--- title: "Quick check: abiotic factors and food web limits" subtitle: "Year 7 Biology · Food webs and ecosystems · Lesson 8" --- # Quick check: abiotic factors and food web limits **Name:** {{field-24}} **Date:** {{field-15}} **Class:** {{field-15}} > **Key question:** A dry year changes the grass. What happens next, and how sure can a food web diagram be? :::teacher-note **In one sentence:** A self-test on abiotic factors and population effects, and the limitations of food web models (AC9S7U02, nodes 3 and 5, taught in class). **Students should be able to say:** I can sort abiotic and biotic factors. I can predict how a change in an abiotic factor spreads through a food web. I can say what a food web model leaves out and how that limits a prediction. **Width:** the unmarked parts are the floor every student does (Engage, Explore, Explain, Evaluate). Typical and Wider sections add contexts, not difficulty. Students work in the online tutorial alongside this sheet. ::: ## Abiotic factors :::keep-together ### Abiotic or biotic? **Is it abiotic (non-living) or biotic (living)?** Groups: Abiotic, Biotic - Sunlight: {{field-15}} - Rainfall: {{field-15}} - Soil pH: {{field-15}} - Temperature: {{field-15}} - Grass: {{field-15}} - Bacteria in the soil: {{field-15}} - A hawk: {{field-15}} ::: :::teacher-note **Answer:** Sunlight → Abiotic; Rainfall → Abiotic; Soil pH → Abiotic; Temperature → Abiotic; Grass → Biotic; Bacteria in the soil → Biotic; A hawk → Biotic ::: :::keep-together ### A dry year **In a web, grass is eaten by grasshoppers, which are eaten by lizards. A drought cuts grass growth. What happens to the grasshoppers?** ☐ They increase, because the grass is drier ☐ They turn into lizards ☐ Nothing, because grasshoppers are not plants ☐ They decrease, because they have less food ::: :::teacher-note **Answer:** They decrease, because they have less food A change in an abiotic factor (water) hits the producer first, then the animals that depend on it. ::: :::keep-together ### Who else? **Besides the grasshoppers, which population is also affected by the drought?** ☐ The sun ☐ The lizards, because their food supply falls ☐ No other population ☐ Only the grass ::: :::teacher-note **Answer:** The lizards, because their food supply falls The effect cascades up the web: fewer grasshoppers means less food for the lizards, and then for whatever eats them. ::: :::keep-together ### Abiotic means **What is an abiotic factor?** ☐ Anything that harms living things ☐ A living thing that affects other living things ☐ A non-living part of the environment, such as temperature, water or sunlight ☐ An animal that eats only plants ::: :::teacher-note **Answer:** A non-living part of the environment, such as temperature, water or sunlight Abiotic means non-living: physical and chemical conditions such as temperature, water, light and soil. ::: ## What a food web leaves out :::keep-together ### What it shows **Does a food web diagram show this?** Groups: Shows it, Does not show it - Who eats whom: {{field-15}} - The direction energy flows: {{field-15}} - How many of each organism there are: {{field-15}} - What a drought does: {{field-15}} - How the web changes with the seasons: {{field-15}} ::: :::teacher-note **Answer:** Who eats whom → Shows it; The direction energy flows → Shows it; How many of each organism there are → Does not show it; What a drought does → Does not show it; How the web changes with the seasons → Does not show it ::: :::keep-together ### A weak prediction **A web shows a hawk eats lizards. Someone predicts that if lizards disappear the hawks will die out. Why might that be wrong?** ☐ It is right: if lizards disappear, the hawks must die out ☐ Hawks may also eat other animals that the diagram leaves out, so they could switch food ☐ Food webs can't be used to make predictions ☐ Hawks would switch to eating grass ::: :::teacher-note **Answer:** Hawks may also eat other animals that the diagram leaves out, so they could switch food Real animals often eat several foods, and a diagram simplifies. A prediction is only as good as the web it comes from. ::: :::keep-together ### Model limits **Which is a limitation of a food web model?** ☐ It shows only some organisms and links, so predictions are less certain ☐ It shows how many organisms there are ☐ It only works for plants ☐ It is always completely accurate ::: :::teacher-note **Answer:** It shows only some organisms and links, so predictions are less certain A model simplifies. Knowing what it leaves out tells you how far to trust its predictions. ::: ## Exit ticket :::keep-together **Give one abiotic factor and say how changing it would affect one population.** {{lines-3}} ::: :::teacher-note **Answer:** For example less rainfall means less grass, so fewer grasshoppers. Any reasoned chain is fine. :::