Lecture 18 Flashcards
why are seeds advantageous
protect embryo, stored food
all seed plants are what
heterosporous
spores are no longer released, they are stored in what
the megasporangium
in ovule evolution, how many megaspores survive
one of four
what envelops the megasporangium
the integument
where does the embryo develop
inside the megagametophyte
what is the one important trend that was seen during the evolution of the seed
gradually integuments fused until only opening left at apex (micropyle)
what are the five phyla of seed plants with living representatives
cyadophyta, ginkgophyta, coniferophyta, gnetophyta, anthophyta
what is polyembryony
all eggs are fertilized by only one embryo develops fully
how does fertilization occur in gymnosperms
male pollen grain transferred to female gametophyte usually by wind, water not required
what do gymnosperms lack
no antheridia in seed plants
how do sperm differ among the different gymnosperm groups
nonmotile in conifers and gnetophytes, motile in cycads and ginko
what are some characteristics of coniferophyta
most numerous, widespread, ecologically important gymnosperm, leaves have many drought resistant characteristics
what are pine needles like
adapted for low soil moisture, thick cuticle, hypodermis, sunken stomata
what is the pine life cycle
two years to complete, microsporangia and megasporangia born on separate cones on same tree, usually male on lower branches and females up higher
what are characteristics of pine microsporangiate cones
small, microsporocytes, meiosis in early spring, immature male gametophyte
what are characteristics of pine megasporangiate cones
larger, seed scale complex, scales in spiral, ovule, after meiosis only one megaspore is functional
when does pine pollination occur
in the spring
when does pine fertilization occur
about 12 months after pollination, all eggs are fertilized but only one is functional
what is the seed life cycle for pines
two diploid sporophytic generations, one haploid generation, seeds usually shed in fall of second year
what two trees are in the family cupressaceae
bald cypress and redwood
which family has the tallest living plant
family cupressaceae
what are some characteristics of cycads
11 genera, palm like plants, fairly large, distinct trunk covered with bases of shed leaves, true secondary growth, highly toxic, reproductive units (conelike structures and unisexual)
how do cycads pollinate
insects
