Biology 107 Unit 4 Study Guide: Plant and Animal Physiology, Diversity, and Energetics

Comprehensive vocabulary flashcards covering metabolic categories, plant vascular and tissue architecture, cation exchange, metabolic rate scaling, digestion, and animal gas exchange/circulation.

Photoautotroph

An organism that utilizes light as its energy source and $CO_2$, $HCO_3^-$, or a related compound as its carbon source (e.g., plants and cyanobacteria).

Chemoautotroph

An organism that oxidizes inorganic chemicals (such as $H_2S$, $NH_3$, or $Fe^{2+}$) for energy and fixes carbon from $CO_2$, $HCO_3^-$, or related compounds; unique to specific species of prokaryotes, Archaea, and some Bacteria.

Photoheterotroph

An organism that harnesses light for energy but must obtain carbon from organic compounds; unique to aquatic and halophilic prokaryotes, Archaea, and some Bacteria.

Chemoheterotroph

An organism that relies on organic compounds for both its energy source and its carbon source (e.g., animals, fungi, and many prokaryotes including decomposers).

Water Potential Gradient (in plants)

The progressive decrease in water potential from the soil (\text{soil } \boldsymbol{\text{\Psi}} = -0.3\,\text{MPa}) up through the roots, trunk xylem ($-0.6\,\text{MPa}$ to $-0.8\,\text{MPa}$), leaf cell walls ($-1.0\,\text{MPa}$), and leaf air spaces ($-7.0\,\text{MPa}$) to the outside atmosphere (\text{outside air } \boldsymbol{\text{\Psi}} = -100.0\,\text{MPa}), which drives the upward movement of water.

Cohesion (in xylem)

The intermolecular attraction between water molecules via hydrogen bonding that maintains an unbroken column of water as it is pulled up xylem conduits.

Adhesion (in xylem)

The hydrogen bonding of water molecules to the hydrophilic cellulose cell walls of xylem tracheids and vessel elements, counteracting the downward pull of gravity.

Transpiration

The evaporative loss of water vapor from plant leaves through open stomata into the atmosphere, generating negative pressure that pulls xylem sap upward.

Pressure-Flow Hypothesis (Phloem Translocation)

The mechanism where sugars are actively loaded into sieve-tube elements at a source, lowering $\psi_S$ and drawing water from adjacent xylem vessels to elevate $\psi_P$, which drives bulk flow toward sinks where sugars are unloaded.

Sugar Source

A plant organ that produces sugar via photosynthesis or the breakdown of stored starch (e.g., mature leaves).

Sugar Sink

A plant organ that consumes or stores sugar (e.g., growing roots, shoot tips, developing fruits, and storage tubers).

Cation Exchange

The process by which root hairs acidify the soil solution by releasing $CO_2$ from respiration (which reacts with $H_2O$ to form $H_2CO_3$, releasing $H^+$) and pumping $H^+$; these $H^+$ ions displace mineral cations ($K^+$, $Ca^{2+}$, $Mg^{2+}$) bound to negatively charged soil particles so roots can absorb them.

Rhizosphere

The narrow zone of soil directly surrounding and influenced by living plant roots and root secretions.

Rhizobia

Soil bacteria that form endosymbiotic mutualisms with plant roots to fix inert atmospheric nitrogen into biological forms that plants can utilize.

Mycorrhizal Fungi

Mutualistic soil fungi that associate with plant roots, supplying minerals and water from the soil in exchange for photosynthetic sugars.

Basal Metabolic Rate (BMR) Scaling

The relationship where total basal metabolic rate increases with overall body mass, but smaller animals have a significantly higher BMR per unit of body mass ($\text{L } O_2/\text{hr} \cdot \text{kg}$) than larger animals.

Endotherm

An organism that generates metabolic heat internally to maintain a relatively constant body temperature (e.g., mammals and birds).

Ectotherm

An organism that relies primarily on external environmental heat sources to regulate its body temperature (e.g., reptiles and fish).

Obligate Aerobe

An organism that requires oxygen ($O_2$) for cellular respiration and cannot survive in its absence.

Obligate Anaerobe

An organism that is poisoned by oxygen ($O_2$) and relies exclusively on fermentation or anaerobic respiration.

Facultative Anaerobe

An organism that utilizes oxygen ($O_2$) when present for aerobic respiration, but can switch to fermentation or anaerobic respiration when oxygen is absent.

Microbiome

The community of microorganisms living in and on host bodies (notably the gut) that facilitates nutrient digestion, vitamin production, immunity, and defense against pathogens.

Parenchyma

Plant ground tissue consisting of living cells with thin, flexible primary cell walls; responsible for photosynthesis, nutrient storage, and tissue repair.

Collenchyma

Plant ground tissue composed of elongated living cells with unevenly thickened primary walls that provides flexible structural support to growing stems and leaves.

Sclerenchyma

Rigid plant supporting tissue composed of cells that are dead at maturity, containing thick, lignified secondary cell walls (e.g., fibers and seed coats).

Cuticle (plants)

A waxy extracellular layer on the epidermis of leaves and stems that prevents desiccation and inhibits excessive water absorption.

Stomata

Microscopic pores in the epidermis flanked by two guard cells that regulate water loss via transpiration and allow gas exchange ($CO_2$ and $O_2$).

Trichomes

Specialized hair-like epidermal outgrowths that protect plants against insect herbivores, UV radiation, excessive water loss, and gall formation.

Cortex (plants)

The region of ground tissue situated external to the vascular cylinder, just beneath the dermal epidermis in stems and roots.

Pith

Ground tissue located in the center of the stem, internal to the vascular tissue.

Tracheids

Elongated, tapered water-conducting xylem cells that are dead at maturity; water moves between adjacent tracheids through pit membranes in their thin primary walls.

Vessel Elements (Vessels)

Wide, barrel-shaped water-conducting cells in xylem that are dead at maturity and aligned end-to-end; water flows freely through open perforation plates.

Sieve-Tube Elements

Tubular phloem cells that remain alive at functional maturity but lack a nucleus and most organelles; transport sugars through perforated end walls called sieve plates.

Companion Cells

Specialized nucleated cells adjacent to sieve-tube elements, packed with mitochondria and ribosomes, that provide metabolic maintenance and load sugars into the phloem.

Apical Meristem

A localized region of actively dividing, undifferentiated cells at the shoot and root tips responsible for primary growth (elongation).

Lateral Meristem

Meristematic tissue (such as vascular and cork cambium) that extends along the length of stems and roots, driving secondary growth (widening in girth).

Pressure Potential ($\psi_P$)

The component of total water potential representing the physical hydrostatic pressure exerted on a solution (can be positive, as in turgid cells, or negative, as in xylem tension).

Solute Potential ($\psi_S$)

The component of water potential that is proportional to the osmolarity of a solution; always zero or negative, decreasing as more solute molecules are dissolved.

Turgor Pressure

The outward physical force exerted by the protoplast pushing the plant cell's plasma membrane against the rigid cell wall.

Epithelial Tissue

Animal tissue that covers body surfaces, lines internal cavities and organs, and forms barriers active in protection, secretion, and absorption.

Connective Tissue

Animal tissue that binds, cushions, and structurally supports other tissues; characterized by an extracellular matrix and includes bone, blood, cartilage, and adipose tissue.

Muscle Tissue

Contractile tissue responsible for mechanical movement; categorized into skeletal muscle (voluntary), smooth muscle (involuntary in viscera), and cardiac muscle (heart wall).

Nervous Tissue

Tissue composed of neurons and glial cells that senses stimuli, generates electrical impulses, and conducts communication throughout the animal body.

Pepsinogen

The inactive zymogen precursor of pepsin secreted by chief cells in gastric glands; prevented from digesting cell proteins until activated by acid in the gastric lumen.

Chief Cells

Specialized secretory cells in the gastric glands of the stomach that synthesize and release pepsinogen.

Parietal Cells

Stomach lining cells that secrete hydrochloric acid ($HCl$) by pumping $H^+$ and $Cl^-$ ions, acidifying the gastric lumen.

Hydrochloric Acid ($HCl$)

Strong stomach acid secreted by parietal cells that lowers gastric pH, activates pepsinogen into active pepsin, denatures dietary proteins, and kills swallowed pathogens.

Pepsin

A gastric endopeptidase active in highly acidic environments (optimal $\text{pH } 1.5\text{--}2$) that hydrolyzes dietary proteins into smaller polypeptides.

Filter Feeding

A feeding mechanism in which an organism strains microscopic organisms or suspended food particles from water (e.g., baleen whales and clams).

Substrate Feeding

A feeding mechanism where animals live in or directly on their food source, eating their way through the material (e.g., caterpillars on foliage).

Fluid Feeding

A feeding mechanism in which an animal extracts and ingests nutrient-rich fluids from living hosts or plants (e.g., mosquitoes, aphids, and hummingbirds).

Bulk Feeding

A feeding mechanism where animals ingest relatively large, discrete pieces of food that are subsequently processed and broken down internally (e.g., humans and snakes).

Arteries

Thick-walled blood vessels with smooth muscle and elastic tissue that carry pressurized blood away from the heart toward capillary beds.

Veins

Vascular vessels equipped with valves that carry blood at lower pressures back toward the heart from capillary networks.

Capillaries

Microscopic, single-endothelial-cell-thick vessels organized into beds that permeate tissues to allow exchange of gases, nutrients, and wastes between blood and interstitial fluid.

Atrium (heart)

A heart chamber with relatively thin walls that receives returning blood from either systemic tissues or respiratory organs and transfers it to a ventricle.

Ventricle (heart)

A thick, muscular chamber of the heart that pumps blood out into arterial circuits toward the lungs/gills or the body tissues.

Single Circulation

A circulatory pattern in which blood passes through the heart only once per complete body circuit (e.g., in fish, where blood flows from heart to gills to body tissues before returning to the heart).

Double Circulation

A circulatory pattern in which blood is pumped through the heart twice per complete circuit, maintaining distinct pulmonary and systemic circuits under different pressures (found in amphibians, reptiles, mammals, and birds).

Tracheal System (Insects)

A network of dead-end air-filled branching tubes (tracheae) in insects that conveys atmospheric gases directly from surface spiracles to body tissues without using the circulatory system.