population in an ecosystem Flashcards
ecology
the study of inter-reloationships between species and the environment
biotic
living factors of the environment
aboitic
non-living factors of the environment
what is a ecosystem
Ecosystems are dynamic systems made up of a community and all
the non-living factors of its environment.
what are the two main parts to an ecosystem
the flow of energy through the system
• the cycling of elements within the system.
population
all individuals of the same species that can interbreed to produce fertile young in the same habitat at the same time
carrying capacity.
when a ecosystem supports a certain size of a population.
what can affect population size
the effect of abiotic factors
intraspecific and interspecific competition
predation.
community
all populations of the different species living and interacting in same habitat at the same time
habitat
A habitat is the place where an organism normally lives and is characterised by physical conditions and the other types of organisms
microhabitat
smaller units within habitats that have their own microclimate
competitive exclusion principle
states that two species that compete for the exact same resources cannot stably coexist
niche
it describes how a species fits into the habitat
it is where an organism lives and what it does there.
It includes all the biotic and abiotic conditions which an organism is adapted
examples of limiting factors to bacteria population
biotic
• The population becomes so large that the bacteria at the surface
prevent light reaching chose at deeper levels.
Other species are introduced into the pond
examples of limiting factors to bacteria population
abiotic
Winter brings much lower temperatures and lower light intensity of shorter duration.
Mineral ions are consumed as the population becomes larger.
temperature
and cold-blooded animals, as temperatures rail below the optimum,
the enzymes work more slowly and so their metabolic rate is reduced.
Populations therefore have a smaller carrying capacity.
At temperatures above the optimum, the enzymes work less
efficiently because they gradually undergo denaturation. Again
the population’s carrying capacity is reduced.
temperature in warm blooded animals
temperature of the external environment gets rrom their optimum
temperature, the more energy these organisms expend in trying to
maintain their normal body temperature. This leaves less energy
for individual growth and so they mature more slowly and their
reproductive rate slows. The carrying capacity of the population is
therefore reduced.
light
The rate or photosynthesis increases as
light intensity increases. The greater the rate or photosynthesis,
the faster plants grow and the more spores or seeds they produce.
Their carrying capacity is therefore potentially greater. In tum, the
carrying capacity of animals that feed on plants is potentially larger.
ph
This affects the action of enzymes.
Each enzyme has an
optimum pH at which it operates most effectively. A population of
organisms is larger where the appropriate ph exists and smaller,
or non-existent, where the pH is different from the optimum.
water
Where water is scarce, populations are small and consist only of species that are well adapted to living in dry conditions.
humidity
Humidity affects the transpiration rates in plants and the evaporation of water from the bodies of animals.
dry air conditions, the populations or species adapted to tolerate low humidity will be larger than those with no such adaptations.
population change equation growth rate
population change during the period/ population at the start of the period
x 100
population growth
= (births+ immigration ) - (deaths + emigration )
Intraspecific competition00.
is when individuals of the same species
compete with one another for resources such as food, water. breeding sites, etc.
The greater the availability, the larger the
population. The lower the availability, the smaller the population.
Availability of resources also affects the degree of competition between
individuals which results in a smaller population.
interspecific competition
Imerspecific competition occurs when individuals of different species
compete for resources such as food, ligh t, water, etc.
competitive exclusion principle.
When populations of two species are in competition one will normally have a competitive
advantage over the other.
The population of’ this species will gradually increase in size while the population of the other will diminish. If conditions remain the same, this will lead to the complete removal of one species.
A predator
is an organism that feeds on
another organism, known as their prey.
prey
is consumed by the predator
what happens when a predator and prey are left in a lab
the prey is exterminated
why are prey not fully exterminated in the wild?
This is largely because the range and variety of the habitat
prey is limited to the confines of the laboratory.
The area over which the population can
travel is far greater and the variety of the environment is much more diverse.
there are many more potential refuges.
there are the harder they arc to find and catch. Therefore, although the
prey population falls to a low level, it rarely becomes extinct.
why is lab work not fully accurate
it is difficult to obtain reliable data on natural populations
because it is not possible to count all the individuals in a natural population.
Its size can only be estimated from sampling and
surveys. These are only as good as the techniques used.
predator prey relationship
Predators 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 survive.
- 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.
natural selections with prey
a selection pressure which means that
those individuals who are able to escape predators, or withstand disease or
an adverse climate, are more likely to survive to reproduce. The population
therefore evolves to be better adapted to the prevailing conditions.
abundance
the number of individuals of a species in a given space. .
factors that affect the type of quadrat
The size of quadrat to use.
The number of sample quadrats to record within the study area.
The position of each quadrat w ithin the study area.
The size of quadrat to use
This will depend on the size of the plants or animals being counted and how they are distributed within the area. Larger species require larger quadrats. Where a population of species is not evenly distributed throughout the area, a large 55656number of small quad rats will give more representative results than
a small number of large ones.
