Download Limits to Growth College Biology Mr. Lee Room 320

Limits to Growth
Honors Biology
Facilitator: Mr. Lee
Room 320
Objectives
• Identify factors that limit population growth
• Differentiate between density-dependent and
density-independent limiting factors
Limiting Factors
• Limiting factors cause population
growth to decrease
• Examples:
– Weeds & crop plants competing
for light, space, nutrients in a
vegetable garden
– Predator-prey relationship of a
toad and a mouse
Limiting Factors…
– A limited resources base can
affect the long-term survival of
a species
– Even the human population
may be limited by:
• Availability of food and living
space
• Disease
• Natural disasters
Density-Dependent
Limiting Factors
• A limiting factor that depends on population
size is called a density-dependent limiting
factor
• The factor only becomes limiting when the
population density reaches a certain level
Density-Dependent
Limiting Factors …
• Density-dependent limiting factors include:
– Competition
– Predation
– Parasitism
– Disease
Competition
• When populations become crowded, organisms
compete for food, water, space, sunlight, etc.
• Competition can also occur between members
of different species
– This is a major force behind evolution
– Both species are under pressure to change in
ways that decrease their competition
Predation
• Predation: Predation is the predator-prey
relationship
Parasitism and Disease
• Parasites can limit the growth of a population
• Parasites take nourishment at the expense of their host
• When the host becomes weakened, they are more likely
to contract a disease
Density-Independent
Limiting Factors
• These factors affect all populations
in similar ways regardless of
population size
• Examples are:
• Unusual weather
• Natural disasters
• Seasonal cycles
• Human activities
Review
• Identify factors that limit population growth:
– Limiting factors cause population growth
to decrease
Review…
• Differentiate between density-dependent
and density-independent limiting factors:
– Density-dependent limiting factors
depends on population size
– Density-independent limiting factors affect
all populations in similar ways regardless
of population size
Learn Long
Live Long