Chapter 30: Plant Diversity II Flashcards
Advantages of reduced gametophytes?
- Protects gametophytes from environmental stresses; enables developing gametophytes to obtain nutrients from parental sporophyte
Ovules + Protection of Eggs
- Integument envelops and protects the megasporangium
- Whole structure is an ovule, inside female gametophyte develops from megaspore
Pollen grain
- Microspore develops into these; consist of male gametophyte enclosed within pollen wall
- Transfer of pollen to part of seed plant that contains the ovules is pollination
Advantages of seeds
- Single-celled
- Remain dormant for months or years
- Supply of stored food
Gymnosperms
- Bear naked seeds typically on cones
Conifers
- Cone-bearing plants (gymnosperms)
- Pines, firs, redwoods
Life Cycle of a Pine
- (2n) Each tree has both ovulate and pollen cones
- Microsporocytes divide by meiosis; produce haploid microspores–>pollen grains
- Ovulate cone scale has two ovules (each contain megasporangium)
- Pollination occurs when pollen gain reaches the ovule; pollen grain germinates to form pollen tube
- Pollen tube develops and megasporocyte undergoes meiosis to produce four haploid cells (one survives as megaspore)
- Megaspore develops into female gametophyte that contains 2-3 archegonia; each of which will form an egg
- By the time eggs are mature, sperm cells have developed in pollen tube (extends into female gametophyte)
- Fertilization occurs when sperm + egg nuclei unite
First seed plants
- 360 million years ago
Dominant life stage for mosses/nonvascular
Gametophyte
Dominant life stage for ferns/seedless vascular
Sporophyte
Dominant life cycle for seed plants
Sporophyte
Gymnosperms in Plant Phyla
- Cycadophyta
- Gingkgophyta
- Gnetophyta
- Coniferophyta
Characteristics of Angiosperms
- Flower
- Petals
- Stamens: produce microspores that develop into pollen
- Filament: Stalk that comprises stamen
- Anther: Terminal sac where pollen is produced
- Carpels: make megaspores; female gametophytes
- Stigma: Tip of carpal that receives pollen
Complete flowers
Have all four organs
Fruits
Seed develops from ovules after fertilization, ovary wall thickens and matures into fruit
Angiosperm Life Cycle
- Megasporangium of each ovule: Megasporocyte divides by meiosis to produce four megaspores; one survives
- On anther, microsporangium contain microsporocytes that divide by meiosis
- Microspore develops into pollen grain; generative wall will divide
- Pollination: Two sperm cells are discharged in each ovule
- Double fertilization occurs; on forms zygote and other forms endosperm
- Zygote develops into an embryo that is packaged along with food into a seed
- Seed germinates and embryo develops into mature sporophyte
Micropyle
Pore in integuments of ovule
Cotyledons
Rudimentary root, and on or two seed leaves
Endosperm
Tissue rich in starch and other food reserves that nourish the developing embryo
Monocot
- One cotyledon
- Embryos
- Leaf venation
- Root system usually fibrous
- Pollen grain with one opening
Dicot
Two cotyledons
Eudicots
- Two cotyledons
- Netlik veins
- Vascular tissue in a ring
- Taproot
- Pollen grain with three opening
- Floral organs usually in multiple of four or five
