chapter 3 - Chapter 3 - Adaptation to Aquatic and...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
Chapter 3 - Adaptation to Aquatic and Terrestrial Environments Tuesday, November 06, 2007 12:47 AM Overview Basics The physical world both provides the context for life and constrains its existence. A world of environmental factors… o Resources: water, minerals and food items o Conditions: temperature and relative humidity Most factors have extremely wide ranges: o Each type of organism is typically adapted to a narrow range of each factor Overview - Regulations Organisms typically contrast with their external environments: o Internal conditions are maintained +/- constant o Fluxes of heat and substances must be regulated o But organisms are open systems… Resources must be acquired Wastes must be eliminated How do organisms accomplish this? Overview - Bottom Line It is important for us to understand the mechanisms organisms use to interact with their environment. This understanding may lead to insights: o Why organisms are specialized o Why organisms have specific geographic distributions o Why certain adaptations are associated with certain environments What do organisms have to deal with? We examine adaptations by considering various challenges facing organisms, for example: o How do pants acquire water and nutrients from soils and transport these? o How do plants carry out photosynthesis under varied environmental conditions? o How do plants and animals cope with extremes of temperature, water stress, and salinity? Water What so special about water? Polarity of water
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Why do space scientist search for water on Mars? Hydrogen and oxygen bounds Water as a solvent Hydrogen bounds between water molecules Availability of Soil Water Water molecules are attracted to: o Each other (Causes surface tension ) o Surfaces (Causes capillary action ) When a soil is saturated and excess (gravitational) water drains: o Remaining water exists as thin films around soil particles (mineral and organic) o The greater the area of such particles (as in clayey soils), the more water the soil retains All soil water molecules are not equal It's all a matter of physical attraction… o The close a water molecule is to a soil particle, the greater the force with which it is attracted o This force is the matric potential of the soil, contributing to the overall water potential o Matric potentials (units are Mpa and atm) are considered increasingly negative as they represent greater attractive forces It's all a matter of potential… Soil water potential is: o Usually dominated by matric forces o Determined as the force required to remove the most loosely bound water molecules Typical "benchmark" values are: o -0.1 atm ( field capacity ) o -15 atm ( wilting point ) o -100 atm (exceedingly dry soil ) Plants obtain water from the soil How do water molecules move? o
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 8

chapter 3 - Chapter 3 - Adaptation to Aquatic and...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online