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.

4

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.

3

On the undersideof the sporophyte‘sreproductive leavesare spots called sori.Each sorus is acluster of sporangia.

6

A zygote develops into a newsporophyte, and the young plantgrows out from an archegoniumof its parent, the gametophyte.

5

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

Table 29.1 Ten Phyla of Extant Plants