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AU / Biology / BIO 1030 / Systematics is what?

Systematics is what?

Systematics is what?


School: Auburn University
Department: Biology
Course: Organismal Biology
Professor: Debbie folkerts
Term: Summer 2015
Tags: Organismal Biology
Cost: 50
Name: BIOL 1030 Exam 1 Study Guide
Description: This is a comprehensive study guide of materials for Exam 1. It includes detailed notes from chapters 26, 27, 28, and 29 in our textbook.
Uploaded: 02/02/2016
14 Pages 31 Views 10 Unlocks

Bio Chapter 26

Systematics is what?

Sunday, January 31, 2016

8:55 PM

Chapter 26: Phylogeny and the Tree of Life

Investigating the Tree of Life

• Phylogeny -- the evolutionary history of a species or group of species

• Systematics -- a discipline focused on classifying organisms and determining their evolutionary  relationships

26.1 Phylogenies show evolutionary relationships

• Taxonomy -- how organisms are named and classified

Binomial Nomenclature

• Developed by Carolus Linnaeus

• Binomial -- two part, Latin, scientific name of an organism

o Composed of Genus + specific epithet

What is binomial?

Hierarchical Classification

• From smaller to larger:  

Genera -- families -- orders -- classes -- phyla -- kingdoms -- domains

• Taxon -- the named taxonomic unit at any level of the hierarchy

Linking Classification and Phylogeny

• Phylogenetic tree -- branching diagram that represents the evolutionary history of an organism • A phylogenetic tree represents a HYPOTHESIS about evolutionary relationships • Branch points -- divergence of two evolutionary lineages from a common ancestor • Sister taxa -- groups of organisms that share an immediate common ancestor and are each others  closest relatives

• Rooted phylogenetic tree -- a branch point within the tree represents the most recent common  ancestor of all the taxa in the tree

What is phylogenetic tree?

We also discuss several other topics like What is the function of sensory system?

• Basal taxon -- lineage that diverges early in the history of a group and lies on a branch that  originates near the common ancestor

• Polytomy -- branch point from which more than two descendant groups emerge What We Can and Cannot Learn From Phylogenetic Trees

• Trees show patterns of descent, not phenotypic similarity

• The sequence of branching in a tree does not necessarily indicate the actual ages of the particular  species

• We should not assume that a taxon on a phylogenetic tree evolved from the taxon next to it Applying Phylogenies

• Identifying closely related organisms allows us to establish a "reservoir" of beneficial alleles that  can be transferred to cultivated organisms by cross-breeding or genetic engineering • Infer species identities by analyzing the relatedness of DNA sequences from different organisms We also discuss several other topics like What is digitalization?

26.2 Phylogenies are inferred from morphological and molecular data Morphological and Molecular Homologies

• Phenotypic and genetic similarities due to shared ancestry = homologies Don't forget about the age old question of How are ecology and evolution related?

• Organisms that share very similar morphologies or similar DNA sequences are likely to be closely  related

Sorting Homology from Analogy

• Analogy -- similarity between organisms due to convergent evolution

• Convergent evolution is when similar environmental pressures and natural selection produce  similar adaptations in organisms from different evolutionary lineages

• Homoplasies -- analogous structures that arise independently

• The more elements that are similar in two complex structures, the more likely it is that they  evolved from a common ancestor

Evaluating Molecular Homologies

• If species are closely related, their DNA sequences probably differ at only one or a few sites Don't forget about the age old question of What is the capital city of libya?

26.3 Shared characters are used to construct phylogenetic trees Cladistics

• Cladistics -- common ancestry is the primary criterion used to classify organisms • Clades -- groups of species that include an ancestral species and all of its descendants • Monophyletic -- consists of an ancestral species and all of its descendants

• Paraphyletic -- consists of ancestral species and some, but not all, of its descendants • Polyphyletic -- includes distantly related species but does not include the most recent common  ancestor Don't forget about the age old question of What is the study of psychology?

Shared Ancestral and Shared Derived Characters

• Shared ancestral character -- a character that originated in an ancestor of the taxon • Shared derived character -- an evolutionary novelty unique to a particular clade Inferring Phylogenies Using Derived Characters We also discuss several other topics like What is the academic integrity?

• Outgroup -- a species or group of species from an evolutionary lineage that is known to have  diverged before the lineage that includes the species we are studying

o A suitable one can be determined based on evidence from morphology, paleontology,  embryonic development, and gene sequences

• Ingroup -- the species we are studying

• Derived characters can be determined by comparing members of the ingroup with each other and  with the outgroup

Phylogenetic Trees with Proportional Branch Lengths

• Branch lengths can be drawn to represent the numbers of changes that have taken place in a  particular DNA sequence in that lineage

• Branch lengths can be proportional to time

Maximum Parsimony and Maximum Likelihood

• Can never be sure of the most accurate tree for a large data set

• Maximum parsimony -- we should first investigate the simplest explanation that is consistent with  the facts; minimalist approach

• Maximum likelihood -- identifies the tree most likely to have produced a given set of DNA data,  based on certain probability rules about how DNA sequences change over time • When a large amount of data is accurate, these two methods yield similar trees Phylogenetic Trees as Hypotheses

• Phylogenetic bracketing allows us to predict that features shared by two groups of closely related  organisms are present in their common ancestor and all of its descendants unless independent  data indicate otherwise

26.4 An organism's evolutionary history is documented in its genome

• DNA sequences show phylogenetic relationships that cannot be determined by nonmolecular  methods

Gene Duplications and Gene Families

• Gene families -- groups of related genes within an organism's genome

• Gene duplication increases the number of genes in the genome, providing more opportunities for  further evolutionary changes

• Orthologous genes -- homology is the result of a speciation event and hence occurs between  genes found in different species

• Paralogous genes -- homology results from gene duplication -- multiple copies of these genes  have diverged from one another within a species; more than one copy in the genome Genome Evolution

• Lineages that diverged long ago often share many orthologous genes  

• The number of genes a species has doesn't seem to increase through duplication at the same rate  as perceived phenotypic complexity

26.5 Molecular clocks help track evolutionary time

Molecular Clocks

• Molecular clock -- an approach for measuring the absolute time of evolutionary change based on  the observation that some genes and other regions of genomes appear to evolve at constant rates o For orthologous genes: assume number of nucleotide substitutions proportional to the time  that has elapsed since the genes branched from their common ancestor

o For paralogous genes: assume number of substitutions proportional to the time since the  ancestral gene was duplicated

• Not always accurate because:

o Some portions of genome have evolved in irregular bursts

o Same gene may evolve at different rates in different groups of organisms

o The rate of the clock may vary greatly from one gene to another

Differences in Clock Speed

• If the mutated gene is one critical for survival, the mutation will be unfavorable and gene changes  will occur slowly. If the mutated gene is not critical fewer mutations will be harmful and changes  will occur more quickly

Potential Problems with Molecular Clocks

• Natural selection changes direction which can lead to averaging out of changes, allowing this to be  an approximate marker of elapsed time

• Estimates can be wrong because of the assumption that clocks have been constant for long  periods of time

• By studying genes of multiple taxa, outliers may average out

Applying a Molecular Clock: Dating the Origin of HIV

• HIV - 1M first spread to humans around 1910

26.6 Our understanding of the tree of life continues to change based on new data From Two Kingdoms to Three Domains

• 3 Domains: Bacteria, Eukarya, and Archaea

The Important Role of Horizontal Gene Transfer

• Comparisons of complete genomes from the three domains show that there have been substantial movements of genes between organisms in the different domains

• Horizontal gene transfer -- genes are transferred from one genome to another through  mechanisms such as exchange of transposable elements and plasmid, viral infection, and perhaps  fusion of organisms

Bio Chapter 27

Monday, February 1, 2016

12:27 AM

Chapter 27: Bacteria and Archaea

Masters of Adaptation

• Prokaryotes are the most abundant organisms on earth -- can adapt to a broad range of habitats

27.1 Structural and functional adaptations contribute to prokaryotic success • Most prokaryotes are unicellular, typically very small

Cell-Surface Structures

• Cell wall maintains shape, protects cell, prevents from bursting in hypotonic environment • Cell wall contains peptidoglycan -- polymer composed of modified sugars cross-linked by short  polypeptides

• Archaeal cell walls contain a variety of polysaccharides and proteins but lack peptidoglycan • Gram stain -- categorize bacterial species according to differences in cell wall composition o Gram positive -- simpler cell walls with large amount of peptidoglycan

o Gram negative -- less peptidoglycan and structurally more complex, outer membrane  contain lipopolysaccharides

• In medicine, gram negative more resistant than gram positive due to outer membrane • Antibiotics like penicillin inhibit the peptidoglycan cross-linking resulting in a nonfunctional cell  wall

• Capsule -- sticky layer of polysaccharide/protein surrounding cell wall that enables prokaryotes to  adhere to their substrate or to other individuals in a colony

• Endospore -- copy of original cells chromosome surrounded by a tough, multilayered structure;  very durable; can remain dormant but viable for centuries

• Fimbriae -- hairlike appendages that allow prokaryotes to stick to their substrate or one another;  shorter and more numerous than pili

• Pili -- appendages that pull two cells together prior to DNA transfer from one cell to the other Motility

• Taxis -- directed movement toward or away from a stimulus (chemotaxis: response to chemical,  phototaxis: light)

• Moving toward stimulus is positive taxis, moving away is negative

• Flagella = most common form of movement; flagella of the domains made up of different proteins  = analogous structures

Evolutionary Origins of Bacterial Flagella

• Only half of the proteins that comprise the motor, hook, and filament of flagella are necessary.  This suggests that the bacterial flagellum evolved as other proteins were added to an ancestral  secretory system

o Exaptation -- the process in which existing structures take on new functions through descent  with modification

Internal Organization of DNA

• Less DNA

• Most lack compartmentalization

• One circular chromosome with fewer proteins

• Nucleoid -- region of cytoplasm not enclosed by a membrane that contains the chromosome • Plasmids -- smaller rings of independently replicating DNA molecules, most carry only a few genes Reproduction

• Binary fission -- single prokaryotic cell divides into 2 cells

• They are small, they reproduce by binary fission, and they often have short generation times

27.2 Rapid reproduction, mutation, and genetic recombination promote genetic  diversity in prokaryotes

Rapid Reproduction and Mutation

• Most genetic variation in sexual populations results from the way existing alleles are arranged in  new combinations during meiosis and fertilization

• New mutations, through rare on a per gene basis, can increase genetic diversity quickly in a  species with short generation times and large populations

Genetic Recombination

• Genetic recombination -- the combining of DNA from two sources

• Horizontal gene transfer -- transfer of genes between organisms of different species Transformation and Transduction

• Transformation -- the genotype and possibly phenotype of a prokaryotic cell are altered by the  uptake of foreign DNA from its surroundings

• Transduction -- phages carry prokaryotic genes from one host cell to another Conjugation and Plasmids

• Conjugation -- DNA is transferred between two prokaryotic cells (usually of the same species) that  are temporarily joined

• In bacteria, the DNA transfer is always one way

• Pilus of donor cell attaches to recipient and retracts, pulling the two cells together. A temporary  mating bridge structure forms between the cells and DNA is transferred

• F factor -- 25 genes required for the production of a pili; (f for fertility)

The F Factor as a plasmid

• F plasmid -- cells containing this (F+ cells) function as DNA donors during conjugation. F are  recipients. Condition is transferrable

The F factor in the chromosome

• A cell with F factor built into its chromosome is and Hfr cell

• Hfr cells act as donor during conjugation with an F cell. DNA enters the cell and homologous  regions of the Hfr and F chromosome may align = segments of DNA are exchanged and recipient  becomes recombinant

R Plasmids and Antibiotic Resistance

• R-plasmids -- carry "resistance genes" which code for enzymes that specifically destroy or  otherwise hinder the effectiveness of certain antibiotics

27.3 Diverse nutritional and metabolic adaptations have evolved in prokaryotes • Phototrophs obtain energy from light

• Chemotrophs obtain energy from chemicals

• Autotrophs need only a carbon source

• Heterotrophs require at least one organic nutrient to make other organic compounds The Role of Oxygen in Metabolism

• Obligate aerobes -- must use oxygen for cellular respiration and cannot grow without it • Obligate anaerobes -- are poisoned by oxygen; some live exclusively by fermentation, others use  anaerobic respiration

• Anaerobic respiration -- extract chemical energy using substances other than oxygen • Facultative anaerobes -- use oxygen if it is present but can also carry out fermentation or  anaerobic respiration in an anaerobic environment

Nitrogen Metabolism

• Nitrogen is essential for production of amino acids and nucleic acids in all organisms • Nitrogen fixation -- conversion of atmospheric nitrogen to ammonia

• Nitrogen fixing prokaryotes can increase the nitrogen available to plants

Metabolic Cooperation

• Oxygen inactivates the enzymes involved in nitrogen fixation so one cell cannot do both at the  same time

• Heterocysts -- cells that carry out only nitrogen fixation; surrounded by a thick cell wall that  prevents the entry of oxygen

• Biofilms -- surface-coating colonies. Cells in biofilms secrete signaling molecules that recruit  nearby cells, causing the colonies to grow and produce polysaccharides and proteins that stick the  cells to the substrate

27.4 Prokaryotes have radiated into a diverse set of lineages

An Overview of Prokaryotic Diversity

• Metagenomics -- obtaining genetic genomes from environmental samples

• Due to horizontal gene transfer, significant portions of the genomes of many prokaryotes are  mosaics of genes imported from other species


• Includes every major mode of nutrition and metabolism


• Extremophiles -- live in extreme conditions

• Extreme halophiles -- live in highly salty environments

• Extreme thermophiles -- thrive in very hot environments

• Methanogens -- archaea that release methane as a by-product of their unique ways of obtaining  energy

27.5 Prokaryotes play crucial roles in the biosphere

Chemical Recycling

• Decomposers -- breakdown dead organisms as well as waste products and thereby unlock  supplies of carbon, nitrogen, and other elements

• Prokaryotes can convert some molecules to forms that can be taken up by other organisms Ecological Interactions

• Symbiosis -- an ecological relationship in which two species live in close contact with each other • Host -- the larger organism in a symbiotic relationship

• Symbiont-- the smaller organism in a symbiotic relationship

• Mutualism -- interaction in which both species benefit

• Commensalism -- one species benefits while the other is neither harmed nor benefitted • Parasitism -- ecological relationship in which a parasite eats the cell contents, tissues, or body  fluids of its host

• Pathogens -- parasites that cause disease

27.6 Prokaryotes have both beneficial and harmful impacts of humans Mutualistic Bacteria

• Bacteria aid human digestion and immunity

Pathogenic Bacteria

• Exotoxins -- proteins secreted by certain bacteria and other organisms

• Endotoxins -- lipopolysaccharide components of the outer membrane of gram-negative bacteria;  released only when the bacteria die and their cell walls break down

Bio Chapter 28

Monday, February 1, 2016

12:29 AM

Chapter 28: Protists

Living Small

• Protists -- mostly unicellular eukaryotes

28.1 Most eukaryotes a single-celled organisms

• Eukaryotes have membrane bound organelles

• Eukaryotes have a well developed cytoskeleton that provides structural support, enabling cells to  have asymmetrical form, change shape as the feed, move, or grow

Structural and Functional Diversity in Protists

• Most protists are unicellular but some are colonial and multicellular

• Cellular functions carried out by subcellular organelles

• Heterotrophs, photoautotrophs,  and mixotrophs

• Mixotrophs -- combine photosynthesis and heterotrophic nutrition

• All three sexual lifecycles

• Ongoing changes in our understanding of phylogeny in protists

Endosymbiosis in Eukaryotic Evolution

• Endosymbiosis -- a relationship between two species in which one organism lives inside the cell or  cells of another organism

• Mitochondria arose from an alpha proteobacterium which was engulfed by an archaeal cell that  may have evolved to have eukaryotic features

Plastid Evolution: A Closer Look

• Heterotrophic eukaryote acquired an additional endosymbiont -- a photosynthetic  cyanobacterium -- that then evolved into plastids = two lineages of photosynthetic protists (algae):  red algae and green algae

• Algae have a double membrane with transport proteins

• Secondary endosymbiosis -- algae were ingested in the food vacuoles of heterotrophic eukaryotes  and became endosymbionts themselves

28.2 Excavates include protists with modified mitochondria and protists with  unique flagella

• Excavata -- based on morphological studies of the cytoskeleton; some members have an  "excavated" feeding groove on one side of the cell body

o Ex. Diplomonads, parabasalids, and euglenozoans

Diplomonads and Parabasalids

• Lack plastids

• Highly modified mitochondiria

• Most are anaerobic

• Diplomonads -- have reduced mitochondria called mitosomes, lack functional electron transport  chains

o Ex. Giardia intestinalis

• Parabasalids -- have reduced mitochondria called hydrogenosomes, anaerobic - release Hydrogen  as a by-product

o Ex. Trichomonas vaginalis


• Euglenozoans -- includes predatory heterotrophs, photosynthetic autotrophs, mixotrophs, and  parasites; main feature: a rod with either a spiral or a crystalline structure inside each of their  flagella


• Kineotoplastids -- have a single, large mitochondrion that contains an organized mass of DNA  called a kinetoplast

• Feed on prokaryotes in freshwater, marine, and moist terrestrial ecosystems, species that  parasitize animals, plants, and other protists

o Ex. Trypanosoma -- sleeping sickness


• Euglenid -- has a pocket at one end of the cell from which one or two flagella emerge • Some are mixotrophs, others engulf prey by phagocytosis

28.3 The "SAR" clade is a highly diverse group of protists defined by DNA  similarities

• Based on whole-genome DNA sequences; includes stramenopiles, alveolates, and rhizarians • Stramenopiles and alveolates originated through secondary endosymbiosis Stramenopiles

• Stramenopiles -- photosynthetic; characteristic flagellum has numerous fine hairlike projections  paired with a shorter, smooth flagellum


• Diatoms -- unicellular algae with glass-like wall made of silicon dioxide embedded in an organic  matrix that provides protection from being crushed by predators

• Very abundant (evidence in diatomaceous earth of the fossil layer)

• During blooms, experience rapid population growth due to ample nutrients being available; they  living ones sink to the bottom and pump carbon to the ocean floor

Golden Algae

• Golden algae -- color due to yellow and brown carotenoids; biflagellated cells • freshwater

• All are photosynthetic, some are mixotrophs that use phagocytosis

• Most are unicellular

Brown Algae

• Brown algae -- largest and most complex; all multicellular; most marine

• Rootlike holdfast anchors the algae and stemlike stipe, which supports the leaflike blades • Adaptations that allow their main photosynthetic surfaces to be near the surface of the water Alternation of Generations

• Alternation of generations -- alternation of multicellular haploid and diploid forms • Diploid sporophyte produces haploid spores (zoospores) that move by flagella • Zoospores develop into haploid multicellular gametophytes which produce gametes • Union of two gametes (fertilization) results in a diploid zygote which grows and becomes a  multicellular sporophyte

• Heteromorphic -- sporophytes and gametophytes are structurally different • Isomorphic -- sporophytes and gametophytes look similar to each other although they differ in  chromosome number


• Alveolates -- have membrane enclosed sacs (alveoli) just under the plasma membrane Dinoflagellates

• Dinoflagellates -- cells reinforced by cellulose plates

• Two flagella located in grooves in the cellulose plates make them spin as they move • Some are purely heterotrophic, others are photosynthetic (phytoplankton), or mixotrophs • During a bloom, create red tide that turns the water red and produce toxins that kill fish Apicomplexans

• Apicomplexans -- almost all are parasites of animals that spread through host as tiny, infectious  cells called sporozoites

• Apex of cell contains complex of organelles for penetrating host tissues and cells • Not photosynthetic but some have a modified plastid

• Complex lifecycle requiring 2+ hosts (ex. Plasmodium -- malaria)


• Ciliates -- named for use of cilia to move and feed

• Most are predators

• Have two types of nuclei: tiny micronuclei and large macronuclei

• Conjugation -- a sexual process in which two individuals exchange haploid micronuclei but do not  reproduce = genetic diversity

• Reproduce asexually through binary fission

• Genes in macronucleus control functions of cell


• Amoebas -- move and feed through pseudopodia (extensions that extend and are anchored, then  cytoplasm streams into it = movement)


• Radiolarians -- have delicate, symmetrical internal skeletons made of silica • Mostly marine

• Psuedopodia radiate from central body

• Engulfs smaller microorganisms that become attached to the pseudopodia Forams

• Foraminiferans -- porous shell called tests made of single piece of organic material hardened by  calcium carbonate

• Marine and freshwater


• Cercozoams -- ameboid and flagellated protists that feed using threadlike pseudopodia • Marine, freshwater, and soil

• Most are heterotrophs

28.4 red algae and green algae are the closest relatives of land plants • Archaeplastida -- monophyletic group including red algae, green algae, and land plants.  o Descended from ancient protist that engulfed cyanobacterium

Red Algae

• Red algae -- red due to photosynthetic pigment phycoerythrin

• Most are multicellular

• Sexual reproduction -- commonly have alternation of generations

• Don’t have flagellated gametes -- water currents bring gametes together

Green Algae

• Green algae -- chloroplasts very similar to plants'

• Divided into two groups -- charophytes and chlorophytes

• Charophytes most closely related to land plants

• Chlorophytes -- larger size and greater complexity because

o Formation of colonies

o Formation of true multicellular bodies by cell division and differentiation

o Repeated division of nuclei with no cytoplasmic vision

28.5 Unikonts include protists that are closely related to fungi and animals • Unikonta -- includes animals, fungi, and some protists


• Amoebozoans -- includes many species of amoeba that have lobe or tube shaped pseudopodia  rather than threadlike pseudopodia

Slime Molds

• Produce fruiting bodies that aid in spore dispersal

• Plasmodial slime molds

o Brightly olored

o Form a mass called plasmodium  

o Unicellular mass of cytoplasm that is undivided by plasma membranes and contains many  nuclei -- "supercell" due to mitosis not followed by cytokinesis

o Plasmodium extends pseudopodia to engulf food particles by phagocytosis -- if habitat dries  up it differentiates into fruiting bodies for sexual reproduction

• Cellular slime molds

o When food is depleted cells aggregate but remain separated by their plasma membranes -- form an asexual fruiting body

o Cells forming stalk dry up but spores cells at top survive -- some cells have mutated so they  never go to the stalk but the stalk cells wont reproduce with them


• Lobe or tube shaped pseuodopodia

• Unicellular

• Most are heterotrophs


• Parasites

• E. histolytica is only pathogenic one -- causes dysentery


• Opisthokonts -- animals, fungi, and several groups of protists

28.6 Protists play key roles in ecological communities

• Most are aquatic

Symbiotic Protists

• Dinoflagellates are food providing symbiontic partners of coral polyps which build coral reefs • Protists in gut of termites that allow them to digest wood

Photosynthetic Protists

• Producers -- organisms that use energy from light (or inorganic chemicals) to convert carbon  dioxide to organic compounds

Bio Chapter 29

Monday, February 1, 2016

12:29 AM

Chapter 29: Plant Diversity I: How Plants Colonized Land The Greening of Earth

• Plants supply oxygen and food to terrestrial animals and create habitats for organisms by  stabilizing the soil

29.1 Land plants evolved from green algae

Morphological and Molecular Evidence

• Plants are multicellular, eukaryotic, photosynthetic autotrophs

• Plants have cell wall made of cellulose

• Have chloroplasts with chlorophyll a and b

• Similar to charophytes

o Rings of cellulose-synthesizing proteins in the plasma membrane

o Structure of flagellated sperm

o Formation of a phragmoplast (a group of microtubules between daughter nuclei of dividing  cells)

Adaptations Enabling the Move to Land

• Sporopollenin -- layer of durable polymer in charophytes that prevents exposed zygotes from  drying out

o Allow plants to grow out of water

Derived Traits of Plants

• Alternation of generations

• Multicellular, dependent embryos

• Walled spores produced in sporangia (produces the spores)

• Multicellular gametangia (where gametes are produced)

• Apical Meristems (produces cells that protect the plant)

• Cuticle -- covering of wax and other polymers that acts as waterproofing to prevent excess water  loss and protecting against microbial attack

• Stomata -- pores that allow the exchange of carbon dioxide and oxygen between the outside air  and the plant

The Origin and Diversification of Plants

• Vascular tissue -- cells joining into tubes that transport water and nutrients throughout the plant =  vascular plants

• Nonvascular plants often informally called bryophytes  

• Lycophytes -- club mosses and their realtives; seedless vascular

• Monilophytes  -- ferns and their relatives; seedless vascular

• Grade -- group of organisms that share key biological features; don’t necessarily share the same  ancestry

• Seed -- embryo packaged with a supply of nutrients inside a protective coat • Gymnosperms -- "naked seed" plants; seeds are not enclosed in chambers; conifers • Angiosperms -- all flowering plants; seeds develop inside chambers that originate within flowers

29.2 Mosses and other nonvascular plants have life cycles dominated by  gametophytes

• Liverworts -- phylum Hepatophyta

• Mosses -- phylum Bryophyta

• Hornwarts -- phylum Anthocerophyta

• Earliest lineages to have diverged from the common ancestor of land plants Bryophyte Gametophytes

• Haploid gametophytes are the dominant stage of the life cycle

• Protonema -- mass of green, branched, once-cell-thick filaments

• Protonema produces buds which has an apical meristem that generates gametophores (gamete  producing structure)

• A protonema + a gametophore = the body of a moss gametophyte

• Rhizoids -- long, tubular single cells (liverworts and hornworts) or filaments of cells (mosses) that  anchor the gametophytes

• Gametangia -- formed by gametophytes; produces gametes and is covered with protective tissue o Archegonium -- produce one egg

o Antheridium -- produce one sperm

• Bryophyte sperm need water to get to the egg = most live in moist environment • Many bryophytes can increase the number of individuals in a local area through various methods  of asexual reproduction

Bryophyte Sporophytes

• Cells contain plastids that are green and photosynthetic

• Cannot live independently -- attached to and dependent on gametophyte for sugars, amino acids,  minerals, and water

• Smallest of all plant sporophytes

• Consist of a foot, a seta, and a sporangium

o Foot -- embedded in the archegonium, absorbs nutrients from the gametophytes o Seta -- stalk, conducts these materials to the sporangium

o Sporangium/Capsule -- uses materials to produce spores by meiosis

• Peristome -- ring of interlocking tooth-like structure found on the upper part of the capsule. Open  under dry conditions, close under moist. Allow spores to be gradually discharged into the wind • Moss and hornwort sporophytes larger and more complex than liverwort

The Ecological and Economic Importance of Mosses

• Help retain nitrogen in bare sandy soil

• Harbor nitrogen fixing cyanobacteria increasing nitrogen availability

• absorb damaging levels of UV in deserts or higher altitudes

• Peat -- partially decayed organic material

o Can be used as fuel

o Can preserve corpses

o Carbon reservoirs stabilize atmospheric CO2 concentrations

29.3 Ferns and other seedless vascular plants were the first plants to grow tall Origins and Traits of Vascular Plants

• Branched sporophytes not dependent on gametophytes for nutrition

• Main traits that characterize living vascular plants: life cycles with dominant sporophytes,  transport in vascular tissues called Xylem and phloem, and well-developed roots and leaves,  including spore-bearing leaves called sporophylls

Life Cycles with Dominant Sporophytes

• Sporophytes are larger and more complex than gametophytes

Transport in Xylem and Phloem

• Xylem: conducts most of the water and minerals

• Tracheids -- tube shaped cells in the xylem that carry water and minerals up from the roots • Lignin -- polymer that strenthens the cell walls of water-conducting cells in vascular plants • Phloem -- tissue that has cells arranged into tubes that distribute sugars, amino acids, and other  organic products

• Lignin helped plants grow taller

• Taller plants outcompete shorter one for sunlight and their spores disperse farther Evolution of Roots

• Roots -- organs that absorb water and nutrient from the soil & anchor vascular plants • May have evolved from lower portion of the stem

Evolution of Leaves

• Leaves -- increase the surface area of the plant body and are the primary photosynthetic organ of  vascular plants

o Microphylls -- small spine-shaped leaves supported by a single strand of vascular tissure;  lycophytes only

o Megaphylss -- leaves with highly branched vascular system

Sporophylls and Spore Variations

• Sporophylls -- modified leaves that bear sporangia

• Sori -- clusters of sporangia produced by fern sporophylls

• Strobili -- groups of sporophylls forming a cone-like structure in many lycophytes and most  gymnosperms

• Homosporous -- one type of sporangium that produces one type of spore that typically grows into  a bisexual gametophyte; most seedless vascular plant species

• Heterosporous -- has two types of sporangia and produces two kinds of spores • Megaspores -- develop into female gametophytes; produced by megasporangia on  megasporophylls  

• Microspores -- develop into male gametophytes

Classification of Seedless Vascular Plants

Phylum Lycophyta: Club Mosses, Spike Mosses, and Quillworts

• Most ancient group of vascular plants

Phylum Monilophyta: Ferns, Horsetails, and Whisk Ferns and Relatives • Most widespread seedless, vascular plants

• Megaphyll leaves and roots that can branch at various points

• Equisetum = horsetails; found in marshy places and along streams • Psilotum and Tmesipteris = whiskferns; only vascular plants lacking true roots The Significance of Seedless Vascular Plants

• Contributed to large reduction in carbon dioxide levels during the carboniferous period • Seedless vascular plants forming the first forests eventually became coal

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