Evolution and Diversity of Plants

Chapter 24

2Evolution and Evolution and Diversity of PlaDiversity of Plantsnts

OutlineOutline

Evolutionary History Evolutionary History

Alternation of GenerationsAlternation of Generations

Nonvascular PlantsNonvascular Plants

Vascular PlantsVascular Plants

SeedlessSeedless

SeedSeed

AngiospermsAngiosperms

­Monocots and EudicotsMonocots and Eudicots

­ FlowersFlowers

3Evolution and Evolution and Diversity of PlaDiversity of Plantsnts

Evolutionary History of PlantsEvolutionary History of PlantsMore than 98% of all biomass is plantsMore than 98% of all biomass is plants

Multicellular photosynthetic eukaryotesMulticellular photosynthetic eukaryotes

280,000 known species280,000 known species

Thought to have evolved from freshwater Thought to have evolved from freshwater algae over 500 myaalgae over 500 mya

Evolution of plants marked by four Evolution of plants marked by four evolutionary events associated with four evolutionary events associated with four major groups of plantsmajor groups of plants

Nonvascular PlantsNonvascular Plants

­ Advent of nourishment of a multicellular embryo Advent of nourishment of a multicellular embryo within the body of the female plantwithin the body of the female plant

4Representatives of the

Four Major Groups of Plants

5Evolution and Evolution and Diversity of PlaDiversity of Plantsnts

Evolutionary History of PlantsEvolutionary History of Plants

Seedless vascular plants Seedless vascular plants

Advent of vascular tissueAdvent of vascular tissue

Gymnosperms and angiospermsGymnosperms and angiosperms

Produce seedsProduce seeds

Flowering PlantsFlowering Plants

Attract pollinators that give rise to Attract pollinators that give rise to fruitsfruits

6 Evolutionary History of Plants

7Evolution and Evolution and Diversity of PlaDiversity of Plantsnts

Alternation of GenerationsAlternation of GenerationsLife cycle involves alternation of generationsLife cycle involves alternation of generations

Multicellular 1n individuals (gametophytes) Multicellular 1n individuals (gametophytes) produce multicellular 2n individuals (sporophytes)produce multicellular 2n individuals (sporophytes)

Multicellular 2n individuals (sporophytes) produce Multicellular 2n individuals (sporophytes) produce multicellular 1n individuals (gametophytes)multicellular 1n individuals (gametophytes)

Sporophyte (2n):Sporophyte (2n): Multicellular individual that produces spores by Multicellular individual that produces spores by meiosismeiosis

Spore is haploid cell that will become the Spore is haploid cell that will become the gametophytegametophyte

Gametophyte (1n):Gametophyte (1n): Multicellular individual that produces gametesMulticellular individual that produces gametes Gametes fuse in fertilization to form zygoteGametes fuse in fertilization to form zygote Zygote is a diploid cell that will become the Zygote is a diploid cell that will become the sporophytesporophyte

8 Alternation of Generations

9Evolution and Evolution and Diversity of PlaDiversity of Plantsnts

Alternation of GenerationsAlternation of Generations

Appearance of generations varies widelyAppearance of generations varies widely

In ferns, female portions are archegonia In ferns, female portions are archegonia and are fertilized by flagellated spermand are fertilized by flagellated sperm

In angiosperm, female gametophyte In angiosperm, female gametophyte (embryo sac), consists of an ovule(embryo sac), consists of an ovule

­ Following fertilization, ovule becomes Following fertilization, ovule becomes seedseed

In seed plants, pollen grains are mature In seed plants, pollen grains are mature sperm-bearing male gametophytessperm-bearing male gametophytes

10 Reduction in the Size of the Gametophyte

11Evolution and Evolution and Diversity of PlaDiversity of Plantsnts

Other Terrestrial AdaptationsOther Terrestrial Adaptations

Vascular tissue transports water and Vascular tissue transports water and nutrients to the body of the plantnutrients to the body of the plant

Cuticle provides an effective barrier to Cuticle provides an effective barrier to water losswater loss

Stomata bordered by guard cells that Stomata bordered by guard cells that regulate opening, and thus water regulate opening, and thus water lossloss

12 Protection of Eggs and Embryos

13 Leaves of Vascular Plants

14Evolution and Evolution and Diversity of PlaDiversity of Plantsnts

Nonvascular PlantsNonvascular Plants

Nonvascular plants (bryophytes) Nonvascular plants (bryophytes)

Lack specialized means of transporting Lack specialized means of transporting water and organic nutrientswater and organic nutrients

Do not have true roots, stems, and Do not have true roots, stems, and leavesleaves

Gametophyte is dominant generationGametophyte is dominant generation

Produces eggs in archegoniaProduces eggs in archegonia

Produces flagellated sperm in antheridiaProduces flagellated sperm in antheridia

Sperm swim to egg in film of water to Sperm swim to egg in film of water to make zygotemake zygote

15Evolution and Evolution and Diversity of PlaDiversity of Plantsnts

Nonvascular PlantsNonvascular PlantsHornworts (phlym Anthocerophyta) have Hornworts (phlym Anthocerophyta) have small sporophytes that carry on small sporophytes that carry on photosynthesisphotosynthesis

Liverworts (phylum Hepatophyta) have Liverworts (phylum Hepatophyta) have either flattened thallus or leafy either flattened thallus or leafy appearanceappearance

Mosses (phylum Bryophyta) usually have Mosses (phylum Bryophyta) usually have a leafy shoot, although some are a leafy shoot, although some are secondarily flattenedsecondarily flattened

Can reproduce asexually by fragmentationCan reproduce asexually by fragmentation

Dependent sporophyte consists of foot, Dependent sporophyte consists of foot, stalk, and sporangiumstalk, and sporangium

16Hornwort

17Liverwort, Marchantia

18Moss (Polytrichum) Life Cycle

19Evolution and Evolution and Diversity of PlaDiversity of Plantsnts

Vascular PlantsVascular Plants

Xylem conducts water and dissolved Xylem conducts water and dissolved minerals up from rootsminerals up from roots

Phloem conducts sucrose and other Phloem conducts sucrose and other organic compounds throughout the plantorganic compounds throughout the plant

Lignin strengthens walls of conducting Lignin strengthens walls of conducting cells in xylemcells in xylem

Most seedless vascular plants are Most seedless vascular plants are homosporoushomosporousWindblown spores are dispersal agentsWindblown spores are dispersal agents

All seed plants are heterosporous and All seed plants are heterosporous and have male and female gametophyteshave male and female gametophytesSeeds disperse offspringSeeds disperse offspring

20Cooksonian Fossil

21Vascular Tissue

22Evolution and Evolution and Diversity of PlaDiversity of Plantsnts

Seedless Vascular PlantsSeedless Vascular Plants

Club Mosses (phylum Lycophyta)Club Mosses (phylum Lycophyta)

Typically, branching rhizome sends up Typically, branching rhizome sends up short aerial stemsshort aerial stems

Leaves are microphylls (have only one Leaves are microphylls (have only one strand of vascular tissue)strand of vascular tissue)

Sporangia occur on surfaces of Sporangia occur on surfaces of sporophyllssporophylls

­Grouped into club-shaped strobiliGrouped into club-shaped strobili

23 Club Moss, Lycopodium

24Evolution and Evolution and Diversity of PlaDiversity of Plantsnts

Seedless Vascular PlantsSeedless Vascular Plants

Ferns and AlliesFerns and Allies

Horsetails (phylum Sphenophyta) Horsetails (phylum Sphenophyta)

­Rhizome produces tall aerial stemsRhizome produces tall aerial stems

­Contains whorls of slender, green Contains whorls of slender, green branchesbranches

­Small, scalelike leaves also form whorls Small, scalelike leaves also form whorls at the jointsat the joints

25 Horsetail, Equisetum

26Evolution and Evolution and Diversity of PlaDiversity of Plantsnts

FernsFerns

Whisk Ferns (phylum Psilotophyta)Whisk Ferns (phylum Psilotophyta)Branched rhizome has rhizoidsBranched rhizome has rhizoids

Mutualistic mycorrhizal fungus helps Mutualistic mycorrhizal fungus helps gather nutrientsgather nutrients

Ferns (phylum Pterophyta)Ferns (phylum Pterophyta)Large conspicuous frondsLarge conspicuous fronds

­Divided into leafletsDivided into leaflets

­Dominant sporophyte produces Dominant sporophyte produces windblown sporeswindblown spores

27 Whisk fern, Psilotum

28Diversity of ferns

29Fern Life Cycle

30Evolution and Evolution and Diversity of PlaDiversity of Plantsnts

Seed PlantsSeed Plants

Seed plants are the most plentiful Seed plants are the most plentiful plants in the biosphereplants in the biosphere

Seed coat and stored food allow an Seed coat and stored food allow an embryo to survive harsh conditions embryo to survive harsh conditions during long period of dormancyduring long period of dormancy

HeterosporousHeterosporous

­Drought-resistant pollen grainsDrought-resistant pollen grains

­Ovule develops into seedOvule develops into seed

31Seed Plants

32Evolution and Evolution and Diversity of PlaDiversity of Plantsnts

GymnospermsGymnosperms

Gymnosperms have ovules and seeds Gymnosperms have ovules and seeds exposed on the surface of exposed on the surface of sporophyllssporophylls

ConfiersConfiers

CycadsCycads

GinkgoesGinkgoes

GnetophytesGnetophytes

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ConifersConifers

Conifers, as well as other gymnosperm Conifers, as well as other gymnosperm phyla, bear conesphyla, bear cones

Tough, needlelike leaves of pines Tough, needlelike leaves of pines conserve water with a thick cuticle conserve water with a thick cuticle and recessed stomataand recessed stomata

­Considered a “soft” wood because it Considered a “soft” wood because it consists primarily of xylem tissueconsists primarily of xylem tissue

34Pine Life Cycle

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CycadsCycads

Cycads (phylum Cycadophyta) Cycads (phylum Cycadophyta)

Large, finely divided leaves that grow Large, finely divided leaves that grow in clusters at the top of the stemin clusters at the top of the stem

Pollen and seed cones on separate Pollen and seed cones on separate plantsplants

Pollinated by insectsPollinated by insects

36Cycad Cones

Figure­24.19

37Evolution and Evolution and Diversity of PlaDiversity of Plantsnts

GinkgoesGinkgoes

Ginkgoes (phylum Ginkgophyta) Ginkgoes (phylum Ginkgophyta)

DioeciousDioecious

Some trees producing seedsSome trees producing seeds

Others producing pollenOthers producing pollen

One surviving species (One surviving species (Gingko bilobaGingko biloba))

38The Ginkgo Tree

39Ephedra

Figure­24.21

40Welwitschia miribilis

41Evolution and Evolution and Diversity of PlaDiversity of Plantsnts

GnetophytesGnetophytes

Gnetophytes (phylum Gnetophyta)Gnetophytes (phylum Gnetophyta)

Have similarly structured xylemHave similarly structured xylem

None have archegoniaNone have archegonia

Strobili have similar constructionStrobili have similar construction

42Evolution and Evolution and Diversity of PlaDiversity of Plantsnts

AngiospermsAngiosperms

Angiosperms (phylum Anthophyta) Angiosperms (phylum Anthophyta)

An exceptionally large and successful An exceptionally large and successful group of plantsgroup of plants

Ovules are always enclosed within Ovules are always enclosed within diploid tissuesdiploid tissues

Became dominant group of plants in Became dominant group of plants in the late Cretaceous and early the late Cretaceous and early Paleocene periodsPaleocene periods

43Amborella trichopoda

44Evolution and Evolution and Diversity of PlaDiversity of Plantsnts

Monocots and EudicotsMonocots and Eudicots

Two classes of flowering plantsTwo classes of flowering plants

Monocotyledones (Monocots)Monocotyledones (Monocots)

­One cotyledon in seedOne cotyledon in seed

Eudicotyledones (Dicots)Eudicotyledones (Dicots)

­ Two cotyledons in seedTwo cotyledons in seed

45Flower Diversity

46Evolution and Evolution and Diversity of PlaDiversity of Plantsnts

The FlowerThe Flower

Peduncle (flower stalk) expands at tip Peduncle (flower stalk) expands at tip into a receptacleinto a receptacle

Bears sepals, petals, stamens, and Bears sepals, petals, stamens, and carpels, all attached to receptacle in carpels, all attached to receptacle in whorlswhorls

Calyx (collection of sepals) protect Calyx (collection of sepals) protect flower bud before it opensflower bud before it opens

Corolla (collection of petals)Corolla (collection of petals)

47Evolution and Evolution and Diversity of PlaDiversity of Plantsnts

The FlowerThe Flower

Each stamen consists of an anther and Each stamen consists of an anther and a filament (stalk)a filament (stalk)

Carpel has three major regionsCarpel has three major regions

Ovary - Swollen baseOvary - Swollen base

­ FruitFruit

Style - Elevates stigmaStyle - Elevates stigma

Stigma - Sticky receptor of pollen Stigma - Sticky receptor of pollen grainsgrains

48Generalized Flower

49Flowering plant life cycle

50Evolution and Evolution and Diversity of PlaDiversity of Plantsnts

Flowers and DiversificationFlowers and DiversificationWind-pollinated flowers are usually not Wind-pollinated flowers are usually not showyshowy

Bird-pollinated flowers are often colorfulBird-pollinated flowers are often colorful

Night-blooming flowers attract nocturnal Night-blooming flowers attract nocturnal mammals or insectsmammals or insects

Usually white or cream-coloredUsually white or cream-colored

Fruits of flowers protect and aid in Fruits of flowers protect and aid in dispersaldispersal

Utilize wind, gravity, water, and animals Utilize wind, gravity, water, and animals for dispersalfor dispersal

51Evolution and Evolution and Diversity of PlaDiversity of Plantsnts

ReviewReview

Evolutionary History Evolutionary History

Alternation of GenerationsAlternation of Generations

Nonvascular PlantsNonvascular Plants

Vascular PlantsVascular Plants

SeedlessSeedless

SeedSeed

AngiospermsAngiosperms

­Monocots and EudicotsMonocots and Eudicots

­ FlowersFlowers

Evolution and Diversity of Plants

Ending Slide Chapter 24