Embed Size (px)
Citation preview
BIOLOGICAL DIVERSITY: NONVASCULAR PLANTS AND NONSEED VASCULARPLANTS
Table of Contents
Evolution of Plants | The Plant Life Cycle | Plant Adaptations to Life on Land
Bryophytes | Tracheophytes: The Vascular Plants | Vascular Plant Groups | The Psilophytes | TheLycophytes
The Sphenophyta | The Ferns | Learning Objectives | Terms | Review Questions | Links
The plant kingdom contains multicellular phototrophs that usually live on land. The earliestplant fossils are from terrestrial deposits, although some plants have since returned to the water.All plant cells have a cell wall containing the carbohydrate cellulose, and often have plastids intheir cytoplasm. The plant life cycle has an alternation between haploid (gametophyte) anddiploid (sporophyte) generations. There are more than 300,000 living species of plants known,as well as an extensive fossil record.
Plants divide into two groups: plants lacking lignin-impregnated conducting cells (thenonvascular plants) and those containing lignin-impregnated conducting cells (the vascularplants). Living groups of nonvascular plants include the bryophytes: liverworts, hornworts, andmosses. Vascular plants are the more common plants like pines, ferns, corn, and oaks. Thephylogenetic relationships within the plant kingdom are shown in Figure 1.
Figure 1. Phylogenetic reconstruction of the possible relationships between plant groups andtheir green algal ancestor. Note this drawing proposes a green algal group, the Charophytes, aspossible ancestors for the plants. Image from Purves et al., Life: The Science of Biology, 4thEdition, by Sinauer Associates (www.sinauer.com) and WH Freeman (www.whfreeman.com),used with permission.
Evolution of Plants | Back to Top
Fossil and biochemical evidence indicates plants are descended from multicellular green algae.Various green algal groups have been proposed for this ancestral type, with the Charophytesoften being prominently mentioned. Cladistic studies support the inclusion of the Charophytes(including the taxonomic order Coleochaetales) as sister taxa to the land plants. Algaedominated the oceans of the precambrian time over 700 million years ago. Between 500 and 400million years ago, some algae made the transition to land, becoming plants by developing aseries of adaptations to help them survive out of the water.
Table 1. Photosynthetic pigments of algae and plants. Prokaryote groups are shown in red,protists in blue, and vascular plants in purple.
TaxonomicGroup Photosynthetic Pigments
Cyanobacteria chlorophyll a, chlorphyll c,phycocyanin, phycoerythrin
Chloroxybacteria chlorophyll a, chlorphyll bGreen Algae(Chlorophyta)
chlorophyll a, chlorphyll b,carotenoids
Red Algae(Rhodophyta)
chlorophyll a, phycocyanin,phycoerythrin, phycobilins
Brown Algae(Phaeophyta)
chlorophyll a, chlorphyll c,fucoxanthin and othercarotenoids
Golden-brownAlgae(Chrysophyta)
chlorophyll a, chlorphyll c,fucoxanthin and othercarotenoids
Dinoflagellates(Pyrrhophyta)
chlorophyll a, chlorphyll c,peridinin and other carotenoids
Vascular Plants chlorophyll a, chlorphyll b,carotenoids
Vascular plants appeared by 350 million years ago, with forests soon following by 300 millionyears ago. Seed plants next evolved, with flowering plants appearing around 140 million yearsago. This pattern is shown in Figure 2.
Figure 2. The fossil records of some protist and plant groups. The width of the shaded space isan indicator of the number of species. Image from Purves et al., Life: The Science of Biology,4th Edition, by Sinauer Associates (www.sinauer.com) and WH Freeman(www.whfreeman.com), used with permission.
The Plant Life Cycle | Back to Top
Plants have an alternation of generations: the diploid spore-producing plant (sporophyte)alternates with the haploid gamete-producing plant (gametophyte), as shown in Figure 3.Animal life cycles have meiosis followed immediately by gametogenesis. Gametes are produceddirectly by meiosis. Male gametes are sperm. Female gametes are eggs or ova.
Figure 3. Typical alternation of generations life cycle, such as occur in some protistans andplants. Image from Purves et al., Life: The Science of Biology, 4th Edition, by SinauerAssociates (www.sinauer.com) and WH Freeman (www.whfreeman.com), used withpermission.
The plant life cycle has mitosis occurring in spores, produced by meiosis, that germinate intothe gametophyte phase. Gametophyte size ranges from three cells (in pollen) to several million(in a "lower plant" such as moss). Alternation of generations occurs in plants, where thesporophyte phase is succeeded by the gametophyte phase. The sporophyte phase producesspores by meiosis within a sporangium. The gametophyte phase produces gametes by mitosiswithin an antheridium (producing sperm) and/or archegonium (producing eggs). These differentstages of the flowering plant life cycle are shown in Figure 4. Within the plant kingdom thedominance of phases varies. Nonvascular plants, the mosses and liverworts, have thegametophyte phase dominant. Vascular plants show a progression of increasing sporophytedominance from the ferns and "fern allies" to angiosperms.
Figure 4. The life cycle stages of a flowering plant. The above image is reduced fromgopher://wiscinfo.wisc.edu:2070/I9/.image/.bot/.130/Angiosperm/Angiosperm_life_cycle.Follow that link to view a larger image.
Homospory and Heterospory
Plants have two further variations on their life cycles. Plants that produce bisexual gametophytes
have those gametophytes germinate from isospores (iso=same) that are about all the same size.This state is referred to as homospory (sometimes referred to as isospory). A generalizedhomosporous plant life cycle is shown in Figure 5. Homosporous plants produce bisexualgametophytes. Ferns are a classic example of a homosporous plant.
Figure 5. A typical homosporous life cycle. Note the production of a single type of bisexualgametophyte that will eventually produce the antheridia (sperm bearing structures) andarchegonia (egg bearing structures). Image from Purves et al., Life: The Science of Biology,4th Edition, by Sinauer Associates (www.sinauer.com) and WH Freeman(www.whfreeman.com), used with permission.
Plants that produce separate male and female gametophytes have those gametophytes germinatefrom (or within in the case of the more advanced plants) spores of different sizes (heterospores;hetero=different). The male gametophyte produces sperm, and is associated with smaller ormicrospores. The female gametophyte is associated with the larger or megaspores. Heterosporyis considered by botanists as a significant step toward the development of the seed. Ageneralized heterosporous life cycle is shown in Figure 6.
Figure 6. Typical heterosporous life cycle. Note the production of separate, unisexual male andfemale gametophytes. Image from Purves et al., Life: The Science of Biology, 4th Edition, bySinauer Associates (www.sinauer.com) and WH Freeman (www.whfreeman.com), used withpermission.
Plant Adaptations to Life on Land | Back to Top
Organisms in water do not face many of the challenges that terrestrial creatures do. Watersupports the organism, the moist surface of the creature is a superb surface for gas exchange,etc. For organisms to exist on land, a variety of challenges must be met.
1. Drying out. Once removed from water and exposed to air, organisms must deal with theneed to conserve water. A number of approaches have developed, such as the developmentof waterproof skin (in animals), living in very moist environments (amphibians,bryophytes), and production of a waterproof surface (the cuticle in plants, cork layers andbark in woody trees).
2. Gas exchange. Organisms that live in water are often able to exchange carbon dioxide andoxygen gases through their surfaces. These exchange surfaces are moist, thin layers acrosswhich diffusion can occur. Organismal response to the challenge of drying out tends tomake these surfaces thicker, waterproof, and to retard gas exchange. Consequently,another method of gas exchange must be modified or developed. Many fish already hadgills and swim bladders, so when some of them began moving between ponds, the swimbladder (a gas retention structure helping buoyancy in the fish) began to act as a gasexchange surface, ultimately evolving into the terrestrial lung. Many arthropods had gillsor other internal respiratory surfaces that were modified to facilitate gas exchange on land.Plants are thought to share common ancestry with algae. The plant solution to gasexchange is a new structure, the guard cells that flank openings (stomata) in the aboveground parts of the plant. By opening these guard cells the plant is able to allow gasexchange by diffusion through the open stomata.
3. Support. Organisms living in water are supported by the dense liquid they live in. Once onland, the organisms had to deal with the less dense air, which could not support theirweight. Adaptations to this include animal skeletons and specialized plant cells/tissues thatsupport the plant.
4. Conduction. Single celled organisms only have tyo move materials in, out, and withintheir cells. A multicellular creature must do this at each cell in the body, plus move
material in, out, and within the organism. Adaptations to this include the circulatorysystems of animals, and the specialized conducting tissues xylem and phloem in plants.Some multicellular algae and bryophytes also have specialized conducting cells.
5. Reproduction. Organisms in water can release their gametes into the water, where thegametes will swim by flagella until they ecounter each other and fertilization happens. Onland, such a scenario is not possible. Land animals have had to develop specializedreproductive systems involving fertilization when they return to water (amphibians), orinternal fertilization and an amniotic egg (reptiles, birds, and mammals). Insects developedsimilar mechanisms. Plants have also had to deal with this, either by living in moistenvironments like the ferns and bryophytes do, or by developing specialized deliverysystems like pollen tubes to get the sperm cells to the egg.
Bryophytes | Back to Top
Bryophytes are small, nonvascular plants that first evolved approximately 500 million years ago.The earliest land plants were most likely bryophytes. Bryophytes lack vascular tissue and havelife cycles dominated by the gametophyte phase, as shown in Figure 7. The lack of conductingcells limits the size of the plants, generally keeping them under 5 inches high. Roots are absentin bryophytes, instead there are root-like structures known as rhizoids. Bryophytes include thehornworts, liverworts, and mosses.
Figure 7. The moss life cycle. The haploid gametophyte phase is free-living andphotosynthetic. The diploid sporophyte grows from and is nourished by the gametophyte.Images from Purves et al., Life: The Science of Biology, 4th Edition, by Sinauer Associates(www.sinauer.com) and WH Freeman (www.whfreeman.com), used with permission.
Tracheophytes: The Vascular Plants | Back to Top
The vascular plants have specialized transporting cells xylem (for transporting water and mineralnutrients) and phloem (for transporting sugars from leaves to the rest of the plant). When wethink of plants we invariably picture vascular plants. Vascular plants tend to be larger and morecomplex than bryophytes, and have a life cycle where the sporophyte is more prominent than thegametophyte. Vascular plants also demonstrate increased levels of organization by havingorgans and organ systems. The novel features oif the vascular plants are summarized in Table 2.
Table 2. Major evolutionary advances of the vascular plants.
Advance Green Algae Bryophytes Tracheophytes
Developmentof the root-stem-leafvascularsystem
nonvascularized body(thallus) that may bevariously shaped
no levaes, shoots, orroots
no vascular system
leaflike structures are present,but lack any vascular tissue
early vascular plants are naked,rootless vascularized stems
later vascular plants developvascularized leaves, then roots
Reduction inthe size ofthegametophytegeneration
wide range of lifecycles, somegametophytedominant, otherssporophyte dominant
sporophyte generationdependant on gametophytegeneration for food;gametophyte is free-living andphotosynthetic
progressive reduction in size andcomplexity of the gametoiphytegeneration, leading to its completedependance on the sporophyte forfood
in angiosperms, 3 celled malegametophyte and a (usually) 8 celledfemale gametophyte
Developmentof seeds in
of seeds insomevascularplants
no seeds no seeds seed plants retain the femalegametophyte on the sporophyte
Spores/Pollenspores for resistingenvironmentaldegradation
Spores that germinate into thegametophyte generation
Spores that germinate into thegametophyte generation or sporesthat have the gametophyte generationdevelop within themselves
Vascular Plant Groups | Back to Top
Vascular plants first developed during the Silurian Period, about 400 million years ago. Theearliest vascular plants had no roots, leaves, fruits, or flowers, and reproduced by producingspores.
Cooksonia, shown in Figure 8, is a typical early vascular plant. It was less than 15 cm tall, withstems that dichotomously branched. Dichotomous branching (where the stem divides into twoewqual branches) appears a primitive or ancestral trait in vascular plants. Some branchesterminated in sporangia that produced a single size of spore.
Many scientists now consider "Cooksonia" an evolutionary grade rather than a truemonophyletic taxon. Their main argument is that not all stems of Cooksonia-type plants havevascular tissue. The evolutionary situation of a grade would have some members of the grouphaving the trait, others not. The shapes of sporangia on various specimens of Cooksonia alsovary considerably.
Figure 8. Cooksonia fossil specimen (L) and reconstruction (R). Both Images fromhttp://www.ucmp.berkeley.edu.
Rhynia, shown in Figure 9, is another early vascular plant. Like Cooksonia, it lacked leaves and
roots. One of the species formerly assigned to this genus, R. major, has since been reclassifiedas Aglaophyton major. Some paleobotanists consider A. major (Figure 10) a bryophyte,however, it does have a separate free-living sporophyte that is more prominent than thesporophyte, but appears to lack lignified conducting cells. The remaining species, R. gwynne-vaughanii is an undoubted vascular plant.
Figure 9. Rhynia gwynne-vaughanii (L) stem cross section from the Rhynie Chert in Scotland.Image cropped and reduced from http://www.uni-muenster.de/GeoPalaeontologie/Palaeo/Palbot/rhynie.html. (R) Reconstruction of the plant,from http://www.ucmp.berkeley.edu/IB181/VPL/Elp/Elp2.html.
Figure 10. Reconstruction of Aglaophyton major (A-C) and Lyonophyton rhyniensis, anotherRhynie Chert plant thought to be the gametophyte of Aglaophyton. Image from the UCMPBerkeley website.
Devonian plant lines included the trimerophytes and zosterophyllophytes, which have been
interpreted as related to ferns and lycophytes.
The Psilophytes | Back to Top
The Division Psilophyta consists of Psilotum nudum (the whisk fern, shown in Figure 11), aliving plant that resembling what paleobotanists believe Cooksonia to have been: a naked,photosynthetic stem bearing sporangia. Also in the group is Tmesipteris, which resemblesPsilotum except for its possession of smallo vascularized leaves arising on opposite sides of thestem. However, most paleobotanists doubt that Psilotum is a direct descendant of Cooksonia.Molecular studies suggest an affiliation with ferns for Psilotum. Psilotum also has three fusedsporangia, termed a synangium, located on the sides of the stems (instead of the tips of stems asin Cooksonia).
Figure 11. Psilotum nudum from Hawaii. Note the synangia, the roundish structures on the sideof the green stems. Image fromhttp://www.botany.hawaii.edu/faculty/carr/images/psi_nud_mid.jpg.
The Lycophytes | Back to Top
The next group, the Division Lycophyta, have their sporangia organized into strobili (singular:strobilus). A strobilus is a series of sporangia and modified leaves closely grouped on a stem tip.The leaves in strobili are soft and fleshy as opposed to the hard, modified leaves in cones.
Leaves that contained vascular tissue are another major advance for this group. The presumedevolutionary pathway for the leaf is shown in Figure 12. The leaves in lycophytes, both livingand fossil forms, are known as microphylls. This term does not imply any size constraint, butrather refers to the absence of a leaf gap in the vascular supply of the stem at the point wherethe leaf vascular trace departs. Ferns and other plants have megaphylls, leaves that produce thisleaf gap.
Figure 12. Proposed steps in the evolution of the microphyll leaf. Note that microphylls do notleave a leaf gap in the stem's vascular cylinder. If we wanted to place Psilotum-like plants onthe left top, we would have Lycopodium-like plants on the right top. Image from Purves et al.,Life: The Science of Biology, 4th Edition, by Sinauer Associates (www.sinauer.com) and WHFreeman (www.whfreeman.com), used with permission.
Today there are fewer genera of lycophytes than during the group's heyday, the Paleozoic Era.Major living lycophytes include Lycopodium (commonly called the club moss [shown in Figure13], although it is NOT a moss), Isoetes, and Selaginella (the so-called resurrection plant).Lycopodium produces isospores that germinate in the soil and produce a bisexual gametophyte.These spores are all approximately the same size. Selaginella and Isoetes are heterosporous, andthus produce two sizes of spores: small spores (termed microspores) that germinate to producethe male gametophyte; and larger spores (megaspores) that germinate to produce the femalegametophyte. The production of two sizes of spores, and also making separate unisexualgametophytes, is thought an important step toward the seed. Modern lycophytes are small,herbaceous plants. Many of the prominent fossil members of this group produced large amountsof wood and were significant trees in the Carboniferous-aged coal swamps.
Figure 13. Lycopodium venustulum, from from Hawaii. Note the strobili on the tips of thestems, as well as the stems covered with numerous spirally arranged microphylls. Image from
http://www.botany.hawaii.edu/faculty/carr/images/lyc_ven.jpg.
Selaginella is a heterosporous member of the lycophytes. Some species of this genus are able towithstand drying out by going dormant until they are rehydrated. For this reason these forms ofthe genus are commonly called resurrection plants. An example of this is shown in Figure 14.
Figure 14. Selaginella lepidophylla. The top part of the image shows the dried plant, the middlepart shows the resurrected or rehydrated plant. Image fromhttp://www.orchideeitalia.it/selaginella.jpg.
Fossil Lycophytes: Baragwanathia and Drepanophycus
Baragwanathia, shown in Figure 15, is an undoubted lycophyte from the middle Siluriandeposits of Australia. It has microphyllous leaves spirally attached to the stem, and sporangiaclustered in some areas of the plant, although not in terminal strobili as in modern lycophytes.
Figure 15. Left: Reconstruction of Baragwanathia longifolia, from the middle Silurian ofAustralia. Image from http://www.ucmp.berkeley.edu/IB181/VPL/Lyco/Lyco1.html; Right:Reconstruction of Drepanophycus , a middle Devonian lycophyte. Note the numerousmicrophyll leaves, placement of sporangia on the upper surface of the sporophylls, and stemanatomy that are all consistent with modern lycophytes. Image fromhttp://www.ucmp.berkeley.edu/IB181/VPL/Lyco/Lyco2.html.
Drepanophycus is a middle Devonian lycophyte from the Northern Hemisphere, also shown inFigure 15. Its features are very similar to modern lycophytes.
Lepidodendron and Sigillaria
The Lycophytes became significant elements of the world's flora during the Carboniferous time(the Mississippian and Pennsylvanian are terms used for this time span in the United States).These non-seed plants evolved into trees placed in the fossil genera Lepidodendron andSigillaria, with heights reaching up to 40 meters and 20-30 meters respectively. Lepidodendronstems are composed of less wood (secondary xylem) that usually is found in gymnosperm andangiosperm trees.
We know much about the anatomy of these coal-age lycopods because of an odd type ofpreservation known as a coal ball. Coal balls can be peeled and the plants that are anatomicallypreserved within them laboriously studied to learn the details of cell structure of these coal ageplants. Additionally, we have some exceptional petrifactions and compressions that revealdifferent layers of the plants' structure. Estimates place the bulk, up to 70%, of coal material asbeing derived from lycophytes.
Lepidodendron, pictured in Figures 16 and 17, was a heterosporous lycophyte tree common incoal swamps of the Carboniferous time. As with many large plant fossils, one rarely if everfinds the entire tree preserved intact. Consequently there are a number of fossil plant genera thatare "organ taxa" and represent only the leaves (such as Lepidophylloides), reproductivestructures (Lepidostrobus), stem (Lepidodendron), spores (Lycospora), and roots (Stigmaria).Lepidodendron had leaves borne spirally on branches that dichotomously forked, with roots alsoarising spirally from the stigmarian axes, and both small (microspores) and large (megaspores)formed in strobili (a loose type of soft cone). Lepidodendron may have attained heigths ofnearly 40 meters, with trunks nearly 2 meters in diameter. The trees branched extensively andproduced a large number of leaves. When these leaves fell from the branches, they left behindthem the leaf scars characteristic of the genus.
Figure 16. External stem features typical of arborescent lycopods, collectively called
lepidodendrids, based on the diamond-shaped "snakeskin" type pattern produced by thehelically arranged leaf cushions. On the left is a lower magnification view of this type ofpattern, showing the general features of many of these trees. Each leaf abscissed, so that if youare looking, as you are here, at the outside of the stem, you can see a characteristic appearance.On the right is a higher magnification photo showing details of leaf cushions. Each diamondshaped cushion has a smaller central area called the leaf base where the leaf attached. In thecenter of the leaf base you can see the leaf trace, or vein to the leaf. The vertical stripe runningdown each cushion is probably the result of increased girth from secondary cortical growthinside the stem. Images and text from http://lsvl.la.asu.edu/plb407/kpigg/lepidodendrid.htm,used with permission of K.B. Pigg, Arizona State University.
Figure 17. Top: Cross section through a branch (approximately an inch in diameter) of a largelepidodendrid tree. In the very center is a pith, surrounded by primary xylem and a small fringeof secondary xylem [wood, MJF]. Then there is black gunk and an open white area. Phloemand innermost cortical tissues are typically not well preserved, and this black gunk and whiteareas probably represent their positions in the branch. The outermost part of the stem is gone.Images and text from http://lsvl.la.asu.edu/plb407/kpigg/lepidostemxs.htm, used withpermission of K.B. Pigg, Arizona State University. Bottom: Reconstructed diorama ofCarboniferous forest scene. Note the ferns and sphenopsids growing around the fallenLepidodendron trunk, and a large calamite tree in the right foreground. Image and text fromhttp://seaborg.nmu.edu/earth/carbonif/car01b.html.
Sigillaria was another arborescent lycopod, and is also common in coal-age deposits. In contrastto the spirally borne leaves of Lepidodendron, Sigillaria had leaved arranged in vertical rowsalong the stem.
The Sphenophyta | Back to Top
The Division Sphenophyta contains once dominant plants (both arborescent as well asherbaceous) in Paleozoic forests, equisetophytes are today relegated to minor roles asherbaceous plants. Today only a single genus, Equisetum, survives. The group is defined bytheir jointed stems, with many leaves being produced at a node, production of isospores in conesborne at the tips of stems, and spores bearing elaters (devices to aid in spore dispersal).Sporophyte features are seen in Figure 18. The gametophyte is small, bisexual, photosynthetic,and free-living. Silica concentrated in the stems give this group one of their common names:
scouring rushes. These plants were reportedly used by American pioneers to scour the pots andpans. The fossil members of this group are often encountered in coal deposits of Carboniferousage in North America and Europe.
Figure 18. Top: A branched species of Equisetum from Hawaii. Note that the branches arisefrom the same node/area along the stem. Image fromhttp://www.botany.hawaii.edu/faculty/carr/images/equ_sp.jpg. Bottom: Closeup view of thecone of Equisetum hyemale from Hawaii. Note the small leaves at the joints near the letteringin the picture. Image from http://www.botany.hawaii.edu/faculty/carr/images/equ_sp_cu.jpg.
The Ferns | Back to Top
Ferns reproduce by spores from which the free-living bisexual gametophyte generationdevelops. There are 12,000 species of ferns today, placed in the Division Pteridophyta. Thefossil history of ferns shows them to have been a dominant plant group during the PaleozoicEra. Most ferns have pinnate leaves, exhibiting small leaflets on a frond, as shown in Figure 19.Ferns have megaphyllous leaves, which cause a leaf gap in the vascular cylinder of thestem/rhizome, as shown in Figure 20. The first ferns also appear by the end of the Devonian.Some anatomical similarities suggest that ferns and sphenophytes may have shared a commonancestor within the trimerophytes.
Figure 19. Three genera of the fern family Gleicheniaceae from Hawaii: Upper left: Sticherisowhyhensis, lower left: Diploterygium pinnatum (uluhe lau nui), right: Dicranopteris linearis(uluhe). Image from http://www.botany.hawaii.edu/faculty/carr/gleicheni.htm.
Figure 20. Formation of leaf gaps by a megaphyllous leaf. Most plants above the ferns havemegaphyllous leaves. Image from Purves et al., Life: The Science of Biology, 4th Edition, bySinauer Associates (www.sinauer.com) and WH Freeman (www.whfreeman.com), used withpermission.
The Fern Life Cycle
The fern gametophyte has both sexes present and is referred to as a prothallium. Prothalliadevelop from spores shed from the underside of the sporophyte leaves, shown in Figure 21.Once fertilization occurs, the next generation sporophyte develops from the egg located in theprothallium.
Figure 21. Sporangia on the underside of Polypodium pellucidum from Hawaii. Image fromhttp://www.botany.hawaii.edu/faculty/carr/images/pol_pel.jpg.
Composite of 4 segmented diagrams of the fern life cycle. Note: to view this in its propersequence you will need to open your browsert window as wide as possible. Images from Purveset al., Life: The Science of Biology, 4th Edition, by Sinauer Associates (www.sinauer.com) andWH Freeman (www.whfreeman.com), used with permission.
Learning Objectives | Back to TopBe able to discuss the differences in life cycle between vascular and nonvascular plants.Both bryophytes and vascular plants have leaf-like structures. Be able to prepare a single sentence thatcan tell the reader what a leaf is, as well as what it is not.Both heterospory and homospory impose certain constraints on the gametophyte generation. List someof these.Be able to compare and contrast the typical plant life cycle and a typical animal one.Psilotum is NOT a primitive vascular plant, but rather has more genetic similarity to ferns. What sortsof information might we gather from studying modern Psilotum and its ecology as it relates toCooksonia and other early vascular plants.What are the chief differences between vascular and nonvascular plants?The fern gametophyte is bisexual. Speculate on the evolutionary advantages of this in ferncolonization of ecologically disturbed areas.
Terms | Back to Top alternation ofgenerations bark bryophytes Charophytes cork cuticle
gametophyte guard cells homospory andheterospory isospores megaspores microspores
nonvascular plants phototrophs pollen rhizoids spores sporangium
sporophyte stomata strobilus vascularplants
xylem andphloem
Review Questions | Back to Top1. Which of these plant groups may include the ancestors of plants? a) red algae; b) green algae; c)
brown algae; d) fungi ANS is b2. Plants and their ancestral group share which of the following features? a) chlorphylls a and b; b)
strach as a storage product; c) cellulose cell walls; d) all of these ANS is d3. Vascular plants have ___, specialized cells that help support the plant as well as transport water and
nutrients upward from their roots. a) phloem; b) trumpet hyphae; c) xylem; d ) arteries ANS is c4. The ___ generation of a moss is the dominant phase of its life history. a) sporophyte; b) adult; c)
embryo; d) gametophyte ANS is d5. The lack of conducting cells in bryophytes limits their maximum size to ___. a) 100 meters; b) 5 cm;
c) 1 meter; d) no limit is set by the lack of these cells ANS is b6. Which of these plants is known only from fossils? a) Cooksonia; b) Lycopodium; c) Equisetum; d)
Tmesipteris ANS is a7. The ___ generation of a fern is the dominant phase of its life history. a) sporophyte; b) adult; c)
embryo; d) gametophyte ANS is a
Links | Back to TopThe Five Kingdoms A table summarizing the kingdoms of living things.Green Plants from the Tree of Life pages at the University of Arizona. This series of pages leads youdeeper into the systematics of the plants and thier sister taxa.Land Plants Online You can learn more about the various plant groups from this well organized site.
Follow links to look up the structure and geologic history of any major plant group of your choice.Non-Flowering Plant Family Access Page Sorted by family on the non-flowering plants. Thumbnailphotos are linked to larger versions. This site is a great educational resource maintained by Gerald D.Carr.Introduction to the Bryophyta: The Mosses This University of California Museum of Paleontology siteoffers a systematic perspective to the mosses by providing succinct information as well as links to anumber of pertinent sites.Introduction to the Anthocerotophyta: The hornworts This University of California Museum ofPaleontology site offers a systematic perspective to the hornworts by providing succinct informationas well as links to a number of pertinent sites.Encyclopedia of Plants Scientific and common names for garden plants, from a commercial site,botany.com.Garden Web Glossary A nice contrast to the above site, this glossary has over 4000 terms, and is alsofrom a commercial site.Introduction to the Lycophyta: Club mosses and Scale trees This University of California Museum ofPaleontology site offers a systematic perspective to the lycophytes, their ecology, systematics, andfossil record.Introduction to the Sphenophyta: Yesterday's trees, today's horsetails This University of CaliforniaMuseum of Paleontology site offers a systematic perspective to the sphenophytes (Equisetum and itsextinct relatives), their ecology, systematics, and fossil record.Mazon Creek Fossils The Illinois State Museum maintains this site that details and illustrates some ofthe exquisite plant and animal fossils from the Mazon Creek deposits in that state.Plant Fossil Record An exhaustive resource for plant fossils maintained by the Organisation ofPalaeobotany.Die Rhynie Chert Flora This site, in German, offers pictures illustrating the vascular nature, triletespores, and stomata that characterize Rhynia as a vascular plant. The site is also available in English.Rhynie Chert, Scotland From the folks at the University of California Museum of Paleontology, thissite offers a closer look at the Rhynie Chert in Scotland, a significant fossil site with undisputedvascular plant fossils.The Botanical Society of America The official website of the plant biologists, oh well, call thembotanists!Botany Online, The Internet Hypertextbook A wonderful, and still growing, site that offers a wealth ofdetails beyond what I have presented in my pages. Worth a look for those extra facts that make onecomfortable when discussing plants.
All text contents ©1995, 1999, 2000, 2001, 2003, 2004, by M.J. Farabee. Use of the text for educationalpurposes is encouraged.
Back to Table of Contents
Email: [email protected]
Last modified:
The URL of this page is:
