A Local Ecosystem Abiotic features of the environment Abiotic features are the non-living components of the environment. They include, Physical features: temperature, rainfall, wind, light intensity, humidity, soil type, water, landform Chemical features: pH of soil or water, salinity, availability of gases Biotic features of the environment Biotic features are the living components of the environment. This includes: Plants Animals Micro-organisms Aquatic environments Environments can be classified as aquatic (water) or terrestrial (land). Aquatic environments can be either freshwater or marine (saltwater). Terrestrial environments Terrestrial environments are found in different climates and range from deserts, grasslands and rainforests to mountain regions. Aquatic v’s terrestrial Organisms living in aquatic and terrestrial environments have to survive different abiotic conditions. When comparing the difference between the two it is necessary to look at features such as: buoyancy, pressure, temperature, availability of gases, light penetration and viscosity. Community and population A community can be defined as the set of interacting organisms within an ecosystem. A population is a group of individuals of the same species living in the same area. Distribution Distribution refers to the region where an organism is found. Distribution of rabbits in Australia Adapted from: Clarke GM et al (2000). Environmental Pest Species in Australia. Internal report, Department of the Environment and Heritage, Canberra. Transects The distribution of plants can be determined by marking out a straight line across an area, noting the types of plants present, and plotting their position along this line on a diagram. This indicates the distribution of plants along a crosssection of the ecosystem. This cross-section is called a transect. Transects Georges River Environmental Education Centre http://www.georgesrive.schools.nsw.edu.au/Vegetation_study.htm Abundance Abundance is the number of individuals of the same species within an area. Abundance is usually found by taking small samples of a community and using the data to estimate the population in the ecosystem as a whole. Quadrats The abundance of a plant species is often found by marking out quadrats. Individuals within the quadrats are counted and the average number per area (density) is calculated. This information can then be used to estimate the abundance in the whole ecosystem. The more quadrats used, the more accurate the estimate. Quadrats Capture – mark - recapture This method of sampling involves: catching a number of individuals of a species marking or tagging them releasing them again at a later time catching another group and counting the number of tagged individuals among them This method is useful for mobile populations. Trends in population estimates Variable that can influence population size over time include, Birth rate Death rate Migration rate Environmental factors such as availability of food, shelter and water, presence of predators Photosynthesis The initial source of energy in an ecosystem is light from the sun. Some of the light absorbed by plants is converted through photosynthesis into chemical energy in the form of carbohydrates such as glucose. Photosynthesis is summarised as: light carbon dioxide + water REACTANTS glucose + oxygen ENERGY SOURCE PRODUCTS Respiration Some of the glucose produced by photosynthesis is broken down during the process of respiration. Respiration can be summarised as follows: Glucose + oxygen water + carbon + energy dioxide The energy produced during respiration is then used for cellular processes. Energy transfer in an ecosystem Light energy Converted into carbohydrates Chlorophyll Photosynthesis Glucose Transported through the plant Respiration Energy for cell processes Uses of energy by organisms Living organisms need a constant supply of energy to maintain cellular activities and stay alive. In ecosystems the initial source of energy is light from the sun. This is used by plants during photosynthesis to produce carbohydrates. Organisms (i.e. plants) that can manufacture their own food from inorganic materials are called autotrophs. Producers and consumers Green plants provide the entire input of energy to an ecosystem and are called producers. When animals (herbivores) eat plants, the carbohydrates stored in plants are converted back into glucose. The glucose is broken down during respiration to provide the animal’s energy requirements. Similarly, when carnivores eat other animals, this chemical energy is passed on. Energy transfer in ecosystems Eaten by Plant Converted into other substances animal Carbohydrates digested to glucose Respiration Energy for animal cellular process Food chains and webs Food chains show the flow of energy through ecosystems. PRODUCER grass FIRST ORDER CONSUMER wallaby SECOND ORDER CONSUMER dingo Trophic levels Animals are consumers. An organism that feeds on plants is a first-order consumer. An organism that feeds on a first-order consumer is called a second-order consumer, and so on. The level occupied by a consumer in a food chain is referred to as a feeding or TROPHIC level. Firstorder consumers occupy the first trophic level; second-order consumers occupy the second trophic level, and so on. Food webs The interrelationship between many food chains is called a food web. Biomass Biomass is an estimate of the amount of matter in a given population of organisms. Biomass for different trophic levels is compared in a biomass pyramid. A biomass pyramid shows how the quantity of matter in living things changes along a food chain. Biomass pyramid The base of the pyramid represents the matter in producers. The next level shows biomass of 1st order consumers and so on. Biomass pyramid At each level in the pyramid biomass is smaller than in the trophic level below. At each level biomass is lost. An energy pyramid shows the total energy in trophic levels and how that energy is lost along a food chain. Energy pyramid Decomposers Organisms that use the organic matter of dead plants and animals are called decomposers. They release digestive enzymes to break down organic matter and then absorb the products of digestion. Decomposers include fungi and bacteria. Decomposers do not fit readily into one trophic level. Competition for resources Competition is a relationship in which two organisms compete for a limited resource. In the short term this results in a decrease in the abundance of one of the species. In the long term it can result in extinction of the less successful species. Competition for resources. Competition is one pressure that influences the evolution of organisms. For example, competition is one of the factors that results in organisms adapting to occupy distinct niches. Adaptations All organisms have adaptations that help them to survive. Organisms that are adapted to their environment are able to: obtain air, water, food and nutrients cope with physical conditions such as temperature, light and heat defend themselves from their natural enemies reproduce respond to changes around them Adaptations Structural adaptations are the physical characteristics of an organism (e.g., skin color, shape, body covering). Behavioral adaptations are the ways in which an organism behaves. Physiological adaptations are those that allow an organism to perform certain biochemical reactions (e.g., making venom, secreting slime, being able to keep a constant body temperature).