Transcript Plants & The Colonization of Land

Plant Diversity
General Characteristics of Plants
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All plants are:
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Eukaryotic
Autotrophic
Multicellular
Cell Walls with cellulose
Chloroplasts w/ chlorophyll
a, b, and carotenoids
May have waxy cuticle to
prevent water loss.
Stomata allow gas
exchange.
Plants probably evolved
from green algae
(charophytes)
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Chloroplast similarity
Biochemical similarities
Cell Wall similarities
Charophytes
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No alternation of
generations
No cuticle needed
Jacketed gametes
No protection of
embryos
v.
Plants
Alternation of
generations
 Cuticle (prevents water
loss/dessication)
 Jacketed gametes
(protects from
dessication)
 Protected embryo
(protects from
dessication)
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Alternation of Generations
Sporophyte (2N)
Mitosis
Meiosis
Zygote (2N)
Spores (N)
fertilization
Gametes (egg
& sperm
Gametophyte (N)
Evolutionary Trend
Figure 23.2
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zygote
GREEN ALGA
BRYOPHYTE
FERN
GYMNOSPERM
ANGIOSPERM
Classifying Plants
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Plants can be divided into 2 major categories based
on their characteristics:
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Nonvascular Plants
 Do NOT have specialized tissues to transport water and
nutrients
 Instead, these plants transport water from cell-to-cell by
osmosis
Vascular Plants
 Have specialized tissues to transport water and nutrients in
plants
 Xylem – carries water upward from roots
 Phloem – carries nutrients and carbohydrates produced by
photosynthesis
Nonvascular Plants (Bryophytes)
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Again, these plants do not have specialized tissues
to transport water and nutrients and instead rely on
osmosis
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Thus, these plants must be small
Why?
Major types of bryophytes (nonvascular plants):
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Mosses
Liverworts
Hornworts
Nonvascular Plants/
Bryophytes
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Mosses
 Have rhizoids that anchor
them to the ground
(instead of roots)
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Depend on water for
fertilization
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The sperm must swim to the
egg
Therefore, nonvascular
plants must live in MOIST
environments
Gametophyte is the dominant
phase of the life cycle
Moss/ Bryophyte Life Cycle
zygote
Zygote grows,
develops into a
sporophyte while
still attached to
gametophyte.
mature
sporophyte
Diploid Stage
Fertilization
Haploid Stage
Meiosis
Spores
germinate.
spermproducing
structure
Figure 23.5
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eggproducing
structure
male
gametophyte
female
gametophyte
Vascular Plants/Tracheophytes
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Reminder:
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Vascular plants have specialized tissues to
transport water and nutrients in plants
Xylem & phloem
Vascular plants (tracheophytes) can be
divided into 2 categories:
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Seedless vascular plants
Seed (vascular) plants
Seedless Vascular Plants
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Have true roots, leaves,
and stems
Consist of ferns, club
mosses, and
horsetails
Seedless Vascular Plants
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Ferns – A Close Up
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Diploid sporophyte is the
dominant stage
Have rhizomes, which are
underground stems
Fronds: large “leaves”
where spores develop
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Develop spores in
sporangia on underside
of fronds
Reproduce using spores
A sorus (plural: sori) is a
cluster of sporangia
Fern Life Cycle
Sporophyte still attached
to gametophyte
sorus
zygote
fertilization
egg
rhizome
Diploid Stage
meiosis
Haploid Stage
Spores develop
Spores
are
released
sperm
Figure 23.9
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mature
gametophyte
Spore germinates
Seed (Vascular) Plants
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Have true roots, leaves, and
stems
Have the ability to form
seeds, which are used for
reproduction
Seed plants are the most
dominant group of
photosynthetic organisms
on land
There are 2 types of seed
(vascular) plants:
 1. gymnosperms
 2. angiosperms
Seed (Vascular) Plants
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Gymnosperms =
“cone bearers”
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“naked seeds” – not
enclosed in ovaries
Bear seeds directly on the
surfaces of cones
 Cones = sporophyte
structures that produce
gametophytes (seeds)
Coniferous trees are the
major example
 Pines, junipers, spruces,
etc.
section
through one
ovule
surface view of one cone scale
(houses two ovules)
Pine Life Cycle
ovule
surface view of one cone scale
(houses a pollen-producing sac)
mature
sporophyte
seed
coat
section through a
pollen-producing sac
zygote
seeding
pollen tube
spermproducing cell
Diploid
embryo
seed
fertilization
meiosis
Haploid
microspores
eggs
form
megaspores
pollination
form
female
gametophyte
Figure 23.17
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Seed (Vascular) Plants
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Angiosperms = flowering plants
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Seeds are enclosed by an ovary
Flowers are reproductive organs
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Flowering plants contain ovaries
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Evolutionary advantage 
attract pollinators
Ovaries surround and protect
seeds
Ovary develops into a fruit after
pollination & helps with seed
dispersal when eaten
Examples:
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Maple trees, tulips, grass
sporophyte
Flowering
Plant Life
Cycle
Diploid
Double fertilization
Haploid
pollination
two
sperm
enter
ovule
Meiosis
microspores
female gametophyte
Meiosis
mitosis
without
cytoplasmic
division
Figure 23.20
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Evolutionary Tree for Plants
Nested monophyletic groups
green zygophytes, charophytes bryophytes lycophytes
algae
related
groups
horsetails
ferns
cycads ginkgos conifers gnetophytes
flowering
plants
seed plants
euphyllophytes
embryophytes (land plants)
vascular plants
(closely related groups)