hey everybody it's mr smeeds and today we'll be covering topics 1.9 and 1.10 which are trophic levels and the 10 rule so we'll be talking about how energy flows through ecosystems and how the available energy decreases as we move up the trophic pyramid we're combining two different topics here today so we have two different objectives and two skills to practice the first objective is to be able to explain how energy and matter flow through trophic levels and the second objective is to be able to determine how energy decreases as it flows through an ecosystem the two skills we'll practice at the end of today's video are explaining an environmental concept of process and then calculating an accurate answer with units so we will be doing some math at the end of this video so before we talk about how energy flows through ecosystems we have to establish the conservation of both matter and energy so very important to remember that matter is never created or destroyed it only changes forms this is key to understanding how both matter and energy flow through ecosystems so let's take a look at an example when a tree dies the tree will get decomposed and we may not see the tree physically anymore but all of its matter was conserved so the carbon the nitrogen the water and the phosphorus within the tree were all returned to either the soil or the atmosphere or went into the bodies of decomposers and so we did not actually lose any of the matter it looks different but it still exists and it's just transformed into a different state let's talk about this with regard to energy as well so if we look at photosynthesis we have the sun's rays which represent light energy and they're going to be converted into chemical energy by the plant and that's glucose so if we look at the diagram and we were to actually count up all of the atoms involved in that process we'd see that all of the carbon oxygen and hydrogen entering the plant as carbon dioxide and as water flowing from the soil are all going to be conserved either as glucose or as oxygen that leaves the plant's leaves during photosynthesis so photosynthesis helps us kind of grasp here the conservation of matter but also the conservation of energy because we have the sun's rays that hit the leaf that's a form of energy but once those rays hit the leaf they're not destroyed they're just transformed into glucose which again is chemical energy so photosynthesis is a really helpful way to remember both the conservation of matter and energy we have a fancy name for this it's called the first law of thermodynamics and that's just a reminder that energy is never created or destroyed it's just transformed into a different form biogeochemical cycles that we've spent the last couple days on so the water cycle carbon cycle nitrogen and phosphorus cycles those all demonstrate that there's conservation of matter so again when an animal dies the nitrogen in its body is never destroyed it's just transformed it goes through modification returns to the soil as ammonia and then can be used for plant growth in the future food webs which we'll focus on today and tomorrow are how we demonstrate the conservation of energy so we talked about the conservation of energy with photosynthesis but let's look at it with an animal here so let's imagine that a rabbit is going to eat the leaf that produce that sugar through photosynthesis so the leaf is no longer there but the energy in the leaf has been transferred to the rabbit the glucose in the leaf is going to be broken down by the rabbit's body it's going to feel growth of the rabbit so some of it might be converted into muscle or fat tissue within the rabbit some of it might go to feel the rabbit's movement so that energy is conserved it's never destroyed even though the leaf was eaten by the rabbit now we'll talk about what happens to energy as it transfers between trophic levels so each time energy transfers from one form to another some of it is lost as heat now it's not destroyed but it's just given off to the surrounding environment and it's no longer useful energy that can be used by organisms and so we'll talk about what that means here in a second let's take a look at an example with electricity generation if we have this coal-fired power plant here and all of the potential energy in the bonds of that coal are released and converted into electricity only about 35 of the energy that was in the coal is going to actually make it to electricity the other 65 percent is going to be lost as heat while the coal is being burned then as that electricity is flowing down transmission wires another 10 or so is going to be lost and only about 90 of the electricity is going to actually make it into your home then when you turn on a light bulb 95 of the energy flowing into the light bulb is lost as heat meaning only 5 is coming through as actual light energy so what this demonstrates is each time we transfer energy from one form to another so from chemical energy in coal to electrical energy to light energy we're losing some of it as heat now we can think about what this means as it applies to ecosystems so each time energy is transferred from one organism to another the amount of available energy is decreasing and that's because the organism that was just eaten had used up most of the energy for things like movement development and just cellular respiration fueling all of the processes its body needs in order to survive so we can look at an example here with an ecosystem if we have a thousand joules of light energy that the producers are receiving remember they're going to need to use 90 of that so they're going to use 990 joules for their growth for their metabolism all of those things and only about 10 joules are going to be available to the elk when the elk eats the grass it gets those 10 joules of energy but then it's going to use up nine of those joules for again development cellular respiration and it's going to be lost as heat to the atmosphere then when the line eats the elk and i don't know what kind of ecosystem we're in here where a line eats out but it's just a helpful diagram it's only going to get that one joule of energy so that means that each time the energy transfers from one organism to another only 10 percent of the energy is making it to that next organism so because the amount of available energy decreases with each step you go up the trophic level we use a pyramid shape to represent this and trophic just means growth or nourishment so that's a helpful way to remember what a trophic level is and so because there's the most energy available at the base it's going to be the widest and then each level up is going to get a little bit more narrow because there's less available energy at that level remember we didn't actually destroy energy it was used up by the organisms so it was lost as heat as they move around or is used up in cellular respiration but only about 10 percent of it is going to transfer onto the next level and so we have a handy rule to remember this and we call it the ten percent rule ten percent rule just reminds us that only about ten percent of the energy from one trophic level makes it to the next the other ninety percent is lost as heat while the organism uses that energy for all the processes it needs to fuel so if we take a look at this diagram we can kind of see that represented here from the producers only about 10 of the energy is going to move on to the rabbits who are the first level to consume the grass 90 will be lost as heat then on to the snakes another 10 90 losses heat and the same thing for the top predator here now we'll talk about the names for each trophic level as well as how the 10 rule also applies to biomass so at the bottom we have the producers these are the plants and they form the base since they are going to produce the usable energy in every ecosystem remember though they're not really making the energy they're just converting light energy into chemical energy in the form of glucose the next level is the primary consumer level and these are the animals that are eating the plants to get their energy and we call them herbivores then we have the secondary consumer level these are animals that are going to eat primary consumers and so we call these either carnivores or omnivores because sometimes these secondary consumers also eat from the producer level so this example here of a blue jay a blue jay eats some animals but also eats some plants same thing with the raccoon and so we call those omnivores and they can belong to two different trophic levels then finally we have the tertiary consumers and these are our top or our apex predators so these are organisms that are going to feed on secondary consumers now we'll talk about the 10 rule as it applies to biomass so because energy is needed for growth and only 10 percent of the energy from one trophic level makes it on to the next that also means that only about 10 of the biomass can be supported now what is biomass biomass just refers to the total mass of all living things at a certain trophic level and so if we're to look at this diagram here at the base we could support about a thousand kilograms of producers but since only about ten percent of the energy moves on to the primary consumer level that means we can only have about 10 of the biomass as well since all biomass needs energy in order to be developed to be grown so we're only going to be able to support about 100 kilograms of primary consumers from that thousand kilograms of producers then that's going to decrease by 10 again by 90 excuse me uh so we'll have 10 kilograms at the secondary consumer level and finally when we get to the top of the pyramid there can only be one kilogram of tertiary consumer biomass for every thousand kilograms of producer biomass so this is really important i want to reiterate this at the base only 10 of the energy moves on to the primary consumer level so only 10 of the biomass can be supported so that's why when we look at a given ecosystem there are far far far more plants than any of the animals in the ecosystem and that's because you can only support 10 percent of the primary producers that you had at the consumer level same thing with the secondary consumers and same thing with the tertiary consumers so now we'll practice actually calculating the amount of energy available at different levels so it's a really simple calculation to calculate the energy available at the next trophic level up you're just going to move the decimal spot one place to the left or just divide by 10. so if we use this example where we have 95 000 joules at the producer level we would just move that decimal place one spot to the left or divided by 10 and that should give us 9500 joules roughly that would be available to the primary producers so what i want you to do is see if you can calculate the secondary producer level and the tertiary producer level so again pretty simple we're just moving the decimal place one spot to the left we're dividing by 10 so at the secondary consumer level we'd expect 950 joules and then only about 95 joules available at the tertiary consumer level since the 10 percent rule also applies to biomass we can do the same type of calculation to determine how much biomass would be found at each level so starting out with 80 kilograms of the secondary consumer i want you to see if you can work both up and down the pyramid to figure out how much biomass would be supported at each of those levels so again we're just moving that decimal place one spot to the left to figure out the tertiary consumers which will only be eight kilograms but we're actually going to do the opposite and move the decimal place to the right as we go down the pyramid so that would give us 800 kilograms at the primary consumer level and 8 000 kilograms at the primary producer level so our practice frqs for topics 1.9 and 1.10 today we'll be covering two different skills one is explaining environmental concept or process the other is calculating an accurate answer with units so first i want you to explain why a relatively large forest can only support a small number of wolves and then i want you to calculate the amount of energy available to a tertiary consumer in an ecosystem where there are a hundred thousand joules of energy produced by plants