BIOTIC LIMITING FACTORS: PARASITES
Parasites are living things that live on or inside other living things and use them or
their tissues for food. The living thing that a parasite feeds on is called the host.
The parasite lives off of the host. Most parasites weaken their host but rarely kill
them. Parasites may weaken their host enough that the host cannot reproduce and
therefore may slow down or stop the growth of that population. Parasites are
considered a biotic limiting factor in an ecosystem.
Fleas are wingless insects whose mouths are adapted for piercing skin and sucking
blood. They live on the outside of mammals and birds. Blood is their major
source of food. Fleas eat blood by sucking it out of their host.
BIOTIC LIMITING FACTORS: COMPETITION
Competition is an interaction between living things in which they use or
fight for the same resources in an ecosystem. Each member of a population of
species has the same needs for the same resources. These resources include
nutrients, shelter, light, water, and living space. There are often not enough
resources in an ecosystem to support all members of a population. Therefore,
single members of a population are in competition with each other for resources.
Those members who are too young, too old, and too weak, or injured often have
trouble getting all of the resources they need to live. They cannot compete with
other members of the population for resources and may die off. As a result,
competition limits the growth of a population and is a biotic limiting factor in an
Example: Lions and antelopes
Lions often hunt antelope. Lions living in the same area have to hunt for the
same antelope. There is a limited number of antelope in the area and therefore
lions have to compete with each other for this food. Young, old or weak lions have
more difficulty hunting and catching antelope, which may cause them to starve and
die. The population growth of lions is limited by the number of antelope available
BIOTIC LIMITING FACTORS: PREDATION
Predation is an interaction between living things where a predator feeds on
its prey. A predator is an animal that hunts, kills and eats other animals. The
animal that it eats is called its prey. Predation affects the predator population as
well as the prey population. Both populations benefit from this interaction.
Predators benefit by getting the food they need to survive. Some prey benefit
because the predators often eat old, sick, or weak members of the prey population.
This makes the prey population stronger as a whole. Predators help to keep the
prey population from growing too large and therefore predation is a biotic limiting
factor in an ecosystem.
Example: Tigers and rabbits
Tigers and rabbits living in the same area benefit each other. Tigers often hunt and
ambush young or weak rabbits, which makes the population of rabbits stronger as a
whole. The tigers benefit since they need to eat rabbits to survive. Rabbits can
reproduce quickly and increase their population. However, tigers kill rabbits and
therefore limit the number of rabbits in an ecosystem.
BIOTIC LIMITING FACTORS: PLANT COMPETITORS
Animals are not the only living things that compete. Plants also compete for
the resources they need. For example, plants need light and water. Members from
the same plant population compete with each other. They also compete with
members of different plant populations. Since there are not enough resources for
all the plants in an ecosystem, some of them die off. Plant competition affects the
population size of plants and therefore is a biotic limiting factor in an ecosystem.
Example: Plants in the Amazon Jungle may compete for light from the Sun. One
type of plant may be taller than another type and prevent shorter plants from
getting enough sunlight. As a result, the shorter plants cannot carry out
photosynthesis to make their own food. Ultimately, the plants that do not receive
enough light with die. Therefore, the population size of short plants is limited.
Competition between plants is a limiting factor in an ecosystem.