Do animals have jobs? Not in the traditional 9-5 sense, but let's think about this question for a second! Similar to how students at your high school occupy different roles, such as cheerleaders, band members, athletic teammates, and so on, animals occupy specific roles in their environment! This is, for example, how over 2,000 species of fish can coexist in the Amazon River: some species of fish have a diet of seeds and fruit, while others are carnivores and eat smaller fish for prey.
These different roles are known as niches! Together, we will explore the complexities of ecological niches and learn more about how species carry out their "jobs"!
- First, we will look at the definition of a niche in Biology.
- Then, we will explore the different types of niches.
- After, we will learn about the importance of ecological niches.
- Lastly, we will take a look at an ecological niche diagram.
Definition of Niches in Biology
In biology, a niche is defined as follows:
An ecological niche is a species' unique ecological role determined by the way it interacts with abiotic and biotic resources in its habitat to survive and reproduce.
Habitat refers to an organism's physical space, such as deserts, grasslands, and marine habitats.
While the concept of a niche seems quite simple, understanding what makes up a species' role can vary!
When the concept of a biological niche first came about, it was defined solely as the environmental (abiotic) factors that a species needed to survive. Shortly after, another definition arose that focused solely on a species' role, defined as interactions with other species. Combining these two concepts lets us arrive at the definition above, which emphasizes a species' niche as interacting with environmental factors (abiotic) and other species (biotic)!
Let's briefly examine these two concepts.
Environmental characteristics of niches
Some important abiotic factors influencing a species' niche include temperature, climate, water availability, and other nonliving factors such as salinity for aquatic life and soil nutrients for plants.
Abiotic factors refer to the nonliving components of an ecosystem, including chemical and physical environmental conditions.
An easy way to think of these factors is that they are the environmental conditions a species requires to survive in its habitat.
For example, a puffin bird's niche in a subarctic habitat might, in part, be defined by the cold temperature of the sea they inhabit during the winter months and its food source. The 'interaction' occurs here between species and abiotic factors (temperature).
When considering the niche of a species, we must consider abiotic factors as they directly impact a species' ability to eat, survive, reproduce, and thrive.
Species interaction
In addition to abiotic factors, we must consider biotic factors.
Biotic factors refer to all the living organisms in an environment and their interactions.
Some common biotic interactions include the presence of predators, competition within and between species, and vegetation.
The presence of predators can cause species to adapt to niches' by altering their food source and limiting their living space.
On the other hand, limited resources can lead to competition--a biotic relationship where individuals struggle to obtain resources they require for survival--which can have a substantial impact on populations. Competition can be interspecific or intraspecific:
For example, plants of different species can compete over light availability, a resource which can be limited especially in the forest floor.
For example, male birds of the same species in the same area might compete over mates.
The presence of predation and competition are some of the reasons niches are so important in the first place. Keep reading further to see species interaction's important role in developing niches!
What are the types of niches?
Two different types of niches are recognized: fundamental and realized.
A fundamental niche refers to all the environmental conditions under which a species could survive and reproduce without species interaction. It only considers abiotic environmental factors and does not include interaction with other species.
Wait a minute, how can a niche be accurate if it doesn't consider other species?
Well, this is why fundamental niches are a poor indicator of a species' true niche and are often thought of as potential niches. A species can potentially live in and tolerate the environmental conditions defined by a fundamental niche, but often, due to the presence of species interaction, the space it can actually survive is much smaller. This is where a realized niche comes in.
A realized niche is the actual niche in which the species lives and survives, taking into account species competition and predation.
Let's say the fundamental niche of bird species A is a whole tree that provides food. Theoretically, in the absence of predation or competition, bird species A could survive on any part of the tree. However, because bird species B utilizes the bottom half of this same tree for food, species A is limited to the top half if it wants to survive. One aspect of the realized niche of species A is the top half of the tree.
Though this is a simple example, there are two important aspects to take away here:
- Fundamental niches are always larger than realized niches because they include every possible place of survival (the tree vs. a part of the tree)
- Fundamental niches are theoretical/ideal niches that are mostly unrealistic, while realized niches are where the species will actually exist in its real-life conditions.
We can actually break the realized niche of species' into two categories: specialists and generalists! Based on their names, we can tell that species that are specialists have a specialized niche, while species that are generalists have a broader niche.
Stay tuned as we will cover examples of specialists and generalists at the end!
What is the importance of ecological niches?
You may be thinking, "What's the big deal that different species have different roles in their habitat; I can tell that from walking outside! Why do niches matter?" The importance of ecological niches comes down to providing species with the chance to survive in habitats with limited resources and competition with other species. Within a specific habitat, there are finite resources (food, water, shelter, etc.) and many different species competing for them to survive.
If two species constantly compete for the same resources, eventually, one species will outcompete the other and drive it to localized extinction (extirpation) or even extinction if the population is restricted to one area. This is known as the competitive exclusion principle.
So, when each species has a unique role to play within a habitat, it promotes balance and allows species to survive with a minimal and manageable amount of competition.
But wait, didn't we just discuss an example where two species of birds had very similar niches and lived in the same habitat? Yes! Coexistence is possible in species when their niches partly overlap because they can adapt to survive through resource partitioning.
Resource partitioning is the division of resources (food or habitats) to avoid competition between species.
Ecological niche diagram
Take a look at the diagram below. What can you observe?
We can see that both Warbler species have the same fundamental niche: the whole tree. Due to competition between them, they have a realized niche depending on the elevation at which they eat from the spruce tree. This is also an example of habitat resource partitioning!
Another example of resource partitioning is found in the African savannah. Giraffes and several species of antelope (kudu and steenbok) all eat leaves from the same tree; however, the resources are divided based on the height of the leaves in the tree. The smallest of these three species, the kudu, can reach only the leaves closest to the ground. The steenbok eats the leaves at a medium height, while the giraffes eat the leaves at the very top.
Examples of Niches
Even though we've covered several different niches already, let's end by looking at two more to really bring this concept to life.
Remember earlier when we briefly covered specialists vs generalists? Well, let's go over an example of each!
Specialists are species that have a very narrow niche. They often need particular environmental conditions to survive and do not adapt well to different environments.
An example of this would be the koala, whose diet is exclusively eucalyptus trees and is only found in certain parts of Australia.
On the other hand, generalists are very adaptable and can thrive under many environmental conditions.
We can see this in species like cockroaches with a broad niche as they can survive in varying hot and cold climates and will eat dead plants, animals, and even waste.
Niches - Key takeaways
- An ecological niche is a species' role in its habitat defined as all its interactions with abiotic and biotic factors.
- A fundamental niche is all the possible environmental conditions a species could survive in without other species' interaction.
- A realized niche is the actual place where a species lives and includes all of its interactions with the other species around it.
- There are specialist species with a very specific niche and generalist species with very broad niches.
- Niches are important because they promote biodiversity and allow species to thrive in their habitat by reducing competition.
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