AEC 360    

Lecture 4:  Physiological Ecology

I.  What are the physical factors that organisms must deal with?

    A.  Examples of environmental extremes that are experienced by organisms

    B.  Shelford's Law of Tolerance: either too little or too much of an environmental factor may exclude a species from an area.

    C.  Adaptation:  A genetically determined characteristic that enhances the ability of an individual to cope with its environment

       1.  Guiding principle 1:  Adaptations involve tradeoffs:  it is not possible to maximize performance in every characteristic, because there are evolutionary and physical contraints on adaptation.

       2.  Guiding principle 2: performance as an integrative measure of individual success

II.  Adaption to the physical environment: Fish
    A.  Water
        1.  Water has a number of properties that help to maintain life
            -Dense and viscous, providing support
            -Stays liquid over a broad range of tempseratures
            -Conducts heat rapidly
            -Becomes less dense as it cools below 4oC
            -Universal solvent

        2.  Some plants and animals take up water through osmosis

        3.  Fish have different adaptations to deal with water (Fig. 2.10)
            -- Freshwater fish must exclude water, retain solutes

            -- Marine fish must retain water, exclude solutes (Figure 2.11)

    B.  Oxygen is required for respiration
        1.  Fish have evolved countercurrent circulation to make oxygen uptake more efficient (Figure 2.16)

    C. Nutrients and Food
        1.  Animals consume other organisms (plant or animal)

        2.  Animals have evolved complex adaptations to acquire food


    C.  Temperature (Figure 2.18. 2.21))

        1.  Animals must cope with extremes of heat and freezing
        2.  All animals must maintain a constant internal environment to some degree.  Some, called homeotherms, also maintain a constant internal temperature.  Poikilotherms (cold-blooded animals) rely on their environment to regulate body temperature
        3.  Glycoproteins prevent ice formation

        4.  Fish are adapted to local physical conditions

    D.  Animals can behave

III.  Adaptation to the physical environment: Plants
    A.  Water (Figure 3.2, 3.5)
        1.  Transported through plant by the process of transpiration
        2.  Creates water potential, or pressure causing water to flow to leaves
        3.  Water enters roots by osmosis

    B.  Nutrients
        1.  Plants obtain mineral nutrients from the soil through their roots

        2.  There are a number nutrients essential to most life; nitrogen (N) and phosphorous (P) are typically most limiting

    C.  CO2, Light, and Temperature (Figure 3.9, 3.10, 2.15)
        1.  Plants need light and carbon to create organic molecules through photosynthesis
        2.  Plants take up carbon through their leaves
        3.  Plants photosynthesis has adapted to heat and water stress
            a.  C3 photosynthesis is the typical form of photosynthesis that involves the Calvin-Benson cycle in the mesophyll cells (Figure 3.11, 3.12)
                -- Most cells participate in photosynthesis
                -- Risk of water loss, especially at high temperatures

            b.  C4 photosynthesis makes more efficient use of Carbon, and prevents carbon loss in hot climates
                --  Calvin-Benson cycle occurs in bundle sheath cells
                --  Close association between mesophyll and bundle sheath cells

            c.  CAM photosynthesis is like C4 photosynthesis, except that carbon assimilation occurs at night, preventing water loss through stomates, and photosynthesis occurs during the day
                -- Occurs in hot, arid environments

        4.  Plants have many adaptations to prevent water loss in dry environments (Figure 3.13)