BIOLOGY CONCEPTS & CONNECTIONS Fourth Edition Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Neil A. Campbell Jane B. Reece Lawrence G. Mitchell Martha R. Taylor From PowerPoint ® Lectures for Biology: Concepts & Connections CHAPTER 17 Plants, Fungi, and the Colonization of Land Modules 17.1 – 17.3

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Mutually beneficial associations of plant roots and fungi are common –These associations are called mycorrhizae –They may have enabled plants to colonize land Plants and Fungi—A Beneficial Partnership

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Citrus growers face a dilemma –They use chemicals to control disease-causing fungi –But these also kill beneficial mycorrhizae

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Plants are multicellular photosynthetic eukaryotes –They share many characteristics with green algae –However, plants evolved unique features as they colonized land 17.1 What is a plant?

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 17.1A PLANT LEAF performs photosynthesis CUTICLE reduces water loss; STOMATA allow gas exchange STEM supports plant (and may perform photosynthesis) Surrounding water supports the alga ALGA WHOLE ALGA performs photosynthesis; absorbs water, CO 2, and minerals from the water HOLDFAST anchors the alga ROOTS anchor plant; absorb water and minerals from the soil (aided by mycorrhizal fungi)

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Unlike algae, plants have vascular tissue –It transports water and nutrients throughout the plant body –It provides internal support Figure 17.1B

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Molecular studies indicate that green algae called charophyceans are the closest relatives of plants 17.2 Plants evolved from green algae called charophyceans PLANT EVOLUTION AND DIVERSITY Figure 17.2A, B

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Cooksonia was one of the earliest vascular land plants Figure 17.2C Sporangia

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Two main lineages arose early from ancestral plants 17.3 Plant diversity provides clues to the evolutionary history of the plant kingdom

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 17.3A PALEOZOIC Radiation of flowering plants MESOZOIC CENOZOIC Charophyceans (a group of green algae) Bryophytes (e.g., mosses) Seedless vascular plants (e.g., ferns, horsetails) Gymnosperms (e.g., conifers) Angiosperms First seed plants Early vascular plants Origin of plants

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings One lineage gave rise to bryophytes –These are plants that lack vascular tissue –Bryophytes include mosses, which grow in a low, spongy mat Figure 17.3B

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Vascular plants are the other ancient lineage Ferns and seed plants were derived from early vascular plants and contain –xylem and phloem –well-developed roots –rigid stems

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Ferns are seedless plants whose flagellated sperm require moisture to reach the egg Figure 17.3C

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings A major step in plant evolution was the appearance of seed plants –Gymnosperms –Angiosperms These vascular plants have pollen grains for transporting sperm They also protect their embryos in seeds

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Gymnosperms, such as pines, are called naked seed plants –This is because their seeds do not develop inside a protective chamber The seeds of angiosperms, flowering plants, develop in ovaries within fruits

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings The haploid gametophyte produces eggs and sperm by mitosis –The eggs and sperm unite, and the zygote develops into the diploid sporophyte –Meiosis in the sporophyte produces haploid spores, which grow into gametophytes 17.4 Haploid and diploid generations alternate in plant life cycles ALTERNATION OF GENERATIONS AND PLANT LIFE CYCLES

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 17.4 HAPLOID Meiosis Spores n Mitosis Gametophytes (male and female) n Mitosis Gametes (sperm and eggs) n Fertilization Zygote 2n Mitosis DIPLOID Sporophyte 2n

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Most of a mat of moss consists of gametophytes –These produce eggs and swimming sperm –The zygote stays on the gametophyte and develops into the less conspicuous sporophyte 17.5 Mosses have a dominant gametophyte

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 17.5 Sperm (n) (released from their gametangium) Gametangium containing the egg (n) (remains within gametophyte) Egg Fertilization Zygote (2n) Mitosis and development Sporophytes (growing from gametophytes) HAPLOID DIPLOID Gametophyte (n) Sporangium Stalk Meiosis Spores (n) 5 Mitosis and development Gametophytes (n)

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Ferns, like mosses, have swimming sperm The fern zygote remains on the small, inconspicuous gametophyte –Here it develops into the sporophyte 17.6 Ferns, like most plants, have a dominant sporophyte

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure Gametophyte (n) (underside) Sperm (n) Egg (n) Fertilization Zygote (2n) Mitosis and development New sporophyte growing out of gametophyte Sporophyte (2n) Meiosis Sporangia 5 Spores (n) Mitosis and development HAPLOID DIPLOID

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Ferns and other seedless plants once dominated ancient forests –Their remains formed coal 17.7 Seedless plants formed vast “coal forests” Figure 17.7

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Gymnosperms that produce cones, the conifers, largely replaced the ancient forests of seedless plants –These plants remain the dominant gymnosperms today

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Sporangia in male cones make spores that develop into male gametophytes –These are the pollen grains Sporangia in female cones produce female gametophytes 17.8 A pine tree is a sporophyte with tiny gametophytes in its cones

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 17.8 Egg (n) 1 HAPLOID DIPLOID Sperm (n) Male gametophyte (pollen grain) Female gametophyte (n) Zygote (2n) Seed coat Embryo (2n) Seed Sporophyte Scale Sporangium (2n) Ovule Integument MEIOSIS HAPLOID Pollen grains (male gametophytes) (n) MEIOSISFertilization Female cone bears ovules. 2 Male cone produces spores by meiosis; spores develop into pollen grains 3 Pollination 4 Haploid spore cells in ovule develop into female gametophyte, which makes egg. 5 Male gametophyte (pollen) grows tube to egg and makes and releases sperm. 6 Zygote develops into embryo, and ovule becomes seed. 7 Seed falls to ground and germinates, and embryo grows into tree.

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Most plants are angiosperms –The hallmarks of these plants are flowers 17.9 The flower is the centerpiece of angiosperm reproduction STAMEN Anther Pollen grains Stigma Ovary CARPEL PETAL SEPAL Ovule Figure 17.9A, B

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings The angiosperm life cycle is similar to that of conifers –But it is much more rapid –In addition, angiosperm seeds are protected and dispersed in fruits, which develop from ovaries The angiosperm plant is a sporophyte with gametophytes in its flowers

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure HAPLOID DIPLOID Egg (n) Ovule Stigma Pollen grain Pollen tube Sperm Fertilization Seed coat Embryo (2n) Seeds Sporophyte Ovary Ovule Pollen (n) Meiosis 1 Haploid spores in anthers develop into pollen grains: male gametophytes. 2 Haploid spore in each ovule develops into female gametophyte, which produces egg. 3 Pollination and growth of pollen tube 4 Zygote (2n) 5 Seed 6 Fruit 7 Seed germinates, and embryo grows into plant. Food supply

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Fruits are adaptations that disperse seeds The structure of a fruit reflects its function in seed dispersal Figure 17.11A-C

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Gymnosperms supply most of our lumber and paper Angiosperms provide most of our food –Fruits, vegetables, and grains Angiosperms also provide other important products –Medications, fiber, perfumes Connection: Agriculture is based almost entirely on angiosperms

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Angiosperms are a major source of food for animals –Animals also aid plants in pollination and seed dispersal Interactions with animals have profoundly influenced angiosperm evolution Figure 17.13A-C

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 20% of the tropical forests worldwide were destroyed in the last third of the 20 th century The forests of North America have shrunk by almost 40% in the last 200 years Connection: Plant diversity is a nonrenewable resource Figure 17.14

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Some plants in these forests can be used in medicinal ways –More than 25% of prescription drugs are extracted from plants Table 17.14

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Plants probably moved onto land along with mycorrhizal fungi –These fungi help plants absorb water and nutrients –They are mutualistic organisms Fungi and plants moved onto land together FUNGI

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Other fungi are Figure 17.15A-C –parasites –predators –decomposers of dead organisms

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Fungi are heterotrophic eukaryotes –They digest their food externally and absorb the nutrients Fungi absorb food after digesting it outside their bodies

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings A fungus usually consists of a mass of threadlike hyphae –This forms a network called a mycelium Figure 17.16A-B Hypha Mycelium

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Most fungi cannot move Figure 17.16C, D –But they grow around and through their food very rapidly

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Fungal spores germinate to form haploid hyphae Many fungi have three distinct phases in their life cycle

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings In some fungi such as mushrooms, the fusion of hyphae results in a unique dikaryotic phase of their life cycle –Each cell contains two haploid nuclei from different parents The dikaryotic mycelium forms a fruiting body, the mushroom –This structure contains specialized cells in which the nuclei fuse –These diploid cells then undergo meiosis, producing a new generation of spores

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure DIPLOID HAPLOID DIKARYOTIC Haploid nucleus Spore Meiosis Fusion of haploid nuclei 1 Fruiting body (mushroom) 2 Diploid nuclei 3 Spores released 4 Germination of spores and growth of mycelia 5 Fusion of two hyphae of compatible mating types 6 Growth of dikaryotic mycelium

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Algal cell Fungal hyphae Lichens are associations of algae or cyanobacteria with a network of fungal hyphae –The fungus receives food in exchange for housing, water, and minerals Lichens consist of fungi living mutualistically with photosynthetic organisms Figure 17.18A, B

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Lichens survive in hostile environments –They cover rocks and frozen tundra soil Figure 17.18C

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Parasitic fungi cause disease –Dutch elm disease –Corn smut –Athlete’s foot Connection: Parasitic fungi harm plants and animals Figure 17.19A-C

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Numerous fungi are beneficial Many are important in the decomposition of organic material and nutrient recycling Connection: Fungi have an enormous ecological and practical impact

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Fungi are also important as food –Mushrooms are the fruiting bodies of subterranean fungi –Yeasts (unicellular fungi) are essential for baking and beer and wine production –Fungi are used to ripen certain cheeses Figure 17.20A

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Some fungi produce antibiotics –Penicillin was the first antibiotic to be discovered Figure 17.20B Staphylococcus aureus Penicillium Zone of inhibited growth