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Chapter 30 Plant Diversity II: The Evolution of Seed Plants PowerPoint Lectures for Biology, Seventh Edition Neil Campbell and Jane Reece Lectures by Chris Romero Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Overview: Feeding the World • Seeds changed the course of plant evolution, enabling their bearers to become the dominant producers in most terrestrial ecosystems Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 30.1: The reduced gametophytes of seed plants are protected in ovules and pollen grains • In addition to seeds, the following are common to all seed plants: – Reduced gametophytes – Heterospory – Ovules – Pollen Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Advantages of Reduced Gametophytes • The gametophytes of seed plants develop within the walls of spores retained within tissues of the parent sporophyte Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Heterospory: The Rule Among Seed Plants • Seed plants evolved from plants with megasporangia, which produce megaspores that give rise to female gametophytes • Seed plants evolved from plants with microsporangia, which produce microspores that give rise to male gametophytes Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Ovules and Production of Eggs • An ovule consists of a megasporangium, megaspore, and one or more protective integuments • Gymnosperm megaspores have one integument • Angiosperm megaspores usually have two integuments Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Pollen and Production of Sperm • Microspores develop into pollen grains, which contain the male gametophytes • Pollination is the transfer of pollen to the part of a seed plant containing the ovules • Pollen can be dispersed by air or animals, eliminating the water requirement for fertilization • If a pollen grain germinates, it gives rise to a pollen tube that discharges two sperm into the female gametophyte within the ovule Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Evolutionary Advantage of Seeds • A seed develops from the whole ovule • A seed is a sporophyte embryo, along with its food supply, packaged in a protective coat Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 30.2: Gymnosperms bear “naked” seeds, typically on cones • The gymnosperms include four phyla: – Cycadophyta (cycads) – Gingkophyta (one living species: Ginkgo biloba) – Gnetophyta (three genera: Gnetum, Ephedra, Welwitschia) – Coniferophyta (conifers, such as pine, fir, and redwood) Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings LE 304aa Cycas revoluta LE 304ab LE 304ac LE 304ad Gnetum. This genus includes about 35 species of tropical trees, shrubs, and vines, mainly native to Africa and Asia. Their leaves look similar to those of flowering plants, and their seeds look somewhat like fruits. LE 304ae Ephedra. This genus includes about 40 species that inhabit arid regions throughout the world. Known in North America as “Mormon tea,” these desert shrubs produce the compound ephedrine, commonly used as a decongestant. LE 304af Welwitschia. This genus consists of one species Welwitschia mirabilis, a plant that lives only in the deserts of southwestern Africa. Its strap like leaves are among the largest known. LE 304ag Ovulate cones LE 304ba Douglas fir. “Doug fir” (Pseudotsuga menziesii) provides more timber than any other North American tree species. Some uses include house framing, plywood, pulpwood for paper, railroad ties, and boxes and crates. LE 304bb Pacific yew. The bark of Pacific yew (Taxa brevifolia) is a source of taxol, a compound used to treat women with ovarian cancer. The leaves of a European yew species produce a similar compound, which can be harvested without destroying the plants. Pharmaceutical companies are now refining techniques for synthesizing drugs with taxol-like properties. LE 304bc Bristlecone pine. This species (Pinus longaeva), which is found in the White Mountains of California, includes some of the oldest living organisms, reaching ages of more than 4,600 years. One tree (not shown here) is called Methuselah because it may be the world’s oldest living tree. In order to protect the tree, scientists keep its location a secret. LE 304bd Sequoia. This giant sequoia (Sequoiadendron giganteum), in California’s Sequoia National Park weighs about 2,500 metric tons, equivalent to about 24 blue whales (the largest animals), or 40,000 people. Giant sequoias are the largest living organisms and also some of the most ancient, with some estimated to be between 1,800 and 2,700 years old. Their cousins, the coast redwoods (Sequoia sempervirens), grow to heights of more than 110 meters (taller than the Statue of Liberty) and are found only in a narrow coastal strip of northern California. LE 304be Common juniper. The “berries” of the common juniper (Juniperus communis), are actually ovuleproducing cones consisting of fleshy sporophylls. LE 304bf Wollemia pine. Survivors of a confer group once known only from fossils, living Wollemia pines (Wollemia nobilis), were discovered in 1994 in a national park only 150 kilometers from Sydney, Australia. The species consists of just 40 known individuals two small groves. The inset photo compares the leaves of this “living fossil” with actual fossils. Concept 30.3: The reproductive adaptations of angiosperms include flowers and fruits • Angiosperms are flowering plants • These seed plants have reproductive structures called flowers and fruits • They are the most widespread and diverse of all plants Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Characteristics of Angiosperms • All angiosperms are classified in a single phylum, Anthophyta • The name comes from the Greek anthos, flower Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Flower s • The flower is an angiosperm structure specialized for sexual reproduction Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings LE 3011 Carpel Stamen 5 cm Archaefructus sinensis, a 125-million-year-old fossil Artist’s reconstruction of Archaefructus sinensis LE 3012ba MONOCOTS EUDICOTS Orchid Monocot (Lemboglossum Characteristics rossii) Eudicot Characteristics Embryos One cotyledon Two cotyledons California poppy (Eschscholzia california) Evolutionary Links Between Angiosperms and Animals • Pollination of flowers by animals and transport of seeds by animals are two important relationships in terrestrial ecosystems Video: Bee Pollinating Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Video: Bat Pollinating LE 3013 A flower pollinated by honeybees. A flower pollinated by hummingbirds. A flower pollinated by nocturnal animals.