Bis 2c Midterm 2
Haplontic (sexual) Life Cycle -expansion of what? -occurs in what groups?
- expansion of the haploid phase -fungi & some algae
How has multicellularity evolved in plants? in what lineages?
- it has evolved independently many times (homoplasia, convergent evolution) Lineages (evolved in all independently, except glaucophytes) -red algae -Chlorophytes -coleochates -charales -land plants
Overtopping Growth
-Apical meristem divides asymmetrically, such there is a main stem and side branches -seen in euphyllophytes
Sori
-Clusters of sporangia -often found on the underside of leptosporangiate fern leaves -circinate vernation~ unrolling fern http://youtu.be/GopfQp9genw -spore catapult ) http://youtu.be/GUfV17u8FlM
Variations of Sexual Ekaryotic Life Cycles
-Diplontic -Haplontic -Sporic (alt. of generations)
Innovations of seed plants (gametophyte/sporophyte) -explain the reduction of gametophyte stage -contrast to how it was for bryophytes (ex. moss) and seedless vascular plants (ex. ferns)
-In seed plants, the gametophyte generation is reduced even further than it is in ferns -The haploid gametophyte develops partly or entirely while attached to the sporophyte
Monilophytes: Leptosporangiate Ferns Characteristics (species numbers? What else?)
-Large group (~12,000 species) -Distinct form of sporangium, annulus, that contain few spores -Sporangia often born in clusters called sori -Typically frond-like leaves develop from fiddleheads
Innovations of vascular plants (Just effecting Lycophytes)
-Lateral sporangia in Lycophytes -sporophylls grouped into a cone (strobilus)
Stigmarian roots -in what lineage -What are they? -what did they derive from?
-Lycophytes -Simple dichotomously branching root system derived from rhizomes -Spirally arranged rootlets derived from microphyllous leaves
Innovations of Vascular plants (Euphyllophytes) -what is the innovation? adaptive values? (2)
-Overtopping growth -effects monilophytes and seed plants Adaptive values: 1. allows taller growth and enhanced competition for sunlight 2.allows elaboration of novel organs
Transpiration-Cohesion-Tension System
-Passive transport system that does not require energy from the plant ~water differential (water moves from wet to dry) -water diffuses from the inside of tissues (from xylem) to the outside (from the stoma/root hairs) and then evaporates at the exposed parts of leaves http://www.life10e.com/at35.02.html
How does the water flow in the xylem? -direction -process
-Roots to aerial parts of plant -Passive transport based on capillary actions
Monilophytes: Whisk ferns (Psilophytes) characteristics (3) -lost/reduced what things? Strange.. (Species numbers?Resembles what? Related to what group?)
-Small group (~15 species) -dichotomously branching stems -reduced leaves -lack roots (secondarily lost) -resemble rhiniophytes -sister to ophioglossales
Monilophytes: Horsetail Ferns (equisetophytes) characteristics (5)
-Small group (~15 species) -hollow, jointed stems -sporangia borne in terminal strobili on reproductive stems -reduced, scale-like leaves borne in a whorl at each node -basal meristem at base of each joint
Innovations of vascular plants (roots)
-Stigmarian roots -complex roots -exhibit homoplasia
Cuticle
-The cuticle is a non-cellular protective layer covering the outer cell layer (epidermis) of the green, aerial parts of land plants -Retards Water Loss
Seed ferns and the origin of seed plants
-The seed ferns were woody plants that bore seeds on their leaves Seed ferns arose in the Carboniferous (~360 Mya) -extinct
Embryophytes derived trait
-all land plants 1. protected embryo
Plantae
-all plants (aquatic+land) 1. primary-endosymbiotic chloroplast 2. cellulose cell wall 3. chlorophyll a
Spermatophytes derived trait
-all seed plants 1. seeds
Tracheophytes derived trait
-all vascular plants 1. tracheids (vascular cells)
What was terrestrial Earth like before land plants (~500mya)
-decreased atmospheric oxygen -increased atmospheric carbon dioxide -intense UV radiation -virtually devoid of life -dystopian hellscape!
Charales
1. A small group of species of primarily multicellular, aquatic organisms 2. Live in near-shore habitats 3. The sister group of Land plants
3 common plant "grades" (unnatural paraphyletic groupings)
1. Chlorphytes+Coleochates+Charales (CCC)= green algae 2. Liverworts+mosses+hornworts= bryophytes 3. Monilophytes= ferns
Challenges of life on land (3)
1. Desiccation 2. Gravity (a relatively non-supportive medium compared to water) 3. Dispersal of gametes (in water gametes are easily dispersed)
Advantages of life on land (3)
1. Easier to capture sunlight 2. Easier to exchange gasses (oxygen and CO2) 3. Initially lower competition for resources
Fertilization
fusion of egg and sperm to form a diploid zygote
Rhizoids
hair-like structures for water absorption not homologous to roots
Gametes
sexual haploid cells (typically eggs and sperm)
Viridiophytes derived trait
- all green plants 1. chlorophyll b
When did plants arise? When did land plants arise? How much time in bewteen?
- all plant MRCA: 1.2 BYA -land plants MRCA: 470 MYA -about 700MYA in between
Euphyllophytes derived trait
- all true-leaved plants 1. overtopping growth
Vascular-plant innovations exhibit homoplasy
- Many key traits have evolved independently multiple time is vascular plants ~leaves ~roots ~heterosporous life cycle -These homoplasious traits can complicate phylogeny estimation -But, independent evolution of such structures suggests their adaptive value independent solutions to common challenges of life on land
Rhiniophytes -what were their characteristics? (4) -adaptive values (2)
-early vascular plants -small (<5 cm) in height -relatively simple organisms ~lacked leaves, roots -*dichotomously branching sporophyte with apical sporangia -Rhyniophytes had single-celled hair like roots adaptive value: 1. increased spore production relative to unbranched counterparts 2. facilitated evolution of novel organ types
Complex roots -which group
-euphyllophytes -Complex branching root system derived from stems -Root hairs developed from dermis
Innovations of Vascular Plants (vascular system) -3 aspects that make up the vascular system innovation -2 adaptive values
-excludes rhiniophytes -tracheid cells and vascular tissue ~xylem ~phloem ~transpiration-cohesion system Adaptive values: 1.efficient transport of water and nutrients allows plants to colonize more fully terrestrial environments 2.rigid structural support allows plants to grow taller, and thus to compete more effectively for sunlight and also to enhance spore dispersal
Diplontic (sexual) Life Cycle -expansion of what? -what major lineage of euks does it occur in?
-expansion of the diploid phase -occurs in animals
Angiosperms
-flowering plants 1. flowers
Lycophytes: spike mosses
-heterosporous (convergent evolution)
Monilophytes: ophioglossales characteristics (2)
-megaphyllous leaves -sister group to whisk ferns
Innovations of Vascular plants (Leaves)
-microphyllous leaves -megaphyllous leaves -shows homoplasia with micro/megaphylls
Green algae grade
-non-land plants -chlorophyll b -starch as storage -paraphyletic (it's a grade) includes the main lineages: chlorophytes, coleochates, charales
Why are plants fundamental to life on earth?
-primary plants -everything you eat is (directly/indirectly) thanks to plants -Plants produce oxygen and scavenge CO2 -Plants are atmospheric terraformers -the source of wood for construction - a major source of clothing -the main source of electricity -the major source of natural gas and oil -keep us warm - the major source of pharmaceutical discoveries -largest,most massive, and oldest living organisms -super diverse in terms of: species numbers, ecology, and morphology
Lycophytes: Club Mosses
-sporophylls grouped into strobilus with lateral sporangia -homosporous
Lycophytes: quillworts
-used to great and diverse, but now its sad ): -still posses swollen "woody" base ~wood not by BVC, instead only the xylem grows, causing the outside (which doesnt grow) to crack
Progymnosperms and the origin of seed plants
-woody but lacked seeds -extinct
In what environment did plants arise? Where are most extant species of plants today?
1)Plants arose in an aquatic environment 2)Most living species of plants are terrestrial
What features are diagnostic of all plants?
1)Primary endosymbiosis of chloroplast 3)Chlorophyll a 2)Cellulose cell walls
Bryophyte grade -characteristics -rely on what? -main lineage
1. "Bryophytes" are the amphibians of Land Plants 2.lack true vascular system -water transport relies on capillary action -nutrient transport relies on diffusion 3.lack true leaves, stems, and roots 4.cuticle is poorly developed 5.largely rely on water for part of their life cycle -they have swimming sperm that require water for transport -limits dispersal and timing of mating 6.typical life cycle: -they have swimming sperm that require water for transport -sporophyte small and dependent on gametophyte -paraphyletic grade -includes liverworts, mosses, hornworts -there is uncertainty in bryophyte phylogenetic relationships
Chlorophytes
1. A group of ~17,000 mainly freshwater (some marine and terrestrial) unicellular and multicellular organisms 2.Diverse variety of forms: -rod shaped -blade shaped -colonial organization
Red algae
1. A group of ~6000 species of primarily multicellular, marine organisms, especially tropical waters 2. In addition to chlorophyll a, they possess accessory pigments called phycoerythrin 3.The prevalence of the pigments depends on the wavelength of light in which they occur 4. Store products of photosynthesis as floridean starch (very short 15 glucose monomer chains)
Liverworts -in what grade? -size of group? -what is the gametophyte called/how does it look? -How is the sporophyte? (3 things) -how do the sperm move to egg? -what do they have for -what is the structure for water absorption? -what structure do they have for asexual reproduction?
1. In bryophyte grade 2. Large group (~9000 species) of low-profile organisms -thallus-gametophyte (haploid generation) leafy, thalloid, or plate-like (untrue leaves, no vascular system to them) -sporophyte (diploid generation) shorter than other bryophytes: ~stock attached sporangium to foot ~stock extension via elongation of a finite number of cells ~sporangia are simple globular cell mass -(generally) swimming sperm 2. Have Rhizoids 3. Gaemmae cup http://youtu.be/ALGDLzWcvnU
Mosses (bryophytes) -size of group? -new attribute? -is there a vascular system? what kind, what cells make it up? -what are the sporangia like? -what is the gametophyte like? (what is and is not photosynthetic in it?)
1. Large group (~15,000 species) of mat-like organisms -possess stomata that regulate gas exchange -many mosses possess a simple vascular system (but not considered a vascular plant) ~hydroid cells facilitate water transport ~leptoid cells facilitate nutrient transport ~sporangia are simple globular cell mass -gametophyte (haploid generation) with leaf- and root-like organs (untrue roots, leaves) ~filamentous protonema ~non-photosynthetic cells rhyzoids ~photosynthetic cells stem and leaf-like organs 3. dead moss forms peat bogs that preserve things well
8 major clades of plants
1. Plantae 2. Viridiophytes 3.Streptophytes 4.Embryophytes 5. Tracheophytes 6. Euphyllophytes 7. Spermatophytes 8. Angiosperms
Lycophyte -main lineages (3) -gerneral characteristics
1. Quillworts ( Isoetes) 2. Spike mosses (Selaginella) 3. club mosses (Huperzia, Lycopodium) General Characteristics: -Small group (~1200 species) -lateral, kidney shaped sporangia -microphyllous leaves -stigmarian (dichotomous) roots
Glaucophytes
1. Small group (13 species) of mainly freshwater, unicellular organisms 2.Chloroplasts retain a vestigial cell layer (peptidoglycan) between its inner and outer layers
Hornworts
1. Small group (~100 species) of horned, low-profile organisms -possess stomata (stomates) that regulate gas exchange -**sporophyte is photosynthetic -**simple, thin gametophyte (a few cells thick) -cells with single large plate-like chloroplast -symbiotic fungal associations provide nutrients ~**sporangia exhibit basal meristematic growth
Innovations of Vascular Plants (sporophyte vs gametophyte)
1. The sporophyte is independent of the gametophyte at maturity (unlike w/ bryophytes) 2. Excludes rhiniophytes
Streptophytes derived traits
1. branched, apical growth 2. retention of egg
Xylem
1. conducts water and minerals from soil to aerial parts of the plant 2.secondary thickening of cell walls (lignin) provides structural support 3. tracheid cells are the principal water conducting element of the xylem and are dead at functional maturity (vessel elements and fiber cells only in gnetophytes and angiosperms)
Shared traits of homospory and heterospory (have what things in their 2 generations?)
1. gametophyte: haploid 'gamete plant' that produces gametes by mitosis in gametangia -gametangia: the multicellular organs of the gameteophyte that produces gametes -heterosporous don't have archegonium/antheridia like homosporous 2.Sporophyte: diploid 'spore plant' that produces spores by meiosis in sporangia -sporangia: the multicellular organs of the sporophyte that produces spores
3 Distinguishing Reproductive features of Land Plants
1. thick spore walls 2. gametangia 4. embryos
Three essential elements of the Sexual eukaryotic life cycle
1.Meiosis 2. Gametes 3. Fertilization
The role of vascular tissue in terrestrial plants
1.Water is needed -in leaves for photosynthesis -in leaves to replace water lost by evaporation 2.Sugar is needed -for metabolism anywhere it is not being produced 3.Two important functions of vascular tissue -transport of water and nutrients -structural support
Phloem
1.conducts products of photosynthesis from source to demand/storage areas in plant 2.comprised of sieve cells that are alive at functional maturity 3.they are nurtured by companion cells 4.nutrients are transported passively throughout the plant by osmosis -moved from sites of production (sources) -moved to sites of use or storage (sinks) e.g., growing tissues, storage organs
4 Distinguishing Vegetative features of Land Plants
1.cuticle 2.pores for gas exchange (stoma) 3. pigments for UV protection 4.mutualistic fungal associations
6 challenges of Life in a Terrestrial environment
1.desiccation 2.water transport 3.gas exchange 4.structural support 5.UV radiation 6.dispersal of gametes/progeny
What provides structural support in the xylem? how?
Lignin: a secondary thickening of cell walls in xylem
Leaves
A compressed photosynthetic structure emerging laterally from a stem or branch that possesses vascular tissue
Megaphyllous leaves
A larger, more complex leaf with ramified vascular tissue (e.g., Monilophytes and seed plants) ~more than one single vascular strand inside of photosynthetic structure
Microphyllous Leaves
A small simple leaf with a single vascular strand (e.g., Lycophytes) originated from sterile lateral sporangia
Innovations of Vascular Plants (Heterospory) -Advantages?
Advantages of Heterospory: 1.genetic diversity: separate, unisexual male and female gametophytes reduces the probability of self fertilization, which maintains genetic diversity in the population via outcrossing 2.Parental investment: separate, unisexual male and female sporangia may provide a means of parental investment in the next sporophyte generation (provisioning the megaspore & thus female gametophyte with nutrients) Adaptive Value: 1. retention of egg in archegonium provides protection for the zygote 2. protects spores from desiccation and facilitates transport by wind -very tough outter covering called sporopollenin
Multiflagellate Sperm -what lineages have this?
All of the plant groups we have discussed so far have diflagellate sperm Multiflagellate sperm has evolved independently in whisk ferns and seed plants
Considering moss and fern cycles: -A. Ferns have alternation of generations and mosses do not. B. Ferns have dominant sporophyte and mosses have dominant gametophytes. C. The embryo is retained on the parent in moss but not in fern. D. Ferns are diplontic, moss are haplontic E. Both (B) and (D)
Answer is B, ferns have dominant sporophyte while mosses have dominant gametophytes -both have alt. of generations life cycle -neither have haplontic of diplontic life cycles -embryo is retained in both
Definition of a plant
Autotrophic eukaryotic organisms capable of converting light energy into chemical energy (carbohydrates) via photosynthesis in the presence of chlorophyll inside organelles called chloroplasts (primary endosymbiosis)
Oogamy
Pair of structurally dissimilar gametes -female gamte=bigger, non motile -male gamete=small, many, motile
Annulus
Distinct form of sporangium found in Leptosporangiate ferns that contain few spores -Catapults spores
Differences in homospory and heterospory
Homoporous: -male and female gametangia may occur on each individual -Only one type of sporangium Heterosporous -male and female gametangia occur separately on the individual ~megagametophyte: produce female gametes (egg cells) ~microgametophyte: produce male gametes (sperm cells) -Two types of sporangia ~megasporangium: produces megaspores that become (female) megagametophyte ~microsporangium: produces microspores that become (male) microgametophyte
The grade of "seedless vascular plants" -includes what lineages?
Includes: Rhiniophytes, lycophytes, monilophytes -arose about 420 mya
The simplest possible Sexual eukaryotic life cycle -draw it, label the stages and processes. -How many cells in the stages
The haploid and diploid stages have only a single cell
Sources
Products of photosynthesis moved from sites of productions (ex. leaves) by osmosis via the phloem a companion cell
Sinks
Products of photosynthesis moved to sites of storage (ex. growing tissues, storage organs) by osmosis via the phloem a companion cells
Roots
Subterranean branching organs of land plants
Anatomy of a Seed
The seed is comprised of 3 main components: 1. Mature diploid embryo (baby plant) 2.Nutritive haploid tissue (to help support establishing plant) 3. Protective seed coat (from previous sporophyte)
Gemmae cup
a structures for asexual reproduction dispersal of bits of gametophyte plant http://youtu.be/ZlCtpTVg2is
How did plants possess a chloroplast?
Through a unique episode of primary endosymbiosis of a cyanobacterium (w/ the MRCA of plants)
What cells make up xylem? Phloem?
Xylem: Tracheids (dead at functional maturity) Phloem: Sieve cells, with the assistance of source and sink companion cells (alive at functional maturity)
Sporic (sexual) Life cycle/ Alternation of Generations -expansion of what? -what are the stages/ draw out with processes
expansion of both haploid and diploid phases Stages 1. The zygote undergoes mitoses to produce a multicellular diploid body 2. Specialized cells undergo meiosis to produce haploid spores 3. These spores germinate and divide repeatedly by mitosis to produce a multicellular haploid body 4. Specialized structures on the haploid body make gametes by mitosis 5. Because the multicellular diploid organism makes spores, it is called the sporophyte ("spore plant") 6. Because the multicellular haploid organism makes gametes, it is called the gametophyte ("gamete plant") 7. Because both the haploid and diploid cells go from a single cell to multicellular bodies, they are considered separate generations— plants have an alternation of generations between haploid and diploid generation.
Strobilus
is a structure present on many land plant species consisting of sporangia-bearing structures densely aggregated along a stem.
What type of group is plants? para, poly, monophyletic?
monophyletic
How many times has the tree form evolved in plants?
more than 200 times
Stoma (or stomate), pl. stomata
pores for gas exchange
Meiosis
reduces diploid cells to haploid cells
Closest relative to plants?
the sister group of the MRCA of fungi and animals
What cells make up the water and nutrient transport system of mosses in the bryophyte grade?
~hydroid cells facilitate water transport ~leptoid cells facilitate nutrient transport
