[Biology Class Notes] on Population Interaction Pdf for Exam

The study of different Organisms, their scattered presence over different regions, and their Interaction or Communication with each other and the surrounding Environment comes under the Umbrella of Ecology.  The theory of Population Interaction is extremely crucial to be understood fundamentally prior to the understanding of the concepts and relationships between Predators and Prey, Camouflage, Competition, Mimicry, Hunting Strategies, etc.

 

Definition of Population Interaction

According to the Population Interaction definition, the Interaction among Populations is the Interaction between different species of Organisms in the Ecosystem. It takes into account the effects that Organisms belonging to a community have on everybody else and one another. 

 

There are two kinds of Factors, the abiotic one or the Physical Factor and the biological one or biotic Factor in the Environment. Some Physical Factors like nutrients of the soil, water, carbon dioxide, atmospheric pressure, wind, etc. are important for and needed by a living Organism to live. The different kinds of Populations and their Interactions can be affected a lot by these abiotic Factors, which are a part of the Ecosystem. Mentioned below are the major modes of Interaction between different Populations or the types of Population Interaction:

 

Competition

It is an Interaction between two or more than two species of Organisms when they compete. The competition is for limited resources, which all the competitors want control of, at the same time. These resources can be area, food, water, or any other prey. As these things are important for sustaining, these resources are mainly the ones for which competition happens.

 

Competition is further categorized into the following types:

• In interference competition, Organisms interact directly by fighting for scarce resources which may be availability of mates or food etc. One example is the large aphids who defend  their feeding sites on cottonwood leaves by ejecting smaller aphids from better sites. Male-male competition in red deer during rut is another example. One key feature is that individuals often engage in aggressive behaviours with respect to the other competitor for foraging, survival and/or reproduction. They also show territorial behaviour in order to beat any competition for limiting resources. To compete aggressively, they have evolved various structures such as antlers in deer, bright colourful feathers in peacocks, etc., which lends competitive advantage over the other members of the species. In an Ecosystem, interference competition is a strategy adopted in animal species mainly by the larger and stronger Organisms within a habitat.

• In exploitation competition, or scramble competition, both  Organisms indirectly use the common limiting resource or shared food item. Instead of fighting to win resources, they indirectly deplete the total amount available for other Organisms. These Organisms might never interact directly, but nevertheless are said to be competing as they effectively respond to changes in resource levels. Common examples of this phenomenon include plants who grow in close vicinity to each other and then compete with their neighboring plants for sunlight, soil nutrients, etc. .

• The apparent competition occurs when two species that are otherwise unrelated end up competing with each other for survival due to a shared predator. For example, suppose there are two species (species A and species B), which are preyed upon by food-limited predator species C. Scientists observe an increase in the abundance of species A and a decline in the abundance of species B.

 

Predation 

In a predation relationship, there is a full dependency of one kind of species over the other species for their survival and food. The one that gets preyed for food is called the prey. The species which feeds on the other kind of species is termed as a predator species.

 

Several instances of the food chains, food webs, etc. are based on this concept, where a predator keeps on relying on other species for food during its entire life cycle. In some cases, the predator can also become prey to some other species. All the living Organisms have their own defense and attack strategies, which they use to become safe from the stronger species or to hunt down the weaker species.

 

This relationship is witnessed not just within the animal kingdom but also plant kingdom. Predator and prey can also be applied to animal and plant relationships. For example, a goat feeding on grass or a panda eating bamboo.

 

Camouflage 

It is an effective defense survival strategy used by various Organisms to develop structural adaptation and Physical characteristics similar to their surroundings and blend with it in order to be safe and not get found by the predators actively looking for them. Many animals like chameleons, lizards, frogs, leopards, etc. use this technique for their own advantages for hiding away from predators.

 

Symbiosis 

In the Greek language, symbiosis means to live together. There are situations in which many species of Organisms depend on each other for survival. They depend on each other for food in most cases. One Organism lives with another exhibiting a mutual stereotypical behaviour in this case. There are different types of Population Interactions of Symbiosis kind.

 

Types of Symbiosis Interaction

1) Mutualism 

It is a biological relationship or Interaction between two or more species of Organisms. In this type of Population Interaction, each species is profited in some or the other way from the other species. This is the most common type of ecological Interaction. It explains that mutual dependency is needed and is necessary for the social well-being of different species. It is prominent in most Populations of Organisms around the globe.

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2) Commensalism

It is a unique kind of relationship where two or more species of Organisms depend on each other for food or survival and get benefitted, but without harming each other or anyone.

                                             

3) Parasitism

Parasitism involves one Organism feeding off another Organism. It is a case of one-sided symbiosis. The Organism that feeds off another species is called a parasite, and the prey species is called the host. The parasites multiply, causing harm to the hosts.