Week 8 Flashcards
coelochaete
aquatic plants or rocks in freshwater environments
charales
along the margins of lakes and estuaries
coleochaete and charales
fertilisation of sperm and egg
diploid zygotes are released and dispersed by water currents
diploid zygote undergoes meiosis at its first division to form haploid cells
one of the haploid cells develops into a multicellular haploid alga
sperm are released into the water while egg is retained
bryophytes
sperm release is stimulated by raindrops, egg is retained
diploid zygote is retained and the sporophyte develops in place, supported mechanically and nutritionally by the gametophyte
multicellular sporophyte produces thousands of haploid spores by meiosis
haploid spores are released into the air. Those that land in a suitable site will germinate to form a new gametophyte generation
sporophyte
diploid multicellular plant produces spores via meiosis
sporophyte generation
obtain water and nutrients from gametophyte
gametophyte
haploid multicellular plant produces gametes via mitosis
gametophyte generation
photosynthetically self sufficient
alternation of generations
haploid gametophyte generation and a diploid sporophyte generation follow one another
basic life cycle of all land plants
gametophyte vs sporophyte nutrients
gametophyte is photosynthetically self sufficient
sporophyte obtains water and nutrients needed for growth from gametophyte
sporangium
capsule at top of sporophyte
thousands of diploid cells undergo meiosis, producing many haploid spores
dispersal
reduces competition
allows offspring to avoid pathogens and parasites
allows offspring to colonise new habitats
vascular plants
sporophyte is the dominant generation as physically larger than gametophyte and higher photosynthetic production
Lycophytes, ferns and horsetails
depend on swimming sperm for fertilisation and disperse by spores that are released into the air
spore dispersing vascular plants
both the gametophyte and sporophyte generation are free living; each is able to supply its own nourishment
seed plant life cycle
formation of two types of spores: male gametophyte and female gametophyte
spores not dispersed; gametophyte develop within their sporangium and remain attached to the sporophyte
pollination
maturation of a fertilised ovule into a seed
pollination
transport of pollen, either in the air or by an animal, from sporangium where it was produced to a location near an ovule
seed
embryo, stored resources and an outer, protective coat
pine trees
a fertilised ovule develops into a seed (2n)
seed dispersal
germination to form sporophyte (3n)
female gametophytes (2n) develop from spores within ovule cones
male gametophytes (2n) develop from spores within pollen cones
Both produce haploid spores via meiosis
male becomes pollen (n)
female becomes ovule (n)
pollen is released into the air and transported by wind; some land on ovule cones
before fertilisation can occur, the pollen must germinate to form a pollen tube that grows to the female gametophyte
ovule cones
upper branches
produce spores that develop into female gametophytes which produce female gametes
pollen cones
lower in tree
produce spores that develop into male gametophytes which produce male gametes
seeds contain tissue from 3 generations
outside: protective seed coat
centre: embryo develops from zygote and represent next sporophyte generation
inside: embryo surrounded by haploid female gametophyte for nutrients
seeds function
store more resources for growth for next generation
high levels of proteins and oils
seed dormancy
can delay germination even when conditions for grwoth are favourable
most favourable with small seeds
during seed maturation, lose water so metabolism drops and embryo stops growing, allows dormancy
flower
angiosperm pollen and ovules produced
flower parts
outer whorls, inner whorls, carpels, ovary, stamen, sepals, petals
outer whorls
sepals and petals
inner whorls
pollen producing stamens and ovule producing carpels
carpels
modified leaves that are folded over and sealed along edges to form hollow chamber
sporangia produced on inner surface
one or more carpels on each flower
ovary
one to many ovules develop
protects the ovules from being eaten or damaged by animals but makes it impossible for pollen to land; pollen instead lands on stigma
stamen
consists of a filament that supports a structure known as the anther, which contains several sporangia
outer whorls
produce neither pollen nor ovules
instead contribute to reproduciton in other way
sepal
encase and protect flower during development
petal
attract and orient animal pollinators, produce volatile oils
angiosperm- self compatible species
pollen and ovules produced by flowers on the same plant can form viable offspring
angiosperm- self incompatible species
pollen transferred between different plants
angiosperm male gametophyte
3 cells
one controls growth of the pollen tube while other two are male gametes or sperm
angiosperm female gametophyte
8 nuclei
6 haploid cells and a central cell with 2 nuclei
angiosperm endosperm
develops only when fertilisation has occurred
fruits
as fertilised egg develops to form an embryo and the endosperm proliferates around it, the ovary wall develops into a fruit, stimulated by signalling molecules produced by the endosperm
fruits protect immature seeds from being preyed on by animals, and enhance dispersal once seeds are mature
asexually produced plants disperse
with and without seeds
most reproduce asexually without seeds, instead new plant grows out of part of parent plant
or through vegetative reproduction
apomixis
seeds develop even in the absence of fertilisation (asexually)
haploid female gametophyte within the
ovule
pollen
multicellular male gametophyte and surrounding outer wall containing sporopollenin
if ovule is fertilised
develops into seed
