Dr. Mitch Pavao-Zuckerman Department of Ecology and Evolutionary Biology

621621--82208220 mzuckermzucker@[email protected] OfficeOffice hours:hours: BiosciencesBiosciences WestWest 431431 WW andand FF 11--22 p.m.p.m. oror byby appointmentappointment Diversity of Plants Diversity of Plants (Fig 29.4)

Chlorophyta Ancestral Alga

Nontracheophytes

Nonseed Tracheophytes

Gymnosperms The Transition to Life on Land Angiosperms The Vascular Plants The Seed Plants The Flowering Plants Monophyly

• Monophyletic group – includes the most recent common ancestor and all decendents

• These are NOT monophyletic: GreenGreen PlantsPlants ((viridiphytesviridiphytes)) areare aa monophyleticmonophyletic groupgroup

• Green Plants include the Chlorophytes (green algae) • Other green algae • and the land plants EmbryophytesEmbryophytes (Land(Land Plants)Plants)

Land Plants are also a monophyletic group

• Photosynthetic eukaryotes that use chlorophyll aa and bb and store carbohydrates starch

• Resting embryo with placental connection to the parent. The Conquest of the Land HistoryHistory ofof plantsplants onon landland •• 500500 myamya -- aa fewfew algaealgae andand lichens.lichens. •• ByBy 460460 myamya -- primitiveprimitive LandLand PlantsPlants,, •• ByBy 425425 myamya -- EarlyEarly VascularVascular PlantsPlants werewere commoncommon

•• HowHow diddid itit happen?happen? •• Obstacles?Obstacles? Reconstruction

Fossil The Conquest of the Land EarlyEarly innovationsinnovations inin landland plantplant evolution:evolution: 1.1. cuticlecuticle (waxy(waxy coating)coating)

2.2. thickthick sporespore wallwall

3.3. AntheridiaAntheridia andand archegoniaarchegonia (gamete(gamete cases),cases), 4.4. protectedprotected embryoembryo 5.5. protectiveprotective pigmentspigments –– flavonoidsflavonoids absorbabsorb damagingdamaging UVUV lightlight Land Plants (Embryophytes) (Fig 29.4)

Chlorophyta Ancestral Alga

Nontracheophytes Protected Embryos Nonseed Tracheophytes

Gymnosperms

Angiosperms Plant Kingdom? Nontracheophytes: Liverworts, Hornworts, and Mosses

•• SmallSmall plantsplants (compared(compared toto presentpresent dayday shrubsshrubs andand trees)trees) •• LackLack specializedspecialized waterwater (xylem)(xylem) andand foodfood conductingconducting tubestubes (phloem)(phloem) ofof vascularvascular plants.plants.

•• RelyRely onon diffusiondiffusion ofof waterwater andand minerals.minerals. Plant life cycles feature alternation of generations (Fig 29.2)

Multicellular Haploid gametophyte

Spore Gametes

Haploid (n) Meiosis Fertilization Diploid (2n) Diploid Zygote

Multicellular sporophyte Nontracheophytes: Liverworts, Hornworts, and Mosses

• Diploid generation is Fig. 29.5 smaller than the haploid generation and • Diploid depends on it for water and nutrition.

• “The big green thing” is the haploid stage. •The diploid stage is attached to it. Liverworts (9,000 species) •• LackLack stomatesstomates (pores(pores withwith guardguard cellscells thatthat regulateregulate C02C02 uptakeuptake andand H20H20 loss).loss). •• SmallSmall sporespore producingproducing diploiddiploid phasephase comparedcompared toto hornwortshornworts oror mossesmosses Hornworts (100 species) •• HaveHave stomatesstomates •• HornHorn--shapedshaped sporespore producingproducing diploiddiploid stagestage •• OneOne largelarge flatflat chloroplastchloroplast perper cellcell Mosses (15,000 species)

• Have stomates • Spore producing upright diploid stage with capsule • Capsule has a lid and row of teeth that release the spores in wet weather. WhatWhat isis notnot aa commoncommon featurefeature ofof nonnon--vascularvascular plants?plants?

a. They are all relatively small

b. They all lack specialized conductive tissue such as xylem and phloem

c. All possess stomata for gas exchange

d. The big generation is haploid (one set of chromosomes) with the smaller diploid (two sets of chromosomes) generation attached and dependent. Land Plants (Embryophytes) (Fig 29.4)

Chlorophyta Ancestral Alga

Nontracheophytes Protected Embryos Nonseed Tracheophytes Vascular tissue

Gymnosperms Vascular Plants (Tracheophytes) Angiosperms Vascular Plants •• ThickThick--walledwalled deaddead waterwater--conductingconducting cellscells..

‹ moremore efficientefficient waterwater movementmovement

‹ supportsupport forfor talltall plants.plants. Vascular Plants • The diploiddiploid generationgeneration becamebecame LARGERLARGER and independent of the haploid generation. Figure 28.19

FigureFigure 29.2029.20 Tracheophytes

• The earliest tracheophytes lacked roots.

• Roots – possibly evolved from branches Tracheophytes • Simple leaves may have evolved from the spore producing structures.

• Complex leaves may have evolved from a branching stem system.

Difference? Land Plants (Embryophytes) (Fig 29.4)

Chlorophyta Ancestral Alga

Nontracheophytes Protected Embryos Nonseed Tracheophytes Vascular tissue

Gymnosperms Vascular Plants (Tracheophytes) Angiosperms Nonseed Tracheophytes Club mosses 1,200 species • Simple leaves • Cone-like structures with spores. • Dominated tropical coastal swamps in Carboniferous period 300 myaÆ coal deposits. • SelaginellaSelaginella is common here in the desert. Nonseed Tracheophytes Whisk Ferns 15 species • Simple branching like ancient vascular plants. • Tiny simple leaves Reconstruction of ancient • No true roots tracheophyte Tracheophytes Horsetails 15 species • Jointed hollow stems • Silica deposits (“scouring rush”) • Leaves in whorls • Spore sacs under “shields” on “cones” Nonseed Tracheophytes Ferns 12,000 species • Big complex leaves with branching veins • Spores in sacs clustered on the bottom of the leaf •Tree ferns can reach 60 ft • Leaves unfold from “fiddlehead” What is not a common feature of Non-Seed Tracheophytes?

a. They are larger than non-vascular plants

b. They possess specialized cells for moving water and food

c. All possess stomata for gas exchange

d. The big generation is haploid (the gametophyte with one set of chromosomes) Land Plants (Embryophytes) (Fig 29.4)

Chlorophyta Ancestral Alga

Nontracheophytes Protected Embryos Nonseed Tracheophytes Vascular tissue

Seeds Gymnosperms

Seed plants Angiosperms Seed Plants 300,000 species •• TheThe seedseed plantsplants havehave greatlygreatly reducedreduced haploidhaploid stagestage.. •• HowHow diddid thisthis happen?happen?

Fig 30.2 Seed Plants 300,000 species

•• FurtherFurther reducedreduced haploidhaploid generation.generation.

‹ PartPart ofof thethe evolutionevolution ofof seedsseeds andand pollen.pollen. •• SeedsSeeds -- protectedprotected restingresting stagestage openingopening manymany possibilities,possibilities, likelike suspendedsuspended animationanimation..

••PollenPollen -- spermsperm deliverydelivery system;system; escapeescape thethe needneed ofof waterwater forfor spermsperm toto swim.swim. How did seeds evolve?

• Ancestors of seed plants had one kind of spore. • First dimorphic spores evolved:

‹ Microspores (grow into sperm producing haploid stage)

‹ Megaspores (grow into egg producing haploid stage)

• Megaspores reduced to just one.

Spore sac How did seeds evolve? •• MegasporeMegaspore envelopedenveloped inin aa sac.sac. •• FemaleFemale haploidhaploid stagestage growsgrows inin thisthis “seed”.“seed”.

•• ItIt isis attachedattached toto thethe diploiddiploid parent.parent. Pollen is a reduced male haploid stage Diploid Haploid Plant and flower are diploid Spore sac Spores

Reduced haploid stage Pollination 1. Pollen Æ reduced haploid female. 2. Pollen produce sperm to fertilize an egg. 3. The zygote develops into a seed embryo. Seed Plants 300,000 species

•• So,So, seedseed plantsplants makemake seedsseeds andand pollenpollen •• AlsoAlso makemake woodwood.. •• EvolvedEvolved ~~ 370370 myamya Land Plants (Embryophytes) (Fig 29.4)

Chlorophyta Ancestral Alga

Nontracheophytes Protected Embryos Nonseed Tracheophytes Vascular tissue

Seeds Gymnosperms

Angiosperms Seed Plants - Gymnosperms

•• GymnospermGymnosperm == ‘naked‘naked seeded’seeded’ •• DoDo notnot havehave flowersflowers oror fruitfruit tissuetissue Gymnosperms - 4 Phyla Cycads Ginkos

Gnetophytes Gymnosperms - Conifers

• Leaves often “evergreen” needles or scales • Cones: scalesscales with seeds Seed Plants- Conifers

• Longest-lived trees - Bristlecone pine: 5,000y • Tallest tree – redwood 112 m • Most massive tree – sequoia – 11m wide Land Plants (Embryophytes) (Fig 29.4)

Chlorophyta Ancestral Alga

Nontracheophytes Protected Embryos Nonseed Tracheophytes Vascular tissue

Seeds Gymnosperms

Flowers Angiosperms

Flowering Plants Seed Plants - Angiosperms

•• HighlyHighly diversediverse plantplant phylumphylum •• DominantDominant formform ofof plantplant lifelife onon EarthEarth

•• BecauseBecause ofof differencesdifferences fromfrom otherother plantsplants Seed Plants - Angiosperms

PollinationPollination •• PollenPollen landslands onon stigmastigma,, ratherrather thanthan atat thethe tiptip ofof thethe ovuleovule •• ReducesReduces chancechance ofof selfself--pollinationpollination –– increasesincreases geneticgenetic diversitydiversity

Fig 30.7, 30.11 DoubleDouble fertilizationfertilization (producing(producing zygotezygote andand endosperm)endosperm) Endosperm Nucleus

•• FlowersFlowers andand fruitfruit areare uniqueunique featuresfeatures Seed Plants Angiosperms

•• FruitFruit andand stamensstamens evolvedevolved fromfrom leafleaf--likelike structures.structures. Seed Plants - Angiosperms

•• MuchMuch diversitydiversity isis relatedrelated toto pollinationpollination andand dispersaldispersal mechanisms.mechanisms. Seed Plants Angiosperms Review Land Plants (Fig 29.4)

Chlorophyta Ancestral Alga

Nontracheophytes Protected Embryos Nonseed Tracheophytes Vascular tissue

Seeds Gymnosperms

Flowers Plant Kingdom? Angiosperms Tracheophytes? Seed plants?