hey everybody it's mr smeeds and today we'll be covering topic 1.8 which is primary productivity so you guys probably already know primary productivity as photosynthesis but we'll be exploring in a little more depth today our objective is to explain how solar energy is acquired or taken in and transformed by living organisms the skill that we'll be practicing in the frq at the end of today's video is to describe an environmental concept or process now we'll talk about some of the basics of primary productivity so it's just the rate that solar energy or light is transformed into organic compounds like glucose or cellulose through photosynthesis over a period of time so we'll take a look at the units here that we use to measure primary productivity and they're going to be kilocalories per meter squared per year now we can use different measures but they always have to be expressed in this format where it's a measure of energy so kilocalories per a given area meter squared over a given time in a year so we can also think of this as the rate of photosynthesis of all the producers in a given area over a period of time so we can kind of use the analogy of plants as workers so think of all the workers in a factory and how many gadgets they produce over a given period of time that would be the productivity of the factory what we also want to do is think of this as the rate of plant growth since photosynthesis translates into plant growth areas that have higher productivity are going to have higher plant growth this is just an easier way to kind of grasp what productivity actually looks like in an ecosystem then there's also a couple trends that we want to understand so the higher the primary productivity in a given area the higher the plant growth which means that there's going to be more food and shelter available for animals which means there will be higher biodiversity so this is a really important trend it's one we'll talk about more than once in this video and that's that ecosystems with high primary productivity are going to have a higher diversity of species they can support and therefore we would consider them to be more biodiverse now we'll take a look at how to actually calculate primary productivity so the first thing we have to remember is that plants use up some of the energy that they harness from the sun for cellular respiration so this goes to things like fueling their movement or the internal transportation that they do so just like humans use up energy for digestion tissue repair things like that so think of respiration loss as the amount of energy that plants use just to keep themselves running or you can think of it as the taxes that are taken out of the plant's paycheck then we have gross primary productivity this is going to be the total amount of sunlight that the plants capture and convert into energy or think of it as the total photosynthetic rate if we're sticking with the paycheck analogy you can think of this as the total paycheck amount that the plant earns by doing the work of photosynthesis then finally we have net primary productivity net primary productivity is going to be the amount of energy that the plant is able to actually store as biomass meaning the amount of plant growth that takes place this is what's left over for consumers like animals that need to eat the plants after the plants have used up the energy that they require for cellular respiration think of this as the take home pay the actual amount of money that the plant gets to take home put in the bank account after taxes are taken out we have a simple equation for this it's npp equals gpp minus respiration loss so we'll do some practice with these equations in a later video and then finally we have a diagram that can be really helpful to grasp what this actually looks like in a plant itself so we have the total amount of sunlight that goes into the plant and is converted into energy is gross primary productivity but then we have respiration loss so remember this is the energy used up by the plant for its basic processes that it needs to do to stay alive and then finally what's left over is net primary productivity and that is the energy that's left after respiration so this is energy that can be stored as sugars in the plant's fruit or in growth in its biomass so trees adding bark to the outside of their trunks or trees that add extra leaves or the leaves grow bigger all of that represents net primary productivity or the actual energy that the plant's able to store after it uses what it needs for cellular respiration so now we'll talk about a concept called ecological efficiency so this is the portion of incoming sunlight that's actually captured by plants and then converted into biomass so in other words net primary productivity or food that's available to consumers so in most ecosystems only about one percent of the sunlight that enters the ecosystem is actually captured by the plant and used for photosynthesis or gross primary productivity the rest of it so about 99 is either reflected back off the surface of the plant or just passes right through the leaf without being captured of this one percent only about 40 percent or 0.4 percent of the total incoming sunlight is converted into biomass or in other words net primary productivity however some ecosystems are more productive than others this could be due to the fact that they get more sunlight coming in or their plants are able to do more photosynthesis or they're actually more efficient than other ecosystems and finally we'll wrap up here by looking at some trends in productivity so remember this important trend that the more productive an ecosystem is the higher its biodiversity that's because there's a wider variety of plants and more of them to support a wider variety of animals so i want you to do is try to predict the highest productivity biome in terms of both aquatic and terrestrial and the lowest productivity biome in terms of both aquatic and terrestrial so take a look at this chart now here and see how you did instead of just memorizing though which biomes are most productive or which are least productive or trying to remember which biomes are the most biodiverse or least biodiverse i want us to pay attention to a couple important factors that determine productivity so focus on this trend here the more water available in a biome the higher the temperature is in the biome and the more nutrient availability in the biome are all factors that contribute to high net primary productivity so take a look here at the graph and we can see that swamps and marshes and tropical rainforest are going to be very highly productive biomes they're going to have high access to water they're going to have relatively warm temperatures that can support growth year round and they're also going to have high nutrient availability think about swamps and marshes which have tons and tons of organic matter in the bottom of their bodies of water lots of nutrient availability the coral reef ecosystem follows this trend as well it's very warm so it can support growth year round there's an abundance of water there's a lot of nutrients from the organic matter that is a part of the reef on the other hand we can look at examples of biomes that have low productivity and we can see that they have deficiencies in at least one of these three factors so first we can look at the desert the desert is going to have a deficiency of water and it's also going to have a deficiency of nutrients because the soil is extremely sandy which doesn't hold a lot of nutrients then we look at the tundra the tundra is extremely cold and so the tundra is going to have a very low temperature that can't support plant growth year-round it's also going to have a low access to liquid water there's a lot of frozen water in the tundra but that's not usable by plants for photosynthesis so it's going to limit primary productivity substantially and then finally we have the open ocean now the ocean in most parts of the world is going to be warm enough to support plant growth it's also going to have an abundance of water but it has a huge deficiency of nutrients so there's not a lot of organic matter in the open ocean to be used by producers and so the open ocean is going to have very low primary productivity our practice frq for topic 1.8 today is going to involve the skill of describing an environmental concept or process so first i want you to try to describe the process of net primary productivity and then i want you to describe the relationship between primary productivity and biodiversity alright everybody thanks for tuning in today don't forget to like this video if it was helpful subscribe for future apes video updates and check out other notes over here to the side and as always think like a mountain write like a scholar