Today: - Lab Review - Nontracheophytes (Bryophytes) cont’d - Into the Pterophytes, Gymnosperms,...

Today:Today:- - Lab ReviewLab Review- Nontracheophytes (Bryophytes) cont’d- Nontracheophytes (Bryophytes) cont’d- Into the Pterophytes, Gymnosperms, and - Into the Pterophytes, Gymnosperms, and

Angiosperms!Angiosperms!

Lab Review:Lab Review:

Image 1: What is this? Haploid or diploid? What comes next in the lifecycle?


Lifecycle Review:Lifecycle Review:

With your group, briefly sketch the lifecycle of a typical moss

and a typical fern. What would you say if you were asked to

compare and contrast the two??

Evolution Evolution of Land of Land

Plants: A Plants: A ReviewReview

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


Evolution Evolution of Land of Land

Plants: A Plants: A ReviewReview

The GymnospermsThe Gymnosperms“Naked Seeds”“Naked Seeds”

3 Major Adaptations:3 Major Adaptations:

1.1. Continued Continued reduction of reduction of gametophytegametophyte

2.2. Evolution of the Evolution of the seedseed

3.3. Evolution of Evolution of pollenpollen

Arabidopsis thaliana pollen grains Microscopy by Juergen

Berger, computer image manipulation by Heiko Schoof

1. Reduction of the Gametophyte1. Reduction of the Gametophyte

Why keep the Why keep the gametophyte??gametophyte??

Is the haploid gametophyte a good Is the haploid gametophyte a good genetic screen??genetic screen??

Is the sporophyte too dependent on Is the sporophyte too dependent on the gametophyte??the gametophyte??

2. Evolution of the Seed2. Evolution of the Seed

SEEDSEED = sporophyte embryo packaged = sporophyte embryo packaged with a food supply in a protective with a food supply in a protective

coat.coat.

The fossilized remains of the Jeholornis prima, shown in an illustration, included about 50 well-preserved seeds in the bird's

stomach. (CNN.com)

Why are seeds such a great advantage??


All seed plants are heterosporous

Megaspores (+ female gametophytes) retained within parent sporophyte!

OVULEOVULE(Integument + (Integument +

Megaporangium Megaporangium + Megaspore)+ Megaspore)

After fertilization, After fertilization, the ovule the ovule

develops into a develops into a SEEDSEED..


3. Evolution of Polle3. Evolution of Pollenn

MicrosporesMicrospores develop into develop into pollen grainspollen grains

Pollen grains mature to Pollen grains mature to become male become male gametophtyesgametophtyes

Transfer of pollen to ovule Transfer of pollen to ovule = = pollinationpollination

Doesn’t require water!!Doesn’t require water!!

GymnospermsGymnospermsOvules and seeds develop of the surface of Ovules and seeds develop of the surface of

specialized leaves called specialized leaves called sporophyllssporophylls

GymnosperGymnosperm Evolutionm Evolution

Gymnosperm DiversityGymnosperm Diversity

Four extant Four extant phyla:phyla:

1.1. GinkophytaGinkophyta

2.2. CycanophytaCycanophyta

3.3. GnetophytaGnetophyta

4.4. ConiferophytaConiferophyta

•One remaining species!

•Popular ornamental (pollution resistant)

•Produces Gingko and stinky, fleshy seeds


•Few species of tropical, palm-like trees

•Symbiotic with N-fixing bacteria

•Toxic to livestock!







•3 very different genera:

Welwitschia, Gnetum, and Ephedra






Government announces ban on ephedraWednesday, December 31, 2003 Posted: 7:58 AM EST (1258 GMT)

The debate over the safety of ephedra heated up after pitcher Steve Bechler died February

17.


•Largest group (pines firs, spruces, larches, yews, junipers, cedars, cypresses and redwoods)

•Mostly evergreen; dominant in N. hemisphere where growing seasons are relatively short






A Gymnosperm (Coniferophyta) Life Cycle

Thought Question For You…Thought Question For You…

Why to Conifers do so well here?

Shouldn’t they be outcompeted by the angiosperms

(flowering trees)??

Cool Cool Coniferous Coniferous

AdaptationsAdaptations

Into the Angiosperms!Into the Angiosperms!

Minor Minor ModificationModification

ssBothBoth

gymnosperms gymnosperms and and

angiosperms angiosperms use use tracheidstracheids in their xylemin their xylem

Angiosperms also Angiosperms also use use vessel vessel

elementselements, and , and reinforce with reinforce with fiber cellsfiber cells!!

Major Major Modification: Modification: the Flower the Flower4 circles of

modified leaves:

1.Sepals

2.Petals

3.Stamens

4.Carpels

Fruits are Mature OvariesFruits are Mature Ovaries

Fruits protect seeds and aid in their Fruits protect seeds and aid in their dispersaldispersal

Ovary wall becomes the Ovary wall becomes the pericarppericarp (thickened wall of the fruit)(thickened wall of the fruit)

Fruits are Mature OvariesFruits are Mature Ovaries

Hypothetical Origin of the CarpelHypothetical Origin of the Carpel

Types of FruitTypes of Fruit1. 1. Simple Fruit-Simple Fruit- derived from a single ovary derived from a single ovary

2. 2. Aggregate Fruit-Aggregate Fruit- derived from a single derived from a single flower with several carpelsflower with several carpels

3. 3. Multiple Fruit-Multiple Fruit- develops from a group of develops from a group of flowers tightly clustered together flowers tightly clustered together (inflorescence)(inflorescence)

The AngiospermsThe Angiosperms

Evolution of the Flower!Evolution of the Flower!

Traditional taxonomy = 2 ClassesTraditional taxonomy = 2 Classes

Monocots Monocots

and and

DicotsDicots

Jack-in-the-Pulpit, Arisaema triphyllum

Not Monophyleti

c!

Angiosperm LifecyclesAngiosperm Lifecycles

Like the Gymnosperms:Like the Gymnosperms: HeterosporousHeterosporous Flower of the Flower of the

sporophyte produces sporophyte produces microspores (will form microspores (will form male gametophytes) male gametophytes) and megaspores (will and megaspores (will form female form female gametophytes)gametophytes)

Angiosperm LifecyclesAngiosperm LifecyclesIn Angiosperms, In Angiosperms, Each pollen grain has two Each pollen grain has two

haploid cellshaploid cellsOvules develop within the Ovules develop within the

ovaryovary, contain the , contain the female gametophyte or female gametophyte or embryo sac embryo sac

(Even further reduction of (Even further reduction of gametophyte gametophyte generation!)generation!)

Double

Useful Animation??Useful Animation??

At left, Germinating Pollen Grain from a Lily,

Sauromatum guttatum

(SEM x3,300).

This image is copyright Dennis Kunkel at

www.DennisKunkel.com, used with permission.

Cross-PollinationCross-Pollination

Some flowers can self-Some flowers can self-pollinate, but most use pollinate, but most use diverse strategies to diverse strategies to ensure cross-pollinationensure cross-pollination

Angiosperms Shape Angiosperms Shape EvolutionEvolution

By the end of the By the end of the Cretaceous (65 mya) Cretaceous (65 mya) angiosperms are the angiosperms are the dominant plants on dominant plants on

Earth.Earth.

Plants and their Plants and their pollinators and pollinators and

dispersers are a good dispersers are a good example of example of

coevolutioncoevolution (mutual (mutual evolutionary influence)evolutionary influence)

Other Notes about Other Notes about AngiospermsAngiosperms

- - Ecologically importantEcologically important

- Major human food - Major human food sourcesource

- Source of unique - Source of unique secondary compounds secondary compounds (drugs!)(drugs!)

Diversity is a non-renewable Diversity is a non-renewable resource!resource!

Today: - Lab Review - Nontracheophytes (Bryophytes) cont’d - Into the Pterophytes, Gymnosperms,...

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