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Definitons
Alternation of generations
Homospory and heterospory
First land plants
definitions
100
What is sporangia?
singular: sporangium specialized organ that is part of a mature sporophyte contains many diploid cells that EACH undergo meiosis to produce spores
100
How can a zygote produce multiple sporophytes?
If a sporophyte reproduces clonally, it can produce multiple clones (sporophytes) normally, a given zygote developes initially into a sporophyte
100
Are the spores different?
spores in homosporous plants are of a single type.
100
What are the divisions of the first land plants (non-vascular)?
Hepatophyta (liverworts) Anthocerophyta (hornworts) Bryophyta (mosses)
100
What is a homosporous species?
produce only one type of spore all spores appear identical to one another -ancestral condition in plants and applies to non-vascular plants
200
What is a gametophyte?
each spore developes into ONE gametophyte through mitosis all cells of the gametophyte are GENETICALLY IDENTICAL to the spore, since it only undergoes mitosis, not meiosis -all gametes produced from a single gametophyte will be genetically identical to each other may produce many gametangia; each gametangium will produce ONLY EGGS or ONLY SPERM
200
Can a sporophyte create multiple sporangia?
YES!! each sporangium can also produce many spores - spores from a given sporangium are genetically UNIQUE (due to meiosis)
200
What occurs in heterosporous plants?
there are two types of spores produced: megaspore and microspore they form the mega(female)/micro(male)gametophyte they mature into egg and sperm fertilization occurs zygote formed embryo sporophyte mega and microsporangium spore mother cell MEIOSIS mega/micro spore
200
What are the general characteristics of the first land plants?
HOMOSPOROUS!! gametophyte stage is DOMINANT - larger than and provides nutrients to the sporphyte that is attached to it -sporophyte dies after spores are released, but gametophyte will remain alive SOME SPECIES ARE PROTECTED WITH A THIN CUTICLE require water for fertilization -sperm swim to the eggs -live in habitats that are moist no xylem and phloem - non vasculat small in size - allows water and minerals to reach all parts of the plant through OSMOSIS and DIFFUSION spores are elevated above soil surface -STALKED SPORANGIA
200
What are heterosporous species?
produce 2 types of spores the types are visibly distinguishable from one another (big or small) heterospory is found in more derived/advanced plant lineages
300
What is a zygote?
first cell of the diploid phase of the life cycle can only divide by mitosis (which eventually forms the sporophyte)
300
What are the two types of gamete making organs?
Antheridia (male-sperm) archegonia (female-egg)
300
What are some problems plants face?
need structual support to get vertical growth -get light when competing with other plants need plumbing system -transport water vertically from soil to growing tips -transport carbs from leaves to reproductive parts water loss can be severe
300
what are rhizoids?
hair like structures on gametophyte that absorb water form substrate
400
What are spores?
They are the first cells of the haploid life cycle they can only divide by mitosis were a product of meiosis (from the diploid sporangium) - each spore is genetically unique
400
What are the two types of alternation of generations? what does it depend on?
Homosporous species heterosporous species dependent on the taxon
400
What are the names of the two types of spores produced in heterosporous plants?
megaspore microspore
400
What are some characteristics that bryophyta have to counter the problems faced as a plant?
stomata sporopollenin rhizoids sporophyte has protective epidermis alternation of generations embryo embedded in and protected by gametophyte tissue
400
what is sporopollenin?
major component of tough outer wall of spores
500
What is a gametangium?
specialized organ that is part of the mature gametophyte haploid cells can either develop into either sperm or egg
500
What are the two spores produced in heterosporous alternation of generations?
megaspores: haploid cells that undergo mitosis, developing into multicellular gametophytes that produces eggs IN THE ARCHEGONIA microspores: haploid cells that undergo mitosis, developing into multicellular gametophytes that produce sperm, IN THE ANTHERIDIA NOTE: THE GAMETOPHYTES ARE UNISEXUAL
500
What is unique about the gametangium of heterosporous plants?
They are unisexual
500
When did non vascular plant evolve?
during ordovican perios 450 mya earth: shallow seas mild and humid climate
500
Why is the embryo embedded in gametophyte tissue?
the egg is fertilized in the gametophyte