Download Intro to Ecology

Community
 A group of
different
populations
that lives in the
same
geographic
area
Community Interactions
 Interactions between organisms
have a huge impact on ecosystems.
Community Interactions
 Types of interactions:
 Competition—when organisms attempt to
use a resource in the same place at the
same time.
 Competitive exclusion principle—no two
species occupy the same niche in the same
habitat.
Predation—an interaction where one
organism captures and feeds on another
organism
More interactions
 Symbiosis—a relationship in which
two species live closely together.
 Usually one species lives on or
inside of another.
 One species always benefits and
other can be harmed, helped, or
have no effect.
Types of Symbiosis
 Mutualism—a symbiotic relationship in
which both species benefit. Ex: Flowers
and the insects that pollinate them.
 Commensalism—a symbiotic
relationship in which one species benefits
and the other is unaffected. Ex:
barnacles on a whale
 Parasitism—a symbiotic relationship
where one species benefits and the other
is harmed. Ex: Fleas, ticks, tapeworms
and their hosts.
Types of Symbiosis
.
The acacia tree and Pseudomyrmex ants are an example of
mutualism
Types of Symbiosis
.
An epiphyte plant is an example of commensalism
Types of Symbiosis
.
A tapeworm is an example of a parasite
Ecological Succession
 Ecological Succession—The series of
predictable changes that occurs in a
community over time.
 As an ecosystem changes, older species
gradually die out and new species move
in.
Types of Succession
 Primary Succession—When succession
occurs on surfaces where no soil exists.
Ex: after a volcanic eruption builds a new
island or covers land with lava rock.
 Secondary Succession—When a
disturbance changes an ecosystem
without removing the soil. Ex: a forest
after a fire.
Succession
 Climax Community—an older,
established community that is no longer
changing (as much)
Populations
 Population Density—The
number of individuals per unit
area
 Ex: number of dandelions per
m2
Population Growth
 Several factors affect population
size:
 Births— # of organisms born
 Deaths— # of organisms that die
 Immigration—The movement of
organisms into a population
 Emigration—The movement of
organisms out of a population
Exponential Growth
 Unrestricted populations of
organisms experience
exponential growth.
 Must have unlimited resources
Exponential Growth Graph
Logistic growth
 As resources become less
available, population growth
slows or stops (birth rate=death
rate) This is called leveling off.
 Carrying capacity—The
maximum number of organisms
that the environment can support
Logistic growth graph
Limiting factors
 Limiting factor—a factor that
causes population growth to
decrease.
Density-Dependent factors
 Density-Dependent factors—
limiting factors whose effects
increase as the size of the
population increases
 Ex: Competition, predation,
parasitism, disease
Density-Independent
factors
 Density-Independent factors—
Limiting factors that affect all
populations in similar ways,
regardless of population size and
density
 Ex: Natural disasters, seasonal
cycles, certain human activities
Human populations
 Demography—The scientific
study of human populations
Exponential Growth in our
human population
 Since the industrial revolution of
the 1800s the human population
has been experiencing
exponential growth.
Effects of increased
growth
 If the human population
continues to grow at an
exponential rate this could
cause:
 Starvation and death for millions
 Some countries to set limits on
birth rates
Slowing population growth
 Human population growth can be
slowed by:
 Global epidemics (influenza, HIV,
etc.)
 Limiting birth rates
Biodiversity
 Biodiversity—the total variety of
organisms in the biosphere.
 It is important to preserve
biodiversity for a variety of
reasons (food webs, new
medicine, etc.)
Maintaining biodiversity
 Humans can help maintain
biodiversity by:
 Enforcing the Endangered Species
Act
 Making laws protecting the
wilderness (including rainforests)
Destroying Biodiversity
 Humans can destroy biodiversity
by:
 Habitat destruction - *** Keystone
species may leave/die so those
below it on food chain are effected
 Introducing invasive species
 (ex: Zebra mussels in Great Lakes,
rabbits in Australia, etc.)
The Greenhouse effect
 The Greenhouse effect—
 Water vapor and greenhouse
gases (CO2, methane, etc.)
trap heat from the sun in our
atmosphere. This keeps Earth
warmer, like the glass panels
of a greenhouse.
Global Warming
 Global Warming—An increase
in greenhouse gases which
increases the amount of heat
trapped in Earth’s atmosphere.
ADD; Specifically CO2
Human activities causing
global warming
 Burning fossil fuels and cutting
down the rainforests are
increasing greenhouse gases
(especially CO2), which is most
likely causing global warming.
Temperatures rise  glaciers melt  sea levels rise
Solutions: Burn less fossil fuels alternative energy sources
Air Pollution
 The quality of our air is important
to our health. Burning fossil
fuels and factory emissions
being released into the air
contribute to air pollution.