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Sub topic (b) How it works Ecosystems • Examples of ecosystems include a woodland, ocean , desert, moorland etc.. • The main parts of an ecosystem are the habitats, animals and plants woodland ocean desert Parts of an ecosystem • Habitat – the place where an organism lives • Population – a group of organisms of one species • Community – all the organisms living in a habitat • Ecosystem – all the living things and their environment Producers • Plants harness the sun’s energy in photosynthesis • We call plants producers because they trap light energy from the sun and convert it into chemical energy during photosynthesis. • Consumers eat other organisms • Many animals eat only plants -they are herbivores. We also call animals that eat plants primary (first) consumers • The next group, called the secondary consumers are carnivores or omnivores. They eat primary consumers Consumers A Basic Food Chain Plants absorb light from the sun, which is turned into chemical energy to grow. We call these producers. The herbivores eat the plants, they are called Primary consumers. Secondary consumers eat or prey on primary consumers. They can also be called predators Food chain • A food chain is a diagram which shows how energy flows from producers through primary consumers to secondary consumers in a natural ecosystem • The arrows in a food chain diagram indicate the direction of energy flow • As energy flows along a food chain 90% is lost as the animal uses energy for heat and movement. oak tree producer mouse primary consumer weasel owl secondary consumers Food web • Food chains rarely occur in isolation • Normally a producer is eaten by several herbivores • Each herbivore is preyed upon by several predators • A food web is a diagram which shows a system of interconnecting food chains. Woodland Web 1 •diagram of interconnecting food chains. 1. What is a food web? 2. Name the producer? Green plant 3. From this food web write down a) a complete food chain with 4 organisms b) a complete food chain with 5 organisms c) Name two herbivores? beetle, grasshopper, snail d) Name a primary consumer? beetle, grasshopper, snail 4. Name a secondary consumer? Woodland web 2 shrew, spider, wood mouse, owl 5. Name two prey animals shrew, spider, wood mouse, beetle, grasshopper, snail 6. Name two predators shrew, spider, wood mouse, owl 7. Name two animals which are both predators and prey shrew, spider, wood mouse, 8. Which animal will be least numerous? owl Removal of species from a food web (C) 1. Predict and explain the effect of removing the holly leaf miner from this food web on a) Pigeon population Pigeons increase as they have more food (holly leaf) to eat b) Blue tit population Blue tits decrease as they have less food (holly leaf miner) to eat 2. Predict and explain the effect of removing blue tits on a) Sparrow hawks Sparrowhawks decrease as they have less food (blue tit) to eat b) Woodpeckers Woodpeckers stay the same as they have more insects to eat but less blue tits to eat • As energy flows along a food chain there is a loss of energy at each level • 90% of the energy is lost as heat and movement • Only 10% is converted into stored energy of an animal’s body tissues meat ( muscle) • Only this stored energy is available for the next level Energy transfer CREDIT Food Pyramids Food pyramids are diagrams which give us an idea of how much energy is available at each level in a food chain. There are two types; CREDIT Pyramid of Numbers Pyramid of Biomass A Pyramid of Numbers shows the number of living things at each level in a food chain. A Pyramid of Biomass shows the total mass ( weight) of living material at each level in the food chain. A Pyramid of Biomass is the more accurate way of displaying how much energy is available at each level because it takes into account the fact that sometimes a very large organism, containing lots of energy, may have lots of smaller ones living on it whose combined energy is less. To draw a pyramid you may sometimes be given figures but they are not necessary. You only have to be aware that the greatest mass/numbers will always be at the start of a food chain and least will be at the end. For example : For the food chain lettuce rabbit CREDIT fox The Pyramid of Numbers is; fox least numbers rabbit lettuce greatest numbers For some food chains the pyramid of numbers can look a bit strange and this makes it an inaccurate representation of the available energy. For example, chain; rosebush bird ladybird greenfly rose bush CREDIT For the food greenfly ladybird bird This pyramid looks strange because there is only one large rosebush in the food chain but there are hundreds of tiny greenflies living on the rosebush CREDIT The Pyramid of Biomass for the same food chain would look like this; bird smallest combined mass ladybird greenfly rosebush greatest combined mass This is because the combined mass, and therefore energy, of all the rose bushes in the area is greater than that of the greenfly, which in turn is greater than that of the ladybirds which is greater than that of the birds. This makes the Pyramid of Biomass a more accurate representation of the energy available. • A population is a group of living things of the same type e.g. sparrows, foxes, daisies • The size of a population changes from time to time • How big a population gets depends on the number of births (birth rate) and the number of deaths (death rate) • A population gets bigger if the birth rate is greater than the death rate (A - B) • A population will remain stable if the birth rate equals the death rate (C) • A population gets smaller if the birth rate is less than the death rate (D) Population growth Growth limiting factors • As a population grows its growth usually slows down due to growth limiting factors • There are many ways in which population growth is slowed down • The main limiting factors are • Lack of food – weaker individuals die due to competition • Lack of space – overcrowding makes it easier for disease to spread • Disease- kills weaker animals • Predators- eat lots of them Population Graph • Under ideal conditions a population will grow slowly at first as reproduction is just beginning A • Growth rate rapidly increases due to high BR and low DR (no limiting factors) B • Finally several generations will be alive and all reproducing - the population size rises almost vertically in a population explosion C CREDIT • Competition occurs when organisms have the need for the same resources • Animals compete for resources which are in short supply e.g. food, water, shelter • Any animal that fails to get the minimum requirements will die • Only the best competitors survive Competition Competition between plants • In plant communities, competition is mainly for light • Light • Water • Soil nutrients soil nutrients water Effects of competition • Red squirrels are losing habitats in competition with grey squirrels • Gannets which don’t get a nesting site will not mate • Plants which don’t get enough sunlight will be stunted or yellow Recycling ( Nutrient Cycles ) The ______ bodies and ______ waste products of organisms have important nutrients _______ locked up inside them. These important nutrients include ______ carbon and _______. nitrogen In nature these nutrients are ________. recycled Without recycling these nutrients would not ___ be available to new living members of the community. Recycling involves the _____ decay of dead bodies and waste bacteria products by microscopic decomposer __________ organisms ( _______+ fungi ____ ). Clover – a leguminous plant CREDIT root nodules The recycling of nitrogen The circulation of nitrogen is called the ________ Nitrogen _____. cycle Nitrogen cycle Atmospheric nitrogen Denitrifying Lightning bacteria storms Soil nitrates CREDIT Nitrogen-fixing bacteria (in root nodules) absorbed Plant protein through roots Nitrifying bacteria nitrites eaten Animal protein death death Faeces + dead remains Nitrifying bacteria Ammonium compounds Decomposers (bacteria+fungi) CREDIT Bacteria in the soil require ________ oxygen for __________. respiration In the _______ absence of oxygen, nitrates are ________ used up and not replaced. Also in the absence of oxygen, ___________ Denitrifying ________ bacteria break nitrogen ____ gas which is released into the down soil nitrates to _______ atmosphere __________. Nitrogen can enter the cycle in other ways. Nitrogen fixing ________ bacteria in the root nodules of leguminous ________ ______ plants change atmospheric nitrogen gas into nitrates. CREDIT Also, during ______________ lightning storms the energy generated during a combine forming flash causes nitrogen and oxygen to ________, oxides of nitrogen dissolve in rain water to form ________________which then ________ nitrates ______. An _______ artificial way is to add a chemical _______. fertiliser