Human Impacts on Ecosystems SAC Revision

Demonstrate an understanding of how organisms are linked through feeding relationships, and give examples of food chains and food webs. organisms are linked through feeding relationships, as organisms need energy and producers are the only organism able to convert light energy into chemical energy and store it in its tissues. For other organisms to receive that energy they must get it through there feeding (food chains). A herbivore will eat the producer and then get some of the energy, then a carnivore will eat the herbivore and get some of the energy. Each level that goes up decreases in the amount of energy uptake as energy is lost through heat. Organisms do not only have one food source though and eat a variety which is shown through a food web which is linked food chains. An example of a food chain is:grass -> mouse -> feral cat -> eagleAn example of a food web is:in one note chapter 21Classify organisms as producer or consumers, and consumers as herbivores, carnivores, scavengers, detritivores or decomposes.A producer is an autotroph which is an organism that can create its our own food, while consumers are heterotrophs which are organisms that cannot create there own food and rely on producers. Consumers are herbivores, carnivores, scavengers, detritivores, and decomposers. A herbivore is an organism that feeds directly on producers.A Carnivore is an organism that feeds directly on other consumers. A scavenger is an organism that feed of the remains of dead animals or plants. A detritivore is an organism that eats small particles of dead plants and animal organic matter, and waste products of other species. A decomposer are microscopic consumers such as bacteria which secrete enzymes over dead material to breakdown the material and release the nutrients from the material back into the environment. Explain how species influence one another through competition and predation.The presence of other organisms may limit the distribution of some species through inter-specific competition (competing with different species for the same supply of food, water, space, nest sites, or any environmental resource in limited supply). Usually with organisms on the same trophic level as they use similar resources, competition can lead to one species being forced out of a habitat by its competitor. Predation is the interaction between two organisms of different species where one species consumes the other species. It is important for influencing the distribution, population, and the diversity of species in a community. Most of the time predation leads to increase in predator size, and decrease in prey size, the effects in the population may effect the community, changing the population of other species. Recognise examples of symbiosis (mutualism, commensalism, parasitism) and pollination, which are close interactions between organisms that my benefit or harm the species involved. Mutualism is where two organisms live in close range of each other and both organisms benefit from the relationship. An example of this is in most plants, which have a mutualism relationship with fungi called a mycorrhiza, where the plant gets an extra supply of phosphorus and the fungi gets sugar. Mutualism in some animals occurs when micro-organisms live in the host animals digestive tract and breaks down cellulose.Commensalism is where two organisms live in close range to each other and one organism benefits from the interaction, and the other is neither benefited nor harmed. An example of this is where Mites will attach to wasps, flies or beetles for transportation.Parasitism is where a two organism live in a partnership, where one organism is benefiting while the other organism is harmed. An example is a koala in a eucalypti tree, or a tapeworm in an animal. Pollination is where organisms transport the pollen, and both are usually benefited; animals in the form of nectar and the plants use the animals for the dispersal of their seeds. Though it is not considered symbiosis as once the pollinating is complete the bee and the plant no longer have a partnership. Explain how energy flows through ecosystems as a consequence of food chains.Energy flows through ecosystems first from the sun which provides a continual source of energy, and then producers convert the light energy into chemical energy, that energy flows as herbivores eat the plant and get some of the energy (some was lost for heat and cellular respiration in the plant), then a first order carnivore eats a herbivore, getting some energy, then a second order carnivore etc. through each level the energy flow decreases. Define the terms 'primary productivity' and 'biomass,' and the main environmental factors that limit productivity.Primary productivity is the rate at which producers can convert sunlight energy into chemical energy. And biomass is the amount of new growth (plant and animal tissue used as fuel) that accumulates in an ecosystem, measured as dry weight per unit area. The main environmental factors that limit productivity are:- low sunlight intensity- low temperature- low soil nutrient- low rainfall- low levels of mineral nutrientsUnderstand an ecological pyramid, which shows the decline in energy that occurs at each trophic level (link) in a food chain through loss of heat. Heats is lost at each trophic level as organisms need to keep themselves warm to be able to function. An ecological pyramid shows the loss of energy and biomass. Image at bottom. Explain how toxins can become more concentrated along food chains. Toxins are added into an ecosystem and producers absorb the toxins, and consumers eat the producers and along the food chain larger animals have an accumulation of toxins in them from the animals that they have eaten they have had the toxin, as the toxin stays in the tissue and does not leave an organism, and usually along a food chain organisms who are higher up will consume more. Understand how matter cycles through ecosystems, including the role of decomposers in the recycling process.Decomposers role in recycling matter through ecosystems, is when animals die the decomposers consume the body to extract energy for their own growth and in the process they break down organic molecules and release chemical nutrients as simple compounds, producers then use the compounds to create new organic matter. Carbon cycle: Carbon enter food chains via photosynthesis, plants absorb carbon dioxide in their leaves (from the air), they use it to make organic matter which accumulates as plant tissue, the carbon is passed through the food chain as organic matter. Through cellular respiration carbon is released from the food chain into the atmosphere. Plants, animals and decomposers all release carbon dioxide. Nitrogen cycle: The nitrogen cycle depends on bacteria to fix Nitrogen in a form that plants can take up and can move through food chains (into nitrite ions and nitrate ions). Bacteria also release Nitrogen back into the atmosphere to complete the cycle (in the process called nitrification).Phosphorus cycle: Phosphorus is slowly released into soil and water from rocks, it is dissolved in the soil and absorbed by plant roots. It passes through food chains until decomposers return it to the non-living part of the ecosystem. Phosphorus eventually reaches the ocean it precipitates as marine sediments, which are compressed into rocks, uplifted and exposed. and the Phosphorus cycle is complete.