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biology 2 uf

biology 2 uf

Description

School: University of Florida
Department: Biological Sciences
Course: Integrated Principles of Biology 2
Professor: Norman douglas
Term: Fall 2016
Tags:
Cost: 25
Name: BSC2011 Exam 1 Week 2 Notes
Description: These notes cover what was gone over in class during the second week.
Uploaded: 01/15/2017
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What adaptations would enable plants to successfully move from an aquatic environment to a terrestrial environment?




What are the sister group relationships among land plants?




What adaptations would enable plants to successfully move from an aquatic environment to a terrestrial environment?



BSC2011 Spring Semester 2017 Class Notes 09 January 2017 Endosymbiosis and the diversity of photosynthetic organisms Carl Woese and the three Domains of Life- discovered Archaea using phylogenetic analysis of ribosomal RNA ● Three Domains of life discovered: ○ Eukaryota ○ Eubacteria ○ Archaea 2015: Archaea is not monophyletic, and Lokiarchaeota are sister to Eukaryotes 2016: Latest data reveal that three domains may not be adequate to explain life’s diversity ● Eukaryotes closest relative is the prokarya ● We evolved from them ● The domain system is already outdated, more than 3 domains of life Phylogeny can help us to pinpoint key innovations= adaptations that are linked to diversification of a group Photosynthesis and the phylogeny of life ● All three domains contain photosynthetic organisms “Photoheterotrophs” ● Organisms that use sunlight to generate ATP, but do not obtain carbon from CO2 and do not generate O2 ○ Don’t go through the carbon fixation process so there is also not an oxygen producing step ○ Some bacteria, e.g. purple non-sulfur bacteria, and some Archaea, e.g. halobacteria Halobacteria ● Bacteriorhodopsin (red pigment) used to change light energy into chemical energy 1● Trap seawater and then when water evaporates, only salt is left and they collect it ○ Use an evaporation pond to do so ○ Salt becomes more concentrated and Halobacteria are able to thrive in this environment ○ Their photosynthetic pigment is the red pigment “Photoautotrophs” ● Organisms that use light to generate ATP for the purpose of carbon fixation- turning CO2 into glucose- AND generate O2 ○ Ex: Plants, Cyanobacteria, and Algae ○ Cyanobacteria is important historically as the original source of photosynthesis in eukaryotes Photosynthesis was around before eukaryotes evolved ● Their fossils look like modern organisms of Cyanobacteria Ancient stromatolite fossils contain cyanobacteria as old as 3.7 billion years ● Layered structure of cyanobacteria and calcium layered sediment ● Ancient pieces in the center and newer pieces near the outside Oxygenic photosynthesis drastically influenced the course of evolutionary history on earth ● Forced a new pathway for evolution ● Oxygen rich atmosphere favored organisms that could withstand and utilize oxygen ● Set the state for the rise and diversification of the eukaryotes ○ Theory of endosymbiosis (Lynn Margulis): We have different organisms that came together in a mutualistic relationship that created the first eukaryotic cells Endosymbiosis (Know it happened, just don’t know how): 1. Start with two independent bacteria 2. One bacterium engulfs the other a. Instead of digesting it, it remains inside alive 3. One bacterium now lives inside the other 4. Both bacteria benefit from the arrangement 5. The internal bacteria are passed on from generation to generation a. Can coordinate their reproductive efforts b. Can persist over time if it's beneficial for survival for both c. Then is subjected to it's own selective pressure Evolution of mitochondria by endosymbiosis 2● Free bacterial cells that used ATP ● There are two membranes Evolution of chloroplasts by endosymbiosis Primary endosymbiosis produced the first photosynthetic eukaryotes ● Primary endosymbiosis​: a cyanobacterium was engulfed. ● Chloroplast has two membranes ● This captured cyanobacterial cell gave rise to red algae, green algae, and land plants Endosymbiotic events in the Evolution of Chloroplasts ● Assimilation: many of the cyanobacterial genes have been transferred to the host nucleus over evolutionary time Eukaryote phylogeny and primary endosymbiosis ● Red algae, “green algae,” and the land plants Red algae ● Chloroplasts contain: Chlorophyll a ● Phycoerythrin- gives red algae their red color Synapomorphies of the green plants: starch storage and Chlorophyll b 3Ulva (green algae)- picture to the right Volvox ● Individual cells that form spheres ● Smaller colonies inside the main sphere Spirogyra ● Chloroplasts join in helical patterns so look like green shiny beads in a string Charophytes ● Chara ○ Apical growth ○ Not sister to land plants ● Coleochaete sp. ○ Parenchyma tissue Secondary endosymbiosis​: a eukaryote engulfed a eukaryotic algal (i.e., red or green algal) cell which became a chloroplast ● In these organisms, the chloroplasts have three membranes ● Engulf an organisms that already had a chloroplast in it Endosymbiotic Events in the Evolution of Chloroplasts (picture to the right) Euglena (green algal endosymbionts) ● Single cell organisms that has a flagellum that it uses to move forward ● Related to other organisms that don't photosynthesize ● Can do either: eat or photosynthesize (make it's own food) ● Chloroplasts derived from a green algal cell 4Stramenopiles-red algae endosymbionts ● Diatoms ● Cells in glass boxes ● Boxes fall to the bottom of the earth and can be used as insecticides that can kill soft bodied insects ● Also used in pool filters ● Also a supplement Stramenopiles-Brown Algae ● Fucus (left picture) ● Postelsia palmaeformis (right picture) A kelp forest- some brown algae can each be up to 30 meters in length ● important habitat for fish ● sometimes they float or ar anchored Secondary and Tertiary endosymbiosis: Dinoflagellates ● Secondary: Dinoflagellates have remnants of an early capture of a red alga, all of whose genes have been transferred to the nucleus (complete assimilation - no separate chloroplast). Still produce characteristic and algal pigments ● Tertiary: Also have proper chloroplasts that are derived from brown algae ● Have photosynthesis from two different sources ● “Supervillains” ● Plated with carbon armour and have two flagella: one they wear as a belt to move that way and one at the bottom to move in that direction ● Gonyaulax contamines shellfish with toxic compounds that can cause respiratory failure in humans ● Produce toxic compounds to burrow into flesh of fish ● Pfiesteria causes lesions on fish and humans, excretes toxic gas ● Dinoflagellate Gymnodinium causes red tide fish kills ● Create bioluminescence in the water when disturbed ● Zooxanthellae- Dinoflagellates who live inside of coral (right picture) Healthy vs. “bleached” coral ● Bleaching associated with climate change and water temp rising, Dinoflagellates are kicked out 11 January 2017 5Invasion of the land; mosses and liverworts Do the “Green algae” form a monophyletic group? ● No because left out the land plants (left out descendants of same ancestry) Plasmodesmata ● Basic plant tissue with cells linked by plasmodesmata= parenchyma ● Cells that communicate with each other as one organism ● PLasmodesmata build cell wall ● Cells of cytoplasm that are tubes in cell wall and connect the cell so they can communicate with one another or communicate with cells that are far away Land Plants or Embryophytes ● There are 11 major clades of land plants Tiktaalik ● Extinct vertebrae ● It represents a transitional fossil when animals made transition to animals, specifically vertebrates ● Looks like a fish ● Instead of fish-like pectoral fin, it had bones in pectoral fin that are like a foot ● Had eyes that were in a slightly different place ● Had ability to move it's head independently of its body (which fish don't usually do, but land animals do) ● Needed something to get oxygen with What adaptations would enable plants to successfully move from an aquatic environment to a terrestrial environment? 6Cuticle ​to withstand water loss ● Waxy cuticle that is a sealant Stomata ​for gas exchange in air while minimizing water loss Unique accessory pigments​ to endure high light ● Light is absorbed (blue lines) or dissipated (orange lines) by accessory pigments ● Can reflect some of the light back out ● Can also act like antennae when there is a small amount of light to get more light Sporopollenin​ for protection and dispersal of spores in air ● Instead of moving in water must move in air (flagella not useful anymore) ● Need same kind of protection that plant has when moving in water ● And if could last a while would be better, aka Sporopollenin ● Resistant to drying out, radiation, and decay ● Resistant to decay because there are so many kinds of bonds that there are very few organisms that can break up all those bonds Gametangia: Archegonium ​(produces and protects the egg) and Antheridium​ (produces and protects the sperm) ● Egg (Produced by mitosis, as are the sperm) Protected and nourished embryo ● Land plants are also called EMBRYOPHYTES ● Embryo still in maternal tissue ● There are placental transfer cells that provide nutrients Mycorrhizae (fungus root) ● Symbiotic associations with fungi ● Plants and fungi invaded land at the same time ● Spored are thought to come from the Glomalin fungus ● Associated with land plants by growing inside of the plant cells ● Coat the outside of roots and fungal body with penetrate the root and start to proliferate within the cell ● Fungus provides extra nutrients to the plant and in exchange the plant provides the fungus with sugar ● Completely dependent on the association with plants, would die without them ● Plants can also not grow well without them so want more of them What are the sister group relationships among land plants? 7● Green algae ● Liverworts ● Moses ● Tracheophytes All referred to as “Bryophytes” ● Hornworts Currently supported sister group relationships between bryophytes and vascular plants ● Among these lineages, all possess stomata EXCEPT liverworts How do these hypothesis affect a parsimonious interpretation of the evolution of stomata? ● Under hypothesis A, B, and C, we interpret a single evolutionary origin of stomata, while under hypothesis D and E we would interpret more than one evolutionary origin of stomata “Bryophytes”: Liverworts, Mosses, and Hornworts ● Not monophyletic ● All lack vascular tissue ● Absorb water and minerals directly though the plant surface through diffusion/osmosis ● Unique genes for desiccation tolerance- many species can survive nearly complete drying for long periods of time (surpassing desiccation tolerance in other plants). ● Reproduce using spores Spores germinate to form an immature gametophyte ● Bud on protonema ○ What it will look it ● Leafy stem on protonema ○ Grow around the moss Parts of a liverwort ● Gametophyte ○ Green, synthetic tissue ● Sporophytes ○ Produce capsules ● Seta: where attaches at the stalk 8● Capsule produces spores Liverworts gametophytes can be flattened (right picture), thalloid, or “leafy” (left picture) ● Have sacs that retain water Liverworts rhizoids anchor them to where they grow ● Function like roots but don’t absorb anything Liverworts sporophytes usually split unto valves to release spores and elaters ● Elaters can sometimes be released with spores ○ Have spiral cellulose thickenings ○ Have ability to expand and retract with the moisture in the air which helps spores to be released into the air Some thalloid liverworts gametophytes have air pores and produce asexual gemmae in gemma cups ● Some thalloid liverworts have special umbrella-like structures for antheridia and archegonia production Many leafy liverworts and some thalloid liverworts produce gemmae along the margins of the gametophyte ● Leafy liverworts and some thalloid liverworts produce archegonia in a perianth Desert-dwelling thallose liverworts dry down and shut down metabolism during drought ● Unfurl when there is rain again Parts of a moss ● Gametophyte ● Sporophyte ○ Has capsule where spores are made ○ Capsule is elongated and has a cap that comes off and inside of it is a structure called the peristome and that is where the spores are released ● Peristome- teeth that surround the mouth of the capsule through which spores are released Sphagnum (peat mosses) 9● Leaves in compact branches ● Can have colorful pigments ● Their sporophytes look like liverwort sporophytes instead of moss ones ● Open, dead cells used for water absorption and storage ● Leaf cells have holes in them, no membrane ○ They collect water, absorptive cells ○ Grow in places that accumulate water ● Have tendency to decrease pH of the water they are growing in ● Living cells at the tip and at the bottom it is dead Peat bogs- low decomposition rate leads to carbon accumulation ● Peat = dead portion of Sphagnum biomass ● Peatlands are major storage banks for global carbon Sphagnum ● Can burn it and use it as a fuel source ● Also used as an absorbing component for things like bandages and diapers Hornworts ● Very small and usually don’t have horns ● Have symbiosis with cyanobacterial colonies ○ Cavities for these colonies to grow ○ These colonies benefit hornworts because they do nitrogen fixation ○ Get fertilization from them 13 January 2017 Alternation of generations life cycle Human life cycle ● We’re diploid individuals Alternation of Generations ● This life cycle is a synapomorphy of the land plant clade, especially the presence of a sporophyte ● Includes two different life stages (generations) which alternate: ○ A multicellular diploid stage (the Sporophyte​) and a multicellular haploid stage (the gametophyte​) ● Gametes are produced by mitosis, ​spores​ are produced by meiosis Alternation of generations: 10● The multicellular haploid stage (gametophyte​) produces gametes​ by mitosis within the gametangia​ (antheridia and archegonia). ● After fertilization, the diploid zygote grows and develops into a multicellular embryo, which eventually grows and develops into a mature diploid plant (sporophyte​) ● The sporophyte​ forms spore-producing sporangia​ (singular: sporangium) ● Spores​ are produced inside the sporangium by meiosis ● Spores are released from the sporangium into the air, and eventually settle, grow, and develop into gametophytes Moss life cycle: ● Egg produced in the archegonium that is fertilized by sperm from the antheridium ● New zygote will be nourished my maternal tissue ● Sporophyte is attached to the gametophyte because of early transfer from maternal tissue to embryonic tissue ● Sporophyte has sporangium that releases the spores that are released ● They then germinate and turn into a gametophyte ● Haploid adult does most of the stuff for the plant 11BSC2011 Spring Semester 2017 Class Notes 09 January 2017 Endosymbiosis and the diversity of photosynthetic organisms Carl Woese and the three Domains of Life- discovered Archaea using phylogenetic analysis of ribosomal RNA ● Three Domains of life discovered: ○ Eukaryota ○ Eubacteria ○ Archaea 2015: Archaea is not monophyletic, and Lokiarchaeota are sister to Eukaryotes 2016: Latest data reveal that three domains may not be adequate to explain life’s diversity ● Eukaryotes closest relative is the prokarya ● We evolved from them ● The domain system is already outdated, more than 3 domains of life Phylogeny can help us to pinpoint key innovations= adaptations that are linked to diversification of a group Photosynthesis and the phylogeny of life ● All three domains contain photosynthetic organisms “Photoheterotrophs” ● Organisms that use sunlight to generate ATP, but do not obtain carbon from CO2 and do not generate O2 ○ Don’t go through the carbon fixation process so there is also not an oxygen producing step ○ Some bacteria, e.g. purple non-sulfur bacteria, and some Archaea, e.g. halobacteria Halobacteria ● Bacteriorhodopsin (red pigment) used to change light energy into chemical energy 1● Trap seawater and then when water evaporates, only salt is left and they collect it ○ Use an evaporation pond to do so ○ Salt becomes more concentrated and Halobacteria are able to thrive in this environment ○ Their photosynthetic pigment is the red pigment “Photoautotrophs” ● Organisms that use light to generate ATP for the purpose of carbon fixation- turning CO2 into glucose- AND generate O2 ○ Ex: Plants, Cyanobacteria, and Algae ○ Cyanobacteria is important historically as the original source of photosynthesis in eukaryotes Photosynthesis was around before eukaryotes evolved ● Their fossils look like modern organisms of Cyanobacteria Ancient stromatolite fossils contain cyanobacteria as old as 3.7 billion years ● Layered structure of cyanobacteria and calcium layered sediment ● Ancient pieces in the center and newer pieces near the outside Oxygenic photosynthesis drastically influenced the course of evolutionary history on earth ● Forced a new pathway for evolution ● Oxygen rich atmosphere favored organisms that could withstand and utilize oxygen ● Set the state for the rise and diversification of the eukaryotes ○ Theory of endosymbiosis (Lynn Margulis): We have different organisms that came together in a mutualistic relationship that created the first eukaryotic cells Endosymbiosis (Know it happened, just don’t know how): 1. Start with two independent bacteria 2. One bacterium engulfs the other a. Instead of digesting it, it remains inside alive 3. One bacterium now lives inside the other 4. Both bacteria benefit from the arrangement 5. The internal bacteria are passed on from generation to generation a. Can coordinate their reproductive efforts b. Can persist over time if it's beneficial for survival for both c. Then is subjected to it's own selective pressure Evolution of mitochondria by endosymbiosis 2● Free bacterial cells that used ATP ● There are two membranes Evolution of chloroplasts by endosymbiosis Primary endosymbiosis produced the first photosynthetic eukaryotes ● Primary endosymbiosis​: a cyanobacterium was engulfed. ● Chloroplast has two membranes ● This captured cyanobacterial cell gave rise to red algae, green algae, and land plants Endosymbiotic events in the Evolution of Chloroplasts ● Assimilation: many of the cyanobacterial genes have been transferred to the host nucleus over evolutionary time Eukaryote phylogeny and primary endosymbiosis ● Red algae, “green algae,” and the land plants Red algae ● Chloroplasts contain: Chlorophyll a ● Phycoerythrin- gives red algae their red color Synapomorphies of the green plants: starch storage and Chlorophyll b 3Ulva (green algae)- picture to the right Volvox ● Individual cells that form spheres ● Smaller colonies inside the main sphere Spirogyra ● Chloroplasts join in helical patterns so look like green shiny beads in a string Charophytes ● Chara ○ Apical growth ○ Not sister to land plants ● Coleochaete sp. ○ Parenchyma tissue Secondary endosymbiosis​: a eukaryote engulfed a eukaryotic algal (i.e., red or green algal) cell which became a chloroplast ● In these organisms, the chloroplasts have three membranes ● Engulf an organisms that already had a chloroplast in it Endosymbiotic Events in the Evolution of Chloroplasts (picture to the right) Euglena (green algal endosymbionts) ● Single cell organisms that has a flagellum that it uses to move forward ● Related to other organisms that don't photosynthesize ● Can do either: eat or photosynthesize (make it's own food) ● Chloroplasts derived from a green algal cell 4Stramenopiles-red algae endosymbionts ● Diatoms ● Cells in glass boxes ● Boxes fall to the bottom of the earth and can be used as insecticides that can kill soft bodied insects ● Also used in pool filters ● Also a supplement Stramenopiles-Brown Algae ● Fucus (left picture) ● Postelsia palmaeformis (right picture) A kelp forest- some brown algae can each be up to 30 meters in length ● important habitat for fish ● sometimes they float or ar anchored Secondary and Tertiary endosymbiosis: Dinoflagellates ● Secondary: Dinoflagellates have remnants of an early capture of a red alga, all of whose genes have been transferred to the nucleus (complete assimilation - no separate chloroplast). Still produce characteristic and algal pigments ● Tertiary: Also have proper chloroplasts that are derived from brown algae ● Have photosynthesis from two different sources ● “Supervillains” ● Plated with carbon armour and have two flagella: one they wear as a belt to move that way and one at the bottom to move in that direction ● Gonyaulax contamines shellfish with toxic compounds that can cause respiratory failure in humans ● Produce toxic compounds to burrow into flesh of fish ● Pfiesteria causes lesions on fish and humans, excretes toxic gas ● Dinoflagellate Gymnodinium causes red tide fish kills ● Create bioluminescence in the water when disturbed ● Zooxanthellae- Dinoflagellates who live inside of coral (right picture) Healthy vs. “bleached” coral ● Bleaching associated with climate change and water temp rising, Dinoflagellates are kicked out 11 January 2017 5Invasion of the land; mosses and liverworts Do the “Green algae” form a monophyletic group? ● No because left out the land plants (left out descendants of same ancestry) Plasmodesmata ● Basic plant tissue with cells linked by plasmodesmata= parenchyma ● Cells that communicate with each other as one organism ● PLasmodesmata build cell wall ● Cells of cytoplasm that are tubes in cell wall and connect the cell so they can communicate with one another or communicate with cells that are far away Land Plants or Embryophytes ● There are 11 major clades of land plants Tiktaalik ● Extinct vertebrae ● It represents a transitional fossil when animals made transition to animals, specifically vertebrates ● Looks like a fish ● Instead of fish-like pectoral fin, it had bones in pectoral fin that are like a foot ● Had eyes that were in a slightly different place ● Had ability to move it's head independently of its body (which fish don't usually do, but land animals do) ● Needed something to get oxygen with What adaptations would enable plants to successfully move from an aquatic environment to a terrestrial environment? 6Cuticle ​to withstand water loss ● Waxy cuticle that is a sealant Stomata ​for gas exchange in air while minimizing water loss Unique accessory pigments​ to endure high light ● Light is absorbed (blue lines) or dissipated (orange lines) by accessory pigments ● Can reflect some of the light back out ● Can also act like antennae when there is a small amount of light to get more light Sporopollenin​ for protection and dispersal of spores in air ● Instead of moving in water must move in air (flagella not useful anymore) ● Need same kind of protection that plant has when moving in water ● And if could last a while would be better, aka Sporopollenin ● Resistant to drying out, radiation, and decay ● Resistant to decay because there are so many kinds of bonds that there are very few organisms that can break up all those bonds Gametangia: Archegonium ​(produces and protects the egg) and Antheridium​ (produces and protects the sperm) ● Egg (Produced by mitosis, as are the sperm) Protected and nourished embryo ● Land plants are also called EMBRYOPHYTES ● Embryo still in maternal tissue ● There are placental transfer cells that provide nutrients Mycorrhizae (fungus root) ● Symbiotic associations with fungi ● Plants and fungi invaded land at the same time ● Spored are thought to come from the Glomalin fungus ● Associated with land plants by growing inside of the plant cells ● Coat the outside of roots and fungal body with penetrate the root and start to proliferate within the cell ● Fungus provides extra nutrients to the plant and in exchange the plant provides the fungus with sugar ● Completely dependent on the association with plants, would die without them ● Plants can also not grow well without them so want more of them What are the sister group relationships among land plants? 7● Green algae ● Liverworts ● Moses ● Tracheophytes All referred to as “Bryophytes” ● Hornworts Currently supported sister group relationships between bryophytes and vascular plants ● Among these lineages, all possess stomata EXCEPT liverworts How do these hypothesis affect a parsimonious interpretation of the evolution of stomata? ● Under hypothesis A, B, and C, we interpret a single evolutionary origin of stomata, while under hypothesis D and E we would interpret more than one evolutionary origin of stomata “Bryophytes”: Liverworts, Mosses, and Hornworts ● Not monophyletic ● All lack vascular tissue ● Absorb water and minerals directly though the plant surface through diffusion/osmosis ● Unique genes for desiccation tolerance- many species can survive nearly complete drying for long periods of time (surpassing desiccation tolerance in other plants). ● Reproduce using spores Spores germinate to form an immature gametophyte ● Bud on protonema ○ What it will look it ● Leafy stem on protonema ○ Grow around the moss Parts of a liverwort ● Gametophyte ○ Green, synthetic tissue ● Sporophytes ○ Produce capsules ● Seta: where attaches at the stalk 8● Capsule produces spores Liverworts gametophytes can be flattened (right picture), thalloid, or “leafy” (left picture) ● Have sacs that retain water Liverworts rhizoids anchor them to where they grow ● Function like roots but don’t absorb anything Liverworts sporophytes usually split unto valves to release spores and elaters ● Elaters can sometimes be released with spores ○ Have spiral cellulose thickenings ○ Have ability to expand and retract with the moisture in the air which helps spores to be released into the air Some thalloid liverworts gametophytes have air pores and produce asexual gemmae in gemma cups ● Some thalloid liverworts have special umbrella-like structures for antheridia and archegonia production Many leafy liverworts and some thalloid liverworts produce gemmae along the margins of the gametophyte ● Leafy liverworts and some thalloid liverworts produce archegonia in a perianth Desert-dwelling thallose liverworts dry down and shut down metabolism during drought ● Unfurl when there is rain again Parts of a moss ● Gametophyte ● Sporophyte ○ Has capsule where spores are made ○ Capsule is elongated and has a cap that comes off and inside of it is a structure called the peristome and that is where the spores are released ● Peristome- teeth that surround the mouth of the capsule through which spores are released Sphagnum (peat mosses) 9● Leaves in compact branches ● Can have colorful pigments ● Their sporophytes look like liverwort sporophytes instead of moss ones ● Open, dead cells used for water absorption and storage ● Leaf cells have holes in them, no membrane ○ They collect water, absorptive cells ○ Grow in places that accumulate water ● Have tendency to decrease pH of the water they are growing in ● Living cells at the tip and at the bottom it is dead Peat bogs- low decomposition rate leads to carbon accumulation ● Peat = dead portion of Sphagnum biomass ● Peatlands are major storage banks for global carbon Sphagnum ● Can burn it and use it as a fuel source ● Also used as an absorbing component for things like bandages and diapers Hornworts ● Very small and usually don’t have horns ● Have symbiosis with cyanobacterial colonies ○ Cavities for these colonies to grow ○ These colonies benefit hornworts because they do nitrogen fixation ○ Get fertilization from them 13 January 2017 Alternation of generations life cycle Human life cycle ● We’re diploid individuals Alternation of Generations ● This life cycle is a synapomorphy of the land plant clade, especially the presence of a sporophyte ● Includes two different life stages (generations) which alternate: ○ A multicellular diploid stage (the Sporophyte​) and a multicellular haploid stage (the gametophyte​) ● Gametes are produced by mitosis, ​spores​ are produced by meiosis Alternation of generations: 10● The multicellular haploid stage (gametophyte​) produces gametes​ by mitosis within the gametangia​ (antheridia and archegonia). ● After fertilization, the diploid zygote grows and develops into a multicellular embryo, which eventually grows and develops into a mature diploid plant (sporophyte​) ● The sporophyte​ forms spore-producing sporangia​ (singular: sporangium) ● Spores​ are produced inside the sporangium by meiosis ● Spores are released from the sporangium into the air, and eventually settle, grow, and develop into gametophytes Moss life cycle: ● Egg produced in the archegonium that is fertilized by sperm from the antheridium ● New zygote will be nourished my maternal tissue ● Sporophyte is attached to the gametophyte because of early transfer from maternal tissue to embryonic tissue ● Sporophyte has sporangium that releases the spores that are released ● They then germinate and turn into a gametophyte ● Haploid adult does most of the stuff for the plant 11

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