CHAPTER 29: PLANT DIVERSITY
By: Meg Riley, Anna Ferlanti, and
Laurie VanBenschoten
How Plants Colonized Land
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
spores
using
Evidence for Common Ancestry

Morphological and Biochemical Evidence
 Structure
 Closely

of flagellated sperm
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
Algae
prevents zygote
from
drying out in
exposed
environments
Plants
encases
spores
The Plant Kingdom

Kingdom Plantae currently includes all
embryophytes
 Embryophytes=
 excludes
plants that grow from an embryo
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 dryingout
***(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
VS.
Sporophyte
multicellular
diploid form of a
cell undergoing
alternation of
generations
2n
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



Bryophyte Sporophytes

Consist of 3 parts:




Form ground-hugging carpets, low to the ground, short
Thin, approx. 1 cell layer thick
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


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


More sporangia, more spores, more evolutionarily fit to survive into adulthood
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
Spike/Club Moss
Fern
http://kmacphoto.net/ferns.jpg
http://www.sd23.bc.ca/~mbirkela/FOV1-000ABDA6/S0A59B017.4/tips-for-sorting-through-ferns0.jpg
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- Moss
52
63
17
84
 Part 2- Fern
26
34
15
