Ecosystem & Energy Flow Lecture Notes PDF

LECTURE 6: ECOSYSTEM & ENERGY FLOW ENVIRONMENTAL SCIENCE Prepared by: DIVINE GRACE S. BATENGA, MSc., LPT Subject Teacher  LEARNING OUTCOMES Upon the completion of this lesson, you are expected to: a) distinguish the differences in the structure...

LECTURE 6: ECOSYSTEM & ENERGY FLOW ENVIRONMENTAL SCIENCE Prepared by: DIVINE GRACE S. BATENGA, MSc., LPT Subject Teacher  LEARNING OUTCOMES Upon the completion of this lesson, you are expected to: a) distinguish the differences in the structure ad function of different types of ecosystem. b) demonstrate ability to explain the energy flow in the ecosystem by creating food chain, food web, ad ecological pyramid. 2  ECOSYSTEM An ecosystem is a unit of nature and the focus of study in ecology. It consists of all the biotic and abiotic factors in an area and their interactions. 3 LEVELS OF ECOLOGICAL ORGANIZATION SPECIES a group of individuals that are genetically related and can breed to produce fertile young. POPULATON a group of organisms belonging to the same species that live in the same area and interact with one another. COMMUNITY is all of the populations of different species that live in the same area and interact with one another A community is composed of all of the biotic factors of an area. ECOSYSTEM includes the living organisms (all the populations) in an area and the non- living aspects of the environment. 4  2 Types of Ecosystem ❑ NATURAL ECOSYSTEM ▪ Aquatic Ecosystem ▪ Terrestrial Ecosystem ❑ ARTIFICIAL ECOSYSTEM ▪ Man-made ecosystem ▪ Aquarium 5  TERRESTRIAL ECOSYSTEM FOREST ECOSYSTEM ▪ High rainfall ▪ Large number of organism and flora ▪ Highly diverse population Function: ▪ Watershed Protection ▪ Atmospheric regulation ▪ Soil Erosion Control ▪ Wind Erosion Control 42 TERRESTRIAL ECOSYSTEM DESERT ECOSYSTEM ▪ High temperature, intense sunlight and low water ▪ Flora and fauna are very poorly developed and are adapted to live in extremities ▪ Scarcely populated Function: ▪ Solar energy resource ▪ Mineral resource 43  TERRESTRIAL ECOSYSTEM GRASSLAND ECOSYSTEM ▪ Marginal rainfall ▪ Vegetation is dominated by grasses ▪ Densely populated Function: ▪ Grassland provide food ▪ Grasslands Are Breeding Areas 44 AQUATIC ECOSYSTEM Low temperature and sunlight Soil and vegetation is submerged Competitive organism Flora and fauna had adapted Densely populated Types of Aquatic ecosystem: Marine- ocean, sea Lotic (running water)- river, spring Lentic (standing water)- pond, lake, swamp 9  COMPONENTS OF AN ECOSYSTEM ABIOTIC BIOTIC -Any non-living organisms in an ecosystem. -Any living organisms in an ec osystem. 10 ABIOTIC COMPONENTS Physical factors Chemical substances Wind- removes water vapour Water surrounding the plants Temperature- affec ts the Oxygen evaporation rate of water from Carbon dioxide plants and animals Light- ac tivities of plants and Nitrogen animals are affected by relative Carbon length of day and night Types of Soil- affec ts the degree of Complex substances aeration, root penetration, nutrient (proteins, lipids and supply carbohydrates) -plays a c ruc ial role in determining the kind of plants and animals found in partic ular ec osystem 11 BIOTIC COMPONENTS PRODUC ERS C ONSUMERS DEC OMPOSERS 12  BIOTIC COMPONENTS PRODUCERS AUTOTROPHS (self-nourishing) Green plants Manufac ture food through Photosynthesis (6C O 2 + 6H2O ------> C 6H12O 6 + 6O 2) Sunlight energy Green plants also take substances such as nitrogen and sullfur from the environment and convert them into plant materials that can be used by other orgnaisms for food. Phytoplanktons- microscopic plants -when they become abundant, they can give a body of water a green color Phytoplankton 13 4 9  BIOTIC COMPONENTS CONSUMERS HETEROTROPHS (feeds on other) A living thing that gets its food from eating other living things. Different types of C onsumers: a) Herbivores- are those that eat plants only b) Carnivores- are those that eat other animals only c) Omnivores- those that eat both plants and animals 14 4 9 BIOTIC COMPONENTS DEC OMPOSERS Fungi A living thing that breaks down other living things to get nutrients and energy. They use the bodies of dead animals and plants for their food and release the minerals and other nutrients back into the environment Bacteria for use by other organisms. Bacteria- most abundant dec omposers Fungi- fast-ac ting dec omposers Earthworms- break down and rec yc le the matter from dead plants and animals, as well as waste products, returning it back into the soil. “Janitors of Nature” Earthworms 5 1  NICHE One of the most important concepts associated with the ecosystem is the niche. A niche refers to the role of a species in its ecosystem. It includes all the ways that the species interacts with the biotic and abiotic factors of the environment. Two important aspects of a species’ niche are the food it eats and how the food is obtained. 16  HABITAT The habitat is the physical environment in which a species lives and to which it is adapted. A habitat’s features are determined mainly by abiotic factors such as temperature and rainfall. These factors also influence the traits of the organisms that live there. 17  COMPETITIVE EXCLUSION PRINCIPLE A given habitat may contain many different species, but each species must have a different niche. Two different species cannot occupy the same niche in the same place for very long. This is known as the competitive exclusion principle. If two species were to occupy the same niche, what do you think would happen? 18 FOOD CHAINS AND FOOD WEBS 19  FOOD CHAINS AND FOOD WEBS Food chains and food webs are diagrams that represent feeding relationships. They show who eats whom. In this way, they model how energy and matter move through ecosystems. 20  FOOD CHAINS A food chain represents a single pathway through which energy and matter flow through an ecosystem. Food chains are generally simpler than what really happens in nature. Most organisms consume—and are consumed by—more than one species. 21  FOOD WEBS A food web represents multiple pathways through which energy and matter flow through an ecosystem. It includes many intersecting food chains. It demonstrates that most organisms eat, and are eaten, by more than one species. 22  TROPHIC LEVELS The feeding positions in a food chain or web. All food chains and webs have at least two or three trophic levels. (maximum of four trophic levels) Many consumers feed at more than one trophic level: ▪ Humans for example, are primary consumer when they eat plants such as vegetables. ▪ They are secondary consumers when they eat cows. ▪ They are tertiary consumers when they eat salmon. 23 TROPHIC LEVELS We are primary consumer when we eat plants. (vegetable) We are tertiary consumer when we eat salmon. We are secondary consumer when we eat cow. (meat) 24 Trophic Level Where It gets Food Example 1st Trophic Level: Makes its own food Plants make food Producer 2nd Trophic Level: Consumes producers Mice eat plant seeds Primary consumer 3rd Trophic Level: Consumes primary Snakes eat mice Secondary consumer consumers 4th Trophic Level: Tertiary Consumes secondary Hawks eat snakes Consumer consumers 25 ECOSYSTEMS, ENERGY, MATTER ❑Ecosystem obey physical laws The law of conservation of energy states that energy cannot be created or destroyed but only transformed. ▪ Plants and other photosynthetic organisms convert solar energy to chemical energy, but the total amount of energy does not change. ▪ The total amount of energy stored in organic molecules plus the amounts reflected and dissipated as heat must equal the total solar energy intercepted by the plant. 26 ECOSYSTEMS, ENERGY, MATTER ❑Ecosystem obey physical laws The second law of thermodynamics states that some energy is lost as heat in any conversion process. ▪ We can measure the efficiency of ecological energy conversions. 27 ECOSYSTEMS, ENERGY, MATTER ❑Ecosystem obey physical laws Chemical elements are continually recycled. ▪ A carbon or nitrogen atom moves from one trophic level to another and eventually to the decomposers and back again. 28 ECOSYSTEMS, ENERGY, MATTER ❑Trophic relationships determine the routes of energy flow and chemical cycling in ecosystems. Autotrophs, the primary producers of the ecosystem, ultimately support all other organisms. Most autotrophs are photosynthetic plants, algae or bacteria that use light energy to synthesize sugars and other organic compounds. Chemosynthetic prokaryotes are the primary producers in deep-sea hydrothermal vents. 29 ECOSYSTEMS, ENERGY, MATTER ❑Trophic relationships determine the routes of energy flow and chemical cycling in ecosystems. Heterotrophs are at trophic levels above the primary producers and depend on their photosynthetic output. Herbivores that eat primary producers are called primary consumers. Carnivores that eat herbivores are called secondary consumers. Carnivores that eat secondary producers are called tertiary consumers. 30 ECOSYSTEMS, ENERGY, MATTER ❑Trophic relationships determine the routes of energy flow and chemical cycling in ecosystems. Another important group of heterotrophs is the detritivores, or decomposers. They get energy from detritus, nonliving organic material such as the remains of dead organisms, feces, fallen leaves, and wood. Detritivores play an important role in material cycling. 31 ECOSYSTEMS, ENERGY, MATTER ❑Decomposition connects all trophic levels. The organisms that feed as detritivores from a major link between the primary producers and the consumers in an ecosystem. Detritivores play an important role in making chemical elements available to producers. ▪ Detritivores decompose organic material and transfer chemical elements in inorganic forms to abiotic reservoirs such as soil, water, and air. Producers then recycle these elements into organic compounds. An ecosystem’s main decomposers are fungi and prokaryotes. 32  PRIMARY PRODUCTION IN ECOSYSTEMS The amount of light energy converted to chemical energy by an ecosystem’s autotrophs in a given time period is an ecosystem’s primary production. ❑An ecosystem’s energy budget depends on primary production. ▪ Most primary producers use light energy to synthesize organic molecules, which can be broken down to produce ATP. ▪ The amount of primary production sets the spending limit of the entire ecosystem. ▪ Different ecosystems differ greatly in their productions as well as in their contribution to the total production of the Earth. Tropical rain forest are among the most productive terrestrial ecosystems. 33  PRIMARY PRODUCTION IN ECOSYSTEMS A global energy budget can be analyzed: Every day, the Earth is bombarded by approximately 1023 joules of solar radiation. The intensity of solar energy striking Earth varies with latitude, with the tropics receiving the greatest input. Most of this radiation is scattered, absorbed, or reflected by the atmosphere. Much of the solar radiation that reaches Earth’s surface lands on bare ground or bodies of water that either absorb or reflect the energy. Only a small fraction actually strikes algae, photosynthetic prokaryotes, or plants, and only some of this is of wavelengths suitable for photosynthesis. Of the visible light that reaches photosynthetic organisms, only about 1% is converted to chemical energy. ✓ Although this is a small amount, primary producers produce about 170 billion tons of organic material per year. 34  PRIMARY PRODUCTION IN ECOSYSTEMS ❑In aquatic ecosystems, light and nutrients limit primary production. Light is a key variable controlling primary production in oceans, since solar radiation can only penetrate to a certain depth known as the photic zone. ❑ In terrestrial ecosystems, temperature and moisture are the key factors limiting primary production. Tropical rain forests, with their warm, wet conditions, are the most productive of all terrestrial ecosystems. By contrast, low-productivity ecosystems are generally dry (deserts) or dry and cold (arctic tundra). 35  SECONDARY PRODUCTION IN ECOSYSTEMS The amount of chemical energy in consumers’ food that is converted to their own new biomass during a given time period is called the secondary production of an ecosystem. ❑ The efficiency of energy transfer between trophic levels is usually less than 20%. Energy is passed up the food chain from one trophic level to the next. However, only about 10 percent of the total energy stored in organisms at one trophic level is actually transferred to organisms at the next trophic level. The rest of the energy is used for metabolic processes or lost to the environment as heat. The amount of energy at different trophic levels can be represented by an energy pyramid 36  SECONDARY PRODUCTION IN ECOSYSTEMS Trophic Levels and Biomass With less energy at higher trophic levels, there are usually fewer organisms as well. Organisms tend to be larger in size at higher trophic levels, but their smaller numbers result in less biomass. Biomass is the total mass of organisms at a trophic level. 37 The Green World Hypothesis Herbivores consume a small percentage of vegetation. Predators are, ironically, the key to keeping the world green, because they keep the numbers of plant-eating herbivores under control. 38  The Green World Hypothesis ❑ According to the green world hypothesis, herbivores consume relatively little plant biomass because they are held in check by a variety of factors, including predators, parasites, and disease. The green world hypothesis proposes several factors that keep herbivores in check: Plants have defenses against herbivores. Nutrients, not energy supply, usually limit herbivores. Animals need certain nutrients that plants tend to supply in relatively small amounts. The growth and reproduction of many herbivores are limited by availability of essential nutrients. Abiotic factors limit herbivores. Temperature and moisture may restrict carrying capacities for herbivores below the level that would strip vegetation. 39  THE CYCLING OF CHEMICAL ELEMENTS IN ECOSYSTEMS Chemical elements are available to ecosystems only in limited amounts. Life on Earth depends on the recycling of essential chemical elements. Nutrient circuits involve both biotic and abiotic components of ecosystems and are called biogeochemical cycles. 40 End of Lecture… 41  References: Akre B, Brainard J, Goose H, Rogers-Estable, and Stewart R (2011). Introduction to Environmental Science, FlexBook Platform, USA. Allaby M. (1996). Basics of Environmental Science, 2nd edn. Routledge, London. Saravanan K, Ramachandran S, and Baskar R (2005). Principles of Environmental Science & Technology, New Age International (P) Ltd., Publishers, New Delhi. Singh Y.K (2006). Environmental Science, New Age International (P) Ltd., Publishers, New Delhi. https://today.duke.edu/2006/02/greenworld.html 42