Mimicry | Zoology Optional Notes for UPSC PDF Download

Mimicry meaning in biology, says that it is an evolved resemblance that exists between an organism and another unknown subject. Most of the time, the unknown subject is found to be an organism that belongs to a different species. Mimicry is something that can evolve between different species or different individuals of the same species. Mimicry is responsible for protecting different species from predators, thus making it an antipredator adaptation. One can get a clear idea of the meaning of mimicry from this paragraph.

Mimicry in Biology

• In biology, mimicry is a phenomenon marked by the superficial likeness of two or more species that are not taxonomically related. The organisms fool the living agent of natural selection by conferring an advantage—such as protection from predation—on one or both of them. Depending on the type of mimicry encountered, the agent of selection (which might be a predator, a symbiont, or a parasite's host) interacts directly with similar organisms and is misled by their similarity. Different types of convergent likeness that emerge from the operation of other natural selection factors (e.g., temperature, feeding preferences) on unrelated organisms are distinguished by this type of natural selection.
• The advantage is one-sided in the most well-studied mimetic partnerships, with one species (the mimic) benefiting from a likeness to the other (the model). Many plants and animals have been discovered to be mimetic since the discovery of mimicry in butterflies in the mid-nineteenth century. Although the creatures involved in most cases belong to the same class, order, or even family, there are countless examples of plants imitating animals and vice versa. Although the most well-known examples of mimicry involve physical similarities, research has shown fascinating cases in which the resemblance involves sound, scent, behaviour, and even biology.
• Deception by the mimic, done on a third party who mistook the mimic for the model, is a critical feature in practically every mimetic situation. This third party might be a group of possible predators on the mimic, a predacious mimic's potential prey, or even one of the mimic's own species' sexes. In some circumstances, such as parasite-host mimicry, the fooled organism is the model.
• Because of the wide range of scenarios in which mimicry occurs, a formal definition must be based on the influence of specific key communicative signals on the appropriate receiver, as well as the resulting evolutionary effect on the signal emitters. Mimicry is defined as a situation in which two virtually identical signals, emitted by two different organisms, have at least one receiver in common that reacts in the same way to both signals because it is advantageous to do so to one of them (the model signal), even if it is disadvantageous to do so to the counterfeit signal.
• When only the model and the mimic are present, the distinction between camouflage and imitation is not always evident. When the receiver is known and its reactions are understood, however, the distinction is clear: in mimicry, the signals have a special meaning for the receiver and the sender, who has evolved the signals in order to be perceived by the receiver; in camouflage, the sender attempts to avoid detection by the receiver by imitating what the receiver perceives as a neutral background. See also colouration: Camouflage for further information on camouflage.

Overview

Mimicry starts evolving when a receiver such as a predator starts perceiving the similarity between a mimic, the organism that is believed to have a resemblance (mimic meaning in biology) and a model, the organism which the mimic resembles, and as a result, the predator aims to change the behaviour of the model in a particular way that will give some selective advantage for the mimic. The resemblances that tend to evolve in mimicry are of many types, such as visual, acoustic, chemical, tactile or electric or sometimes the combinations of these sensory modalities.

Biology Mimicry - Different Types

Mimicry of organisms is most probably clear from the above paragraphs where we explained mimicry meaning. Now let’s discuss the different types of mimicry that exist in nature. We will discuss each in a brief way.

Batesian Mimicry

• In 1862, Henry W. Bates, an English naturalist, published a book that explained some unexpected and unique similarities in the appearance of two distinct family butterflies that were found in Brazilian Forest. One of these butterflies is known as Heliconiinae, they are conspicuously coloured and are unpalatable birds, and the other one is known as Pieridae; they are considered edible to predators. 
• According to Bates, the coloured species which are inedible act as a warning for the predators, who learned that they are inedible from experience. If the edible species get the same colour pattern as the inedible ones, then they can get saved from the predators. This form of mimicry is known as Batesian mimicry. It was named like this in order to honour the discoverer.

Aggressive Mimicry

• In some situations, it is seen that the predator seems to take advantage of mimicry in order to resemble its prey or a parasite its host. To describe aggressive mimicry in simple words, just say the phrase "a wolf in sheep's clothing"; it will clearly describe the meaning of aggressive mimicry. This type of mimicry doesn't involve warning mechanisms. In this case, the mimic tries to adopt some marks of its model so that it will have some advantage over the model or over a third species that might interact with the model.
• The model might get mimicked only for a single stage in the life cycle; this is similar to the case of parasitic cuckoos, where the eggs tend to resemble the host. The model might also be a prey of the mimic's victim; this is similar to the case of anglerfishes which have rod-like spines naturally which are tipped with a fleshy "bait" in order to lure the fishes who are within reach.

Mullerian Mimicry

• Bates observed some resemblance between some unrelated butterflies, including danaids (milkweed butterfly) which he was unable to explain. All of these butterflies were considered to be inedible. There was no point or any requirement for such species to adopt a warning colouration because they have ample defence which can protect them from predators.
•  In 1878, Fritz Muller, who was a known German zoologist, published an explanation for Bate's paradox; he suggested that this paradox might be an advantage for one inedible species in making a predator learn from another. Once the predator has learned that they had to avoid a particular colour pattern that they have contact with initially, then they will start avoiding every species edible or inedible having the same colour pattern. 
•  When the predator gets the initial experience, it might cause death or damage to the inedible individual who was responsible for providing the experience. This shows that there is some cost to pay for making the predator learn the inedibility of a particular species. Predators didn't inherit this knowledge; they learn about the inedibility of a species from experience only.
•  Other inedible species which are resembling the one who taught the predator inedibility don't need to sacrifice individuals to teach the same predator. Species that have the same colouring pattern as the one who taught the predator inedibility to get secured automatically. When inedible species start to resemble each other, it is known as Mullerian mimicry.

Types of Mimicry

Batesian Mimicry

The edible species' deceptively similar colour patterns would give protection from the same predators. Batesian mimicry is named after its discoverer, and it occurs when a vulnerable creature shows a striking likeness to a toxic and visible one.

Automimicry

The phenomenon of automimicry refers to how certain members of a species benefit from their likeness to other members of the same species. Although defenceless, males of many bees and wasps are protected from predators by their similarity to females with stingers. Some butterflies can protect themselves from predators by absorbing, tolerating, and retaining toxins from the plants they feed on while still juvenile (larval). Individuals or even subpopulations of these butterflies may not gain such protection as a result of feeding on nonpoisonous plants, but predators that sampled protected individuals of the same species avoid them.

Aggresive Mimicry

In some cases, it is advantageous for a predator to look like its prey, or for a parasite to look like its host. Aggressive mimicry, which is well described as "a wolf in sheep's clothing," is devoid of warning signals. In order to gain an edge over the model or a third species that interact with the model, the mimic adopts certain of its model's recognition marks.

Mullerian Mimicry

Once the predator has learned to avoid the specific colour pattern with which it came into contact for the first time, it will avoid any other patterned species, both edible and non-edible. The predator's initial learning experience frequently results in death or harm to the inedible individual who delivered the lesson; thus, the species that informs the predator of its inedibility bears some cost. Evidence suggests that certain predators have little or no hereditary recognition of noxious or inedible species; instead, each individual learns about noxious or inedible species by sampling them. Other inedible species that resemble the first, on the other hand, do not need to sacrifice individuals to teach the same predator, and the number of individuals sacrificed in learning the total predator population is dispersed throughout all species that share the same warning pattern. Müllerian mimicry refers to the tendency of inedible or toxic species to resemble one another.