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Chapter 21: Part 1 The Diversity of Plants Adapted from Lecture Outlines by Gregory Ahearn, University of North Florida Copyright © 2011 Pearson Education Inc. How do plants affect the ecosystem? Photosynthesize – Make sun’s energy available to consumers – Produce oxygen Plants build soil – Dead plant material is decomposed, making the soil more fertile – Roots hold the soil together Plants help keep ecosystems moist – Store water – Preven runnoff and flooding Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. How do plants affect humans? Plants provide humans with necessities and luxuries – Plants provide shelter, fuel, and medicine – Plants provide pleasure through flowers, gardens, lawns, and parks and through coffee, tea, and wine Cocoa beans Biology: Life on Earth, 9e Sassafras Quinine Copyright © 2011 Pearson Education Inc. 21.3 What Is the Evolutionary Origin of Plants? Ancestors were photosynthetic protists (algae) Both: – have similar DNA – use the same type of chlorophyll – store food as starch and have cell walls made of cellulose Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. Green alga Chara, a Stonewort plants’ closest living relatives Fig. 21-3 Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. 21.3 What Is the Evolutionary Origin of Plants? The ancestors of plants were aquatic – this has its advantages! – Bathed in a nutrient-rich solution – Supported by buoyancy – Gametes and zygotes carried by water currents Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. 21.4 How Have Plants Adapted to Life on Land? The invasion of the land brought many advantages to plants – Direct access to sunlight – Access to nutrient-rich soil But… it also imposed some challenges – No support from water – Drying out an issue – No wet medium to transport gametes Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. 21.4 How Have Plants Adapted to Life on Land? Adaptations helped solve these problems – Roots – Anchor the plant – Absorb nutrients from the soil – Waxy cuticle – Limits the evaporation of water – Stomata – Pores in the leaves and stems that open and allow gas exchange, but close when water is scarce Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. 21.4 How Have Plants Adapted to Life on Land? Adaptations helped solve these problems (cont.) – Vascular tissues –Conducting cells that transport materials throughout plant –Xylem – water and minerals –Phloem – sugar and nutrients – Lignin –Rigid polymer in cell walls that supports the plant body Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. 21.4 How Have Plants Adapted to Life on Land? Some plants have additional adaptations – Seeds – Protect embryo – Provide food for embryo – Pollen – Contains male gamete – Dispersed by wind and the bodies of insects – Flowers – Attract pollinators – Fruits – Attract animal foragers Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. Chapter 21: Part 2 The Diversity of Plants Adapted from Lecture Outlines by Gregory Ahearn, University of North Florida Copyright © 2011 Pearson Education Inc. 21.5 What Are the Major Groups of Plants? Two major groups of land plants arose from ancient green algal ancestors – The nonvascular plants (called bryophytes) straddle the boundary between aquatic and terrestrial life – The vascular plants (called tracheophytes) have been able to colonize dry habitats Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. The Evolutionary Tree of Some Major Plant Groups Nonvascular plants Vascular plants seed plants Liverworts Mosses Ferns Gymnosperms Angiosperms Flowers and fruits Seeds and pollen True vascular tissue and lignin Ancestral green alga Biology: Life on Earth, 9e Fig. 21-4 Copyright © 2011 Pearson Education Inc. 21.5 What Are the Major Groups of Plants? Nonvascular must live near water – – – – They lack true roots, stems, or leaves Cell walls aren’t as stuff – limits size Flagellated sperm must swim to egg Nonvascular plants include the hornworts, liverworts, and mosses Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. 21.5 What Are the Major Groups of Plants? Vascular plants have conducting cells that also provide support – Have xylem and phloem – Vascular tissues contain lignin in cell walls – Vascular plants can be divided into two groups: the seedless vascular plants and the seed plants Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. 21.5 What Are the Major Groups of Plants? The seedless vascular plants include the club mosses, horsetails, and ferns – These plants have swimming sperm and require water for reproduction – They do not produce seeds, but propagate by spores Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. 21.5 What Are the Major Groups of Plants? The seed plants are aided by two important adaptations: pollen and seeds – Pollen grains carry sperm-producing cells –They are dispersed by wind or pollinators –They eliminate the need for sperm to swim to the egg – Seeds have three components: an embryonic plant, a food supply for the embryo, and a protective outer coat Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. Seeds embryo stored food seed coat Pine seed (gymnosperm) (a) Seeds Biology: Life on Earth, 9e Bean seed (angiosperm) Fig. 21-9 Copyright © 2011 Pearson Education Inc. 21.5 What Are the Major Groups of Plants? Gymnosperms are nonflowering seed plants – Gymnosperms evolved earlier than the flowering plants – They were the first fully terrestrial plants to evolve – Today, four groups of gymnosperms survive: ginkgos, cycads, gnetophytes, and conifers Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. 21.5 What Are the Major Groups of Plants? Angiosperms are flowering seed plants – Angiosperms produce flowers and fruits – They are the most diverse and widespread of all plants, with more than 230,000 species – They have a broad range in size – Duckweed (3 mm in diameter) – Eucalyptus tree (100 meters in height) Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. 21.5 What Are the Major Groups of Plants? Angiosperms also have broad leaves – Collect more sunlight for photosynthesis – Some drop their leaves to conserve water – BUT… tender leaves are more appealing to herbivores than the tough, waxy needles of conifers – We exploit some of these defenses – Medicines (aspirin, codeine) – Stimulants (nicotine, caffeine) – Spicy flavors (mustard, peppermint) Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. Author Animation: Adaptations in Plant Evolution Nonvascular plants Vascular plants seed plants Liverworts Mosses Ferns Gymnosperms Angiosperms Flowers and fruits Seeds and pollen True vascular tissue and lignin Ancestral green alga Biology: Life on Earth, 9e Fig. 21-4 Copyright © 2011 Pearson Education Inc. Angiosperms can be divided into two groups Monocots – Lilies, daffodils, tulips, palms, corn, grasses – Seeds produce two cotyledons (part that nourishes embryo) Dicots – All “broad-leafed” plants – tomatoes, daisies, cherry trees, maple trees – Seeds produce only one cotyledon Some differences in root and stem structure Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc.