19 KEY CONCEPT Plant life began in the water and became adapted to land. (Charophytes are the ancestors of plants)

19 Kingdom Plantae Characteristics of all plants Multicellular Autotrophic Eukaryotic

19 Plants faced difficulties to maintain life on land Obtaining resources- from air and soil- special organs Staying upright- support tissues-lignin-c. wall Maintaining moisture-waxy cuticle, stoma-pores on leaf Reproducing- protective jacket for gametes, eggs remain in female parent where they are fertilized

19 Important plant characteristics likely originated in charophytes. multicellular body allowing for specialization of cells and tissues cell division that allows for chemical communication between cells reproduction involving sperm swimming to egg

19 True plants evolved through natural selection. Ancestral charophytes lived in areas of shallow water. Those that could survive longer dry periods were favored. First true plants probably grew at edges of water. True plants have embryos that develop while attached to female parent.

Evidence: Charophytes are ancestors of green plants Cell walls- 20-60% cellulose Similar chloroplasts Similar mitosis and cytokinesis Similar genes and rRNA sequences

19 True plants evolved through natural selection.

Plants have adaptations that allow them to live on land. 19 Plants have adaptations that allow them to live on land. Challenges of living on land have selected for certain plant adaptations. Maintaining moisture A cuticle allows plants to retain moisture. waxy, waterproof layer holds moisture in

19 Stomata are tiny holes in the cuticle. can open and close allow air to move in and out (CO2 and O2) Closing holds in moisture

19 A vascular system allows resources to move to different parts of the plant. collection of specialized tissues brings water and mineral nutrients up from roots disperses sugars from the leaves allows plants to grow higher off the ground (lignin) sugars water and mineral nutrients xylem phloem

19 Lignin allows plants to grow upright. plant cells lignin hardens cell walls of some vascular tissues provides stiffness to stems

19 Pollen grains allow for reproduction without free-standing water. pollen grains contain a cell that divides to form sperm pollen can be carried by wind or animals to female structures

19 A seed is a storage device for a plant embryo. seed coats protect embryos from drying wind and sunlight embryo develops inside the ovary of a female plant

Alternations of Generations- Taking turns 19 Alternations of Generations- Taking turns A plant's life cycle alternates between the gametophyte and sporophyte generations. Gametophytes produce gametes Sporophytes produce spores Four major Groups of plants: bryophytes, pteridophytes, gymnosperms, and angiosperms.

Spores differ from gametes Spores can develop into a new organism with fusing or mating. Gametes must fuse- zygote Spores have tough, protective coats to resist harsh conditions Gametes are affected by harsh conditions-cold, heat, drying.

Bryophytes- mosses- oldest 4 Main plant Groups Bryophytes- mosses- oldest No seeds, no lignin-hardened vascular tissue Pteridophytes- ferns No seeds, have lignin-hardened vascular tissue Gymnosperms- cone-bearing plants First to have seeds-”naked seeds”- no chamber Specialized leaves Seeds- embryo with a food store Plants can spread via seeds without drying out. Flowering plants- angiosperms - Seeds in ovaries- protection, dispersal

19 Plants have adaptations that prevent animals from eating them. spines and thorns defensive chemicals