What is ecology?
“Ecology works at characterizing the patterns seen in nature, studying the complex interactions among organisms and their environments, and understanding the mechanisms involved in biological diversity.”
1. Characterizing the patterns seen in nature
Example: The River Continuum
Many differences are seen between the upstream and downstream stretches of a river
Different types of invertebrates
Different species of fish 2. Studying complex interactions between organisms and their environment
Example: What causes the differences seen between upstream and downstream sites?
Possibilities??? 3. Understanding the mechanisms involved in biodiversity
Why do some reaches of a river tend to have greater diversity than others? Why do some rivers have greater diversity than others?
Why do tropical rain forests and coral reefs have relatively high species diversity compared to other ecosystems? The absolute geographical boundaries of a species are set by abiotic factors
Global scale: Adelie penguins would overheat in the tropics
The absolute geographical boundaries of a species are set by abiotic factors
Local scale: Giant, green anemones are found in pooling water in the intertidal, but not on vertical rock faces Within limits set by abiotic factors, biological interactions affect the presence abundance of species
What are some of these biological interactions? Why are there no polar bears in the Antarctic? Shelford’s law of tolerance
What do the axes mean? What do different parts of the curve tell us about the species? Winter distribution of the Eastern phoebe:
Blue line: -4º isotherm, minimum average temp. January
Blue patches: Deviation of phoebe distribution from -4º isotherm. Seasonal or geographical shifts in tolerance
What do the three different curves represent? ( 1 possibility)
What does the arrow represent?
What types of values belong on the x-axis? How might natural selection affect a species’ tolerance curve?
Within a single generation?
After several generations? Global Climate
Change and Species
Diagram from Bellarmine
University website Biomes as related to Temperature and Moisture Global Distribution of Terrestrial Biomes What causes the poles to be colder than equatorial regions?
Key reason: Curvature of the earth and resultant angle of sun’s rays [Fig. 2.7a] Which other factors mediate the distribution of global temperature?
Earth’s rotation Æ air and ocean currents that affect the distribution of heat energy
Earth’s tilt (angle of axis) (Precession)
Albedo (Reflectivity) Movement of air masses
If the earth had no rotation: Movement of air masses
With rotation: Ocean circulation patterns and heat distribution
Example: Effect of the Gulf Stream on temperatures (E.
North America; W. Europe) The angle of the earth’s axis is responsible for seasonal variations on the earth.
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Position shifts between summer and winter (why?) Albedo: reflectance of solar radiation
Snow and Ice: high albedo
(Photo: K. Haberman)
Forested areas: low albedo
Photo: Natl. Park Svc. Global patterns of precipitation Global patterns of precipitation
Warm air holds more moisture than cold air
Warm air rises and cools, dropping moisture close to where it was picked up, so moist areas tend to remain moist, and dry areas tend to remain dry
Warm, dry air picks up additional moisture… Altitude and Rain shadows North vs. south facing slopes North vs. south facing slopes (cont.) Microclimate example: Effects of vegetation on temperature Nutrients
Examples: C, H, N, O, P, Ca, Mg, K, S, Na, Cl
Examples: Fe, Mn, B, Co, Cu, Mo, Zn, I, Se Global distribution of productivity in the ocean Upwelling Focus on light
Characteristics that vary with climate/microclimate
directionality Light energy as a function of latitude and time of year PAR: Photosynthetically active radiation (400-740 nm) Attenuation of light through water Attenuation of light through vegetation
Leaf area index Attenuation of light through vegetation (cont.) Other key factors
Example: Different estuarine species are tolerant to different conditions
Example 1: Surface waters vs. sediments in an estuary
Substrate (i.e. soil type, rocky vs. muddy river bottom, etc…)
Example: Distribution of macroinvertebrates in streams.