Ecology of Populations
Our
Environment
Humans are part of the Earth’s
natural ecosystems. We depend
on our planet for food, clean
water, clean air to breath, and for
living space. Humans need to be
careful to preserve our
ecosystems because our
existence depends on it!!
Population Growth
• The Earth can sustain a certain number of humans
on this planet and we need to find a way to slow
population growth before the earth’s carrying capacity
is reached. If we exceed the carrying capacity, future
generations will suffer from famine, disease, high
pollution levels, and wars over limited resources.
Watch
video!!
Age Distribution
Age-Structure Diagram shows growth
patterns of populations grouped into
categories
Horizontal axis = Number of individuals
Human Age Distribution
Developed countries
Less-developed countries
Humans are part of the Earth's
ecosystem. Human activities can either
deliberately or
inadvertently alter the balance of an
ecosystem. Once ecosystems are
damaged, people may suffer from that
damage just like any other species.
Most species in new environments will have a period of
rapid population growth. Then the population growth will
slow as the population number approaches the carrying
capacity. The carrying capacity is the number of
individuals the environment can support. Available
resources such as food and water will decrease, while
the pollutants and wastes of the population will rise as a
population approaches the carrying capacity.
What do you Think???
How do human
activities affect the
environment?
Human Impacts on the Environment
Global warming
Use of machinery by
humans seems to be
increasing CO2 levels
in the air. CO2
prevents heat from
escaping, causes
slight world wide
temperature
increases
Rising water temperatures
causes coral bleaching
Human impacts on the
environment
Deforestation
• Caused by demand for wood products,
need for space, farmland, housing,
roads
• Deforestation causes
habitat fragmentation
Animals and plants are forced
into confined areas
Habitat Fragmentation
Habitat Fragmentation
Pollution:
• Agricultural
–DDT
–Fertilizers
–Animal wastes (nitrogen)
• Homes
–Strong cleaning agents
• Industry
–Toxic gases and wastes
–Acid rain
Human impacts on the Environment
Ozone depletion
• Caused by aerosol chemicals called
chlorofluorocarbons (CFCs)
• CFC’s
– Escape into atmosphere, reacts
breaking down the ozone (O3, a
protective atmospheric layer)
– UV rays penetrate the atmosphere
and
cause harm to many organisms
“HOLE” in
the ozone
(O3)
Human impacts on the
Environment
Fishing activities
•
Demand for fish and shellfish
• Commercial Fishing be harmful to
environment in many ways
Human impacts on the environment
Invasive species (EXOTIC SPECIES)
•introduced by people accidentally or
intentionally
• Can cause problems if no natural enemies
are present
Cane toad was
introduced to Australia
to control cane beetles,
pest insects that destroy
sugar cane crops
Human impacts on the Environment
Exotic pet trade
• Capture and sell wild animals from
exotic locations
• Wealthy buyers and collectors desire
obscure animals
• Animals removed from their habitat
causes an imbalance in the ecosystem
Importance of the Environment
Biodiversity = Many
different types of
organisms
• Organisms depend
upon one another
• Interfering with one
Organism can have a
Ripple effect to many
w/in the habitat. What
happens when a top
predator is removed?
Importance of the environment
Natural resources:
Non-renewable- resources that
we use that cannot be replaced.
Includes fossil fuels (petroleum,
coal),metals (aluminum, iron),
minerals (silicon)
• Renewable- Resources that
can be replaced in a relatively
short amount of time. Includes
animals, plants, water, wind, etc.
– even renewable resources
can run out
Importance of the Environment
Natural resources
Renewable energy sources include
wind power, geothermal energy,
ocean currents
Preserving our resources
• Increasing our use of
renewable resources
could mean that they
become nonrenewable.
For example, polluting a
lake so that no one can
drink the water or
removing so many fish
through commercial
fishing that they are
unable to find each
other to reproduce to
restore their numbers.
Individuals can help
maintain our supply
of both renewable
and nonrenewable
resources by
practicing the 3 R’s
Stewardship:
Natural Processes in
Ecosystems
• Maintaining air quality- rainfall helps
clean particles from the air and it keeps
the air moist. The carbon- oxygen cycle
of photosynthesis and respiration keep
levels of oxygen and carbon dioxide at
acceptable levels for life.
• Humans affect the air by polluting it with
products of combustion (burning of
fossil fuels) and other industrial gases.
Carbon – Oxygen Cycle
• Soil Formation- soil forms when weathering breaks
down rock and when dead and decaying material
accumulates. Soil promotes the growth of many
producer organisms and serves as a habitat for
animals and decomposers too. Root systems hold
the soil in place.
• Human or grazing animals remove vegetation and
the soil is washed away by rain or blown away be
wind. This is called erosion. We lose much fertile
topsoil this way.
The Water Cycle- Through the water cycle fresh, clean
water is made available for all organisms.
Humans can pollute the water to the extent that the
natural recycling methods do not clean up the water
fast enough and the water becomes unusable.
Benefit of decomposers
Waste removal and Recycling of Nutrients- Plants use
the minerals in the soil as they grow. Animals eat the
plants and the energy that the plants produced gets
passed from organism to organism through the food
chains and food web. When a body dies or creates
wastes, decomposers break down the remains. The
nutrients are returned to the soil, making the soil fertile
again for the plants in the area. If an area had no
decomposers, the nutrients would be “locked up” in the
wastes of and remains of
organisms. The soil would
lose fertility and soon plants
would not be able to grow
there.
• In the rain forest, the rates of decomposition and
nutrient uptake by plants have to happen very
rapidly or the rain will wash the nutrients away.
When people cut down or burn the rain forest, the
rain depletes what nutrients are in the soil rapidly
and the land becomes useless.
• Humans can make compost, (a mix of decaying
lawn and garden wastes) which is a natural
fertilizer. We can make the soil around our home
more fertile by spreading compost.