BIO326 : Individual : Adaptation to Environment : Lesson

Active transport, activity space, adaptation, ambient, C₃ photosynthesis, C₄ photosynthesis, Calvin cycle, CAM, conformer, countercurrent circulation, diffusion, ectotherms, endotherms, homeothermy, poikilothermic, regulator, symbiont.

Organisms have developed ways to cope with their environments. In this section, we will look at examples of organisms which have found ways to be successful in their habitats.

I. Adaptation - meeting challenges

1. Salt and water balance in plants and animals
   • Diffusion - the tendency toward equilibrium
   • Freshwater organisms
   • Marine organisms
   • Terrestrial organisms

Nitrogen - protein metablolism Ammonia Urea Uric acid Temperature - anatomy and behavior Water for plants - pressures (measured in atmospheres) Photosynthesis - problems of water and temperature Anatomical solutions Biochemical solutions Examples of Myriophyllum, Isoetes, & Stylites

6. Oxygen
   • Diffusion: air vs. liquid
   • Hemoglobin: direction of diffusion depends on relative concentrations
   • Hemoglobin: different solutions to specific conditions

7. Countercurrent circulation - blood & environmental fluid (air, water) flow in opposite directions
   • Anatomy
   • Prevents equilibrium and maintains a gradient

8. Soil nutrients
   • Diffusion (passive)
   • Active transport
   • Root-shoot ratio
   • Fungal symbionts
   • Nutrient hoarding

9. Optimum - range of environmental conditions where the organism is best suited
   • Example of salt
   • Example of temperature
   • Enzymes provide the mechanism

II. Homeostasis - staying in balance

1. Negative feedback - oppose change, return to stable condition
   • Components: sensor, set point, effector

2. Temperature - an important determinant of organism function

3. Cost of endothermy
   • Newton's law of cooling
   • Basal metabolic rate
   • Lower critical temperature
   • Adaptations: countercurrent heat exchange; torpor

Partial homeothermy - a compromise Activity space - microhabitats Environmental tolerance and examples Plantago Mallee dragon Desert iguana Cactus wren Structural responses - trade-offs Acclimation - short-term Developmental responses

When you have completed this lesson, go on to Review Questions