department of ecology and evolutionary biology 621-8220 … · 2006-01-26 · dr. mitch...

Dr. Mitch Pavao-ZuckermanDepartment of Ecology and Evolutionary Biology

621621--82208220mzuckermzucker@[email protected] hours: Biosciences West 431Office hours: Biosciences West 431W and F 1W and F 1--2 p.m. or by appointment2 p.m. or by appointment

Diversity of Plants

Diversity of Plants (Fig 29.4)

Ancestral Alga Chlorophyta

Nontracheophytes

Nonseed Tracheophytes

Gymnosperms

Angiosperms

The Transition to Life on Land

The Vascular PlantsThe Seed PlantsThe Flowering Plants

Monophyly•• Monophyletic groupMonophyletic group –– includes the includes the

most recent common ancestor and all most recent common ancestor and all decendentsdecendents

•• These are NOT monophyletic:These are NOT monophyletic:

Green PlantsGreen Plants((viridiphytesviridiphytes)) are a are a monophyletic groupmonophyletic group

•• Green PlantsGreen Plants include the include the Chlorophytes Chlorophytes (green algae)(green algae)

•• Other green algaeOther green algae•• and the land plantsand the land plants

EmbryophytesEmbryophytes (Land Plants)(Land Plants)

Land PlantsLand Plants are also a monophyletic groupare also a monophyletic group

•• PhotosyntheticPhotosynthetic eukaryotes that use eukaryotes that use chlorophyllchlorophyll aa and and bb and store and store carbohydrates carbohydrates starchstarch

•• Resting Resting embryoembryo with placental connection to with placental connection to the parent.the parent.

The Conquest of the LandHistory of plants on landHistory of plants on land•• 500 500 myamya -- a few algae and lichens.a few algae and lichens.•• By 460 By 460 myamya -- primitive primitive Land PlantsLand Plants, , •• By 425 By 425 myamya -- Early Early Vascular PlantsVascular Plants

were common were common

•• How did it happen?How did it happen?•• Obstacles?Obstacles?

Fossil

Reconstruction

The Conquest of the Land

2. thick spore wall2. thick spore wall

Early Early innovationsinnovations in land plant in land plant evolution: evolution:

1. cuticle (waxy coating) 1. cuticle (waxy coating)

3. Antheridia and archegonia 3. Antheridia and archegonia (gamete cases), (gamete cases),

4. protected embryo4. protected embryo

5. protective pigments 5. protective pigments –– flavonoidsflavonoidsabsorb damaging UV lightabsorb damaging UV light

Land Plants (Embryophytes) (Fig 29.4)


Nontracheophytes


Gymnosperms

AngiospermsPlant Kingdom?

Protected Embryos

Nontracheophytes:Liverworts, Hornworts, and Mosses

•• SmallSmall plants (compared to present day plants (compared to present day shrubs and trees)shrubs and trees)

•• Lack specialized water (xylem) and food Lack specialized water (xylem) and food conducting tubes (phloem) of vascular conducting tubes (phloem) of vascular plants.plants.

•• Rely on Rely on diffusiondiffusion of water and minerals.of water and minerals.

Diploid

Haploid

Plant life cycles feature alternation of generations (Fig 29.2)

Haploid (n)

Diploid (2n)

Fertilization

Zygote

Multicellular sporophyte

Meiosis

Spore

Multicellular gametophyte

Gametes

• Diploid generation is 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.

Nontracheophytes:Liverworts, Hornworts, and Mosses

Fig. 29.5

Liverworts (9,000 species)

•• Lack Lack stomatesstomates (pores with guard (pores with guard cells that regulate C02 uptake and cells that regulate C02 uptake and H20 loss).H20 loss).

•• Small spore producing diploid phase Small spore producing diploid phase compared to hornworts or mossescompared to hornworts or mosses

Hornworts (100 species)

•• Have Have stomates stomates •• HornHorn--shaped spore producing shaped spore producing

diploid stagediploid stage•• One large flat chloroplast per cellOne large flat chloroplast per cell

Mosses (15,000 species)

•• Have Have stomates stomates •• Spore producing upright diploid Spore producing upright diploid

stage with capsulestage with capsule•• Capsule has a lid and row of teeth Capsule has a lid and row of teeth

that release the spores in wet that release the spores in wet weather.weather.

a.a. They are all relatively smallThey are all relatively small

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

c.c. All possess stomata for gas exchangeAll possess stomata for gas exchange

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

What What is notis not a common feature of nona common feature of non--vascular plants?vascular plants?



Nontracheophytes

Nonseed TracheophytesNonseed Tracheophytes

GymnospermsGymnosperms

AngiospermsAngiosperms

Vascular Plants

(Tracheophytes)

Protected Embryos

Vascular tissue

Vascular Plants•• ThickThick--walled dead walled dead waterwater--conducting conducting

cellscells..more efficient water movementmore efficient water movementsupportsupport for tall plants.for tall plants.

Vascular Plants •• The The diploiddiploid generation became LARGERgeneration became LARGER and and

independent of the independent of the haploidhaploid generation.generation.

Figure 28.19

Figure 29.20Figure 29.20

Tracheophytes

•• The earliest The earliest tracheophytestracheophytes lacked lacked roots. roots.

•• Roots Roots –– possibly possibly evolved from branchesevolved from branches

Tracheophytes •• Simple leavesSimple leaves may have may have

evolved from the spore evolved from the spore producing structures. producing structures.

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

Difference?Difference?



Nontracheophytes

Nonseed TracheophytesNonseed Tracheophytes



Vascular Plants

(Tracheophytes)

Protected Embryos

Vascular tissue

Nonseed TracheophytesClub mosses 1,200 species

•• Simple leavesSimple leaves•• ConeCone--like structures with spores.like structures with spores.•• Dominated tropical coastal swamps in Dominated tropical coastal swamps in

Carboniferous period 300 Carboniferous period 300 myamya coalcoaldeposits.deposits.

•• SelaginellaSelaginella is common here in the desert.is common here in the desert.

Nonseed Tracheophytes Whisk Ferns 15 species•• Simple branchingSimple branching like ancient vascular plants. like ancient vascular plants. •• Tiny Tiny simple leavessimple leaves•• No true rootsNo true roots

Reconstruction of ancienttracheophyte

Tracheophytes Horsetails 15 species

•• Jointed hollow stems Jointed hollow stems •• Silica deposits (“scouring rush”)Silica deposits (“scouring rush”)•• Leaves in whorlsLeaves in whorls•• Spore sacsSpore sacs under “shields” on under “shields” on

“cones”“cones”

Nonseed Tracheophytes Ferns 12,000 species•• Big Big complex leavescomplex leaves with branching veins with branching veins •• SporesSpores in sacs clustered on the bottom of in sacs clustered on the bottom of

the leafthe leaf•• Leaves unfold from “fiddlehead”Leaves unfold from “fiddlehead”

••Tree ferns can reach 60 ftTree ferns can reach 60 ft

a.a. They are larger than nonThey are larger than non--vascular plantsvascular plants

b.b. They possess specialized cells for moving water and They possess specialized cells for moving water and foodfood

c.c. All possess stomata for gas exchangeAll possess stomata for gas exchange

d.d. The big generation is haploid (the The big generation is haploid (the gametophytegametophyte with with one set of chromosomes)one set of chromosomes)

What What is not is not a common feature of a common feature of Non-Seed Tracheophytes??



Nontracheophytes



AngiospermsAngiospermsSeed plants

Protected Embryos

Vascular tissue

Seeds

Seed Plants 300,000 species

•• The seed plants have greatly The seed plants have greatly reduced reduced haploid stagehaploid stage. .

•• How did this happen?How did this happen?

Fig 30.2


•• Further reduced haploid generation. Further reduced haploid generation.

Part of the evolution of Part of the evolution of seedsseedsand and pollen.pollen.

•• SeedsSeeds -- protected resting stage protected resting stage opening many possibilities, like opening many possibilities, like suspended animationsuspended animation..

••PollenPollen -- sperm delivery system; sperm delivery system; escape the need of water for escape the need of water for sperm to swim.sperm to swim.

How did seeds evolve?•• Ancestors of seed plants had one kind of spore.Ancestors of seed plants had one kind of spore.

Spore sac

•• First First dimorphicdimorphic spores evolved:spores evolved:MicrosporesMicrospores (grow into sperm producing haploid stage)(grow into sperm producing haploid stage)Megaspores Megaspores (grow into egg producing haploid stage)(grow into egg producing haploid stage)

•• Megaspores reduced to just one.Megaspores reduced to just one.

How did seeds evolve?•• Megaspore enveloped in a sac.Megaspore enveloped in a sac.

•• Female haploid stage grows in this “seed”.Female haploid stage grows in this “seed”.

•• It is attached to the diploid parent.It is attached to the diploid parent.

Pollen is a reduced male haploid stageDiploid

Spore sacHaploid Spores

Reduced haploid stage

Plant and flower are diploid

Pollination1.1. Pollen Pollen reduced haploid female. reduced haploid female. 2.2. Pollen produce sperm to fertilize an egg.Pollen produce sperm to fertilize an egg.3.3. The zygote develops into a seed embryo.The zygote develops into a seed embryo.


•• So, seed plants make seeds and So, seed plants make seeds and pollen pollen

•• Also make Also make woodwood..

•• Evolved ~ 370 Evolved ~ 370 myamya



Nontracheophytes


Gymnosperms


Protected Embryos

Vascular tissue

Seeds

Seed Plants - Gymnosperms

•• Gymnosperm = ‘naked seeded’Gymnosperm = ‘naked seeded’•• Do not have flowers or fruit tissueDo not have flowers or fruit tissue

Gymnosperms - 4 PhylaCycads Cycads GinkosGinkos

Gnetophytes Gnetophytes

Gymnosperms - Conifers

•• Leaves often “evergreen” needles Leaves often “evergreen” needles or scalesor scales

•• Cones: Cones: scalesscales with seedswith seeds

Seed Plants- Conifers •• LongestLongest--lived trees lived trees -- Bristlecone Bristlecone

pine: 5,000ypine: 5,000y•• Tallest tree Tallest tree –– redwood 112 mredwood 112 m•• Most massive tree Most massive tree –– sequoia sequoia –– 11m 11m

widewide



Nontracheophytes


Gymnosperms

Angiosperms

Flowering Plants

Protected Embryos

Vascular tissue

Seeds

Flowers

Seed Plants - Angiosperms

•• Highly diverse plant phylumHighly diverse plant phylum•• Dominant form of plant life on EarthDominant form of plant life on Earth

•• Because of differences from other plantsBecause of differences from other plants

Seed Plants - Angiosperms PollinationPollination•• Pollen lands on Pollen lands on stigmastigma, rather than at the , rather than at the

tip of the ovuletip of the ovule•• Reduces chance of selfReduces chance of self--pollination pollination ––

increases genetic diversityincreases genetic diversity

Fig 30.7, 30.11

Double fertilizationDouble fertilization (producing zygote and (producing zygote and endosperm)endosperm)

•• FlowersFlowers andand fruit fruit are unique featuresare unique features

Endosperm Nucleus

Seed Plants Angiosperms

•• Fruit and stamens Fruit and stamens evolved from leafevolved from leaf--like like structures.structures.

Seed Plants - Angiosperms

•• Much diversity is related to Much diversity is related to pollination pollination andanddispersal dispersal mechanisms. mechanisms.

Seed Plants Angiosperms

Review Land Plants (Fig 29.4)


Nontracheophytes


Gymnosperms

Angiosperms

Protected Embryos

Vascular tissue

Seeds

Flowers Plant Kingdom?

Tracheophytes?

Seed plants?

department of ecology and evolutionary biology 621-8220 … · 2006-01-26 · dr. mitch...

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