Origins of Plants- From land to sea

What did plants descend from?
A eukaryotic ancestor and cyanobacteria
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How did photosynthesis evolve in plants?
Photosynthesis originally evolved in cyanobacteria and then plants acquired this by endosymbiosis
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What is endosymbiosis?
Symbiosis (both organisms benefit from relationship) where one organism lives inside another- cyanobacteria inside plant
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Which plant is believed to be the first plant?
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What are glaucophytes?
Freshwater plants, unicellular, contain chlorophyll, unique chloroplasts, only 13 species
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Describe the chloroplasts of glaucophytes
Contain small amounts of peptidoglycan between inner and outer membrane (the same that is found in cyanobacteria, this feature is lost in all other plant groups)
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Describe red algae
Multicellular, phycoerythrin as photosynthetic accessory pigment, important components of coral reefs, can change colour due to light intensity (green at surface, red further down)
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Describe green algae
Mainly freshwater, important biofouling organisms, Chlorophytes
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What did land plants evolve from?
Green algae (chlorophytes)
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What type of plant is thought to be the closest living relative of land plants?
Charophytes- a division of green algae, (due to comparisons of nuclear and chloroplast genes)- Land plants not descended from modern charophytes but they share a common ancestor
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In charophytes, what stops the zygotes from drying out?
Sporopollenin, found in plant spore walls
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What factors allowed movement onto land by early charophyte ancestors?
Unfiltered sun, more CO2, nutrient-rich soil, lack of herbivores and pathogen
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What problems did the plants face moving onto land?
Lack of water and lack of structural support from being surrounded by water
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What are the 4 key traits that appear in nearly all land plants but not charophytes?
Multicellular dependent embryos, walled spores produced in sporangia, multicellular gametangia, apical meristems
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Name 3 other trains developed by land plants
Waxy cuticle on epidermis, mycorrihizae (symbiosis of plant roots and fungi) Secondary compounds to deter herbivores and parasites
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Describe the plant lifecycle/ reproduction
Spores released, develops into gametophyte with both egg and sperm, fertilisation forms zygote, which develops into a sporophyte which then produces haploid spores by meiosis
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How are nutrients transferred to the embryo within the female gametophyte?
Through placental transfer cells
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Why are land plants called embryophytes?
Because of the dependency of the embryo on the parent plant
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Where are the gametes produced in embryophytes?
Within organs called gametangia
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Female gametangia- produces eggs and is the site of fertilisation
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Male gametangia- produces and releases sperm
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What is an apical meristem?
Tip of plant, a region of actively dividing cells (stem cells), cells differentiate into various tissues and allow continual growth for plant
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What is a vascular plant?
Plants that have vascular tissue (xylem & phloem), most plants are vascular
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What is a non-vascular plant?
Plants with out a vascular bundle
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How did photosynthesis evolve in plants?


Photosynthesis originally evolved in cyanobacteria and then plants acquired this by endosymbiosis

Card 3


What is endosymbiosis?


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Card 4


Which plant is believed to be the first plant?


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Card 5


What are glaucophytes?


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