Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings PowerPoint ® Lecture Presentations for Biology Eighth Edition Neil Campbell and Jane Reece Lectures by Chris Romero, updated by Erin Barley with contributions from Joan Sharp Chapter 29 Plant Diversity

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings You should now be able to: 1.Describe four shared characteristics and four distinct characteristics between charophytes and land plants 2.Diagram and label the life cycle of a bryophyte 3.Explain why most bryophytes grow close to the ground and are restricted to periodically moist environments 4.Describe three traits that characterize modern vascular plants and explain how these traits have contributed to success on land 5.Explain how vascular plants differ from bryophytes 6.Diagram and label the life cycle of a seedless vascular plant 7.Explain why pollen grains were an important adaptation for successful reproduction on land 8.Describe the life history of a pine; indicate which structures are part of the gametophyte generation and which are part of the sporophyte generation 9.Identify and describe the function of the following floral structures: sepals, petals, stamens, carpels, filament, anther, stigma, style, ovary, and ovule

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Seeds and pollen grains are key adaptations for life on land Seeds changed the course of plant evolution, enabling their bearers to become the dominant producers in most terrestrial ecosystems A seed consists of an embryo and nutrients surrounded by a protective coat In addition to seeds, the following are common to all seed plants – Reduced gametophytes – Heterospory – Ovules – Pollen

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Origin of land plants (about 475 mya) Origin of vascular plants (about 420 mya) Origin of extant seed plants (about 305 mya) ANCES- TRAL GREEN ALGA Liverworts Hornworts Mosses Lycophytes (club mosses, spike mosses, quillworts) Pterophytes (ferns, horsetails, whisk ferns) Gymnosperms Angiosperms Seed plants Seedless vascular plants Nonvascular plants (bryophytes) Land plants Vascular plants Millions of years ago (mya)

Fig Reduced (usually microscopic), dependent on surrounding sporophyte tissue for nutrition Reduced, independent (photosynthetic and free-living) Gametophyte Sporophyte (2n) Gametophyte (n) Sporophyte Example Gametophyte (n) Dominant Reduced, dependent on gametophyte for nutrition Mosses and other nonvascular plants Ferns and other seedless vascular plants Seed plants (gymnosperms and angiosperms) PLANT GROUP GymnospermAngiosperm Microscopic female gametophytes (n) inside ovulate cone Microscopic male gametophytes (n) inside pollen cone Sporophyte (2n) Microscopic female gametophytes (n) inside these parts of flowers Microscopic male gametophytes (n) inside these parts of flowers

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Heterospory: The Rule Among Seed Plants Seed plants are heterosporous – Megasporangia produce megaspores that give rise to female gametophytes 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 © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Heterospory: The Rule Among Seed Plants Seed plants are heterosporous – Megasporangia produce megaspores that give rise to female gametophytes – Microsporangia produce microspores that give rise to male gametophytes 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 eliminates the need for a film of water and can be dispersed great distances by air or animals

Copyright © 2008 Pearson Education, Inc., publishing as Pearson 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 Seeds provide some evolutionary advantages over spores: – They may remain dormant for days to years, until conditions are favorable for germination – They may be transported long distances by wind or animals

Seed coat (derived from integument) (c) Gymnosperm seed Embryo (2n) (new sporophyte) Food supply (female gametophyte tissue) (n) (b) Fertilized ovule(a) Unfertilized ovule Integument Immature female cone Spore wall Megasporangium (2n) Male gametophyte (within a germinated pollen grain) (n) Megaspore (n) MicropylePollen grain (n) Egg nucleus (n) Discharged sperm nucleus (n) Female gametophyte (n)

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Gymnosperm Evolution Fossil evidence reveals that by the late Devonian period some plants, called progymnosperms, had begun to acquire some adaptations that characterize seed plants Living seed plants can be divided into two clades: gymnosperms and angiosperms – Gymnosperms appear early in the fossil record and dominated the Mesozoic terrestrial ecosystems – Gymnosperms were better suited than nonvascular plants to drier conditions – Today, cone-bearing gymnosperms called conifers dominate in the northern latitudes

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Phylum Cycadophyta Individuals have large cones and palmlike leaves These thrived during the Mesozoic, but relatively few species exist today Gymnosperm Evolution

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Phylum Ginkgophyta This phylum consists of a single living species, Ginkgo biloba It has a high tolerance to air pollution and is a popular ornamental tree Gymnosperm Evolution

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Phylum Gnetophyta This phylum comprises three genera Species vary in appearance, and some are tropical whereas others live in deserts Gymnosperm Evolution

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Phylum Coniferophyta This phylum is by far the largest of the gymnosperm phyla Most conifers are evergreens and can carry out photosynthesis year round Gymnosperm Evolution

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings The Life Cycle of a Pine: A Closer Look Three key features of the gymnosperm life cycle are: – Dominance of the sporophyte generation – Development of seeds from fertilized ovules – The transfer of sperm to ovules by pollen

Fig Microsporangium (2n) Microsporocytes (2n) Pollen grains (n) Pollen cone Microsporangia MEIOSIS Mature sporophyte (2n) Haploid (n) Diploid (2n) Key MEIOSIS Surviving megaspore (n) Pollen grain Megasporocyte (2n) Ovule Integument Ovulate cone FERTILIZATION Pollen tube Female gametophyte Sperm nucleus (n) Egg nucleus (n) Archegonium Seedling Seeds Seed coat (2n) Food reserves (n) Embryo (2n) Megasporangium (2n)

Origin of land plants (about 475 mya) Origin of vascular plants (about 420 mya) Origin of extant seed plants (about 305 mya) ANCES- TRAL GREEN ALGA Liverworts Hornworts Mosses Lycophytes (club mosses, spike mosses, quillworts) Pterophytes (ferns, horsetails, whisk ferns) Gymnosperms Angiosperms Seed plants Seedless vascular plants Nonvascular plants (bryophytes) Land plants Vascular plants Millions of years ago (mya)

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings The reproductive adaptations of angiosperms include flowers and fruits Angiosperms are seed plants with reproductive structures called flowers and fruits All angiosperms are classified in a single phylum, Anthophyta – The name comes from the Greek anthos, flower – The flower is an angiosperm structure specialized for sexual reproduction – Many species are pollinated by insects or animals, while some species are wind-pollinated

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings A flower is a specialized shoot with up to four types of modified leaves: – Sepals, which enclose the flower – Petals, which are brightly colored and attract pollinators – Stamens, which produce pollen on their terminal anthers – Carpels, which produce ovules Various fruit adaptations help disperse seeds Seeds can be carried by wind, water, or animals to new locations The reproductive adaptations of angiosperms include flowers and fruits

Fig Carpel Ovule Sepal Petal Stigma Style Ovary Stamen Anther Filament

Fig Hazelnut Ruby grapefruit Tomato Nectarine Milkweed

Fig Barbs Seeds within berries Wings

Fig MEIOSIS Key Microsporangium Microsporocytes (2n) Generative cell Anther Tube cell Pollen grains Microspore (n) Male gametophyte (in pollen grain) (n) Mature flower on sporophyte plant (2n) Haploid (n) Diploid (2n) MEIOSIS Ovule (2n) Ovary Megasporangium (2n) Megaspore (n) Female gametophyte (embryo sac) Antipodal cells Central cell Synergids Egg (n) Pollen tube Stigma Sperm (n) Discharged sperm nuclei (n) FERTILIZATION Germinating seed Embryo (2n) Endosperm (3n) Seed coat (2n) Seed Nucleus of developing endosperm (3n) Zygote (2n) Egg nucleus (n) Style Sperm

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Angiosperm Evolution Clarifying the origin and diversification of angiosperms poses fascinating challenges to evolutionary biologists Angiosperms originated at least 140 million years ago During the late Mesozoic, the major branches of the clade diverged from their common ancestor

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Angiosperm Diversity The two main groups of angiosperms are – monocots (one cotyledon) – eudicots (“true” dicots)

Fig n Monocot Characteristics Eudicot Characteristics Vascular tissue usually arranged in ring Veins usually parallel Vascular tissue scattered Leaf venation One cotyledon Embryos Two cotyledons Stems Veins usually netlike

Fig o Roots Pollen Root system usually fibrous (no main root) Pollen grain with three openings Pollen grain with one opening Floral organs usually in multiples of three Flowers Floral organs usually in multiples of four or five Monocot Characteristics Eudicot Characteristics Taproot (main root) usually present

Origin of land plants (about 475 mya) Origin of vascular plants (about 420 mya) Origin of extant seed plants (about 305 mya) ANCES- TRAL GREEN ALGA Liverworts Hornworts Mosses Lycophytes (club mosses, spike mosses, quillworts) Pterophytes (ferns, horsetails, whisk ferns) Gymnosperms Angiosperms Seed plants Seedless vascular plants Nonvascular plants (bryophytes) Land plants Vascular plants Millions of years ago (mya)

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Human welfare depends greatly on seed plants No group of plants is more important to human survival than seed plants Plants are key sources of food, fuel, wood products, and medicine Our reliance on seed plants makes preservation of plant diversity critical

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Products from Seed Plants Most of our food comes from angiosperms Six crops (wheat, rice, maize, potatoes, cassava, and sweet potatoes) yield 80% of the calories consumed by humans Modern crops are products of relatively recent genetic change resulting from artificial selection Many seed plants provide wood Secondary compounds of seed plants are used in medicines

Table 30-1a

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Threats to Plant Diversity Destruction of habitat is causing extinction of many plant species Loss of plant habitat is often accompanied by loss of the animal species that plants support At the current rate of habitat loss, 50% of Earth’s species will become extinct within the next 100–200 years

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings You should now be able to: 1.Describe four shared characteristics and four distinct characteristics between charophytes and land plants 2.Diagram and label the life cycle of a bryophyte 3.Explain why most bryophytes grow close to the ground and are restricted to periodically moist environments 4.Describe three traits that characterize modern vascular plants and explain how these traits have contributed to success on land 5.Explain how vascular plants differ from bryophytes 6.Diagram and label the life cycle of a seedless vascular plant 7.Explain why pollen grains were an important adaptation for successful reproduction on land 8.Describe the life history of a pine; indicate which structures are part of the gametophyte generation and which are part of the sporophyte generation 9.Identify and describe the function of the following floral structures: sepals, petals, stamens, carpels, filament, anther, stigma, style, ovary, and ovule