Download Food Webs and Ecological Pyramids Ecological Niches

SNC1DA 2.5: Food Webs and Ecological Pyramids Ecological Niches: • Every species occupies a unique ecological niche • Ecological Niche : _____________________________________________________________________________________
_____________________________________________________________________________________ Types of Consumers Feeding Role Definition Herbivore Carnivore Omnivore Scavenger Decomposer Food Chains and Food Webs Feeding relationship between organisms can be organized by food chains, trophic levels, and food webs (in order from least to most informative) Food Chains: -­‐ Describes simple relationships; ___________________________
___________________________ -­‐ Starts with _________________ -­‐ Arrows show the ___________________________ throughout the chain Trophic levels: -­‐ Describes an organism’s ___________________________
along the food chain -­‐ Starts with a producer Food Web: -­‐ More _________________; describes the interactions of __________________ feeding on many species. -­‐ The number of interactions relates to the _________________________ of a species -­‐ More stable SNC1DA Food Chains: Feeding relationships between species can be represented using food chains. • In a food chain, only about __________________________________ is passed along from _____________________________ to the next (the available energy is divided by 10 at each step in the food chain). • Most of the energy is lost to the environment as ______________________________. Example: If the pine cones in an ecosystem contain 450 000 kJ of energy, how much of this energy is available to the red squirrel? The weasel? The goshawk? Food Webs: • A food web is a more accurate, but still incomplete, way to illustrate feeding relationships. • Complex food webs are usually more stable than simple food webs, because species do not depend on just one source of food. Trophic Levels: • All organisms continually __________________________ energy to their environment, energy is continuously _______________ from all levels of the food chain. • The trophic level describes the________________position of an organism along a food chain or web. • Species can be divided into trophic levels depending on ____________________________________. Ecological Pyramids Ecological pyramids display the relationships between trophic levels in an ecosystem. There are three different types of ecological pyramids: SNC1DA 1. Pyramid of Energy: •
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An energy pyramid represents the amount of energy available at each level. The amount of energy _________________________ at each level because some energy is used by the organisms, and some energy is lost to the environment. Only about 10 % of the energy taken in by individuals at one trophic level is passed on to individuals at the next level. 2. Numbers Pyramid: A numbers pyramid illustrates the relative numbers of organisms at each level. 3. Biomass Pyramid: A _________________________ pyramid illustrates the total mass of all individuals at each level. • Unlike energy pyramids, pyramids of numbers or biomass do not always ____________________ in size from _________________ to____________________levels. Pyramid of Numbers: Approximate number of species in a given ecosystem Pyramid of Biomass: The total dry mass (water has been removed) of all organisms in a given trophic level These pyramids do not always go from large to small – for example, the # of plant-­‐feeding bugs in the second level will outnumber the # of trees in the first level: Pyramid of Energy: Illustrates energy loss and transfer between trophic levels -­‐ The size of the pyramid represents the amount of energy available at that trophic level. -­‐ Only 10 % of energy taken in by individuals at one trophic level is passed onto individuals at the next level. -­‐ Energy is used up in biological processes (growth, reproduction, thermal energy) -­‐ Always decrease in size from lower to higher levels SNC1DA SNC 1D 2.5 Food Webs and Ecological Pyramids Ecological Niches • Every species occupies a unique ecological niche • Niche : the function a species serves in its ecosystem, including what it eats, what eats it, and how it behaves Types of Consumers Feeding Role Definition Herbivore Animal that eats plants or other producers Carnivore Animal that eats other animals Omnivore Animal that eats both plants and animals Scavenger Animal that feeds on the remains of another organism Food Chains and Food Webs Feeding relationship between organisms can be organized by food chains, trophic levels, and food webs (in order from least to most informative) Food Chains: Describes simple relationships; who eats whom within an ecosystem Starts with a producer Trophic levels: Describes an organisms position along the food chain Starts with a producer Food Web: More complex; describes the interactions of consumers feeding on many species. The number of interactions relates to the vulnerability of a species •
Food Webs are the best tool for understanding what may happen if a species is removed from an ecosystem SNC1DA •
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Energy is continuously being lost to the environment by all living things Higher tropic levels always have less energy available to them Ecological Pyramids Ecological pyramids display the relationships between trophic levels in an ecosystem. There are three different types of ecological pyramids: Pyramid of Numbers: Pyramid of biomass: Pyramid of Energy: Approximate number of species The total dry mass (water has Illustrates energy loss and in a given ecosystem been removed) of all organisms transfer between trophic levels in a given trophic level -­‐ The size of the pyramid represents the amount of energy available at that trophic level. -­‐ Only 10 % of energy taken in by individuals at one trophic level is passed onto individuals at the next level. -­‐ Energy is used up in biological processes (growth, reproduction, thermal energy) -­‐ Always decrease in size from These pyramids do not always go lower to higher levels from large to small – for example, the # of plant-­‐feeding bugs in the second level will outnumber the # of trees in the first level: • The different types are often presented together in a single diagram • Displays the relationships of energy lost and transferred between the different trophic levels in an ecosystem. Ecological Pyramids Summarized: •
Species at the highest trophic level have less energy available to them than the species near the bottom o It’s harder for the fox to find the rabbit, than the rabbit to find some grass. SNC1DA •
Therefore, organisms that feed at lower trophic levels (herbivores) have much more energy and biomass available to them when compared to higher level (carnivores). o Changes at the lower trophic level can have a profound impact on the entire ecosystem. 2.5 Homework 1. What is meant by the term ecological niche? Describe the ecological niche of humans and three other species. 2. Explain the difference between a food web and a food chain. 3. Describe some impacts of adding or removing species from an ecosystem. 4. As you go up one trophic level to the next, the amount of energy decreases. Explain where the energy has gone. 5. What trophic levels are occupied by carnivores? Provide some examples. 6. Bison, zebra and kangaroos are three large mammals. Explain why they have similar ecological niches but cannot be shown in the same food web. SNC1DA 7. a. How would the food web below, change if the red fox were killed off by rabies? b. What species would benefit? c. What species might decline? red fox hawk rabbit grasses mouse squirrel berries tree seeds