1. The scientific study of interactions between organisms and their environment
2. The scientific study of interactions that determine the distribution (geographic
location) and abundance of organisms
Ecological maxims (guiding principles):
1. Organisms interact and are interconnected
2. Everything goes somewhere
3. No population can increase in size forever
4. Finite energy and resources result in trade-offs
5. Organisms evolve
6. Communities and ecosystems change over time
7. Spatial scale matters
Ecological hierarchy: Organism < population < community < ecosystem <
Population: Group of individuals of a species that are living and interacting in a
Community: Association of populations of different species in the same area.
Biotic: living components
Abiotic: physical components
Ecosystem: Community of organisms plus the physical environment.
Landscapes: Areas with substantial differences, typically including multiple
Biosphereall living organisms on Earth plus the environments in which they live.
Adaptation: A characteristic that improves survival or reproduction.
Natural selection: Individuals with certain adaptations tend to survive and
reproduce at a higher rate than other individuals.
Producers capture energy from an external source (e.g. the sun) and use it to
Net primary productivity (NPP): Energy captured by producers, minus the
amount lost as heat in cellular respiration.
Consumers get energy by eating other organisms or their remains How ecosystems work: Energy moves through ecosystems in a single direction
onlyit cannot be recycled.
But nutrients are continuously recycled from the physical environment to
organisms and back againthis is the nutrient cycle.
Ecological Experiments: Design and Analysis:
1. Assignments of treatments and control
3. Random assignment of treatments
4. Statistical Analyses (statistical vs. biological significance)
The process is iterative and self-correcting.
Biological indicators: Amphibians skins are permeable, so they might be early
warning to something in the environment.
Weather: Current conditionstemperature, precipitation, humidity, cloud cover.
Climate: Long-term description of weather, based on averages and variation
measured over decades.
Greenhouse Gases: Water vapor (H O), 2arbon dioxide (CO ), Met2ane (CH )., 4
Nitrous oxide (N 2). Without greenhouse gases, Earths climate would be about
Uplift: Warm air is less dense than cool air, and it risesthis is called uplift.
Three Circulation Cells: Hadley cell (tropic), Ferrell cell (temperate), Polar cell
Prevailing winds: Areas of high and low pressure created by the circulation cells
result in air movements.
The Coriolis effect: The winds appear to be deflected due to the rotation of the
Heat capacity: the number of heat units needed to raise the temperature of a body
by one degree.
Water has a higher heat capacity than landit can absorb and store more
energy without changing temperature.
Semi permanent high and low pressure cell:
Summer: Air over oceans is cooler and denser, so air subsides and high
pressures develop over the oceans.
Winter: Air over continents is cooler and denser; high pressure develops
over continents. Ocean currents affect climate.
The warm Gulf Stream warms the climate of Great Britain and Scandinavia.
At the same latitude, Labrador is much cooler because of the cold Labrador
Downwelling: Where warm tropical surface currents reach polar areas, the water
cools, ice forms, the water becomes more saline and more dense and sinks
Upwelling is where deep ocean water rises to the surface.
Upwelling occurs where prevailing winds blow parallel to a coastline. Surface
water flows away from the coast and deeper, colder ocean water rises up to
replace it. Upwellings influence coastal climates.
Photic zonewhere light penetrates and phytoplankton grow
Upwellings bring nutrients from the deep sediments to this zone, thewe
areas are the most productive in the open oceans.
Maritime climate: Little daily and seasonal variation in temperature, and high
Continental climates: Much greater variation in daily and seasonal temperatures.
Annual Seasonal Temperature Variation: Air temperatures over land show
greater seasonal variation than those over the oceans
Rain shadow: The slope facing prevailing winds (windward) has high precipitation,
while the leeward slope gets little precipitation.
When air masses meet mountain ranges, they are forced upwards, cooling
and releasing precipitation.
Albedocapacity of a land surface to reflect solar radiationis influenced by
vegetation type, soils, and topography.
Loss or change in vegetation can affect climate.
Deforestation increases albedo of the land surface: Less absorption of solar
radiation and less heating. Lower heat gain is offset by less cooling by
evapotranspiration, due to loss of leaf area. Decreased evapotranspiration
results in less moisture in the atmosphere and less precipitation.
Deforestation in the tropics can lead to a warmer, dryer regional climate.
Climatic variation over time: The angle and intensity of the suns rays striking any
point on Earth vary as Earth orbits the sun, resulting in seasonal variation in
climate. Lake Stratification: In temperate-zone lakes, stratification changes with the
In summer, the warm epilimnion lies over the colder hypolimnion. The
thermocline is the zone of transition.
Turnover- The complete mixing of a lake. Occurs in spring and fall when water
temperature and density become uniform with depth.
El Nio Southern Oscillation (ENSO), are longer-scale climate variations that occur
every 3 to 8 years and last about 18 months.
The positions of high- and low-pressure systems over equatorial Pacific
switch, and the trade winds weaken.
Upwelling of deep ocean water off the coast of South America ceases,
resulting in much lower fish harvests.
Long-Term Record of Average Global Temperature- Over the past 500 million
years, Earths climate has alternated between warm and cool cycles.
Warmer periods are associated with higher concentrations of greenhouse gases
Glacial maxima- Earths cool phase- characterized by the formation of glaciers.
Interglacial periods- Earths warm phase- characterized by glacial melting
These glacialinterglacial cycles occur at frequencies of about 100,000 years.
We are currently in an interglacial period; these have lasted about 23,000
years in the past.
The last glacial maximum was about 18,000 years ago.
Milankovitch cycles- the glacialinterglacial cycles have been explained by regular
changes in the shape of Earths orbit and the tilt of its axis. The intensity of solar
radiation reaching Earth changes, resulting in climatic change. The shape of Earths
orbit changes in 100,000-year cycles. The angle of axis tilt changes in cycles of about
41,000 years. Earths orientation relative to other celestial objects changes in cycles
of about 22,000 years
Biomes are large-scale biological communities shaped by the physical environment,
particularly climate. Dominant plant forms, not taxonomic relationships, categorize
Plant Growth Forms:
Deciduous Trees: Moist, seasonally warm/cool or cool/cold on fertile soils or
warm seasonally wet/dry.
Cacti and Shrubs; succulent stems or leaves: Dry, seasonally hot/cool
Needle-leaved evergreen trees: Moist, seasonally warm/cool or cool/cold on
Grasses, sedges: Moist, seasonally warm/cool, with fires.