This quiz will check your knowledge of the content covered in the cycles lesson and also help you to revise previous ecology content.

The movement of water through a plant is called what?

Which process is not part of the carbon cycle?

Revision: which is the best description of a mean average?

Revision: what is a quadrat?

What helps in the decay of dead organisms?

Cycles

﻿Hello, I'm Dr. Clapp, and I'd like to welcome you to another ecology lesson. All you'll need for the lesson today is a pen and a piece of paper. If you could just take a moment to carry away any distractions that are around you, and if possible find yourself a quiet place to work where you won't be disturbed during our lesson. Right, if you're ready let's get started. In this lesson we're going to look at the process of decay and think about why it's important. We're going to look at the conditions that are required for decay to happen. And then some uses that we make of decay to help us out, basically. So we looked at cycles in our previous lesson and we discussed that they are just a series of processes that take a starting material and change it into lots of different things and then eventually it gets back to where it began. Now, cycles aren't just for carbon or water that we looked at, but they're also for nutrients. So living plants and animal matter, we started off with that position. We would, at some point end up with dead plant and animal matter. Decomposers would break down the matter. This would lead to nutrients being stored in the soil, and then living plants and animals would use those nutrients and the cycle would continue to go around and around. And this is important because there are limited resources on earth and that includes nutrients. So there are limited numbers of nutrients on earth. And so the cycle needs to go round and round, otherwise we would not be able to support life. So to summarise that, there are only a set amount of nutrients on earth. When organisms die, their bodies decay and release nutrients back into the ground. Waste products also undergo decay and they would release nutrients into the ground as well. And then these nutrients can be used for new growth by plants. Plants would then be eaten by animals and the cycle would continue around and around. So decay itself, decay is when complex materials break down into more simple molecules which can then be reused. So it's basically taking big molecules and breaking them down into smaller molecules and then we're using them again. So here's our first set of quick-fire questions for today. No need to write anything down. Just tell me the answer when you know it. Why didn't nutrients need to be cycled? Hopefully you got, because there are limited amounts of them on earth. What is decay? Excellent, if you've got it. It's the breakdown of complex materials into more simple molecules. Really well done, 'cause it's important to know that distinction we're taking the more complicated things and we're breaking them down into the simpler things that can then be reused, really good work. So we're going to go through the decay process step by step. I'm going to put some pictures up and then we're going to just, put some simple explanations to go along with them. So, the first step in the decay process might involve organisms like worms, or woodlice, or maybe maggots. And these organisms are called detrivores. So the detrivores will come along and they will eat the dead material, the plant or animal matter. The second step in the decay process, involves a fungi or bacteria microorganisms. These are called decomposers and they digest everything. So they would break down the dead animal material, or plant material, or they could also break down waste products. The next step, decomposers and the detrivores respires and they release waste products as they're respiring. So they would release water, carbon dioxide, nutrients into the soil, and they also release energy and so the temperature would increase. And then finally, this little symbol back here again, the materials are reused and the cycle begins again. So all of the things that the detritivores and decomposers released into the soil would be used by plants. Plants would grow, animals would eat plants, plants and animals would die, nutrients back in the soil, and around and around we go. So we're going to go through that again, but this time I'm going to to pause for a while and let you fill in the information to go with the pictures. Just verbally again, nothing to write down at this stage. So what was going on in this first step here? So here we've got our detrivores eating the dead material. What was the next step? They were all decomposers digesting everything, remember that decomposers are bacteria or fungi. The third step, excellent, it was the decomposers and detrivores respiring and releasing their waste products. And then the final step, we should be used to this symbol now. Great work, it's the materials being reused and the cycle beginning again. Right, So let's do a little bit of independent practise based on that now. I would like you to describe the process of decay. And I have put some keywords here to help you out, things that you want to include in your answer. So, please pause the lesson here now, and then resume and come back when you are ready for some answers. Okay, and here are our answers. If you're not ready just hit pause again now. So detrivores such as worms and woodlice start the process of decay by feeding on the dead matter. That was step one. Step two, decomposers such as bacteria and fungi will also feed on the dead matter or the waste products. Step three, both the detrivores and decomposers will use some of the nutrients from the dead matter but we'll also respire and release waste products into the surroundings. And then finally, the waste products can be used by plants for growth and then the cycle will begin again. So ticks, if you've got those correct or if you missed out any information stages just add it into your work now. So decay is a process that happens but it happens best in certain conditions. And that's what we're going to consider now. So the best or most ideal conditions for decay are warm area. damp, so moisture, and a good oxygen supply. And we'll look at why each of those are important. So why does it need to be warm? Warm temperatures increase the rates of reactions and decay is a reaction, so this will speed up decay. But there is something important that we need to remember here. High temperatures will denature enzymes stopping the reactions from occurring at all. So basically, what we're saying is, and that's why we've used the word warm rather than hot. If it's warm then the rates of decay will increase, but if it gets too hot, if the temperature gets too high, decay will stop completely because the enzymes will denature. And we're just going to go through now what that means as a quick reminder, you would have come across it in other topics, but just to make sure. So if we imagine that this little diagram here is an enzyme. Is a protein molecule and it has a very specific shape in the side of it. There you can see the two kind of pointy bits, that is active sites. and active sites are specific. So their shape is specific for the substrates that they work on. So they matchup perfectly. and sometimes you might hear this described as a lock and key mechanism because they fit together like a key fits in a lock. And if this works, if the substrate combined into the active sites then the enzyme will able to work and the reaction will happen. Now, if our temperatures get too hot, what happens is the enzyme denatures. And that means it starts to unwind it's protein structure and its shaped changes. So the shape of the active sites becomes different in this denatured enzyme here. The substrate hasn't changed at all but if that substrate comes along now, it's not going to be able to fit into the active site anymore. And so the enzyme will not be able to carry out its job. It will not be able to work on that particular reaction. And so the reaction won't happen. So just to summarise, active sites have a specific shape. If an enzyme is heated too much it denatures. The shape of the active site changes. This means the substrate can no longer bind and the reaction won't happen. So that's why we say we want warm conditions for decay rather than hot conditions. Because if it's too hot the enzymes will denature and decay won't be able to happen. Okay. The second condition that I had on my list was that it needed to be damp. When it is damp the matter will start to dissolve into the water which makes it easier for the decomposers to digest. So if we've got dampness in the air or dampness around where the dead material is, it will start to dissolve. And that makes it easier for the decomposers to come along and digest the rest of the matter, basically, so it helps to speed up the process. And the last thing that was on my list for the ideal conditions for decay was a good oxygen supply. The detrivores and decomposers need to respire in order to stay alive and oxygen is needed for respiration. All living things need to respire, oxygen is needed for respiration. Detrivores and decomposers are still living things. So if there's not enough oxygen they would not be able to respire. So let's try a little bit more quick-fire questions before we move on to some more independent practise. So nothing to write down just tell me out loud as soon as you know the answer. What are the three conditions required for decay? Excellent, if you got warm, damp and a good oxygen supply. What does it mean if an enzyme is denatured? Good work, it means the shape of the active site has changed and it can no longer work. Why is a good oxygen supply important for decay? The organisms involved need it for respiration. Excellent, if you remembered about respiration there. Why is a warm temperature best for decay? Because reactions happen faster in warmer temperatures and decay is just a reaction. So let's summarise that one more time for a bit more independent practise. Decay happens fastest when it's warmer, but not so warm that the enzymes get denatured, so they balance. The rate of decay is also affected by the presence or absence of water and oxygen. So we want some water and we want some oxygen. Oxygen is needed by the detrivores and microbes for respiration And decay is important because it releases nutrients back into the environment where they can be used by other organisms for growth. Basically, because they feed this cycle and we need the nutrients to keep going round around in the cycle because there are only limited numbers of them. So time for a bit more independent practise, I've got three questions here that I want you to answer. So, please pause the lesson here now, and then when you're ready come back to me for some answers. Okay, and here are our answers. So if you're not ready hit pause again. So the three conditions required for decaying were warm temperatures, damp and good oxygen supply so here we've a tick if you've got all of those. Explain why if it gets too hot the rate of decay will slow down? If it gets too hot the enzymes will begin to denature and then the substrates wouldn't be able to bind to the active sites, so the reactions will stop and decay will slow down. Excellent if you've got that. And then our last question, explain why if oxygen levels get low the rates the decay will slow down? If oxygen levels get low then the organisms involved in the decay process won't be able to respire and will die. So the rates of decay will slow down. Remember to add in anything that you didn't quite get the first time round if you need to. Now there are some examples sometimes when decay doesn't happen. And this is a picture of one of the best preserved woolly mammoth. So from a long period of time ago and as you can see obviously it doesn't look like a live woolly mammoth, it has undergone some decay but really not very much considering how long ago it would have lived and died. And that's because sometimes the conditions for decay aren't right and if the conditions aren't right then decay won't happen. So what is thought is that when this woolly mammoth died, it probably got buried very quickly under a lot of ice and the temperatures were really really cold and therefore it has been preserved really well, decay didn't happen. We also see preservation happening in places where oxygen levels are low because the microbes and the detrivores aren't able to do their job. And also sometimes when the temperatures are really hot as we mentioned earlier. So like we said, decay has these ideal conditions and if the ideal conditions aren't met then decay might not happen in the way we expect or might not happen very much at all in the case of this woolly mammoth. So we do have some uses of decay, kind of everyday uses for some people. And one of those is compost. So you might have in your back garden a compost bin, or just a pile of compost. So you might have food waste from the house, plant material that you might put on the bin, or maybe when you cut the lawn, or do any gardening, those waste bits of plants they might go into the compost bin. And compost bins are designed in a particular way to make the decay process happen as best as it can. And that's what's happening in a compost bin that material that's in there is decaying. So the features of a compost bin would be that it would be open at the bottom. That's to encourage the detrivores in because we need those worms and woodlice, and maybe maggots, to start the decay process. It will have a loose fitting lid. So it's got a lid on the top, you can see in the picture, but it wouldn't be sealed, it would be loose fitting and it would have some air holes probably around it sides somewhere, that's to allow airflow in, the lid and the air holes, to allow airflow in 'cause remember we need oxygen for decay to happen efficiently. And it would be dark-colored, probably normally they're blacks or dark greens. And that's because those colours tend to absorb more energy and so help to keep the bin warm. So time for a bit more quick-fire. Let's see what we can remember. Which feature of a compost bin helps with maintaining a good oxygen supply? Is it a loose lid or a dark colour? That's right, it's a loose lid. Well done, if you've got that one. Which feature of a compost bin then helps with keeping warm? Is it a dark colour or air holes? Yep, that's right, it's a dark colour because that absorbs the energy more. Which feature of a compost bin encourages detrivores to enter? Is it a dark colour or an open bottom? Yep, an open bottom, so they can quite literally crawl in. So the final use of decay that I want to talk about right now is biogas. If oxygen levels are allowed to drop then anaerobic respiration will take place. The type of respiration we've been talking about so far has been aerobic respiration, it has used oxygen. Respiration can happen without oxygen and that's anaerobic respiration. But the products are slightly different. And in this case biogas is produced. And biogas can be used as a fuel so it's useful. And in the image here is a small kind of biogas plant. So one of the containers would have the decay process happening inside it. And then the other one would be used to collect the biogas and the biogas could then be collected and sold to people that wanted to use it for fuel. Right, so we're going to finish with having to go at an exam question and I'm going to go through the first one and then there's some for you to have a go at yourself independently. So, the production of landfill gas is affected by temperature. The rate of gas production is greatest between 35 degrees Celsius and 50 degrees Celsius. Explain why landfill gas production is reduced above and below these temperatures? So if we look at that question, there's some important information there. There's an explain, so it's not just state. We need to say why this has happened and it's easy reduced above and below these temperatures. So we need to do both. So it's two marks. So without even trying to answer the question by looking at this, I can see that I'm probably going to get myself one mark. If I talk about why it's reduced above and the second mark for why it's reduced below. So let's have a look at how I might formulate this answer. I would say that below these temperatures it would be too cold and respiration would be very slow. So decay would not be happening. Above these temperatures the enzymes would denature and stop working. So I've covered both of those points. What happens below and what happens above. And I've said why enzymes would denature, for example, or respiration would be slow. So I've given my explanation. Right, so now it's time for you to have a go at some independent practise. After heavy rain, a rubbish dump can become water-logged. The production of landfill gas will increase over the following few weeks, so after it's become water-logged, suggest why? And then another question, when bristlecone pine trees die the wood does not rot. The wood is full of a thick sap called resin. This means the wood does not easily absorb oxygen or water. Use this information to help explain why the wood does not rot? So there's two questions there. You might need to flick back to the previous slide in the video to be able to remind yourself and answer that question but I'd like you to please pause the lesson here now, have a go at both of those questions and then come back when you are ready for some answers. Okay, and here are the answers to the first section. So we needed to suggest why? If we'd said lots of water would mean less oxygen could get in, that would give us one mark. And then we would need to take that further by saying, this would lead to anaerobic conditions for respiration. So the gas would be produced. So excellent, if you've got both of those, if you only got one, I'll do the other one now. And then the other question was about the tree and we needed to use the information to explain why the word does not rot. So for one mark we want to say that microorganisms need oxygen for respiration. And no oxygen means that organisms cannot survive and carry out decay processes, because it said in the question remember, that the resin meant that the wood could not absorb the water or the oxygen. So excellent work if you've got both of those correct. Right, so we reached the end of our lesson for now and I just want to do a quick summary. So we introduced the process of decay and we talked about why was important. The fact that nutrients are limited and we need to cycle them around, so that we can reuse them for new growth. We identified the three conditions for decay, the ideal conditions. So it needs to be warm not hot, moist and have a good oxygen supply. And then we've looked at two uses of decay, composting and producing biogas. Right, so as always the last thing I need you to do please, is to complete the exit quiz for today's lesson that will help you to check your understanding of the content that we've covered. I'd like to say thank you for your attention and for your efforts during the lesson. And I look forward to seeing you again soon, for another ecology lesson. Bye for now.

This quiz will check your knowledge of the content covered in the decay lesson.

Why is decay a useful process?

Select the two main types of organisms involved in decay.

Which condition from the list will help decay to occur?

Why do high temperatures slow down decay?

True or false: Anaerobic means with oxygen

Select three key features of a compost bin.

Decay

Name the causes of decay and describe conditions that can speed it up

Describe and explain the effect of temperature on the rate of decay

Interpret secondary data to describe and explain the effect of oxygen on the rate of decay

This lesson looks at the process of decay and the conditions which speed it up and applies this knowledge to the uses of decay.

Biology

Y10 Biology

Key Stage 4

Year 10

Ecology

UNIT

Communities

Biotic and Abiotic factors

Adaptations

Maths skills

Sampling required practical (Part 1)

Sampling required practical (Part 2)

Biomass

Food security and farming

Decay required practical

Global warming

Biodiversity

Review (Part 1)

Review (Part 2)

Review (Part 3)

Case Study: Dr Beth Penrose

What type of organism is always found in trophic level 1?

Revision: what do the arrows in a food chain show us?

What is described as the mass of living organisms?

In a food chain 200 kg of wheat is fed on by 18 kg of mice which in turn are eaten by 1kg of hawk. What is the percentage energy transferred from the first trophic level to the third?

What is the best description of food security?

Select two reasons why some populations might have poor food security.

Revision: Select two reasons why biomass is lost between the trophic levels of a food chain.

What is sustainable fishing?

Revision: Which is the example of a behavioural adaptation?

What is the following statement describing? A situation where numbers of living organisms remain roughly constant over time.

Revision: what do all food chains and webs start with?

What is the definition of a biotic factor?

What effect would a constantly low temperature have on a population of plants?

What is a structural adaptation?

Why do desert plants tend to have spines rather than large leaves?

Revision: what is an apex predator?

Which is an effect of global warming?

Revision: select the three ideal conditions for decay.

In the following food chain which organism is the apex predator? Mahogany tree → caterpillar → song bird → hawk

Which resources do plants compete for?

How do we reduce bias in a sampling experiment?

What is a functional adaptation?

Select three things that can be done to help maintain biodiversity.

An animal has a surface area of 120,000 cm² and a volume of 40,000 cm³. What is the surface area : volume ratio?

What is the area of a quadrat with a side length of 0.4 m?

A field has an area of 765 m². A 0.5 m x 0.5 m quadrat was placed 8 times and the number of buttercups counted as follows 22, 10, 6, 8, 0, 11, 9, 17. Estimate the population of buttercups in the field.

Lesson overview:Decay

Ecology: