Today: - Algal Wrap-up - Life on Land: Challenges & Adaptations - Evolution of Land Plants -...

Today:Today:- - Algal Wrap-upAlgal Wrap-up- - Life on Land: Challenges & AdaptationsLife on Land: Challenges & Adaptations- Evolution of Land Plants- Evolution of Land Plants- Nontracheophytes (Bryophytes)- Nontracheophytes (Bryophytes)- Into the Lab- Into the Lab

The Algae: Where We Left OffThe Algae: Where We Left Off

Named for their color (from Named for their color (from carotene and xanthophyll carotene and xanthophyll accessory pigments)accessory pigments)

Typically biflagellated and Typically biflagellated and unicellularunicellular

May be mixotrophic May be mixotrophic (absorption/ingestion in (absorption/ingestion in addition to photosynthesis)addition to photosynthesis)

1.1. The Heterokont Algae- Golden The Heterokont Algae- Golden Algae (Chrysophytes)Algae (Chrysophytes)

Prymnesium parvum, the golden alga

responsible for many fresh water fish kills.

Photo: Dr. Carmelo TomasU. of North Carolina, Wilmington

Multicellular, primarily Multicellular, primarily marinemarine

Largest and most Largest and most complex of all algae complex of all algae (“seaweed”)(“seaweed”)

Complex anatomy Complex anatomy evolved evolved independentlyindependently of of plants (analogous, not plants (analogous, not homologous)homologous)

1.1. The Heterokont Algae- The Heterokont Algae- Brown Algae (Phaeophyta)Brown Algae (Phaeophyta)

Anatomy of Anatomy of the Brown the Brown

Algae Algae (Phaeophyta)(Phaeophyta)

Blade

Stipe

Holdfast

Pneumatocyst

The body of a seaweed is called a thallus

The The Heterokont Heterokont

Algae- Brown Algae- Brown Algae Algae

(Phaeophyta): (Phaeophyta): Life Cycle Life Cycle

Note the heteromorphic generations!

2. The Red Algae 2. The Red Algae (Rhodophyta)(Rhodophyta)

No flagellated stages!No flagellated stages! Usually red colored Usually red colored

because of an because of an accessory pigment, accessory pigment, phycoerythrin (similar phycoerythrin (similar to those in to those in cyanobacteria!)cyanobacteria!)

Plastids of red algae Plastids of red algae most likely evolved most likely evolved from cyanobacteria by from cyanobacteria by primary endosymbiosisprimary endosymbiosis

Mostly marine (Mostly marine (deep! deep! Why?Why?), but may be ), but may be freshwater, or even in freshwater, or even in moist soilsmoist soils

Mostly multicellularMostly multicellular Complex life cycles; Complex life cycles;

dependent on water dependent on water currents to bring gametes currents to bring gametes togethertogether

2. The Red Algae 2. The Red Algae (Rhodophyta)(Rhodophyta)

The Green Algae The Green Algae (Chlorophytes)(Chlorophytes)

3. The Green Algae (Chlorophyta)

Unicellular, colonial, or Unicellular, colonial, or multicellularmulticellular

Primarily freshwater, Primarily freshwater, but also marine, in but also marine, in soils, and symbiotic soils, and symbiotic relationships (lichens!)relationships (lichens!)

Share a common Share a common ancestor with land ancestor with land plants!plants! The Unicellular green

algae, Chlamydomonas


Isogamy!

Mechanisms for the evolution of size and complexity:Mechanisms for the evolution of size and complexity:

1.1. Formation of Formation of coloniescolonies of individual cells ( of individual cells (VolvoxVolvox))

2.2. Repeated division of nuclei without cytoplasmic Repeated division of nuclei without cytoplasmic division (division (multinucleate filamentsmultinucleate filaments))

3.3. Formation of true multicellular forms by Formation of true multicellular forms by cell cell division and differentiationdivision and differentiation ( (UlvaUlva))


Life Cycle Life Cycle of the of the Green Green Alga, Alga, UlvaUlva

Note the isomorphic generations

!

Life on Land:Life on Land:

Advantages?Advantages?

Challenges?Challenges?

Adaptations?Adaptations?

Evolution Evolution of Land of Land

Plants: A Plants: A PreviewPreview

The The BryophytesBryophytesThe Liverworts, The Liverworts, Hornworts, and Hornworts, and

MossesMosses

Bryophyte Bryophyte adaptations include adaptations include

offspring that offspring that develop from develop from multicellular multicellular

embryos embryos attached to the attached to the “mother” plant“mother” plant

The PterophytesThe Pterophytes

The Pterophytes The Pterophytes include the include the

lycophytes, ferns, lycophytes, ferns, horsetails and whisk horsetails and whisk

fernsferns

Pterophytes posses Pterophytes posses true vascular true vascular

tissuetissue (cells joined (cells joined into tubes to into tubes to

transport water and transport water and nutrientsnutrients

The The GymnospermsGymnospermsThe Gymnosperms The Gymnosperms include in ginkgos, include in ginkgos,

cycads, gnetae, cycads, gnetae, and conifersand conifers

Gymnosperms have Gymnosperms have “naked seeds”“naked seeds”

(plant embryo (plant embryo packaged with a packaged with a

food supply within food supply within a protective coat)a protective coat)

The AngiospermsThe Angiosperms

Angiosperms have Angiosperms have complex reproductive complex reproductive structures (structures (flowersflowers) )

that bear seeds that bear seeds within protective within protective

chambers (chambers (ovariesovaries))


Plants: A Plants: A PreviewPreview

Plant PhylaPlant Phyla

Probable Ancestors: CharophyceansProbable Ancestors: Charophyceans

Like many algae, plants Like many algae, plants are multicellular, are multicellular,

eukaryotic, eukaryotic, photosynthetic photosynthetic

autotrophsautotrophs

Like some algae, cell Like some algae, cell walls are made of walls are made of

cellulose, use cellulose, use chlorophylls chlorophylls aa and and bb

Charophyceans and Land Plants:Charophyceans and Land Plants:Shared FeaturesShared Features

Plasma membranes of both have rose-Plasma membranes of both have rose-shaped arrays of proteins that synthesize shaped arrays of proteins that synthesize cellulose microfibrils (cellulose microfibrils (rosette cellulose-rosette cellulose-synthesizing complexessynthesizing complexes))

Enzyme composition within the Enzyme composition within the peroxisomesperoxisomes

In land plants with flagellated sperm, the In land plants with flagellated sperm, the sperm sperm resemble those of the resemble those of the charophyceanscharophyceans

Formation of the cell wallFormation of the cell wall during during cytokinesis is similarcytokinesis is similar

1. Apical 1. Apical Meristems-Meristems- localized regions localized regions of cell division at of cell division at the tips of roots the tips of roots and shootsand shoots

Land Plants:Land Plants:Unique Terrestrial AdaptationsUnique Terrestrial Adaptations

2. Multicellular, 2. Multicellular, Dependent Dependent Embryos: Embryos: develop develop from zygotes retained from zygotes retained within tissues of the within tissues of the female parentfemale parent

Parental tissues provide Parental tissues provide nutrients through nutrients through placental transfer placental transfer cellscells


3. Alternation of 3. Alternation of generations: generations: two multicellular two multicellular body forms body forms alternate alternate generations generations (occurs in algae, (occurs in algae, but not the but not the charophyceans)charophyceans)


3. Alternation of generations: 3. Alternation of generations:

Evolved through a delay in meiosis?Evolved through a delay in meiosis?


4. Walled Spores: 4. Walled Spores: produce haploid produce haploid reproductive cells reproductive cells by mitosis; walls by mitosis; walls of plant spores of plant spores tough and tough and resistant due to resistant due to the presence of the presence of sporopolleninsporopollenin


5. Multicellular 5. Multicellular Gametangia: Gametangia: gametes produced gametes produced within multicellular within multicellular organs called organs called gametangiagametangia

Female = Female = archegoniaarchegonia

Male = Male = antheridiaantheridia


Cuticle-Cuticle- waxy layer waxy layer coating the epidermis; coating the epidermis; protects against protects against microbial attack and microbial attack and water losswater loss

Stomata-Stomata- pores in the pores in the epidermis of leaves epidermis of leaves (photosynthetic organs); (photosynthetic organs); allow for the exchange allow for the exchange of carbon dioxide and of carbon dioxide and oxygenoxygen

Land Plants: Miscellaneous Land Plants: Miscellaneous Terrestrial AdaptationsTerrestrial Adaptations

Vascular tissues-Vascular tissues- except except for bryophytes, have for bryophytes, have specialized tissue for specialized tissue for transport:transport:XylemXylem- tube shaped dead - tube shaped dead conducting cells, transport conducting cells, transport water and minerals up water and minerals up from rootsfrom rootsPhloemPhloem- living tissue, - living tissue, distributes sugars amino distributes sugars amino acids and other organic acids and other organic productsproducts


Secondary Secondary Compounds-Compounds- many many plants produce unique plants produce unique molecules as products of molecules as products of secondary metabolic secondary metabolic pathwayspathways

Ex. Alkaloids, terpenes, Ex. Alkaloids, terpenes, tannins, and phenolicstannins, and phenolics Protect plants against Protect plants against

herbivores, UV, pathogensherbivores, UV, pathogens May act as signaling May act as signaling

moleculesmolecules


One last One last word of word of caution:caution:

A Closer Look: The A Closer Look: The BryophytesBryophytes

Three Phyla:Three Phyla:

LiverwortsLiverworts (Hepatophyta)(Hepatophyta)

HornwortsHornworts (Anthocerophyta)(Anthocerophyta)

MossesMosses (Bryophyta) (Bryophyta) Not monophyletic! Not monophyletic!

Diverged independently Diverged independently early in plant evolutionearly in plant evolution

Evolution Evolution of Non-of Non-vascular vascular PlantsPlants

In all three phyla, In all three phyla, gametophytes are gametophytes are dominant!dominant!

Most bryophytes Most bryophytes lack conducting lack conducting tissues (those that tissues (those that do have do have conducting tissue conducting tissue lack lignin in the lack lignin in the cell walls)cell walls)

The BryophytesThe Bryophytes

The Bryophyte, Polytrichum, a moss

Terminology:Terminology:Germinating moss spores Germinating moss spores

produce a mass of one-produce a mass of one-cell-thick filaments cell-thick filaments called a called a protonemaprotonema

With sufficient resources, With sufficient resources, a protonema produces a a protonema produces a bud with bud with meristemsmeristems

Meristems generate the Meristems generate the gametophoregametophore


Terminology:Terminology:Most bryophytes grow close Most bryophytes grow close

to the ground, to the ground, anchoredanchored by by rhizoidsrhizoids

Eggs are produced singly in Eggs are produced singly in archegoniaarchegonia; large ; large numbers of sperm are numbers of sperm are produced in produced in antheridiaantheridia

Flagellated sperm swim Flagellated sperm swim through water films through water films toward eggs!?toward eggs!?


Terminology:Terminology:Dependent Dependent

sporophytessporophytes disperse disperse huge numbers of huge numbers of sporesspores


Peristome

A Moss A Moss LifecycleLifecycle Dioecious-

“two houses”

A Moss A Moss LifecycleLifecycle

Pop Quiz: Find a Bryophyte!Pop Quiz: Find a Bryophyte!

Do you have the…

Gametophyte?

Sporophyte?

Is it…

Haploid?

Diploid?

Other Interesting MossesOther Interesting MossesLuminous moss is Luminous moss is

often found often found near cave near cave entrances. The entrances. The upper surfaces upper surfaces of the cells are of the cells are curved, curved, magnifying dim magnifying dim light on the light on the chloroplasts at chloroplasts at the base.the base.

Main entrance to the Ape Caves, Mt. St. Helens

The Bryophytes ContinuedThe Bryophytes ContinuedWidely dispersed and Ecologically Important:Widely dispersed and Ecologically Important:

Wind dispersal of lightweight spores Wind dispersal of lightweight spores (succession!)(succession!)

Tolerate desiccation very well! (The Tolerate desiccation very well! (The amphibians of the plant world)amphibians of the plant world)

Phenolic secondary compounds absorb UVPhenolic secondary compounds absorb UV

Strange Things Turn Up In Peat Strange Things Turn Up In Peat Moss BogsMoss Bogs

Photo: PBS, “Mummies 101”; 400BC-400AD

Most mosses disperse Most mosses disperse their spores through their spores through

wind. Spores are wind. Spores are released through the released through the

peristome (often peristome (often sensitive to humidity!) sensitive to humidity!)

Weird Exceptions: Dung Weird Exceptions: Dung mosses produce nasty mosses produce nasty odors that attract flies. odors that attract flies. Their spores are sticky!Their spores are sticky!

Moss DispersalMoss Dispersal

Asexual reproduction via Asexual reproduction via fragmentation also fragmentation also

facilitates dispersal. facilitates dispersal.

One study collected One study collected bryophyte fragments in bryophyte fragments in

the Canadian high arctic: the Canadian high arctic: 12% of their samples 12% of their samples resumed growth in the resumed growth in the lab. (each cubic meter lab. (each cubic meter

of snow contained of snow contained >4,000 bryophyte >4,000 bryophyte

fragments)fragments)

Moss DispersalMoss Dispersal

Drought-Tolerant MossesDrought-Tolerant MossesMany species of moss can survive drastic Many species of moss can survive drastic

plasmolysis. Rehydrated plants repair plasmolysis. Rehydrated plants repair most internal damage within minutes most internal damage within minutes (drought repair genes!). Respiration (drought repair genes!). Respiration resumes in minutes; photosynthesis resumes in minutes; photosynthesis

resumes within 24 hours!resumes within 24 hours!Scientists at the USDA are eager to learn more about

these drought resistant genes!

GrimmiaGrimmia, a , a rock moss, rock moss, capable of capable of surviving surviving on bare on bare rocks, rocks, often in often in direct sundirect sun

Drought-Tolerant MossesDrought-Tolerant Mosses

LiverwortsLiverworts

The most The most common common liverworts have liverworts have broad, flattened broad, flattened leaf-like bodies. leaf-like bodies. (the(the thalloid thalloid liverworts)liverworts)Marchantia, a common

thalloid liverwort reproducing sexually (above) and asexually

(below).

Horn WortsHorn Worts

Looking Looking Ahead:Ahead:

The The Evolution Evolution

of Vascular of Vascular PlantsPlants

Vascular Plant Evolution- Vascular Plant Evolution- ReviewReview

From their bryophyte-like From their bryophyte-like ancestors, inherit:ancestors, inherit:

Tissue-producing meristemsTissue-producing meristems GametangiaGametangia Embryos and the Embryos and the

sporophytes that develop sporophytes that develop from themfrom them

StomataStomata CuticlesCuticles Sporopollenin-walled sporesSporopollenin-walled spores

The Vascular Plants: Major The Vascular Plants: Major ChangesChanges

Have true vascular Have true vascular tissue (phloem and tissue (phloem and xylem)xylem)

Dominant sporophyte Dominant sporophyte generationgeneration

Branched sporophytesBranched sporophytes Earliest vascular Earliest vascular

plants are seedlessplants are seedless

zygote

SPOROPHYTE (2n)

GAMETOPHYTE (n)

GREEN ALGA BRYOPHYTE FERN GYMNOSPERM ANGIOSPERM

Plant Evolution: Major Trends

Two Modern Phyla of Seedless Two Modern Phyla of Seedless Vascular Plants:Vascular Plants:

1. Lycophyta1. Lycophyta (lycophytes)(lycophytes)

2.2. PterophytaPterophyta (ferns, whisk (ferns, whisk ferns, and ferns, and horsetails)horsetails)

Lycopodium: Phylum Lycophyta

Origins of the Vascular SystemOrigins of the Vascular System

Most pterophytes Most pterophytes have true roots with have true roots with lignified vascular lignified vascular tissuetissue

Roots resemble the Roots resemble the stems of early stems of early vascular plants!vascular plants!

What does this suggest?What does this suggest?

Lycophytes have Lycophytes have small leaves with a small leaves with a single, unbranched single, unbranched vein (vein (microphyllsmicrophylls))

Evolved from tissue Evolved from tissue flaps on the stem?flaps on the stem?


Larger leaves with branching vascular Larger leaves with branching vascular system are called system are called megaphyllsmegaphylls


Evolution of branched stems before large leaves and roots?

A Sporophyte-Dominant Life Cycle:A Sporophyte-Dominant Life Cycle:

Spore Terminology in the Spore Terminology in the Pteridophytes:Pteridophytes:

A A homosporoushomosporous plant produces one type of plant produces one type of sporespore

A A heterosporous heterosporous plant produces two types plant produces two types of spores: of spores: Megaspores Megaspores and and MicrosporesMicrospores

Develop into female

gametophytes bearing

archegoniaDevelop into male

gametophytes with antheridia

Onto The Onto The Vascular Vascular Plants: Plants:

SpecificsSpecifics

Phylum LycophytaPhylum Lycophyta

The lycophytes (also called club The lycophytes (also called club mosses or ground pines) mosses or ground pines) originally consisted of 2 groups:originally consisted of 2 groups:

Small herbaceous Small herbaceous plantsplantsandand

Giant woody treesGiant woody trees

Giant Lycophytes are Giant Lycophytes are extinct!extinct!

An artist’s vision of a An artist’s vision of a forest of giant forest of giant lycophytes (during lycophytes (during a storm). These a storm). These giant “trees” (30+ giant “trees” (30+ meters) were a meters) were a dominant dominant component of the component of the forests of the late forests of the late Carboniferous Carboniferous (~300 mya) (~300 mya)

from Life Before Man by Zdenek V. Spinar, illustrated by Zdenek Burian

Phylum Pterophyta (Ferns and Phylum Pterophyta (Ferns and Their Relatives):Their Relatives):

Three Major Groups:Three Major Groups:

1. The Psilophytes 1. The Psilophytes (whisk ferns)(whisk ferns)

lack true leaves and lack true leaves and roots (evolved roots (evolved secondarily?)secondarily?)

may be terrestrial or may be terrestrial or epiphyticepiphytic


2. The Sphenophytes 2. The Sphenophytes (horsetails)(horsetails)

Also larger and more Also larger and more diverse during the diverse during the Carboniferous periodCarboniferous period

Common in waterlogged Common in waterlogged soils (have internal air soils (have internal air canals)canals)


Horsetails: Abundant in the fossil record Horsetails: Abundant in the fossil record (also up to 30 m). Represented today (also up to 30 m). Represented today

by a single genus, by a single genus, Equisetum.Equisetum.

A Typical Horsetail LifecycleA Typical Horsetail Lifecycle


3. The “True” Ferns:3. The “True” Ferns:

most widespread and most widespread and diverse of the diverse of the pteridophytespteridophytes

large, extensively large, extensively branched vascular branched vascular systemssystems



Plants: A Plants: A ReviewReview

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