Transcript SNC 1D Ecology populations

Populations and Resources
Population
Is a group of organisms of one species
that lives in the same place, at the
same time, and can successfully
reproduce.
Example: Elephants.
Exponential Growth
Accelerating growth
that produces a J-like
curve when the
population is
graphed.
Only occurs for short
periods in nature
Usually when the
organism has a lot of
resources.
Limiting Factors
Exponential growth cannot be
sustained in nature because no
ecosystem has an unlimited supply of
resources.
These restrictions are called limiting
factors.
Abiotic limiting factors: temperature,
pH, oxygen, light, hiding places
Biotic limiting factors: food, etc.
Carrying Capacity
Is the size of a population that can be
supported indefinitely by the resources and
services of an ecosystem.
When a population is maintained at its
carrying capacity, it is at an equilibrium or
balance.
There is an equal amount of organisms being
born or moving into the ecosystem as there
are dying or leaving.
Graphing Carrying Capacity
Humans and Carrying Capacity
Humans alter natural ecosystems often,
causing a change to carrying capacities.
Urban sprawl is the growth of relatively lowdensity development on the edges of urban
areas.
Human population in the Golden Horseshoe
is expected to increase by 3.7 million
between 2005 and 2031. How do we make
room for all these people without affecting
other ecosystems?
Ecological Niche
As species go about their daily
activities, they interact with other
species.
An ecological niche is the way an
organism occupies a position in an
ecosystem, including abiotic and biotic
factors.
Example: brown bat
Biotic niche: insects
that it eats, its
competitors like the
nighthawk, and its
predators.
Abiotic niche: place
for roosting and
hibernation, the time
of night it hunts,
airspace it flies in,
the temperature
range it can live at.
Population Regulation
Predators: organism that kills and consumes
other organisms
Prey: is eaten as food by a predator
Bottom-Up Population regulation: a shortage
of plant resource at the base of the food
chain causes declines in the animals in the
higher trophic levels.
Top-Down Population regulation: more
rabbits in a population, lead to more coyotes
to eat them, then more coyotes lead to fewer
rabbits.
Competition
Competition occurs when 2 or more
organisms compete for the same
resource.
Can limit size of population
Can influence the ecological niche of
an organism
Symbiosis
Mutualism: 2 species benefit from the
relationship
Example: algae lives in coral. The algae
gives the coral energy and the coral gives
the algae protection and carbon dioxide.
Parasitism: when an organism benefits
at the expense of a different organism.