Unit-2-Interspecific and intraspecific interactions.ppt
- 1. ELECTIVE COURSE - II ELECTIVE COURSE - II (B) – (B) – ECOLOGY AND ECOLOGY AND EVOLUTION (UNIT-II) EVOLUTION (UNIT-II) Prepared by Dr. A. Sudha, Assistant Professor, Department of Biotechnology, Dr. Umayal Ramanathan College for Women, Karaikudi.
- 2. Unit - II Population interaction: Intra specific interactions – Aggregation, Social organization, divisions of labour and Social behavior, Territorialism, migration. Inter specific interaction – Neutralism, commensalism, synergism, mutualism, symbiosis, commensalism, Antagonism, parasitism, competition and predation.
- 3. POPULATION INTERACTIONS Population interactions or biological interaction are the effects that a pair of organisms in a community have on one another. These effects may be short-term, like pollination and predation, or long-term; both often strongly influence the evolution of the species involved. An organisms interaction with its environment are fundamental to the survival of that organism and the functioning of the ecosystem as a whole. Populations do not exist alone in nature. The way organisms interact is important for the survival of a species. There are two types of interaction: intraspecific interactions and interspecific interactions.
- 4. Intraspecific interactions are those that take place among organisms of the same species while interspecific interactions are those which happen among individuals of different species. A long-term interaction is called a symbiosis. Symbioses range from mutualism, beneficial to both partners, to competition, harmful to both partners. Interactions can be indirect, through intermediaries such as shared resources or common enemies.
- 6. An ecological community consists of all the populations of all the different species that live together in a particular area. Interactions between different species in a community are called interspecific interactions— inter- means "between." Different types of interspecific interactions have different effects on the two participants, which may be positive (+), negative (-), or neutral (0). The main types of interspecific interactions include competition (-/-), predation (+/-), mutualis m, (+/+), commensalism (+/0), and parasitism (+/-). These are distinguished by the degree of benefit or harm they cause to each partner. Interspecific interactions
- 7. Interspecies interactions can be broken into three main categories: competition, predation, and symbiosis.
- 9. 1. Competition In interspecific competition, members of two different species use the same limited resource and therefore compete for it. Competition negatively affects both participants (-/- interaction), as either species would have higher survival and reproduction if the other was absent. Species compete when they have overlapping niches, that is, overlapping ecological roles and requirements for survival and reproduction. Competition can be minimized if two species with overlapping niches evolve by natural selection to utilize less similar resources, resulting in resource partitioning.
- 10. 2. Predation It is a kind of short term interaction. In predation, one organism, the predator, kills and eats another organism, its prey. This interaction is beneficial for the predator, but harmful for the prey (+/- interaction). Ex: Leopard killing deer. Predators are adapted and often highly specialized for hunting, with acute senses such as vision, hearing, or smell. Many predatory animals, both vertebrate and invertebrate, have sharp claws or jaws to grip, kill, and cut up their prey. Predation has been a major driver of evolution.
- 11. Predation has a powerful selective effect on prey, causing them to develop antipredator adaptations such as warning coloration, alarm calls and other signals, camouflage and defensive spines and chemicals. Predators and prey regulate each other's population dynamics. Also, many species in predator-prey relationships have evolved adaptations—beneficial features arising by natural selection—related to their interaction. On the prey end, these include mechanical, chemical, and behavioral defenses. Mimicry is another adaptation evolved in some species to shock the predators.
- 12. Predation is a method to transfer the energy to higher trophic levels. In fact biological control methods of pests are based on the predator- prey relationship. Predation may involve two animal species, but it can also involve an animal or insect consuming part of a plant, a special case of predation known as herbivory. Plants have also evolved various defensive mechanisms to avoid predation. They are as follows: i. Thorns in Acacia and Cactus. ii. Toxic chemicals are produced by some plants that harm the plants. Calotropis, a weed produces a highly poisonous cardiac glycosides and are avoided by the grazing animals.
- 13. 3. Symbiosis It is a long-term biological interaction. Symbiosis is a general term for interspecific interactions in which two species live together in a long-term, intimate association. The organisms, each termed a symbiont, may be of the same or of different species. Symbiosis is a broader concept and can include close, lasting relationships with a variety of positive or negative effects on the participants. The six possible types of symbiosis are mutualism, commensalism, parasitism, neutralism, amensalism, and competition. Symbiosis can be obligatory, which means that one or more of the symbionts entirely depend on each other for survival, or facultative (optional), when they can generally live independently.
- 14. When one organism lives on the surface of another, such as head lice on humans, it is called ectosymbiosis; when one partner lives inside the tissues of another, such as Symbiodinium within coral, it is termed endosymbiosis.
- 15. i) Mutualism: Mutualism describes the ecological interaction between two or more species where each species has a net benefit. Similar interactions within a species are known as co-operation. Mutualistic relationships may be either obligate for both species, obligate for one but facultative for the other, or facultative for both. An example of mutualism is the relationship between the clownfish that dwell among the tentacles of sea anemones. The territorial fish protects the anemone from anemone-eating fish, and in turn the stinging tentacles of the anemone protect the clownfish from its predators.
- 16. Mutualism is a common type of ecological interaction. In a mutualism, two species have a long-term interaction that is beneficial to both of them (+/+ interaction). Other examples include most vascular plants engaged in mutualistic interactions with mycorrhizae, some types of fungi form mutualistic associations with plant roots, flowering plants being pollinated by animals, vascular plants being dispersed by animals etc.. Mutualism plays a key part in ecology. For example, mutualistic interactions are vital for terrestrial ecosystem function as more than 48% of land plants rely on mycorrhizal relationships with fungi to provide them with inorganic compounds and trace elements.
- 17. Mutualism is thought to have driven the evolution of much of the biological diversity such as flower forms (important for pollination mutualisms) and co- evolution between groups of species. However, mutualism has historically received less attention than other interactions such as predation and parasitism. Humans are involved in mutualisms with other species: their gut flora is essential for efficient digestion.
- 18. Evolution of Mutualism Mutualisms are not static, and can be lost by evolution. Sachs and Simms (2006) suggest that this can occur via 4 main pathways: ◦ One mutualist shifts to parasitism, and no longer benefits its partner, such as headlice. ◦ One partner abandons the mutualism and lives autonomously. ◦ One partner may go extinct. ◦ A partner may be switched to another species.
- 19. POLLINATION PROCESS One of the most commonly observed mutualism is the pollination of flowering plants by an insect or humming bird. The pollinator benefits from the interaction by receiving nectar. The plant gets its pollen transferred from one plant to another.
- 20. Mutualism-other examples Mutualism Species 1 Species 2 Ant & acacia Ant – gains secure home, food supply Acacia – gains protection from predation Coral & Algae Coral – gains carbohydrate from photosynthesis Algae – protection and mineral nutrients Mycorrhizae & plants Mycorrhiza – gains photosynthetic product Plant – improved mineral and water absorption Ruminant herbivore & bacteria Ruminant - gets its food digested Bacteria – gains protection, warmth, moisture & food Lichen Fungus – photosynthetic products Algae – gains water, minerals and structural support Rhizobium and legumes Rhizobium – gains photosynthetic product Plant – gains nitrate for protein synthesis
- 21. Proto-cooperation: When both the species can survive without each other it is called facultative mutualism or proto- cooperation. Best example of this is the association between hermit crab and sea anemone. Sea anemone provides camouflage to hermit crab and in turn is transported to new feeding places. It is less extreme type of interaction in which two species interact favorably with each other, though both of them are able to survive separately.
- 22. ii)Commensalism In a commensalism, two species have a long-term interaction that is beneficial to one and has no positive or negative effect on the other (+/0 interaction). It occurs when one organism takes benefits by interacting with another organism by which the host organism is not affected. For instance, many of the bacteria that inhabit our bodies seem to have a commensal relationship with us. They benefit by getting shelter and nutrients and have no obvious helpful or harmful effect on us. It's worth noting that many apparent commensalisms actually turn out to be slightly mutualistic or slightly parasitic when we look at them more closely.
- 23. It is derived from the English word commensal, used of human social interaction. A good example is a remora living with a manatee. Remoras feed on the manatee's faeces. The manatee is not affected by this interaction, as the remora does not deplete the manatee's resources. Remora-Sucker fish Manatees are large, fully aquatic, mostly herbivorous marine mammals sometimes known as sea cows.
- 24. Examples for commensalism are – sucker fish is found attached to sharks with their suckers. Sucker fish gets protection from predators whereas it has no effect on sharks. Epiphytes like mosses, orchids, ferns, money plants grow on the trunk of other trees. They do not harm the tree but just grow to get better sunlight .
- 25. iii)Parasitism In a parasitism, two species have a close, lasting interaction that is beneficial to one, the parasite, and harmful to the other, the host (+/- interaction). Some parasites cause familiar human diseases. For instance, if there is a tapeworm living in the intestine, you are the host and the tapeworm is the parasite. In the parasitic association, the species which provides nourishment and support is called the host and the one which gets support and nourishment is called the parasite. Parasitism takes many forms, from endoparasites that live within the host's body to ectoparasites. Parasitism is an extremely successful mode of life; about 40% of all animal species are parasites.
- 26. Examples of endoparasites are tapeworm, roundworm, threadworm, Plasmodium, etc. and ectoparasites are ticks, mites, lice, leech, etc. Cuscuta is a plant parasite and has lost its ability to photosynthesize since it derives nourishment from the host plant. Parasites are host specific in such a way that both the host and the parasite have coevolved. The parasites have evolved special adaptations to live successfully in a host. They are as follows: Loss of sense organs Presence of adhesive organs or suckers High rate of reproduction Loss of digestive system.
- 27. Complicated life history with a primary and one or more intermediate hosts. Eg: The malarial parasite (Plasmodium) requires a mosquito which is a vector to spread to other hosts. Brood parasitism in bird is an interesting example of parasitism. This is seen in the cuckoo or koel bird. The cuckoo lays its eggs in the nest of the crow. These eggs resemble the eggs of crow. The crow incubates the eggs and takes care of them.
- 28. Diagram of the six possible types of symbiotic relationship, from mutual benefit to mutual harm.
- 29. iv)Amensalism Amensalism is an asymmetric interaction where one species is harmed or killed by the other, and one is unaffected by the other. Amensalism describes the adverse effect that one organism has on another organism. This is a unidirectional process based on the release of a specific compound by one organism that has a negative effect on another. A classic example of amensalism is the microbial production of antibiotics that can inhibit or kill other, susceptible microorganisms. A clear case of amensalism is where sheep or cattle trample grass. Whilst the presence of the grass causes negligible detrimental effects to the animal's hoof but the grass suffers from being crushed. Amensalisms can be quite complex interactions.
- 30. There are two types of amensalism, competition and antagonism (or antibiosis). Competition is where a larger or stronger organism deprives a smaller or weaker one from a resource. An example of competition is a sapling growing under the shadow of a mature tree. The mature tree can rob the sapling of necessary sunlight and, if the mature tree is very large, it can take up rainwater and deplete soil nutrients. Throughout the process, the mature tree is unaffected by the sapling. Indeed, if the sapling dies, the mature tree gains nutrients from the decaying sapling. Competition is often for a resource such as food, water, or territory in limited supply, or for access to females for reproduction.
- 31. Competition among members of the same species is known as intraspecific competition, while competition between individuals of different species is known as interspecific competition. According to the competitive exclusion principle, species less suited to compete for resources should either adapt or die out. According to evolutionary theory, this competition within and between species for resources plays a critical role in natural selection. Antagonism occurs when one organism is damaged or killed by another through a chemical secretion. An example of antagonism is black walnut, secreting juglone, a substance which destroys many herbaceous plants within its root zone.
- 32. v) Neutralism Neutralism (a term introduced by Eugene Odum) describes the relationship between two species that interact but do not affect each other. When the presence of one species appears to have no effect on the second species (i.e., no interaction), it is a state of neutralism. Examples of true neutralism are virtually impossible to prove; the term is in practice used to describe situations where interactions are negligible or insignificant.
- 33. Cost, Benefits & Consequences INTERACTION Effect on Population Density Predation Parasitism Commensalism Mutualism Competition Predator increases, prey decreases Parasite increases, host decreases Commensal increases, host density is unaffected Both species in mutualism increase Both species in competition decrease
- 35. Territoriality is the behavior by which an animal lays claim to and defends an area against others of its species, and occasionally members of other species as well. The territory defended could be hundreds of square miles in size, or only slightly larger than the animal itself. It may be occupied by a single animal, a pair, family, or entire herd or swarm of animals. Some animals hold and defend a territory year-round, and use the territory as a source of food and shelter. Other animals establish a territory only at certain times of the year, when it is needed for attracting a mate, breeding, and/or raising a family. Territorialism
- 36. Types Of Territories Some animals will establish a territory solely for the purpose of having a place to rest. Such a territory is known as a roost, and may be established in a different area every night. Roosts are often occupied and defended by large groups of animals, for the protection offered in numbers. Individual personal spaces within the roost may be fought over as well. Roosting spots nearer the interior of a group of animals are often the safest.
- 37. Several species of birds and a few mammals are known to establish specialized territories during the breeding season, which are used only to attract mates through breeding displays. This type of territory is known as a lek, and the associated behavior is called lekking. Leks are generally of little use for feeding or for bringing up young, and the animals will abandon its lek once it attracts a mate or mates, or if it becomes too weak to defend it.
- 38. Among birds, territories have been classified as six types. Type A: An 'all-purpose territory' in which all activities occur, e.g. courtship, mating, nesting and foraging Type B: A mating and nesting territory. Type C: A nesting territory which includes the nest plus a small area around it. Type D: A pairing and mating territory-lekking type. Type E: Roosting territory. Type F: Winter territory which typically includes foraging areas and roost sites.
- 39. Defending A Territory Some animals will defend their territory by fighting with those who try to invade it. Fighting, however, is not often the best option, since it uses up a large amount of energy, and can result in injury or even death. Most animals rely on various threats, either through vocalizations, smells, or visual displays. The songs of birds, the drumming of woodpeckers, and the loud calls of monkeys are all warnings that carry for long distances, advertising to potential intruders that someone else’s territory is being approached.
- 40. Many animals rely on smells to mark their territories, spraying urine, leaving droppings or rubbing scent glands around the territories’ borders. Approaching animals will be warned off the territory without ever encountering the territory’s defender. When two individuals of a territorial species meet, they will generally threaten each other with visual displays. These displays often will often exaggerate an animal’s size by the fluffing up of feathers or fur, or will show off the animals weapons.
- 41. Actual fighting usually only happens in overcrowded conditions, when resources are scarce. Serious injury can result, and old or sick animals may die, leading to a more balanced population size. Under most natural conditions, territoriality is an effective way of maintaining a healthy population.
- 42. Advantages of Territoriality: I. Associated with Reproduction: 1. It helps in securing a nesting site. 2. Aids in the formation of pairs. 3. Reduces the possibility of disturbances from the competitors. 4. Permits females to select the males. II. Associated with Habitat and Food: 1. Permits increased inbreeding within a population as a means of better adaptation to the local habitat. 2. Secures adequate food for the pair and young ones. 3. Makes the animals familiar with the location of food and water.
- 43. Divides resources among the dominant and subordinate individuals with consequent reduction in fighting and stress. III. Associated with Predation and Parasitism: 1. Provides knowledge of location of shelter. 2. Dispersion, thus resulting in less possibility of being detected by the predators. 3. Provides sufficient space to the members of a species, thereby decreasing the chances of transmission of diseases and parasites. IV. To avoid overcrowding: Prevents overcrowding and over exposition of resources through natural selection.
- 44. An aggregation is any form of gathering of organisms and the process of coming together. In some forms, groups of unrelated species might form, in which interaction between members of the aggregation might be minimal. for example herds of grazing zebra and antelopes might combine both the better to observe the approach of predators, and to improve the odds of escape in the event of attack by predators. Sometimes there might be some interaction, such as mixed flocks of birds that observe each other's foraging behavior in searching for food. Aggregation
- 45. A general theory explaining why individuals should prefer to aggregate was first proposed by the Briton W.D. Hamilton, one of the most important evolutionary biologists of the 20th century. Hamilton hypothesized that animals might come together to form a so-called “selfish herd,” where an individual’s chances of being eaten are substantially reduced, especially if that individual remains in the interior of the group. Eg: school of fish is formed, it cannot be eaten by predators.
- 46. A school of fish
- 47. Living in groups also protects group members through a dilution effect. In the simplest example, when a group-living individual encounters a predator that will eat just one prey item, his likelihood of being eaten is reduced from p, the probability when alone, to p/N, the probability when the individual is a member of a group of size N. For example, if a tadpole joins a group with just one other individual, it reduces its chance of being eaten by one-half. Furthermore, if that tadpole joins with 99 others, its chance of being eaten drops by 99 percent.
- 48. Alarm calls and other complex signaling behaviour within aggregations can also reduce the likelihood of predation. Calls may coordinate a group’s escape from danger, confuse a predator, and prompt individuals to seek protected sites or shelter. Alarm calls may also convey information about the type of predator and lead to the appropriate evasive behaviour. Alarm calls might even provide information regarding an individual predator’s identity and habits.
- 49. Structured aggregations tend to be longer-term and of a specific life-cycle function and context. Typically, they will be of a single species. Often they will be of a single age and possibly of a single sex. Eg: mature males of elephants, seals, lions and other animals would begin to compete with the dominant males of other animals. Another example is larvae of certain insects such as Lepidoptera and Hemiptera form a flock and feed together and may migrate in "processions" until they are mature after which some kinds get dispersed. Most species of migrating birds and mammals flock on a large scale, partly for protection and partly for greater reliability of navigation.
- 50. The primary functions of aggregation appear to be feeding and defense. The important range of functions are security against predators, success in food location, wide range of mate choice, with concomitant increase of outbreeding opportunities, location with other members of the same species (sometimes adherence to separate communities can almost amount to parapatric residence when say, different communities of rats or chimpanzees have violent mutual antipathy). There also are various forms of educational function, such as in some species where the young must learn the correct mate recognition skills, and in highly intelligent species such as crows and elephants, must learn the necessary social skills and the necessary traditional foraging techniques in their region.
- 51. Aggregation also takes place, since the animals are mutually attracted to each other for some resources. Examples may include aggregations of sea lions or shorebirds for breeding purposes or a place to take shelter from cold, aridity, or otherwise rainy weather, as in aggregations of opilionids-“harvestmen”. They survive because a big clump of them, won’t dry out and die as easily as lone individuals. These spiders will often stick many of their legs straight up from the cluster to capture condensation from the night and dawn air, helping to save them from fatal desiccation in the hot part of the day.
- 52. Migration, in ecology, is the large-scale movement of members of a species to a different environment. Migration is a natural behavior and component of the life cycle of many species of mobile organisms, not limited to animals, though animal migration is the best known type. Migration is often cyclical, frequently occurring on a seasonal basis, and in some cases on a daily basis. Species migrate to take advantage of more favorable conditions with respect to food availability, safety from predation, mating opportunity, or other environmental factors. Migration
- 53. Migration is two way mass movement of the entire population. It involves a periodic departure and return of the individuals of a population and occurs only in mobile organisms during un- favourable periods. It is shown by many birds, fishes and certain mammals. Through this type of movement the chances of utilization of resources in the habitats is very high. However, during migration of population, mortality of numerous individuals may occur due to various ecological hazards, such as temperature fluctuation, scarcity of food, predation etc. Migration has certain benefits for populations as it enables wider dispersion of populations. It also avoids competition for food, shelter, etc.
- 54. Migratory organisms use environmental cues like photoperiod and weather conditions as well as internal cues like hormone levels to determine when it is time to begin a migration. Migratory species use senses such as magnetoreception or olfaction to orient themselves or navigate their route, respectively. For eg: The pigeon can return to its home using its ability to sense the Earth's magnetic field and other cues to orient itself. The factors that determine migration methods are variable due to the inconsistency of major seasonal changes and events. When an organism migrates from one location to another, its energy use and rate of migration are directly related to each other and to the safety of the organism.
- 55. If an ecological barrier presents itself along a migrant’s route, the migrant can either choose to use its energy to cross the barrier directly or use it to move around the barrier. If an organism is migrating to a place where there is high competition for food or habitat, its rate of migration should be higher. This indirectly helps determine an organism’s fitness by increasing the likelihood of its survival and reproductive success. Elk migrate vertically – up the mountains in spring as snow recedes and down the mountains in fall as winter advances. Millions of zebra, wildebeest and antelope in East Africa migrate each year in what is known as The Great Migration or the Annual Wildebeest Migration.
- 56. Types of migration include: Animal migration, the physical movement by animals from one area to another. ◦ Bird migration, the regular seasonal journey undertaken by many species of birds. Reverse migration, a phenomenon in bird migration. ◦ Fish migration, the regular journey of fish. ◦ Insect migration, the seasonal movement of insects Lepidoptera migration, the movement of butterflies and moths. Diel vertical migration, a daily migration undertaken by some ocean organisms.
- 57. Effects of migration Migratory species can transport diseases long- distance from their original habitat. A species migrating to a new community can affect the outcome of local competitive interactions. If the migratory species is abundant in the new community, it can become a main prey for a resident predator. It can increase the predatory species’ population size.
- 58. Ecological Significance of Migration Migration, has considerable ecological significance. It enables fast-moving animals to exploit fluctuating resources and to settle in areas where life would not be acceptable for animals incapable of rapid travel. On the other hand, peaks of food production would be unexploited without the periodic presence of migratory populations. The sequence of migratory movement is closely integrated in the annual cycle of ecosystems characterized by productivity fluctuations.
- 59. Migrant birds avoid equatorial forests where productivity is constant throughout the year, and food surpluses do not occur. They do gather together, on the other hand, in savannas where productivity varies with the seasons. In the Arctic, vegetal and animal production is very high during the summer; ducks and waders nest in great numbers, exploiting these resources. As winter comes, food becomes scarce, and water birds migrate to the tropics, where the rainy season has caused food production to increase to optimal levels.
- 60. Division of labor refers to separation of activities and the specialized allocation to different individuals. The division of labor creates specialized behavioral groups within an animal society which are sometimes called castes. A colony has caste differences: queens and reproductive males take the roles of the sole reproducers, while soldiers and workers work together to create a living situation favorable for the brood. Batra, observed the cooperative behavior of the bees, males and females alike, as they took responsibility for at least one duty (i.e., burrowing, cell construction, oviposition) within the colony. The cooperativeness was essential as the activity of one labor division greatly influenced the activity of another. Division of labor
- 61. Division of labour (DOL)/ Functional specialization within organisms is not universal but it is a derived feature. It is common in most multi-cellular, colonial and social organisms. DOL evolved at every level of individuality from some organelles of single-celled eukaryotes, through different cell types, tissues and organs within multi-cellular organisms, to polymorphic zooids and castes in colonial and social animals. DOL occurs in at least 10 colonial and social animal phyla. Without DOL, the ecology of organisms must remain simple or their physiology must constantly adjust to any changes in their environments.
- 62. The expression of DOL is different across various types of organisms. Two basic types can be recognized- reproductive and ‘other’ types of DOL. Reproductive DOL occurs when some members of group do not reproduce. ‘Other’ DOL is defined as non-reproductive functional differences between members (for example, between feeding and defence). Two basic mechanisms have been previously proposed that jointly explain the origin of DOL within organisms, colonies and societies. In the first mechanism, functional variants arise over evolutionary time. In the second mechanism, DOL arises as a solution to a functional optimization problem.
- 63. An organism with extensive DOL could have feeding, defensive, reproductive and structural specialists, whereas an organism without extensive DOL may only have defensive specialists. Animal division of labor is the division of labor amongst animals. This can be demonstrated in a number of areas such as: ◦ Animal defensive behavior ◦ Animal foraging behavior ◦ Animal parental behavior ◦ Nest building ◦ Eg; In various species of social insects such as ants, wasps, termites, and bees, DOL is predominant.
- 64. Eg:1-The degree of social organization in a Hymenoptera colony is most evident in the division of labour. In honeybee colonies, the division of labour is achieved in an especially interesting manner. Tasks are assigned according to age. The first day after the bee’s emergence as an adult, female workers carry out wastes, clean the cells, and line them with a disinfectant secretion preparatory to deposition of the egg by the queen. On about the fourth day this young bee advances to brood nursing, where she provides older larvae with honey and pollen. On the sixth day she also provides young, newly hatched larvae with specific larval food from her pharyngeal glands.
- 65. At about 16 days the bee becomes active in secreting wax and using it to build the comb. Soon afterward, she makes her first orientation flight outside the hive. On about the 20th day she becomes a hunter. She remains at this job until her death. This activity sequence parallels certain physiological changes in the bee. Eg:2- In the division of labour among some ant, highly specialized types of polymorphism have been developed. The very close relationship between insects that are social parasites of the Hymenoptera and their hosts is made possible by the host’s division of labour and by a special secretion produced by the parasite.
- 66. https://www.easybiologyclass.com/ biological-interactions-positive-negative- interactions-ecosystem-ppt/ https://www.britannica.com/topic/animal- social-behaviour/Aggregation-and- individual-protection https://www.britannica.com/topic/animal- social-behaviour/The-range-of-social- behaviour-in-animals#ref1045264