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Chapter 29 - Plant Diversity 1

How Plants Colonized Land
STUDY
PLAY
Cyanobacteria likely existed on land ___ _______ years ago.
1.2 billion
Around ___ _______ _____ ago, small plants, fungi, and animals emerged on land
500 billion years
Since colonizing land, how many plant species have diversified?
roughly 290, 000
Land plants are defined by ...
having terrestrial ancestors, even though some now might be aquatic

they do not include photosynthetic protists (algae)
Plants supply ______ and are the ultimate source of most food eaten by land animals.
oxygen
Land plants evolved from _____ _____.
green algae (charophyte)
4 traits land plants share with algae.
1) Alternation of generations and Multicellular, Dependent Embryos
2) Walled Spores produced in Sporangia
3) Multicellular Gametangia
Alteration of generations and multicellular, dependent embryos
life cycles of land plants occur in two generations of multicellular organisms : gametophytes and sporophytes.

each generation gives rise to the other

this occurs in most algae, but not charophytes

distinguished by the fact that the life cycle includes multi-cellular haploid organisms and multi-cellular diploid organisms
5 generalized steps of alternation of generations
1) the gametophyte produces haploid gametes by mitosis.
2) Two gametes unite (fertilization) and form a diploid zygote.
3) the zygote develops into a multicellular diploid sporophyte.
4) the sporophyte produces haploid spores by meiosis.
5) the spores develop into multicellular haploid gametophytes.
Walled Spores Produced in Sporangia
sporophytes have multiple organs called sporangia that produce spores.

prevents exposed zygotes from drying out

alos found in plant spore walls

charophyte algae lack multicellular sporangia and their flagellated, water-dispersed spores lack sporopollenin.
Multicellular Gametangia
the production of gametes within multicellular organs called gametangia

female gametangia called archegonia
male gametangia called antheridia
Apical Meristems
localized regions of cell division at the tips of roots and shoots.

cells produced by Apical Meristems differentiate into the outer epidermis, which protects the body, and various types of internal tissue
4 key traits land plants SHARE with charophytes
1) rings of cellulose-synthesizing complexes
2) peroxisome enzymes
3) structure of flagellated sperm
4) formation of phragmoplast
kingdom of plants
embryophytes

dependency of the embryo on the plant
How are nutrients transferred from plants to embryo?
placental transfer cells
archegonia
produce eggs and are the site of fertilization

female gametangia
antheridia
produce and release sperm

male gametangia
Cuticle
additional derived trait of plants
waxy covering of the epidermis
aids in waterproofing, helping prevent excessive water loss while aiding in protection from microbial plants.
Mycorrizae
additional derived trait of plants
symbiotic associations between fungi and land plants that may have helped plants without true roots to obtain nutrients

create SA, obtain nutrients
Secondary Compounds
additional derived trait of plants
deters herbivores and parasites
Fossil evidence indictates that plants were on land at least ___ _______ _____ ago.
475 million years
Fossilized spores and tissues have been extracted from ___ _______ ____-old rocks.
475 million year
land plants are grouped based on the
presence or absence of vascular tissue
nonvascular plants are called
bryophytes
clades of seedless vascular plants
lycophytes (club mosses and their relatives)
pterophytes (ferns and their relatives)

seeless vascular plants are paraphyletic - of the same biological organization, or grade
seed
embryo and nutrients surrounded by a protective coat

gymnosperms and angiosperms
gymnosperms
the "naked seed" plants, including the conifers
angiosperms
flowering plants
Mosses and other nonvascular plants have lifecycles dominated by .....
gametophytes
3 phyla of small, herbaceous (nonwoody) plants
Liverworts (Hepatophyta)
Hornworts (Anthocerophyta)
Mosses (Bryophyta)
in all three bryophyte phyla, ____________ are larger and longer living than ___________.
gametophytes, sporophytes
___________ are typically present only part of the time
sporophytes
A spore germinates into a gametophyte composed of a _________ and gamete-producing gametophore
protonema
one cell thick filaments with large SA that enhances absorption of water and minerals
protonema
The height of gametophytes is constrained by ____ __ ________ ______.
lack of vascular tissue
anchor gametophytes to substrate, not composed of tissues, do not play a role in mineral absorption
rhizoids
Mature gametophytes produce flagellated sperm in __________ and an egg in each ___________.

Sperm swim through a film of water to reach and fertilize the egg.
antheridia, archegonium
Bryophyte sporophytes grow out of __________, and are the smallet and simplest sporophytes of all extant plant groups.
archegonia
a sporophyte consists of a ....
foot
seta (stalk)
sporangium (capsule)
foot
absorbs nutrients from gametophyte
seta (stalk)
conducts nutrients into the sporangium (capsule
sporangium (capsule)
produce spores by meiosi
peristome
discharge spores

open - dry
closed - moist
Hornwort and moss sporophytes have _______ for gas exchange; liverworts do not.
stomata
What do mosses help retain in the soil
nitrogen!
spaghnum
"peat moss"
forms extensive deposits of partially decayed organic material known as peat.

peat can be used as a source of fuel
important global resoivoir of organic carbon

overharvesting spaghnum and/or a drop in water level in peatlands could release stored CO2 to the atmosphere.
_____ and other ________ ________ ______ were the first plants to grow tall.
Ferns, seedless vascular plants
What was the prevalent form of vegetation for the first 100 million years of plant evolution?
Bryophytes and bryophyte- like plants
When did Vascular plants begin to diversify during the ________ and _____________ periods
Devonian and Carboniferous
Why are seedless vascular plants usually restricted to moist environments?
they have flagellated sperm
How far back do fossils of the forerunners of vascular plants date back?
425 million years
living vascular plants were characterized by
life cycles with dominant sporophytes
vascular tissue called xylem and phloem
well-developed roots and leaves
in contrast with bryophytes, sporophytes of seedless vascular plants are the larger generation, as in ________ _____
familiar ferns
in seedless vascular plants, gametophytes grow
on or below the soil surface
What does xylem conduct?
water and minerals, including dead cells called traicheids

strengthened by lignin and provide structural support
phloem
consists of living cells and distributes sugars, AA, and other organic products
________ ______ allowed for increased height, which provided an evolutionary advantage
Vascular Tissue
_____ are organs that anchor vascular plants.
Roots, they enable vascular plants to absorb nutrients form the soil

may have evolved from subterranean stems
______ are organs that increase the SA of vascular plants, thereby capturing more solar energy that is used for photosynthesis.
Leaves!
2 categories of leaves
microphylls - single vein (evolved as outbranch of stems)
macrophylls - highly branched vascular system (may have evolved as webbing between flattened branches)
___________ are modified leaves with sporangia.
Sporophylls
____ are clusters of sporangia on the underside of sporophylls.
Sori
strobili
cone-like structures formed from groups of sporophylls
most seedless vascular plants are ___________, producing one type of spore that develops into a bisexual gametophyte.
homosporous
All seed plants and some seedless plants are
heterosporous
megaspores
give rise to female gametophytes
microspores
give rise to male gametophytes
2 phyla of seedless vascular plants
lycophyta (club mosses, spike mosses, and quillworts)
pterophyta (ferns, horsetails, whisk ferns, and their relatives)
_____ _________ _____ survived for millions of years in moist swamps
giant lycophyta trees

surviving species are small herbaceous plants

club mosses and spike mosses have vascular tissues and are not true mosses.
_____ are the most diverse seedless vascular plants, with more than ____ species
Ferns, 12000

most diverse in tropics, but also in temperate forests.
__________ were diverse during the _____________ period, but are now restricted to the genus Equistum.
Horsetails, Carboniferous
Increased ______ ___ ______________ removed CO2 from the atmosphere and may have contributed to global cooling at the end of the Carboniferous period.
growth and photosynthesis
The decaying plants of these _____________ _______ eventually became ____.
Carboniferous forests, coal