Plant Evolution and Classification

Adapting to Land More exposure to sunlight Increased CO 2 levels Greater supply of inorganic nutrients Susceptible to drying out cuticle (waxy coating to prevent water loss) with stomata (for gas exchange)

Reproduction Developed structure to protect reproductive cells from drying out Spore - haploid reproductive cell surrounded by a hard outer wall Seed - embryo surrounded by a protective coat

Absorbing and Transporting Nutrients Some 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 plants Have 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 groups Seedless plants - ferns and fern-like plants Seed plants - plants that produce seeds

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

Alternating Life Cycles All plants have life cycles consisting of two phases, which are named for the type of reproductive cells they produce Alternation of generations Sporophyte (2n) - produces spores Gametophyte (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.