Interactions among the organisms of the same species: Intra-specific Interactions:

As we know that the organisms of the same species living together in a particular habitat come to form a population. How do they interact with each other form second important topic of ecological studies and hold an ecological significance of flora and fauna in the sense of limiting the population size so that a perpetually constant ecological balance can be maintained in the nature. From these intra-specific interactions we can certainly drive home a lesson about containing the ever burgeoning human population sizes. Although, the members of a species interact in several ways yet, these interactions fall into two main categories broadly viz: Cooperative interactions and Competitive interactions.

Noted that both types of these interactions are more evident in animals than in plants for the obvious reason their being sessile in nature.

Cooperative Interactions

 In cooperative interactions, the members of a species work together to achieve the same end.

 The sheer advantage of these cooperative intraspecific interactions is that it contributes to the survival of the species. Some of the notable examples of these cooperative intraspecific interactions are: mating, parental care, family formation, aggregations, altruism, dominance subordination behaviour, leadership behaviour, territorial behaviour, animal societies, communication and cannibalism etc. Let’s zero in on each of them in brief to get a fair idea about these interactions:

1.   Mating: Its ecological significance to identify certain species in a particular area:  

      Pairing of male and female individuals for the purpose of reproduction is known as mating. It is also called as copulation or coition. Cooperation for mating is the most fundamental and universal inter-action among the organisms of the same species.

      For the purposes of mating, animals have evolved varied modes of copulation. Many, particularly birds and mammals, indulge in simple to elaborate courtship and precopulatory behaviour. Courtship involves singing, dancing, and presenting gifts by males to their female counterpart. Mating calls of certain fishes, frogs and insects provide effective cues for species identification. Precopulatory behaviour includes mutual tactile activity. It not only initiates but also synchronizes physiological changes so that the sexes are ready to mate at the same time. Cross fertilization in plants is also a cooperative interaction for sexual reproduction.

2.   Parental Care: It refers to an activity wherein the eggs or the young ones are being looked after either by one of the parents or by both. Care arises from responsibility or affection for others among the organisms and varies from mild attention to a profound concern. Although, it is not a universal feature as most animals do not show parental care. They thus leave their eggs or young ones hatching from them to be tended by nature. Yet, many animals do exhibit a unique behaviour of care for their eggs and young ones. This behaviour manifests in many forms and modes such as: 

 (a)       Ootheca Formation: Some animals pro-vide food and protection to the eggs and pay no further attention to the offspring. Earthworm and cockroach belong to this category. They lay food-laden eggs in protective egg-eases called as oothecae and deposit the same in a safe place.

(b)       Nest Building: Many animals prepare special nests for storing their eggs. They may store food in the nest, guard the eggs, or incubate the eggs. Say for example, the female dauber wasp stores paralyzed spiders in the nest so that the young larvae upon hatching could feed on them. The male stickleback fish guards the eggs laid by several females in a nest. The female krait (a poisonous snake) incubates the eggs. The birds incubate the eggs and also rear the young ones in the nest. This may be done by one or both the parents. In the peacock, only the mother incubates the eggs and cares for the young. In crows and vultures, both the parents take part in nest building, incubation and feeding the young ones.

      Parental care: Care of the Young: It is interesting to note that the care of the young is not only a phenomenon common to animals but, it also occurs in the plants as well. Among animals, it is probably more glaringly exhibited among honey bees than in others. The worker honeybees look after and feed the larvae with great care. The mother scorpion carries the offspring on the back for about a week. The Surinam toads keeps in skin pockets not only the eggs but also the emerging tadpoles that complete metamorphosis there and leave as small, tailless adults. The mother crocodile looks after the eggs as well as the young ones when hatched. The young of some birds, such as pigeon, sparrow, dove, crow and bulbul, are naked and help-less at the time of hatching. They are thus fed and looked after in the nest itself by the parents for a long time. All mammals look after their young ones with great care and affection. This period of care has a great importance for the offsprings as they are taught during this time what the race has learnt through the ages. The female kangaroo protects and nourishes the very helpless young in her abdominal pouch called rnarsupium. The female rabbit, rat, cat and dog keep their naked, blind and helpless offspring in a burrow or under bushes or other objects, and may shift them to a safer place if threatened with danger. Parental care is prolonged in primates and is of course, maximum in humans.

      Insofar as plants are concerned, they nourish the young (embryos) and release them with various devices that protect them and help them to reach suitable sites so as to establish their permanent growth there.

      Noted that the sheer advantage of parental care among organisms is that it greatly increases the chances of survival of the progeny and continuation of the race.

3.   Aggregations: Aggregation refers to the habitual occurrence of the individuals of a species in large groups for various purposes. Such aggregations among animals may be temporary, while others may be more or less permanent. Say for example, the frogs exhibit a gregarious mode only for a temporary period for the purposes of breeding. Similarly, many solitary birds become gregarious during migration. Snakes are mainly solitary but hibernate in groups for warmth. Mosquitoes swarm for 'mating. On the other hand, there are organisms which show permanent aggregations such as flying fish live in shoals. Birds, such as parrots, ducks and geese, always occur in flocks. Mammals, such as deer, antelopes, zebras, elephants, and lions live in herds. Monkeys and apes live in troops. Bats roost together in caves. A herd of African elephants usually consists of females and their young ones. The adult female is usually the leader of the herd. Sometimes, even males form their own temporary aggregations for example; males of mountain gorilla, olive baboon and macaque form multi-male herds.

      Although, there many advantages that accrue to animals from such aggregations, yet the most significant is protection against predators and environmental hazards. It has been validly confirmed through many field observations and laboratory experiments that the individuals in an aggregation are more likely to survive than a single individual of the same species placed in the same environment. A herd of deer is less likely to be surprised by a predator than a single deer be-cause of many noses and many pairs of eyes and ears. A pack of wolves is more likely to make a kill than a single wolf.

4.   Altruism (Altruistic Behaviour): Altruism is the behaviour whereby an individual increases the welfare of another individua1 of its species at the expense of its own welfare. The individual which shows altruistic behavior is called altruistic individual or altruist. In altruism, the altruist suffers whereas the other individual is favoured (benefited). Many live examples of altruism are exhibited by the animals in nature and the most important of them are exhibited by the following animals:

 (a)       Spotted Deer: When a herd of spotted deer is attacked by a predator, such as tiger or panther, the stag' having the best antlers is surrounded by other members of the herd, to save its life. As such, one or more surrounding defenders may likely be killed by the predators.

(b)       Bees: A worker bee defends the hive by stinging the intruder even though it will rip out its inside while leaving the victim as its sting is left behind on the body of the victim. This way, it sacrifices itself life for the sake of defending its hive. The sheer advantage that altruism fetches for the organisms is that it saves the best individual or the colony from death through sacrifice of life by one or more individuals.

5.   Dominance-Subordination Behaviour: Dominance-subordination behaviour is a kind of hierarchical social order seen in a flock or herd in which there is ranking of individuals. Often the females are subordinate to males and the Youngs are subordinate to adults. High, ranking or dominant individuals casually displace the low-ranking or subordinate ones from areas of shelter and sources of food and water, whereas low-ranking individuals withdraw or submit themselves on the approach of high-ranking ones. In these social systems, social dominance is established by a series of threats including aggressive postures or actual fights. Each individual in a social group knows its rank, and all live peace-fully. If a conflict arises, the higher-ranking individual gives a formal threat display, and the lower-ranking one at once assumes a submissive or appeasement posture to avoid injury. Thus, there is no serious bloodshed, and confrontations are averted by ritualized submission. If a new individual joins the group or a member is injured, threats and fights ensue to readjust the status of the members in the social group. A member that remains absent from the group for some time is downgraded. Dominance once established is more or less permanent. However, a member of a lower rank may get a higher rank by defeating the senior ranks.

      In a social group, the highest rank always has a first chance at the available food, mate and resting site, and the lower ranks must wait for their turn. Among animals, such dominance hierarchies have been found in fishes, lizards, mice, rabbits, wild dogs, wolfs, goats, horses, Lions, tigers, monkeys and apes. Dominance hierarchies occur in such gregarious animals in which groups are small and stable so that the members may know one another individually. Its importance lies in the fact that it maintains an order and discipline in social groups which are likely to be disturbed by aggressive members.

6.   Leadership Behaviour: Leadership behaviour is a tendency on the part of the members of a group to follow a certain member called the leader. The leader keeps the other members of the group together when they are on the move. The leader determines the feeding and resting rhythms of the members in the herd. Facing the intruder or fleeing from the site is also ordered by the leader. The leadership behaviour is beneficial for the group as well as the individuals, especially in times of emergency. The relationship between the leader and the followers is different from that between the dominant member and the subordinates. The leader does not enjoy special social privileges and there is mutual dependence of the leader and the followers. This Leadership behaviour is common in mammals, but it does exist in birds, lizards, fishes and arthropods. Say for example in the red deer, the herd is led by a female. Such a herd is said to be matriarchal in nature. In elephants, the herd is also led by a female. A kangaroo herd is patriarchal in nature as it is generally led by an old male.

7.   Territorial Behaviour and Home Range: This particularly involves marking off a particular area by an individual or a group of breeding individuals either for the purposes of breeding or defending the same against any trespass typically by members of the same species, except the mates. The area so marked off is called as territory.

      These territories may be set up on a seasonal or a permanent basis. Size of the territory depends upon the food requirements of the breeding pair and their offspring. Territories are found, prior to breeding, usually by males. Boundary of the territory is marked with urine, faeces or through odorous secretions. Animals usually set up a single territory for feeding and breeding. However, the green heron (a small new world heron) establishes separate feeding and breeding territories. Similarly, the penguins use the territories for breeding only and fly out of the territories for feeding. A flock of wagtails that are winter migrants to N. India, sets up a small territory for feeding. Some individuals keep a watch and raise an alarm on seeing an approaching predator. The entire flock, so alerted eventually frightens away the enemy. Noted that the term territory may be distinguished from another analogus terms called as “Home range.” While, a territory is a small area marked off by an animal for breeding and raising a family purposes generally, by a breeding pair, home range is a wide area similarly marked off, but by a flock or herd of an animal species for the purposes of food and shelter. On the other hand, a territory is generally a selected specific region, but the home range is more or less a natural region.

8.   Animal Societies:  Certain insects, namely, termites, bees, ants and wasps, form well organized and highly integrated societies. In such a society, a large number of individuals of the same species live together in some sort of a nest which may be called as hive or comb in honey bees; termitarium or termite hill in termites and formicarium in ants. The individuals in all such insect societies are morphologically specialized into distinct types so called as castes (polymorphism) for performing different activities or jobs (division of labour). Each individual contributes to the welfare of the entire colony. There is so much specialization and interdependence of individuals in insect societies that they cannot survive outside the colony. Although, the different insect societies have evolved separately and differ in their composition and activities, they have much in common. In all cases, there are three. main castes : queen, males (drones in bees and kings in other social insects) and workers. The first two are reproductive individuals, The workers perform all other duties such as preparation of nest, collection and storing of food, rearing of young ones and protection of the colony from predators.

       The honeybee colony consists of 3 castes of individuals namely, queen, drones and workers. An average-sized colony has some 10,000-16,000 individuals. Of these, only one is queen, 500-1000 are drones, and the rest are all workers.

       In Termites, besides having the 3 castes of individuals as found in honeybees, termites do have soldiers to fight the intruders as well as for fighting a chemical warfare.

      Similarly, in an Ant society besides having soldiers, they also have sexual castes and workers. Ants cultivate fungus gardens and rear ant cows (aphids) for feeding. The aphids excrete a sweet fluid through a pair of honey dew tubes located at their back. The ants eat the honeydew.

9.   Communication: As the term is itself self explanatory, communication means transmission or exchange of information among the members of a species. This communication among animals takes place by means of different kinds of signals and       each animal possess an ability to not only send and receive signals, but also to interpret them meaningfully. As such these signals may be chemical, tactile, visual, auditory or electrical in nature. Let’s discuss the nature of these signals in brief for better understanding:

Chemical Signals: Animals use two types of chemicals for communication; pheromones and allochemicals.

Pheromones:  Chemicals released by an animal into the environment to evoke a certain behavior in other members of the species are called pheromones. The latter are detected by smell or taste. Say for example, foraging ants leave behind so called a trail substance which is a chemical pheromone along their path so that the other workers of the colony may find their way to the food and back home after gathering food. The female of silk moth secretes a sex attractant, called bombykol, which attracts male moths from several kilometers downwind. A female dog in “heat” releases a sex attractant that brings male dogs to her from a considerable (1 kilometre) distance. Queen bee secretes an antiqueen substance which checks the workers from building royal cells for new queens. Musk and other odourous substances produced by mammals (Musk deer) which secretes muskeon are used to mark territories, to identify the members of a herd and as sex attractants during breeding seasons.

Allochemicals:  The chemicals that are released by one species and affect another species are termed allochemicals. Allo means- different. These are of two types called as Allomones and kairomones.

So far as allomones are concerned, they give a sort of adaptive advantage to an              organism which produces them by acting either as repellents or attractants. Repellents provide defence against an attack. For example, the strong offensive odour emitted from two anal glands by skunk , a North American mammal when attacked keeps its predatoir at bay. Similarly, attractants attract the prey or pollinators say for example, some insectivorous plants, such as sundew (Drosera) which secretes a sticky substance to attract the insects. Many flowers secrete honey or scent to attract the insect pollinators.

The Kairomones on other hand, give adaptive advantage to an organism which receives them. Some predators find their prey by chemicals given off by the latter, e.g., Scoliodon can smell food from a long distance. Mouse can smell the odour of a cat and hide or run away.

Tactile Signals: These signals are generally used as a mode of communication when the sender of a signal is in close contact with the receiver of the same such that a variety of messages can be communicated between them by varying the frequency, pressure, and duration of contact. Tactile communication is common in courtship and mating behaviour. For example, mutual preening in birds and grooming in primates are modes of this kind of communication.

Visual Signals:  Specific structures indicate sex of the individual, e.g., mane in lion, white rump of antelope, brilliant plumage in peafowl and pheasant. Firefly emits light to attract a mate. Some animals feign death as a protection from enemy. Honeybees perform dance movements to indicate the direction and distance of the food source. A dog expresses a threat by baring its teeth and raising the fur on the back.

 Auditory Signals: This is a mode of communication by means of sound. Many animals make mating calls say for example, the male frog makes a croaking sound during the breeding season. Male crickets produce chirping sound by rubbing their forewings. Male cicada produces' a characteristic loud song with its special vibrating plates. Birds and mammals, besides mating calls, also produce sounds (chirps, grunts, snorts, roars, squeaks) to express distress, hunger, threat, mating desire and anger. Crows give a mobbing (assembly) call on seeing a predator (cat or owl). Hearing it, the crows gather and shriek at the enemy to confuse it. Male red deer produces roaring sound to win the female from the other deer.

10.       Cannibalism:   Cannibalism is an intraspecific interaction in which the larger members   eat up the smaller ones of their own species. An individual that eats is known as a      cannibal, and the one that is being eaten is called a prey. Cannibalism is common in      insects such as cockroaches, ants and termites. It is also noticed in frogs, cobras and        scorpions. Female spider eats up the male after mating. Ecologically, cannibalism has its             own share of advantage in the sense that it enables a cannibal to obtain proteins similar to         those of its own kind from the prey. Some animals limit their population by cannibalism and thus maintain a natural balance in the nature.

Competitive intraspecific Interactions (Competition)

 Since every individual in this nature needs food, space, protection from enemies and many other similar requirements of life. It thus always comes in contact with other organisms for the said purpose and competes with it. It is not easy to get all these requirements fulfilled as the earth is already crowded with life. There is competition among the organisms for their needs, and it may be quite intense. No habitat is peaceful. The animals occupying it are engaged in killing others so that they themselves may live. Sparrows fighting with one another for shelter and wall lizards chasing each other to catch an insect are common sights in our houses. Yet amid all this death and destruction, there always exists sort of a balance, ecological equilibrium, which permits the maximum individuals to live and leave their progeny. This natural balance is achieved by competition which in nature may manifest itself in two forms called as intraspecific and interspecific. Of the two, the intraspecific competition is always very fierce and severe because, all the members of a species have the same requirements of food and shelter, and they are nearly equal in their structural, functional and behavioural adaptations. This is the reason that the individuals of solitary animals often live spaced apart so that each has a better chance to satisfy its needs. Many birds and mammals establish territories for the same purpose. Intraspecific competition is maximum when the resources are limited. At other times, the animals arc well spread out and can satisfy their needs. If overcrowding occurs, the excess individuals fail to get their requirements and are eliminated.

Competition in Plants: Competition occurs in plants also. Seedlings growing under the parent tree seldom survive because of competition with the parent. Seedlings growing close together compete for space, light, water and minerals. Those growing faster than others succeed in getting their requirements and survive others perish. Seed dispersal is a mechanism for reducing competition in plants by spacing out the seedlings. Roots of some desert plants produce certain chemicals which check the germination of seeds within a certain distance to conserve scarce water and minerals.

Ecological significance of flora and fauna can thus be discerned from this competitive interaction among the organisms either of intraspecific or interspecific nature, as this competition regulates the population size to establish an ecological balance between the available resources and the population of a species.