plant phylogeny

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Plant Phylogeny Study Guide

I. Introduction to Plant Evolution

Kingdom Plantae: Includes all land plants and green algae.

Streptophyta vs. Viridiplantae:

Streptophyta: Land plants + some green algae (closer relatives to land plants).

Viridiplantae: All green algae + land plants.

Plants evolved from charophyte algae, adapting to land by developing cuticles, stomata, vascular tissue, seeds, and flowers over time.

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II. Major Plant Groups

1. Non-Vascular Plants (Bryophytes) – Earliest Land Plants

Phylum Bryophyta (Mosses)

Phylum Hepatophyta (Liverworts)

Phylum Anthocerophyta (Hornworts)

Key Characteristics:

✅ Lack xylem & phloem (no vascular tissue).

✅ Small in size, rely on diffusion for water transport.

✅ Dominant gametophyte stage (haploid, 1N); sporophyte (diploid, 2N) is dependent.

✅ Reproduce via spores; require water for sperm movement.

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2. Seedless Vascular Plants (Early Tracheophytes)

Phylum Lycophyta (Club Mosses, Spike Mosses, Quillworts)

Phylum Pteridophyta (Ferns, Horsetails, Whisk Ferns)

Key Characteristics:

✅ Have vascular tissue (xylem & phloem) → allows larger size.

✅ Dominant sporophyte stage (diploid, 2N).

✅ Reproduce via spores, not seeds.

✅ Require water for reproduction (flagellated sperm).

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3. Seed Plants (Spermatophytes) – Advanced Tracheophytes

A. Gymnosperms ("Naked Seed" Plants – No Fruit)

Phylum Cycadophyta (Cycads)

Phylum Ginkgophyta (Ginkgo biloba – only species left!)

Phylum Coniferophyta (Conifers: Pines, Firs, Cedars, etc.)

Phylum Gnetophyta (Gnetophytes: Ephedra, Welwitschia, Gnetum)

Key Characteristics:

✅ Dominant sporophyte stage (diploid, 2N).

✅ Have vascular tissue (xylem & phloem).

✅ Reproduce via seeds, not spores.

✅ Seeds develop in cones; no flowers or fruit.

✅ Mainly wind-pollinated.

B. Angiosperms ("Enclosed Seed" – Flowering Plants)

Phylum Anthophyta (Most diverse and dominant plant group today).

Key Characteristics:

✅ Have vascular tissue.

✅ Dominant sporophyte stage (diploid, 2N).

✅ Reproduce via seeds enclosed in fruit.

✅ Flowers attract pollinators (birds, insects, bats).

✅ Divided into:

Monocots (one cotyledon, parallel veins, floral parts in 3s – e.g., grasses, lilies).

Dicots (Eudicots) (two cotyledons, net-like veins, floral parts in 4s or 5s – e.g., roses, oak trees).

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III. Key Evolutionary Adaptations in Plants

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IV. Summary of Plant Phylogeny

1. First land plants: Non-vascular (mosses, liverworts, hornworts).

2. Vascular plants evolve: Seedless tracheophytes (ferns, club mosses).

3. Gymnosperms: First seed plants (conifers, cycads, ginkgo).

4. Angiosperms: Most advanced, dominate ecosystems today (flowering plants).

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