Populations in Ecosystems

• A species is a group of organisms that occupy the same area at the same time, meaning that they are capable of breeding together to produce fertile offspring
• Species do not exist by themselves in their own isolated environment, they interact with other species forming communities
• A community is multiple populations of different species living and interacting in the same area
• Communities can interact with the non-living components of the environment they live in, to form ecosystems
• An ecosystem is the interaction between a community and the non-living parts of the environment
• An ecosystem is a relatively self contained community of interacting organisms and the environment they live in, but is not entirely self contained as organisms tend to migrate
• There is a flow of energy within an ecosystem and the nutrients within it are recycled. This means that ecosystems can vary greatly in size, scale and complexity
• The place where a species lives within an ecosystem is its habitat
• The role a species plays within the habitat is known as its niche, which includes both the biotic and abiotic interactions of the species
• A niche can only be occupied by one species, meaning that every individual species has its own unique niche, and if two niches overlap, the species will compete with each other for the same resources
• When individuals compete in the same niche, one of the species will be more successful and out compete the other until only one species is left and the other is either forced to occupy a new niche or go extinct
• Adaptations are features of organisms that increase their chances of surviving and reproducing
• What are the types of adaptations?

  Anatomical, behavioural and physiological
• A species must be adapted to both the biotic and abiotic factors within its habitat in order to occupy its unique niche
• The changes that a species produce in their abiotic environment can result in a less hostile environment, which can change or increase the biodiversity within that environment
• What are ecosystem engineers?

  Organisms that can change the abiotic environment in their habitat, which can make it less hostile
• Population size is measured as the total number of organisms of one species in a habitat
• What is the carrying capacity?

  The maximum stable population size of a species that an ecosystem can support
• Abiotic and biotic factors prevent every population growth, this ensures that the populations size of each species is limited at some point
• There is fluctuation around the carrying capacity, and when the population size gets too high above the carrying capacity, extinction and large levels of competition occurs
• What are the consequences of exceeding carrying capacity by too much or for too long?

  The population will go extinct or the carrying capacity will be permanently lowered
• Abiotic factors involve the non-living parts of an ecosystem
• What are some examples of abiotic factors that can limit population size?

  Light availability, water supply, temperature and soil pH
• When abiotic conditions are suitable, there is fast growth of the population, as successful breeding causes the population to increase
• When abiotic conditions are unsuitable, there is slow growth in the population as breeding is less successful and the population will be stable or decrease
• Biotic factors involve the living parts of an ecosystem as they are the interactions between organisms
• What are three main types of biotic factors?

  Interspecific competition

  Intraspecific competition

  Predation
• What is Interspecific competition?

  When individuals from different species compete for the same resources
• Interspecific competition can sometimes cause both populations of the species to decrease as each of them has access to fewer resources and therefore less chance of survival and reproduction, this occurs if they are similarly well adapted to the habitat
• Interspecific competition can lead to a decrease in the population size of one species and an increase in the other, occurring when one outcompetes the other for resources, thus having a greater chance of surviving and reproducing, meaning that species is better adapted to the habitat
• Intraspecific competition is when individuals of the same species compete for the same resources
• What is an example of intraspecific competition?

  When resources are plentiful, a population of a species will increase, this means that there are more individuals competing for these resources, and at some point the resources become limiting and the population can no longer grow in size
• Predation is when an organism kills and eats another as a source of food
• Consumers that kill and eats another other animals are known as predators, and those eaten are known as prey
• In a stable community, the numbers of predators and prey rise and fall in cycles, limiting the population sizes of both
• Describe some of the key patterns of predator-prey cycles?

  The number of predators increases as there is more prey available

  The number of prey decreases as there is now more predators

  The number of predators decreases as there is now less prey available

  The number of prey increases as there are now fewer predators

  The cycle repeats
• What is abundance?

  The number of individuals of one species in one area
• The abundance of a species can be counted, the frequency or percentage cover can be calculated
• The distribution of a species described how it is spread throughout the ecosystem
• What is sampling?

  A method of investigating the abundance and distribution of a species and populations