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Chapter 24 - Evolution and Diversity of Plants . Domain – Eukarya Kingdom - Plantae. Plant Kingdom. Plants are multicellular, Primarily terrestrial eukaryotes Autotrophic by photosynthesis
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Chapter 24 - Evolution and Diversity of Plants Domain – Eukarya Kingdom - Plantae
Plant Kingdom • Plants are multicellular, • Primarily terrestrial eukaryotes • Autotrophic by photosynthesis • Approximately 265,000 different types of plants exist today. Plants began the transition to land about 425 million years ago. • Plants play a critical role as producers in the world's food webs; using photosynthesis to produce organic biomass and releasing oxygen as an end-product.
Plant Kingdom • Terrestrial plants carry on gas exchange through pores (stomata) on the surface of leaves. • Oxygen and water vapor leave thru stomata, and carbon dioxide enters through the stomata. (note: stoma (singular)) • The leaves are covered with a waxy cuticle to prevent desiccation.
Plant Kingdom • Plant chloroplasts contain chlorophyll a, chlorophyll b, and a variety of yellow and orange carotenoids. • Plant cell walls are composed of cellulose. • Plants store carbohydrate as starch.
Plant reproduction • Nearly all plants reproduce sexually, though many also are capable of asexual modes of reproduction. • Alternation of generations occurs in the life cycle of plants, with a haploid, gamete-producing gametophyte stage alternating with a diploid, spore-producing sporophyte stage. • Bryophytes (true mosses) have a large, obvious gametophyte stage, • but in other plants the sporophyte stage is larger and the gametophyte stage has been reduced.
Plant Evolution - marked by four major adaptations: • (1) about 400 million years ago - the feature of a protected embryo; also spore production as a means of reproduction; • (2) the evolution of vascular tissue; • (3) the origin of seed producing plants about 360 million years ago; and • (4) the evolution of flowering plants about 130 million years ago.
Plants - Basic Vocabulary • vascular tissue - plant tissues that consist of cells that transport water and nutrients throughout the plant body. The two major types are xylem and phloem. • xylem - vascular tissue that carries water and minerals from the roots to the rest of the plant. • phloem - vascular tissue that carries sugar and organic nutrients (sap) throughout the plant. • gametangium - the gametophyte stage of mosses consisting of a male antheridium (sperm) and a female archegonium (egg) • gametophyte - multicellular, haploid stage of the life cycle that produces haploid gametes that fuse to form the diploid sporophyte • sporophyte - multicellular, diploid stage of the life cycle that through meiosis produces haploid gametes that become the gametophyte
Vascular tissue • xylem - vascular tissue that carries water and minerals from the roots to the rest of the plant. • phloem - vascular tissue that carries sugar and organic nutrients (sap) throughout the plant.
Plant Kingdom: The Classification of Plants (Four major groups exist):
Nonvascular Plants Mosses and Relatives - – bryophytes No true roots (rhizoids), stems, or leaves Gametophyte stage dominant, no vascular tissue, spores as a means of reproduction • Phylum Bryophyta - (true mosses) (10,000 species) • Phylum Hepatophyta (liverworts) (6500 species) • Phylum Anthocerophyta (hornworts) (100 species)
1. Bryophytes and their relatives • Phylum Bryophyta (mosses) - lack vascular tissue but have certain adaptations that made a terrestrial existence possible including having a waxy cuticle, and female gametes that develop and are fertilized within a protective gametangia. The male gametangium is the antheridium and the female gametangium is the archegonium. The egg is fertilized within the archegonium and the sporophyte stage grows out of the body of the gametophyte stage. • Because mosses lack vascular tissue they must absorb water by diffusion and capillary action which limits them to shady, moist habitats and a relatively small body size. • 1. antheridium • 2. archegonium • 3. sporophyte • 4. gametophyte
Bryophytes and their relatives, contd. • * Phylum Hepatophyta (liverworts) - diminutive plants with lobed bodies ("lobed herbs"), liverworts have a life cycle similar to mosses. They can also reproduce asexually by gemmae (groups of cells) which are dispersed when raindrops fall into their protective cups. • * Phylum Antherocerophyta (hornworts) - resemble liverworts but have horn-shaped sporophyte stage
Vascular Plants – Seedless • sporophyte stage dominant; small gametophyte present; vascular tissue present; spores as a means of reproduction • Phylum Psilophyta (whiskferns) (13 species) • Phylum Lycophyta (club mosses) (1,000 species) • Phylum Sphenophyta (horsetails) (15 species) • Phylum Pterophyta (ferns) (12,000 species)
2. Ferns and their relatives: • Phylum Psilophyta (whiskferns) - Psilotum, lacks true roots and leaves, have rhizomes which are underground stems covered with rhizoid hairs. The body plan of the whiskferns probably is similar to the earliest vascular plants.
Ferns and their relatives, contd. • Phylum Lycophyta (lycopods, club mosses, ground pines) - Lycopodium and Sellaginella, the sporangia of Lycopodium are borne on sporophylls, leaves specialized for reproduction. Gametophyte stage is inconspicuous and develops underground. Heterosporous, the megaspores develop into female gametophytes bearing archegonia and the microspores develop into male gametophytes bearing antheridia.
Ferns and their relatives, contd. • Phylum Sphenophyta (horsetails): Equisetum, conspicuous sporophyte, silica in the epidermal cells give these plants a glassy texture. Equisetum was also formerly called "scouring rush" because the glassy texture made them useful for scrubbing pots and pans. Gametophyte stage is small but photosynthetic and free-living.
Ferns and their relatives, contd. • Phylum Pterophyta (ferns): large sporophyte stage, ferns are widely distributed in the tropics and relatively common in temperate regions. Some of the leaves (fronds) of ferns are specialized sporophylls with clusters of spores called sori on the underside of the frond. The airborne spores are catapulted from the sorus. • frond – leaves of ferns • sorus – on underside of leaves/ hold spores • rhizome – branching underground stem w/ rootlike hairs
Vascular Plants - Seed Producers • – sporophyte stage dominant; vascular tissue, seeds as a means of reproduction • 3. Gymnosperms • Division Coniferophyta (conifers) (550 species) • Division Cycadophyta (cycads) (100 species) • Division Ginkgophyta (ginkgo) (1 species) • Division Gnetophyta (gnetae) (70 species)
3. Gymnosperms and their relatives: • Phylum Coniferophyta (pines, spruce, firs, larches, cedars, cypresses, redwoods): • produce a cone which supports and protects the seed. • Most conifers are evergreen and their needle-shaped leaves adapt them to dry habitats. • Important source of most of our lumber and pulp paper. • The bristlecone pine is one of the oldest organisms (4600 years old), while the redwoods are the largest organisms alive (the "General Sherman" tree has a trunk circumference of 26 m.
Phylum Coniferophyta, contd. • In the life cycle of the pine, the sporophyte generation would be represented by the pine tree itself, while the gametophyte generation has been reduced to female (ovulate) and male (pistillate) cones. These plants produce true seeds which consist of a developing embryo, a nutrient supply, and a protective seed coat. Conifers are monoecious since trees produce both pollen and seed cones.
Phylum Coniferophyta life cycle of the pine
4. Angiosperms • sporophyte dominant, vasculat plants, seeds, fruits and flowers • Phylum Anthophyta (flowering plants) (240,000 species) • The angiosperms are extremely important providing all of our fruits and vegetables, and providing medicines, fiber, perfumes, and decorations.
4. Angiosperms and their relatives • Angiosperms (flowering plants) - the dominant form of plant life on earth at the present time; 240,000 species. • monocots Monocotyledons • dicots Dicotyledons
monocots Monocotyledons • Consists of monocots (lilies, orchids, yuccas, palms, pineapples, grasses, and cereal grains) which have flower parts in threes or multiples of three (3); and • one cotyledon (seed leaf) in their seeds
dicots Dicotyledons • dicots (oak, hickory, asters, roses, maples, strawberries, cactuses, beans) which have flower parts in four or fives, or multiples of four (4) or five (5), and • two cotyledons (seed leaf) in their seeds
Angiosperm characteristics • Have well-developed and efficient vascular tissue including xylem (tracheids and vessels) and phloem (sieve tubes and companion cells). • Four major flower parts may be present: the calyx consisting of sepals that protect the flower; the corolla consisting of petals to attract pollinators; the stamens (male pollen-producing structure consisting of and anther and filament); and the carpel (pistil) (female egg-producing structures consisting of the stigma, style, and ovary).
General Flower Structure - Angiosperms male pollen-producing structure pistil female egg-producing structures
Angiosperm Vocabulary • ovule - holds the megasporangium and female gametophyte which produces an egg; the ovule later becomes the seed • ovary - the enlarged base of the pistil, which forms the fruit • fruit - a ripened, thickened ovary of a flower, which protects the seeds and assists their dispersal • pollination - transfer of pollen from microsporangium to female gametophyte • fertilization - fusion of sperm nucleus with egg nucleus
Angiosperm Flowering plant life cycle
Four Trends in Angiosperm Evolution • 1. Number of floral parts has been reduced • 2. Floral parts have become fused • 3. Symmetry has changed from radial to bilateral • 4. Ovary has dropped to a position below the petals and sepals (inferior) where the flowers are better protected • * Flowering plants and land animals have co-evolved to develop many different types of relationships related to pollination and reproduction.
