GYMNOSPERMS & ANGIOSPERMS Flashcards
The vast majority of modern plants produce __ and include about __ species of
gymnosperms and almost __ species of angiosperms, so it is no wonder that seeds are so
familiar—particularly those of flowering plants
seeds
760
250,000
gymnosperm seeds form on the __ or __ and are “exposed” in the sense that they are not completely enclosed within a fruit
surface of leaves
branches of cones
gymnosperm seeds result from a __ of sperm and egg
single fertilization
in gymnosperm seeds, the developing embryo is being nourished by the __
megagametophyte tissue
angiosperm seeds result from a __ of sperm with egg and with __ of the megagametophyte (female gametophyte)
double fertilization
two nuclei
in angiosperm seeds, the nourishment is provided by __
endosperm
structure in angiosperm seeds - formed by the union of a sperm with two nuclei of the megagametophyte
endosperm
for the plants that produce them, seeds provide the __ between generations—the future and the past
sexual biological link
to be successful in an evolutionary sense, a plant must transfer its __ to the next generation
genes
the evolution of the seed, an __ combined with a food supply and surrounded by a __, allowed plants to be much more successful on land
embryonic plant
protective seed coat
the __ of seeds enables seed plants to survive extended periods of cold winter or drought
dormant state
the __ serves as a barrier against bacterial or fungal decay
seed coat
a __ produced by the microgametophyte (male gametophyte) delivers sperm to the egg, making fertilization possible without the presence of water
hollow pollen tube
accordingly, the vast majority of seed plants have non-flagellated sperm
➢ the exceptions are a few gymnosperms, the __ and __
cycads
Ginkgo biloba
the evolution of seeds is closely tied to the evolution of __ and sporangia on __
sporophylls
sporangia
evolution of the seed
before the development of the large vascularized leaves known as __, sporophytes bore sporangia at the end of leafless branches known as __
megaphylls
telomes
evolution of seed
the association of sporangia with leaves began during the __ period (409 to 363 million years ago) and continued through the evolution of the sporophytes of seedless vascular plants, gymnosperms, and finally angiosperms
Devonian
evolution of seed
most of the intermediate forms of plants are extinct, but
two key precursors to the emergence of seeds were __ and __
heterospory
endosporic development
evolution of seed
the original vascular land plants were probably __, with one type of spore produced by one type of sporangium
homosporous
all seed plants are __, producing two types of spores,
__ and __, in two different types of sporangia, microsporangia and megasporangia
heterosporous
microspores
megaspores
in most seedless plants, both extinct and living, spores germinate to produce gametophytes outside the confines of the spore wall, known as __
exosporic development
the gametophytes of seed plants develop __, growing
inside the spore, a process also evident in a few seedless vascular plants, including Selaginella
endosporically
the selective advantage of __ may be that it protects the developing gametophyte from desiccation while supplying nutrition and water
endosporic development
The term gymnosperm is derived from the Greek gymnos, “__”, and sperma, “__”. This term has no taxonomic status, however, but rather is a descriptive of a heterogenous group of plants characterized by the production of naked seeds.
naked
seed
Estimates from fossil records indicate that gymnosperms must have evolved approximately 300 million years ago from non-seed-producing ancestors of the extinct division __, which were fern-like in appearance.
Progymnospermatophyta
_- is an adaptation of great significance for the survival and dispersal of plants. In fact, this was part of the competitive advantage that allowed the gymnosperms to supersede the other vascular plants as the dominant type of vegetation on land.
Seed production
although __ reproduction is found in a few species of gymnosperms, __ reproduction is predominant most gymnosperms
asexual
sexual
gymnosperms, particularly __ are wind-pollinated
conifers
in some gymnosperm species, __ and _- are on separate plants
- pines and many other conifer species have both types of cones (strobili) on each plant
pollen cones
ovulate cones
gymnosperms
also known as female cones or seed cones, usually occur on higher branches
ovulate cones
gymnosperms
also known as male cones, typically occur on lower branches
pollen cones
gymnosperms
this arrangement promotes cross-pollination, because the windblown pollen is not usually distributed from the bottom to the top of the same tree
pollen cones
the transfer of
pollen from one plant to another
cros-pollination
ovulate cones in conifers are typically more complex than pollen cones
true
pollen cones in conifers are sometimes called __ because each cone consists of __ microsporophylls attached directly to a central axis
➢ each microsporophyll, known more commonly as a __, has two pollen-containing microsporangia on its lower surface
simple cones
spirally arranged
scale
the complex ovulate cones that are characteristic of pine and most other conifers are sometimes __ can enter through a small opening in the integument called a __ (Greek pyle, “gate”).
grains
micropyle
pine life cycle
unlike an antheridium, which contains many single-celled sperm, each __ contains several hundred microsporocytes, also known as __
microsporangium
microspore mother cells
pine life cycle
(1) each microsporocyte undergoes __ to produce four haploid microspores
▪ each microspore then gives rise to a __, a pollen grain
with four cells, that develops endosporically
meiosis
microgametophyte
pine life cycle
(2)
➢ two of the cells, known as __, have no known function
➢ a third cell is called the __ because it will give rise to a sterile stalk cell as well as to what is known as a body cell, which eventually produces two sperm
➢ the fourth cell is called the __ because it will produce the pollen tube, which is a device that facilitates delivery of sperm to the egg without water
prothallial cells
generative cell
tube cell