Populations Flashcards
Define abiotic
Non-living factors such as temperature, rainfall, pH and light intensity in an environment that influences the size of a population.
Define adaptation.
An organism adapts to their environment by adjusting their behaviour, physiology and structure of itself to become better suited to survive and successfully pass their genes onto the next generation.
Define biotic.
Living factors eg competition and predation in an environment that influence the size of a population.
Define community.
ALL of the populations of different species living and interacting in a particular place at the same time.
What is the ‘competitive exclusive principle’?
Interspecific competition leads to populations of two species competing for resources. One species usually has a competitive advantage over the other. Thus, the population of this species will gradually increase in size whilst the other diminishes.
Define population.
A group of individuals of one species that occupy the same place at the same time (with the potential to interbreed).
The size of a population can vary as a result of:
- the effect of abiotic factors.
- interactions between organisms (eg intra and inter specific competition and prediction).
Define habitat.
The place where an organisms normally lives and is characterised by physical conditions and the other types of organisms present.
What is a microhabitat?
Within each habitats are smaller units, each with their own microclimate.
Define niche.
Where an organism lives and what it does there. It includes all the abiotic and biotic conditions to which an organism is adapted.
Define competitive exclusion principle.
No two species occupy exactly the same niche. For example due to different tolerance of environmental factors eg pollution.
What is the carrying capacity determined (limited) by?
Factors such as:
- availability of food
- light
- water
- oxygen
- shelter
- accumulation of toxic waste
- predators
- disease
What abiotic factors influence the size of a population?
- temperature
- light
- pH
- water and humidity
Outline how pH is an abiotic factor that can influence the size of a population.
pH affects the action of enzymes. Each enzyme has an optimum pH at which it operates most effectively.
A population is larger where appropriate pH exists. And smaller, of non-existent populations where the pH differs from the optimum.
Outline how water and humidity, as an abiotic factor, influences the size of a population.
Where water is scarce, populations are small and only consist of populations adapted to dry conditions.
Humidity affects transpiration rates in plants and the evaporation of water from the bodies of animals. So, again, in dry air conditions, the populations adapted to tolerate low humidity will be larger than those with no such adaptions.
Define ecosystem.
A dynamic system made up of a community and all non-living factors of its environment. They can range in size from very small to very large. Eg: freshwater pond, lake, a woodland.
Define environment.
The external surroundings including all the biotic and abiotic factors that surround and affect the survival and development of organisms of a population.
Define habitat.
The place where an organism normally lives and is characterised by physical conditions (abiotic factors) and with other types of organisms present. Within an ecosystem, there are many habitats.
Define interspecific competition.
Competition between organisms of different species. Eg for resources such as food, water, light.
Define intraspecific competition.
Competition between organisms of the same species. Eg for food, water, breeding sites.
How can intraspecific competition lead to smaller populations?
The availability of resources (eg food) can affect the degree of competition between organisms - resulting in a smaller population.
Define prediation.
A relationship between two organisms of different species in which one organism is a predator that captures and feeds in the organism that serves as prey. This affects population size.
What is the difference between a habitat and a niche?
Habitat = where a species lives. Niche = what it does in that habitat.
What are 3 ways that organisms can adapt?
Physiological (inside their body), behavioural and anatomical (structural features of their body).
What is population size?
The total number of organisms of one species in a habitat.
Define carrying capacity.
The maximum stable population size of a species that an ecosystem can support.
The carrying capacity carries as a result of abiotic and biotic factors.
Outline how inter specific competition can be a problem (re food).
If two species share the same food source, there will be less available to both of them.
This means both populations will be limited by a lower amount of food.
They’ll have less energy for growth and reproduction, so the population size will be lower for both species.
What happens in inter specific competition if one species is better adapted?
The less well adapted species is likely to be outcompeted (eg the grey squirrel outcompetes the red squirrel).
In intra specific competition, how can population fluctuate?
The population of a species increases when resources are plentiful. However, as the population increases, there’ll be more organisms competing for the same amount of space and food.
Eventually, resources eg food become limiting (there isn’t enough) so population begins to decline.
A smaller population then means there’s less competition for resources eg space and food, which is better for growth and reproduction - so the population starts to grow again.
How can predation cause the population to fluctuate?
As the prey population increases, there’s more food for the predators, so the predator population grows.
As the predator population increases, more prey is eaten so the prey population begins to fall.
This means that there’s less food for the predators, so their population decreases and so on.