, and chemical composition.

Ecosystem: a biological community composed of all living organisms and their interactions with the physical environment

How Do Biotic and Abiotic Factors Influence the Adaptation of Species?

Biotic and abiotic factors are selection pressures. The interaction of organisms with biotic and abiotic factors can affect their evolutionary fitness. Selection pressures can increase or decrease the occurrence of a trait in a population of organisms at a given time.

Traits that help organisms survive and reproduce in their specific environments are called adaptations. Species with favorable traits that survive in their environment can reproduce more because of those traits; this is natural selection. Over time, those with favorable traits will outnumber those without them, eventually changing the heritable traits of the entire population of a species, a process called evolution.

Selection pressures are the external factors that affect an organism’s chances of surviving its environment.

Evolutionary fitness: the ability of organisms to survive and reproduce.

How Do Biotic Factors Influence The Adaptation of Species?

Living organisms interact in ways that affect each other’s survival and reproduction. Interactions between biotic factors can be divided into five main types of ecological relationships: competition, predation, commensalism, mutualism, and parasitism.

Competition

Competition is when organisms compete for resources, such as food and territory.

For example, plants tend to compete for sunlight as it serves as their primary energy source. In rainforests, tall, old-growth trees reach out to the sun, and their branches form the canopy--the uppermost layer of the forest habitat--and block out the sun.

When an old-growth tree falls, a gap forms in the canopy, and the plants in the layers below rush to maximize the sun exposure. Some are adapted to avoid shade through the elongation of their stem or petioles. Others can tolerate shade by increasing the surface area of their leaves.

Predation

Predation is when organisms consume other organisms to obtain energy.

Let’s take the predatory relationship between lions and zebras (Fig. 1) as an example. Traits that help zebras escape or hide from lions (like speed and camouflage) increase their chances of survival. On the other hand, lions have adapted to their prey's increased size and strength by stalking and hunting in groups. More intelligent lions can use better tactics to corner their prey, so they have better chances of feeding and surviving.

Biotic and abiotic factors fig. 1: Lions stalk their prey and hunt in groups | StudySmarter

Figure 1. Lions stalk their prey and hunt in groups. Source: Aliparsa, CC BY-SA 3.0, via Wikimedia Commons.

Commensalism

Commensalism is when one organism benefits from the interaction while the other organism is unaffected.

An example of this is the remora (family Echineidae), that have a flat disk-like structure that allows it to attach itself to sharks and other fishes, giving it access to a free ride and a free meal since it feeds on the leftovers of its host (Fig. 2).

Biotic and abiotic factors fig. 2: A remora gets a free ride from a whale shark | StudySmarter

Figure 2. A remora gets a free ride from a whale shark. Source: Nicholas Lindell Reynolds, CC BY-SA 4.0, via Wikimedia Commons.

Parasitism

Parasitism is when one organism benefits from the interaction while harming the other organism.

For example, female brown-headed cowbirds (Molothrus ater) lay their eggs in the nests of other birds, including the savannah sparrow (Passerculus sandwichensis) (Fig. 3). Because the savannah sparrow cannot tell the fledglings apart, they take care of all of them, including those of the cowbirds. Cowbirds are much larger than the savannah sparrow, so they eat more food than the other fledglings.

Biotic and abiotic factors fig. 3: The brown-headed cowbird fledgling is larger than the savannah sparrows fledglings | StudySmarterFigure 3. The brown-headed cowbird fledgling is larger than the savannah sparrows fledglings. Source: Kati Fleming, CC BY-SA 3.0, via Wikimedia Commons.

Mutualism

Mutualism is when both organisms benefit from the interaction.

Interactions between flowering plants and their pollinators are a good example of mutualism. Most flowering plants are pollinated by animals such as birds and insects. This interaction helps flowering plants to reproduce and diversify. On the other hand, pollinators get to eat pollen or nectar. Other pollinators like bees can also use waxes to build their hives and certain compounds to attract mates.

As a result of this relationship, flowering plants could benefit from traits that attract pollinators. For example, some flowering plants adapt by producing pigment that gives them a bright color which is attractive to some pollinators, like hummingbirds. On the other hand, hummingbirds adapt to the flowers available in the ecosystem through their different beak lengths and shapes.

How Do Abiotic Factors Influence the Adaptation of Species?

Abiotic factors also play a major role in the ecosystem. Abiotic factors can limit or enhance the ability of organisms to survive and reproduce. Over time, organisms inherit adaptations that suit their environmental conditions.

Abiotic factors like wind and water can aid in dispersing pollen and seeds, helping plants reproduce. For example, the dipterocarp fruit (Fig. 4) has "wings" that allow it to use the wind draft to spread as far as possible.

Biotic and abiotic factors fig. 4: Dipterocarp fruits have two wings that let them ride the wind draft to spread | StudySmarter

Figure 4. Dipterocarp fruit. Dipterocarps (which literally translates to “two-winged fruits) are tall trees usually found in tropical rainforests. Source: Mokkie, CC BY-SA 3.0, via Wikimedia Commons.

Abiotic factors like temperature, salinity, and water pH can greatly affect marine life. Coral bleaching, for instance, occurs when the water temperature gets too high. Figure 5 shows how coral bleaching occurs due to factors such as increased temperatures, storm runoff and pollution, and high solar irradiance.

Biotic and abiotic factors fig. 5: Rise in water temperature can cause coral bleaching | StudySmarter

Figure 5. Coral and microscopic algae depend on each other for survival. When water temperatures get too high, the microscopic algae leave the coral tissue and the coral slowly dies. Source: Logwo18, CC BY-SA 4.0, via Wikimedia Commons.

Comparing and Contrasting Biotic and Abiotic Factors

Let's look at some similarities and differences between biotic and abiotic factors.

Similarities Between Biotic and Abiotic Factors

Biotic and abiotic factors are both components of an ecosystem that interact and influence the adaptation of a species by increasing or decreasing its chances of survival and/or reproduction.

Differences Between Biotic and Abiotic Factors

The main difference between biotic and abiotic factors is that biotic factors are comprised of living things (such as plants, animals, and fungi). In contrast, abiotic factors are comprised of non-living chemical and physical environmental conditions in an ecosystem (such as wind, water, and light). Another difference is that biotic factors depend on abiotic factors, while abiotic factors exist independent of biotic factors.

Example of Biotic and Abiotic Factors in an Ecosystem

Let's use a desert ecosystem as an example. What are some biotic and abiotic factors in a desert ecosystem and how do they interact with each other?

A desert ecosystem is a dry environment that doesn’t get much rainfall. Water is an abiotic factor that causes biotic factors like plants and animals to make adaptations.

Camels, for example, can regulate their body temperature to prevent water loss by sweating. Succulent plants like cacti have spines which are modified leaves that conserve water by preventing water loss during the day and collecting condensed water vapor at night. Cactus seeds also have the ability to stay dormant until there is enough rainfall to support the growth of a seedling.

Temperature and sand are other abiotic factors that could affect plants and animals. Camels have wide feet that help them walk on sand and thick fur that keeps them warm at night. Some lizard species that live in a desert ecosystem have adapted by burrowing into the sand to hide from the intense heat of the sun and by having toes with spiny scales that do not sink in the sand.

Organisms in the desert ecosystem have also made adaptations to biotic factors. For example, succulents (Fig. 6) have thorns that protect them from herbivores, while camels have thick, leathery mouths that allow them to feed on thorny plants.

Biotic and abiotic factors Fig. 6: Cacti have modified leaves called spines | StudySmarter

Figure 6. Cacti have modified leaves called spines that conserve water and protect them from herbivores. Source: Chris Hunkeler from Carlsbad, California, USA, CC BY-SA 2.0, via Wikimedia Commons.

Biotic and Abiotic Factors - Key takeaways

  • An ecosystem is a biological community composed of all living organisms (biotic factors) and their interaction with the physical environment (abiotic factors).
  • The interaction of organisms with biotic and abiotic factors can affect their survival and reproduction.
    • Biotic factors (living organisms) interact with each other in ways that affect each other’s survival and reproduction. Interactions between biotic factors can be divided into five main types of ecological relationships, namely:
      • Competition: when organisms compete for resources, such as food and territory.
      • Predation: when organisms consume other organisms to obtain energy.
      • Commensalism: when one organism benefits from the interaction while the other organism is unaffected.
      • Parasitism: when one organism benefits from the interaction while the other organism is harmed.
      • Mutualism: when both organisms benefit from the interaction.
    • Abiotic factors (non-living environmental conditions) can limit or enhance the ability of living organisms to survive and reproduce. Examples of abiotic factors are temperature, salinity, wind, and water.
  • Biotic and abiotic factors are selection pressures: they increase or decrease the occurrence of a trait in a population of organisms at a given time. Organisms inherit adaptations that suit their environmental conditions, and over time, populations evolve with adaptations that are better suited to the biotic and abiotic factors in their ecosystem.

Frequently Asked Questions about Biotic and Abiotic Factors

An ecosystem is a biological community composed of all living organisms (biotic factors) and their interaction with the physical environment (abiotic factors).

In an ecosystem, biotic factors are living organisms while abiotic factors are non-living chemical and physical environmental conditions.

Biotic and abiotic factors are components of an ecosystem: biotic factors are living things, while abiotic factors are non-living things. These factors interact and influence the adaptation of species.

Biotic factors (living organisms) interact in ways that affect each other’s survival and reproduction. Interactions between biotic factors can be divided into five main types of ecological relationships: competition, predation, commensalism, mutualism, and parasitism. On the other hand, abiotic factors (non-living environmental conditions) can limit or enhance the ability of living organisms to survive and reproduce.

Biotic factors (living organisms) interact with each other in ways that affect each other’s survival and reproduction. For instance, plants adapt to be able to compete with other plants over resources like sunlight and water. 


Abiotic factors (non-living environmental conditions) can limit or enhance the ability of organisms to survive and reproduce. For example, abiotic factors like wind and water can aid in the dispersal of pollen and seeds, helping plants reproduce.


Over time, organisms inherit adaptations that suit their environmental conditions.  

Final Biotic and Abiotic Factors Quiz

Question

What is an ecosystem?

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Answer

An ecosystem is composed of all living organisms and their interaction with the physical environment.

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Question

What are biotic factors in an ecosystem?

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Answer

Biotic factors are living things in an ecosystem.

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Question

What are abiotic factors in an ecosystem?

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Answer

Abiotic factors are non-living things in an ecosystem.

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Question

What are biotic factors that produce their own food called?

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Answer

Autotrophs

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Question

What are biotic factors that consume other organisms called?

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Answer

Heterotrophs

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Question

What are biotic factors that feed on dead or decaying organisms?

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Answer

Detritivores

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Question

Is temperature a biotic or an abiotic factor?

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Answer

Abiotic factor

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Question

Are predators a biotic or an abiotic factor?

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Answer

Biotic factor

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Question

Is the pH level of soil a biotic or an abiotic factor?

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Answer

Abiotic factor

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Question

Coral and microscopic algae depend on each other for survival. When water temperatures get too high, the microscopic algae leave the coral tissue and the coral slowly dies. In this example, what abiotic factor affected the survival of corals?

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Answer

Water temperature

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Question

What is the difference between biotic and abiotic factors?

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Answer

Biotic factors are living organisms while abiotic factors are non-living environmental conditions within an ecosystem.

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Question

How are biotic and abiotic factors related?

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Answer

Biotic and abiotic factors are both selection pressures that are found within an ecosystem.

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Question

How do biotic and abiotic factors interact?

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Answer

The interaction between biotic and abiotic factors determines the characteristics of an ecosystem. The survival and reproduction of living organisms (biotic factors) depend on abiotic factors such as temperature, wind, and water.

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Question

Organisms benefit from each other in what type of interaction between biotic factors?

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Answer

Mutualism

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Question

Organisms consume other organisms in what type of interaction between biotic factors?

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Answer

Predation

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