LABS 12-15 bold structures, functions, and phyla traits

What five shared derived traits distinguish land plants from green algae?

1. Alternation of generations, 2. Multicellular dependent embryos, 3. Walled spores produced in sporangia, 4. Multicellular gametangia (antheridia and archegonia), 5. Apical meristems

What is the primary function of an apical meristem in land plants?

It consists of localized regions of cell division at the tips of roots and shoots that allow continuous growth.

What is the key evolutionary distinction between non-vascular plants (bryophytes) and vascular plants?

Non-vascular plants lack specialized vascular tissues (xylem and phloem) for water and nutrient transport, making the haploid gametophyte the dominant life cycle stage.

Which plant structure produces eggs, and is it male or female?

The archegonium, which is the female multicellular gametangium.

Which plant structure produces sperm, and is it male or female?

The antheridium, which is the male multicellular gametangium.

In bryophytes (mosses and liverworts), which stage of the life cycle is photosynthetically dominant and independent?

The haploid gametophyte stage.

Identify the cup-like structure shown in a liverwort cross-section

Gemma cup (containing gemmae for asexual reproduction in Phylum Hepatophyta).

What is the biological function of a gemma cup in liverworts (Phylum Hepatophyta)?

Asexual reproduction through the production and dispersal of gemmae clones by raindrops.

How do rhizoids differ structurally and functionally from true roots?

Rhizoids are cellular filaments that anchor non-vascular plants/gametophytes without specialized vascular tissue, whereas true roots possess xylem and phloem to transport water and nutrients.

What is the main structural difference between rhizoids and rhizomes?

Rhizoids are root-like anchoring filaments lacking vascular tissue, whereas rhizomes are underground vascular stems used for growth and asexual propagation.

What is the difference between microphylls and megaphylls?

Microphylls are small leaves with a single unbranched vein (found in lycophytes), while megaphylls are larger leaves with a branched network of veins (found in monilophytes and seed plants).

What defines a homosporous plant?

A plant that produces a single type of spore that typically develops into a bisexual (hermaphroditic) gametophyte.

What defines a heterosporous plant?

A plant that produces two distinct types of spores: microspores (male) and megaspores (female).

In the phylogeny of land plants, which group represents the earliest-diverging lineage of vascular plants?

Lycophytes (club mosses, spike mosses, quillworts).

To which phylum do ferns, horsetails, and whisk ferns belong?

Phylum Monilophyta (also known as Pterophyta).

In seedless vascular plants like ferns, which life cycle stage is dominant and independent?

The diploid sporophyte stage.

What are sori (singular: sorus) on a fern frond?

Clusters of spore-producing sporangia located on the underside of megaphyll fronds.

What is the function of the indusium in fern anatomy?

A protective, shield-like flap of tissue covering the sporangia within a sorus.

What is the fern prothallus?

The tiny, heart-shaped haploid gametophyte stage of a fern that produces antheridia and archegonia.

On a heart-shaped fern gametophyte, where are the archegonia and antheridia typically located?

Archegonia are located near the notch of the heart shape, while antheridia are scattered among the rhizoids at the basal end.

Why are seedless vascular plants and bryophytes restricted to moist habitats for sexual reproduction?

They produce flagellated sperm that require a film of water to swim from antheridia to archegonia to fertilize the egg.

What type of sporangial arrangement is visible in a lycophyte strobilus longitudinal section?

A heterosporous strobilus containing both megasporangia (with large megaspores) and microsporangia (with small microspores).

What three structural components comprise a plant seed?

1. A protective seed coat (derived from integument),

2. An embryo (young diploid sporophyte),

3. A food supply (megagametophyte in gymnosperms or endosperm in angiosperms).

What is the primary evolutionary advantage of producing seeds over spores?

Seeds provide multi-layered protection, an internal nutrient supply for early growth, and the capacity to remain dormant through unfavorable conditions.

What is pollination?

The transfer of pollen grains (male microgametophytes) to the proximity of the female ovule or stigma.

How does pollination differ from fertilization in seed plants?

Pollination is the physical transfer of pollen to the female structure, whereas fertilization is the subsequent fusion of egg and sperm nuclei.

What adaptation allows gymnosperm pollen to travel long distances through the air?

A pair of lateral air bladders ("wings") attached to the central body of the pollen grain.

In gymnosperm anatomy, what structure directly surrounds the megasporangium and eventually matures into the seed coat?

The integument.

Which gymnosperm phylum contains palm-like plants with flagellated sperm and large woody cones?

Phylum Cycadophyta.

What does it mean for a plant species to be dioecious?

Male and female reproductive structures (cones or flowers) are produced on separate individual plants.

What does it mean for a plant species to be monoecious?

Both male and female reproductive structures are produced on the same individual plant.

Which gymnosperm phylum features non-motile sperm, includes desert and tropical species, and can be dioecious or monoecious?

Phylum Gnetophyta.

What is the male reproductive cone in gymnosperms called, and what spores does it produce?

Staminate cone (male cone), which produces microspores within microsporangia.

What is the female reproductive cone in gymnosperms called, and what spores does it produce?

Ovulate cone (female cone), which produces megaspores within megasporangia (ovules).

What key structural feature defines angiosperms ("vessel seeds") compared to gymnosperms ("naked seeds")?

Angiosperms enclose their seeds within a protective receptacle called an ovary (which matures into a fruit).

What are the two sterile whorls of a typical flower?

Sepals (calyx) and petals (corolla).

What two structures make up the male microsporophyll (stamen) of a flower?

The anther (contains microsporangia) and the filament (supporting stalk).

What three structures make up the female megasporophyll (carpel or pistil) of a flower?

The stigma (pollen receptive surface), style (connecting tube), and ovary (contains ovules).

Where does microsporogenesis take place within an angiosperm flower?

Inside the microsporangia (pollen sacs) of the anther.

Where does megasporogenesis take place within an angiosperm flower?

Inside the megasporangium of the ovule within the ovary.

What floral structure matures into the fruit after fertilization?

The ovary wall (pericarp).

What floral structure matures into the seed after fertilization?

The ovule.

What is the main selective advantage of animal pollination over wind pollination in angiosperms?

Animal pollination is targeted and efficient, reducing the amount of pollen required for successful fertilization compared to random wind dispersal.

How are vascular bundles arranged in a cross-section of a monocot stem (e.g., Zea mays)?

Vascular bundles are scattered throughout the ground tissue.

How are vascular bundles arranged in a cross-section of a eudicot/dicot stem (e.g., Ranunculus)?

Vascular bundles are arranged in a distinct ring surrounding a central pith.

In angiosperm stem cross-sections, what two main vascular tissues are present inside each vascular bundle?

Xylem (transports water and minerals) and phloem (transports sugars and organic nutrients).

What is double fertilization in angiosperms?

A process where one sperm nucleus fertilizes the egg cell to form a 2n zygote, while a second sperm nucleus fuses with two polar nuclei to form a triploid (3n) endosperm.

What is the nutritional role of the endosperm in an angiosperm seed?

It acts as a nutrient-rich storage tissue that nourishes the developing embryo sporophyte.

In the Kirby-Bauer antimicrobial susceptibility test, what is the zone of inhibition?

The clear circular area around an antibiotic disc where bacterial growth is inhibited.

How is the zone of inhibition measured in a Kirby-Bauer disk diffusion test?

By measuring the total diameter of the clear zone across the disk in millimeters (mm).

How do you determine if a bacterium is resistant, intermediate, or susceptible to an antibiotic in a Kirby-Bauer assay?

By measuring the zone of inhibition diameter and comparing it to standard interpretive reference charts.

What is the difference between a homosporous plant and a heterosporous plant?

Homospory produces one spore type that grows into a bisexual gametophyte, while heterospory produces microspores (male) and megaspores (female).

What three structural components comprise a plant seed?

1. Protective seed coat, 2. Diploid embryo, 3. Food supply (endosperm or megagametophyte).

What is the primary evolutionary advantage of producing seeds over spores?

Seeds provide multi-layered protection, an internal food supply, and the ability to stay dormant through harsh conditions.

What is the main selective advantage of animal pollination over wind pollination in angiosperms?

Animal pollination is targeted and efficient, requiring much less total pollen than random wind dispersal.

How are vascular bundles arranged in a monocot stem vs. a eudicot/dicot stem?

Monocot = scattered vascular bundles. Dicot = vascular bundles arranged in a distinct ring around a central pith.

What is double fertilization in angiosperms?

One sperm fertilizes the egg to form a 2n zygote, and a second sperm fuses with two polar nuclei to form a triploid (3n) endosperm.

What is the zone of inhibition in a Kirby-Bauer test?

The clear circular area around an antibiotic disc where bacterial growth is inhibited; measured in millimeters (mm) to determine susceptibility.