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– Ecology is the study of interactions among organisms and their environment.
– Ecosystem is a community (all the organisms in a given area) and the abiotic
factors (such as water, soil, or climate) that affect them.
– Stable Ecosystem – populations fluctuate at a predictable rate, supply of
resources fluctuate at a predictable rate, energy flows through the system
– Limiting factors – any abiotic or biotic factor that limits the numbers,
reproduction, or distribution of an organism
– Biotic – animals, plants, bacteria, etc.
– Abiotic – water, soil, temperature, etc.
Community Interactions
– Competition occurs when more than one organism
uses the same resource at the same time.
– Predation is when one organism eats another
– The organism being eaten is the prey.
– The organism that eats is the predator.
– An ecological niche refers to the role of an organism in its environment
including type of food it eats, how it obtains its food and how it interacts
with other organisms.
– Two species occupying the same niche will have to compete for resources.
They will not be able to coexist.
Some organisms enhance their
chances of surviving by forming
symbiotic relationships
– Commensalism
– Mutualism
– Parasitism
– Parasitism is a symbiotic relationship in which one organism (the parasite)
benefits at the expense of the other organism (the host).
– Some live in or on their host
– Ex: Cowbird/Other birds, Mosquito/Mammals, tapeworms/mammals
– A symbiotic relationship in which both species benefit.
– Ex: ants/acacia tree, flowering plants/pollinating insects, wood digesting
– A symbiotic relationship in which one species benefits and the other species is
neither harmed or benefited.
– Ex: Spanish moss/tree, barnacle/whale
4-1: Understanding Populations
– Properties:
– Size - number
– Density – number/area
– Dispersion:
– Clumped – when food or resources are clustered
– Even – defined territories (chemicals or protection)
– Random – seed dispersal by wind or birds
Population Ranges
– Depends on abiotic and biotic factors
– Some are specialized to only certain locations
– Iiwi – live only in Hawaii
– Some may be able to live in larger areas
– Peregrine falcon – live on all continents except Antarctica
Population Regulation
– Limiting factors that affect population size:
– Density-independent factors
– and
– Density-dependent factors
Density-dependent factors – reduce
population due to an increase in
population size
Examples include mostly biotic factors that
cause a shortage of resources (food, shelter,
nesting sites, etc.):
Density-independent factors – reduce
population by same degree no matter
population size
Examples include mostly abiotic factors:
seasonal cycles
clear cutting forests
pollution, etc
Changing Environment
– Environments are constantly changing, so organisms must be able to
survive a range of conditions.
– How well an organism can survive different conditions (i.e.
temperature & pH) can be shown on a tolerance curve
– Range of tolerance – the upper and lower
limits that the organism can survive in
Tolerance Curve for Cutthroat Trout –
Shows they can tolerate temps between
5 and 23°C
– some organisms can change their tolerance to abiotic factors by becoming
acclimated to the new condition
– for example, if you raised the temperature of a goldfish bowl a degree
every week, your fish might be able to tolerate higher temperatures than
other goldfish
Ecological Succession: Natural changes
and species replacements that take place in
a community over time.
Primary Succession
– Colonization of NEW land (no soil) that is exposed by avalanches, volcanoes, or
glaciers to pioneer species (such as lichens and mosses). Pioneer species develop
the soil that is the colonized by other plants.
Climax Community
–A stable community that undergoes
little or no change in species.
Secondary Succession
– Sequence of changes that take
place after a community is
disrupted by natural disaster
(fire or hurricane) or human
actions. (soil present)
– Occurs in all ecosystems
– Forest
– Pond
– Coral reef
– Desert
Geochemical Cycles
– The energy in organisms comes from sunlight. Sunlight is an
infinitely available resource.
– The materials organisms are made from (water, carbon,
nitrogen) are not constantly replenished like sunlight.
– These materials have been recycled by the Earth since life
Carbon Cycle
– Carbon and is cycled from an abiotic factor to existing within biotic parts of the
environment and back to abiotic through photosynthesis, respiration,
decomposition, combustion, and erosion/weathering of limestone rock.
CO2 + H2O + energy(light)
C6H12O6 + O2 + H2O
C6H12O6 + O2 + H2O
CO2 + H2O + energy(ATP)
Carbon Cycle
Nitrogen Cycle
– Nitrogen is an element necessary to building proteins.
– Nitrogen (N2) is abundant in the atmosphere but cannot be
used by plants in that form.
– Nitrogen fixation - Bacteria in the soil “fix” the nitrogen so
plants can use it.
– The nitrogen enters the soil through animal waste and
– Denitrification - Denitrifying bacteria break down the nitrogen
compounds in the soil and
release nitrogen into the atmosphere.
bacteria return
nitrogen to the
– The Air is 78% nitrogen but plants can’t use it.
Water Cycle/Hydrologic
– Drinking water, transpiration, respiration, photosynthesis,
and elimination are biotic contributions to the water cycle.
– Transpiration – evaporation from leaves of plants.
4/164155/00044678.html (Water Cycle Brain Pop Video)
Human Impact
– An increasing population effects
the amount of available clean
– An increasing population has an
effect on the amount of waste that
is produced.
– If clean water is being depleted at
a greater rate than it can be
purified, it is not considered
– More waste is produced than can
be managed effectively.
– Some waste products require
complicated and costly means for
removal once they are introduced
into the environment.
– An increasing population can have
an effect on the amount of
available fertile soil for agriculture
(food resources).
– Soil is often lost when land is
cleared, making the land
unsuitable for agriculture.
– Demand for land (for agriculture
or habitation) has led to
– As forests are cut down, there are
fewer trees to absorb atmospheric
carbon dioxide. The increase in
atmospheric carbon dioxide
contributes to global warming.
– Deforestation can increase the
rate of erosion and decrease the
rate of soil generation.
Earth’s Atmosphere
– Ozone comes from
oxygen produced from
– It blocks a large amount
of radiation from the sun
Burning of Fossil Fuels
– Increases the greenhouse gases released in the
atmosphere (carbon dioxide).
– Increases global temperatures (global warming) that
affect sea levels, climate, and atmospheric composition.
– Produces acid rain (pollutants in the air combining
with water to cause the normal water pH to be
– Acid rain decreases the pH of the soil and aquatic
– Can leach nutrients from soils or destroy plant life and
affect the types of organisms that can survive there.
Global Warming
– Earth’s temperature depends on how much of the sun’s radiation
enters the atmosphere and how much escapes back into space.
– The greenhouse effect
– Greenhouse gases (carbon dioxide, oxygen, methane, and water vapor) trap
sunlight that normally reflects back into space.
– This increases the temperature of our planet (global warming).
Amount of CO2 in the
Greenhouse effect
Average Global Temperature
Plant cover on
Rate of photosynthesis
Amount of CO2
absorbed by plants
Amount of CO2 in the
Greenhouse effect
Blue Line =
Average Global
Red Line =
Atmospheric CO2
Human Populations & Impact
– Population Growth Rate
– Birth rate
– Death rate
– Immigration rate (movement into a population)
– Emigration rate (movement out of a population)
– (Birth + immigration) – (death + emigration) =
Growth Rate
– If growth rate is negative, population is decreasing
– If growth rate is positive, population is increasing
Linear Model
population increases by a specific increment
each time.
Getting paid per hour at work
Exponential Model – J Curve
– Describes a rapidly growing population after
a few generations
– Assumes birth and death rates are constant
– Makes a J-shaped curve on a graph
– Limitations to the model:
– Limiting factors – factors that restrict population
– Food, space, resources, competition, etc.
Logistic Model – S Curve
– Builds on exponential model, but takes
limiting factors into account
– Knows birth rates decline and death rates
increase as the population size increases
– Determines the carrying capacity (K) – the
number of individuals a population can
support over a long period of time
– Makes an S-shaped curve on a graph
– Assumes carrying capacity is constant
Human Population Growth
– Hunter-gatherer Lifestyle
– Small nomadic populations
– High mortality rates among young
– Slow population growth
– Agricultural Revolution
– Began to domesticate animals and cultivate food
– Stabilizing and increasing food supplies
– Population increased faster
Human Population Growth
– Population Explosion:
– Bubonic plague (1347-1352) – decreased 25% of
European population
– Acceleration of population growth after 1650, due
to a decrease in death rates with:
– Increased sanitation and hygiene
– Disease control
– More food available
– Better economic conditions
Human Population Growth
– Global growth rate at all time high in the
1960s at 0.021 per capita
– Growth rate is slowly decreasing due to a
decrease in birth rates (currently at 0.014)
– Sample problems:
– 1970 had 3.7 billion people with rate of 0.0196
– 1999 had 6 billion people with rate of 0.014
– October 31, 2011 – 7 billion people worldwide
Population Today
– Developed countries – modern, industrialized
– United States, Japan, Germany, France, the United
Kingdom, Australia, Canada, and Russia
– 20% of population w/ growth rate of 0.01 per capita
– Undeveloped countries – poorer
nonindustrialized countries
– Most of Asia, Central America, South America, and
– 80% of population w/ growth rate of 0.02 per capita
Population Dynamics
– Dynamic – change in size and composition over time
– Birth rate
– Death rate (mortality rate)
– Life expectancy
– Age structure
– Patterns of mortality
– Demography – study of human populations
– Biodiversity – variation of living things in an area
– Genetic diversity – variation of genes in a population
– Species diversity – variation in the number of species in an area
– Ecosystem diversity – variation of ecosystems within the biosphere
– Extinction – the complete loss of a species
Importance of Biodiversity
– Economic value
– Provides medicines and shelters
– Provides food, clothing, energy,
– Aesthetic value
– Beauty
– Scientific value
– Useful information to study
Factors that Threaten
– Overexploitation – excessive use
– Habitat loss
– Destruction of habitats
– Disruption of habitats
– Keystone species – important species for the ecosystem
– Fragmentation of habitat
– Edge effects
Factors that Threaten
– Pollution
– Biological magnification – increasing concentration of toxicity
as you go up the food chain
– Acid precipitation
– eutrophication
– Introduced Species
Conserving Biodiversity
– Maintain Natural Resources
– Renewable resources – replaced faster than consumed (Ex. Solar energy)
– Nonrenewal resources – used faster than replaced (Ex. Fossil fuels)
– Sustainable use – using materials at a rate where they can be replaced or
Conserving Biodiversity
– Protecting Biodiversity
– Protected areas in US
– National Park System
– Protected areas Internationally
– 7% of land areas are reserves
– Biodiversity Hot Spots
– Areas with endemic species which are not found anywhere else
– Corridors between habitat fragments
Conserving Biodiversity
– Restoring Ecosystems
– Bioremediation – use of living organisms to clean an area that is polluted
– Biological Augmentation – adding natural predators to keep species in
– Legally Protecting Biodiversity
– Endangered Species Act
Human Carrying Capacity
 Scientists are concerned
about the human
population reaching or
exceeding the carrying
 An important factor is the
amount of resources from
the biosphere that are used
by each person.
Human Population Growth
– Population growth world-wide has grown
exponentially. It is predicted that the population will
continue to grow at a rapid rate.
– As humans reach Earth’s carrying capacity population
growth will slow 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
Humans are the only species that
can change its carrying capacity
through the use of technology.
– Technology is the application scientific knowledge in order to find
solutions to problems or develop products to help meet the needs of
– Technology has also contributed to the pollution of the air, water, and