BIO226 : Individual : Environmental Factors : Lesson

		Energy, heat, light
Sun

Adaptation, aerobic, allometry, anaerobic, archaebacteria, boundary layer, compensation point, cyanobacteria, detritus, diversity, ecology, ecological system (ecosystem), euphotic zone, evolution, experiment, habitat, hypothesis, mathematical model, natural selection, niche, osmosis, population, saturation point, solar constant.

Physical factors present the most immediate challenges to every organism. In this section, we will examine some of the most obvious factors in an organism's environment.

I. Introduction

1. Ecology

2. Levels of organization
   • Biosphere --> Ecological system (ecosystem)--> Community --> Population
   • Biotic and abiotic
   • Energy and nutrients (chemical elements)

Kinds of organisms Sunlight is the ultimate source of energy Producers Consumers Decomposers

4. Energy
   • Organic: contained in organic molecules
   • Exchanged across surfaces

5. Growth
   • Populations by increasing numbers of individuals
   • Individuals by increasing in size

6. Size
   • Bacteria and fungi: small but numerous
   • Large herbivores: large and few

7. Scale: time and space - relative to size and lifespan of organism

8. Ecological principles
   • Physical and chemical laws cannot be changed - organisms adapt
   • Ecological steady state: the system is stable but the components are dynamic
   • Nature is diverse - ecosystems, communities, and populations are composed of a variety of species adapted in their own ways to the environment
   • Scientific process - testing hypotheses
   • Humans - helpful and harmful

II. The Physical Environment

1. Water
   • Thermal properties
   • Chemical properties

2. Water and soil
   • Interaction of water with surfaces
   • Field capacity - force of attraction: soil particles and plants --> wilting point

3. Temperature
   • Range for life - causes of mortality at high and low temperatures
   • Freezing point depression - adaptations
   • Heat and kinetic energy, Q₁₀

4. Acidity
   • pH - negative logarithm of concentration
   • Carbonic acid - equilibrium
   • Limits for living systems

5. Energy transformations
   • Chemical bonds contain energy: carbohydrates, lipids, proteins
   • Reduction and oxidation - changing energy potential
   • CO₂/O₂ - photosynthesis and respiration
   • Diffusion in air and water

6. Inorganic nutrients
   • Major limiting factors: nitrogen, phosphorus
   • Other major nutrients: sulfur, potassium, calcium, magnesium, iron, sodium
   • Availability varies with soil water, pH, and temperature

7. Osmotic potential
   • Diffusion - passive and active transport
   • Salt concentration: seawater, Great Salt Lake, Dead Sea
   • Osmotic challenges to freshwater and marine organisms

8. Light
   • Sun is the primary source of energy for the biosphere
   • Visible spectrum, infrared, ultraviolet
   • Photoactive gases - greenhouse gases - greenhouse effect
   • Photoactive pigments
   • Photosynthetic active region (PAR)

9. Thermal environment
   • Radiation - electromagnetic, infrared
   • Conduction - contact
   • Convection - aided by fluids
   • Transfer facilitated by water - evaporation, transpiration, rates, boundary layer

10. Body size
    • Size changes relationships and rates
    • Surface area and volume - volume changes faster than surface area

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

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