Adaptations to Terrestrial Environments 3

Adaptations to Terrestrial Environments

Soil Type
- Soils derive from weathered rock.
- Differences in soil types are due to:
 - Climate
 - Parent rock (minerals)
 - Organic matter
 - Age (layers or "horizons")
 - Particle sizes
- Water as a Solvent:
 - Minerals in soil from parent rock dissolve in water, forming salt.
 - Example: Limestone $CaCO³$ in South Florida.
- Soil pH:
 - Ranges from acidic to basic (alkaline).
 - Factors influencing pH:
 - Moisture
 - Parent rock
 - Organic matter
 - pH Scale:
 - Acidic: < 7
 - Neutral: 7
 - Basic (Alkaline): > 7
 - Common pH ranges:
 - Mineral soils: Extreme range
 - Arid region soils: Moderate to strong alkaline
 - Humid region soils: Common for soils to be acidic
 - Peat soils: Extreme pH
- Soil Structure:
 - Mineral particles of different sizes (sand, silt, clay).
 - Aggregates of particles.
 - Organic matter.
 - Pores containing air and water.
 - Organisms: Fungi, actinobacteria, and the rhizosphere (root zone).
- Glomalin:
 - Glycoprotein produced by hyphae of arbuscular mycorrhizal fungi.
 - Binds soil particles together.
 - Can constitute up to 30% of soil carbon in intact habitats.
- Soil Texture and Water Availability:
 - Soil texture influences water content.
 - Water runs through big particles while tiny particles bind water tightly.
 - Loam and silt loam soils hold the most water available for plants.
- Soil Orders (STATSGO):
 - Different soil orders affect plant community composition.
 - Examples: Alfisol, Entisol, Histosol, Inceptisol, Mollisol, Spodosol, Ultisol.
 - Horticultural Hardiness Zones: Based on average annual minimum temperature.
 - Plant Communities: Vary by region and soil type (e.g., beaches/dunes, pine flatwoods, cypress swamps).

Nutrients: Nitrogen

Nitrogen Availability:
- Depends on soil type, abiotic factors (temperature, moisture, pH, depth), and biotic factors (root exudates, mycorrhizas, rhizosphere).
- Plants can be nitrogen-limited, leading to deficiency symptoms.
Low-Nitrogen Environments:
- Bogs and longleaf pine savannas.
Plant Carnivory:
- Plants like Sarracenia (pitcher plants) use carnivory to obtain nitrogen in low-N environments.
Nepenthes (Pitcher Plants):
- Adapted for low soil nitrogen; specialized for various N sources (pollinators, termites, leaf litter, scat).
- Resource partitioning: Different pitcher types for different resources at different altitudes.
Nitrogen in Animals:
- Animals have excess nitrogen due to their intake of carbohydrates, fats, proteins, and nucleic acids.
- Nitrogenous waste products: Ammonia, urea, uric acid.
- Trade-off in nitrogenous waste forms: Toxicity vs. energy cost of production.
Aquaponics:
- Integrated system where fish waste (ammonia) is converted to nitrite and then nitrate by bacteria.
- Plants absorb nitrate as a nutrient, purifying the water for the fish.

Light & Photosynthesis

Why Plants Are Green:
- Chlorophyll absorbs light in the red and blue regions of the spectrum, reflecting green light.
Review of Flows, Inputs, and Outputs:
- Energy: Source is the sun, ends up as chemical energy in the form of glucose, but mostly as heat.
- Electrons: Source is water, end up in glucose.
- Carbon: Source is carbon dioxide, ends up in glucose.
Photosynthesis:
- The $O2$ released as waste comes from $H2O$ , and the $O$ in starch molecules in a potato comes from $CO_2$ .
Why Plants Are Sometimes Not Green:
- Young leaves can be red due to anthocyanins protecting them from intense light or herbivory.
- Ghost pipes (Monotropa uniflora) lack chlorophyll and are parasitic on fungi.
- Multiple hypotheses exist for why plants are not green, including light protection and herbivory defense.

Modifications to Photosynthesis

Photorespiration:
- Occurs when Rubisco binds to $O2$ instead of $CO2$ , especially under hot and dry conditions when stomata close.
- Stomates close: Decreases $CO2$ and increases $O2$ . Stomates open: Leaf admits $CO2$ and loses $H2O$ .
- Most severe in tropical savanna.
C4 Photosynthesis:
- Fixes $CO_2$ without photorespiration using specialized cell types.
- $CO2$ is pumped into bundle sheath cells, increasing $CO2$ concentration around Rubisco.
- Efficient but expensive in terms of ATP; not all plants can do it.
- More common in grasses, especially in tropical savannas.
- About 3% of plant species but accounts for 25% of terrestrial productivity.
CAM (Crassulacean Acid Metabolism):
- CAM Day-Night Cycle:
  - Night: Stomata open. CO2 is fixed via PEP carboxylase to create C4 which is stored in the vacuole as malic acid.
  - Day: Stomata close. The C4 is transported to the chloroplast to release CO2 to be used in the Calvin Cycle.
- Fixes $CO_2$ at night and stores it for use during the day, when stomata are closed to conserve water.
- Common in arid environments and epiphytes.
- About 7% of plant species.
- Some plants exhibit plasticity, capable of C3, C4, or CAM photosynthesis depending on conditions.

Heat

Optimal Temperature:
- Too cold: Metabolic rate is low, lipids are stiff.
- Too hot: Enzymes denature, DNA is damaged, more food needed.
Heat Transfer Mechanisms:
- Conduction, convection, radiation.
- Factors affecting heat transfer: Surface area, insulation, air movement.
Plant Adaptations to Heat:
- Maximize heat transfer by convection.
- Minimize heat absorption through reflection and small leaves/leaflets.
- Leaflet orientation minimizes heat.
- Adaptive loss of leaves, silvery hairs for reflection and moisture retention.
Animal Adaptations to Heat:
- Thermoconformers (poikilotherms) vs. thermoregulators (homeotherms).
  - Ectotherms (rely on behavior).
  - Endotherms rely on physiology.
- Body mass/surface area ratio: Advantage of huge mass and minimize surface area.
- Ear size increases to maximize heat transfer.
- Flapping ears increases convection.
- Panting (convection, evaporation) and behavior (seeking shade).
Human Adaptations to Heat:
- Sweating (evaporation), loose-fitting clothing (convection), and behavioral adaptations.

Participation Activities & Miscellaneous

Various participation activities are assigned throughout the course, including:
- Writing a biography on Canvas profile.
- Making an observation of temperate forest bird ecology and stating a specific ecological hypothesis.
- Describing how specific mammals keep cool in hot weather.
Office hours are available for student support.
Minimizing distractions during lectures is crucial for learning.