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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