3.7.3 Populations and Ecosystems Flashcards
Why is it important to measure species diversity?
to compare different habitats or study how a habitat has changed over time
Define niche
The role of a species in it’s environment
Define community
All of the organisms of different species that live in the same habitat and interact with each other
Define population
All the organisms of one species in a habitat
Define mutualism
A relationship between two organisms where both benefit
Define ‘population size’
The number of individuals of one species in a particular area
Define ecosystem
All the organisms living in a particular area and all the non living (abiotic) factors
Define habitat
The place where an organism lives
Define species distribution
Where a species is within a particular area
Define abundance
The number of individuals of one species in a particular area
Define biotic factors
The living features of the ecosystem (e.g. predators, prey, microorganisms)
Define abiotic factors
The non living features of the ecosystem
Define carrying capacity
The maximum stable population size of a species
What happens as a population of organisms approaches carrying capacity (k strategist)
Density dependent factors limit the rate of population growth (eg availability of food). This is sometimes referred to as environmental resistance
How can some organism have a polulation above carrying capacity
They reproduce very quickly (often small organisms - R strategists) and a population boom will be followed by a bust (dramatic decrease).
what formula determines the size of a bacterial population growing exponentially
Population = Starter population x 2^n (where n = number of generations)
why do we often use logarithmic graphs when plotting bacterial populations
When the populations have a very large range (ie you have to plot very small numbers and very large numbers)
What is a producer (or an autotroph)?
Organisms that produce their own food (usually through photosynthesis)
Which factors determine the numbers and distribution of organisms in a habitat ?
Biotic and Abiotic factors
What is primary succession?
Occurs on land that has been newly formed or exposed
What is secondary succession?
Occurs on land that has been cleared of all plants, but where the soil remains
What is a climax community?
A stable community usually dominated by trees that remains unchanged unless conditions in the habitat change
What is a pioneer species?
The first species to colonise an area, tends to be very specialised
How does primary succession start?
When species colonise a new land surface, seeds and spores are blown in by the wind and begin to grow
Describe the abiotic conditions at the start of primary succession
Hostile, there is no soil to retain water
How can pioneer species grow in primary succession?
They are specially adapted to cope with the harsh conditions (extremes of temp, lack of soil, water and nutrients)
How do pioneer species change the abiotic conditions ?
They die and microorganisms decompose the dead organic material forming basic soil. So the conditions are less hostile
When the conditions are less hostile what happens (primary succession) ?
the basic soil retains water so new organisms with different adaptations move in and grow. these then die and decompose adding more organic material, making the soil deeper and richer in minerals
Define dominant species
Outcompete the plants and animals that are already there as they are better adapted. They are the most abundant species.
What is interspecific competition ?
when organisms of different species compete with each other for the same resources
What is intraspecific competition ?
When organisms of the same species compete with each other for the same resources
what is the competitive exclusion principle and can you draw a graph of paramecium populations to illustrate
If 2 organisms with a similar niche are grown in a habitat or culture, only one will survive.
What is the carrying capacity of a population?
The maximum stable population size of a species
How are the population sizes of predators and prey interlinked ?
as the population of one changes, it causes the other population to change
What happens when the prey population increases?
There is more food for predators so the predator population grows
What happens when the predator population grows?
More prey is eaten so the prey population decreases
What do grazing, predation and parasitism have in common ?
They are relationships between two organisms where one benefits at the others expense
what is conservation
the management of the earths natural resources by hyuman in such a way that maximum use of them can be made in the future
What are some different types of reasons to conserve ecosystems and biodiversity
Personal reasons, ethical reasons (it is the right things to do), economic reasons (the ecosytem provides ecosytem services such as pollination and clean air), cultulral and aesthetic reasons
why might conservationists sometimes prevent succession
In some cases, transitional communities may have higher biodiversity (but lower biomass) than climax communities. This may be true in places like moorland where succession is prevented by either grazing or periodic burning
What is deflected succession
Where some activity prevents succession to a climax community. A plagioclimax community is reached instead (eg moorland)
