Plant diversity 7

What are some key features of land plants?

Multicellular, photosynthetic (chlorophyll a & b), cellulose cell walls, alternation of generations, protected embryo, cuticle, stomata, vascular tissue (in most).

What is the evolutionary origin of land plants?

Evolved from green algae (charophytes); share traits like chlorophyll a & b, cellulose, and similar cell division.

How have plants adapted to life on land?

• Prevent water loss: cuticle, stomata

• Support against gravity: vascular tissue, lignin

• Reproduction without water: pollen, seeds

• Dispersal: spores, seeds, fruits

Plants What are the major groups? How are they similar/different?

1. Bryophytes (mosses, liverworts, hornworts) – non-vascular, need water for fertilization

2. Ferns (pteridophytes) – vascular, seedless, spores for dispersal

3. Gymnosperms (conifers, cycads, ginkgo) – vascular, seeds (naked), pollen

4. Angiosperms (flowering plants) – vascular, seeds (enclosed in fruit), flowers, double fertilization

Similarity: All have alternation of generations, multicellular embryos, photosynthetic.
Difference: Vascular tissue, seeds, flowers/fruits, water dependency for fertilization.

What is alternation of generations?

A: Life cycle alternates between haploid gametophyte (n) and diploid sporophyte (2n) generations.

How does alternation of generations vary among plants?

• Mosses: Gametophyte dominant, sporophyte dependent on gametophyte.

• Ferns: Sporophyte dominant, independent gametophyte.

• Gymnosperms: Sporophyte dominant, gametophyte reduced, pollen/ovules.

• Angiosperms: Sporophyte dominant, gametophyte highly reduced (pollen & ovule), double fertilization.

What organism most closely resembles the ancestor of land plants?

Charophyte green algae (stoneworts).

Key features distinguishing major groups:

• Bryophytes: Non-vascular, need water for fertilization

• Ferns: Vascular, spores, independent sporophyte

• Gymnosperms: Seeds, pollen, cones

• Angiosperms: Flowers, fruits, double fertilization

Challenges on Land & Plant Adaptations Q: Challenges? Adaptations?

Challenge	Adaptation
Water loss	Cuticle, stomata
Gravity/support	Lignin, vascular tissue
Fertilization without water	Pollen, seeds
Dispersal	Spores, seeds, fruits
UV damage	Flavonoids, pigments

Bryophytes (Mosses) Key features Alternation of generations?

Non-vascular, rhizoids, water-dependent fertilization, gametophyte dominant.

Gametophyte dominant; sporophyte grows on gametophyte, releases spores.

Ferns Key features? Alternation of generations? Differences from mosses?

Vascular, rhizomes, fronds with sori (sporangia), independent sporophyte.

Sporophyte dominant; gametophyte (prothallus) small, independent, water needed for fertilization.

Vascular tissue, sporophyte independent, larger size, better water/nutrient transport.

Seed bearing plants main groups? Characteristics?

Gymnosperms and angiosperms.

Embryo, nutritive tissue, protective coat; enables dormancy and dispersal via wind, water, animals.

Gymnosperms Characteristics? Main groups?

Vascular, seeds “naked” (not enclosed in fruit), pollen, cones, sporophyte dominant.

Conifers, cycads, ginkgo, gnetophytes.

Angiosperms Characteristics? Key adaptations for success? Evolutionary trend (moss → angiosperm)?

Flowers, seeds in fruit, double fertilization, sporophyte dominant, highly reduced gametophyte.

Flowers for pollination, fruits for dispersal, diverse growth forms, vascular efficiency.

Increased sporophyte dominance, vascular tissue, seeds, flowers/fruits.

Parts of a flower (male vs. female)? Pollination cues? Fruits?

• Male: Stamen (anther + filament)

• Female: Carpel/pistil (stigma + style + ovary)

• Flower color, scent, nectar, shape → attract insects, birds, wind, or water.

• Mature ovary; protects seed, aids dispersal (wind, animals, water).

Root vs. shoot systems?

• Roots: anchor, absorb water/nutrients

• Shoots: stems, leaves, reproductive structures

Q: Monocots vs. dicots?

Feature	Monocot	Dicot

Cotyledons

1

2

Leaf veins

Parallel

Net-like

Flower parts

Multiples of 3

Multiples of 4/5

Vascular bundles

Scattered

Ringed

What is a meristem? Types?

Region of undifferentiated cells;

• Apical meristem: tips of roots/shoots → primary growth

• Lateral meristem: girth/secondary growth

Specialized transport tissues?

• Xylem: water/mineral transport

• Phloem: sugar transport

How does transport work?

• Xylem: transpiration pull, cohesion-tension

• Phloem: pressure-flow, source → sink

Stomata Function? Soil function? nutrition?

Pores for gas exchange and transpiration.

Anchors plant, supplies water and nutrients.

Carnivorous plants, mycorrhizal associations, nitrogen-fixing plants.

How does angiosperm growth occur?

Meristematic activity produces new cells → differentiation → primary/secondary growth; growth regulated by hormones and environmental cues.