Adaptations to Terrestrial Environments

Vocabulary flashcards covering plant soil nutrition, water potential, photosynthesis pathways (C3, C4, CAM), animal osmoregulation, nitrogen excretion, and thermoregulation mechanisms based on the lecture notes.

Soil

Chemically and biologically altered material that overlies bedrock or other unaltered material at the Earth's surface.

Parent Material

The underlying bedrock or unaltered material whose physical and chemical characteristics determine the type of soil that forms above it.

Soil Horizon

A distinct layer of soil categorized by the specific components and processes happening at that level.

O-horizon

The topmost soil layer composed primarily of dead organic litter.

A-horizon

A layer rich in humus, consisting of partly decomposed organic material mixed with mineral soil.

Leaching

The process by which groundwater dissolves and removes soluble substances, carrying them down through deeper soil layers.

Weathering

The physical and chemical alteration of bedrock caused by water penetration, repeated freezing and thawing, and chemical dissolution.

Water Potential

The measure describing the tendency and movement of water in soil, influenced by gravity, water pressure, osmotic potential, and matric potential.

Matric Potential

The potential energy generated by attractive electrical forces between water molecules and soil particle matrices.

Sand

The largest soil particle size category, consisting of particles with diameters greater than $0.5\,m\text{m}$.

Silt

Intermediate-sized soil particles with diameters ranging between $0.002\,m\text{m}$ and $0.05\,m\text{m}$.

Clay

The smallest soil particle size category, with diameters less than $0.002\,m\text{m}$, providing a large total surface area that holds water tightly.

Loam

A soil mixture comprised of $40\%$ sand, $40\%$ silt, and $20\%$ clay.

Field Capacity

The maximum amount of water held by soil against the force of gravity, providing available water for plant growth.

Wilting Point

The soil water content level at which water is held so tightly by soil particles that plant roots can no longer extract it.

Cation Exchange Capacity

The ability of a soil to retain positively charged nutrient ions such as $\text{Ca}^{2+}$, $\text{Mg}^{2+}$, $\text{K}^+$, and $\text{Na}^+$ on negatively charged clay and organic matter particles.

Xylem

Specialized vascular plant tissue through which water and dissolved minerals move upward from roots to leaves.

Cohesion

The attraction of water molecules to one another, forming a continuous water column inside xylem vessels.

Adhesion

The attraction between water molecules and the inner walls of xylem vessels.

Transpiration

The process by which water evaporates out of leaf stomata into the atmosphere, creating a water potential gradient that pulls water upward through a plant.

Stomata

Pores on a leaf surface that serve as the point of entry for $\text{CO}_2$ and the point of exit for $\text{O}_2$ and $\text{H}_2\text{O}$.

Guard Cells

Specialized cells surrounding stomata that swell when turgid to open the pore, or shrink when collapsed to close the pore.

Rubisco

An enzyme involved in photosynthetic carbon fixation that catalyzes the reaction between $\text{CO}_2$ and RuBP, but has a low affinity for $\text{CO}_2$ and can also bind $\text{O}_2$.

Photorespiration

An inefficient biochemical pathway initiated when Rubisco preferentially binds $\text{O}_2$ instead of $\text{CO}_2$ under hot and dry conditions, releasing $\text{CO}_2$ and consuming energy. Products are G3P + G2P + CO2. Accumulation of G2P can become toxic. Can be converted, but comes at an energetic cost.

PEP Carboxylase

An enzyme used in $\text{C}_4$ and CAM photosynthesis that has a higher affinity for $\text{CO}_2$ than Rubisco, allowing efficient carbon fixation even at low $\text{CO}_2$ concentrations.

$\text{C}_4$ Photosynthesis

A photosynthetic adaptation in which initial $\text{CO}_2$ fixation occurs in chloroplasts of mesophyll cells, where light reactions occurs, via PEP carboxylase, and the Calvin cycle occurs separately in bundle sheath cells to prevent photorespiration.

CAM Photosynthesis

Crassulacean Acid Metabolism; a photosynthetic pathway in which succulents open stomata at night for gas exchange, and close stomata during the day to run the Calvin cycle without excess water loss.

Urea

A nitrogenous waste product produced by terrestrial mammals, filtered by the kidneys and excreted in urine with low toxicity but requiring water loss.

Uric Acid

A nitrogenous waste product excreted as a concentrated paste by birds and reptiles to conserve water, though requiring substantial energy to synthesize.

Radiation

The emission of electromagnetic energy by a surface, where the rate of heat radiation increases with the fourth power of absolute temperature ($K$).

Conduction

The transfer of heat between two objects that are in direct physical contact with one another. Rate of conduction depends on Organism’s surface area, organism’s resistance to heat transfer, and the temperature difference between organism and surroundings.

Convection

The transfer of heat caused by the movement of surrounding liquids or gases across an organism's surface. Ex. Wind Chill

Evaporation

The transformation of liquid into gas requiring heat energy, which produces a cooling effect on an organism's surface.

Thermal Inertia

The resistance to changes in body temperature exhibited by large organisms due to their low surface area-to-volume ratio.

Blood Shunting

A physiological adaptation where blood vessels shut off flow to extremities, rerouting warm blood back to the core to minimize heat loss in cold environments.

Chemical alteration

water dissolves soluble minerals (i.e. NaCl)

Desert plant adaptations

Increase concentration of amino acids, carbohydrates, organic acids in root cells to create higher osmotic forces and pull water in.

Light Reaction

Part of photosynthesis. Uses light energy to produce high energy compounds (ATP and

NADPH) and oxygen

Calvin Cycle

Uses energy from compounds produced during light reaction to convert CO2 into glucose

C3 Calvin cycle

Calvin cycle used by algae, aquatic plants, most terrestrial plants. Uses Rubisco and bad for low water areas as stomata must stay open.

C₃ Plant

C₄ Plant

Shallow Roots

acquire water rapidly from soil surface during brief rain events (rain does not penetrate soil)

Deep roots

access water deep below soil surface

Kangaroo rat

Adaptation to help maintain water and salt balance. Searches for food at night. Stays in underground burrow for the day. Get most water from eating rather than drinking. Highly efficient kidney.

Iguanas in Galapagos Islands

Expel excess salts by sneezing it out of their nasal glands