the key thing to understand in ecology is that all organisms have relationships for example mice have relationships with other mice with the plants they eat with the predators that eat them and with all the other animals that live nearby they also have relationships with the environment itself for example they'll breathe in oxygen from the air and breathe out carbon dioxide or they'll burrow holes in the soil which can increase irrigation and so improve the quality of that soil because of all these relationships if any one part of the ecosystem changes for example the mouse population falls it can affect all other parts of the ecosystem so in this case it could mean that predators have less food and soil quality decreases before we go any further it's worth running through some of the special terms that you need to know for ecology the first is habitat which is just the place where an organism lives so for our mice that could be a field a forest or somebody's basement meanwhile a population is all of the organisms of a particular species that live in that habitat so all the mice that live in the field next we have the community which is all the populations of different species that live together in a habitat so the community would involve not only the mice but also the owls the plants and any other organisms that live in that field two more terms are biotic factors which are the living factors of the environment like the availability of food or the number of predators and abiotic factors which are the non-living factors of the environment like temperature and soil ph we'll take a closer look at these two in our next video as they're both a bit harder to understand if we put all of these together so the habitat the community that lives there and all of the bartik and abiotic factors what we have overall is the ecosystem which we could describe as the interaction of a community of living organisms with the non-living parts of their environment and ecology is really about understanding how these ecosystems function and also how they might change in the future one of the most important processes in an ecosystem is competition if you think about any organism it's going to need a range of different resources to survive for animals this usually includes things like space which we can call territory food water and also mates so that they can reproduce meanwhile plants need things like light space and water and mineral ions which they get from the soil the problem is that all of these resources are limited so to make sure they get enough of them organisms have to compete with each other and this competition might be between organisms of different species like when lions and hyenas compete for a wildebeest or between organisms of the same species such as when male deer compete with each other for females the last key term we need to cover is interdependence which is the idea that all species depend on other species in some way we can see how this works with a food web which show the feeding relationships within a community so here we can see that mice rabbits and grasshoppers all feed on the grass and then the shoes and sparrows feed on the grasshoppers and so on the important thing to understand here though is that if anything happens to one of these species then it will affect all of the others for example take a second to think about what might happen if the mouse population suddenly increased well as all these mice need food let's start eating the grass which would mean that there was less grass available for the rabbits and grasshoppers so their populations would fall meanwhile the hawks would suddenly have a lot more mice to eat so their population might increase however as they also feed on rabbits and we just said that there would be fewer rabbits the hawk population might not actually increase all that much and if we wanted to we could go on to describe the effects on all the other species too such as how the decline in grasshoppers could lead to a decline in the shrew and sparrow populations as well there's no need to remember any specific examples you just need to understand how these relationships work and be able to predict the knock-on effects of any changes anyway that's all for today so i hope you found it useful and we'll see you next time