--- marp: true theme: default html: true --- # Quick check: abiotic factors and food web limits Year 7 Biology · Food webs and ecosystems --- ## Today **We are learning to** a few quick questions on abiotic factors, how a change spreads through a food web, and what food web models leave out. Taught in class; use this to check yourself. - 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. --- ## Why it matters > A dry year changes the grass. What happens next, and how sure can a food web diagram be? --- ✅ Check ## Abiotic or biotic? **Is it abiotic (non-living) or biotic (living)?** Groups: Abiotic · Biotic Sunlight · Rainfall · Soil pH · Temperature · Grass · Bacteria in the soil · A hawk * Answer: Sunlight → Abiotic; Rainfall → Abiotic; Soil pH → Abiotic; Temperature → Abiotic; Grass → Biotic; Bacteria in the soil → Biotic; A hawk → Biotic --- ✅ Check ## 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 * Answer: They decrease, because they have less food --- ✅ Check ## 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 * Answer: The lizards, because their food supply falls --- ✅ Check ## 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 * Answer: A non-living part of the environment, such as temperature, water or sunlight --- ✅ Check ## What it shows **Does a food web diagram show this?** Groups: Shows it · Does not show it Who eats whom · The direction energy flows · How many of each organism there are · What a drought does · How the web changes with the seasons * 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 --- ✅ Check ## 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 * Answer: Hawks may also eat other animals that the diagram leaves out, so they could switch food --- ✅ Check ## 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 * Answer: It shows only some organisms and links, so predictions are less certain --- ✅ Check ## Exit ticket **Give one abiotic factor and say how changing it would affect one population.** * For example less rainfall means less grass, so fewer grasshoppers. Any reasoned chain is fine.