BISC 120 Midterm 3 | 17 Land Plants

How are photosynthesis and respiration linked?

Photosynthesis produces sugars and oxygen. Respiration uses them to obtain ATP and releases carbon dioxide and water.

Why are algae an informal, polyphyletic group?

Algae are photosynthetic eukaryotes from several evolutionary lineages. They include unicellular microalgae and multicellular macroalgae.

What are the three main parts of a macroalga?

The holdfast anchors it, the stipe is stem-like, and the photosynthetic blade or lamina is leaf-like.

How do Viridiplantae, embryophytes, and tracheophytes nest?

Viridiplantae includes green algae and land plants. Embryophytes are land plants. Tracheophytes are the vascular land plants: seedless vascular plants, gymnosperms, and angiosperms.

Which algal lineage is closest to land plants, and what four clues support it?

Charophytes. The clues are cellulose synthase rosettes, flagellated sperm structure, sporopollenin, and nuclear, chloroplast, and mitochondrial DNA similarities.

What opportunities and challenges came with life on land?

More direct light, carbon dioxide, and soil nutrients were available. Water scarcity and support against gravity were challenges.

How could early mycorrhiza-like partnerships help land plants before true roots evolved?

Fungal partners helped plants acquire water and mineral nutrients.

What four derived traits does Lecture 17 highlight for land plants?

Alternation of generations, apical meristems, multicellular gametangia, and walled spores in sporangia.

What makes land plants embryophytes?

The embryo is retained and nourished on the parent.

How do cuticle and stomata balance water loss and gas exchange?

Waxy cuticle limits water loss. Stomata open for gas exchange and close to conserve water.

Where are apical meristems, and what do they do?

At shoot and root tips. Self-renewing, undifferentiated cells divide to extend the plant and give rise to tissues.

Why is post-embryonic organ formation useful to sessile plants?

A plant can adjust how many organs it makes and how they grow in response to local conditions.

What alternates in alternation of generations?

A multicellular haploid gametophyte and a multicellular diploid sporophyte.

Who makes gametes, and by which division?

The haploid gametophyte makes haploid gametes by mitosis.

Who makes spores, and by which division?

The diploid sporophyte makes haploid spores by meiosis in sporangia.

Which are haploid and which are diploid: sporangium, spore, gametangium, gamete, zygote, and embryo?

Sporangium, zygote, and embryo are 2n. Spore, gametangium, and gamete are n.

What two steps change ploidy in the plant life cycle, and what grows from their products?

Fertilization makes a 2n zygote, which grows by mitosis into a sporophyte. Meiosis produces n spores, which grow by mitosis into gametophytes.

What distinguishes a plant spore from a gamete?

A spore germinates without fusing. Gametes fuse in fertilization.

What are antheridia and archegonia, and where does moss fertilization occur?

Antheridia produce sperm, archegonia contain eggs, and moss fertilization occurs in an archegonium.

In a moss diagram, which generation is the leafy plant and which is the attached stalk and capsule?

The green leafy part is the independent n gametophyte. The attached stalk and capsule form the dependent 2n sporophyte. The capsule is the sporangium.

Trace the moss cycle from a spore to the next spore-producing structure.

Spore → protonema → bud → gametophyte → gametes → fertilization → zygote → embryo → attached sporophyte with a capsule that makes spores by meiosis.

In what order did land plants, vascular tissue, and seeds appear, and how did gametophytes change?

Land plants first, then vascular tissue, then seeds. Moss gametophytes dominate, fern gametophytes are smaller but free-living, and seed-plant gametophytes are reduced and protected.