Transcript Parade through the Plants

Parade through the Plants
Chapter 29 and 30
What is a plant?
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Multicelled
Eukaryotic
Autotrophic
Cell wall made of cellulose
Additional Characteristics
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Cuticle
Stomata
Secondary products (poisons, lignin, sporopollenin)
Starch storage
The Four Phyla
• Bryophyta – mosses
– nonvascular
• Pterophyta – ferns
– Vascular
– Seedless
• Gymnosperm – conifers
– Vascular
– “Naked” seeds – not
enclosed in an ovary
• Angiosperm – flowering
plants
– Vascular
– Seeds contained in fruits
– a mature ovary
Plant kingdom in
monophyletic (derived
from a common
ancestor)
Gametophyte
generation becomes
reduced
Sperm goes from
flagellated to pollen
Vascular plants
Origin of the seed
Emergence of
flowering plants
Why are Charophyceans thought to be ancestors
of land plants?
1. Homologous Chloroplasts
2. Biochemical similarity
3. Similarity in the mechanisms of mitosis
and meiosis
4. Similarity in sperm structure
5. Genetic relationship (rRNA)
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Charophytes are not the
ancestors of plants. Evidence shows that
the modern Charophytes and plants both
evolved from a common ancestor that
would be classified as a Charophyte.
Adaptations of land plants (aka “embryophytes)
• Deal with drying out, UV light and reproduction
without water
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Lignin
Sporopollenin
Reduced gametophyte
Gametangia
Apical meristem
Seeds
Pollen grain
Vascular tissue (xylem/phloem)
One generation is a Gametophyte (n) – multicelled individual made of haploid cells
-- produces gametangia by mitosis…gametes within the gametangia are
protected by a jacket of “sterile” cells (protects gametes and embryos).
Antheridia – male gametangia…produces sperm
Archegonia – female gametangia…produces egg
One generation is a Sporophyte (2n) – multicelled individual made of diploid cells
-- produce haploid “spores” via meiosis
-- spores divide via mitosis to produce gametophyte
Sterile cells
Sterile
cells
Sperm
Egg
Antheridia
Archegonia
Bryophytes
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Nonvascular
Gametophyte is the dominant stage of life cycle
Need water to reproduce
Lack lignin-fortified tissue
Gametophyte generation is dominant generation
 sporophyte is smaller and short lived. Depends on the gametophyte
for water and nutrients
Diploid sporophyte produces haploid spores via meiosis in a structure
called a sporangium
Adaptations of Pteridophytes (ferns) not seen in Bryophytes
1. Subterranean root system (Bryophytes had rhizoids)
2. Stems
3. Leaves
4. Vascular Tissue
a. Xylem – water, minerals up (dead cells)
b. Phloem – sugars, amino acids throughout (living cells)
5. Lignin
a. function in mechanical support
b. Xylem also has lignified cells
Dominant phase of the fern life cycle is the sporophyte phase.
How is the reduced gametophyte an
adaptation for seed plants?
 Spores are retained within the sporangia (not released)
 Gameotphyte develops within the wall of the spore
 Exposed to sun’s UV rays (mutations) – diploid can handle
mutations more easily than haploids.
 Sporophyte embryo is dependent on tissues of the
maternal gametophyte
Why not completely eliminate the
gametophyte generation?
Cooksonia – oldest fossilized
vascular plant preserved down
to the tissue – sporophyte was
dominant stage and it was
branched.
What is the significance of the seed? The seed replaced the spore as
the main means of dispersing offspring
•Multicelled
•Sporophyte embryo packaged with food and protective
coat (can withstand more harsh environments)
•Can disperse offspring more widely
•All seed plants are heterosporous
•Megasporangium is a solid fleshy structure called the
nucellus
Ovule
•Integuments envelop megasporangium
•Megaspores
•Female gametophyte develops within the wall of the
megaspore nourished by nucellus. This contains the egg.
What is the advantage of pollen?
Pollen grain = Male gametophyte (became vehicles for sperm cells in
seed plants)
•Microspores develop into pollen grains which mature to
be male gametophytes (protected by sporopollenin
•If it lands close to the ovule, it elongates a tube that
discharges one or more sperm into the female
gametophyte within the ovule.
• Mode of travel different than water
Four Phyla of Gymnosperms
1. Phylum Cycadophyta (thrived with the
dinosaurs)
2. Phylum Ginkgophyta (Ginko biloba is the
only surviving species)
3. Phylum Gnetophyta
4. Phylum Coniferophyta – most common
Adaptive value of the flower to plants:
Pollination more specific (rely more on insects and other animals to
transfer pollen, not just wind)
Fruits (mature ovaries) protect dormant seeds and aid in their dispersal.
Role of Ovaries and Ovules – the wall of the ovary thickens when an egg
(ovule) is fertilized. This is the “fruit.” The seeds are fertilized ovules.
Examples: pea pods, apples, oranges
Features that aid in seed dispersal
parachutes or propellers (wind)
hollow inside (coconut) so it floats
Burrs to cling to fur (animal dispersal)
Edible (animal disperal)