Plant Evolution and Classification

Adapting to Land

More exposure to sunlightIncreased CO2 levels

Greater supply of inorganic nutrients

Susceptible to drying outcuticle (waxy coating to prevent water loss) with stomata (for gas exchange)

Reproduction

Developed structure to protect reproductive cells from drying outSpore - haploid reproductive cell surrounded by a hard outer wallSeed - embryo surrounded by a protective coat

Absorbing and Transporting NutrientsSome plants have vascular tissue to transport food (phloem) and water (xylem), and help support the plant

Classifying Plants

12 phyla (formerly divisions), include more than 270,000 species.

Three phyla of nonvascular plantsHave neither true vascular tissue not true roots, stems, or leaves.

Classifying Plants Cont.Nine phyla of vascular plants (have vascular tissue and true roots, stems, and leaves)

Vascular plants can be divided into two groupsSeedless plants - ferns and fern-like plantsSeed plants - plants that produce seeds

Classifying Plants Cont.Seed plants can be divided into two groupsGymnosperms - produce seeds not enclosed in fruits (pine trees)Angiosperms - produce seeds enclosed in fruits

Alternating Life CyclesAll plants have life cycles consisting of two phases, which are named for the type of reproductive cells they produce

Alternation of generationsSporophyte (2n) - produces sporesGametophyte (1n) - produces gametes

Alternating Life Cycles Cont.In the nonvascular plant life cycle, the gametophyte is the dominant phase.

Alternating Life Cycles Cont.In the vascular plant life cycle, the sporophyte is the dominant plant.