Chapter 30: Plant Diversity II
By Dan Xiang, Sam Taylor, and Graham Opie
Important Terms
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Bryophyte - Non vascular terrestrial plants
Gametophyte - Haploid generation of plants
Sporophyte - Diploid generation of plants
Integument - Layers of sporophyte tissue
Heterospory - Production of two spores male and
female by the sporophyte of land plants
• Double fertilization - One sperm fertilizes egg,
another fuses with the two nuclei found in the
large central cell of the female gametophyte
Overview
• Seed developed around 360 million years ago.
• The harvesting of gymnosperms and
angiosperms (mainly angiosperms) allowed
humans to have permanent settlement.
• Most plants today are classified as either a
gymnosperm or an angiosperm
30.1 The reduced gametophytes of seed plants
are protected in ovules and pollen grains
• The first known seeded plants cames into
existence more than 360 million years ago
• The evolution of seeds allowed plants to become
the dominant producers in most of the terrestrial
ecosystems.
• Seeded plants began to make up the vast
majority of plant biodiversity.
• During permian period arid climates let
gymnosperms thrive. (think moss preproduction)
Adaptations of seed plants
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Reduced gametophytes
Heterospory
Ovules
Pollen
Cotyledons and endosperms
Reduced gametophytes
• Seedless plants have lifecycles that are
dominated by gametophytes
• Seeded plants lifecycles are dominated by
sporophyte stage.
• Miniaturization of the gametophyte stage lets
the gametophyte develop from a spore inside
of the sporangia.
Heterosporous vs Homosporous
• Seedless plants are almost all homosporous
and thus have bisexual gametophytes
• Seed plants are heterosporous
• Some seedless plants are heterosporous
• Female gametophyte in a heterosporous plant
is called the megaspore
• Male gametophyte in a heterosporous plant is
called the microspore
Diagram of ovule (and pollen)
Heterospore difference continued/
ovule section
• Though some seedless plants can be
heterosporous, seed plants are unique in that
they keep the megaspore within the parent
sporophyte
• While inside the sporophyte the
megasporangia is enveloped by an
integument(s) in order to protect the
megaspore
Heterospory/pollen
• Microspores develop into pollen grains, they
carry the male gametophyte
• The pollen has a hard coat of the polymer
sporopollenin (not a hard term to remember
for once)
• Pollen can travel very long distances especially
compared to the sperm of seedless plants.
Advantages of seeds
• The seed allows for a greater chance that the
ovule will be pollinated safely and that the zygote
(embyro) will remain safe until it matures.
• Helps the plant thrive or reproduce easier in
harsh climates.
• Being able to travel farther enables the new plant
that is born from the seed to not have to share its
resources with its parent as often.
• Cotyledons and endosperms
30.2 Gymnosperms bear “naked” seeds,
typically on cones
• Their seeds are considered “naked”
• They are the first form of seed plants
• Some of the most common gymnosperms are
conifers, or cone-bearing plants
• The transitional plants between seedless
plants and gymnosperms are called
progymnosperms…
• The four phyla of gymnosperms are cycads,
ginkgo, gnetophytes, and conifers.
Naked seeds
• In naked seeds the endosperm is haploid
• Conifers have male and female cones, the
pollen from male cone fertilizes the haploid
ovules of the female cone then a diploid cell is
produced (embryo)
• Other gymnosperms have similar setups but
with seeds on their leaves instead of
protective cone seed.
http://www.youtube.com/watch?v=D9byVQxv
MXs
Life Cycle of a Pine
30.3 The reproductive adaptations of
angiosperms include flowers and fruits
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90% of Plantae Kingdom
250,000 known species
Phylum Anthophyta
Flower Structure unique to Angiosperm sexual
reproduction
• Pollen transportation
Flower Structure
Angiosperm Reproduction
Function of Fruits
• Mechanism to disperse seeds
• Consists of a mature ovary
• Pollination occurs->ovary wall becomes a
pericarp->the rest of the flower withers away
• Pollination does not occur->flower just
withers away
• Fruits are either fleshy or dry
Fruit Adaptations
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Fruits adapt to disperse seeds
Winged seeds
Water dispersal (i.e. Coconut)
Fruit with burrs can cling
Edible, nutritious, sweet, colorful
Purpose of double fertilization is preventing
flower from wasting resources
http://www.youtube.com/watch?v=Gq8NWh9
8wQs
Angiosperm Origins and Evolution
• First Angiosperms developed 140 mya
• Archaefructus liaoningensis & Archaefructus
sinensis- 125 million years old
• Comparison of A. sinensis with 173 species of
modern angiosperms
• Michael Frohlich- “evo-devo” approach.
• Ancestor had separate ovule and pollen
producing structures
Cont.
• Mutations occurred and ovule developed on
some microsporophyll
• “Mostly male” hypothesis
• Gene comparison between gymnosperm
pollen producing genes and flower
development genes
Angiosperm Diversity
• Monocots- “One” “Cotyledon” i.e. orchids,
palms, corn, wheat, rice- ¼ angiosperms
• Dicots- “Two” Cotyledon” i.e. roses, peas,
sunflowers
• Dicots->Eudicots
• Basal angiosperms
Evolutionary Links between
Angiosperms and Animals
• Animals create a selective pressure for plants
and vice versa
• Mutual evolutionary relationship benefits
both partners
• Bees/hummingbird and angiosperm
relationship increases diversity in both
30.4 Human welfare depends greatly on seed
plants
• 80% of all the food we eat comes from
angiosperms
• Modern crops come from recent changes to
plant diversity, humans selected for more
fitting traits in plants
• About 25% of medicine contains ingredients
from angiosperms, wood is very important to
human development.
Cont.
• Deforestation is causing the most drastic rate
of decrease in plant diversity since Permian
and Cretaceous extinctions.
• The loss of plant diversity equates to the loss
in diversity of many other species because
seed plants are often the building blocks of
ecosystems.
Works Cited
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"1-introduction of lima bean - Classification explinations: comparing
angiosperms and gymnosperms." 1-introduction of lima bean - Just another
Edublogs.org weblog. N.p., n.d. Web. 13 Nov. 2011.
<http://brubini4662.edublogs.org/2010/05/27/classification-explinationscomparing-angiosperms-and-gymnosperms/>.
"Biology 2108." College of Science and Mathematics. N.p., n.d. Web. 13 Nov.
2011.
<http://science.kennesaw.edu/~jdirnber/Bio2108/Lecture/LecBiodiversity/Bio
DivPlants.html>.
"[ Plant Life Cycle Phases - Phase One ( Planting Seeds ) ]." Welcome to Penn
State York. N.p., n.d. Web. 13 Nov. 2011.
<http://www2.yk.psu.edu/~sg3/ist311/games/team3/>.
kelikelvin19. "
Seed Production in Gymnosperm - YouTube ."
YouTube - Broadcast Yourself. . N.p., n.d. Web. 13 Nov. 2011.
<http://www.youtube.com/watch?v=D9byVQxvMXs>.
leoquartz06. "
Seed Production in Gymnosperm - YouTube ."
YouTube - Broadcast Yourself. . N.p., n.d. Web. 13 Nov. 2011.
<http://www.youtube.com/watch?v=D9byVQxvMXs>.