 A really simple example of an ecosystem and its carrying capacity is something like this terrarium here, which is a really neat semi-closed system. We do help it out a little bit with a few different resources. Thinking about it in terms of those abiotic and biotic factors, there's a few different things we want to consider. In terms of abiotic, we've got different amounts of sunlight. We've got that water that we're helping it out with. There's also the soil type to consider as well. In terms of the biotics, we've got a few different plant species here. We've also got a few insects that are making their home in here as well and nibbling on the plants. We've also got some microbes in the soil. Now all of these interact together to have those really complex transfers of energy and matter in the ecosystem. So within the system, a kind of key abiotic factor is that sunlight. It's coming in and the plants are using that energy to convert CO2 to oxygen. That oxygen is being used by our insects and those soil microbes as well. In turn, the insects and the soil microbes are eating plant matter in different forms. The insects might be eating the living tissue and the soil microbes are helping decay any of the old dead plant tissue that's full into the soil and converting that into nutrients for the plant again. In doing so, we've got this kind of complex network and this cycle of matter and energy in our system. This in turn defines our carrying capacity. Now we can think about that carrying capacity in terms of the actual ecosystem level but we can also think about it for a given species within that ecosystem. So for example, our plants. And in that case, a specific subset of those factors might be more important for that plant. So sunlight, water, these kinds of things. So the carrying capacity of that individual species can be separate from the ecosystem as a whole. Another important thing about carrying capacity is that it can change. Because we have this really complex set of interactions and this network of energy and matter, any small change within that or any big changes can result in a change in carrying capacity. So for something like our terrarium, say if we decided to limit the amount of sunlight or we forgot to water it, we might end up with our ecosystem collapsing because we've interrupted that network and as a consequence our carrying capacity has declined. In real ecosystems, carrying capacity can be very complex because we go outside of that kind of small terrarium example and we've suddenly got a lot of different factors to consider. But it's still a really useful concept especially in conservation where we want to understand that maximum sustainable population in an ecosystem. A good example of this is the southern brush-tailed rock wallaby. This is the ACT mammalian emblem and it was last seen in the wild in the ACT in the 1950s. The population experienced some pretty big declines mainly due to various introduced species that were both predators and also competitors. Land clearing and also changed fire regimes. As a consequence, our local ecosystems carrying capacity for this species rapidly declined which meant that suddenly the species couldn't really manage to exist. Now at Tibbin Bill and Nature Reserve, the population there has been kind of reintroduced. They're managing it in enclosed fenced areas so that they can actually maximize the carrying capacity for this species in that ecosystem. So they're making sure that there are abundant food resources available. They're excluding those predators and competitors and in doing so they're making sure that that population can grow as much as possible and allow us to then manage reintroductions and other similar conservation efforts for this species and all because we are able to recognize the factors that are affecting the carrying capacity of this species and consequently manage them. Thank you.