Phylogeny of land plants Flashcards
Describe seed dispersal mechanisms
- oceanic drift
- wind
- lizards
- birds (secondary dispersal)
- dung
Describe the Embyrophytes
multicellular haplodiplontic zygotes
Describe a haplontic life cycle
- zygote is diploid (2n)
- zygote undergoes meiosis
- forms uni- or multicellular haploid (n) organism
- produces haploid gametes
- haploid gametes undergo fertilisation
Describe a haplodiplontic life cycle
- sporophyte is diploid (2n) and multicellular
- (mega and micro-)sporangia undergo meiosis to produce haploid (n) (mega and micro-)spores
- spores form haploid multicellular gametophytic organisms (of different sexes)
- produce haploid gametes for fertilisation
Spores do not undergo
fertilisation
Describe the Bryophytes morphologically and ecologically
- small plants (20cm max.)
- dominant haploid phase
- leptoids, no tracheids
- rhizoids, no roots
- phyllids, thalloid, no leaves
- sporophyte usually a stalk (seta) and sporangium
- water necessary for fertilisation
Describe the Bryophytes taxonomical
- mosses (12,000 sp)
- hornworts (215 sp)
- liverworts (7271 sp)
Describe moss morphology
- pseudoelater
- stoma
- capsule
- calyptra
- meristem
- foot
- seta
- leafy gametophyte
- thallus
- rhizoids
protonema
- thread-like chain of cells
- forms the earliest stage of development of the gametophyte in the life cycle of mosses
Describe a moss life cycle
- within the sporophyte, meiosis produces 1n spores
- each spore grows into a 1n gametophyte
- sperm swim into archegonium from other antheridium and fertilise egg
- produces 2n sporophyte embryo
Give an example of a moss
Phaeomegacerossquamuliger
Describe Sphagnum moss
hyaline cells take up 20 times weight in water
hyaline cells
- dead, polysaccharides
- absorbative, antiseptic
When were stomata innovated?
after liverworts before mosses
What separates the Charophytes from the Bryophytes?
- cuticle
- sporopollenin spores
Describe the Bryophyte Monophyly hypothesis
two lineages of land plants
Describe the Bryophyte Paraphylyl hypothesis
- hornwort sister to all land plants
- mosses sister to liverworts
- both sister to tracheophytes, step-wise
OR - hornwort sister to tracheophytes
- mosses sister to liverworts
- both sister to all other land plants, step-wise
Soft polytomy
simultaneous divergence
What taxa do Embryophytes include?
LMHLMS
Characteristics of the Bryophytes
- sporopollenin
- spores
- cuticle
- stomates
- haploid (1n) dominance
Describe the LMH-LMS transition
- vascular tissue
- rise of the diploid (2n) phase
What is phase dominance?
what does the most photosynthesis
Monilophytes
- Ferns
- Calamites
- Water Ferns
Tracheophytes
- vascular plants
- ## have tracheids
tracheids
- water conducting cell
- vessel member dead at maturity
- perforations or one large hole at each end
- generally elongate with a lignified secondary wall
- c. 1-7mm in vascular plants
- 1-2mm in angiosperms
vessel
several to many vessel members
Who are the Tracheophytes?
LMS
Describe the Monilophytes
- gametophyte (1n) prothallus
- fronds
- circinate vernation
- 30% epiphytic
Describe fern fronds
- simple
- deeply pinnatifid
- once pinnate
sporangium
enclosure in which spores are formed
sori
clusters of sporangia
indusium
a thin membranous covering shielding a sorus on a fern frond.
vernation
arrangement of leaves in a bud
circinate
rolled up with the tip in the centre
Give examples of circinate vernation
- Crozier
- Fiddleheads
Describe epiphytic ferns
rhizome & vegetative reproduction
Describe the Monilophyte life cycle
- sorus (containing indium and sporangia) releases spore
- spore germinates
- forms gametophytic prothallus
- prothallus produces egg (in archegonium) and sperm
- fertilisation
- sporophyte develops into fronds
Describe the water ferns
- heterosporous
- Salvinia’s and Marsilea’s
Anabaena azollae
- nitrogen fixing cyanobacterium
- lives in the cavities of Azolla
List some water ferns
- Salvinia
- Marsilea
- Azolla
Lycophytes contain
Clubmosses, Spikemosses and Quillworts
List some Lycophyte genera
- Lycopodium (genus of clubmosses)
- Selaginella (spike moss)
- Isoetes (quillworts)
Describe lycophytes
- microphyllous leaves
Who has megaphyllous leaves?
- Pteropsids
- Spermatophytes
- reduced in Sphenopsids
Pteropsids
true ferns
Describe Lepidodendron
- Carboniferous clubmoss
- found in fossil grove, Victoria park, Glasgow
- leaf scars with single trace
Describe the polyphyletic origin of heterospory
- Selaginella
- Isoetes
- water ferns
- many extinct lineages
- evolved at least 10 times independently
Describe Carboniferous Coal Swamps
an age of free sporing plants
Calamites
horsetails
Where did megaphylls evolve?
after lycophytes and before monilophytes
Where did microphylls evolve?
on lycophyte branch
Describe seed production
- a particular version of heterospory
- two types of sporangia
- microsporangia produce microspores (pollen grains) which are dispersed by wind (anemophily) or insects (entomophily)
- megasporangia and megaspores
- reduced number of megaspores provides space for nourishing tissue
- does not rely on free water.
Describe the megasporangium
- integument
- funicle
- ovary wall
- chalaza
- micropyle
- functional megaspore
- nucellus (ovule)
- polar nuclei
- synergies
- antipodal cells
What is the megagametophyte?
embryo sac
Seeds
fertilised ovules
