BIOB50H3 Chapter L#3: lecture #3 reading
CHAPTER 2,3 READINGS (Lecture #3 Readings) – pg 22-28, 31-37, 50-78
- Grizzly bears in Pacific Northwest eat salmon (that arrive to
reproduce in the streams of the region) salmon are
anadromous: born in freshwater streams, spend adult lives
in ocean, then return to spawn in their freshwater habitats
where they were born
- Dams, stream sediments, water pollution, overharvesting
have all been blamed for declines in salmon population
Studies have focused on deterioration of freshwater
habitat as cause for declines in salmon
Steven Hare and Robert Francis suggested changes in
marine env. Are contributing to declines in salmon
abundance hypothesized that abrupt-shifts in salmon
production were associated w/ long-term climate
variation in the North Pacific
oMantua found correspondence between shifts
in salmon production and changes in sea surface
temp. in North Pacific
INTRODUCTION
- Physical env. Is ultimate determinant of where org. can live, what resources they can
use, and what rate their pop. Grow physical env. Include: climate (temp., wind, and
precipitation over long period of time; ultimately driven by solar radiation), chemical
composition (eg. Salinity, acidity, [ ] of gases in atmosphere and in water), soil
CLIMATE (2.1)
-Weather: the current temp. humidity, precipitation, wind, and cloud cover important
determinant of our behaviour (eg. What we wear, type of transport etc.)
-Climate: long-term description of weather at a given location, based on avg. and
variation measured over decades includes the daily and seasonal cycles associated w/
changes in solar radiation
Also includes changes over years (eg. Large-scale cyclic-weather patterns related to
atmosphere and oceans)
L-T climate change occurs b/c changes in the intensity and distribution of solar
radiation reaching Earth’s surface (+ changes in the overall energy balance)
Earth’s climate is changing increase in conc. Of CO2 absorb energy and radiate it
back to Earth’s surface greenhouse effects
Climate controls where and how organisms live
- Geographic distribution and org. function is determined by their climate eg. Temp
affects biochemical rxns and physiological activity for org. // eg. Precipitation
freshwater org. are dep. On precipitation for the maintenance of their habitats // eg.
Marine org. depend on ocean currents
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- Geographic distribution of
org. are influenced by
extreme conditions b/c
extreme events are
important determinants of
organism mortality
Eg. Long drought in US
led to deaths of pinion
pines
Thus physical env. Must
also be characterized by
its variability over time
and not just by avg.
conditions if want to
understand its ecological importance best
-Timing of changes in physical env. Are also important eg. Seasonality of rainfall (eg.
Rainfall determines availability of water for terrestrial organisms, eg. Regions w/ a
Mediterranean climate system wet seasons, dry seasons dry seasons can promote
forest fires, limits growth of some plants)
- Climate also influences rate of abiotic processes that affect org. (eg. Rate at which rocks
are broken down to supply nut. To plants and microorganisms determined by
climate)
Also influences periodic disturbances: eg. Fires, floods, avalanches
Global energy balances drives the climate system
- Energy is derived from solar radiation top of Earth’s atm. Receives 342 Watts of solar
radiation p/m2 yearly 1/3rd is reflected back by aerosols, 1/5th is absorbed by ozone,
clouds and water vapour, ½ is absorbed by Earth’s water and land
- If want temp. to remain same, energy gains from solar radiation must be balanced by
energy losses must radiation absorbed by Earth’s surface is infrared radiation
(longwave radiation)
Surface also loses energy through evaporation called latent heat flux
Heat is also transferred through the exchange of kinetic energy by molecules in
direct contact w/ eachother (conduction) and by the movement of air/water
(convection)
oEnergy transfer from warm air above earth’s surface to cooler atm. By
convection and conduction is called sensible heat flux
- Atm. Absorbs lots of infrared radiation from earth’s surface and reradiates it back to
Earth’s surface major energy gain greenhouse gases do this (eg. Water vapour, CO2,
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CH4, N2O; some made by biological activity and w/o them, Earth would be much cooler
than it is right now)
ATMOSPHERIC AND OCEANIC CIRCULATION (2.2)
- @ equator, Sun rays strike earth perpendicularly,
towards poles, angle is steeper so same amount of
energy is spread over a progressively larger area
also passes through more atmosphere, and thus
more is reflected/absorbed before it reaches
surface
othus: more solar energy is received p/unit
area in tropics, than in poles
- differential input of solar radiation creates a
latitudinal gradient in temp. and also drive
warm/cold fronts and large storms
- movement of earth on its axis also results in changes
in the amount of sunlight received over course of the year cause seasonal climate
variation
Atmospheric circulation cells are established in regular latitudinal patterns
- surface warmed by sun emits infrared radiation and warms the air above it
differential warming creates pockets of warm air surrounded by cooler air warm air is
less dense (fewer molecule p/unit volume) than cold will rise (as long as cold air
surrounds it) called uplift
-atmospheric pressure: force exerted by molecules of air on the air and the surface
below it (pressure decrease w/ increasing altitude as warm air rises, it expands and
cools) b/c cold air can’t hold as much water vapour condenses forms clouds
condensation of water into clouds is a warming process (a form of latent heat flux)
keeps pocket of air warmer than surrounding atmosphere and enhances its uplift
(despite its cooling)
owhen there’s substantial heating of surface and cooler atmosphere above
surface uplifted air will form wedge-shaped tops clouds reach the
boundary between the troposphere and the stratosphere (marked by a
transition from cooler temp. in troposphere to hotter temps in
stratosphere)
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Document Summary
Chapter 2,3 readings (lecture #3 readings) pg 22-28, 31-37, 50-78. Dams, stream sediments, water pollution, overharvesting have all been blamed for declines in salmon population. Studies have focused on deterioration of freshwater habitat as cause for declines in salmon. Steven hare and robert francis suggested changes in marine env. Is ultimate determinant of where org. can live, what resources they can use, and what rate their pop. Include: climate (temp. , wind, and precipitation over long period of time; ultimately driven by solar radiation), chemical composition (eg. salinity, acidity, [ ] of gases in atmosphere and in water), soil. Weather: the current temp. humidity, precipitation, wind, and cloud cover important determinant of our behaviour (eg. what we wear, type of transport etc. ) Climate: long-term description of weather at a given location, based on avg. and variation measured over decades includes the daily and seasonal cycles associated w/ changes in solar radiation.
