Gymnospores Flashcards
Seed plants are called
gymnosperms
the most dominant producers in most terrestrial ecosystems
seed-bearing plants
A seed consists of
an embryo and nutrients surrounded by a protective coat
Shared derived traits of seed plants
- reduced gametophytes
- heterospory
- ovules
- pollen
- seeds
Gametophytes of seed plants develop by
they develop within cell walls of spores that are retained within tissues of parent sporophyte
Sporophyte in non-vascular plants:
independent, dominant gametophyte; sporophyte dependent on the gametophyte
Sporophyte in seedless vascular plants
dominant sporophyte, but gametophyte still independent
Sporophyte in seed plants
sporophyte dominant and independent; gametophyte microscopic and dependent on the sporophyte
Trend: progressive ___ in size and
independence of the gametophyte, and the ___ role of the sporophyte
reduction, increasing
All seed plants are ___ while most seedless plants are homosporous
heterosporous
Heterosporous plants
produce two sizes of spores
two sizes of spores
megaspores and microspores
Microsporangia produce
microspores that give rise to male gametophytes
Megasporangia produce
megaspores that give rise to female gametophytes
Spores are ___ dispersed in seed plants
not
Ovule
consists of a megasporangium (2n), megaspore (1n), and one or more protective integuments (2n). Ovules develop into seeds after fertilization
The megasporangium (2n) produces a megaspore (1n) via
meiosis
Is the megaspore dispersed?
no
Pollination triggers:
development of female (mega) gametophyte (1n)
Microspores develop into
male gametophytes, which are contained
within pollen grains
Pollen grains are coated with
sporopollenin (withstands desiccation, damage, UV)
Microsporangium (2n) produces microspores (1n) via
meiosis
Microspores develop into:
pollen grain
Microspores undergo mitosis to
produce
tiny male gametophytes (1n)
Pollen grain contains ___ that develops within the spore wall
male gametophyte
Each male gametophyte has:
a generative cell and a tube cell
generative cell
become sperm nuclei after pollination
tube cell
becomes sperm pollen tube after pollination
Pollen eliminates the need for
water for fertilization
Pollination
the transfer of pollen to part of a seed plant containing ovules
What happens if a pollen grain germinates
it gives rise to a pollen tube that discharges two sperm nuclei into female gametophyte within the ovule
A seed develops from the
whole ovule
A fertilized seed develops into
seed containing next generation sporophyte
In seed plants, fertilization is ____ of water
independant
Male gametophyte transported in
___ through the air to the
female gametophyte (sperm not
released into the environment)
pollen
Two living clades of seed plants
gymnosperms and angiosperms
Gymnosperms
“naked seed” plants
Angiosperms
flowering plants
Angiosperms seeds are enclosed in:
fruits, which are mature ovaries
first seed plants appear in the fossil
record
gymnosperms (360 mya)
Gymnosperms dominated
Mesozoic terrestrial ecosystems (were better adapted to dry conditions)
Angiosperms began to replace gymnosperms near the end of
the Mesozoic
conifers
cone-bearing gymnosperms which dominate northern altitudes
4 Phyla of Gymnosperms
Cycadophyta, gingkophyta, gnetophyta, and coniferophyta
Living gymnosperms for a ____ group
monipholetic
Cycads produce ___ leaves on ____ stems
large palm-like leaves, stout,
unbranched stems.
Cycad cones
They have large cones on separate male and female sporophytes (insect pollinated
Clades that have flagellated sperm
cycads and ginkgos
Living species of Ginkgo
Ginkgo biloba
Ginkgo biloba traits
Distinctive bi-lobed leaves, separate male and female sporophyte trees, wind-pollinated and flagellated sperm,
3 genera of Gnetophyta phylum
Gnetum, Ephedra, Welwitschia
Coniferophyta traits
- woody shrubs or trees
- wind-pollinated
- evergreens and carry out photosynthesis year-round
- adapt to cold dry habitats
How conifers are adapt to cold climate
- Xylem is resistant to collapse following freezing.
− Leaves with thick waxy epidermis; reduced leaf surface area; leaf retention
Key features of gymnosperm life cycle
- The dominance of the sporophyte generation
- development of seeds from fertilized ovules
- the transfer of male gametophyte to ovules by pollen
