BIOL204 Exam 2 Lecture 14-16 Flashcards

Archaeplastida

A eukaryotic supergroup containing red algae, green algae, and land plants.

Major members of Archaeplastida

Red algae, green algae, and land plants.

Green algae

A paraphyletic group consisting of chlorophytes and charophytes; they include unicellular, colonial, filamentous, and thalloid forms.

Chlorophytes

One of the two major green-algae clades.

Charophytes

One of the two major green-algae clades and the green-algae group most closely related to land plants.

Paraphyletic

A group containing a common ancestor and some, but not all, of its descendants.

Plant and green-algae synapomorphies

Chloroplasts with chlorophyll a and b, stacked thylakoids, starch storage, and cellulose cell walls.

Chloroplast function

The organelle where photosynthesis occurs; it captures light energy to produce chemical energy.

Thylakoids

Membrane sacs inside chloroplasts that contain photosynthetic pigments and are stacked into grana.

Grana

Stacks of thylakoids inside chloroplasts.

Chlorophyll a and b

Photosynthetic pigments that absorb light energy.

Starch

A carbohydrate used for energy storage in green algae and land plants.

Cellulose

A glucose polymer forming the cell walls of plants and green algae; its glucose linkages are beta-1,4.

Starch versus cellulose

Starch has alpha-1,4 glucose linkages, whereas cellulose has beta-1,4 glucose linkages.

Biofuel importance of green algae

Some green algae are studied as potential sources of renewable fuels and green products.

Land plants (Embryophyta)

Plants whose zygotes are retained within tissues of the female parent and develop into protected embryos.

Approximate origin of land plants

About 470-500 million years ago.

Embryophyte

A land plant; the name emphasizes that the developing embryo is retained and protected by the parent.

Why plants colonized land successfully

They evolved adaptations that reduced water loss, protected gametes and spores, supported growth, and protected and nourished embryos.

Apical meristem

A localized region of cell division at the tips of roots and shoots.

Function of apical meristems

They allow mitosis throughout life, elongating roots and shoots and increasing access to environmental resources.

Cuticle

A waxy covering on plant surfaces that reduces water loss and helps prevent desiccation.

Thick spore walls

Protect spores from drying and other harsh environmental conditions.

Sporopollenin

A highly resistant polymer in spore walls and pollen walls that protects them from desiccation and environmental damage.

Gametangia

Protective cases that enclose plant gametes and help prevent them from drying out.

Archegonium

The female gametangium; it encloses and protects the haploid egg.

Antheridium

The male gametangium; it produces or encloses haploid sperm.

Archegonia versus antheridia

Archegonia contain eggs; antheridia contain sperm.

Alternation of generations

A life cycle alternating between a multicellular haploid gametophyte and a multicellular diploid sporophyte.

Gametophyte

The haploid (n) generation that produces haploid gametes by mitosis.

Sporophyte

The diploid (2n) generation that produces haploid spores by meiosis.

What fertilization produces

The fusion of haploid gametes produces a diploid zygote, which develops into the sporophyte.

What meiosis produces in plants

Haploid spores, not gametes.

What mitosis produces in the gametophyte

Haploid gametes.

Why gametes are produced by mitosis in plants

The gametophyte is already haploid, so mitosis preserves the haploid chromosome number.

Dependent embryo

A multicellular embryo retained in protective parent tissue and supplied with nutrients by the parent.

Foot

The structure of a bryophyte sporophyte that absorbs nutrients from the gametophyte and transfers them to the sporangium.

Seta

The stalk of a bryophyte sporophyte that supports the capsule.

Capsule

The sporangium at the tip of a bryophyte sporophyte where spores are produced.

Peristome

A tooth-like structure around the opening of some moss capsules that helps regulate spore release.

Bryophytes

The traditional grouping of liverworts, mosses, and hornworts.

Bryophyte life-cycle traits

Gametophyte dominant, motile sperm requiring water, and no vascular tissue.

Bryophyte gametophyte

The dominant, long-lived generation.

Bryophyte sporophyte

A small, short-lived generation dependent on the gametophyte for nutrition.

Bryophyte sperm

Flagellated and motile; water is needed for sperm to reach the egg.

Do bryophytes form a monophyletic group?

In the lecture treatment, bryophytes are presented as a monophyletic group consisting of hornworts, liverworts, and mosses.

Hornwort stomata

Hornworts have stomata, which function in gas exchange and water retention and are also characteristic of vascular plants.

Stomata

Adjustable pores that allow gas exchange while helping regulate water loss.

Ecological importance of bryophytes

They can help retain nitrogen, sometimes through associations with nitrogen-fixing cyanobacteria, and can inhabit extreme environments.

Moss habitats

Mosses can live in northern coniferous forests, high elevations, tundra, and deserts.

Peat moss (Sphagnum)

A moss used as fuel and soil conditioner; peatlands also act as major carbon sinks.

Peat moss and carbon

Sphagnum peatlands store large amounts of carbon in their soils and cover a substantial fraction of Earth’s land surface.

Vascular plants (Tracheophyta)

Land plants with lignified vascular tissue and a dominant sporophyte generation.

Earliest vascular-plant fossils

They date to approximately 430 million years ago; Cooksonia is an early example.

Rhyniophytes

Early-diverging vascular plants such as Cooksonia that lacked true roots and leaves.

Vascular tissue

A conducting system that transports water, minerals, sugars, amino acids, and other nutrients through the plant.

Tracheophyte synapomorphies

A dominant sporophyte and lignified vascular tissue containing xylem and phloem.

Tracheophyte sporophyte

The dominant, larger, longer-lived generation.

Tracheophyte gametophyte

Usually a much smaller generation; in seedless vascular plants it may initially be independent, while in seed plants it is reduced and dependent.

Lignin

A hydrophobic strengthening polymer in vascular tissue, especially xylem; it provides structural support and helps water-conducting cells resist collapse.

Xylem

Vascular tissue that conducts most water and minerals, generally from roots toward shoots; it contains tracheids.

Tracheids

Tube-shaped, lignin-strengthened xylem cells that conduct water and minerals and provide support.

Phloem

Vascular tissue that distributes sugars, amino acids, and other organic products of photosynthesis.

Why vascular tissue was evolutionarily important

It allowed plants to transport materials efficiently, grow taller, and develop larger bodies.

First trees

Selection for taller growth contributed to the evolution of the first trees approximately 385 million years ago.

Tracheophyte organ systems

Shoots containing stems, leaves, and reproductive organs, plus roots.

Early vascular plants and roots/leaves

Some early tracheophytes, including Cooksonia, lacked true roots and leaves.

Leaf function

Leaves increase surface area for capturing solar energy used in photosynthesis.

Microphyll

A leaf with a single, unbranched vascular vein; characteristic of lycophytes.

Megaphyll

A leaf with a highly branched vascular system, allowing greater photosynthetic surface and efficiency.

Microphyll fossil age

Microphylls appear in the fossil record around 410 million years ago.

Megaphyll fossil age

Megaphylls appear in the fossil record around 370 million years ago.

Sporophyll

A modified leaf that bears sporangia containing spores.

Sorus (plural sori)

A cluster of sporangia, commonly on the underside of a fern sporophyll.

Strobilus (plural strobili)

A cone-like structure made of groups of sporophylls; common in lycophytes and most gymnosperms.

Homosporous

Producing one type of spore from one type of sporangium; the spore develops into a bisexual gametophyte.

Heterosporous

Producing two types of spores: microspores and megaspores.

Homosporous plant life cycle

One spore type produces a bisexual gametophyte with both antheridia and archegonia.

Heterosporous plant life cycle

Microspores produce male gametophytes, while megaspores produce female gametophytes.

Most seedless vascular plants

They are homosporous, including most ferns.

Seed plants

They are heterosporous; all seed plants produce microspores and megaspores.

Lycophytes

Seedless vascular plants with microphylls; their extinct relatives included enormous tree forms.

Extinct lycopods

Tall Carboniferous trees such as Lepidodendron that contributed substantially to modern coal deposits.

Lepidodendron

An extinct, tree-sized lycopod from ancient swamp forests.

Monilophytes

A vascular-plant lineage including ferns and horsetails.

Ferns

Seedless vascular plants with true roots and megaphylls; the traditional fern grouping is paraphyletic in the lecture.

Horsetails (Sphenophytes)

Seedless vascular plants with jointed stems, microphylls arranged in whorls, rhizomes, and strobili.

Equisetum

The only surviving horsetail genus; its cell walls contain silica.

Horsetail identification

Straight, jointed stems ringed by whorled microphylls and often topped by cones (strobili).

Rhizome

A horizontal stem from which horsetail roots can arise.

Whisk fern (Psilotum)

A living-fossil-like plant with simple sporangia, no true roots or leaves, and homospory.

Significance of seedless vascular plants

Their ancestors formed the first forests, grew very tall, altered atmospheric CO2, contributed to cooling and glaciation, and eventually formed coal.

Carboniferous forests

Forests from about 359-299 million years ago dominated by large seedless vascular plants.

Seedless vascular plants and climate

Their high growth and photosynthesis removed CO2, possibly contributing to global cooling near the end of the Carboniferous.

Coal formation

Decaying plants from Carboniferous swamp forests were buried and eventually transformed into coal.

Spermatophyta

The seed-plant lineage containing gymnosperms and angiosperms.

Seed-plant synapomorphies

Seeds, highly reduced gametophytes, heterospory, pollen, and ovules.

Key feature distinguishing seed plants from other plants

Ovules, together with seeds, pollen, heterospory, and reduced dependent gametophytes.

Seed-plant gametophyte

Usually microscopic, highly reduced, and nutritionally dependent on surrounding sporophyte tissue.

Seed-plant sporophyte

The dominant generation.