Download Density-independent factors

5.2 Limits to growth
Limiting factors cause the growth of a
population to decrease.
A limiting factor can be many things, limited
water supply, limited food supply, limited
space, limited nutrients (such as nitrogen or
phosphorus.
For example, panda bears eat bamboo that
grows in the temperate forests of china.
Because humans need space, forests are
cleared which depletes the bamboo trees.
Therefore, bamboo has become a limiting
factor- and panda bear populations have
declined to near extinction
There are 2 main types of Limiting Factors
1. Density-dependent factors
2. Density-independent factors
Density-dependent factors
Density-dependent factors depend on the size
of a population in a given area.
In other words, if the population is high
(dense), density dependent factors will
appear
Examples of density dependent factors
1. Competition
2. Predation
3. Parasitism
4. Disease
These factors are not a big deal unless the
population is dense (or large)
competition
When a population is dense, individuals will
compete for the same resources.
Whenever there is competition, there must be a
winner and a loser – something must die.
In other words, individuals of the same species are
trying to occupy the same niche.
Predation
Predation is the relationship where one
organism (the predator) hunts, kills, and
eats another (prey)
This is called the predator-prey relationship.
The success of one will affect the success of
the other.
•
Parasitism and disease
Parasites (usually cause a disease) are similar
to predators.
They take nourishment from the host, at the
expense of the host.
This weakens the host and sometimes causes
death.
•
Density-independent factors
Density-independent factors affect all
populations in similar ways regardless of
the population size.
Examples are unusual weather, natural
disasters, seasonal cycles, human
activities such as damming rivers and
cutting forests.
More specific examples include
Hurricanes, floods, droughts, long winters,
long summers, humans with insecticides
Such events can cause population sizes to
collapse.
In many cases, living things adapt to change.
But is the change is too great or too
sudden, extinction follows as a population
dwindles to zero.
•
•
•