Updated Environmental Studies Lecture Notes 2024 PDF

1 UNIVERSITY OF TECHNOLOGY FACULTY OF SCIENCE AND SPORT Module: Environmental Studies Lecture #2 ORGANISATION OF THE ENVIRONMENT The environment can be divided into the biological or l...

1 UNIVERSITY OF TECHNOLOGY FACULTY OF SCIENCE AND SPORT Module: Environmental Studies Lecture #2 ORGANISATION OF THE ENVIRONMENT The environment can be divided into the biological or living component which is known as biota and the physical or non-living component known as abiota. Biota includes all the organisms: plants, animals and microbes in the ecosystem. The total population of a specific kind of plant, animal or microbe is called a species. Individuals belonging to the same species have similar DNA and are able to interbreed and produce fertile offspring. The way categories of organisms fit together is referred to as the biotic structure. The non-living chemical and physical factors of the environment including soil quality and climate are referred to as abiotic factors. Biotic Structure Individual: A single member of a species. Population: A group within a given species, living in the same habitat, the individuals of which can and do freely interbreed. Breeding between different populations of the same species is less common because of differences in location, culture and nationality. Community: Several interacting populations living in a habitat. Abiotic structure Atmosphere: Gaseous envelope surrounding the Earth. Hydrosphere: Earth’s supply of water, liquid and frozen, fresh and salty. Lithosphere: The lithosphere is the soil and rock of Earth’s crust. Biotic and Abiotic Interactions Ecosystem: Grouping of plants, animals and other organisms interacting with each other and the non-living component of the environment in such a way as to perpetuate the grouping more or less indefinitely. Biome: Terrestrial regions with similar vegetation types and other forms of life occurring in different parts of the world are collectively termed biomes. These are governed by similar types of climatic conditions. Examples include: tropical rain forests, coniferous forests and grasslands. Ecotone: Ecosystems seldom have distinct boundaries and are not independent of each other. One tends to blend into the next through a transitional region called an ecotone. This region contains many of the species and characteristics of the two adjacent systems and may include unique environments that support distinctive plants and animals as well as those that are common to the adjoining ecosystem. Examples of ecotones include areas ( a ) between ocean and freshwater systems in the form of estuaries, (b) between ocean and land in the form of beaches, wetlands and rocky coastlines and (c) between terrestrial ecosystems such as between a forest and grassland or between a forest and a desert.  2 Fig 1. Example of a Terrestrial Ecotone: Source: https://www.pmfias.com/wp-content/uploads/2016/05/ecotone-grassland.jpeg  3 Fig 2. Example of an Ecotone between a Land and an Aquatic Ecosystem: Source: https://ec0l0gical.files.wordpress.com/2013/12/ecotone.jpg Biosphere: Zone of the earth where life is found. It consists of parts of the atmosphere, hydrosphere and lithosphere. THE ENERGY OF LIFE Matter is anything that has mass and takes up space. For matter to move or do work it requires energy which is the capacity or ability to do work or to transfer heat. The sun is the energy source that powers all life processes. The study of energy and its transformations is called thermodynamics. Two laws of thermodynamics are: First Law of Thermodynamics Energy cannot be created or destroyed although it can be transformed from one form to another. As a consequence of the first law of thermodynamics, living things cannot create energy but must capture the energy from the environment. Plants absorb the radiant energy of the sun and convert it into the chemical energy contained in the bonds of glucose. Animals obtain energy by consuming plants or other animals. Second Law of Thermodynamics When energy is converted from one form to another, some usable energy i.e. energy available to do work is degraded into a less usable form such as heat that disperses into the environment. As a result, the amount of usable energy available to do work in the universe decreases over time. Photosynthesis and Cell Respiration Photosynthesis is a biological process in which light energy from the sun is captured and transformed into the chemical energy found in the chemical bonds of carbohydrate molecules (glucose). This process uses carbon dioxide and water as raw materials with the release of oxygen as a by-product.  4 6CO2 +6 H2O Solar energy C6H12O6 +6O2 carbon dioxide+ water glucose + oxygen Respiration is the process by which the chemical energy stored in carbohydrates and other molecules is released within the cells by the breaking down of these molecules in the presence of oxygen to form carbon dioxide and water with the release of energy stored in units called ATP – Adenosine Triphosphate. C6H12O6 + 6O2 6CO2 + 6H2O + ATP (energy) glucose + oxygen carbon dioxide + water + energy ENERGY FLOW THROUGH ECOSYSTEMS The movement of energy in a one-way direction through an ecosystem is known as energy flow. In an ecosystem energy flow occurs in food chains where energy from food passes from one organism to the next in a sequence. A food web is a complex of interconnected food chains in an ecosystem. Organisms in a community can be divided into categories based on how they get nourishment. 1. Producers/Autotrophs – these are organisms that trap the sun’s energy to manufacture food from simple raw materials. These are found at the bottom or the beginning of the food chain. 2. Primary consumers/ herbivores – these are organisms that feed directly upon producers. 3. Secondary consumers – these are organisms that feed on primary consumers. 4. Omnivores – these are organisms that can use both plants and other animals as food sources. 5. Tertiary consumers – these are organisms that feed on secondary consumers 6. Decomposers – Decomposers feed on dead or decaying matter (detritus) by secreting digestive enzymes extracellularly. This breaks down the cell walls and the nutrients are then absorbed. e.g. fungi and bacteria 7. Detritivores – unlike decomposers these consumers ingest detritus. The matter is then broken down and the nutrients absorbed internally. e.g. snails, crabs, clams and worms. Detritus is non-living organic matter which includes animal carcasses, leaf litter and faeces Trophic Levels Trophic levels are the feeding position an organism may occupy in a food chain. A plant, for example, is at the first trophic level while the grasshopper that eats the plant is at the second trophic level. As you move up the food chain energy is degraded. This is caused by a conversion of potential energy into kinetic energy and heat energy. As stated under the Second Law of Thermodynamics as the energy changes, some of the useful energy is degraded to lower quality, less useful energy. Ecological Pyramids Ecological pyramids are graphical representations designed to show the biomass, productivity (energy flow) or population at each trophic level in a particular ecosystem in a given time. These pyramids were first described by the English biologist, Charles Elton in the 1920s. Pyramid of Energy The pyramid of energy shows the energy available or the productivity at each trophic level (see Fig 3). The values presented in the pyramid are expressed as kcal or J per m2 per year. This pyramid is always upright as there is a substantial amount of energy lost (90 %) in the form of heat through respiration at successive trophic levels. On average, only approximately 10% of the energy available at one trophic level is available to the one above it when an organism is consumed. This means that energy is at its maximum at the lowest trophic level i.e., at the level of the primary producers and is at the minimum at the highest trophic level. This also means that a large quantity of energy is required at the base to sustain an ecosystem. The loss in available energy as one moves up the food chain as indicated in the pyramid of energy is an application of the Second Law of Thermodynamics described earlier.  5 Fig 3. Pyramid of Energy (Figures in pyramid represent J per m2 per year) Source: https://qph.cf2.quoracdn.net/main-qimg-af6482a39081dd78f66f6eb888122689-lq Pyramid of Numbers (Population) The pyramid of numbers displays the number of living organisms present at each trophic level expressed as number per m2, km2 or hectare (ha). Generally, green plants are the most numerous group of organisms and form the base of the pyramid which in this case would be an upright one (Fig. 4) as the numbers of organism of successive trophic levels decrease. There are some instances, however, as in a temperate forest, where the base of the food chain is occupied by a relatively small number of very large trees. In this case, even though the amount of plant material is large enough to support the ecosystem, the number of individual plant organisms is lower that the number of herbivores. This yields a partly upright or spindle-shaped pyramid (Fig. 5). FIg. 4 Typical Upright Pyramid of Numbers Sources: Pyramid: https://cdn.kastatic.org/ka-perseus-images/aa7160f542bb2108744f41b6a2b7a7bcaadaa6c5.png Grassland Image: https://www.reference.com/content/424724/ea359fad648ff77cc53736c2a73c2053.jpg  6 Fig. 5 Partially Upright Pyramid of Numbers in Temperate Ecosystem Sources: Pyramid: https://cdn.kastatic.org/ka-perseus-images/aa7160f542bb2108744f41b6a2b7a7bcaadaa6c5.png Forest Image: https://cff2.earth.com/uploads/2020/10/20155502/forest-3795202_1280.jpg Pyramid of Biomass The pyramid of biomass illustrates the dry weight of living tissue that is present at each trophic level within a particular ecosystem. Values are represented in this pyramid as grams per m2 or kilograms per m2. In terrestrial ecosystems the pyramid of biomass is usually always upright as the amount of living material represented by its weight decreases on one moves up the food chain (Fig. 6). In some aquatic ecosystems, however, the base of the food chain is occupied by microscopic plants (phytoplankton) which are consumed primarily by microscopic animals (zooplankton). These organisms, although very numerous and enough to support the entire ecosystem weigh very little and as such the resultant pyramid will look different from that of the terrestrial pyramid of biomass. In this case the pyramid would be either inverted or partly upright (Fig. 7). Tertiary Consumers Secondary Consumers Primary Consumers/ Herbivores Producers Fig. 6 Typical Upright Pyramid of Biomass (Terrestrial Ecosystem) Adapted from: https://image.slidesharecdn.com/energytransferinecosystems-120914163642-phpapp02/95/energy- transfer-in-ecosystems-8-728.jpg?cb=1347640820  7 Tertiary LARGER FISH (12 g/ m2) Consumers Secondary SMALL FISH (8 g/ m2) Consumers ZOOPLANKTON (6 g/ m2) Primary Consumers/ Herbivores PHYTO- (4 g/ m2) Producers PLANKTON Fig 7. Example of Inverted Pyramid of Biomass (Aquatic Ecosystem) ECOLOGICAL EFFICIENCY After feeding, consumers convert the chemical energy in their food into their own biomass (stored organic matter). The energy stored in biomass is then transferred to the next trophic level as a result of consumption. Ecological efficiency describes how much stored energy an organism can receive from the food that it consumes, and hence the efficiency with which energy is transferred from one trophic level to another. Since an organism uses its food for other physical and biological processes and a significant portion is lost as low- grade heat, energy transfer between trophic levels is generally inefficient so that on average it is estimated that there is only a 10 percent transfer of energy from one trophic level to the next. This inefficiency in energy transfer is one reason given to explain why food chains are generally short in nature having only between 3 to 5 links on average (energetic hypothesis). TUTORIAL QUESTIONS 1. What is ecology? Using examples, distinguish between the biotic and abiotic structure of the environment. This is the study of organisms interacting between organisms and their non- living environment. 2. Define the following terms: individual, community and population. Community, this is a group of different organisms living in the same habitat which also are interbreeding 3. What is meant by the following: ecosystem, biosphere and ecotone. What are the relationships between them?Ecosystem is a group of living organism interacting with each other and the non living component of the environment. Ecotone, this is the study of interactions between organism and their non living environment 4. Is the energy available to do work now the same as it was when the universe was formed? Explain. 5. a) What is thermodynamics? b) State the first and second laws of thermodynamics and discuss how they apply to organisms and ecosystems. First laws of thermodynamics, which is also called conservation of energy, in this cause energy cannot be created or destroyed. Second law of thermodynamics  8 6. Explain the processes of photosynthesis and cellular respiration and discuss their importance to organisms. Provide summary equations for both processes. 7. a) What is an ecological pyramid? b) Explain what is illustrated in a pyramid of energy and a pyramid of biomass. c) Explain why the pyramid of energy has its characteristic shape. d) Define the term “ecological efficiency” 8. a) Define the term “trophic level” Trophic level is the feeding level of an organism b) List and define the various levels of consumers that may be found within an ecosystem. Producers, primary consumers, secondary consumers, Tertiary consumers 9. What are the implications of the complete removal from an ecosystem of: a) Photosynthetic plants b) Primary consumers c) Secondary consumers 10. Differentiate between an autotroph and a heterotroph. How are they important to the transfer of energy in the ecosystem? Originally Compiled By: Raymond Martin Last Revision By: Christine O’Sullivan, May 2012 Last Updated By: Christine O’Sullivan, May 2017 Last Updated By: Nikki Bramwell, August 2021 Last Updated By: Nikki Bramwell, May 2024 List of References Britannica, T. Editors of Encyclopaedia (2021, November 29). ecotone. Encyclopedia Britannica. https://www.britannica.com/science/ecotone Ecotone: Edge Effect, Edge Species and Ecological Niche (2019). https://www.pmfias.com/ecological- niche-ecotone-edge-effect/ Ecological Pyramids. (2020, August 14). Retrieved June 22, 2021, from https://bio.libretexts.org/@go/page/14228 Ecosystem (Book Chapter). Retrieved May 3, 2024 from https://ncert.nic.in/textbook/pdf/lebo114.pdf Kumar, Pranav & Mina, Usha. (2021). Fundamentals of Ecology and Environment 3e. Miller, G. T., & Spoolman, S. (2010). Environmental Science 13th Edition (Belmont: Brooks/Cole, Cengage Learning).  9 Nielsen, S. N., Müller, F., Marques, J. C., Bastianoni, S., & Jørgensen, S. E. (2020). Thermodynamics in Ecology-An Introductory Review. Entropy (Basel, Switzerland), 22(8), 820. https://doi.org/10.3390/e22080820 Image of Terrestrial Ecotone https://www.pmfias.com/wp-content/uploads/2016/05/ecotone- grassland.jpeg Image of Ecotone https://ec0l0gical.files.wordpress.com/2013/12/ecotone.jpg Image of Pyramid of Energy https://qph.cf2.quoracdn.net/main-qimg- af6482a39081dd78f66f6eb888122689-lq Image of Pyramid of Numbers https://cdn.kastatic.org/ka-perseus- images/aa7160f542bb2108744f41b6a2b7a7bcaadaa6c5.png Image of Grassland https://www.reference.com/content/424724/ea359fad648ff77cc53736c2a73c2053.jpg Image of Forest Ecosystem https://cff2.earth.com/uploads/2020/10/20155502/forest- 3795202_1280.jpg Image of Typical Upright Pyramid of Biomass (Terrestrial Ecosystem) https://image.slidesharecdn.com/energytransferinecosystems-120914163642-phpapp02/95/energy- transfer-in-ecosystems-8-728.jpg?cb=1347640820