Ecosystems – What do we already know? • What is an ecosystem? • Create an ecosystems mindmap
Ecosystems revision – Important definitions • Ecology • Species • Population • Community • Ecosystem • Habitat • Environment • Biome
Ecology • Ecology is the study of the distribution and abundance of living organisms and how these properties are affected by interactions between the organisms and their environment
Species - Groups of similar individuals that can reproduce fertile offspring (e.g. kookaburra, snow gum) • Population - Group of organisms of the same species living in the same area at a particular time • Community - Groups of different populations in an area or habitat
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.
Environment - Both living (biotic) and non-living (abiotic) surroundings of an organism • Habitat – the place where an organism lives
Ecosystem - A community together with its environment. Any environment containing organisms interacting with each other and the non-living parts of the environment (e.g. rainforest, freshwater pond) • Biome - Large regional system characterised by major vegetation type (e.g. desert); region of earth with similar ecosystems grouped together
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 environments on land which covers around 35% of the Earth’s surface. • Differences in the climate and topography of the land have produced many different terrestrial environments.
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.
Dot Point 8.2.1a • Compare the abiotic characteristics of aquatic and terrestrial environments:
Abiotic Characteristics of Aquatic and Terrestrial Environments
Dot Point 8.2.1b • Identify factors determining the distribution and abundance of a species in each environment:
Distribution Distribution refers to the region where an organism is found. Distribution of rabbits in AustraliaAdapted from: Clarke GM et al (2000). Environmental Pest Species in Australia. Internal report, Department of the Environment and Heritage, Canberra.
Distribution • It is usually uneven throughout the ecosystem • Organisms are found where abiotic and biotic factors favour them • Organisms are distributed where: Survival rate is high Predation is low Requirements for survival are met
Abundance Abundance is the number of individuals of the same species within an area. • Not the same throughout environment • Changes over time: Increases due to births and immigration Decreases due to deaths and emigration
Abiotic Factors Affecting Distribution and Abundance • Light • Strength of wind • Rainfall • Temperature variations • Topography • Tides, currents and waves • Water (amount, salinity, pH) • Substrate • Space and shelter • Oxygen
Biotic Factors Affecting Distribution and Abundance • Availability of food • Number of competitors • Number of mates available • Number of predators • Number and variety of disease causing organisms
Measuring Population Distribution and Abundance • A population is a group of similar organisms living in a given area as a time • Populations can never be 100% accurately counted. Why? • Populations are estimated using sampling techniques. These make an estimate, which is roughly accurate of the population.
Process and analyse information obtained from a variety of sampling studies to justify the use of different sampling techniques to make population estimates when total counts cannot be performed: Measuring Distribution • Transect Measuring Abundance • Plants – Quadrats • Animals – Capture-Recapture
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 cross- section of the ecosystem. This cross-section is called a transect.
Transects Georges River Environmental Education Centre http://www.georgesriv-e.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.
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
Population growth • Growth is initial slow as the species adjust to the environment and establishes reproductive patterns • The population becomes established and growth is more rapid • Environmental factors such as competition for the same resources causes the curve to level of (reach equilibrium)
Predation • A detrimental relationship in which one organism kills and eats another one
Identify examples of allelopathy, parasitism, mutualism and commensalism in an ecosystem and the role of organisms in each type of relationship:
Allelopathy • This is the production by a plant of specific chemicals (allelo-chemicals) which inhibit the growth of other plants around it • Example: the Casuarina. Its leaves contain allelo-chemicals, so as they dropped to the floor, they released the chemicals, preventing the growth of other plants in the area
Parasitism • This is a relationship between two organisms where one benefits at the expense of the other organism • Example: the pimple wasp. It lays its eggs on the leaves of the mangrove. The larvae eat through the leave when they hatch and the leaf is damaged
Mutualism • A relationship between two organisms where both of them benefit • Example: lichen. This consists of a fungus and an alga joined together. The fungi provides structure and the alga provides food
Commensalism • A relationship between 2 organisms where only one benefits, and the other get no harm and no benefit • Example: the golden orb-weaving spider and the dewdrop spider. The weaving spider makes a web, and catches its prey with it. It leaves scraps behind. The dewdrop spider eats the leftovers.
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.
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 glucose + oxygen REACTANTSENERGY PRODUCTS SOURCE
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.