Gymnosperms Flashcards
Seed
consists of an embryo and nutrients surrounded by a protective coat
what is the protective coat of a seed called
Integument
what does the Integument do
contains food supply for embryo
What is common to seed plants
reduced gametophytes
heterospory
Ovules
pollen
where do the gametophytes of the seed plants develop
within the walls of spores that are retained within tissues of the parent sporophyte
What are the two kinds of gametophytes
Male gametophytes
Female gametophytes
Male gametophytes
Pollen grains
dispersed by wind, water, or pollinator
No need for water
Female Gametophytes
Develop within an ovule
Enclosed within diploid sporophyte tissue in angiosperms
Ovule and protective tissue are the ovary
The ovary develops into fruit
The ancestors of seed plants were
homosporous
Seed plants are
heterosporous
Megasporangia
produce megaspores that give rise to female gametophytes
Microsporangia
produces microspores that give rise to male gametophytes
Ovule
consists of a megasporangium, megaspore, and one or more protective integuments
How many integuments do gymnosperm megaspores have
One
How many integuments do angiosperm megaspores have
two
Megasporangium in females
diploid tissue where haploid megaspore is formed (meiosis)
Microspores in females
haploid cell that grows into the female gametophyte, including the egg nucleus
Microsporangium in Males
diploid tissue where haploid microspores are formed (meiosis).
Microspores in Males
develop into male gametophyte
Pollen in Males
contains the male gametophyte within the tough pollen wall
Process of Gymnosperm fertilization
- Pollen released into air, spread for miles
- Pollen grain reaches ovule and germinates
- Pollen tube grows, digesting through megasporangium
- Pollen tube reaches egg nucleus, discharges sperm nucleus into egg nucleus of female gametophyte
Pollen grains
Microspores develop into pollen grains, which contain the male gametophytes
Pollination
the transfer of pollen to the part of a seed plant containing the ovules
What does pollen do
eliminates the need for a film of water and can be dispersed great distances by air or animals
What happens if a pollen grain germinates
it gives rise to a pollen tube that discharges two sperm into the female gametophyte within the ovule
Where does a seed develop from
the whole ovule
A seed is a ____
sporophyte embryo, along with its food supply, packaged in a protective coat
Evolutionary advantages of seeds over spores
- May be dormant for years, until conditions are favorable for germination
- May be transported long distances by wind or animals
Phylum Cycadophyta
- large cones and palm like leaves
- Mesozoic, relatively few today
- 300 alive today
- rare plant collectors are willing to steal
- largest sperm of all organisms
Phylum Ginkgophyta
- consists of a single species, Ginkgo biloba
- has high tolerance to air pollution
- dioecious
- leaves remain little changed for 270 million years
Dioecious
Male and female structures on different trees
Phylum Gnetophyta
- compromises three genera
- species vary in appearance, and some are tropical whereas others live in deserts
Three genera of gnetophyta
Gnetum
Ephedra
Welwitschia
Phylum Coniferophyta
- Largest of the gymnosperm phyla
- Most are evergreens and can carry out photosynthesis year round
