Types of Interactions – Limiting Factors

Key Concepts

• Ecosystem
• Limiting factors
• Carrying capacity
• Types of interactions
• Predator and prey relationship
• Predator adaptations
• Prey adaptations

Introduction: 

A group of organisms belonging to the same species and living in the same area is called a population. Whereas a community is a group of different species living in a particular area interacting with each other. An ecosystem comprises a community of different organisms along with abiotic factors. 

Explanation: 

In natural communities, the size of populations of different organisms living together tends to vary greatly. This variation is seen because everything in the environment affects every other thing. Most living things produce a large number of offspring, but only a few survive. For example, a female frog may lay hundreds of eggs in a pond. But in a few months, the population of frogs will be the same as it was a year ago. Why do you think the pond won’t be overrun with frogs? 

Limiting factors: 

A population cannot grow without limits because the environment has a limited amount of food, water, living space and other resources. When a resource is so scarce that it limits the size of a population, it is called a limiting factor. 

For example, food becomes a limiting factor when the size of a population becomes very large for the amount of food that is available. A single resource such as food or space can act as a limiting factor to a population’s size.  

Effects of limiting factors: 

A limiting factor also can affect other populations in the community indirectly. For example, a drought might lead to a decrease in the number of seed-producing plants in a forest. 

Lesser plants mean that food can become a limiting factor for a deer population that eats the plants and for a bird population that feeds on the seeds of those plants. 

In addition, food could become a limiting factor for animals that feed on the bird and deer population. 

As a result, a limiting factor can affect an entire community. 

Carrying capacity: 

The largest population that any environment can support is considered as its carrying capacity. If a population grows larger than its carrying capacity, the limiting factors in the environment cause the individuals to die or leave. As a result, the size of the population decreases. 

For example, after a rainy season, producers such as plants may produce a large number of leaves or seeds. This large quantity of food may cause a primary consumer like a herbivore or a bird population to grow. 

If the next year receives less rainfall, there won’t be enough food to support the large population of herbivores. In this way, a population can become larger than its carrying capacity, but only for a short duration. The lack of food and other limiting factors will eventually cause the population to decrease to a level that the environment can support. 

Types of interactions: 

Ecologists have described three main relationships through which species and individuals affect each other. They are as follows: 

1. Predatory and prey relationships 

2. Competitive relationships  

3. Symbiotic relationships 

 

Predatory and prey relationships:

 In nature, many interactions between species consist of one organism eating the other in order to obtain energy and nutrients. The organism that gets eaten is called prey. Whereas the organism that eats the prey is called a predator. When a frog eats a fly, the fly is the prey, and the frog is the predator. 

Predator adaptations: 

In order to survive, predators must be able to catch their prey. To achieve this, predators have developed a wide variety of methods and abilities. 

For example, the cheetah is able to run very fast to catch its prey. The cheetah’s speed gives the cheetah an advantage over other predators which are competing for the same prey.  

Other predators, like the goldenrod spider, ambush their prey. The goldenrod spider blends in with the yellow flower so that insects don’t see it. Now, all the spider has to do is wait for its prey to arrive. 

Some animals exhibit mimicry as predator adaptations. The orchid mantis assumes the shape of an orchid in order to attract pollinators like butterflies, bees, etc. As soon as the pollinators are in close vicinity, the orchid mantis preys on these pollinators. 

Prey adaptations: 

Similar to predators, the prey also have their own methods and abilities to protect themselves. Many animals run away from their predators. Prairie dogs run to their underground burrows when a predator is approaching. 

Most of the animal species live in groups to protect themselves from predators. For example, cows, buffaloes and antelopes stay in herds. Many small fishes, like anchovies, swim in groups known as schools. When animals live in groups, it is easier to spot a predator as all eyes, ears and noses of the individuals in the group are watching, listening and smelling for predators. 

Other prey adaptations may include: 

1. Camouflage 

2. Defensive chemicals 

3. Warning colorations. 

Camouflage: 

Some animals hide from their predators by blending in with their environment. Blending in with the background is called camouflage. 

For example, a rabbit freezes so that its natural color helps it to blend in a background of shrubs or grasses. A lot of animals mimics twigs, leaves, stones, bark or other materials in their surroundings. 

For example, a walking stick is an insect that looks like a twig. Some walking sticks even sway a little, as though a breeze is blowing.  

Defensive chemicals: 

Some animals defend themselves with the help of chemicals. 

For example, the skunk and the bombardier beetle both spray their predators with irritating chemicals. 

Some animals like bees, ants and wasps inject powerful acid into their attackers by stinging them. The skin of some animals contains deadly toxins. 

For example, the poison arrow frog and the bird are called the hooded pitohui. Any predator that eats any of these animals will probably die. 

Warning colorations: 

The animals that have chemical defense advertise them by showing warning colorations. This is done to warn the predator so that they will look for a meal elsewhere. 

Predators will avoid any animals that have the colors and patterns which they associate with pain, illness, or previous unpleasant experiences. The most common warning colors are black, white and bright shades of orange, red and yellow. 

Summary

• An ecosystem comprises a community of different organisms along with abiotic factors.
• A population cannot grow without limits because the environment has a limited amount of food, water, living space and other resources.
• When a resource is so scarce that it limits the size of a population, it is called a limiting factor.
• A limiting factor also can affect other populations in the community indirectly.
• The largest population that any environment can support is considered as its carrying capacity.
• If a population grows larger than its carrying capacity, the limiting factors in the environment cause the individuals to die or leave.
• Three main relationships through which species and individuals affect each other areas follows:
• 1. Predatory and prey relationships
• 2. Competitive relationships
• 3. Symbiotic relationships In nature, many interactions between species consist of one organism eating the other in order to obtain energy and nutrients.
• The organism that gets eaten is called prey.
• Whereas the organism that eats the prey is called a predator.
• Predators have developed a wide variety of methods and abilities to catch their prey which are considered predator adaptations.
• These adaptations include ability to run fast, mimicry and blending.
• Similar to predators, the prey also have their own adaptations to protect themselves.
• These adaptations include running away or hiding, living in groups, defense chemicals, warning colorations, camouflage, etc.