3 Objectives Explain what a plant is Describe what plants need to surviveDescribe how plants first evolved
4 What Is a Plant? Plants are members of the kingdom Plantae Plants are multicellular eukaryotes that have cell walls made of cellulose. They develop from multicellular embryos and carry out photosynthesis using the green pigments chlorophyll a and b
5 The Plant Life CyclePlants have life cycles that are characterized by alternation of generationsthe two generations are the haploid (N) gametophyte, or gamete-producing plant, and the diploid (2N) sporophyte, or spore-producing plant.
26 During at least one stage of their life cycle, bryophytes produce sperm that must swim through water to reach eggs of other individuals.Therefore, they must live in places where there is rainfall or dew for at least part of the year
27 Asexual Reproductive Part Sexual Reproductive/ PhotosyntheticPart
47 Objectives Describe the reproductive adaptations of seed plants Describe the evolution of seed plantsIdentify the four groups of gymnosperms
48 Over millions of years, plants with a single trait—the ability to form seeds—became the most dominant group of photosynthetic organisms on land.Seed plants are divided into two groups:
49 Gymnosperms Cone plants Bear their seeds directly on the surfaces of conesEx.) conifers, pines, spruces, cycads, ancient ginkgoes and gnetophytes
50 Angiosperms Flowering plants Bear their seeds within a layer of tissue that protects the seedEx.) grasses, flowering trees shrubs, wild flowers
51 Reproduction Free From Water Unlike mosses and ferns, however, seed plants do not require water for fertilization of gametes.Q: Why was this an advantage?A: They could live further away from waterAdaptations that allow seed plants to reproduce without water include flowers or cones, the transfer of sperm by pollination, and the protection of embryos in seeds.
66 Evolution of Seed Plants Over a period of millions of years, continents became much drier, making it harder for seedless plants to survive and reproduce.For that reason, many moss and fern species became extinct. They were replaced by seed plants with adaptations that equipped them to deal with drier conditions.
67 Gymnosperms—Cone Bearers The most ancient surviving seed plants are the gymnosperms. Gymnosperms include:
87 AnnualsAngiosperms that complete a life cycle within one growing season
88 Biennials Angiosperms that complete their life cycle in two years In the first year, biennials germinate and grow roots, stems, leavesDuring their second year, biennials grow new stems and leaves and then produce flowers and seeds
89 PerennialsFlowering plants that live for more than two years