19 Populations in ecosystems Flashcards
Define biosphere
The region on, above, and below the Earths surface where life exists
What is an ecosystem?
Dynamic systems made up of a community and all the non-living factors of its environment. There are two major processes to consider; the flow of energy through the system, the cycling of elements within the system.
What is meant by the term population?
A group of individuals of one species that occupy the same habitat at the same time and are potentially able to interbreed.
What does the term ‘carrying capacity’ mean?
An ecosystem supports a certain size of population of a species. Anything after this is referred to as the carrying capacity.
Define community
All the populations of different species living and interacting in a particular place at a particular time.
Define habitat
The place where an organism normally lives and is characterised by physical conditions and other types of organisms present. Within an ecosystem there any many habitats.
What is an ‘ecological niche’
Describes how an organism fits into its environment. It refers to where an organism lives and what it does there. Two species cannot occupy exactly the same niche (the competitive exclusion principle.)
What factors determine the size of a population?
The effect of abiotic factors, interactions between organisms eg. Intraspecific and interspecific competition and predation.
What abiotic factors effect the size of a population?
Temperature- Each species has a different optimum temperature at which it is best able to survive.
Light- A basic necessity of life, increases rate of photosynthesis meaning that plants grow faster, meaning that their carrying capacity is potentially higher and therefore the carrying capacity of animals that feed on plants is also higher.
PH- Each enzyme has an optimum PH at which it operates more effectively. A populations of organisms is larger where the appropriate PH exists.
Water and humidity- Where water is scarce, populations are small and consist only of species that are well adapted to living in dry conditions. Humidity affects transpiration rates in plants and the evaporation of water from animals.
Define intraspecific competition
When individuals of the same species compete with one another for resources such as food, water, breeding sites etc.
Describe interspecific competition
When individuals of different species compete for resources such as food, light, water etc.
How does interspecific competition influence population size?
One species will have advantage over the other species, meaning that the population of this species will gradually decrease in size and the other population size will diminish. If conditions remain the same, it can lead to complete removal of the species (competitive exclusion principle).
What does the competitive exclusion principle state?
Where two species are competing for limited resources, the one that uses these resources most effectively will ultimately eliminate the other. No two species can occupy the same niche when resources are limited.
What is meant by predation?
It occurs when one organism is consumed by another.
Explain the effect of predator-prey relationships on population size.
Predators can eat their prey, thereby reducing the population of prey.
With fewer prey available the predators are in greater competition with each other for the prey that are left.
The predator population is reduced as some individuals are unable to obtain enough prey for their survival or to reproduce.
With fewer predators left, fewer prey are eaten and so more survive and are able to reproduce.
The prey population therefore increases.
With more prey now available as food, the predator population in turn increases.
