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Chapter 29 Plant Diversity
1. What are the characteristics of plants?- Photosynthetic autotrophs- Cellulose in cell walls- Starch as storage polysaccharide- PROBLEM – light, CO2 & O2 are above ground
- water & minerals are below ground- SOLUTION – evolution of specialized structures
2. What adaptations do plants have for survival on land?- Stomata – pores used for gas exchange- Roots – absorb water & minerals from underground- Apical meristems – tips of shoots & roots where growth occurs- Cuticle – waxy covering to prevent water loss thru leaves- Jacketed gametangia – gamete producing organ with protective jacket
of cells to prevent dehydration- Sporopollenin – polymer that formed around exposed zygotes & forms
walls of plant spores preventing dehydration- Lignin – structural polymer that provides strength for woody tissues of
vascular plants
Algae also
Chapter 29: Plant Diversity
1. What are the characteristics of plants?2. What adaptations do plants have for survival on land?3. What were the adaptations/highlights of plant evolution?
- Plants likely evolved from Charophytes (green algae)- similar peroxisome enzymes- similar %age of cellulose found in plants & charophytes- nuclear & chloroplast genes have similar DNA
- Movement to land led to Bryophytes (mosses & worts)- Tougher spores (sporopollenin)- Jacketed gametangia
- Vascular tissue (ferns)- Cells joined to transport water & nutrients- Lacked seeds
- Development of seeds (Gymnosperms, e.g. pine tree)- More protection of embryo- Embryo w/ food
- Development of flowers (Angiosperms, e.g. oak tree)- Complex reproductive structure
Figure 29.7 Highlights of plant evolution
Bryophytes(nonvascular plants) Seedless vascular plants Seed plants
Vascular plants
Land plants
Origin of seed plants(about 360 mya)
Origin of vascular plants (about 420 mya)
Origin of land plants(about 475 mya)
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Chapter 29 Plant Diversity
1. What are the characteristics of plants?2. What adaptations do plants have for survival on land?3. What were the adaptations/highlights of plant evolution?4. Describe alternation of generations
- Alternates between sexual & asexual reproduction
- Gametophyte (n) make gametesby mitosis
- Sporophyte (2n) makes sporesby meiosis
Haploid multicellularorganism (gametophyte)
Mitosis Mitosis
Gametes
Zygote
Diploid multicellularorganism (sporophyte)
Alternation of generations: a generalized scheme
MEIOSIS FERTILIZATION
2n2n
n
n
nn
nSpores
Mitosis
Figure 29.8 The life cycle of a Polytrichum moss
Maturesporophytes
Youngsporophytes
Malegametophyte
Raindrop
Sperm
Key
Haploid (n)Diploid (2n)
Antheridia
Femalegametophyte
Egg
Arch-egonia
FERTILIZATION
(within archegonium)Zygote
Archegonium
Embryo
Femalegametophytes
Gametophore
Foot
Capsule(sporangium)
Seta
Peristome
Spores
Protonemata
“Bud”
“Bud”
MEIOSIS
Sporangium
Calyptra
Capsule with peristome (LM)
Rhizoid
Maturesporophytes
Figure 29.9 Bryophyte Diversity
LIVERWORTS (PHYLUM HEPATOPHYTA)
HORNWORTS (PHYLUM ANTHOCEROPHYTA) MOSSES (PHYLUM BRYOPHYTA)
Gametophore offemale gametophyte
Marchantia polymorpha,a “thalloid” liverwort
Foot
Sporangium
Seta
500
µmMarchantia sporophyte (LM)
Plagiochiladeltoidea,a “leafy”liverwort
An Anthoceroshornwort species
Sporophyte
Gametophyte
Polytrichum commune,hairy-cap moss
Sporophyte
Gametophyte
Figure 29.12 The life cycle of a fern
Fern sperm use flagellato swim from the antheridia to eggs in the archegonia.
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Sporangia release spores.Most fern species produce a singletype of spore that gives rise to abisexual gametophyte.
1 The fern sporedevelops into a small,photosynthetic gametophyte.
2 Although this illustration shows an egg and sperm from the same gametophyte, a variety of mechanismspromote cross-fertilizationbetween gametophytes.
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On the undersideof the sporophyte‘sreproductive leavesare spots called sori.Each sorus is acluster of sporangia.
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A zygote develops into a newsporophyte, and the young plantgrows out from an archegoniumof its parent, the gametophyte.
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MEIOSIS
Sporangium
Sporangium
Maturesporophyte
Newsporophyte
Zygote
FERTILIZATION
Archegonium
Egg
Haploid (n)
Diploid (2n)
Spore Younggametophyte
Fiddlehead
Antheridium
Sperm
Gametophyte
Key
Sorus
Figure 29.14 Seedless Vascular Plant Diversity
LYCOPHYTES (PHYLUM LYCOPHYTA)
PTEROPHYTES (PHYLUM PTEROPHYTA)
WHISK FERNS AND RELATIVES HORSETAILS FERNS
Isoetesgunnii,a quillwort
Selaginella apoda,a spike moss
Diphasiastrum tristachyum, a club moss
Strobili(clusters ofsporophylls)
Psilotumnudum,a whiskfern
Equisetumarvense,fieldhorsetail
Vegetative stem
Strobilus onfertile stem
Athyrium filix-femina, lady fern
Chapter 30: The Evolution of Seed Plants1. What are the 3 most important reproductive adaptations?
- Reduction of the gametophyte- Advent of the seed – replaced spore - Evolution of pollen – male gametophyte
- Air dispersal instead of sperm swimming
Sporophyte dependent on gametophyte (mosses and other bryophytes).
(a) Large sporophyte and small, independent gametophyte (ferns and other seedless vascular plants).
(b)
Microscopic femalegametophytes (n) inovulate cones(dependent)
Sporophyte (2n),the flowering plant(independent)
Microscopic malegametophytes (n)inside these partsof flowers(dependent)
Microscopic malegametophytes (n)in pollen cones(dependent) Sporophyte (2n)
(independent)
Microscopic femalegametophytes (n)inside these partsof flowers(dependent)
Reduced gametophyte dependent on sporophyte (seed plants: gymnosperms and angiosperms).
(c)
Gametophyte(n)
Gametophyte(n)
Sporophyte(2n)
Sporophyte(2n)
Figure 30.2 Gametophyte/sporophyte relationships
Chapter 30: The Evolution of Seed Plants1. What are the 3 most important reproductive adaptations?
- Reduction of the gametophyte- Advent of the seed – replaced spore as - Evolution of pollen – male gametophyte
2. How does an ovule become a seed?- Fertilization- Growth of the embryo
Figure 30.3 From ovule to seed
Unfertilized ovule. In this sectionalview through the ovule of a pine (a gymnosperm), a fleshy megasporangium is surrounded by a protective layer of tissue called an integument. (Angiosperms have two integuments.)
(a) Fertilized ovule. A megaspore develops into a multicellular female gametophyte. The micropyle, the only opening through the integument, allows entry of a pollen grain. The pollen grain contains a male gametophyte, which develops a pollen tube that discharges sperm.
(b) Gymnosperm seed. Fertilization initiates the transformation of the ovule into a seed, which consists of a sporophyte embryo, a food supply, and a protective seed coat derived from the integument.
(c)
Integument
Spore wall
Megasporangium(2n)
Megaspore (n)
Male gametophyte(within germinatingpollen grain) (n)
Femalegametophyte (n)
Egg nucleus (n)
Dischargedsperm nucleus (n)
Pollen grain (n)Micropyle
Seed coat(derived fromintegument)
Food supply(femalegametophytetissue) (n)
Embryo (2n)(new sporophyte)
Chapter 30: The Evolution of Seed Plants1. What are the 3 most important reproductive adaptations?2. How does an ovule become a seed?3. What’s the difference between a megaspore & a microspore?
- Megasporangia megaspores female gametophytes (eggs)- Microsporangia microspores male gametophytes (sperm)
4. What are gymnosperms?- “naked seed” plants- Pines, spruce, fir, sequoia, yews, junipers, ginkgo - Most lumber & paper products- The gymnosperm life cycle…
Figure 30.6 The life cycle of a pine
FERTILIZATION
Seed coat(derived fromparentsporophyte) (2n)
Food reserves(gametophytetissue) (n)
Embryo(new sporophyte)(2n)
Seeds on surfaceof ovulate scale
Seedling
MEIOSIS
Survivingmegaspore (n)
Germinatingpollen grain
ArchegoniumIntegumentEgg (n)
Femalegametophyte
Germinatingpollen grain (n)
Dischargedsperm nucleus (n)
Pollentube
Egg nucleus (n)
Ovule
Key
Haploid (n)Diploid (2n)
Megasporocyte (2n)
Integument
Longitudinalsection ofovulate cone
Ovulatecone
Pollencone
Maturesporophyte(2n)
Longitudinalsection ofpollen cone
Microsporocytes(2n)
Pollengrains (n)(containing malegametophytes)
Micropyle
Germinatingpollen grain
Megasporangium
MEIOSIS
Sporophyll
Microsporangium
Chapter 30: The Evolution of Seed Plants1. What are the 3 most important reproductive adaptations?2. How does an ovule become a seed?3. What’s the difference between a megaspore & a microspore?4. What are gymnosperms?
- “naked seed” plants- Pines, spruce, fir, sequoia, yews, junipers, ginkgo - Most lumber & paper products- The gymnosperm life cycle…
5. What are angiosperms?- Flowering plants
6. What is a flower?- Reproductive structure of an angiosperm
Figure 30.7 The structure of an idealized flower
Anther
Filament
Stigma
Style
Ovary
Carpel
Petal
ReceptacleOvule
Sepal
Stamen
Female structures
Male structures
Chapter 30: The Evolution of Seed Plants1. What are the 3 most important reproductive adaptations?2. How does an ovule become a seed?3. What’s the difference between a megaspore & a microspore?4. What are gymnosperms?5. What are angiosperms?6. What is a flower?
- Reproductive structure of an angiosperm7. What is a fruit?
- Mature ovary- Helps seed dispersal
Figure 30.8 Some variations in fruit structure
Ruby grapefruit, a fleshy fruitwith a hard outer layer andsoft inner layer of pericarp
(b)Tomato, a fleshy fruit with soft outer and inner layers of pericarp
(a)
Nectarine, a fleshyfruit with a soft outerlayer and hard innerlayer (pit) of pericarp
(c)
Walnut, a dry fruit that remains closed at maturity
(e)(d) Milkweed, a dry fruit thatsplits open at maturity
Figure 30.9 Fruit adaptations that enhance seed dispersal
Wings enable maple fruits to be easily carried by the wind.
(a)
Seeds within berries and other edible fruits are often dispersed in animal feces.
(b)
The barbs of cockleburs facilitate seed dispersal by allowing the fruits to “hitchhike” on animals.
(c)
Chapter 30: The Evolution of Seed Plants1. What are the 3 most important reproductive adaptations?2. How does an ovule become a seed?3. What’s the difference between a megaspore & a microspore?4. What are gymnosperms?5. What are angiosperms?6. What is a flower?7. What is a fruit?8. The angiosperm life cycle….
Figure 30.10 The life cycle of an angiosperm
Nucleus ofdevelopingendosperm
(3n)
Zygote (2n)
FERTILIZATION
Embryo (2n)
Endosperm(foodsupply) (3n)
Seed coat (2n)
Seed
Germinatingseed
Pollentube
Sperm
Stigma
Pollengrains
Pollentube
Style
Dischargedsperm nuclei (n)
Eggnucleus (n)
Mature flower onsporophyte plant(2n)
Key
Haploid (n)
Diploid (2n)
Anther
Ovule withmegasporangium (2n)
Male gametophyte(in pollen grain)
Microspore (n)
MEIOSIS
Microsporangium
Microsporocytes (2n)
MEIOSIS
Generative cell
Tube cell
Survivingmegaspore(n)
Ovary
Megasporangium(n)
Female gametophyte(embryo sac)
Antipodal cellsPolar nucleiSynergidsEgg (n)
Pollentube
Sperm(n)
Double fertilization
Chapter 30: The Evolution of Seed Plants1. What are the 3 most important reproductive adaptations?2. How does an ovule become a seed?3. What’s the difference between a megaspore & a microspore?4. What are gymnosperms?5. What are angiosperms?6. What is a flower?7. What is a fruit?8. The angiosperm life cycle….9. Why is double fertilization important?
- Synchronizes food development with embryo development- Prevents angiosperms from wasting nutrients on unfertilized ovules
10. What are the 2 general types of angiosperms?- Monocots- Eudicots
Orchid(Lemboglossumrossii)
MonocotCharacteristics
Embryos
Leafvenation
Stems
Root
Pollen
Flowers
Pollen grain withone opening
Root systemUsually fibrous(no main root)
Vascular tissuescattered
Veins usuallyparallel
One cotyledon Two cotyledons
Veins usuallynetlike
Vascular tissueusually arranged
in ring
Taproot (main root)usually present
Pollen grain withthree openings
Zucchini (CucurbitaPepo), female(left) and male flowers
Pea (Lathyrus nervosus,Lord Anson’s blue pea),a legume
Dog rose (Rosa canina), a wild rose
Pygmy date palm (Phoenix roebelenii)
Lily (Lilium“Enchant-ment”)
Barley (Hordeum vulgare), a grass
Anther
Stigma
Californiapoppy(Eschscholziacalifornica)
Pyrenean oak(Quercuspyrenaica)
Floral organsusually in
multiples of three
Floral organs usuallyin multiples of
four or fiveFilament Ovary
EudicotCharacteristics
MONOCOTS EUDICOTS