Biological interactions

Ecology

1. Department of Bioresources University of Kashmir By Shariqa Aisha Biological Interactions Picture representing the title of the Topic Biological Interactions

2. Learning Objectives To understand the concept of ecological interactions. To know about the different types of competition . To learn about the various types of interactions. To acquire the knowledge about parasitism and predation.

3. An ecological community consists of all the populations of all the different species that live together in a particular area . The populations can be very much affected by the interactions between the organisms in the ecosystem i.e. Interspecific interactions. 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 (+/-), mutualism, (+/+), commensalism (+/0), and parasitism (+/-). Introduction

4. Competition Competition is a relationship in which different organisms or populations in the ecosystem attempt to use the same limited resources at the same time. The limiting resource may be water, prey, light, water etc., which is responsible for the organism’s growth and survival in the ecosystem . Competition can occur both within (intra specific) and between (inter specific) species. Competition among the individuals can also be characterized as resource competition or interference competition. Resource competition : It is characterized by the organism’s completion directly for the limiting nutrient in the ecosystem, there by obtaining as much each individual can . An example is the competition of fly maggots in a mouse carcass, where few individuals obtain enough nutrients for their reproduction and survival.

5. Interference Competition: in this case, the individuals harm each other directly by a physical force. In this case either the individuals interact with foraging, survival, and reproduction of others or directly prevent their physical organization in a part of their habitat. Interference competition generally results in the exclusion of one of the two competitors. The competitive exclusion principle,sometimes referred to as Gause's law, stated that two species competing for the same limited resource cannot coexist at constant population values. When one species has even the slightest advantage over another, the one with the advantage will dominate in the long term. Competitive exclusion principle Competitive Exclusion Principle 1 : A smaller (yellow) species of bird forages across the whole tree. 2: A larger (red) species competes for resources. 3: Red dominates in the middle for the more abundant resources. Yellow adapts to a new niche restricted to the top and bottom of the tree, avoiding competition.

6. Interspecific competition Interspecific competition is competition for resources (such as food, space, water, light, etc.) between members of different species, and in general one species will out-compete another one. This can be demonstrated by growing two different species of the protozoan Paramecium in flasks in a lab . They both grow well in lab flasks when grown separately, but when grown together P. aurelia out-competes P. caudatum for food, so the population of P. caudatum falls due to interspecific competition. Case first shows no competition as they are grown separately, while as in case second P. aurelia out-competes P. caudatum due to interspecific competition.

7. Intraspecific competition Intraspecific competition is an interaction in population ecology, whereby members of the same species compete for limited resources. This leads to a reduction in fitness for both individuals, but the most fit individual survives and is able to reproduce. Two basic types have been identified for intraspecific competition : Interference (adapted) intraspecific competition: This occurs in species that establish hierarchies through aggressive behavior where one or more individuals within the population hold a dominant status over the others . Exploitation (contest) intraspecific competition: This occurs between individuals of the same population exploiting the same resources and reducing or depleting its availability to others.

8. Mutualism Mutualism is an interspecific interaction between two organisms in the ecosystem with benefit to both the associating members in the interaction. During this interaction, populations of each interacting species grow survive and reproduce at a higher rate in the presence of the other interacting species . Mutualism is an interaction between two or more species, where species derive a mutual benefit, for example an increased carrying capacity . One or both species involved in the interaction may be obligate, meaning they cannot survive in the short or long term without the other species. Pollination is a good example to explain mutualism, where the plant gets benefit from the dispersal of pollen the pollinator obtaining a meal of nectar from the flower.

9. The spider crab and the algae . Spider crabs live in shallow areas of the ocean floor, and greenish-brown algae lives on the crabs' backs, making the crabs blend in with their environment, and unnoticeable to predators. The algae gets a good place to live, and the crab gets camouflage. The bacteria and the human . A certain kind of bacteria lives in the intestines of humans and many other animals. The human cannot digest all of the food that it eats. The bacteria eat the food that the human cannot digest and partially digest it, allowing the human to finish the job. The bacteria benefit by getting food, and the human benefits by being able to digest the food it eats. Mutualism: The algae gets a good place to live and the spider crab gets camouflage to live. Bacteria benefits by getting food and human benefits by being able to digest food it eats

10. Commensalism Commensalism is a type of symbiotic relationship in which one species benefits, while the other species is neither harmed nor helped. The species that gains the benefit is called the commensal. The other species is termed the host species . A commensal species benefits from another species by obtaining shelter, food, or support from the host species, which (for the most part) neither benefits nor is harmed. Commensalism ranges from brief interactions between species to life-long symbiosis. Example: Cattle egrets eat the insects stirred up by cattle when they are grazing. The cattle are unaffected, while the birds gain food.

11. Amensalism is an interaction where an organism inflicts harm to another organism without any costs or benefits received by itself. There are basically two types of amensalism: competition and antibiosis. In competition , a larger or more powerful organism excludes another organism from its source of shelter or food. In antibiosis , one organism secretes a chemical that kills the other organism, while the one that secreted the chemical is unharmed. Amensalism Example: Algal blooms can lead to the death of many species of fishes and other animals, however the algae do not benefit from the deaths of the individuals. Amensalism

12. Parasitism Parasitism benefits one species at the expense of another. Parasitism may be regarded as a special form of symbiosis in which the parasite usually is much smaller than the prey and remains closely associated with it . Parasitism is harmful to the prey organism and beneficial to the parasite. In many cases, the parasite kills its host, and thus the ecological effects of parasitism can be similar to those of predation. It is in the parasite’s best interest not to be too detrimental to the host. If the host dies, then the parasite dies.

13. Ex ternal parasites Parasites that feed on the exterior surface of an organism are external parasites, or ectoparasites. Many instances of external parasitism are known in both plants and animals. Parasitoids are insects that lay eggs on living hosts. This behavior is common among wasps, whose larvae feed on the body of the unfortunate host, often killing it. Examples: Hair and body lice (head lice )

14. Internal parasites Parasites that live within the body of their hosts, termed endoparasites, occur in many different phyla of animals and protists. Internal parasitism is generally marked by much more extreme specialization than external parasitism, as shown by the many protist and invertebrate parasites that infect humans. Example: Acanthamoebiasis This tiny ameba can affect the human eye, the skin, and the brain. It exists all over the world in water and soil. Individuals can become infected if they clean contact lenses with tap water.

15. Amoebiasis This is caused by the parasite Entamoeba histolytica. It affects the intestines. It is more likely in tropical regions and in areas with high population density and poor sanitation. It is transmitted through the fecal-oral route.

16. Predation The term predation is defined as the consumption of one living organism (prey) by another ( the predator) excluding scavengers and decomposers. I t is act of capturing, killing and eating. T he organism which does the act of predation is called a predator. The second organism which is killed and eaten is called prey. Predation is generally linked to carnivorous animals and predator is generally larger in size compared to the prey.

17. Examples: Spiders spinning webs to trap and kill insects

18. Rattlesnakes using venom in their bite to kill small animals

19. NAME DESCRIPTION EFFECT Competition Organisms of two species use the same limited resource and have a negative impact on each other. - /- Mutualism A long-term, close association between two species in which both partners benefit. + /+ Commensalism A long-term, close association between two species in which one benefits and the other is unaffected. + / 0 Amensalism An organism inflicts harm to another organism without any costs or benefits received by itself. - / Parasitism A long-term, close association between two species in which one benefits and the other is harmed. + / - Predation A member of one species, predator, eats all or part of the body of a member of another species, prey. + / -

20. Multiple choice Questions Q.1 When both partners are affected negatively the nature of interaction is: a) Competition b) commensalism predation amensalism Q.2 The ascaris, entamoeba and plasmodium are considers as an examples of : Endoparasite E ctoparasite Digestion parasite synthetic parasite Q.3 The organism who kills, attacks and feeds others are called: Prey parasite assimilators predators

21. Q.4 The competitive exclusion principle was first described by Gause for species of: Mice Birds Protozoa Grass Q.5 Predation and Parasitism are which type of interactions: + /+ + / - - / - - / + Q.6 The interaction shown by rattle snack and rat is: Predation Parasitism Mutualism Cooperation

22. Q.7 A relationship between two organisms in which one organism benefits and the other is unharmed: Competition Parasitism Commensalism Mutualism Q.8 Amensalism is an interaction between two species where: One species is harmed and the other is benefited. One species is harmed and the other is unaffected. One species is benefitted and the other is unaffected. Both species are harmed. Q.9 Cattle egrets and Cattle shows which type of interaction: Amensalism Protocooperation Parasitism Commensalism

23. http:// www.sciencedirect.com https:// www.britannica.com http:// www.ncbi.nllm.nih.gov http:// www.reseacrhgate.net https:// www.khanacademy.org Life sciences_ Pranav Kumar Ecology_ Theories and applications by Peter Stiling Links and Books of the Title lecture