Chapter 17. Plants, Fungi, and the Colonization of Land. Lecture by Joan Sharp

Chapter 17 Plants, Fungi, and the Colonization of Land PowerPoint Lectures for Biology: Concepts & Connections, Sixth Edition Campbell, Reece, Taylor, Simon, and Dickey Copyright 2009 Pearson Education, Inc. Lecture by Joan Sharp

Introduction: Plants and Fungi A Beneficial Partnership Plants and fungi colonized land together Mycorrhizae, mutually beneficial associations of plant roots and fungi hyphae, enabled plants to colonize land Mycorrhizal fungi absorb water, phosphorus, and other minerals from soil and make them available to the plant The sugars produced by the plant nourish the fungus Copyright 2009 Pearson Education, Inc.

17.1 Plants have adaptations for life on land 500 million years ago, the algal ancestors of plants formed a green carpet on the edge of lakes and coastal salt marshes Green algae called charophytes are the closest living relatives of plants Copyright 2009 Pearson Education, Inc.

17.1 Plants have adaptations for life on land Land plants are a clade, defined by a set of derived characters Alternation of haploid and diploid generations Walled spores produced in sporangia Male and female gametangia Multicellular, dependent sporophyte embryos Copyright 2009 Pearson Education, Inc.

17.1 Plants have adaptations for life on land Challenges of terrestrial life Maintaining moisture within cells Obtaining resources from soil and air Supporting body in air Reproducing and dispersing offspring without water Copyright 2009 Pearson Education, Inc.

Key Vascular tissue Leaf Spores Pollen Alga Water supports alga. Whole alga performs photosynthesis; absorbs water, CO 2, and minerals from water. Flagellated sperm Spores Leaf Stem Roots Holdfast (anchors alga) Flagellated sperm Flagellated sperm Moss Stomata only on sporophytes; primitive roots anchor plants, no lignin; no vascular tissue; fertilization requires moisture Stem Roots Fern Stomata; roots anchor plants, absorb water; lignified cell walls; vascular tissue; fertilization requires moisture Seed Leaf Stem Roots Pine tree Stomata; roots anchor plants, absorb water; lignified cell walls; vascular tissue; fertilization does not require moisture

Key Vascular tissue Leaf Spores Alga Water supports alga. Whole alga performs photosynthesis; absorbs water, CO 2, and minerals from water. Spores Leaf Flagellated sperm Stem Roots Holdfast (anchors alga) Flagellated sperm Flagellated sperm Moss Stomata only on sporophytes; primitive roots anchor plants, no lignin; no vascular tissue; fertilization requires moisture Stem Roots Fern Stomata; roots anchor plants, absorb water; lignified cell walls; vascular tissue; fertilization requires moisture

Key Vascular tissue Pollen Seed Leaf Stem Roots Pine tree Stomata; roots anchor plants, absorb water; lignified cell walls; vascular tissue; fertilization does not require moisture

17.1 Plants have adaptations for life on land In all plants, the zygote develops into an embryo while attached to and nourished by the parent plant Plants are embryophytes, with multicellular, dependent embryos Copyright 2009 Pearson Education, Inc.

17.2 Plant diversity reflects the evolutionary history of the plant kingdom Four key adaptations for life on land distinguish the main lineages of the plant kingdom Dependent embryos (characteristic of all plants) Lignified vascular tissues Seeds Flowers Copyright 2009 Pearson Education, Inc.

Ancestral green alga 1 Origin of land plants (about 475 mya) Liverworts Hornworts Mosses 2 Origin of vascular plants (about 425 mya) Lycophytes (club mosses, spike mosses, quillworts) Pterophytes (ferns, horsetails, whisk ferns) 3 Origin of seed plants (about 360 mya) Gymnosperms Angiosperms 500 450 400 350 300 0 Millions of years ago (mya)

17.3 Haploid and diploid generations alternate in plant life cycles The haploid gametophyte produces gametes (eggs and sperm) by mitosis Fertilization results in a diploid zygote The zygote develops into the diploid sporophyte, which produces haploid spores by meiosis Spores grow into gametophytes Copyright 2009 Pearson Education, Inc.

Key Haploid (n) Diploid (2n) Gametophyte plant (n) Mitosis Sperm Gametes (n) Egg

Key Haploid (n) Diploid (2n) Gametophyte plant (n) Mitosis Sperm Gametes (n) Egg Zygote (2n) Fertilization

Key Haploid (n) Diploid (2n) Gametophyte plant (n) Mitosis Sperm Gametes (n) Egg Zygote (2n) Fertilization Sporophyte plant (2n) Mitosis

Key Haploid (n) Diploid (2n) Gametophyte plant (n) Mitosis Sperm Spores (n) Gametes (n) Egg Meiosis Fertilization Zygote (2n) Sporophyte plant (2n) Mitosis

Key Haploid (n) Diploid (2n) Mitosis Gametophyte plant (n) Mitosis Sperm Spores (n) Gametes (n) Egg Meiosis Fertilization Zygote (2n) Sporophyte plant (2n) Mitosis

17.4 Mosses have a dominant gametophyte Gametophytes make up a bed of moss They produce eggs and flagellated sperm in gametangia Sperm swim through water to the egg The zygote develops within the gametangium into a mature sporophyte, which remains attached to the gametophyte Meiosis occurs in sporangia at the tips of the sporophyte stalk Haploid spores are released from the sporangium and develop into gametophytes Copyright 2009 Pearson Education, Inc.

Key Haploid (n) Diploid (2n) Male Gametophytes (n) 1 Sperm (n) Female gametangium Female 1 Egg (n) Fertilization

Key Haploid (n) Diploid (2n) Male Gametophytes (n) 1 Sperm (n) Female gametangium Female 1 Egg (n) Fertilization 2 Zygote (2n)

Key Haploid (n) Diploid (2n) Male Gametophytes (n) 1 Sperm (n) Female gametangium Female 1 Egg (n) Fertilization Sporangium Stalk 2 Sporophyte (2n) Zygote (2n) 3 Mitosis and development

Key Haploid (n) Diploid (2n) Male Gametophytes (n) 1 Sperm (n) Female gametangium Spores (n) Female 1 Egg (n) Fertilization Sporangium Stalk Meiosis 4 Sporophyte (2n) 2 Zygote (2n) 3 Mitosis and development

Key Haploid (n) Diploid (2n) 5 Mitosis and development Male Gametophytes (n) 1 Sperm (n) Female gametangium Spores (n) Female 1 Egg (n) Fertilization Sporangium Stalk Meiosis 4 Sporophyte (2n) 2 Zygote (2n) 3 Mitosis and development

17.5 Ferns, like most plants, have a dominant sporophyte Fern gametophytes are small and inconspicuous They produce flagellated sperm that swim to the egg and fertilize it to produce a zygote The zygote initially develops within the female gametangia but eventually develops into an independent sporophyte Sporangia develop on the underside of the leaves of the sporophyte Within the sporangia, cells undergo meiosis to produce haploid spores Spores are released and develop into gametophytes Copyright 2009 Pearson Education, Inc.

Key Haploid (n) Diploid (2n) 1 Sperm (n) Gametophyte (n) Female gametangium (n) Egg (n) Fertilization

Key Haploid (n) Diploid (2n) 1 Sperm (n) Gametophyte (n) Female gametangium (n) Egg (n) Fertilization 2 Zygote (2n)

Key Haploid (n) Diploid (2n) 1 Sperm (n) Gametophyte (n) Female gametangium (n) Egg (n) Fertilization 4 Clusters of sporangia New sporophyte (2n) 2 Zygote (2n) 3 Mitosis and development Mature sporophyte

Key Haploid (n) Diploid (2n) 1 Sperm (n) 5 Mitosis and development Female gametangium (n) Spores (n) Gametophyte (n) Egg (n) Meiosis Fertilization 4 Clusters of sporangia New sporophyte (2n) 2 Zygote (2n) 3 Mitosis and development Mature sporophyte

17.6 Seedless plants dominated vast coal forests Seedless plants formed vast ancient forests in lowlying wetlands during the Carboniferous period (360 299 million years ago) When they died, the plants formed peat deposits that eventually formed coal Coal, oil, and natural gas are fossil fuels Oil and natural gas formed from marine organisms; coal formed from seedless plants Burning fossil fuels releases CO 2, causing climate warming Copyright 2009 Pearson Education, Inc.

17.7 A pine tree is a sporophyte with gametophytes in its cones A pine cone holds all of the tree s reproductive stages: spores, eggs, sperm, zygotes, and embryos Each scale of the cone contains sporangia that produce spores by meiosis The spores produce gametophytes within the cone The male gametophyte is a pollen grain, released from pollen cones and carried by wind to female cones Female ovulate cones carry two ovules on each stiff scale Each ovule contains a sporangium surrounded by the integument Animation: Pine Life Cycle Copyright 2009 Pearson Education, Inc.

1 Sporangia produce spores; spores develop into pollen grains. Sporangium (2n) Scale Ovule Meiosis Pollen grains (male gametophytes) (n) 3 Meiosis Spore mother cell (2n) Integument Pollination 2 Ovulate cone bears ovules. Mature sporophyte Key Haploid (n) Diploid (2n)

1 Sporangia produce spores; spores develop into pollen grains. 2 Meiosis Sporangium (2n) Pollen grains (male gametophytes) (n) Ovulate cone bears ovules. 3 Scale Ovule 4 A haploid spore cell develops into female gametophyte, which makes eggs. Meiosis Spore mother cell (2n) Integument Pollination Egg (n) Sperm (n) Male gametophyte (pollen grain) 5 Female gametophyte (n) Pollen grows tube to egg and makes and releases sperm. Fertilization Mature sporophyte Key Haploid (n) Diploid (2n)

17.7 A pine tree is a sporophyte with gametophytes in its cones In pollination, a pollen grain lands on a scale in an ovulate cone and enters an ovule The scales then grow together, sealing up the cone Within the sealed cone, the gametophytes produce gametes Fertilization occurs a year after pollination, when a sperm moves down a pollen tube to the egg to form a zygote The zygote develops into a sporophyte embryo, and the ovule becomes a seed, with stored food and a protective seed coat The seed is a key adaptation for life on land and a major factor in the success of seed plants Copyright 2009 Pearson Education, Inc.

17.8 The flower is the centerpiece of angiosperm reproduction Flowers contain separate male and female sporangia and gametophytes Flowers usually consist of sepals, petals, stamens (which produce pollen), and carpels (which produce eggs) Sepals enclose the flower before it opens Petals attract animal pollinators Stamens include a filament and anther, a sac at the top of each filament that contains male sporangia and releases pollen Copyright 2009 Pearson Education, Inc.

Stigma Stamen Anther Style Carpel Filament Ovary Petal Sepal Receptacle Ovule

17.8 The flower is the centerpiece of angiosperm reproduction The carpel is the female reproductive structure, including the ovary The ovary encloses the ovules, which contain sporangia that will produce a female gametophyte Ovules develop into seeds; ovaries mature into fruit Copyright 2009 Pearson Education, Inc.

17.9 The angiosperm plant is a sporophyte with gametophytes in its flowers The angiosperm life cycle 1. Meiosis in the anthers produces haploid spores that form the male gametophyte (pollen grains) 2. Meiosis in the ovule produces a haploid spore that forms a tiny female gametophyte, including the egg 3. A pollen tube from the pollen grain to the ovule carries a sperm that fertilizes the egg to form a zygote 4. Each ovule develops into a seed, consisting of an embryo (a new sporophyte) with a food supply and a seed coat 5. The ovary wall forms a fruit Copyright 2009 Pearson Education, Inc.

17.9 The angiosperm plant is a sporophyte with gametophytes in its flowers Animation: Plant Fertilization Video: Flowering Plant Life Cycle (time lapse) Animation: Seed Development Copyright 2009 Pearson Education, Inc.

1 Haploid spores in anthers develop into pollen grains: male gametophytes. Pollen grains (n) Meiosis 2 Haploid spore in each ovule develops into female gametophyte, which produces an egg. Meiosis Egg (n) Ovule Key Haploid (n) Diploid (2n)

1 Haploid spores in anthers develop into pollen grains: male gametophytes. 2 Meiosis Meiosis Pollen grains (n) Haploid spore in each ovule develops into female gametophyte, which produces an egg. Egg (n) 3 Pollination and growth of pollen tube Stigma Pollen grain Pollen tube Ovule Sperm Fertilization Key Haploid (n) Diploid (2n)

1 Haploid spores in anthers develop into pollen grains: male gametophytes. Meiosis Pollen grains (n) 3 Pollination and growth of pollen tube Stigma Anther 2 Haploid spore in each ovule develops into female gametophyte, which produces an egg. Meiosis Egg (n) Stigma Pollen grain Pollen tube Sporophyte (2n) Ovule Ovary Ovule 7 Seed germinates, and embryo grows into Seeds plant. Sperm 6 Fruit (mature ovary) Key Haploid (n) Diploid (2n) 5 Seed Food supply Seed coat Embryo (2n) 4 Fertilization Zygote (2n)

17.10 The structure of a fruit reflects its function in seed dispersal Fruits, ripened ovaries of flowers, are adaptations that disperse seeds Some rely on wind for seed dispersal Some hitch a ride on animals Fleshy, edible fruits attract animals Animation: Fruit Development Copyright 2009 Pearson Education, Inc.

17.11 CONNECTION: Angiosperms sustain us and add spice to our diets Most human food is provided by the fruits and seeds of angiosperms Corn, rice, wheat, and other grains are dry fruits Apples, cherries, tomatoes, and squash are fleshy fruits Spices such as nutmeg, cinnamon, cumin, cloves, ginger, and licorice are also angiosperm fruits Copyright 2009 Pearson Education, Inc.

17.12 EVOLUTION CONNECTION: Pollination by animals has influenced angiosperm evolution 90% of angiosperms use animals to transfer pollen Birds are attracted by colorful flowers, but not scent Beetles are attracted by fruity odors, but not color Bats are attracted by large, highly scented flowers Wind-pollinated flowers produce large amounts of pollen Copyright 2009 Pearson Education, Inc.

17.13 CONNECTION: Plant diversity is an irreplaceable resource More than 50,000 square miles of forest are cleared every year Replanted areas have greatly reduced biological diversity Loss of forests has greatly reduced diversity of life on Earth The loss of plant diversity removes potentially beneficial medicines More than 25% of prescription drugs are extracted from plants Copyright 2009 Pearson Education, Inc.

17.14 Fungi absorb food after digesting it outside their bodies Fungi are absorptive heterotrophic eukaryotes that digest their food externally and absorb the nutrients Most fungi consist of a mass of threadlike hyphae making up a mycelium Hyphal cells are separated by cross-walls with pores large enough for ribosomes, mitochondria, and nuclei to cross Some are multinucleate without cross-walls Hyphae have a huge surface area to secrete digestive enzymes and absorb food Fungal hyphae are surrounded by a cell wall with chitin Animation: Fungal Reproduction and Nutrition Copyright 2009 Pearson Education, Inc.

Mycelium Hypha

17.15 Fungi produce spores in both asexual and sexual life cycles Many fungal species can reproduce both sexually and asexually Fungi produce huge numbers of asexual spores, each of which can germinate to form a new fungus In many fungi, sexual fusion of haploid hyphae leads to a heterokaryotic stage, in which cells contain two genetically distinct haploid nuclei Hours or centuries may pass before parental nuclei fuse to form a short-lived diploid phase Zygotes undergo meiosis inside specialized reproductive structures and disperse haploid spores Copyright 2009 Pearson Education, Inc.

Key Haploid (n) Heterokaryotic (n + n) (unfused nuclei) Diploid (2n) Spore-producing structures Spores (n) Asexual Mycelium reproduction Germination Heterokaryotic stage Fusion of cytoplasm Germination Spores (n) Sexual reproduction Fusion of nuclei Meiosis Spore-producing structures Zygote (2n)

17.16 Fungi are classified into five groups Sexual reproductive structures are used to classify fungi Fungi with no known sexual stage are known as imperfect fungi Fungi likely evolved from an aquatic, flagellated ancestor shared with animals Chytrids, which have flagellated spores, are the earliest lineage of fungi Animals and fungi diverged into separate lineages 1.5 billion years ago The oldest fungal fossils are 460 million years old Copyright 2009 Pearson Education, Inc.

Chytrids Zygomycetes (zygote fungi) Glomeromycetes (arbuscular mycorrhizal fungi) Ascomycetes (sac fungi) Basidiomycetes (club fungi)

17.16 Fungi are classified into five groups Zygomycetes Zygote fungi form resistant zygosporangia in which haploid spores form by meiosis This group includes black bread mold Copyright 2009 Pearson Education, Inc.

17.16 Fungi are classified into five groups Glomeromycetes These fungi form mycorrhizae, in which invasive hyphae branch into treelike arbuscules within plant roots 90% of plants have symbiotic partnerships with glomeromycetes Copyright 2009 Pearson Education, Inc.

17.16 Fungi are classified into five groups Ascomycetes Sac fungi form saclike asci, which produce sexual spores They range in size from yeasts to elaborate morels and cup fungi Some form lichens in association with green algae or cyanobacteria Copyright 2009 Pearson Education, Inc.

17.16 Fungi are classified into five groups Basidiomycetes Club fungi are the mushrooms, puffballs, and shelf fungi They have club-shaped spore-producing structures called basidia These fungi are important forest decomposers Copyright 2009 Pearson Education, Inc.

17.17 Fungal groups differ in their life cycles and reproductive structures Hyphae reproduce asexually by producing spores in sporangia at the tips of upright hyphae When food is depleted, the fungus reproduces sexually Mycelia of different mating types join and produce a zygosporangium, which develops into a thickwalled structure that can tolerate dry, harsh conditions Under favorable conditions, the parental nuclei fuse and the diploid nucleus undergoes meiosis to form haploid spores Copyright 2009 Pearson Education, Inc.

Key Haploid (n) Heterokaryotic (n + n) Diploid (2n) Zygosporangium (n + n) Mycelia of different mating types Cells fuse 2 3 1 Fusion of nuclei Young zygosporangium (heterokaryotic) Sporangium Meiosis 4 Spores (n)

17.17 Fungal groups differ in their life cycles and reproductive structures Hyphae of different mating types fuse to form a heterokaryotic mycelium, which grows to produce a mushroom Haploid nuclei fuse to form diploid nuclei in the clubshaped cells called basidia that line the gills of the mushroom Each diploid nucleus undergoes meiosis to form haploid spores Copyright 2009 Pearson Education, Inc.

Key Haploid (n) Heterokaryotic (n + n) Diploid (2n) 1 Fusion of two hyphae of different mating types

Key Haploid (n) Heterokaryotic (n + n) Diploid (2n) Mushroom 2 Growth of heterokaryotic mycelium 1 Fusion of two hyphae of different mating types

Key Fusion of nuclei 3 Diploid nuclei Haploid (n) Heterokaryotic (n + n) Diploid (2n) Basidia Mushroom 2 Growth of heterokaryotic mycelium 1 Fusion of two hyphae of different mating types

Key Fusion of nuclei 3 Diploid nuclei Haploid (n) Meiosis Heterokaryotic (n + n) Diploid (2n) Basidia Haploid nuclei 4 Spores released Mushroom Spores (n) 2 Growth of heterokaryotic mycelium 1 Fusion of two hyphae of different mating types

17.18 CONNECTION: Parasitic fungi harm plants and animals 80% of plant diseases are caused by fungi Between 10 and 50% of the world s fruit harvest is lost each year to fungal attack A variety of fungi, including smuts and rusts, infect grain crops Only 50 species of fungi are parasitic on animals, causing mycoses Human infections include athlete s foot (caused by ringworm) Systemic mycoses are rare but serious fungal infections that spread through the body from inhaled spores Copyright 2009 Pearson Education, Inc.

Ergots

17.19 Lichens consist of fungi living in close association with photosynthetic organisms Lichens consist of algae or cyanobacteria within a fungal network Many lichen associations are mutualistic The fungus receives food from its photosynthetic partner The fungal mycelium helps the alga absorb and retain water and minerals Lichens are important pioneers on new land, where they help to form soil Lichens are sensitive to air pollution, because they obtain minerals from the air Copyright 2009 Pearson Education, Inc.

Fungal hyphae Algal cell

17.20 Some fungi have mutually beneficial relationships with ants Several species of ants and termites cultivate fungal gardens The insects feed their fungi with leaves, weeding out undesirable fungi The fungi feed on the leaves The ants harvest the swollen hyphal tips Farmer insects and fungal crops have been evolving together for over 50 million years Copyright 2009 Pearson Education, Inc.

17.21 CONNECTION: Fungi have enormous ecological benefits and practical uses Fungi have many practical uses for humans Some fungi can break down toxic pollutants, including pesticides like DDT and cancer-causing chemicals Fungi may be able to clean up oil spills and chemical messes We eat many fungi, from mushrooms to cheeses modified by fungi Yeasts produce alcohol and cause bread to rise Fungi provide antibiotics that are used to treat bacterial disease Fungi are playing important new roles in molecular biology and biotechnology Copyright 2009 Pearson Education, Inc.

Staphylococcus aureus Penicillium Zone of inhibited growth

Leaves carry out photosynthesis Reproductive structures, as in flowers, contain spores and gametes Cuticle covering leaves and stems reduces water loss Stomata in leaves allow gas exchange between plant and atmosphere Lignin hardens cell walls of some plant tissues Stem supports plant; may perform photosynthesis Vascular tissues in shoots and roots transport water, minerals, and sugars; provide support Roots anchor plant; mycorrhizae (rootfungus associations) help absorb water and minerals from the soil

ANCESTRAL GREEN ALGA 1 a. 2 b. c. 3 d.

A. Pine tree, a gymnosperm B. Puffball, a club fungus

You should now be able to 1. Describe the key plant adaptations for life on land 2. Describe the alternation of generation life cycle; explain why it appears that this cycle has evolved independently in algae and land plants 3. Describe the key events of the moss, fern, and pine life cycles 4. Explain how coal was formed; explain why coal, oil, and natural gas are called fossil fuels Copyright 2009 Pearson Education, Inc.

You should now be able to 5. Describe the parts of a flower and explain their functions 6. Describe the stages of the angiosperm life cycle 7. Describe angiosperm adaptations that promote seed dispersal 8. Explain how flowers are adapted to attract pollinators 9. Compare the life cycles and reproductive structures in the fungal groups Copyright 2009 Pearson Education, Inc.