Today: - Life on Land: Challenges & Adaptations - Evolution of Land Plants - Nontracheophytes (Bryophytes) & Seedless Tracheophytes.
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Today:Today:- - Life on Land: Challenges & AdaptationsLife on Land: Challenges & Adaptations- Evolution of Land Plants- Evolution of Land Plants- Nontracheophytes (Bryophytes) & - Nontracheophytes (Bryophytes) & Seedless Seedless
TracheophytesTracheophytes
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))
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
Land Plants:Land Plants:Unique Terrestrial AdaptationsUnique Terrestrial Adaptations
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)
Land Plants:Land Plants:Unique Terrestrial AdaptationsUnique Terrestrial Adaptations
3. Alternation of generations: 3. Alternation of generations:
Evolved through a delay in meiosis?Evolved through a delay in meiosis?
Land Plants:Land Plants:Unique Terrestrial AdaptationsUnique Terrestrial Adaptations
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
Land Plants:Land Plants:Unique Terrestrial AdaptationsUnique Terrestrial Adaptations
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
Land Plants:Land Plants:Unique Terrestrial AdaptationsUnique Terrestrial Adaptations
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
Land Plants: Miscellaneous Land Plants: Miscellaneous Terrestrial AdaptationsTerrestrial Adaptations
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
Land Plants: Miscellaneous Land Plants: Miscellaneous Terrestrial AdaptationsTerrestrial Adaptations
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
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
The BryophytesThe Bryophytes
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!?
The BryophytesThe Bryophytes
Terminology:Terminology:Dependent Dependent
sporophytessporophytes disperse disperse huge numbers of huge numbers of sporesspores
The BryophytesThe Bryophytes
Peristome
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).
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?
Origins of the Vascular SystemOrigins of the Vascular System
Larger leaves with branching vascular Larger leaves with branching vascular system are called system are called megaphyllsmegaphylls
Origins of the Vascular SystemOrigins of the Vascular System
Evolution of branched stems before large leaves and roots?
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
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
Three Major Groups:Three Major Groups:
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)
Phylum Pterophyta (Ferns and Phylum Pterophyta (Ferns and Their Relatives):Their Relatives):
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.
Three Major Groups:Three Major Groups:
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
Phylum Pterophyta (Ferns and Phylum Pterophyta (Ferns and Their Relatives):Their Relatives):
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