Plant Form, Function, Diversity, and Reproduction

Comprehensive practice flashcards covering plant evolution, derived characteristics, nonvascular bryophytes, seedless vascular plants, anatomical adaptations, life cycles, and paleobotanical fossils.

How do holoparasitic plants like Rafflesia arnoldii differ physiologically from hemiparasitic plants like mistletoe (Viscum spp.)?

Holoparasitic plants are complete parasites that perform no photosynthesis, whereas hemiparasitic plants are photosynthetic while also obtaining water and nutrients from their host.

What is a haustorium in parasitic plants?

A specialized feeding structure that penetrates host tissues to extract water and nutrients.

What parasitic plant species is shown here, recognized as having the largest flower in the world?

Rafflesia arnoldii (corpse flower)

Why do mixotrophic carnivorous plants, such as Venus flytraps, capture insects even though they carry out photosynthesis?

To obtain nitrogen and other essential nutrients that are scarce in their native environments.

How do plants explore their environment through indeterminate growth using phototropism, hydrotropism, and chemotropism?

Shoots grow toward light (phototropism) for photosynthesis, while roots grow toward water (hydrotropism) and mineral nutrients (chemotropism).

What cellular components form the primary and secondary cell walls of plants?

Cellulose forms the primary cell wall, while lignin forms the thicker secondary cell wall.

How does turgor pressure regulate stomatal opening and closing in plant leaves?

When turgor pressure increases, stomata open to allow gas exchange; when turgor pressure decreases, stomata close to prevent water loss.

How does the sensitive plant Mimosa pudica respond to mechanical vibrations?

It rapidly alters turgor pressure in leaf cells, causing its leaves to fold up in response to mechanical vibrations that could indicate an herbivore.

What five derived traits appear in nearly all land plants but are absent in charophyte algae?

1. Alternation of generations; 2. Multicellular gametangia; 3. Multicellular, dependent embryos; 4. Walled spores produced in sporangia; 5. Apical meristems.

In plant alternation of generations, what are the respective ploidies and reproductive outputs of sporophytes and gametophytes?

The diploid ($2n$) sporophyte produces haploid spores via meiosis, while the haploid ($n$) gametophyte produces haploid gametes (sperm and eggs) via mitosis.

What are the two types of multicellular gametangia, and what gametes do they produce?

Archegonia produce and protect eggs (female), while antheridia produce and release sperm (male).

What is the function of placental transfer cells in embryophytes such as Marchantia?

They facilitate nutrient and water transfer from the maternal parent gametophyte to the developing multicellular embryo through elaborate cell wall ingrowths.

What are sporangia, and what protective adaptation do plant spores possess for terrestrial survival?

Sporangia are multicellular organs where spores are formed through meiosis; spores are encased in sporopollenin, which protects against desiccation and UV radiation.

What is an apical meristem, and where is it located in a plant?

A region of actively dividing, undifferentiated cells located at the tips of roots and shoots that enables continuous growth.

What defines the clade Viridiplantae?

A clade of photosynthetic eukaryotes that contain chlorophyll $a$ and $b$ and store starch inside chloroplasts.

According to fossil evidence, when did land plants originate, and when did Cooksonia appear?

Land plants originated from green algae about $470\text{ million years ago}$, and Cooksonia, the earliest vascular plant, appeared by $425\text{ million years ago}$ in the Silurian Period.

How does the life cycle of Chara corallina differ fundamentally from the embryophyte life cycle?

Chara has a multicellular haploid body with no multicellular diploid generation; its diploid zygote undergoes meiosis directly to yield four haploid cells.

What were the primary environmental benefits and challenges encountered during the plant transition to land?

Benefits included unfiltered sunlight, abundant $\text{CO}_2$, nutrient-rich soil, and few initial pathogens; challenges included water scarcity, lack of structural support against gravity, and gamete/offspring desiccation.

What major evolutionary trend in generation dominance occurs across embryophytes from bryophytes to seed plants?

The gametophyte generation progressively decreases in size and independence, while the sporophyte generation becomes larger, dominant, and photosynthetic.

What are the four major evolutionary transformations of embryophytes shown on their phylogenetic tree?

1. Alternation of generations and protected embryos; 2. Evolution of xylem and phloem; 3. Evolution of seeds and pollen; 4. Evolution of flowers and fruits.

How do bryophytes, lycophytes, and ferns compare to seed plants in their mechanisms of fertilization and dispersal?

Bryophytes, lycophytes, and ferns require water for flagellated sperm fertilization and disperse spores through the air; seed plants use air for pollen-mediated fertilization and air (or animals) for seed dispersal.

Approximately what percentage of the nearly $400,000$ living plant species do angiosperms comprise?

Approximately $90\%$ ($>380,000$ species).

Why can angiosperms typically transport water and $\text{CO}_2$ more efficiently than gymnosperms?

Angiosperms possess higher leaf vein densities, facilitating more rapid water transport to sustain high stomatal conductance and photosynthesis.

Why are bryophytes constrained to small sizes ($<5\,\text{cm}$ height)?

They lack vascular tissues (xylem and phloem) with lignified cell walls, forcing water to move solely cell-to-cell.

What structural parts comprise the bryophyte sporophyte that grows attached to the gametophyte?

The foot (nutrient uptake from the gametophyte), seta (stalk), capsule (sporangium where meiosis occurs), and operculum (capsule lid).

Under what environmental condition do moss sporangia typically release spores, and why?

Under dry conditions, because moisture can cause tiny, lightweight spores to clump together and fall directly to the ground instead of being dispersed by wind.

What are rhizoids, and how do their functions differ from true roots?

Filamentous root-like structures that anchor bryophytes to their substrate; unlike true roots, they lack vascular tissue and do not serve as the primary organs for water and nutrient uptake.

What are the distinguishing vegetative and reproductive features of hornworts (Phylum Anthocerophyta)?

They possess a flattened photosynthetic thallus for a gametophyte and elongated, horn-like sporophytes that grow continuously from their base.

What are the cup-like structures visible on this liverwort thallus, and what is their function?

Gemmae cups, which produce vegetative propagules called gemmae for asexual reproduction (cloning).

How does Sphagnum (peat moss) modify wetland chemistry to impede decomposition?

It retains large quantities of water in specialized dead cells, secretes protons to acidify surrounding water, and produces phenolic compounds that inhibit microbial activity.

What proportion of Earth's land surface is covered by peat bogs, and how much organic carbon do they store?

Peat bogs occupy $2\%$ to $3\%$ of the global land surface and store organic carbon equal to approximately $65\text{ times}$ the annual global release from fossil fuel combustion.

What Iron Age bog body, shown here, demonstrates the exceptional preservation provided by the acidic and anoxic conditions of Sphagnum bogs?

Tollund Man (discovered in 1950 in a Danish peat bog)

What primitive anatomical characteristics did the early vascular plant Aglaophyton major from the Rhynie Chert exhibit?

Dichotomously branching leafless photosynthetic stems with terminal sporangia, stomata embedded in a waxy cuticle, and hairlike rooting rhizoids along horizontal axes.

What mechanical role does lignin play in the secondary cell walls of xylem vessels?

It reinforces the cell walls against collapse caused by negative pressure during transpiration and provides structural rigidity for upright, tall growth.

What structural leaf types are contrasted in this diagram?

Microphylls (top, containing a single unbranched vascular vein) and megaphylls (bottom, containing a branched network of veins).

What are strobili, and what advantages do they provide to plants like lycophytes and horsetails?

Tightly packed clusters of sporangium-bearing sporophylls that protect sporangia and elevate spores above ground level for wider aerial dispersal.

How do homosporous and heterosporous spore production pathways differ in seedless vascular plants?

Homosporous plants produce a single type of spore that yields a bisexual gametophyte (producing both eggs and sperm), whereas heterosporous plants produce megaspores (yielding female gametophytes with eggs) and microspores (yielding male gametophytes with sperm).

What extinct Carboniferous arborescent lycophyte produced the fossilized bark with diamond-shaped leaf cushion scars shown in this image?

Lepidodendron sternbergii

What form-genera names designate the leaves, cones, and rooting axes of giant Carboniferous lycophytes?

Lepidophylloides designates the leaves, Lepidostrobus designates the cones/strobili, and Stigmaria designates the rooting axes with appendages.

What are coal balls, and what is their significance in paleobotany?

Mineralized concretions that permineralize uncompressed peat, preserving internal three-dimensional cellular anatomy of Carboniferous swamp plants.

What is the structural organization of a typical fern leaf (frond)?

A frond is divided into individual leaflets called pinnae (often $<2\,\text{cm}$ wide), which can be further subdivided into pinnules.

What is the term for the young, coiled fern frond shown in this image?

Fiddlehead (crozier)

What distinctive anatomical features characterize the genus Equisetum (horsetails)?

Hollow, ribbed stems with high levels of abrasive silica, and tiny, non-photosynthetic leaves arranged in whorls around jointed nodes.

How do tree ferns reach heights of up to $10\,\text{m}$ without producing true woody secondary xylem?

They achieve mechanical support via an extensive, rigid outer mantle of interlocking adventitious roots that encase the slender stem.

What symbiotic relationship enables the tiny water fern Azolla to serve as a natural biofertilizer in flooded rice paddies?

A symbiotic relationship with nitrogen-fixing cyanobacteria that reside within specialized cavities inside Azolla leaves.

What are the three-lobed yellow reproductive structures visible on the stem of the whisk fern Psilotum nudum in this image?

Synangia (fused groups of three sporangia)