Plant Life

There are almost one third of a million species of plants which range in form from unicellular algae a few microns in diameter to gigantic trees that can grow to a height of 100 meters. Plant Life makes sense of the bewildering diversity of plants by treating them not just as photosynthetic factories, but as living organisms that are the survivors of millions of years of evolutionary struggle. The book examines plants from an evolutionary perspective to show how such a wide range of life forms has evolved and continues to thrive. The book is divided into three main sections. The first introductory section sets out the necessary background of evolutionary and taxonomic theory and introduces a classification of living plants based on the ways in which they have evolved. The second part investigates how the challenges of life in the water and on land have led to the evolution of the major taxonomic groups of the plants, and describes the key adaptations that have contributed to the success of each group. The final section shows how the contrasting environments of the world's major climatic zones have led to the evolution of such different floras as those of tropical rainforests, prairies and deserts. This section introduces a fascinating range of plants with ingenious and often bizarre methods of survival and reproduction. The book is enriched by detailed case studies, points for discussion and suggestions for further investigation. In addition, extensive color plates and line drawings bring the world of plants vividly to life. Clear classification charts and a full glossary are also useful. Plant Life is an essential elementary text for undergraduate students and should prove a breath of fresh air for jaded botanists who are accustomed to the traditional taxonomic grind through the plant kingdom. New, environmental approach in keeping with modern course content. Beautifully written in a clear, concise and accessible style. Extensive colour plates, electron micrographs and line drawings bring the world of plants vividly to life. Uses carefully chosen examples of species in each group, so that students are not overwhelmed with excessive information and species lists. Discussion questions at the end of chapters encourages further reading and provides essay topics for teachers. Clear classification charts and a full glossary provide useful material for revision.

Preface, ix PART 1 1 Evolution and plant diversity, 3 1.1 Introduction-the diversity of plant life, 3 1.2 Factors affecting plant evolution, 3 1.3 The process of evolution, 6 1.4 Life cycles of eukaryotes, 8 1.5 Mechanisms of adaptation,11 1.6 Mechanisms of speciation,12 1.7 Macroevolution and evolutionary trends,17 1.8 Large-scale trends in evolution,18 1.9 Causes and effects of extinction,19 1.10 Points for discussion, 21 2 The evolutionary history of plant life, 22 2.1 Introduction, 22 2.2 The difficulty of reconstructing plant phylogeny, 22 2.3 Methods used to reconstruct phylogeny, 23 2.4 Types of evidence, 24 2.5 Systems of classification, 28 2.6 A simplified classification of photosynthetic organisms, 28 2.7 Points for discussion, 32 PART 2 3 Life afloat, 35 3.1 Introduction, 35 3.2 The first plants, 35 3.3 The cyanobacteria (cyanophyta), 36 3.4 The evolution of eukaryotes, 41 3.5 Radiation of the eukaryotic algae, 42 3.6 The dinoflagellates (pyrrophyta), 43 3.7 The diatoms (bacillariophyta), 45 3.8 The unicellular green algae (chlorophyta), 46 3.9 Points for discussion, 50 4 Life on the rocks, 52 4.1 Introduction, 52 4.2 Selective forces and evolution of benthic organisms, 52 4.3 Groups of multicellular algae, 54 4.4 Reproduction in benthic algae, 61 4.5 Ecology and distribution of algae, 65 4.6 The corals, 66 4.7 Points for discussion, 67 Practical investigations: investigating the design of seaweeds, 67 5 Life on the ground, 69 5.1 Introduction, 69 5.2 Living on dry land, 69 5.3 Adaptation and diversity of the bryophytes, 70 5.4 Growth and form of bryophytes, 70 5.5 Lichens, 82 5.6 Points for discussion, 85 6 Life above the ground, 87 6.1 Introduction, 87 6.2 The first vascular plants, 87 6.3 Adaptive radiation of spore-producing plants, 90 6.4 Growth and form of vascular plants, 92 6.5 Asexual reproduction of vascular plants, 100 6.6 Sexual reproduction of spore-producing plants,101 6.7 Points for discussion, 110 7 Life from seeds, 111 7.1 Introduction,111 7.2 The structure of seeds, 111 7.3 The earliest seed plants, 111 7 A The cycads (cycadophyta),113 7.5 The evolution of secondary thickening, 114 7.6 The conifers (coniferophyta), 115 7.7 The angiosperms (anthophyta),118 7.8 The groups of angiosperms, 122 7.9 The evolution of angiosperm flowers, 123 7.10 Speed dispersal and the evolution of fruit, 128 7.11 Points for discussion,131 PART 3 8 Life in the wet tropics, 135 8.1 Introduction: problems of life in the wet tropics,135 8.2 Tropical rainforests, 135 8.3 Vegetation of the primary rainforest,135 8.4 Vegetation in gaps, 141 8.5 Possible causes of high rainforest diversity, 143 8.6 The effect of humans on rainforests, 144 8.7 Points for discussion, 145 9 Life in seasonal climates, 146 9.1 Introduction, 146 9.2 Distribution and adaptations of trees, 146 9.3 Vegetation of seasonal forests, 149 9.4 Ecology of seasonal forests,153 9.5 The climatic limits of tree growth,155 9.6 Vegetation in areas with short growing seasons, 155 9.7 Ecology of highly seasonal areas, 158 9.8 The effect of humans, 159 9.9 Points for discussion, 160 10 Life on the edge, 161 10.1 Introduction,161 10.2 Life in the desert, 161 10.3 Life in the snow and ice, 166 10.4 Points for discussion, 169 Practical investigations, 169 11 Life back in the water, 171 11.1 Introduction,171 11.2 Life in fresh water,173 11.3 Adaptations to life in salt water,181 11.4 Points for discussion,185 Further reading, 185 Appendix: A classification of plants, 187 Glossary, 193 Index, 203 Colour plate section falls between pp. 110 and 111.