+ Chapter 18 Evolution of Plants and Fungi. + Plant Characteristics: Contain chlorophylls a and b...

+

Chapter 18Evolution of Plants and Fungi

+Plant Characteristics:

Contain chlorophylls a and b and various accessory pigments

Store excess carbohydrates as starch

Have cellulose in their cell wall

Meristem tissue Produces new cells / organs

Plasmodesmata Openings that allow for passage

Protection of zygote Pass nutrients and keep from drying out

Alternation of generations Sporophyte vs gametophyte

18-2

+Plants have an alternation of generations life cycle

2 multicellular individuals alternate, each producing the other Sporophyte represents the diploid generation (2n)

Produces spores by meiosis spore is a haploid reproductive cell that develops into a new

organism without needing to fuse with another reproductive cell spore undergoes mitosis to become a gametophyte

Gametophyte represents the haploid generation (n) Produces gametes In plants, eggs and sperm are produced by mitosis A sperm and egg fuse, forming a diploid zygote that undergoes

mitosis and becomes the sporophyte

18-3

+ 18-4

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

zygote (2n)

sporophyte (2n)

spore (n)

gametophyte (n)

(n)(n)

gametes

Mito

sis

Mitosis

Mitosis

sporangium (2n)

diploid (2n)

haploid (n)MEIOSISFERTILIZATION

+ size of the gametophyte is progressively reduced as the sporophyte becomes more dominant

18-5


Moss Fern Gymnosperm Angiosperm

roots

roots

roots

rhizoids

Gametophyte

(n)

Sporophyte

(2n)

seed seedspores spores

rhizoids

+Sporophyte anatomy

Cuticle Impermeable Barrier to water loss

Also to gas exchange

Stomata Openings to allow for gas exchange

18-6

+Embryophta – land plants

Nonvascular Bryophytes

Mosses Hornworts Liverworts

Vascular (tracheophytes) Seedless

Lycophytes Ferns

Seeds Gymnosperms Angiosperms (Flowering

plants )

18-7

+Bryophytes

Hornworts, liverworts, and mosses Prefer damp shaded areas Form a mat on ground Turn brown when dry but becomes green when watered again

First plants to colonize land

Successfully reproduce on land protect the embryo and produce wind-blown spores

No true roots, stems, or leaves – no vascular tissue Non-vascular plants

18-8

+Bryophytes

Bryophyte reproduction Gametophyte is the dominant generation Female gametophyte produces eggs in archegonia Male gametophyte produces flagellated sperm in antheridia Following fertilization, the zygote becomes a sporophyte

Sporophyte attached to, and derives its nourishment from, the photosynthetic gametophyte

18-9

+18-10


(top): © Peter Lilja/Getty Images; (bottom): © Steven P. Lynch

zygote

spermegg

Archegonia

Antheridia

Spores

Sporangium

Gametophytes

buds

Mitosis

Mitosis

haploid (n)

diploid (2n)

1

2

5

6

Developing sporophyte: The sporophyte embryo is retained within the archegonium, where it develops, becoming a mature sporophyte.

developingsporophyte

Fertilization: Flagellated sperm produced in antheridia swim in external water to archegonia, each bearing a single egg.

The maturegametophytes:In mosses, thedominantgametophyte shootsbear either antheridiaor archegonia, wheregametes areproduced by mitosis.

Spore dispersal: Spores are released when they are most likely to be

dispersed by air currents.

The immature gametophyte: A spore germinates into the first stage of the male and the female gametophytes.

3

archegonium

antheridium

The sporophyte: The dependent sporophyte has a foot buried in female gametophyte tissue, a stalk, and an upper capsule (the sporangium), where meiosis occurs and windblown spores are produced.

4

MEIOSISFERTILIZATION

Sporophyte

stalk

foot (n)

+Vascular Plants

Have vascular tissue Xylem transports water

Contain lignin to strengthen cell walls Phloem transports nutrients

First vascular plants were like Cooksonia Rhyniophyte that flourished during Silurian period No roots or leaves Example of seedless vascular plant

Like lycophytes and ferns

18-11

+Transport begins in both the leaves and the roots of plants

Xylem Carries water and minerals from the roots to the

leaves Contain 2 types of nonliving conductive cells

Tracheids allow water to pass between

Vessel elements perforation plates at each end form a completely hollow pipeline from roots

to leaves

22-12

+Transport begins in both the leaves and the roots of plants

Phloem Transports sugar to all parts of the plant Composed of several cell types

Sieve-tube members living conducting cells, contain cytoplasm but

have no nucleus Companion cells

provide proteins to sieve-tube members

Water is a large part of xylem sap and phloem sap

22-13

A plant΄s transport system

blue = phloem; pink =sugar; red = xylem; light blue = water


O2

xylemphloemstoma

CO2

Phloem is transporting sugarfrom the leaf to the root.

H2O

watersugar

H2Osugar

+Lycophytes

Lycophytes or club mosses True stems, leaves, and roots Leaves are microphylls

Only 1 strand of vascular tissue Sporophyte is dominant, as it is in all vascular plants Today there are 3 groups

Ground pines (Lycopodium) Spike mosses (Selaginella) Quillworts (Isoetes)

18-15

+18-16


sporophyll

sporangiastrobili

branches

aerial stem

rhizome

root

Leaf

Strobilusleaves(microphylls)

Root

stoma

vascular tissue

phloemxylem

+Ferns

seedless vascular plants

Have megaphyllsBroad leaves with

several strands of vascular tissue

Allow plants to collect more solar energy

18-17

+

Microphylls and megaphylls18-18


a. Microphyll Megaphyll

b. Megaphyll evolution process

branchedvascular tissue

single strand ofvascular tissue

branchedstem system

megaphyllleaf

Tissue filled in the spacesbetween the side branches.

The side branches flattenedinto a single plane.

One branch began todominate the stem system.

+Ferns

Whisk ferns Psilotum and

Tmesipteris Epiphytes

Plants that live on/in trees

No leaves

18-19


rhizome

sporangium

aerial stem

scale

root

(Left): © CABISCO/Phototake

+Ferns

Ferns 11,00 species Megaphylls called

fronds Leaves first appear as

fiddleheads 2 generations separate

and independent

18-20


Cinnamon fern, Osmunda cinamomea

frond(undivided)

Hart’s tongue fernCampyloneurum scolopendrium

Maidenhair fern,Adiantum pedatum

spores onfertile frond

axis

leaflet

(cinnamon fern): © James Randklev/Getty Images; (hart's tongue): © Walter H. Hodge/Peter Arnold/Photolibrary; (maidenhair): © Jeff Foott/Getty Images

frond(divided)

+Fern life cycle 18-

21Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Sporophyte

fiddlehead roots

frond

Sporangium

sperm

Antheridium

egg

Archegonium

Gametophyte

Spores

zygote

leaflet

Sorus

sporangium

MEIOSIS

Dryopterus

Mitosis

Mitosis

haploid (n)

diploid (2n)

5

6

4

3

2

1 The sporophyte: The sporophyte is dominant in ferns.

Young sporophyte:The sporophyteembryo developsinside anarchegonium. As the distinctivefirst leaf appearsabove thegametophyte, and as the roots develop below it,the young sporophyte becomes visible.

young sporophyteon gametophyte

FERTILIZATION

The sporangia:In this fern, thesporangia arelocated within sori(sing., sorus) onthe underside of the leaflets.

The spores:Within asporangium,meiosis occursand spores areproduced. When asporangium opens,the spores arereleased.

germinatingspore

The gametophyte:A spore germinates into aheart-shaped gametophyte,which typically bears archegoniaat the notch and antheridia at thetip between the rhizoids.

Fertilization: Fertilization takes place when moisture is present, because the flagellated sperm must swim in a film of water from the antheridia to eggs within archegonia.

(Top right): © Matt Meadows/Peter Arnold/Photolibrary

Sori

+Seed Plants

Evolution of the seed was the next significant innovation in the evolution of plants

Gymnosperms and angiosperms are seed plants

Seed contains a sporophyte generation, along with stored food, within a

protective seed coat

Ability of seeds to survive harsh conditions until the environment is again favorable for growth largely accounts for the dominance of seed plants today

18-22

+Gymnosperms

Seeds are naked

Diversity of Gymnosperms Four groups of living gymnosperms: cycads, ginkgoes, gnetophytes,

and conifers All have ovules and develop seeds that are exposed on the surface

of cone scales or analogous structures

Conifers Consist of about 575 species of trees

Many are evergreens such as pines, spruces, firs, cedars and hemlocks

Economic Value of Conifers Wood of conifers is used extensively in construction

18-23

+ Pine life cycle18-24


Pollen sac

Seedstored food

seed coat

zygote

seed wing

Sporophyte

pollen cone scale

Seed cones

seed cone scale

Pollen cones

sperm

pollen tube

egg

Mature female gametophyte

Pollen grain

Pollination

Megaspores

Microspores

pollen grain

Megaspores:Megaspore mother cellin ovule undergoesmeiosis to producemegaspores.Onemegaspore willbecome theegg-producing

The pollen grain:The pollen grain has two wings and is carried by thewind to the seed cone during pollination

Mature male gametophyte

200 µm

MEIOSIS MEIOSIS

Ovule

Ovule

Mitosis

Mitosis

Mitosis

haploid (n)

diploid (2n)

3

4

5

1

2

FERTILIZATION

The sporophyteembryo:Afterfertilization, theovule matures andbecomes the seedcomposed of theembryo, reservefood, and a seedcoat. Finally, in thefall of the secondseason, the seedcone, bynow woody andhard, opens torelease wingedseeds. Whena seed germinates,the sporophyte

sporophyteembryo

Fertilization:Once a pollen grainreaches a seed cone,it becomes a maturemale gametophyte.A pollen tube digestsits way slowlytoward a femalegametophyte anddischargesnonflagellated sperm. The fertilizedegg isa zygote.

ovulewall

megasporemother cell

microsporemother cell

The pollen cones:Typically, the pollencones are quite smalland develop near thetips of lowerbranches.

The seed cones: The seed cones arelarger than the pollencones and are locatednear the tips of higherbranches.

Microspores:Microspore mothercells undergo meiosisto producemicrospores. Eachmicrospore becomes apollen grain.

(Bottom right): © Phototake

+Angiosperms

Seeds are covered

Angiosperms are flowering plants Evolved some 200 MYA Innovations are flower and fruit 240,000 known species Ovules always enclosed within sporophyte tissue

Angiosperm Diversity Monocotyledones (or monocots) – One cotyledon Eudicotyledones (or eudicots) – Two cotyledons Cotyledons – seed leaves with nutrients that nourish the

embryo

18-25

+

Shoot system – stem, branches, leaves, and flowers (organs of sexual reproduction)

Root system – main root and its branches

21-26

stem

internode

petiole

axillary bud

terminal bud

node

Shoot systemRoot system

node

leaf blade

root tip

vascular tissues(xylem and phloem)

lateralbranchrootroothairs

primaryroot


+Flowering plants typically have roots, stems, and leaves

Roots 3 main functions

1. Anchor plant in soil2. Absorb water and minerals from soil3. Produce hormones Some also store food

Root hairs increase surface-to-volume ratio

Tap roots vs. fibrous roots

21-27

+21-28Taproot system (left) versus fibrous root system (right)

(taproot): © Jonathan Buckley/Getty Images;; (fibrous root): © The McGraw-hill companies Inc./Evelyn Jo Johnson, photographer


Taproot Fibroous root system

+Flowering plants are either monocots or eudicots

Monocots have one cotyledon Root vascular tissue rings pith Vascular bundles scattered in stem Leaf veins are parallel Flower parts in multiples of three

Eudicots have two cotyledons Root phloem between arms of xylem Vascular bundles in a distinct ring Leaf veins form a net pattern Flower parts in multiples of four or five

21-29

+21-30Monocots and eudicots differ structurally in several ways


Mo

no

cots

Eu

dic

ots

Two cotyledons in seedRoot phloem between

arms of xylemVascular bundlesin a distinct ring

Leaf veins forma net pattern

Flower parts in fours orfives and their multiples

axillary bud

pith

xylem

phloem

One cotyledon in seed

xylem

Seed Root Stem Leaf Flower

endosperm phloempith

Root xylem andphloem in a ring

Vascular bundlesscattered in stem

axillary bud

Flower parts in threesand multiples of three

Leaf veins forma parallel pattern

+Fruits and Seeds

Advantage of fruit Fruits of flowers aid in dispersal of seeds Eaten by animals

Then transport seeds

Advantage of seeds Dry environment 129 years!! Endosperm of seed provide nourishment

Helps new plant until photosynthesis begins

18-31

+ Generalized flower18-32


petals (corolla) sepals (calyx)

stamens

anther

filament

receptacle

stigma

ovary

ovule

style

pollentube

carpel

Flowering plant life cycle

18-33


ovary

stigma

style

Megaspores

sperm

pollen tube

Microspores

(mature male gametophyte)Pollen grain

Embryo sac

(mature female gametophyte)

Pollination

polar nuclei

ovule wall

egg

Seed

endosperm (3n)

sporophyte embryo

seed coat

SporophyteAnther

egg

polar nuclei

Stamen Carpel

stigmastyleovaryovule

filamentanther

MEIOSIS MEIOSIS

sperm

ovule

The mature male gametophyte:A p[ollen grain that lands on the carpel of the same typeof plant germinates and produces a pollen tube,which delivers two nonflagellated sperm to the femalegametophyte. A fully germinated pollen grain is themature male gametophyte.

Mitosis

Mitosis

Mitosis

Ovule

diploid (2n)

haploid (n)

Carpel

Double Fertilization

receptacle

3

4

5

6

1

2

The stamen:An anther at the top of eachstamen has four pollen sacs.

The carpel:The ovary at the base of acarpel contains one or moreovules. The contents of anovule change during theflowering plant life cycle.

pollensac

microsporemother cell megaspore

mother cell

degeneratingmegaspores

Microspores:Microspore mother cells undergo meiosis to producemicrospores. Each microspore becomes a pollen grain.

Megaspores:Megaspore mother cell inside ovule undergoes meiosis toproduce megaspores. One megaspore will become theegg-producing female gametophyte.

pollentube

FERTILIZATION

The mature female gametophyte:The ovule now contains the mature femalegametophyte (embryo sac), which typically consists of eight haploid nuclei embedded in a mass of cytoplasm. The cytoplasm differentiates into cells, one of which is an egg and another of which contains two polar nuclei.

Double fertilization: On reaching the ovule, thepollen tube discharges thesperm. One of the two spermmigrates to and fertilizes theegg, forming a zygote; theother unites with the twopolar nuclei, producing a 3n(triploid) endosperm nucleus.The endosperm nucleusdivides to form endosperm,food for the developing plant.

The seed:The ovule now develops intothe seed, which contains anembryo and food enclosedby a protective seed coat.The wall of the ovary andsometimes adjacent partsdevelop into a fruit thatsurrounds the seed(s).

The sporophyte embryo:The embryo within a seedis the immature sporophyte.When a seed germinates,growth and differentiationproduce the maturesporophyte of a floweringplant.

fruit(mature ovary)seed(mature ovule)

+Adaptations of plants help them acquire nutrients

Root Nodules Some plants, such as legumes, soybeans, and alfalfa, have roots

colonized by Rhizobium bacteria Rhizobium can reduce atmospheric nitrogen (N2) to NH4

+ for incorporation into organic compounds

Mycorrhizae Involves fungi and almost any type of plant root Fungus increases the surface area available for mineral and water

uptake and breaks down organic matter in soil

22-34

+Mycorrhizae result in better growth 22-

35


Mycorrhizae present

Mycorrhizae not present

mycorrhizae

(plants, top): © Runk/Schoenberger/Grant Heilman Photography; (mycorrhizae, circle): © Dana Richter/Visuals Unlimited

+

Parasitic plants, such as dodders, broomrapes, and pinedrops, send out rootlike projections called haustoria that tap into the xylem and phloem of the host stem

22-36

© Kevin Schafer/Corbis


dodder(brown)

+

Carnivorous plants, such as the Venus flytrap and the sundew, digest insects as a source of nitrogen

By-pass need for nitrates from soil which may be lacking

22-37


bulbs releasedigestive enzymes

stickyhairs

narrowleafform

Sundew leafenfolds prey

(sundew leaf, prey): © Dr. Jeremy Burgess/Photo Researchers, Inc .

+

Fungi

+ Fungi

– Yeasts and molds• Single-celled, microscopic

– Mushrooms• Multicellular, macroscopic

– Cell nucleus and other cellular structures

– Absorb nutrients from their environment

– Saprobes – Widely distributed in water and soil

+Fungi

Thermal dimorphism grow as molds at 30°C Grow as yeasts at 37°C

18-40

Fungal Organization - Mold

Fungal Cell StructureHyphae

MyceliumConidia / sporesSexual and asexual

reproductionCell wallsCell walls contain chitin Energy reserve is glycogen Nonmotile

Produce wind-blown sporesGrow toward food source

Fungal Organization

Yeasts Soft, uniform texture and

appearance

Unicellular (bicellular) False hyphae Beta-glycan cell wall

structure

+Fungi have mutualistic relationships with algae and plants

In a mutualistic relationship, two different species live together and help each other out Mycorrhizal fungi form mutualistic relationships (mycorrhizae) with

the roots of most plants Helps plants grow more successfully in dry or poor soils

particularly those deficient in inorganic nutrients

Lichen – a mutualistic association between a particular fungus and a cyanobacteria or green algae Fungal partner is efficient at acquiring nutrients and moisture Organic acids given off by fungal partner can be used by

photosynthetic partner

18-43

+Land fungi occur in three main groups

Zygospores

Ascospores

Basidiospores

18-44

+

Zygospore Fungi Mainly saprotrophs,

but some are parasites

18-45

Black bread mold, Rhizopus stolonifer


zygospore

sporangium

mycelium

+

MEIOSIS2nn

34

Sexualreproduction

Asexualreproduction

1

2

(top left): © Runk/Schoenberger/Grant Heilman Photography

FERTILIZATION

–germinatingspores

5

1

+

Sac Fungi Nearly 75% of all

described fungal species

Name from ascus Yeast – unicellular

forms mainly in Ascomycota

No more Deuteromycota – use molecular data

18-46


(cup fungi): © Felix Labhardt/Getty RF; (morel): © Robert Marien/Corbis RF

meiosis

Ascocarp of the cup fungus Sarcoscypha

Cup fungi

Morel

ascocarp

ascocarp

ascospores

male organ

female organ

nuclearfusion zygote

(2n)matureascus

dikaryotichyphae

+ mating type (n)spore

– mating type (n)spore

+

Club Fungi Name comes from the

reproductive structure, the basidium

The basidia are located within a basidiocarp

When you eat a mushroom, you are eating a basidiocarp

18-47


basidiocarp

fusion meiosis

Sexual reproduction

spores

nuclei inbasidium

gill ofmushroom

+-

+Land Fungi Have Economic and Medical Importance

Economic Importance Help produce medicines and many foods

Mold Penicillium was original source of penicillin Excellent low-calorie meat substitute containing lots of

vitamins Fungal pathogens are a major concern for farmers

Medical Importance Certain mushrooms are poisonous Mycoses are diseases caused by fungi

Candida albicans Ringworm Aspergillus

18-48

+ Chapter 18 Evolution of Plants and Fungi. + Plant Characteristics: Contain chlorophylls a and b...

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Transcript of + Chapter 18 Evolution of Plants and Fungi. + Plant Characteristics: Contain chlorophylls a and b...