Download Ecology Notes 2 - Succession and Populations NEW

Changes Over Time
• Ecological Succession – natural changes and
species replacements in communities of an
ecosystem
• Occurs in stages as different species create
conditions suitable for some species and
unsuitable for others
• Often difficult to observe
– can take decades
In the beginning…
• New land can be created or exposed where
no life existed before
– Lava destroying all life in its path and forms new land
– An avalanche exposes new areas and ledges
– A city street has never before had life growing from it.
• New communities of organisms colonizing these areas
is called Primary Succession
• The first species in the area are called Pioneer Species
– Example: Lichens (can grow without
soil on rocks and other surfaces)
And then…
• Pioneer organisms die and become
the first patches of soil
• The presence of soil allows weedy
plants to emerge, and over time
vines, shrubs, and trees appear
• When this primary succession
slows down and the community
becomes stable
• This mature community undergoing
little or no change is called the
Climax Community.
From Pioneer Species to Climax
Community
Disaster Strikes…
• When natural disaster or human
actions disrupt or destroy a
community, the following community
changes are called Secondary
Succession
• Like Primary Succession, the
communities of organisms
gradually change
• Unlike Primary Succession, this
occurs where there was once life and
on land that contains soil
Secondary Succession
• Because there is soil
– Pioneer Species will be different from the Primary
Succession
• Example: Lichens were pioneers in Primary where
wildflowers may be pioneers in Secondary
– Secondary Succession will take less time to reach
Climax Community
• Though Pioneer Species may be different, the
Climax Community will most likely be similar if
the climate it the same.
Secondary
Succession
Population Growth
• What is Population
Growth?
– An increase in the
size of a population
over time
• Some things exhibit
Linear Growth
– As time goes by, growth
occurs at a steady rate
– when graphed, it is a
straight line
How do Populations Grow?
• Populations show a J-shaped
curve
• Initial increases are slow, but
as the population gets larger,
it grows faster
– Why?
• There are more organisms
available to reproduce
• This pattern is called
Exponential Growth
Can it go on Forever?
• Eventually, population growth will be affected
by limiting factors
– Such as: availability of food and space
• The number of organisms an environment can
support is called the Carrying Capacity
• In time, the population
growth will level off making
an s-shaped curve
Environmental Limitations
• Two main types of Limitation Factors
– Density-Dependent
– Density-Independent
• Density-Dependent Factors have an increased effect
as population increases (more organisms, more risk)
–
–
–
–
Disease
Competition
Parasites
Predation
Environmental Limitations
• Density-Independent Factors affect all populations
regardless of their density
(more organisms, same risk)
– Temperature
– Storms
– Natural Disasters
• (floods, hurricanes, etc)
– Drought
– Habitat Destruction
– Pollution
• Most are abiotic factors
Organism Interactions: Predation
• The number of
predators affects the
prey population
– More predators, more
risk to prey
• The number of prey
affects the predator
population
– More prey, more
food for predators
Organism Interactions: Competition
• Competition – a density-dependant factor
– Organisms within a population must compete for resources
– If population numbers are low, resources are plentiful
– When populations grow, resources are in higher demand
• If demand is greater than supply……population must
decrease
– Fight and kill each other
– Reproduce less
Human Activities vs. Earth’s Processes
• Human populations have a carrying capacity as well.
• To have a sustainable population, there needs to be a
balance between the Earth’s resources, the needs of
humans, and the needs of other species on Earth.
• Factors that affect human population sustainability are:
– Population growth
– Technology
•
•
•
•
Agricultural
Industrial
Alternative Energy
Building Roads and Bridges
– Resource Consumption
Population
• Population growth world-wide has
grown exponentially and is expected to continue to do so.
• Population growth will naturally slow down as it nears its
carrying capacity due to an increase in the death rate and a
decrease in the birth rate as a result of:
– Food and water shortages
– Pollution of the environment
– Spread of diseases
• An increasing population can have an effect on:
–
–
–
–
the amount of available clean water
the amount of waste that is produced
the amount of available fertile soil for agriculture (food resources).
Impacting animal habitats and migratory routes
Technology
• Technology applies scientific knowledge to help meet the needs of
humans. These technological advances in agriculture, industry, and
energy can have a positive or negative impact on Earth.
Agricultural technology
Positive: Improved Technology
More Food Produced
Negatives: Pollution
Less Diversity in Crops
Consumes Energy
Industrial Technology
• Advances in industrial technology have changed the
world and have lead to developments in
communication, transportation, and industry.
• The development of certain chemicals have contributed to the
depletion of the ozone layer, which results in increased
ultraviolet rays reaching Earth.
• Technological advances have revolutionized the
communication industry; however, the disposal of outdated or
damaged equipment is becoming an increasing concern.
• The burning of fossil fuels for industry and transportation:
– increases the greenhouse gases
– produces acid rain
Technology
Alternative energy technology
• Using natural renewable energy sources (such as wind,
water, geothermal, or solar energy) decreases the
burning of fossil fuels, which increases the quality of
the atmosphere and the cycles involved.
• Using nuclear energy technology provides an
alternative energy source that does not impact the
atmosphere. However, the waste produced from
nuclear energy use is becoming an increasing concern.
Resource Consumption
• As the population increases and
technology expands, the demand for
Earth’s limited supply of resources
also increases.
• Some resources (such as food, clean water, and timber)
are considered renewable resources, those that can be
produced at roughly the same rate that they are
consumed.
Resource Consumption
• Other resources, such as fossil fuels, are nonrenewable
resources, those that cannot be produced at the same
rate that they are consumed. For example,
• Sustainable use of resources can be accomplished by reducing
consumption, reusing products rather than disposing of them,
or recycling waste to protect the environment.