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4.1 Species, Communities and Ecosystems Essential idea: The continued survival of living organisms including humans depends on sustainable communities. Understandings: • Species are groups of organisms that can potentially interbreed to produce fertile offspring. • Members of a species may be reproductively isolated in separate populations. • Species have either an autotrophic or heterotrophic method of nutrition (a few species have both methods). • Consumers are heterotrophs that feed on living organisms by ingestion. • Detritivores are heterotrophs that obtain organic nutrients from detritus by internal digestion. • Saprotrophs are heterotrophs that obtain organic nutrients from dead organisms by external digestion. • A community is formed by populations of different species living together and interacting with each other. • A community forms an ecosystem by its interactions with the abiotic environment. • Autotrophs obtain inorganic nutrients from the abiotic environment. • The supply of inorganic nutrients is maintained by nutrient cycling. • Ecosystems have the potential to be sustainable over long periods of time. Applications and Skills: • Skill: Classifying species as autotrophs, consumers, detritivores or saprotrophs from a knowledge of their mode of nutrition. • Skill: Setting up sealed mesocosms to try to establish sustainability. (Practical 5) • Skill: Testing for association between two species using the chi-squared test with data obtained by quadrat sampling. • Skill: Recognizing and interpreting statistical significance. Key Words for the topic can be found here: https://quizlet.com/6396273/ecology-definitionsflash-cards/ ● ● ● Unscramble each of the clue words. Copy the letters in the numbered cells to other cells with the same number to find a quote on this topic Now match the clue words to the definitions below: Ecological Key Terms _______________ The study of relationships between living organisms and between organisms and their environment _______________ The environment in which a species normally lives or the location of a living organism _______________ A community and its abiotic (non-living) environment ______________ A group of populations living and interacting with each other in an area _______________ A group of organisms of the same species who live in the same area at the same time _______________ A group of organisms that can interbreed and produce fertile, viable offspring _______________ The role and space that an organism occupies in a given ecosystem Feeding Methods _______________ An organism that lives on or in non-living organic matter, secreting digestive enzymes into it and absorbing the products of digestion _______________ An organism that ingests non-living organic matter _______________ An organism that obtains organic molecules from other organisms (heterotrophs are consumers) _______________ An organism that synthesises its organic molecules from simple inorganic substances (e.g. CO2 and nitrates) (autotrophs are producers) _______________ killed An organism that ingests other organic matter that is living or recently Complete the tree below with definitions and examples of each type of feeding strategy. Distinguish between the feeding strategies at each level of the diagram. Food chains represent the flow of energy and nutrients in a series of feeding relationships. Give one example of a marine food chain (min. 4 organisms) Give one example of a terrestrial food chain (min. 4 organisms) Give one other example of a food chain (min. 4 organisms) Describe what is meant by a food web. The food web below shows some coral reef feeding relationships; Identify species in the following trophic levels: i. Producers ii. Primary consumers iii. Secondary consumers “Energy flows through an ecosystem, nutrients are recycled.” Explain this statement with the aid of a flow chart. Include the roles of saprotrophic bacteria and fungi. Abiotic and Biotic Factors Watch the video here:https://www.youtube.com/watch?v=woSO0D94VGA Which of the following factors affects the distribution of plants and animals? Factor Plants Animals Temperature Soil pH Breeding sites Salinity Water Mineral nutrients Food supply Territory Light How can we measure the distribution of plants and animals? Describe how each of the following is used: Quadrat Random sampling Skill: Testing for association between two species using the chi-squared test with data obtained by quadrat sampling. Go to this website and select Site A http://www.saps.org.uk/secondary/teaching-resources/768-ecology-practical-abundancediversity-and-random-sampling We are investigating if there is an association between these two species: If there is an association, we would expect them to appear in the same places. Record the number of quadrats that the species appear in using the table below: Lousewort No Lousewort Meadow buttercup No Meadow buttercup Total The null hypothesis (Ho) is that there is no association between the two species Total First calculate expected values: expected values = row total x column total/grand total Add them to the table: Lousewort Observed Expected No Lousewort Observed Total Expected Meadow buttercup No Meadow buttercup Total Now calculate chi squared using this formula: Where o = observed and e = expected Compare the chi squared value you calculated with the critical value in the table for the correct degrees of freedom, calculated as follows: Degrees of freedom = columns of observed value - 1) x (columns of observed value - 1 In this case (2-1) x (2-1) = 1 For our experiment we use probability p = 0.05 and 1 degree of freedom , so the critical value is 3.84 There is no rule about this but with fieldwork data most people reckon that 5% significance is an adequate level of acceptance or rejection of the null hypothesis. Remember this means that you would expect to be correct in accepting or rejecting your null hypothesis 95% of the time, 5% of the time you might get a different result due to chance. Is there an association between the two species? Use the chi squared value you calculated to explain how you know this.