Angiosperms Flashcards
Angiosperms
seed plants with two key reproductive adaptations: flowers and fruits
Phylum of angiosperms
Anthophyta
The ____ is the dominant generation
sporophyte
The gametophytes are ____ and depend on the ____ for nutrients
microscopic, sporophyte
Flowers
specialized structures for sexual reproduction
Different types of modified leaves
Sepals, petals, stamens, and carpels
Sepals
leaves that enclose the flower
petals
leaves that are brightly coloured to attract pollinators
stamens
leaves that produce pollen
carpels
leaves that produce ovules
___ and ___ are reproductive organs
stamens and carpels
Stamen consists of
stalk (filament), anther (containing microsporangia) that produce pollen
microsporangia
pollen sacks inside of anther that produce pollen
carpel consists of
ovary (at the base), style, and sigma
Megaspore
the female genotype
Complete flowers contain:
all 4 flowar organs
Approx __ of angiosperms have incomplete flowers
12%
Infloroscences
clusters of flowers
A pollen grain consists of:
two-celled male gametophyte and sporopollenin-rich outer wall
Pollen develops from
microspores within the microsporangia of anthers
Microspores undergo mitosis to produce:
two-celled male gametophytes, generative cell (sperm nuclei) and tube cell (pollen tube)
The embryo sac develops in
an ovule contained in the ovary at the sigma base
Megasporocyte in megasporium undergoes meiosis and
produces 4 megaspores (only one survives)
Megaspores produce
7-celled female gametophyte after division
Pollenation
the transfer of pollen from an anther to a stigma
Pollination occurs via
wind, water, animals
After pollination:
- pollen grain produces a pollen tube
- generative cell undergoes mitosis to produce two sperm nuclei
- the pollen tube of the male gametophyte grows down into the ovary and discharges two sperm nuclei into an ovule
Double fertilization
occurs when the pollen tube discharges two sperm nuclei into the embryo sac within an ovule
One sperm nuclei fertilize the egg to form a while The second sperm nuclei forms
1, zygote (2n)
2. combines with polar nuclei, giving rise to the triploid food-storing endosperm (3n)
After double fertilization
− Each fertilized ovule develops into a seed.
− The ovary develops into a fruit enclosing the seed(s).
Endosperm development
- Triploid endosperm undergoes repeated mitosis to produce starchy food tissues for the embryo.
- Triploid endosperm takes nutrients from the parent gametophyte during development.
endosperm in monocots
the endosperm stores nutrients that can be sued by the seedling
endosperm in most eudicots
food reserves of the endosperm are exported to the cotyledons (embryo)
The first mitotic division splits the zygote into
basal cell and terminal cell
basal cell
The basal cell produces a multicellular suspensor, which anchors the embryo in the endosperm cavity and facilitates the transfer of nutrients to the developing embryo
The terminal cell
gives rises to most of the embryo
After fertilization
each fertilized ovule develops into a seed, the ovary develops into a fruit enclosing the seeds
A fruit forms when
the ovary wall thickens and matures
Fruit functions
protect seeds, assist seed dispersal by wind, water, or animals
Classifications of fruit
dry (ovary dries out during maturity) and fleshy (thick, soft, and sweet at maturity)
Adaptive advantages of angiosperm fertilization
- Nutrient stores in the seed (endosperm) develops only after double fertilization.
- Fruit development is usually triggered by fertilization
- Female gametophyte greatly reduced in size and hence cheaper to produce
- Rapid growth of the small female gametophyte
