Chapter 3: Adaptations to Terrestrial Environments & Photosynthesis

Vocabulary flashcards covering key terms from the Chapter 3 notes on terrestrial adaptations and photosynthesis.

Water potential

A measure of water’s potential energy; affects the movement of water in soil from one location to another.

Matric (matrix) potential

Potential energy generated by attractive forces between water molecules and soil particles; quantified in megapascals (MPa).

Field capacity

Maximum amount of water held by soil against gravity after excess drainage.

Wilting point

Soil moisture level (~−1.5 MPa) at which most plants cannot extract more water.

Soil texture

Classification of soil by particle size: sand (>0.05 mm), silt (0.002–0.05 mm), clay (<0.002 mm).

Clay surface area vs water holding

Smaller particles have larger surface area relative to volume; can hold more water, but water is held tightly.

Osmosis

Passive movement of water across a semipermeable membrane from lower to higher solute concentration.

Root pressure

Osmotic potential in roots draws water from the soil into the xylem.

Xylem

Vascular tissue that transports water and minerals from roots to leaves.

Cohesion

Mutual attraction between water molecules that helps water rise through the xylem.

Transpiration

Evaporation of water from leaf surfaces that generates water potential in the plant.

Cohesion-Tension Theory

Water movement from roots to leaves driven by transpiration-induced tension and cohesive water columns.

Stomata

Pores on the underside of leaves that regulate CO2 uptake and water loss.

Guard cells

Pairs of cells that regulate stomatal opening and closing.

Ribulose

Enzyme that fixes CO2 in the Calvin cycle; can also fix O2, leading to photorespiration; most abundant enzyme on Earth.

Calvin cycle

Light-independent reactions that synthesize sugars using ATP and NADPH from the light reactions.

Photosynthesis

Process by which plants convert light energy, CO2, and water into glucose and O2.

Photosynthesis equation

6 CO2 + 6 H2O + photons → C6H12O6 + 6 O2.

Light-dependent reactions

Photosynthetic reactions that capture light to produce ATP and NADPH, occurring in the thylakoid membranes.

Chloroplast

Organelle where photosynthesis occurs; contains thylakoids and stroma with pigments.

Thylakoids

Membrane-bound sacs inside chloroplasts where the light reactions take place.

Stroma

Fluid-filled space inside chloroplasts surrounding the thylakoids; site of the Calvin cycle.

Chlorophyll a

Primary pigment in photosynthesis; drives the light reactions.

PAR (Photosynthetically Active Radiation)

Visible light in the 400–700 nm range used for photosynthesis.

C3 photosynthesis

Baseline carbon fixation pathway where CO2 is fixed by Rubisco into a 3-carbon compound (3-PGA); common in cool, wet conditions.

C4 photosynthesis

CO2 fixation first by PEP carboxylase into oxaloacetate (4C) in mesophyll cells; CO2 released to Calvin cycle in bundle-sheath cells; more water-use efficient under high light.

CAM photosynthesis

Temporal separation of CO2 uptake and fixation; stomata open at night, CO2 stored as malate, released during the day.

PEP carboxylase

Enzyme that fixes CO2 into oxaloacetate in C4 photosynthesis.

Oxaloacetate (OAA)

4-carbon molecule produced by PEP carboxylase in C4 plants; releases CO2 to the Calvin cycle.

Photorespiration

Oxygenation of ribulose-1,5-bisphosphate by Rubisco, leading to energy loss; more pronounced in hot, dry conditions and in C3 plants.

Notothenioids

Antarctic fishes with antifreeze glycoproteins in blood; low hemoglobin and narrow optimal temperature range.

Desert kangaroo rat

Desert rodent with adaptations to conserve water: nocturnal activity, underground living, large kidneys and loop of Henle for increased water retention.

Ammonia (NH3)

Nitrogen waste excreted by many aquatic organisms; highly toxic and water-intensive to excrete.

Urea

Nitrogenous waste produced by mammals and some amphibians; less toxic than ammonia and requires less water, but more energy to synthesize.

Uric acid

Nitrogenous waste excreted by birds and many reptiles; least toxic and highly water-conserving.

Essential nutrients

Mineral elements required for plant growth (e.g., NH4+, NO3−, PO4^3−, Ca^2+, K^+) whose absence halts growth.

Loam

Soil texture considered among the best for plant growth; balanced proportions of sand, silt, and clay.

Homeostasis

An organism’s ability to maintain stable internal conditions; often via negative feedback mechanisms.

Soil nutrient availability factors

Soil nutrient availability varies with soil temperature, pH, and the presence of other ions.