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Matter cycles and energy dissipates through the biosphere and its component ecosystems. The concept of an ecosystem is used to explain energy flow and nutrient recycling and to quantify large-scale and long-term processes. Students will study habitat destruction, ecological succession and changes to populations, focusing on the need to balance the interests of a growing human population with sustainable ecosystems. UNIT D: CHANGES IN Living Systems
UNIT D: OUTCOMES • analyze ecosystems and ecological succession in the local area and describe the relationships and interactions among subsystems and components • analyze and investigate the cycling of matter and the flow of energy through the biosphere and ecosystems as well as the interrelationship of society and the environment • analyze and describe the adaptation of organisms to their environments, factors limiting natural populations, and evolutionary change in an ecological context.
Water: An Essential Abiotic Factor • investigate and analyze an aquatic or a terrestrial local ecosystem, distinguish between biotic and abiotic factors, describe how these factors affect population size and • infer the abiotic effects on life; e.g., light, nutrients, water, temperature • infer biotic interactions; e.g., predator-prey relationships, competition, symbiotic relationships • infer the influence of biota on the local environment; e.g., microclimates, soil, nutrients • describe the potential impact of habitat destruction on an ecosystem
Abiotic vs. Biotic Factors • In any part of the biosphere, there are abiotic and biotic factors: • Abiotic factors are physical, non-living parts of an ecosystem. • Biotic factors are living organisms found an ecosystem. • NOTE: “abiotic” is not the same as “dead.” Dead things were once living and are therefore still considered biotic parts of an ecosystem.
Abiotic vs. Biotic Factors • Wind • Water • Temperature • Nutrients found in soil • Sunlight • Mammals • Trees • Fish • Plants/ flowers • insects Abiotic Biotic
Ecosystems • An ecosystem is a broad definition that refers to all the organisms in an area as well as the abiotic factors with which they interact. • It is IMPORTANT to remember that an ecosystem is more than just animals and plants. It includes many abiotic factors that have a VERY STRONG influence on the success and health of an ecosystem. • Ecosystems vary in size: a fallen tree in a forest can support an ecosystem, our bodies are ecosystems, the boreal forest is an ecosystem.
Ecosystems • This is the MOST IMPORTANT fact: • All life is connected. • Organisms are connected to each other and the abiotic factors they rely on or interact with. • Therefore, ecosystems are what connects all life. • Ecosystems are connected by the organisms that leave or enter them and by the abiotic factors that leave or enter them. • Everything on Earth exists in a closed system.
Habitat • Habitat is all the biotic and abiotic factors present in an area that encourage the reproduction and survival of an organism. • Every organism has a preferred habitat. • Every living thing has certain biotic and abiotic requirements of its habitat. If those minimum requirements are not met, the organism will struggle to survive. • Nutrientsare some abiotic examples of these requirements .they are any element or compound that an organism needs for growth or other functioning.
Water: An Essential Abiotic Factor • Water is perhaps the most important abiotic factor in any ecosystem. • A few facts about water: • 75-90% of all cells are made up of water. • Somewhere between 70-75% if the Earth’s surface is covered in water. • Pure water (only H2O(l)) has a pH of 7 and is neither acidic nor basic. • The same water that existed on the earth millions of years ago is still present today. • Of all the water on the earth, humans can used only use about three tenths of a percent of this water. Such usable water is found in groundwater aquifers, rivers, and freshwater lakes.
Water: An Essential Abiotic Factor • Water is the solvent for life. Many ionic components are dissolved in water and are transported between living cells in fluids such as blood and tree sap. • Water is a finite resource. There is only a certain amount that is useable to use as humans. • When we remove water from the environment (an ecosystem), it is no longer available to other organisms for their use. This is becoming a major problem in the world.
Biotic Factors: The Influence of Living Things • investigate and analyze an aquatic or a terrestrial local ecosystem, distinguish between biotic and abiotic factors, describe how these factors affect population size and • infer the abiotic effects on life; e.g., light, nutrients, water, temperature • infer biotic interactions; e.g., predator-prey relationships, competition, symbiotic relationships • infer the influence of biota on the local environment; e.g., microclimates, soil, nutrients • describe the potential impact of habitat destruction on an ecosystem
Ecology • If ecosystems are built on the interactions of biotic and abiotic factors in an area, then ecology is the study of those interactions. • Ecologists are scientists who specialize in the study of interactions within ecosystems. • The study of ecology takes on many forms and is a difficult and challenging discipline. • Remember, organisms interact with each other and the abiotic factors that surround them. This forms a complex web of connections between all components of an ecosystem. • It is an ecologist’s job to make sense of that web.
Ecosystems • We have mentioned that ecosystems, are based on the complex interactions between all the biotic and abiotic factors within an area. • As a rule, ecosystems cover a larger geographic area than do communities. • For ecologist, studying an entire ecosystem is difficult – they are made up of many communities that first need to be studied before a more complete picture of the ecosystem is made.
Biomass • Biomass is the dry mass of all the living things occupying a habitat or ecosystem. • It is generally accepted that biomass is a good measure as to how many of each organism are present in a habitat or ecosystem.
Organization of Biotic Factors • Within ecosystems, it is possible to organize biotic factors (living things) into categories. • Populations • A group of organisms, all of the same species, which interbreed and live in the same area at the same time. • For example, all the deer mice occupying a particular meadow in the month of June are a population. • Ecologists often study ecosystems at the population level in order to better understand that organism’s role in the ecosystem.
Organization of Biotic Factors • Communities • A community is more complex than a population. It is the interacting populations living in a certain area at a certain time. • Therefore, a community is made up of more than one group of organisms that interact with each other. • For example, a meadow in the month of June could be considered a community. There are plants, insects, birds and mammals that all interact with each other. • Studying communities is much more difficult to do. Ecologists struggle with the complexity of the connections between all the populations within that community.
Interactions in Ecosystems –Symbiosis • Symbiosis is a type of interaction between biotic factors in an ecosystem. • Symbiosis is a long-lasting, ecological relationship that benefits at least one organism of two different species that live in close contact. • One of the important things to remember about symbiosis is that it NEEDS to be long-lasting. If the interaction is momentary (like a bear attacking something) then it is not symbiosis. • There are three types of symbiosis that are recognized by ecologists.
Interactions in Ecosystems –Symbiosis • Mutualism • This is a type of symbiosis where both organisms involved benefit from the relationship. • Nitrogen-fixing bacteria on the roots of some plants use the nutrients in the roots to sustain themselves (a benefit). The roots benefit from the relationship because the bacteria provide roots with a good source of nitrogen • Commensalism • This is a type of symbiosis where one organism benefits and the other is neither benefitted nor harmed. • For example, brown-headed cowbirds follow herds of bison around. The cowbirds eat flies that harass the bison (a benefit) and the bison are largely unaffected by the interaction.
Interactions in Ecosystems –Symbiosis • Parasitism • This type of symbiosis involves one organism that benefits from the relationship and another which is harmed. • For example, yellow-bellied sapsuckers (a woodpecker) create small, square-shaped holes in the sides of trees. Sap leaks out of those holes, attracting ants which get caught in the sap. The sapsucker benefit by feeding on the trapped ants, the tree, however is harmed by the interaction (it loses sap).
Interactions in Ecosystems –Predator-Prey Interactions • A predator is an organism that hunts another organism for the purpose of killing and eating it. • A prey animal is an organism that is hunted by a predator. • A predator-prey relationship is an interaction between two organisms where one organism (the predator) hunts, kills and eats the other organism (the prey). • Predator-prey relationships are common in all ecosystems. It is important, however, to note that parasitism is NOT predation, nor is a consumer eating a plant (there is no hunting taking place)
Interactions in Ecosystems –Competition • The interesting thing about ecosystems is that resources are limited. A prey species is not usually a prey species for only ONE organism. • In many cases competition for resources (for example a prey species) is a significant problem for organisms to overcome in order to be successful. • If an organism isn’t well-suited to compete for a resource, then it will struggle to survive. • The resources that organisms compete for can be either biotic factors (plants, meat, etc.) or abiotic factors (water, air, sunlight, etc.) • In many cases, competition for resources drives evolution.
The Web of Life • analyze and describe how energy flows in an ecosystem, using the concepts of conservation of energy (second law of thermodynamics); energy input and output through trophic levels, food webs, chains and pyramids; and specific examples of autotrophs and heterotrophs • explain why population size and biomass are both directly related to the trophic level of the species and explain how trophic levels can be described in terms of pyramids of numbers, biomass or energy.
Ecological Niches • Within an ecosystem, each organism plays a particular role. Some organisms may fill a number of niches depending on how they are connected to the ecosystem. • An ecological niche is a specific role an organism plays in its ecosystem. • American Ecologist Eugene Odum used the analogy that, “ If an organisms habitat is it’s “address”, the niche is the organism’s “profession”.
Ecological Niches • Producer: an organism that uses light energy to synthesize sugars and other organic compounds through the process of photosynthesis[ the conversion of light energy to chemical energy in the forms of sugars and organic molecules] (in most ecosystems, these are plants). • Consumer:a broad definition referring to any organism that uses other organisms as a source of energy (i.e. they eat other organisms). • Primary consumer (herbivore): an organism that east green plants, algae or phytoplanktons. • Secondary consumer: an organism that eats herbivores. • Tertiary consumer: an organism that eats secondary consumers.
Ecological Niches • Carnivore: an organism that kills and eats other animals. • Omnivore: an organism that eats both plants and animals. • Scavenger: a bird or animal that feeds on dead and decaying animals that it did not kill itself. • Decomposer: (or detritivore) an organism that breaks down complex organic molecules into simpler molecules.
Energy Flow in Ecosystems • Ecosystems are all about energy and matter. As you will learn, energy flows and matter cycles. • Energy flow starts with the ultimate source of energy in our solar system – the Sun. From the Sun, energy flows through the producers and into the consumers at different levels. • Energy flows in steps and each step in the energy pathway is referred to as a trophic level: • Trophic comes from the greek word Trophikos, which means “to nourish”. • A tropic level is the division of species within an ecosystem based upon its energy source. • Producers are the lowest trophic level, followed by primary consumers, secondary consumers, etc. • Energy is lost as we move up trophic levels.
Energy Flow in Ecosystems • The reason that energy is lost as we move up in trophic levels of the energy pyramid is because the higher up you go the more energy is used to survive, thus less is passed on. • There are numerous ways we can represent the flow of energy in ecosystems. We’ll explore a few of these: • Pyramids of numbers, energy and biomass. • Food chains • Food webs
Pyramid of Energy • Amount of energy at each trophic level can be represented by a pyramid of energy. • Tertiary consumers have a larger mass and expend large amounts of energy hunting, which is why the energy levels drop significantly. • Each level will obtain 1/10 or 10% of the energy their prey started out with.
Represents the number of organisms at each trophic level. The pyramid is not always the same, producers can be very large, while others are small. What if we had a largenumber of top-levelconsumers and asmall number of producers? Pyramid of Numbers
Represents the biomass of each trophic level in an ecosystem. Ex. Rainforest ecosystem would store large amounts of solar energy and would contains lots of organic matter = large amount of biomass Tundra gets a lot less energy and would contain less organic matter = smaller amount of biomass Pyramid of Biomass
The Pyramids • Pyramids are a great way to represent the flow of energy in an ecosystem (as well as, in some cases the numbers of individuals of each species in the population). The problem is that they are often difficult to construct: • The pyramid of energy requires us to measure the energy stored by plants and then what is passed on to the next trophic level – a difficult task. • The pyramid of biomass requires us to take the dry mass of all organisms (or at least a portion of them) in order to get the masses correct.
Food Chains • Food Chain - a diagram of “who eats who” in the ecosystem, with one organism at each trophic level. • This is a very simple representation of the flow of energy in an ecosystem. We trace energy from when it enters the ecosystem through the producer and as it passes from one trophic level to the next.
Food Chain 4 5 2 3 1 1 2 3 4 5
Food Webs • Food webs– a diagram made up of interconnecting food chains with many organisms at each trophic level • More accurate because organisms eat more than 1 kind of food and can occupy more than one trophic level • Food webs are quite complex, but give a more complete picture of how energy flows within an ecosystem.
Food Chains and Food Webs • You’ll notice that the food chains and food webs both have arrows. Those arrows represent the flow of energy. • For example, energy flows from the fish to the osprey when the osprey eats the fish. • THIS IS IMPORTANT TO REMEMBER!
The Recycling of Matter • outline the biogeochemical cycles of nitrogen, carbon, oxygen and water and, in general terms, describe their interconnectedness, building on knowledge of the hydrologic cycle from Science 10, Unit D • describe artificial and natural factors that affect the biogeochemical cycles: • nitrogen cycle; e.g., automobile, agricultural and industrial contributions to NOx combining with water to produce nitric acid, nitrogen in manure and fertilizers • carbon cycle; e.g., emissions of carbon oxides from extraction, distribution and combustion of fossil fuels, releases associated with deforestation and cement industries • water cycle; e.g., extraction of ground water, dams for hydro-electricity and irrigation
Matter Cycles • In the last lesson, we described that energy flows through ecosystems. It originates with the sun (in most cases) and flows up the trophic levels. • In ecosystems, matter does the opposite: it cycles. • Matter cycles because the Earth is a closed system – energy is allowed to enter and leave, but matter is not. • Therefore, we have a finite amount of matter to use in our biosphere, therefore it must be cycled (think recycling).
The Biogeochemical Cycles • Matter within our biosphere cycles through biogeochemical cycles. • “Bio” means living, therefore these cycles are connected to living things. • “Geo” means Earth or rock, therefore these cycles are also connected to the rock/Earth. • “Chemical” is obvious – these cycles are linked with chemical reactions. • Each cycle has a living, Earth and chemical reaction connection.
Hydrological (Water) Cycle • Involves the cycling of water in the atmosphere and on the surface of the earth. • driven by solar energy • evaporation • condensation • precipitation
Purposes of the Hydrological Cycle • serves to stabilize the temperature of the surrounding air and land due to the high latent heat of vaporization required for evaporation and the latent heat of fusion for freezing • serves as a purification process • as the water percolates through the soil, it is filtered • “distillation” process – when water evaporates, it leaves potentially harmful substances behind.
Carbon and Oxygen Cycles • Involves the cycling of carbon (usually in CO2(g) form) and oxygen in the atmosphere or as a part of organisms or the land. • photosynthesis and cellular respiration maintain a balance of concentrations of carbon and oxygen in the atmosphere • 6 CO2(g) + 6 H2O(l) C6H12O6(s) + 6 O2(g) (Photosynthesis) • C6H12O6(s) + 6 O2(g) 6 CO2(g) + 6 H2O(l) (Cellular respiration) • Atmospheric concentrations of oxygen and CO2(g) • O2 – 20.95% • CO2 – 0.033% • Oceans and forests serve as a sink for CO2 either absorbing or releasing CO2 to the atmosphere
What if CO2/O2 isn’t balanced? • What would happen if, for some reason, the equilibrium maintained by cellular respiration and photosynthesis is disrupted?
Carbon Cycle • When carbon is not in its organic form it is stored in 3 main areas: the atmosphere (gas), the ocean in sediments, and the Earth’s crust. • Under some conditions carbon is converted to rocks and fossils (coal, petroleum, natural gas) rather than going into immediate circulation. • Organic carbon is also stored in bogs. • There is little oxygen in bogs, decomposition is very slow, and carbon atoms become locked away (formation of coal).
Oxygen Cycle • The oxygen cycle is a mirror image (mostly) of the carbon cycle. Since both are tied in to cellular respiration and photosynthesis, they mirror each other
Nitrogen Cycle • Nitrogen cycling is connected to the atmosphere, the soil and organisms. • Essential for the formation of amino acids (proteins) • Composes 78.08% of atmosphere but cannot be used in its atmospheric form (N2(g)) except for a few cases of nitrifying bacteria • In order to have usable nitrogen, we must convert it first to nitrates. This is done through lightning or nitrogen fixation (by bacteria)
Disturbances to the Cycles • Humans are really good at disturbing the natural cycling of water, carbon, oxygen and nitrogen. • Each time one of these cycles is messed with, it affects the ecosystems connected to the cycles. • In most cases, the effects of “messing” with the cycles are negative, but in some cases, we can have positive effects.
