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Lecture 3

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Biological Sciences
Marc Cadotte

Lecture 3: Organisms and their Environment Introduction ▯ - The physical environment ultimately determines where organisms can live, and the resources that are ▯ available to them ▯ - Thus, understanding the physical environment is key to understanding ecological phenomena ▯ - Some species are only fit for certain environment. This helps us understand certain natural processes Global Diversity ▯ - Amphibians and plants share the same geographic regions in terms of species diversity Climate ▯ - Climate is the most fundamental characteristic of the physical environment. Climate controls where ▯ organisms are ▯ - Climate is the long-term description of weather, based on averages and variation measured over decades ▯ - On average, the climate in the tropics = warmed compared to Canada ▯ - Climate determines the geographic distribution of organisms ▯ - Can map out wheather data (rainfall, temperature) to find the limits of geographic distribution ▯ - Depends on climate change; birds have been staying in southern ontario more; climate ▯changes species ▯ distribution ▯ - A major climate change (eg. drought) can cause widespread changes in ecosystems, change where species ▯ are ▯ - Middle of the earth is warmer because radiation is focusing on that region (higher density) compared to the ▯ northern goegraphic locations (radiation spread out over wide range of area) ▯ - Affects climate: warm area rises, then it cools, condenses -> rain (rainy areas around equator) ▯ - Air comes down from high pressure; goes from cooler to warmer ▯ - Deserts are around 30 degrees N/S lattitude ▯ - Hadley cell is at the equator ▯ - Weʼre in a ferrell cell region (low pressure, ample precipitation in all seasons) ▯ - Polar cell -> north/south pole, cold, dry in all seasons ▯ -The three cells result in the three major climatic zones in each hemisphere: Tropical, temperate, and polar ▯ zones▯ ▯ - As we move northward, we get more seasonal variation in temperature (ex. Canada compared to Trinadad) ▯ Regional Climate ▯ - Regional climate can be affected by topography (mountains) and water bodies ▯ - The Rain-Shadow Effect: occurs along the west coast of Canada. Air comes in hot from ▯the ocean, goes up ▯ the mountain, it cools, condenses, and it rains. Comes down in high pressure, makes one side of the mountain ▯ very dry, therefore different species ▯ - Evapotranspiration is the sum of water loss through transpiration by plants and ▯evaporation from the soil ▯ ▯ - transfers energy (as latent heat) and water into the atmosphere, thereby affecting air temperature ▯ ▯ and moisture ▯ - Three types of energy + heat energy: albedo, sensible heat loss, latent heat loss ▯ ▯ - Sensible heat loss: direct heat loss, i.e. heating air ▯ ▯ ▯ - direct transfer of energy between two substances (blow cool air over hot air) ▯ ▯ ▯ - The change in surface roughness increases sensible heat loss by convection ▯ ▯ ▯ (wind) ▯ ▯ - Albedo: reflected radiation from surface, return energy back to space ▯ ▯ ▯ - + Sensible heat loss: relatively low in forest systems ▯ ▯ ▯ - Removing trees increases the albedo of the land surface, lowering its absorption of solar ▯ ▯ ▯ radiation ▯ ▯ - Latent heat loss: via change in state, i.e. water to gass ▯ ▯ ▯ - cooling the climate in forest systems (causes precipitation) ▯ ▯ ▯ - These cooling effects are more than offset by the warming effects of deacreased latent heat ▯ ▯ ▯ loss by evapotranspiration ▯ ▯ ▯ - Reduced evapotranspiration also reduces the return of moisture to the atmosphere and ▯ ▯ ▯ reduces precipitation rates ▯ ▯ - in deforested systems, the system is warmed because latent heat loss is so much less (even though ▯ ▯ albedo + sensible heat loss increases, there is a lack of ▯ ▯ ▯ precipitation) ▯ ▯ - Causes feedback effect on the organisms that live in the environment ▯ Introduction▯ ▯ - The biosphere is the zone of life on Earth. It lies between the lithosphere- Earthʼs surface crust and upper ▯ mantle, and the troposphere- the lowest layer of the atmosphere ▯ - Biosphere is made up of different biomes ▯ - Can further classify into different habitats (tundra, rainforest, desert, boreal forest) ▯ - Terrestrial biomes: are characterized by the dominant growth forms of vegetation. Classified by the growth ▯ form of the most abundant morphology (not plant species) ▯ - Biomes are large biological communities shaped by the physical environment, particularly climatic variation. ▯ Based on similarities in the morphological responses of organisms to the ▯physical environment Terrestrial Biomes ▯ - Characteristics of the leaves may be used: ▯ ▯ - Deciduousness: seasonal shedding of leaves ▯ ▯ - Thickness ▯ ▯ - Succulence: development of fleshy water storage tissues Growth form Environment Sclerophyllous shrubs Seasonally dry/moist and warm/cool 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/
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