Interspecific Interactions , Competition , Coevolution & Symbiosis

The interactions among members of the different species are called interspecific competition. Members of other species can affect all char cteristics of a population. Interspecific interactions are herbivory, predation, competition, coevolution and symbiosis. Animals often do not interact with other animals in only one way. The nature of interspecific interactions changes with the mat ity of animal and change of seasons.


Animals that feed on plants by cropping portions of the plant, but not killin the plant are herbivores. The animals which readily kill and eat other organisms are called predators. Interactions between plants and herbivores, and redator and prey are complex. Many characteristics of the environment affect them.

Yellow rumped (Myrtle)

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or Yellow rumped (Myrtle)


The competition between different species is called interspecific competition. The members of different species compete for resources. One species is forced to move or become extinct. Sometimes, two species share the resource and coexist with each other.

Most studies have shown that competing species can coexist. Some species utilize resources in slightly different ways. It can develop coexistence among these species. The interspecific competition is less severe than the effects of  intraspecific competition. Robert MacArthur studied five species of warblers (birds). They live in spruce trees. They all used the same caterpillar prey. Warblers partitioned their spruce tree habitats. He formed preferred regions for foraging. The foi nging regions were overlapped. But the competition was limited. Therefore, five speies coexisted with each other.


The coordinated evolution of ecologically related species in such a way that each species exerts a strong selective influence on the other is called coevolution. Cevoluticn may occur when species are competing for the same resource. Its examples are.

(a)    Predator-prey coevolution: Natural selection favors the development of

protective characteristic in the prey species. Similarly, selection favors characteristics in predators These predator are better adapted to catch and immobile prey. Predator-prey relationships coevolve with each other When the predator becomes more efficient, the prey also becomes more active.

(b)    Coevolution of flowering plants and pollinators: Coevolution also occurs between some flowering plants and their animal pollinators. Flowers developed different color and odors to attract pollinators. Insect-pollinated flowers are usually yellow or blue. The insects see these wavelengths of light very wall. The insects can stand on petals.

Hummingbirds also pollinate the flower. They select the tubular and red flowers. Hummingbirds have a poor sense of smell. But they see red very well. The long beak of hummingbirds is an adaptation. It allows them to reach far into tubular flowers. They have hovering ability. So they have no need for a perch.


The continuing and intimate associations between two different species are called symbiosis. Such interspecific interactions influence the species. These species involved in different ways. Sometime, one member of the association benefits and the other is harmed. In other cases, life without the partner is impossible for both. There are following types of symbiosis:



1. Parasitism: The association in which one organism lives in or on a second organism (host) is called parasitism. The host survives till the parasite complete its life cycles. The relationships between a parasite and its host are often complex. Some parasites have multiple hosts.

(a)    Definitive or final host. The host in which sexual stages of the parasite live is called definitive host. A fertile female lives in a definitive host. It produces and releases thousands of eggs in its lifetime.

(b)   Intermediate host: Each egg gives rise to an immature stage. This stage parasitizes the second host. This second host is called an intermediate host. Asexual term:Auction occurs in this host. Some life cycles have mote than one intermediate host. They develop more than one immature stage. The final immature stage reaches the definitive host.

  1. Commensalisms: A symbiotic relationship in which one member benefits and the second is neither helped nor harmed is called ommensalisms. It is difficult to differentiate parasitism and cornmensalism n natural situations The host may or may not be harmed. But it depends on such factors like nutritional state of host. Thus, symbiotic relationships may be ommunalistic in some situation. But it is parasitic in others.
  2. utualism: The symbiotic relationship that benefits both members is ailed mutualism. There are many examples of mutualism in the animal ingdom.


Interspecific interactions have developed many other characteristics in animals. So e of these are:

  1. amouflage: The hiding of an animal or its developmental stage from another animal by animal’s color patterns is called camouflage. There are two pes of camouflage.

( ) Cryptic coloration: In this case, an animal takes on color patterns of its environment Now it cannot be seen by other animals.

( ) Countershacling: It is also a kind of camouflage. It is common in frog and toad eggs. Their eggs are darkly pigmented on top. But they are lightly pigmented on the bottom. When a bird or other predator views the eggs from above, the dark of the top side hides it. But when fish view the eggs from below, the light undersurface blends with the bright water.

  1. Aposematic coloration: Some dangerous or distasteful predators develop different colors. They advertise their condition by this conspicuous coloration. The skunk have sharp white stripe. Similarly, poisonous snakes have bright colors. These color patterns are examples of warning or a aposematic coloration.
  2. Mimicry: In this case, a species resembles one or more than one, other Species. It gains protection by this resemblance.

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