Exam 1 Study Guide: Adaptations to Land and Plant Diversity

Flashcards covering adaptations to land, plant diversity (bryophytes, vascular plants, gymnosperms, angiosperms), plant structure, water & nutrient transport, growth, and defense mechanisms.

Cuticle

A waxy coating on plants that prevents desiccation and provides protection from UV light.

Stomata

Openings on plants that allow gas exchange (CO2 in, O2 out) and help stop desiccation during dry spells.

UV pigments

Chlorophyll a and b, which absorb UV rays for photosynthesis and provide protection against radiation.

Sporoponenin

A thick-walled substance in spores that resists decay and prevents spores from drying out, responsible for early pollen records.

Mutualistic associations w/ fungi

A relationship where fungi bring plants minerals and water from the soil, and in return, the fungi gain products of photosynthesis.

Multicellular gametangia

Multicellular organisms in which gametes are produced.

Archegonia

Female gametangia.

Embryos

Tiny diploid plants surrounded and nourished by gametophyte cells.

Zygote

A 2n (diploid) cell formed when sperm meets egg, which fuses to become an embryo, nourished by the gametangium, and develops into a multicellular sporophyte.

Alteration of Generations

The alteration between the diploid (2n) sporophyte stage and haploid (n) gametophyte stage in a plant's life cycle.

Sporophyte

The 2n (diploid) stage of a plant that produces spores.

Gametophyte

The n (haploid) stage of a plant that produces gametes.

Bryophytes

Non-vascular plants (mosses, liverworts, hornworts) where the gametophyte (n) is the dominant life stage.

Vascular plants

Plants with a vascular system where the sporophyte (2n) is the dominant, branched, and independent life stage.

Hydroids

Dead cells in mosses that form channels for efficient water movement, resembling vascular tissue.

Peristome teeth

Hygroscopic structures on the sporophyte capsule of mosses that change shape with humidity, allowing gradual spore dispersal.

Sphagnum Peat Moss

A type of moss that maintains peatland, covers 1% of Earth, stores 400 gigatons of CO2, and is found in places like the Everglades.

Gemma cup

An asexual reproductive structure in liverworts from which gemmae are dislodged by raindrops to establish new growth.

Elasters

Microscopic and hygroscopic helixes in liverworts that assist with spore dispersal by flexing in response to humidity.

Tracheophytes

A major clade of land plants, also known as vascular plants, characterized by a dominant, branched, independent sporophyte and the presence of tracheids, xylem, and phloem.

Tracheids

Dead, long, tapered, lignified cells in the xylem of vascular plants that transport water and minerals and provide structural support.

Xylem

A straw-like vascular tissue that transports water and nutrients from the roots to the leaves.

Phloem

A vascular tissue that moves photosynthetic products from the leaves to the rest of the plant.

Lycophytes (Club Mosses)

Vascular plants with independent sporophyte and gametophyte stages, microphylls instead of true leaves, and dichotomous branching sporangia in strobili.

Microphylls

Spiraled photosynthetic leaf-like structures found in lycophytes, not considered true leaves.

Homospore

A reproductive strategy producing a single type of spore that develops into a gametophyte with both male and female reproductive organs.

Heterospore

A reproductive strategy producing separate male microspores and female megaspores, leading to two types of gametophytes.

Euphyllophytes

All extant vascular plants except lycophytes, characterized by megaphylls, multiflagellated sperm, and roots with endogenous branching.

Megaphylls

Multi-veined leaves found in euphyllophytes, evolved from overtopped, flattened, and webbed branch systems.

Ferns

Vascular plants with an independent and dominant sporophyte, a short-lived gametophyte, sporangia on the back of fronds (sori), and that require water for sperm to travel.

Sori

Clusters of sporangia found on the back of fern fronds.

Epidermis (leaves/stem)

The outermost layer of leaves and stems that provides protection and minimizes desiccation through the secretion of a waxy cuticle.

Cortex

The tissue in a stem cross-section located between the epidermis and the vascular tissues.

Transpiration

The main driver of water movement in the xylem, where surface tension pulls water up.

Cohesion (water)

The property of water where H2O molecules cling to xylem sap due to hydrogen bonding.

Tension (water transport)

The pulling force that draws water from veins into the apoplast of mesophyll cells.

Apoplast

A pathway for water movement through the meshwork of cellulose in cell walls and intercellular spaces, where water never enters the cell and the plant has no control.

Symplast

A pathway for water movement across the cytoplasm of living cells connected by plasmodesmata, giving plants more control over transport.

Casparian Strip

A band that blocks water flow and dissolved substances from the apoplast pathway, forcing them to be filtered before entering the vascular cylinder.

Pressure Flow Model

The mechanism by which phloem distributes solutes of photosynthesized products (e.g., sucrose) throughout the plant, allowing fluid to flow both up and down.

Source cells (phloem)

Cells, typically in leaves, that produce sucrose and load it into the phloem, increasing its concentration.

Sink cells (phloem)

Cells, abundant in roots, fruits, and tips, that unload sucrose from the phloem where it is needed.

Spermatophytes (Seed Plants)

A group of plants characterized by producing secondary growth (wood), reduced gametophytes, heterospory, seeds, pollen, and a dominant sporophyte.

Primary Growth

Growth that makes a plant taller and its roots deeper, occurring at the apical meristem due to cell division and elongation.

Secondary Growth

Growth that makes a plant wider, occurring at secondary meristems like the vascular cambium and cork cambium.

Vascular cambium

A secondary meristem that produces secondary xylem (wood) and secondary phloem (inner bark).

Cork cambium

A secondary meristem that produces waxy-walled protective cells near the exterior of the stem, creating the outer bark.

Heartwood

Dead, old xylem that no longer functions in water transport.

Sapwood

Functioning xylem that actively transports water and nutrients.

Bark

Composed of living primary and secondary phloem, providing protection for the tree.

Periderm

The protective outer layer of a plant stem, including the cork cambium and cork.

Gymnosperms

Woody perennial seed-producing plants with 'naked seeds' (no protective ovary), no fruits or flowers, and only tracheids for water conduction (producing softwood).

Cycads

Subtropical gymnosperms with short, woody trunks, palm-like leaves, dioecious reproduction, symbiotic relationships with cyanobacteria, and motile, flagellated sperm.

Dioecious

Refers to plants that have separate male and female individuals.

Ginkgo

A gymnosperm genus with only one remaining species (Ginkgo biloba), characterized by motile, swimming sperm and dioecious reproduction.

Conifers

Well-branched gymnosperm trees with simple pinnate leaves, resin production, wind pollination, and non-motile sperm that requires a pollen tube for fertilization.

Gnetophytes

A bizarre group of gymnosperms sharing characteristics with angiosperms, such as fleshy cones, leaf morphology, and insect pollination.

Angiosperms

Flowering plants characterized by flowers, double fertilization, vessel elements in both xylem and tracheids, venation in leaves, seeds enclosed in a carpel, pollen germination on a stigma, and development of endosperm.

Flowers

Modified leaves and sporangia in angiosperms, sometimes functioning in protection and attraction.

Sepals (calyx)

Outermost floral parts that protect the bud and can aid in attraction.

Petals (corolla)

Often colorful floral parts that protect inner structures and attract pollinators.

Stamens

The male reproductive organ of a flower, consisting of an anther (location of male sporangium) and a filament.

Carpel (megaphyll)

An enclosed modified leaf within a flower that contains ovules and seeds.

Pistil

The female reproductive organ of a flower, consisting of fused carpels and containing the ovaries, style, and stigma.

Stigma

The receptive tip of a carpel or pistil that receives and transmits pollen to the ovaries.

Double Fertilization (angiosperms)

A unique process in angiosperms where two sperm cells fertilize the egg to form the embryo and the central cell to form the endosperm (3n).

Endosperm (angiosperm)

A 3n nutrient-rich tissue created during double fertilization that provides nourishment for the developing seed.

Cotyledon

Seed leaves within an angiosperm embryo that absorb and digest endosperm, and may become photosynthetic upon germination.

Perfect flower

A flower that contains both megasporangia (female) and microsporangia (male) reproductive organs.

Imperfect flower

A flower that contains either megasporangia (female) or microsporangia (male) reproductive organs, but not both.

Inbreeding depression

A reduction in fitness caused by self-fertilization in perfect flowers, due to the unmasking of deleterious recessive mutations.

S locus protein

A genetic mechanism that prevents inbreeding by rejecting pollen when its protein on the pollen coat matches an identical protein on the stigma.

Heterostyly

The production of flowers with different forms (e.g., pin or thrum flowers) as a structural mechanism to prevent self-pollination.

Chasmogamous flowers

Open flowers that promote genetic diversity through cross-pollination.

Cleistogamous flowers

Closed flowers that achieve self-fertilization.

Pollination Syndromes

Specific traits in flowers that have evolved to attract particular types of pollinators (e.g., bee, fly, moth, hummingbird, wind).

Photorespiration

An alternative process to photosynthesis that occurs in conditions of high O2, low CO2, high temperature, and high light, where the enzyme RuBisCo uses O2 instead of CO2, producing no useful energy or sugar.

C3 plants

The most common type of plant, where carbon fixation occurs when RuBisCo adds CO2 to RuBP, producing a 3-carbon compound.

C4 plants

Plants that fix CO2 into a 4-carbon compound, separating carbon fixation from the Calvin cycle spatially (e.g., in mesophyll and bundle sheath cells), allowing photosynthesis to continue even when stomata are closed.

CAM Plants

Plants that separate carbon fixation from the Calvin cycle temporally, opening stomata at night to take in CO2 and storing it until daytime to make sugar.

Carnivorous plants

Plants found in nutrient-poor soils (especially low nitrogen) that acquire nitrogen and other nutrients by eating insects.

Mycoheterotrophs

Plants whose roots have a symbiotic relationship with mycorrhizal fungi, where the plant gains nutrients from the fungus and the fungus gains carbon.

Parasitic Plants

Plants that obtain nutrients by feeding on a host plant.

Hemiparasites

Parasitic plants that still carry out photosynthesis but supplement their nutrients by stealing from a host.

Holoparasites

Parasitic plants that do NOT photosynthesize and are entirely dependent on their host plant for nutrients.

Constitutive defenses

Plant defenses that are always present, such as outer surface protection (cuticle, bark), trichomes, thorns, prickles, spines, laticifers, or secondary metabolites.

Trichomes

Hair-like structures on plants that serve as a constitutive defense.

Secondary metabolites

Non-essential substances produced by plants (e.g., terpenoids, alkaloids, phenolics) used to repel or inhibit herbivores as a constitutive defense.

Induced defenses

Plant defenses produced in reaction to the presence of a pathogen, herbivore, or other threat.

Elicitors

Molecules, often coded for by Avr (avirulence) genes, that trigger plant defenses.

R (resistance gene)

A plant gene that recognizes specific elicitors and confers resistance to a pathogen.

Localized Response (plant defense)

An immediate, localized reaction to a wound or parasitic attack, involving phytoalexins, pathogenesis-related (PR) proteins, and physical isolation.

Phytoalexins

Antibiotic compounds produced by plants as part of a localized defense response against bacteria and fungi.

Systemic Response (plant defense)

A broad-spectrum protection against pathogens that develops throughout the plant after an initial attack, often involving the jasmonate pathway and phloem-traveling protective measures.

Auxin

A plant hormone that controls growth and development, causes phototropism, influences gravitropism, and contributes to apical dominance.

Phototropism

The bending of plant stems towards a light source, caused by auxin concentrating on the side facing away from the light.

Gravitropism

The growth response of a plant in relation to gravity, where roots typically grow down (positive) and stems grow up (negative), influenced by auxin.

Apical dominance

The inhibition of axillary buds by apical buds, typically resulting in a triangular plant shape, a process influenced by auxin.

Ethylene Gas

A plant hormone that promotes leaf abscission and senescence, speeds fruit ripening, reduces growth, affects phototropism, and promotes seed germination in some species.

Phytochromes

Plant photoreceptors that exist in two isoforms (Pr and Pfr) and determine processes like seed germination, shoot development, and flowering.