[Music] hi I'm welcome back to three size lessons cold UK by the end of this video you should be able to describe the biotic and abiotic factors that can affect a community in the last video we saw that biotic factors are the living parts of an environment and the abiotic factors are the nonliving parts in this video we're going to look at these in more detail there are four different biotic factors and in the exam you could be asked about any of them the first biotic factor is the availability of food all animals eat other living organisms for example lions eat other animals whereas animals such as zebras eat plants however all sources of food whether animals or plants are a biotic factor and if the availability of food Falls then the number of organisms in that community will also fall another biotic factor is the arrival of a new predator this can cause the population of a prey species to fall a new predator can also affect existing predators for example if they're competing for the same prey competition between species as another biotic factor if a species is out competed then its population can fall so much that numbers are no longer sufficient to breed and the species may become extinct the final biotic factor on new pathogens if an infectious disease emerges and then spreads it can wipe out a population of a species okay we're going to take a look now at a biotic factors and remember that abiotic means not living there are seven different abiotic factors and in the exam you could be asked about any of them the first abiotic factor is light intensity and this can have a major effect on plants all plants need light to carry out photosynthesis however if the light intensity is too low then the rate of photosynthesis Falls and plants will grow more slowly now this can have a major impact on a community if plants grow more slowly than animals which feed on plants may not have enough food temperatures also a really important abiotic factor if the temperature of an environment changes then this could cause the distribution of species to change for example animals could migrate and plant species might simply disappear from that area both plants and animals need water to survive so water is also a major abiotic factor many species are adapted to deal with low levels of water and we'll be looking at these adaptations in the next video the pH and mineral content of the soil is an important abiotic factor for plants many plants cannot go on soil which is too acidic or too alkaline plants also need certain minerals in the soil for example nitrate which is used to make amino acids for proteins the wind intensity and direction is another abiotic factor that can affect plants for example strong winds blowing inland from the sea can cause plans to lose water so plants growing in sand dunes are often adapted to reduce water loss the final abiotic factors are the gases carbon dioxide and oxygen carbon dioxide is needed for plants to photosynthesize and if carbon dioxide levels fall then the rate of photosynthesis can also decrease oxygen is needed for air orbit respiration now the level of oxygen in the air stays fairly constant however the level of dissolved oxygen in water can fall for example on hot days and this can be harmful to aquatic organisms such as fish remember your found plenty of questions on biotic and abiotic factors in my vision workbook and you can get that by clicking on the link above [Music]