Chapter 21 The Diversity of Plants Lecture Outlines by Gregory Ahearn University of North Florida Copyright 2011 Pearson Education Inc Chapter 21 At a Glance 21 1 What Are the Key Features of Plants 21 2 How Do Plants Affect Other Organisms 21 5 What Are the Major Groups of Plants Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 21 1 What Are the Key Features of Plants Most plants have the ability to photosynthesize The multicellular embryo of a plant is retained within and receives nutrients from the tissues of the parent plant Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 21 1 What Are the Key Features of Plants Plants exhibit alternation of generations a multicellular diploid generation alternates with a multicellular haploid generation A diploid sporophyte plant produces haploid spores The spores divide by mitosis and develop into haploid through meiosis gametophyte plants Haploid gametophyte plants produce haploid male and female gametes through mitosis Gametes of opposite sex fuse to form diploid zygotes which divide by mitosis and develop into diploid sporophytes Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 21 2 How Do Plants Affect Other Organisms Plants play a crucial ecological role Plants make vital contributions to the food air soil and water that sustain life on land Plants capture energy that other organisms use Through photosynthesis plants provide food directly or indirectly for all the animals fungi and nonphotosynthetic microbes on land Plants help maintain the atmosphere Plants produce oxygen gas as a by product of photosynthesis continually replenishing oxygen in the atmosphere Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 21 2 How Do Plants Affect Other Organisms Plants play a crucial ecological role continued Plants build soil Dead plant material is decomposed by fungi prokaryotes and other decomposers into organic matter Decomposed plant tissue helps the soil hold water and nutrients making it more fertile The roots of living plants help hold the soil together preventing erosion by wind and water Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 21 2 How Do Plants Affect Other Organisms Plants help keep ecosystems moist Plants take up and store water from the soil slowing the rate at which water escapes terrestrial ecosystems Plants also slow the rate of water runoff and flooding Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 21 2 How Do Plants Affect Other Organisms Plants provide humans with necessities and luxuries Plants provide shelter fuel and medicine Wood is used to construct housing Wood is an important fuel for warming and cooking in many parts of the world Coal is another important fuel and is derived from the remains of ancient plants that have been transformed by geological processes Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 21 2 How Do Plants Affect Other Organisms Plants provide shelter fuel and medicine continued Many medicines and drugs were originally found in and extracted from plants for example aspirin the heart medication digoxin Taxol the malaria drug quinine and pain killers such as morphine and codeine Humans have domesticated a host of useful plant species Plants provide pleasure through flowers gardens lawns and parks and through coffee tea and wine Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 21 5 What Are the Major Groups of Plants Two major groups of land plants arose from ancient green algal ancestors The nonvascular plants called bryophytes require a moist environment to reproduce and therefore they straddle the boundary between aquatic and terrestrial life The vascular plants called tracheophytes have been able to colonize dry habitats Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 21 5 What Are the Major Groups of Plants Nonvascular plants lack conducting structures They lack true roots stems or leaves Instead they have rhizoids root like anchoring structures Because they must instead rely on slow diffusion or poorly developed conducting tissues to distribute water and other nutrients nonvascular plants are of limited body size most less than 2 5 cm tall Their absence of a stiffening agent in the cell walls also limits their size Biology Life on Earth 9e Copyright 2011 Pearson Education Inc Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 21 5 What Are the Major Groups of Plants Nonvascular plants include the hornworts liverworts and mosses Hornwort sporophytes generally have a spiky shape that appears hornlike The gametophytes of certain liverwort species have a lobed form reminiscent of a liver All hornworts liverworts and most mosses are found in moist areas near banks of streams and ponds and in forests Biology Life on Earth 9e Copyright 2011 Pearson Education Inc Mosses are diverse have waterproof covering that retains moisture Accumulations of dead mosses form peat which is used as fuel Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 21 5 What Are the Major Groups of Plants The reproductive structures of nonvascular plants are protected Gametes develop within protected structures on the haploid gametophyte Archegonia singular archegonium produce eggs Antheridia singular antheridium produce sperm Some nonvascular plant species have both archegonia and antheridia on the same plant Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 21 5 What Are the Major Groups of Plants The reproductive structures of nonvascular plants are protected continued Reproduction involves several steps Sperm swim to an egg Fertilization occurs and a diploid sporophyte develops within the archegonium of the gametophyte The sporophyte produces encapsulated haploid spores via meiosis Haploid spores disperse and germinate into new haploid gametophytes Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 21 5 What Are the Major Groups of Plants Vascular plants have conducting cells that also provide support These plants are distinguished by specialized groups of tube shaped conducting cells These cells are impregnated with the stiffening agent lignin The diploid sporophyte generation is dominant Vascular plants can be divided into two groups the seedless vascular plants and the seed plants Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 21 5 What Are the Major Groups of Plants The seedless vascular plants include the club mosses horsetails and
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