The Diversity of Plants Copyright © 2005 Pearson Prentice Hall, Inc.

Plant Evolution Green Algae Gave Rise to Plants Bryophytes Tracheophytes seed plants Liverworts Mosses Ferns Gymnosperms Angiosperms Figure: 21-1 Title: Evolutionary tree of some major plant groups Caption: Plant Evolution (F 21.1 p. 406) Green Algae Gave Rise to Plants Plant Ancestors Lived in Fresh Water Ancestral green alga Copyright © 2005 Pearson Prentice Hall, Inc. Copyright © 2005 Pearson Prentice Hall, Inc.

Key Features of Plants Alternating Multicellular Haploid & Diploid Generations Alternation of generations in plants (F21.2 p. 407) More Recently Evolved Plants Have Smaller Gametophytes Copyright © 2005 Pearson Prentice Hall, Inc.

MITOSIS Haploid FERTILIZATION MEIOSIS Diploid gametophyte (n) sperm egg n FERTILIZATION 2n zygote Haploid MEIOSIS 2n spore mother cell n spores Figure: 21-2 Title: Alternation of generations in plants Caption: As shown in this generalized depiction of a plant life cycle, a diploid sporophyte generation produces haploid spores through meiosis. The spores develop into a haploid gametophyte generation that produces haploid gametes by mitosis. The fusion of these gametes results in a diploid zygote that develops into the sporophyte plant. Diploid 2n embryo sporophyte (2n) haploid Copyright © 2005 Pearson Prentice Hall, Inc. diploid

Key Features of Plants Multicellular, Dependent Embryos Plants Are Adapted to Life on Land Bodies Resist Gravity & Drying Embryos Are Protected Sex Cells May Disperse Without Water Copyright © 2005 Pearson Prentice Hall, Inc.

Features of the Major Plant Groups T21.1 (p. 408) Table: 21-T1 Title: Features of the Major Plant Groups Copyright © 2005 Pearson Prentice Hall, Inc.

Major Groups of Plants Bryophytes Lack Conducting Structures Bryophytes (F 21.3 p. 409) Copyright © 2005 Pearson Prentice Hall, Inc.

Major Groups of Plants: Bryophytes Life cycle of a moss (F21.4 p. 410) emerging sporophyte capsules capsules MEIOSIS Life cycle of a moss (F21.4 p. 410) Major Groups of Plants: Bryophytes Protected Reproductive Structures emerging gametophyte leafy gametophyte FERTILIZATION Figure: 21-4 Title: Life cycle of a moss Caption: The leafy green gametophyte (lower right) is the haploid generation that produces sperm and eggs. The sperm must swim through a film of water to the egg. The zygote develops into a stalked, diploid sporophyte that emerges from the gametophyte plant. The sporophyte is topped by a brown capsule in which haploid spores are produced by meiosis. These are dispersed and germinate, producing another green gametophyte generation. (Inset) Moss plants. The short, leafy green plants are haploid gametophytes; the reddish brown stalks are diploid sporophytes. haploid diploid Copyright © 2005 Pearson Prentice Hall, Inc.

capsules MEIOSIS emerging sporophyte capsules FERTILIZATION emerging Figure: 21-4 Title: Life cycle of a moss Caption: The leafy green gametophyte (lower right) is the haploid generation that produces sperm and eggs. The sperm must swim through a film of water to the egg. The zygote develops into a stalked, diploid sporophyte that emerges from the gametophyte plant. The sporophyte is topped by a brown capsule in which haploid spores are produced by meiosis. These are dispersed and germinate, producing another green gametophyte generation. (Inset) Moss plants. The short, leafy green plants are haploid gametophytes; the reddish brown stalks are diploid sporophytes. emerging gametophyte leafy gametophyte haploid diploid Copyright © 2005 Pearson Prentice Hall, Inc.

Major Groups of Plants: Vascular Plants Conducting Vessels That Also Provide Support The Seedless Vascular Plants Club Mosses, Horsetails, and Ferns Club Mosses and Horsetails Are Small and Inconspicuous Some seedless vascular plants (F21.5 p. 411) Copyright © 2005 Pearson Prentice Hall, Inc.

Copyright © 2005 Pearson Prentice Hall, Inc. Figure: 21-5 Title: Some seedless vascular plants Caption: Seedless vascular plants are found in moist woodland habitats. (a) The club mosses (sometimes called ground pines) grow in temperate forests. This specimen is releasing spores. (b) The giant horsetail extends long, narrow branches in a series of rosettes. Its leaves are insignificant scales. At right is a cone-shaped spore-forming structure. (c) The leaves of this deer fern are emerging from coiled fiddleheads. Question In each of these photos, is the pictured structure a sporophyte or a gametophyte? Copyright © 2005 Pearson Prentice Hall, Inc.

Ferns: Broad-Leaved More Diverse Life cycle of a fern (F21.6 p. 412) sporophyte FERTILIZATION masses of sporangia sporangium MEIOSIS stem root leaf Ferns: Broad-Leaved More Diverse Life cycle of a fern (F21.6 p. 412) gametophyte Figure: 21-6 Title: Life cycle of a fern Caption: The dominant plant body (upper left) is the diploid sporophyte. Haploid spores, formed in sporangia located on the underside of certain leaves, are dispersed by the wind to germinate on the moist forest floor into inconspicuous haploid gametophyte plants. On the lower surface of these small, sheetlike gametophytes, male antheridia and female archegonia produce sperm and eggs. The sperm must swim to the egg, which remains in the archegonium. The zygote develops into the large sporophyte plant. (Inset) Underside of a fern leaf, showing clusters of sporangia. haploid diploid Copyright © 2005 Pearson Prentice Hall, Inc.

Copyright © 2005 Pearson Prentice Hall, Inc. Figure: 21-6 Title: Life cycle of a fern Caption: (Inset) Underside of a fern leaf, showing clusters of sporangia. Copyright © 2005 Pearson Prentice Hall, Inc.

Major Groups of Plants Seed Plants Dominate the Land Aided by Two Important Adaptations: Pollen and Seeds Seeds (F21.7 p. 413) Copyright © 2005 Pearson Prentice Hall, Inc.

embryo stored food seed coat Pine seed Bean seed (gymnosperm) (angiosperm) Figure: 21-7 Title: Seeds Caption: Seeds from (a) a gymnosperm and (b) an angiosperm. Both consist of an embryonic plant and stored food confined within a seed coat. Seeds exhibit diverse adaptations for dispersal, including (c) the dandelion's tiny, tufted seeds that float in the air and (d) the massive, armored seeds (protected inside the fruit) of the coconut palm, which can survive prolonged immersion in seawater as they traverse oceans. Question Can you think of some adaptations that help protect seeds from destruction by animal consumption? Copyright © 2005 Pearson Prentice Hall, Inc.

Major Groups of Plants Gymnosperms: Nonflowering Seed Plants Conifer Seeds Develop in Cones Life cycle of the pine (p. F21.8 414) Copyright © 2005 Pearson Prentice Hall, Inc.

scale of female cone male cone male cone female spore-forming cell MEIOSIS egg cell gametophyte ovule mature sporophyte seedlings Figure: 21-8 Title: Life cycle of the pine Caption: The pine tree is the sporophyte generation (upper left) and bears both male and female cones. Haploid female gametophytes develop within the scales of female cones and produce egg cells. Male cones produce pollen, the male gametophytes. A pollen grain, dispersed by the wind, may land on the scale of a female cone. It then grows a pollen tube that penetrates the female gametophyte and conducts sperm to the egg. The fertilized egg develops into an embryonic plant enclosed in a seed. The seed is eventually released from the cone, germinates, and grows into a sporophyte tree. embryo seed FERTILIZATION pollen tube haploid diploid Copyright © 2005 Pearson Prentice Hall, Inc.

Copyright © 2005 Pearson Prentice Hall, Inc. Figure: 21-8 inset left Title: Life cycle of the pine inset left Caption: The pine tree is the sporophyte generation (upper left) and bears both male and female cones. Haploid female gametophytes develop within the scales of female cones and produce egg cells. Male cones produce pollen, the male gametophytes. A pollen grain, dispersed by the wind, may land on the scale of a female cone. It then grows a pollen tube that penetrates the female gametophyte and conducts sperm to the egg. The fertilized egg develops into an embryonic plant enclosed in a seed. The seed is eventually released from the cone, germinates, and grows into a sporophyte tree. Copyright © 2005 Pearson Prentice Hall, Inc.

Copyright © 2005 Pearson Prentice Hall, Inc. Figure: 21-8 inset right Title: Life cycle of the pine inset right Caption: The pine tree is the sporophyte generation (upper left) and bears both male and female cones. Haploid female gametophytes develop within the scales of female cones and produce egg cells. Male cones produce pollen, the male gametophytes. A pollen grain, dispersed by the wind, may land on the scale of a female cone. It then grows a pollen tube that penetrates the female gametophyte and conducts sperm to the egg. The fertilized egg develops into an embryonic plant enclosed in a seed. The seed is eventually released from the cone, germinates, and grows into a sporophyte tree. Copyright © 2005 Pearson Prentice Hall, Inc.

Major Groups of Plants Ginkgos and Cycads Less Abundant Two uncommon gymnosperms (F21.9 p. 415) Copyright © 2005 Pearson Prentice Hall, Inc.

Copyright © 2005 Pearson Prentice Hall, Inc. Figure: 21-9 Title: Two uncommon gymnosperms Caption: (a) This ginkgo, or maidenhair tree, is female and bears fleshy seeds the size of large cherries. (b) A cycad. Common in the age of dinosaurs, these are now limited to about 160 species. Like ginkgos, cycads have separate sexes. Copyright © 2005 Pearson Prentice Hall, Inc.

Major Groups of Plants Angiosperms: Flowering Seed Plants Angiosperms (F21.10 p. 417) Copyright © 2005 Pearson Prentice Hall, Inc.

Copyright © 2005 Pearson Prentice Hall, Inc. Figure: 21-10 Title: Angiosperms Caption: (a) The smallest angiosperm is the duckweed, found floating on ponds. These specimens are about 1/8 inch (3 millimeters) in diameter. (b) The largest angiosperms are eucalyptus trees, which can reach 325 feet (100 meters) in height. Both (c) grasses and many trees, such as (d) this birch, in which flowers are shown as buds (green) and blossoms (brown), have inconspicuous flowers and rely on wind for pollination. More conspicuous flowers, such as those on (e) this butterfly weed and on a eucalyptus tree (b, inset), entice insects and other animals that carry pollen between individual plants. Exercise List the advantages and disadvantages of wind pollination. Do the same for pollination by animals. Why do both types of pollination persist among the angiosperms? Copyright © 2005 Pearson Prentice Hall, Inc.

Major Groups of Plants Flowers Attract Pollinators Life cycle of a flowering plant (F 21.11 p. 418) Copyright © 2005 Pearson Prentice Hall, Inc.

seedling flower stigma anther mature sporophyte food source embryo ovule stigma anther food source embryo seed coat spore- forming cell MEIOSIS anther contains cells that form pollen spore pollen (male gametophytes) ovule each seed developed from one ovule seed stigma pollen grain pollen tube FERTILIZATION female gametophyte sperm nuclei egg cell Figure: 21-11 Title: Life cycle of a flowering plant Caption: The dominant plant body (upper right) is the diploid sporophyte, whose flowers normally produce both male and female gametophytes. Male gametophytes (pollen grains) are produced within anthers. The female gametophyte develops from a spore within the ovule, and contains one egg cell. A pollen grain that lands on a stigma grows a pollen tube that burrows down to the ovule and into the female gametophyte. There it releases its sperm, one of which fuses with the egg to form a zygote. The ovule gives rise to the seed, which contains the developing embryo and its food source. The seed is dispersed, germinates, and develops into a mature sporophyte. haploid diploid Copyright © 2005 Pearson Prentice Hall, Inc.

Major Groups of Plants Fruits Encourage Seed Dispersal Broad Leaves Capture More Sunlight Two ways of coping with the dryness of winter (F 21.12 p. 419) Copyright © 2005 Pearson Prentice Hall, Inc.

Copyright © 2005 Pearson Prentice Hall, Inc. Figure: 21-12 Title: Two ways of coping with the dryness of winter Caption: The evergreen (a conifer) retains its needles throughout the year. The small surface area and heavy cuticle of the needles slow the loss of water through evaporation. In contrast, the aspen (an angiosperm) sheds its leaves each fall. The dying leaves turn brilliant shades of gold as pigments used to capture light energy for photosynthesis are exposed when the chlorophyll disintegrates. Copyright © 2005 Pearson Prentice Hall, Inc.

Major Groups of Plants Copyright © 2005 Pearson Prentice Hall, Inc.