Part 2 Required Readings Flashcards
Why Ecology Matters, SFE pt4,
What are the two main limiting factors of the geographic distribution of most species of animals and plants?
geography and climate
Changes in historic geographic ranges are now being caused by two main processes:
human introductions and climate change
What is the effect of barriers on dispersal movements?
they prevent dispersal movements, in particular the movement of an individual from its place of birth to a new place for breeding and reproduction
Describe how transplant studies work
Move the organism to a new area. If it survives there and reproduces, you have good evidence that the former distribution was restricted by a lack of dispersal.
Give two examples of deliberate introduction of pest species
- The European Starling (Sturnus Vulgaris) has spread over the entire US and much of Canada within a period of 60 years.
- The cane toad (Rhinella marines) was brought to Australia where it failed to control any insect pests and became a pest itself
If more individuals of a species are introduced….
the species will be more likely to survive and colonise the island.
What are the four major steps of the invasion process? At which step can this process fail?
Transport, establishment, spread, and impact
The invasion process can fail at any of these four steps.
Why may transplants or movements of plants and animals into a new area fail?
- Biological environment may eliminate the newcomer
- Physical-chemical environment may be lethal to the organism and prevent it from reproducing
List the 4 geological processes that may cause changes in distributions for any particular species
- Dispersal limitation: the species is absent because it has not been able to move to an area
- The species does not recognise the habitat as suitable
- Other species prevent colonisation (parasites, predators, pathogens)
- Limiting physical or chemical factors (temperature, water, oxygen, soil, pH)
Describe the simplest model for climactic limitation
geographic ranges for all species should be shifting poleward
How will stream fish react to water temperatures rising?
they will tend to move upstream to stay within their temperature zone
what is the environmental variable most important to organisms?
temperature
what does the latitudinal gradient in temperature arise from?
- the uneven distribution of radiant electromagnetic energy that is blasted at the earth from the sun
- the spherical shape means that the sun’s rays strike the earth at different angles at different latitudes
describe how photon density per unit area of the earth changes as we move towards the poles
it declines because the angle of incidence declines from 90 to 0, eventually reaching a tangent
how does seasonal variation in climate arise?
- the earth’s axis is tilted at about 23.5 off the vertical.
- as it makes its annual revolution, different parts of the earth experience the sun as being directly overhead at noon
at the spring and autumn equinoxes
sun is directly above equator
at the northern hemisphere’s summer solstice
sun is directly over 23.5N
at the northern hemisphere’s winter solstice
sun is directly over 23.5S
the latitudinal lines around the earth at 23.5N and 23.5S are called
Tropic of Cancer and Tropic of Capricorn respectively
solar equator
line of latitude closest to the sun
how does the solar equator change through the year
it oscillates between the two tropic lines, making one cycle per year
tropical region
belt bounded by Tropic of Cancer and Tropic of Capricorn
how does solar light energy transfer so much heat to the earth?
- when lights hit solid surfaces, they are absorbed and reradiated at longer, IR wavelengths
- light is converted to heat
- IR radiation (unlike light) is absorbed by the atmosphere
- solar energy heats the earth’s surface and then the surface heats the air near the surface
what is atmospheric circulation caused by?
solar heating of the bottom of the atmosphere
define atmospheric circulation
the large-scale movement of air and together with ocean circulation is the means by which thermal energy is redistributed on the surface of the Earth.
what is the earth’s atmosphere?
a relatively thin layer of gases that is pressed against the earth by gravity
Hadley cells
- equatorial region of earth’s surface heats up the most
- IR radiation from the heated surface in turn heats up the near-surface atmosphere, rendering the air less dense
- this reduction in density (1) causes a meterological low pressure zone (2) impels heated air to rise above the solar equator
- as the air rises, it creates a partial vacuum beneath it, and that suction causes surface air to be drawn toward the solar equator from the N and S
- that new air also heats up and rises
- this sets up a continuous flow
- the air bumps up against the top of the atmosphere, and is then pushed away from solar equator, moving to the south and north.
- as the air rises, it expands more as there is less atmosphere above it to compress it
- expansion of a gas causes it to cool (relationship of temperature drop to altitude gain is described by adiabatic lapse rate)
- cold and heavy air at top of atmosphere sinks, but because it is continually pushed to the north and south, it descends not at the equator, but at 30N nd 30S latitude.
- after descending, air is pulled back toward solar equator
zone of rising, heated air in Hadley cells is known as
intertropical convergence zone (ITCZ)
Hadley cells not only set prevailing winds in motion, but also
affect precipitation:
- air that comes into the ITCZ is humid
- as it rises and cools, much of the water vapour condenses into liquid water clouds and falls as rain, so the equatorial tropical regions are very rainy
- by the time a packet of air has reached the upper atmosphere, it has been wrung dry of most of its moisture
- when that air subsequently descends at the 30N and S latitudes, it comes down as hot, dry, air
- these latitudes chronically experience high-pressure weather systems (=deserts)
describe Ferrell and polar cells
- not as strong or consistent as Hadley cells, but are driven by same processes.
- as the dry air in the Ferrell cells moves across the earth’s surface towards the pole, it also picks up moisture, and finally tends to rise, creating another pair of rainy/snowy low-pressure zones around 60N and 60S
- high-level flows toward the equator close the Ferrell loops; the flows toward the poles set up polar cells (weakest + most diffuse)
why are wind patterns critical influences on organisms?
- they redistribute heat
- they redistribute water (as vapour) from oceans to continents
north wind
blows from north to south
describe the six-cell circulation pattern that imparts northernly and southerly components to prevailing wind directions
- between 0 and 30N, the Hadley cells push air from north to south
- between 30N and 60N, Ferrell cells push air in the opposite direction
- between 60N and the North Pole, the polar cells impart a flow to the south
Prevailing westerlies
- westerlies arise because the air being pushed straight northward by the Ferrell cell is passing over the surface of a spinning sphere
- that action produces a twist of the wind vectors with respect to the earth’s surface (Coriolis effect = pseudo force)
- between 30S and 60S, 30N and 60N
Prevailing easterlies
- between equator and 30N or 30S
- air is moving toward the equator, so air pacers fall behind their apparent target rather than getting ahead
where are prevailing winds strongest?
at the latitudes in the middles of the atmospheric cells, roughly at 15 and 45. here, the air is primarily being pushed horizontally across the earth’s surface, producing consistent winds
where is there little horizontal wind?
at the latitudes where air packets are mainly going upward (0 and 60) or coming down (30)
draw a diagram for wind
Fig. 5 of SFE
define and describe jet streams
another class of wind currents high in the atmosphere - concentrated and narrow westerlies that wander around in irregular fashion.
these blur and transgress the usual boundaries between the cells.
oceanic circulation
massive packets of water produce circulation patterns (currents) in the oceans. They move heat from one place to another and this affects neighbouring land masses; land and sea are not independent systems.
describe how oceans influence nearby land masses by providing thermal inertia
- land masses heat up in summer and cool down in winter much faster than do masses of water.
- in coastal areas, spring arrives more slowly, but summer lingers longer into the autumn
- maritime climates are buffered against temperature extremes
describe the relationship between ocean temperatures and precipitation
- more loading takes place when ocean waters are warm rather than cold
- warm water warms the air
- molecules of liquid water are more able to evaporate into vapour from warmer water and warmer air can retain more water vapour
orogenic precipitation and rain shadows
for a mountain range oriented perpendicular to the prevailing winds, precipitation is greatly enhanced on the windward side and suppressed in the lee.
as air is pushed up the windward side, it is cooled according to the lapse rate equations, causing condensation and precipitation
impact of exposure on vegetation
- in the northern hemisphere, south-facing hillsides face the direct rays of the sun
- north facing slopes are mostly shaded, cooler, and more moist.
- agitation on slopes thus differs
two factors that are most likely to limit the distributions of terrestrial species
temperature and water
why is water important?
- affects concentrations of chemical reactions
- cells and tissues depend on membranes to compartmentalise chemical processes and reactants. proper functioning depends on osmotic balance.
if cells get too dry
concentrations of dissolved salts increase. chemical reactions are slowed and changed
if too much water enters cells,
reactants get diluted and fail to combine as needed
what does it mean for objects to equilibrate?
will tend to reach the same temperature as their environment
thermoconformers
body temperatures more closely track ambient temperatures
endotherms vs ectotherms
Endotherms use internally generated heat to maintain body temperature. Their body temperature tends to stay steady regardless of environment.
Ectotherms depend mainly on external heat sources, and their body temperature changes with the temperature of the environment.
distinguish between conduction and convection
- conduction is the direct transfer of heat between two bodies that are in contact
- convection is the heat transfer that is facilitated by a moving fluid, typically air or water
how does radiative heat transfer differ from all other types of heat transfer?
they involve molecules bumping into each other and transmitting their kinetic energy
role of fur/feathers
to trap air and prevent convective flow. within the layer of insulation, a temperature gradient is set up and maintained; temperatures are cold near the outside of the fur, but warm next to the skin
how do birds keep warm?
they can lift their outer contour feathers away from their body, creating a dead-air space underneath that is filled by down feathers. these block convective air flow
how do mammals in cold environments usually keep warm?
depend on a thick layer of subcutaneous blubber which serves as insulation and long-term food energy storage
countercurrent circulation
- direct contact between arteries that send warm blood and the veins that bring cooled blood
- heat exchange can occur
- cooled returning venous blood captures warmth before it can be lost to the environment
- because the blood flows are going in opposite directions, there is a continuous temperature gradient between the two vessels
describe biochemical specialisations of photosynthetic pathways
- C3 and C4 pathways. atmospheric CO2 is incorporated into a 3C or 4C molecule.
- CAM. plants keep most of stomata closed in sun and only open at night
what are the cons of C3 and C4?
- not efficient in water use
- enzyme that captures the carbon also captures oxygen, which causes wasteful photorespiration at high temperatures
laminar flow
- airflow is unimpeded so a stratified pattern builds up
- happens when surface is smooth, without bumps or ridges
- one cm above leaf surface, air is going at normal speed
- much closer to leaf’s surface the air forms a boundary layer that is virtually stagnant.
why is stagnant air next to a leave not desirable?
- dead air depleted of CO2 and enriched in oxygen
- heat up cos convective evaporative cooling is reduced
turbulent flow
if the leave surface has enough irregularities, the boundary layer is broken up and freshened by eddy currents and vortices
microphylly
tiny leaves
desert annual plants
compressed life cycle in which the seeds germinate right after heavy rains start, they grow, flower, set seed, and die, all in around 2 months. plants temporally evade desert conditions.
