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Life On Earth National 5 Biology 2. Biotic and Abiotic factors 2.1 The Effect of Abiotic Factors on the Distribution of Organisms in an Ecosystem 2.2 2.1.1 Measuring Abiotic Factors 2.1.2 Effect of Abiotic Factors on Distribution of Organisms The Effect of Biotic Factors on the Distribution of Organisms in an Ecosystem 2.2.1 Competition 2.2.2 Grazing 2.2.3 Predators and Prey 2.2.4 Parasitism and Disease Learning Intentions By the end of this section you should be able to: describe the difference between abiotic and biotic factors give named examples of abiotic and biotic factors design an investigation to measure the effects of abiotic and biotic factors on the distribution of organisms use sampling equipment to measure abiotic factors in a habitat identify possible sources of error in your investigation and how to minimize them explain the relationship between abiotic and biotic factors and population size, giving named examples Describe the relationship between grazing and biodiversity An organism will only live in a particular habitat if the conditions are suitable for it. These conditions, or factors, are either biotic or abiotic 1 Life On Earth National 5 Biology 2.1 The Effect of Abiotic Factors on the Distribution of Organisms in an Ecosystem Abiotic factors are non-living physical and chemical factors which affect the ability of organisms to survive and reproduce. Some abiotic factors include light intensity, temperature, pH level, availability of water, oxygen/carbon dioxide levels and levels of pollution. Abiotic factors vary in the environment and determine the types and numbers of organisms that exist in that environment. Biotic factors are all the living things that directly or indirectly affect an organism in its environment. This would include competition for resources like food or light between organisms, availability of food, parasitism, disease, and predation. Factors which determine the types and numbers of organisms of a species in an ecosystem are called limiting factors. Abiotic factors often act as limiting factors by restricting the growth of populations in nature. An example of this would include low annual average temperature, common to the Arctic region, which restricts the growth of trees and insects. Biotic factors can also act as limiting factors, for example competition for light and water between trees in a forest can limit the number or type of trees present. Carrying capacity is the maximum number of organisms the resources of an ecosystem can support. The carrying capacity of the ecosystem is limited by a combination of abiotic and biotic factors. 2 Life On Earth National 5 Biology Learning Activity 1 – Show you know! 1. Describe the difference between abiotic and biotic factors, giving a named example of each. 2. Re-organise the information into a table of Abiotic and Biotic factors giving 4 examples of each 3. Why are competition and disease classed as biotic factors? 4. What effect do limiting factors have on the size of a population? 5. How do biotic and abiotic factors act as limiting factors? Extension - Attempt activity 3.1.16 on p249 of National 5 biology book 2.1.1 Measuring Abiotic Factors During the study of an ecosystem the abiotic factors can be measured. Your teacher will demonstrate/discuss some of the techniques that can be used to measure abiotic factors, e.g. light intensity, moisture level, pH, water content. They will also point out what can go wrong with the techniques and how these problems are overcome. Learning Activity 2 – Measuring Light intensity and Moisture Your task is to use the equipment you have been shown to measure and then compare the light intensity and moisture level between at least two different areas (habitats) around the school. 3 Life On Earth National 5 Biology You will record your results in tables like the ones shown below: Measuring Light intensity 1st Reading 2nd Reading 3rd Reading 1. 2. Measuring Moisture Area Moisture level 1st Reading 2nd Reading 3rd Reading Average Moisture Level 1. 2. Once you have your results complete the following tasks: 1. If possible, compare area one and two in terms of both light intensity and moisture level. 2. Explain why it was necessary to take three reading in each area. 3. Explain what errors could have occurred while using the equipment 4. Describe what you did to minimise these errors. 5. Insert and complete the Measuring Abiotic Factors diagram from your pack into your notes. 4 Life On Earth National 5 Biology 2.1.2 - Effect of Abiotic Factors on the Distribution of Organisms Learning Activity 3 – Investigating the effect of abiotic factors of seed germination How do abiotic factors affect germination of seeds? Choose one of the following factors to investigate: Temperature Moisture pH Your teacher will show you some of the equipment available to you. Working with a partner, you need to come up with a plan for this investigation. In the plan you need to identify: your aim the equipment that you will need how you will alter the independent variable how you will measure the dependent variable other variables that you will need to control how you will obtain and record your results Show your plan to your teacher. If the teacher agrees, you can set up the investigation. 5 Life On Earth National 5 Biology Learning Activity 4 – Effect of Light Intensity on Plant Distribution 1. You will carry out a line transect survey to investigate the effect of moisture on the distribution of daisies. Your teacher will demonstrate how to carry out a line transect. You can record your results in a table like this. Sample site Abundance of daisies 1 2 3 4 5 6 7 8 9 10 (out of 25) Moisture 2. Share your results with other groups and work out a class average. 3. Discuss the following questions in pairs: What do the results tell you about the relationship between light intensity and the abundance of daisies? What was the point of sharing the results to make a class average? Apart from light intensity, what other factors could be affecting the abundance of daisies? Learning Activity 5 – Effect of light intensity on the abundance of daisies A group of students carried out transect survey to measure the abundance of daisies in a small clearing in the middle of a wood. They used quadrats and light meters to obtain their results. Study the information in the table below then complete the questions underneath the table. 6 Life On Earth National 5 Biology Abundance of Daisies Sample site Abundance of daisies 1 2 3 4 5 6 7 8 9 10 19 20 18 21 12 8 4 1 0 0 H H H H G F E D C C (out of 25) Light Intensity (A=low H=high) A. Present the information in the table as a two separate bar charts. Once you have drawn one of the bar charts check the success criteria below to judge how good it is. Decide if you need to make any improvements. B. Using the data from your bar charts, describe the relationship between light intensity and the abundance of daisies. C. Predict how many daisies would be found if the light intensity was ‘B’. Explain your answer. D. Suggest a reason why the light intensity decreased between sample site 1 and sample site 10. E. Name at least two variables that would need to be controlled during the investigation to make these results valid. Success Criteria for a Bar Chart All lines must be drawn in pencil with a ruler The labels for the Y (vertical) axis and X (horizontal) axis must match up to the headings in the table, including any units Each scale must have equal integers (i.e. each space on the scale should be worth the same numerical value) The bars should be accurately drawn, i.e. tops of the bars should be straight; bars should be same width; height of each bar should match a value given in the table The bar graph should have a title 7 Life On Earth National 5 Biology 2.2 The effect of Biotic Factors on the Distribution of Organisms in an Ecosystem 2.1.2 - Competition Learning Activity 6 – what do you already know? What sort of things might organisms living in the same habitat compete for? Make a list of as many things as you can. There are two types of competition: Interspecific competition is when individuals of different species compete for similar resources in an ecosystem. Intraspecific competition is when individuals of the same species compete for exactly the same resources in an ecosystem. Which type of competition is more intense? Discuss with your partner. Learning Activity 7: Investigating competition between cress seedlings You will investigate the effect of competition for moisture on the growth of a population of cress seedlings. 100 cress seeds will germinate successfully on 2g of cotton wool soaked with 20ml of cold tap water in a yoghurt carton. Under these conditions there is little or no competition between the seedlings as they develop. If they are left in a propagator for 5 days, they will grow tall and develop healthy green leaves. 8 Life On Earth National 5 Biology Working with a partner, you need to come up with a plan for this investigation. In the plan you need to identify: your aim the equipment that you will need how you will alter the independent variable how you will measure the dependent variable other variables that you will need to control how you will obtain and record your results Show your plan to your teacher. If the teacher agrees, you can set up the investigation. Learning Activity 8 - Research task: Interspecific competition Brown v Rainbow Trout – Rainbow trout from North America have been introduced into British Rivers and are invading the natural habitat of the native brown trout. Use resources available to use to research more about inter-specific competition. The links below will help you find out more about competition between the two species of trout but you can chose other organisms if you wish. Write a short report describing competition between the organisms you have chosen. Include information about the resources they compete for, which of the organisms is most successful and why you think this is. Go to http://www.gov.scot/Topics/marine/marine- environment/species/fish/freshwater/btrout and http://www.gov.scot/Topics/marine/marineenvironment/species/fish/freshwater/rainbow 9 Life On Earth National 5 Biology 2.2.3 Effect of Grazing on Biodiversity Grazing is a biotic factor which affects biodiversity in an ecosystem. Natural grassland normally contains a rich diversity of plant species. Some are especially strong and vigorous while others are much more delicate. Rabbits are relatively unselective grazers eating most types of grassland plants. This maintains a high biodiversity of plant species as the stronger, more vigorous grasses are kept in check. If disease or human activity decreases the number of rabbits from an area of grassland the dominant, more vigorous grasses will be able to grow freely and this will prevent the weaker species surviving and plant biodiversity will be reduced. When rabbits return to the area, they keep the grass closely cropped, keeping the dominant grasses in check, allowing the weaker species to return again, and so increasing biodiversity. However if grazing becomes very intense (overgrazing) the biodiversity of plants may be slightly reduced as the more delicate species can no longer survive. Learning Activity 9 – Data Handling Use the information in the table to draw a line graph to show the effect of grazing pressure. Average number of plant species 10 20 50 20 Grazing Pressure (Number of rabbits per Km2) 100 200 300 400 a. Present the information as a line graph. Refer to the success criteria to help you complete it correctly. 10 Life On Earth National 5 Biology Line Graph Success Criteria All line must be drawn using a pencil and a ruler A suitable scale must be used for the Y- axis (vertical) and the x-axis (horizontal) The scale for each axis must have regular integers (i.e. spaces between the numbers should have equal numerical values) The scale should have an origin (i.e. start at zero) Each axis should have a label, including units, that matches the headings in the table All points must be plotted accurately The graph should have an appropriate title b. Using the information from the passage above and the data from your graph, compare the effect of increasing grazing pressure with the average number of plant species found. If two marks were available in an exam for question b, how many marks is your answer to question b worth? How could you improve your answer? Share your answer with the people at your table until you think you have come up with the perfect answer. Show your answer to your teacher and ask for his/her feedback. 11 Life On Earth National 5 Biology 2.2.3 - Predator Prey Interactions Predation is a biotic factor which affects biodiversity in an ecosystem. The graph below shows the typical relationship between predator and prey populations. Learning Activity 10 – Data Interpretation Collect a copy of the graph and paste it into your notes. What do you notice when you look at the graph? Discuss this with your partner. Make a list of as many observations as you can. Share these with the people at your table. Learning Activity 11 – Data Interpretation The graph below shows the interaction between the population of Moose and the population Wolves. Collect a copy of the graph and complete the following questions in full sentences. 12 Life On Earth National 5 Biology 1. 2. 3. 4. 5. What was the Moose population in 1970? What was the Moose population in 1980? What was the Wolf population in 1970? What was the Wolf population in 1980? Suggest a reason for the decline in the Moose population between 1973 and 1982. You should use the evidence from the graph to support your answer. 6. Using the data from the graph, describe what happens to the Wolf population between 1980 and 1982. Suggest a possible reason for this. 7. Predict what would have happened to the size of the Wolf population after 1995. 8. Explain what the graph tells us about the relationship between the size of a predator population and the size of a prey population. 13 Formatted: Font: Comic Sans MS, 12 pt Life On Earth National 5 Biology 2.2.4 - Parasites and Parasitism A parasite is an organism that lives off of another organism (called the host organism). Parasitism is a biotic factor that describes the relationship between the parasite and its host organism. The picture opposite shows a honey bee larva that has been infected by a parasite called Varroa Destructor (Varroa mite). Watch the film below to get some perspective on this issue. Consider the questions below while you watch the film. http://www.abc.net.au/7.30/content/2013/s3911559.htm The key questions: How does the varroa mite affect the honey bee? Why is the varroa mite such a problem for honey bees? What impact could this have on humans? Learning Activity 12 – Parasites Your task is to use the internet or other resources to research the effect of the varroa mite on the honey bee population. Your report should be one or two sides of A4 at most. 14 Life On Earth National 5 Biology It must include five of the following pieces of information: A description of what a varroa mite is A description of how the varroa mite affects the honey bee An explanation of why the varroa mite is such a problem for honey bees Some data to show the effect it has on the size of the honey bee population A description of the effect this is having on the population of honey bees An explanation of the effect that this could have on humans An explanation of the effect that this could have on biodiversity A description of what can be done by humans to help protect the honey bee from the varroa mite Choice Extension Task 1 2 3 4 5 You must complete at least two of these activities Design a board game based on competition. Produce a collage of pictures demonstrating different types of competition in nature. Produce a poster on a particular habitat – Where in the world is it? What sort of animals or plants live there? What abiotic and biotic factors affect them? Find out a parasite that affects humans. Produce an information poster or leaflet about it Produce a helpful checklist or advice to help people to draw graphs Completed 15 Life On Earth National 5 Biology Self Evaluation - How well did I do? How well can you describe the key words/phrases below? Take turns at explaining what they mean to the person sitting next to you, and then let them explain them to you. Abiotic, biotic, intense, overgrazing, abundance, parasite, competition, limiting factor, habitat, biodiversity, population, ecosystem, source of error, independent variable, dependent variable, interspecific, intraspecific Use the success criteria sheet to reflect on and evaluate your learning from this section. Think carefully and answer the following questions: 1. What skills have you developed over the past few lessons? How do you know and how could you prove it to someone? 2. What areas have you found difficult? What strategies are you going to use to overcome these problems? Discuss this with your teacher and set yourself a learning target – this is what you will do to improve your knowledge and skills. Update Didbook with a comment about what you have done well, what you want to improve at doing and how you will do this. 16