Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings PowerPoint Lectures for Biology, Seventh Edition Neil Campbell and Jane Reece Lectures by Chris Romero Chapter 29 Plant Diversity I How Plants Colonized Land

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 29.1: Land plants evolved from green algae Green algae called charophyceans are the closest relatives of land plants

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Derived Traits of Plants Five key traits appear in nearly all land plants but are absent in the charophyceans: – Apical meristems – Alternation of generations – Walled spores produced in sporangia – Multicellular gametangia – Multicellular dependent embryos

LE 29-5a Apical Meristem of shoot Developing leaves Shoot Root Apical meristem 100 µm Apical Meristems

LE 29-5b Mitosis Alternation of Generations Spores Mitosis Zygote Gametes Haploid multicellular organism (gametophyte) Diploid multicellular organism (sporophyte) MEIOSIS FERTILIZATION

LE 29-5c Walled Spores Produced in Sporangia Multicellular Gametangia Multicellular, Dependent Embryos Longitudinal section of Sphagnum sporangium (LM) Spores Sporangium Sporophyte Gametophyte Sporophyte and sporangium of Sphagnum (a moss) Archegonia and antheridia of Marchantia (a liverwort) Male gametophyte Antheridium with sperm Female gametophyte Archegonium with egg Maternal tissue Embryo 2 µm 10 µm Wall ingrowths Placental transfer cell

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Additional derived traits such as a cuticle and secondary compounds evolved in many plant species

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Origin and Diversification of Plants Fossil evidence indicates that plants were on land at least 475 million years ago Fossilized spores and tissues have been extracted from 475-million-year-old rocks

LE 29-6 Fossilized spores. Unlike the spores of most living plants, which are single grains, these spores found in Oman are in groups of four (left; one hidden) and two (right). Fossilized sporophyte tissue. The spores were embedded in tissue that appears to be from plants.

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Those ancestral species gave rise to a vast diversity of modern plants Land plants can be informally grouped based on the presence or absence of vascular tissue

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

LE 29-7 Ancestral green alga Origin of land plants (about 475 mya) Origin of vascular plants (about 420 mya) Origin of seed plants (about 360 mya) Land plants Vascular plants Seed plants Seedless vascular plantsBryophytes Liverworts HornwortsMosses Lycophytes Pterophytes Gymno- sperms Angio- sperms Charophyceans

LE 29-9b Plagiochila deltoidea, a “leafy” liverwort

LE 29-9c An Anthroceros hornwort species Sporophyte Gametophyte

LE 29-9d Polytrichum commune, hairy cap moss Sporophyte Gametophyte

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Ecological and Economic Importance of Mosses Sphagnum, or “peat moss,” forms extensive deposits of partially decayed organic material known as peat Sphagnum plays an important role in the Earth’s carbon cycle

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Life Cycles with Dominant Sporophytes In contrast with bryophytes, sporophytes of seedless vascular plants are the larger generation, as in the familiar leafy fern The gametophytes are tiny plants that grow on or below the soil surface Animation: Fern Life Cycle Animation: Fern Life Cycle

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Transport in Xylem and Phloem Vascular plants have two types of vascular tissue: xylem and phloem Xylem conducts most of the water and minerals and includes dead cells called tracheids Phloem consists of living cells and distributes sugars, amino acids, and other organic products

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Evolution of Roots Roots are organs that anchor vascular plants They enable vascular plants to absorb water and nutrients from the soil Roots may have evolved from subterranean stems

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Evolution of Leaves Leaves are organs that increase the surface area of vascular plants, thereby capturing more solar energy that is used for photosynthesis

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Significance of Seedless Vascular Plants The ancestors of modern lycophytes, horsetails, and ferns grew to great heights during the Carboniferous, forming the first forests These forests may have helped produce the global cooling at the end of the Carboniferous period The decaying plants of these Carboniferous forests eventually became coal

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings