Note for ECOL 182R with Professor Huxman at UA
Note for ECOL 182R with Professor Huxman at UA
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Date Created: 02/06/15
Posted on web 22607 at 530 pm Evolution of Photoautotrophy Ecol 182 2272007 3 Summary from last time We talked about Factors shaping constraints over photosynthetic rates a series of heirarchical controls with multiple tradeoffs hinge P Relative allocation of Tradeoff between Leaf lifespan returns nitrogen to carboxylation exchanges of water and on C amp N investment versus light harvesting carbon Cowan 1977 reproductive timing and Field and Mooney 1986 Cowan and Farqhuar output Bloom 1986 Farqhuar et al 1980 1977 Bazzaz 1996 Big Questions What have been the important constraints and or principles that have shaped the evolution of plants Diversi cation Form and function Important particularities on evolution and speciation in plants RA Fisher 1958 Fundamental Theorem of Natural Selection But plants do two additional tricks that enhance genetic variation 4 Polyploidy 5 Hybridization Multicellularity and plant evolution Multicellularity evolved more than once Multicellularity has several interesting advantages When is an organism multicellular When neighboring cells adhere interact and physiologically communicate Contact is achieved in four ways 1 T 139th junctions 2 Desmosomes 3 Gap junctions 4 Plasmodesmata Multicellular plant Single living protoplast of adjoining cells Cell membranes which line plasmodesmata are continuous from one cell to the next Water and small molecules may pass with relative ease essentially through the whole plant Material ow may be modified by altering number and location of plasmodesmata What is a plant Plants are photosynthetic eukaryotes A more derived group of plants is called the embryophytes Plants appear monophyletic forming a single branch of the evolutionary tree so says your book gt Brown plantsquot Stramenopiles J Ancestral u organism amp gt Red plants J amp ChlorophytesKm Charophytes gtquotGreen plantsquot P1 t Embryophytes an ae LIFE THE SCIENCE OF BIDLaGY Savant Edition Flglna 291 What Is a Plum r 2004 Smauar Assocrznes me am w H Freeman amp Cm Diversity of Embrophytes Embryophytes fall out into 10 phyla Unique characteristics of plants Alternation of generations is a universal feature of the life cycles of plants The multicellular diploid plant is called the Sporophyte The sporangia on the sporophyte produce haploid unicellular spores by meiosis The multicellular haploid plant formed by mitosis of a spore is called the gametophyte The gametophyte produces haploid gametes The fusion of two gametes results in the formation of a diploid cell the zygote and the cycle repeats Multicellular gametophyte Spore Gamel39es I HAPLOID n DIPLOID 2n Multiccllular SpUl Oph y te Figure 292 in the book Sporophyte generation from the zygote through the adult multicellular diploid plant Gametophyte generation from the spore through the adult multicellular haploid plant to the gamete Charophytes a group of green algae appear to be the closest living relative of Embryophytes These organisms now occupy the margins of ponds or marshes meaning that the jump to a terrestrial environment was in close proximity a Chara sp stonewort b Coleoclzaete Sp LIFE THE SCIENCE OF BIOLOGY Savenlh Edition Figula 25311 Closasi Relatives 01 Land Flam 92001 Sinauer Assnmales inn and w H Freeman 5 Co The Conquest of the Land Embryophytes invaded the terrestrial environment approximately 400 500 mya Some adaptations to life on land Cuticle Gametangia Embryos Pigments Spore wall thickening Mychorhizzae Stomata Aerenchyma The Conquest of the Land Evolution of specialized water conducting cells tracheids allowed for advancement in the terrestrial environment The rst land plants either lacked vascular tissue or like some mosses had very simple conducting tissue that developed from dead cells Chlorophytes Ancestral alga Charophytes Liverworts Protected Hornworts embryos First true vascular Club mosses tissue Ferns and allies v v sal qdoaqaenuoN peasuoN v squad squdoaqamJ P998 a w W First seed 0 Gymno plants sperms Flowering plants squdoatpml aeluuld 1210198qu LIFE THE SCIENCE OF BIOLOGY Sammy Edition gure 294 Fran Green Algae to Phil 9 2004 Smauy Assma es mo and w H Freeman E Co Water and nutrient acquisition by non tracheophytes recall they do not have a vascular system Many grow in dense masses through which water can move by capillary action They have leaflike structures that catch and hold water that splashes onto them They are small enough that a Marclmntin sp minerals can be distributed evenly by diffusion Nontracheophytes Liverworts Hornworts and Mosses Grow in dense mats in moist habitats typically they are small in size Layers of maternal tissue prevent loss of water from the embryo Have a thin cuticle though it is not highly effective in retarding water loss Are Widespread across siX continents and eXist locally on the coast of Antarctica Nontracheophytes Visible green structure is the garnetophyte Sporophyte produces unicellular haploid spores through meiosis within sporangium or capsules Spores germinate and give rise to a rnulticellular haploid gametophyte Whose cells contain chloroplasts Gametophytes n i 9 Ar omum n Photosynthetic filament Protonema Antheridium n with bud Bud HAPLOID n Gametophyte generation Rhizoid DIPLOID 2n Sporophyte generation mari Sporophyte 2n Gametophyte 1 LIFE THE SCIENCE OF BIOLOGY Seventh Edivian Figure 295 A NDniracheophyle Lila Cycle 9 2004 Smauev Assamales me and w H Fveeman 5 Co Gametangia The archegonium The antheridium The sporophyte produces a sporangium Liverworts Several genera have both sexual and asexual reproduction Asexual reproduction by simple fragmentation of the garnetophyte n Marclmntin sp 7 Mnrchantia sp The hornworts phylum Anthocerophyta mosses and tracheophytes all have unique adaptations to life on land These groups all possess stomata that allow the uptake of CO2 and the release of 02 but they can be closed to prevent excessive water loss in some group s Anllmccms sp Two characteristics distinguish hornworts from liverworts and mosses Cyanobacteria often populate internal mucilage lled cavities within hornworts The phylum Bryophyta mosses are probably sister to the tracheophytes Hydroid cells in many mosses are a likely progenitor of the water conducting cells of the tracheophytes cIENcE OF BIGLK 20a The Tracheophytes The sporophyte generation of a nowextinct organism produced a new cell type called the tracheid Allowed for the radiation of a novel life form The tracheid is the principal water conducting element in the xylem in all tracheophytes except the angiosperms The tracheophytes have welldeveloped vasculature consisting of Phloem Xylem The evolution of tracheids had two important consequences Tracheids set the stage for invasion of land by plants Tracheophytes also feature a branching independent sporophyte We break tracheophytes down into at least seven different groups see fig 2910 Nontracheophytes 39 39 39 Z 0 common Club mosses W a ancestor g E 9 Horsetalls g b g Tracheids 0 branching Whisk ferns 1 8 H independent K3 7 3 m klt n sporophyte f d r Iquot l m g quotS Multi agellate n E sperm complex 7 lt 8 leaves k a g Comfers E o m 0 m 9 Seeds R 3 H a a m 839 o Gnetophytes Flowers carpels triploid endosperm Angiosperms LIFE THE SCIENCE OF BIOLOGY Savant Edition Figure 2WThe Evolulinn o1 Tnday39s Flams 2qu Smauer Assocmes me am w H Freeman 5 Co The Tracheophytes Recall plants invaded land about 400500 million years ago During the Devonian period club mosses lycopods horsetails and ferns made the environment more hospitable to animals Trees dominated during the Carboniferous period resulting in forest that eventually become coal deposits At the end of the Permian period the ZOOmillionyear reign of the lycopod fern forests came to an end as they were replaced by forests of seed plants Introducing the Tracheophytes The rst tracheophytes were in the nowextinct phylum Rhyniophyta They had the structural features found in all other tracheophyte phyla Club mosses Lycophyta appeared in the Silurian period Ferns horsetails and whisk ferns Pteridophyta appeared in the Devonian These groups Lycophyta and Pteridophyta had true roots true leaves and a differentiation between two types of spores The Tracheophytes Roots had their origins as branches either as rhizomes or aboveground portion of stems Early roots were simple structures that penetrated soil branching and anchoring the plant absorbing water and minerals Belowground and aboveground environments are quite different Sporan gia Dichotornous quotquot branching The Tracheophytes 0 A leaf a Vascular tissue Sp0rangium Sporan gia Mlcrophy The Tracheophytes The megaphyll is larger and more complex found in ferns and seed plants May have arose from attening of stems and development of overtopping one branch differentiates from and extends beyond rest Overtopping Megaphyll Introducing the Tracheophytes Plants that bear a single type of spore are said to be homosporous The most ancient tracheophytes were all hornosporous Both the gametophyte and the sporophyte are independent and usually photosynthetic A single type of gametophyte bears both female and male reproductive organs Introducing the Tracheophytes Plants with two distinct types of spores evolved later and are said to be heterosporous In heterosporous plants the megaspore develops into a larger speci cally female gametophyte megagametophyte The microspore develops into the smaller male gametophyte microgametophyte Heterospory evolved independently and repeatedly suggesting that it affords selective advantages n Homospory Archegonium 9 Gamatophytc IL II Antheddium d Spove11 390 E Spatmm ggs H HAPLOID I J DIPLOID 2quot Spore mother cell Zn zygote 2 2 H er s 039 c o P y MegagametophyteQ Sporangium 271 Embryo 2quot S l l poggfye chmgamgffphytew mmiima umanvwmimmuruuvrnuNWym mm WWW w m x m Megaspore n Microspore n sperm 1 Eggs 390 HAPLOID I t DH LOIDZn Spore mother Spare mother ZYEOMQ cell 211 cell 2 Mcgasparangium Wdospomngium Embryo 2n 2quot 211 Sporophyke 2H Urswssarm earlmmansnwmsmbmmwnum my MM m The Surviving Nonseed Tracheophytes The club mosses phylum Lycophyta have microphylls exhibit apical growth and have roots that branch dichotomously Sporangia in many club mosses are contained within conelike structures called strobili clusters of spore bearing leaves inserted between a specialized leaf and the stem There are both homosporous and heterosporous species The Lycophyta and the Pteridophyta were the dominant phyla during the Carboniferous period Figure 2915 Club Masses Strobilus Microsporangium a Lycopodium obscm um 7 LIFE THE SCIENCE 0F BIDLDGY Seventh Editian gure 2915 Club Masses 2004 Smauer Assumes m and w H Freeman A Co The Surviving Nonseed Tracheophytes The horsetails Whisk ferns and ferns form a clade the phylum Pteridophyta The horsetails all are genus Equisetum have true roots that branch irregularly and sporangia on short stalks called sporangiophores The leaves are reduced megaphylls and grow in whorls Stern growth is from the base of the stern segments Figure 2916 Horsetails Leaves Sporan gium Sporangiophore Fertile shoot a Equisetum m vense l7 Equisetum pnlustre LIFE THE SCIENCE OF BIOLOGY Seventh Edition Figure 2916 Horsatails 2004 smauer Assocrmes vm am w H Freeman 5 Ca The Surviving Nonseed Tracheophytes The Whisk ferns are two genera of rootless spore bearing plants Psilotum and T mesipteris Psilotum has only minute scales instead of true leaves Although Whisk ferns resemble the most ancient tracheophytes they are now considered to be highly specialized plants that evolved fairly recently Psilotum nudum LIFE THE SCIENCE OF BIOLOGY Sevznfh Edmun Figure 2917 A Whisk Fem uaom Smauel Assommes me am w H Freemans Cu The Surviving Nonseed Tracheophytes The sporophytes of the ferns typically have true roots stems and leaves The ferns rst appeared during the Devonian About 97 of fern species belong to one clade the leptosporangiate ferns These ferns have sporangia with walls only one cell thick borne on a stalk Ferns are characterized by fronds large leaves with complex vasculature Sporangia are found on the undersurfaces of the fronds clustered in groups called sori Figure 2919 Fern Sori Are Clusters of Sporangia Dryopteris intermedia LIFE THE SCIENCE OF BIOLOGY Ssvenlh Edition Figure 2919 Fem Sori Ave Clusters oi Spornngia pm 2004 Smauer Assocwmeg m and w H Freeman 5 Ca Figure 2918 Fern Fronds Take Many Forms a Adiantum pedatum C Marsilea mutich LIFE THE SCIENCE OF BIOLOGY Samm Edrrian Figure 29 Fem andsTake Many Form 2 2004 Sinauer Assmales Inc and w H Freeman 3 Ca The Surviving Nonseed Tracheophytes The sporophyte generation dominates the fern life cycle Spores germinates and form a gametophyte bearing antheridia or archegonia or both The antheridia release sperm that swim to a nearby archegonium and fertilize an egg The sperm are guided by chemical attractants released from the archegonia The resulting diploid embryo forms roots and fronds and grows into the familiar sporophyte life stage Mature gametophyte A Rhizoids 39 Germinating spore Antheridium HAPLOID n Mature DIPLOID 2n sporophyte Archegonial wall Sporophyte Root Horizontal stem LIFE THE SCIENCE OF BIOLOGY Suanlh Edition Figure 2920 The Life Cycle 01 a Fem 2004 5mm Assncmes me and w H Freeman 1 Ca Nontracheophytes 39 39 39 Z 0 common Club mosses W a ancestor g E 9 Horsetalls g b g Tracheids 0 branching Whisk ferns 1 8 H independent K3 7 3 m klt n sporophyte f d r Iquot l m g quotS Multi agellate n E sperm complex 7 lt 8 leaves k a g Comfers E o m 0 m 9 Seeds R 3 H a a m 839 o Gnetophytes Flowers carpels triploid endosperm Angiosperms LIFE THE SCIENCE OF BIOLOGY Savant Edition Figure 2WThe Evolulinn o1 Tnday39s Flams 2qu Smauer Assocmes me am w H Freeman 5 Co
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