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Plant Phylogenetic Description
 

Plant Phylogenetic Description

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    Plant Phylogenetic Description Plant Phylogenetic Description Document Transcript

    • Diversity of LifeThe Kingdom of PlantsKing ChloroplastMajor Groups: Extant phyla within the kingdom Plantae
    • A. Non-vascular plants (bryophytes) 1. Marchantiophyta - liverworts 2. Anthocerotophyta- hornworts 3. Bryophyta - mosses B. Vascular plants (tracheophytes) 1. Lycopodiophyta - clubmosses 2. Equisetophyta - horsetails 3. Pteridophyta - "true" ferns 4. Psilotophyta - whisk ferns 5. Ophioglossophyta - adderstongues 6. Seed plants (spermatophytes) a) Pinophyta - conifers b) Cycadophyta - cycads c) Ginkgophyta–ginkgo d) Gnetophyta - gnetae e) Magnoliophyta - flowering plantsMosses and their allies,liverworts and hornworts, are the oldest land plants in the world. Theseplants are all non-vascular, meaning they have no tissue for transporting water and nutrientthought the cell. Their spoors must be transported and united into diploid cells by an outsidewater source flowing through the plant. Nutrients must be distributed the same way, with eachpiece of the plant relying on the luck to have nutrients be washed its way. Non vascular plantsare thus limited to a small size, as each cell can only obtain nutrition a direct neighbor celldiffusing some or by water flowing over it. Because of this, the non-vascular plants are only ableto colonize places where water flows regularly.
    • Marchantiophytais the name of the liverwort phylum. These are possibly the oldest landplants in the world, and, together with hornworts, are the most primitive plants to be found today.There are two classes of liverworts, Jungermanniidea(leafy) andMarchantiopsida(leaf-like). Theleafy liverworts in the first generation (gametophyte) look very like mosses. Leaf-like liverwortsin the first generation look like plump leaves. The spoors, rather than being produced on the endof a thin stalk like leafy liverworts, are produced on the underside of an umbrella shape on theend of a thick stalk (thecarpocephalum). Anthocerotophyta is the name of the hornwort phylum.These may also be the oldest landplants in the world. There is only one class in the phylum Anthocerotophyta, it is Anthocerotaewhich has but one order, Anthocerotales .Hornwort cells are notable because, unlike other landplants, their cells contain only one large chloroplast each. Hornwort sporophyte generationsmanifest themselves inside, rather than on, the green central stalk, which splits open uponmaturity to release the spoors. Bryophyta is the name of the moss phylum. While hornworts and liverworts are onlydistantly related to all other plants, mosses are probably the ancestors of most land plants.Though still primitive, being non vascular, mosses are less primitive and more diverse than eitherliverworts or hornworts and have a central support on their leaves. This midrib may be thepredecessor to stalks in vascular plants. The sporophyte of a moss is a long stalk with a capsuleon the end. The sporophyte grows parasitically on the gamete generation until it reachesmaturity, upon which it splits open and releases the spoors. The stalk may remain for some timeafter that. There are three classes in the Moss phylum: Peat Mosses (Sphagnopsida), GraniteMosses (Andreaopsida), and true mosses (Bryopsidia). Peat mosses are often found in bogs andhave historically been burned for fuel.Ferns and their allies (club mosses, horsetails, whip ferns, and adderstounges) are the nextgeneration of plants, and the next line of attack against rocks. They are the first vascular plants,meaning they have developed specialized tissues for water and nutrition transport (roots, stems,leaves). They also develop firm tissues for structural support. All of these together allow earlyvascular plants to reach hithertounknownheights; literally, as some can grow to the sizes of smalltrees, and so monopolize more sunlight. Roots allow the plant to survive when water is notrunning directly over all parts of the plant. If one root is in a sufficiently wet place, it can,distribute the water to all other parts of the plant. However, the spoors of ferns and their alliesrely on water in the same way moss spoors do, requiring the luck for water to run in exactly theright place at the right time for fertilization to occur. Because of this, plants were still limited towet places through which water regularly ran.
    • Psilotophyta is the name of the whisk fern phylum. Whisk ferns are notable because,although they contain vascular stems, they lack roots. Instead, their stems are simply buried inthe ground. Whisk ferns are dichotomous, meaning they branch off in pairs. Taxonomyaccidentally mirroring physiology, there are two genera (only one class, order, and family)within the phylum, Psilotum andTmesipteris. Psilotumis the more primitive of the two, andperhaps the most primitive of vascular plants to be seen today, because it lacks leaves as well asroots, instead having proto-leaf extensions of the stem called enations. However, Tmesipteris’sgametophyte generation has no vascular tissue, so Psilotum appears more advanced until thesporophyte stage. Lycopoidiophyta is the club moss phylum. It is the oldest living phylum of vascularplants, having fossils dating to 420 Megayears ago. This phylum is notable because although itdoes not contain true leaves, but photosynthetic elongations of the stem called enations, eachenations has a vascular trace (capillary). In this way, the club moss phylum links the primitivewhisk ferns and true ferns as the vascular system extends and develops, the leaf being the nextlogical step from vascularized enations. In addition to paving the way for leaves, these plantsassist human society in a financial way, as many of these plants fossilized into what are now coalmines. Their spores are used in fireworks. Equisetophyta is the name of the Horse Tail Phylum. The horse tail phylum evolvedaporximately 400 million years ago, and became very important by the 300-250 Megayear agomark. Horsetails are significant because they demonstrate the gradual evolution of leaves.Horsetail leaves are true leaves, with true vascular systems, but the leaves are not yet evolved tobe fully and gracefully extended on the plant, leaving the plant with small, but true leaves,thereby linking the morphic chain from moss to fern completely. Species in this genus such asthe E. arvensecan regrow from seemingly nothing, having been dug up by the roots, becausehorsetail gametophytes are buried so far into the ground. In the Carboniferous period, horsetailswere big, in two ways, once they covered almost all the world but Australia, and two and theycould grow up to 30 meters (90 ft) tall. Since the rise of seed plants, however, horsetails havesuffered. There is now only one continuing class of horsetail left , Equisetopsida, in it a oneextant order, Equisetales , in that a lone living family, Equisetaceae, which shelters the solesurviving genus, Equisetum , which contains a mere fifteen species. Horsetails are therefore,considered living fossils, but that doesn’t stop them getting weeded out of gardens across the oldworld. Pteridophyta is the name of the fern phylum. Ferns first appeared 350-250 Megayearsago.Since then ferns have evolved into a total of 20,000 species, divided into four classes:Psilotopsida, Equisetopsida, Marattiopsida, andPolypodiopsida, the former being thestereotypical fern most people associate with the name. These thousands of species have beenbusy evolving into many specialized nieces, from banks of rainforest ponds to sheer, dry desertrocks, ferns can be found, despite early plants’ noted difficulties in that area. The gametophytestage of the fern is very hard to find, for it is just a small heart-shaped green leaflet. It is thesporophyte that one imagines when they hear the word “fern.” Fern sporophytes sprout up intofronds (fern-shaped leaves) that shelter spores on their underside and can grow as tall as trees.
    • Ophioglossophyta is the name of the adderstongue, moonwort, and grape-fern phylum.Until recently, adderstongue were thought to be ferns, but gradually biologists have realized thatadderstongue and allies are individual. However, dispute continues. While the currently winningviewpoint gives adderstongueand allies their own phylum, there is another scheme which groupsadderstounges, whisk fern, and horsetails as classes in a single phylum, Archeophyta. Thisphylum, unlike ferns, has underground gametophytes and fleshy roots. In some species it cantake as long as 20 years for a gametophyte to send up a sporophyte, and when that occurs, it isusually a single spore-dusted stalkwhich sprouts a single leaf or frond, if any. There are twofamilies within this phylum, Ophioglossaceae, and the moonworts and grape-ferns,Botrychiaceae. However, it should be noted that some biologists place moonworts withOphioglossacea rather than Botrychiaceae. Adderstongue have more chromosomes than anyother known plant.Gymnosperms (pines, conifers, and allies) are the third category of plants. As ferns and the alliesbefore them, gymnosperms are vascular, but they have advanced an additional giant leap:gymnosperms have pollen, and produce seeds. Pollen allows fertilization to take place at greatdistance, via the wind, rather than directly running water. Seeds are the resultant embryos, but inan egg-like structure, rather than unprotected or nourished. Seeds store food for the embryo, andsurround it with a hard case. This enables offspring to remain dormant until conditions are right,surviving off nutrients within the seeduntil, for example, the next rain. This greatly improvesoffspring survival rate. The name “gymnosperm” means “naked seed” referring to the fact thatthey do not case their ova in ovaries, but instead merely house their ova in cones. Concurrently,their pollen is not displayed in flowers, but simply thrown to the winds (it is because of this thatpine pollen turns all Georgia yellow each spring.) To further legitimize the naked metaphor, thefertilized embryos (seeds) of gymnosperms are not set in fruits, but also thrown to the winds.Gymnosperms have four existent phyla, Pinophyta, Cycadophyta, Ginkgophyta, and Gnetophyta. Cycadophyta is the name of the cycad phylum. Though now rare, this was once adominant phylum during the Jurassic. For this reason cycads are thought of as living fossils.They are evergreen and similar in looks to a palm tree, although true palms are angiosperms.However, the two groups share distribution somewhat, as cycads live in a wide range ofequatorial environments, cycads having been found in sand, dirt and on rocks, in semi-arid andtropical regions about the equator. This is made possible by the small phylum being well adaptedto heat and sunlight, as well as partially adapted to dry conditions, the partial adaption giving
    • flexibility. All cycads have a symbiotic relationship with cyanobacteria, blue - green algae whichlives with the cycads roots, nitrogen fixes the soil, and imparts a toxic quality to cycad seeds.Cycads, like ginkgoes, are either male or female, but never both. Cycad fossils have been foundthat are 280 megayears old, and there are possible (but disputed) cycad fossils dated as far backas 320 megayears ago. The ginkgo phylum has only one living species left in it, Ginkgo biloba. Fossils of thisspecies, or one very like it, can be found as early as the Jurassic, making this tree one of the mostwell known examples of living fossils today. Ginkgo trees are either male or female, but neverboth, as many angiosperms are. They grow aerial roots very slowly some taking as long as 100years, to no known purpose. Pinophyta(until recently, Coniferophyta) is the largest phylum of gymnosperms. So muchso that it used to be considered the only phylum of gymnosperms.They were very successful atthis, it appears, for while there are few species of conifers, they can be found on most of theworld (see map below). As for the classification within Pinophyta, it is currently in dispute.Pinopsidia is the only complete class. The other classes are cited as no longer existent, or asmerely divisions. Pinopsidiahas simple leaves and secondary root and stem growth. This classincludes pines, firs, spruces, redwoods, yews, ect. As those familiar with plants can ascertainfrom the examples given, they cover a wide range, and are most important in boreal forrests ofthe north. Conifer’s distribution The phylum Gnetophyta is the most advanced of the gymnosperms. It is significantbecause, unlike other gymnosperms, it has an angiosperm’s woody vascular bundles. For thisreason, biologists suspect it may be the “missing link” between gymnosperms and floweringplants. This phylum has three orders in it Gnetales, Welwitschiales, and Ephedrales. All togetherthere are only six species in the phylum Gnetophyta.
    • Magnoliophyta (once called Anthophyta) is the flowering plants. This is the only phylum ofangiosperms, which means “enclosed fruit”. The flowering plants are the largest plant phylum interms of number of species by a great deal. Angiosperms encase their seeds in fruit, and their ovaare housed in ovaries, thus this phylum is protecting their offspring wherever possible. Fruitsoften store sugars in order to attract animals into eating them. After a fruit is eaten, the seeds(evolutionarily packaged to be indigestible) will pass through the digestive system of the animaland be deposited elsewhere with a pile of handy fertilizer. This process increases the rate ofreproductive spread and success. Flowers are specialized leaves which all angiosperms have,whether they are as conspicuous as a venus flytrap or as easy to overlook as the flowers of anoak. Flowers often have sugary nectar for the purpose of attracting insects. These insects, whileeating the nectar, will get pollen (male plant gametes) all over itself and then move on to drinkfrom another flower, which will receive the pollen of the old, plus dust the insect with its own.This process is called entimophylly (pollination via insects). Most angiosperms are both maleand female. Many plants like this can pollinate with themselves. Because of adaptations such asthese, Angiosperms generally grow faster and reproduce surer than most conifers, leading tothem taking over most forests in their “old growth” stage, as the final wave of assault by plantson rocks. They will remain that way until a new phylum of plants evolves. There are two classeswithin this phylum, monocot and dicot. Monocot’s seeds have one seed leaf, parallel veins, andtend towards fibrous roots. The number of floral parts is often a multiple of three. The vascularbundles are distributed throught the stem. Dicot’s seeds have two seed leaves, branched veins,and tap roots. Their floral parts are often multiples of four or five and their vascular bundles arearranged in a ring about the stem. Although it is not a rule, monocots are more closely associatedwith grasses while dicots are more often trees