CHAPTER 29: PLANT DIVERSITY How Plants Colonized LandBy: Meg Riley, Anna

Ferlanti, and Laurie VanBenschoten

The Greening of Earth Land plants evolved from aquatic green

algae 500 mya Plants are crucial to life on Earth

Supply Oxygen Provide Habitats Provide Food

Charophyceans (algal ancestor of land plants)

http://greatneck.k12.ny.us/GNPS/SHS/dept/science/krauz/bio_h/images/29_03Charophyceans_LP.jpg

Evolution from Algae Aquatic green

algae= charophyceans closet living relative

of land plants, share a common ancestor

First land plants were seedless reproduced using

spores

Evidence for Common Ancestry Morphological and Biochemical Evidence

Structure of flagellated sperm Closely resembles that of charophyceans

Genetic Evidence Nuclear & chloroplast genes suggest

relatedness to charophyceans Confirms conclusions from above

Adaptations for Movement to Land Adaptations enabling the Move to Land

A chemical found in both charophyceans & land plants

Plantsencases spores

Algaeprevents

zygote from drying out in

exposed environment

s

The Plant Kingdom Kingdom Plantae currently includes all

embryophytes Embryophytes= plants that grow from an

embryo excludes charophyceans

Derived Traits of Land Plants

These traits, unique to nearly all plants, distinguish them from charophyceans Apical meristems- localized regions of cell division that make vascular

tissue Alternation of generations- alternation between two multicellular body

forms between generations Walled spores produced in sporangia- multicellular capsules that contain

and protect spores during development Multicellular gametangia- multicellular organs in which gametes are

produced Archegonia- female, 1 egg Antheridia- male, many sperm

Multicellular, dependent embryos- zygote retained within tissue of female parent and develops with nutrients from mother

Cuticle coverings- layer of polyesters & waxes that prevents plant from drying-out

***(see pg. 576-577 for full explanations)

Evolutionary History of Land Plants

Gametophyte vs. Sporophyte

Gametophyte multicellular

haploid form of a cell

undergoing alternation of generations

1n

Sporophyte multicellular

diploid form of a cell

undergoing alternation of generations

2n

VS.

Characteristics of Bryophytes

Bryophytes are seedless nonvascular plants found in three plant phyla…phylum Hepatophyta (liverworts),

Anthocerophyta (hornworts), and Bryophyta (aka moss) Gametophyte is dominant over sporophyte

Bryophyte Gametophytes Characteristics

Form ground-hugging carpets, low to the ground, short Thin, approx. 1 cell layer thick

Bryophyte Sporophytes Consist of 3 parts:

Foot- anchors to set into sporophyte Seta (or stalk)- holds up sporangium Sporangium (or capsule)- contains & protects spores

Ecological and Economic importance of Mosses Mosses are widespread and important

Ex. Peat moss used as fossil fuel and good for preserving bodies in swamps

: http://www.youtube.com/watch?v=jcWYAnmm-QE

Life Cycle of Bryophyte (ex. Moss)

Spores develop into threadlike strands of plant fibers

The haploid strands produce “buds” that grow into gametophytes

Most mosses have separate male and female gametophytes with antheridia and archegonia respectively

A sperm swims through a film of moisture to an archegonium and fertilizes the egg

The diploid zygote develops into a sporophyte embryo within the archegonium

The sporophytes grows a long stalk, or seta, that emerges from the archegonium

Attached by its foot, the sporophyte remains nutritionally dependent on the gametophyte

Meiosis occurs and haploid spores develop in the sporangium of the sporophyte

Sporangium pops off, propelling spores into the air using “teeth”

Characteristics of Lycophytes & Pterophytes

Origins and Traits of Vascular Plants Life Cycles with Dominant Sporophytes

More sporangia, more spores, more evolutionarily fit to survive into adulthood

Transport in Xylem and Phloem (type of vascular tissue) Xylem-conducts water & minerals Phloem- conducts sugar, amino acids, and other organic products

Evolution of Roots Roots –anchor plant, allow for absorption of water and nutrients from soil

Evolution of Leaves Leaves- increase surface area, allow capture of more sunlight for

photosynthesis, increase plant efficiency Mircohpylls- leaves of old lycophytes Megaphylls- leaves of new lycophytes, more complex

Characteristics of Seedless Vascular Plants (cont.)

Sporophylls and Spore Variations Sporophylls (modified leaves with sporangia)

Homosporous vs. Heterosporous

Megaspores vs. Microspores

Life Cycle of a Lycophyte (ex. Fern)

Sporangia release spores Spore develops into

photosynthetic gametophyte Cross or self- fertilization

may occur between male and female gametes

Sperm use flagella to swim from antheridium to archegonium

Sporophyte grow out of archegonium of gametophyte

Spores form in clusters on underside of reproductive leaves (sorus)

Classification Phylum Lycophyta: older seedless vascular

plants, common ones include spike & club mosses (not true mosses)

Phylum Pterophyta: younger seedless vascular, all sorts of ferns

http://www.sd23.bc.ca/~mbirkela/FOV1-000ABDA6/S0A59B017.4/tips-for-sorting-through-ferns0.jpg

http://kmacphoto.net/ferns.jpg

Spike/Club Moss Fern

Significance How evolution of vascular tissue, roots, and leaves

allows plants to grow bigger than ever before…development of large forests

Increased removal of CO2 from atmosphere, resulting in global cooling

Plants fossilize to from coal, however, once coal is burned as fossil fuels, it results in global warming

Answers to Activity: Part 1- Moss5 26 31 78 4 Part 2- Fern2 63 41 5