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BYF2513- Unit I Session 1: Major components of an ecosystem Session 1 Major components of an ecosystem Contents Introduction, p1 1.1 The Ecosystem, p4 1.2 Major components and structure of an Ecosystem, p4 1.3 Interactions and relationships among the Ecosystem, p6 Summary, p...

BYF2513- Unit I Session 1: Major components of an ecosystem Session 1 Major components of an ecosystem Contents Introduction, p1 1.1 The Ecosystem, p4 1.2 Major components and structure of an Ecosystem, p4 1.3 Interactions and relationships among the Ecosystem, p6 Summary, p10 Learning outcomes, p11 Review Questions, p11 Introduction The term Ecology was evolved from Greek word “Oicok” meaning is “household" coupled with the word “logia” means “study of". The “study of house” has a broad meaning for the term “Ecology”. In general, your house consist of “you” and your family members, your pets , other furniture, physical things and space, energy (light, electrical, timber), house arrangement etc. You and your family members have a particular role in the house. In addition, you always make different interactions with other family members in different ways. You and your family members have their own goods, equipment, physical belongings and separate places for their personal use. Your house could be recognized as a specifically organized system. Simply speaking the term “ecosystem” is s also similar to your house. It consists of different living and non-living components, different roles and interactions at between each other. The term “Ecology” can simply be described as the scientific study on you and your surroundings. Ecology is a sub-unit of biology, the study of life. The word "ecology” was introduced by the German scientist, Ernst Haeckel in 1866. Ancient philosophers of Greece, including Hippocrates and Aristotle, recorded the natural history of plants and animals. Modern ecology developed as a more organized science after Charles Darwin's evolutionary theory in 1859. Ecology is multi-disciplinary and a collection of knowledge from different subject areas. It is closely related to physiology, evolutionary 1 Copyright © 2019, The Open University of Sri Lanka BYF2513- Unit I Session 1: Major components of an ecosystem biology, genetics, climatology, soil science etc. There are many practical applications of ecology in conservation biology, wetland management, natural resource management, city planning (urban ecology), community health, economics, basic and applied sciences and human social interaction (human ecology). Ecology may also be divided according to habitat as terrestrial ecology as well as aquatic ecology. In addition, ecology has four angles of approach as descriptive, population, productive and comparative ecology. The subject ecology is closely related to environmental science, but has its own features that distinguish it from environmental science. An understanding of how animals and plants affect ecological functions is an important focus area in ecological studies. But environmental science refers to everything that exists around us. It is the medium in which we live; we gather all the essential materials including food, air and water; all of which are integral part of our environment. The word "environment" is most commonly used to describe “natural" environment and means the sum of all living and non-living things that are present around an organism, or group of organisms. Environment often changes after some time and therefore many organisms have the ability to adapt to these changes. But ecology is a broader perspective which is defined as the air, water, minerals, organisms, and all other external factors surrounding and affecting a given organism at any time. Ecology is the scientific study of the distribution and abundance of life and the interactions between organisms and their natural environment. The environment of an organism includes physical properties, which can be described as the sum of local non-living (abiotic) factors such as insolation (sunlight), climate, and geology, and biotic ecosystem, which includes other organisms (plants, animals, and decomposers) that share its habitat. Cell→tissues→ individual species → population→communities-→ ecosystem Activity 1 Log into reliable web sites and collect different definitions on “Ecosystems”. Read carefully the collected concepts on “Ecology” and make common key words for the term ecology. Let us understand the different terms and concepts related to ecology as follows. 2 Copyright © 2019, The Open University of Sri Lanka BYF2513- Unit I Session 1: Major components of an ecosystem Term species A group of closely related organisms those are very similar to each other. They are usually capable of interbreeding and producing fertile young. The species is the fundamental category of classification. Term Genus A genus is a group of species that are closely related through common decent. A genus represents one of several hierarchical categories called taxa (singular taxon genera (plural of genus) include only a small group of species which evolved from a relatively recent common ancestor. The genus is the fundamental category of ecology. Population A group of individuals of a particular species occupying a particular geographical region in a given time. Eg. Elephus maximas (Elephants) at Gal Oya basin during 1967 -1969 period was about 300. Number of organisms in the population is increased by birth or germination and immigration. It is decreased by death and emigration. Community An ecological community is a group of actually or potentially interacting species living in the same location. Communities are bound together by a shared environment and a network of influence each species has on the other. Such groups of several species are living together with mutual tolerance and benefits in that area. In a community different species share some common characteristic features due to uniform environmental conditions. The size and the characteristic features of communities are varied. Eg. A forest, a desert, a pond, mangrove community process different characteristic features. A community has its own specific features. i. e. Different plant and animal species, growth form and structures (trees, liana, shrubs etc), different arrangement of plants, that is horizontal arrangement (zonation) and vertical arrangement (stratification) or growth forms and some important prominent species. Such prominent species in a community is known as “Dominant species”. As an example in a low land tropical rain forest such as Sinharaja forest the Dipterocarpus (Hora) species are dominant. In addition, any community can change with time due to variation/fluctuation of environmental factors and eventually attain to a stable condition known as climax stage. Communities which change their composition with time are known as successional communities. 3 Copyright © 2019, The Open University of Sri Lanka BYF2513- Unit I Session 1: Major components of an ecosystem Activity 2 Define the basic terms “population” and the “ community”. Tabulate the main differences between terms “population” with “community”. 1.1 The Ecosystem The living and non-living things in an environment, and all their interactions can be simply defined as an Ecosystem. The ecosystem can be recognized as a basic fundamental unit in ecology. There are different types of ecosystems in nature eg. a pond, a forest, an estuary, grassland. Usually the boundaries of one ecosystem are overlapping and no clear margins are recognizable in most ecosystems. We can study the subject ecology at the level of the individual, the population, the community, and the ecosystem levels. Figure 1.1: Diagrammatic representation of main components in an ecosystem. 1.2 Major components and structure of an Ecosystem There are two major dimensions in an ecosystem. They are the structure and its function of the ecosystem. As you know, the structure mainly consists of living as well as non-living components (Figure 1.1). Those two components always make interactions and maintain a balance. The main functions of an ecosystem are flow of energy and cycling of raw material within the system. The non-living (abiotic) components The non- living part of an ecosystem mainly consist of space, energy and raw material. The space is again sub-divided as physical and 4 Copyright © 2019, The Open University of Sri Lanka BYF2513- Unit I Session 1: Major components of an ecosystem biological space. Biological space is a sub-unit of a physical space and it is the space living organisms occupy. Based on the sources, there are several types of energy in the world. e.g. Solar, chemical, gravitational, heat, wind etc. Solar energy plays a major role in an ecosystem. Almost all functions in an ecosystem are governed by solar energy. eg. Material flow as well as functions of every biotic component. The energy enters the ecosystem from the sun as radiation and is trapped in green plant and converted to chemical energy. This chemical energy is utilized in metabolic processes and finally released as heat energy. Raw materials are the building blocks of an ecosystem. The materials can be divided in to three pools according to their origin i.e. Atmosphere (gases), hydrosphere (water), lithosphere (soil). The atmosphere provides organisms found within ecosystems with carbon dioxide (CO2) for photosynthesis and oxygen for respiration. Most living tissues contain a very high percentage of water, up to 90%. A large portion of the earth (2/3) is covered by water in different forms. e.g. Sea water, fresh water, ,ice in polar regions , ground water. The Lithosphere is the solid component which consists of soils and rocks. Soils are mainly formed by weathering of rocks and it is much more complex than simple sediments. Soils contain a mixture of weathered rock fragments, highly altered soil mineral particles, organic matter, and living organisms. The living (biotic) components Ecosystems are composed of a variety of living organisms. In ecology, living organisms are classified as producers (autotroph), consumers and decomposers (heterotroph). Producers or autotrophs (auto = "self"; "troph" - feeding), are organisms that can synthesise the organic compounds that they use as sources of energy and nutrients. Most producers are green plants or algae that can manufacture their food through the process of photosynthesis. Organisms that require energy fixed in the form of chemical bonds of organic molecules for survival are called heterotrophs (hetero = "other"; "troph" - feeding). Heterotrophs always depend directly on producers or organic materials derived by producers. Heterotrophs who obtain their energy from living organisms are called consumers. Consumers can be of two basic types: Consumer and decomposers. Consumers that consume plants are known as herbivores. Carnivores are consumers who eat herbivores or other carnivores. Some organisms that are eating the producers (plants) as well as consumers (animals) are known as Omnivores. Decomposers or 5 Copyright © 2019, The Open University of Sri Lanka BYF2513- Unit I Session 1: Major components of an ecosystem detritivores are heterotrophs that obtain their energy either from dead organisms or from organic compounds dispersed in the environment. Most of them are microorganisms which includes fungi and bacteria. The following graphical model describes the major ecosystem components and their interrelationships (Figure 1.2). Figure 1.2: Interactions amongst major components of an ecosystem. Activity 3 1. What do you mean by an Ecosystem? 2. Identify the main components of an ecosystem 1.3 Interactions and relationships among the ecosystems The ecosystem is a highly complex system. It is dynamic and changes with time or in respect to place (temporal and spacial changes). Two types of changes can be recognized in an ecosystem called uni- directional (moving or operating in a single direction) or cyclic (repeat the changes). Under natural conditions organisms live together, have influence on each other in direct or indirect manner. Sometime these relationships may be beneficial to each other or may harm one organism or more organisms in interaction. Mainly five (05) types of interactions are prominent within biological components. e.g. Predation, parasitism, symbiosis and pathogenesis. The most important relationship between living organisms and the environment, dependent ultimately on the amount of solar energy received. 6 Copyright © 2019, The Open University of Sri Lanka BYF2513- Unit I Session 1: Major components of an ecosystem Predation It is easy to think of predation in the context of common sense. Predator eats prey. However, ecologically, predation is defined as any interaction between two organisms that results in a flow of energy between them. This definition is applicable to both plants and animals. There are four commonly recognized types of predation: (1) carnivory, (2) herbivory, (3) parasitism, (4) Mutualism (5) Pathogenesis Each type of predation can by categorize based on whether or not it results in the death of the prey. Carnivory is lethal to the prey while herbivory and parasitism may or may not be lethal to the prey. Mutualism is not lethal to either predator or prey but, rather, benefits both organisms. Predation can restrict the distribution of prey species or regulate their populations. That is very important maintain the ecosystem 1. Carnivory Carnivorous predators kill and eat their prey. The common perception of carnivory involves a large animal, such as a lion or a tiger, hunting smaller animals like rabbits or deer. However, carnivorous predation is widespread in the animal world and carnivores can come in a variety of sizes – from sea otters hunting sea stars to blue whales consuming zooplankton, each carnivore is adapted to its mode of feeding. 2. Herbivory Herbivorous predation involves the consumption of autotrophs, such as plants or photosynthetic algae. Unlike carnivory, not every herbivorous interaction leads to the death of the plant. Occasionally, herbivory can benefit the plant as well. Fruit seeds are dispersed over wide areas as the herbivore moves. Tough seed coatings are removed in the digestive tract of the herbivore, and its dung fertilizes the soil, providing an ideal environment for seed germination. 3. Parasitism Parasitism is a form of predation where the host supplies essential nutrients for the sustained survival and reproduction of the parasite. In many successful parasitic interactions, the host suffers a loss of energy, 7 Copyright © 2019, The Open University of Sri Lanka BYF2513- Unit I Session 1: Major components of an ecosystem falls sick or loses access to nutrients. However, unlike carnivory, the host is not always killed. In most cases, the parasite is much smaller than the host.. e.g. A tree infected with Cuscuta 4. Mutualism Mutualism involves the interaction between two organisms where the host provides the nutrition and space for the growth and reproduction of another species. However, the host is not harmed and the interaction is mutually beneficial. Symbiosis is a good example for mutualism. That is an association of two organisms with beneficial effects for both organisms. eg. Lichen or a mycorrhiza, N-fixing bacteria and Legume plants. 5. Pathogenesis One organism causing diseases in another organism is known as pathogenesis. e.g. Bacteria, fungi, Virus. The host is affected by the pathogen and most often express symptoms. Activity 4 1. List the main interactions that could be identified in an ecosystem. 2. List the main differences between symbiosis and pathogenesis. Ecological competition Ecological competition is the struggle between two organisms for the same resources within an ecosystem. Resources are components of the ecosystem that are required for survival and reproduction such as food, water, shelter, light, territory, and substrate. Members of the same species have similar requirements hence are more competitive. There are two major competition types. i.e., inter species and Intra species. Competition among members of different species is known as inter species competition, while competition among members of the same species is called intra species competition. Because members of the same species occupy the same ecological niche, their needs are nearly identical. Hence, intra species competition tends to be more intense than inter species competition. Ecological competition helps maintain community structure and species diversity within ecosystems. The concept of competitive exclusion is also being used to improve agricultural practices. Inter species competition occurs when members 8 Copyright © 2019, The Open University of Sri Lanka BYF2513- Unit I Session 1: Major components of an ecosystem of more than one species compete for the same resource. Woodpeckers and Squirrels often compete for nesting rights in the same holes and spaces in trees, while the lions and cheetahs of the African savanna compete for the same antelope and gazelle prey. Intra species competition helps nature keep the population under control. When food is limited, the environment can only feed so many individuals of the same species. This result in the survival of the fittest, only those capable of winning against their counterparts survive. Similar regulation occurs when individuals compete over shelter for raising young. This often occurs with young male lions; Animals that lose are driven from the group and from the area. Plants also compete for space, nutrients and resources such as water and sunlight. This competition can shape how the ecosystem looks. Taller trees shield a forest's understory -- the ground beneath the forest's tree- top canopy -- from sunlight, making it hard for anything to grow but the most shade-tolerant plants. The life cycles of some plants are also impacted because many shorter plants flower and bear seeds before the leaves of the taller trees are fully developed, which makes it possible for shorter plants to receive sunlight. Desert plants have developed shallow, far-reaching roots systems to successfully compete for valuable water resources, which is an example of how competition can affect the evolution of a species. Competition according to evolutionary theory: this competition within and between species for resources is important in natural selection. Scientists believe that competitive relationships may at least be partially responsible for the evolutionary process. In natural selection, the individuals of a species are best adapted to the environment around them to survive and reproduce and pass on the genetics that make them well adapted. Take the Giraffe for example, whose evolution of its long neck makes it possible to eat food with little to no competition. As an herbivore, it completes with other grazing herbivores such as zebras and antelope for food. Giraffes with longer necks are able to reach the leaves of high tree branches, giving them access to more food and a better chance of passing their genetics on to their offspring. Read more: http://www.biologyreference.com/CeCo/Competition.html#ixzz5VP81a99m https://sciencing.com/competitive-relationships-ecosystems-8451289.html 9 Copyright © 2019, The Open University of Sri Lanka BYF2513- Unit I Session 1: Major components of an ecosystem Ecological niche and the habitat Naturally, man as a social animal always has a competitive mentality with his peers and tries to demarcate his position and the teritory. Other organisms also show such competitive mentality specially to fulfil their basic needs. Further, all organisms prefer to demarcate a most suitable physical space to live without much competition. In addition each and every organism has identical roles and status in the ecosystem. Concepts such as ecological habitat and niche have been explained by ecologists based on demarcated space and respective role of an individual in an ecosystem. A habitat and a niche have quite different meanings. The habitat is the place where a particular animal lives and can be found in nature. The niche is the role it plays that places him to live comfortably in the ecosystem. The niche provides us a complete description of how the organism fits into its physical and biological environment. That is the ecological role and space that an organism fills (habitat) in an ecosystem. i. e. Your address in the working place is similar to a habitat and address including your position in the working place can be described as a niche. Specific conditions are necessary for each species to tolerate the physical environment, obtain energy and nutrients, and avoid predators. It is obvious that toleration limits are different from one species to another. Limits of tolerance is the upper and lower limits to the range of particular environmental factors (e.g. light, temperature, availability of water) within which an organism can survive. Some species shows waste tolerant limits in an ecosystem and they can tolerate any environmental changes than less tolerance species. There are two categories of niches as fundamental and realized niches. The fundamental niche of a species includes the total range of environmental conditions that are suitable for existence without any ecological disturbances. The realized niche describes the part of the fundamental niche which is actually occupied by the species. 10 Copyright © 2019, The Open University of Sri Lanka BYF2513- Unit I Session 1: Major components of an ecosystem Activity 5 Differentiate the terms Niche and the Habitat. Summary “Ecology” is a multi-disciplinary subject and is described as the scientific study on you and your surroundings. A population is a group of organisms of the same species which live together in the same space and time. An ecosystem can be defined as an environment where both the living and non-living part of nature interact and are in dynamic equilibrium. Ecosystems are made up of abiotic and biotic components and these basic components are important to nearly all types of ecosystems. Mainly five (05) types of interactions are prominent within biological components. e.g. Predation, parasitism, symbiosis, mutualism and pathogenesis. Ecological competition is the struggle between two organisms for the same resources within an environment. There are two major competition types. i.e, Intra species and Inter species. Learning outcomes After studying this session, you should be able to: Describe an ecosystem Describe the main components in an ecosystem Explain the different concepts related to ecology Identify basic interaction among component in an ecosystem Describe the term ecological competition. 11 Copyright © 2019, The Open University of Sri Lanka BYF2513- Unit I Session 1: Major components of an ecosystem Review Questions 1. What do you mean by an Ecological system? 2. List the main components in an ecosystem. 3. Describe the interactions found among components listed in question 12 Copyright © 2019, The Open University of Sri Lanka