Transcript Botany - Merrillville Community School

AP Biology
Chapter 29
Seedless Plants: Bryophytes and Ferns
Objectives
1. Name the protist group from which plants are hypothesized
to have descended, and describe supporting evidence.
2. Discuss some environmental challenges of living on land, and
describe how several adaptations meet these challenges.
3. Summarize the features that distinguish bryophytes from
green algae and from other plants.
4. Name and briefly describe the three phyla of bryophytes.
Algae
•Plantlike (autotrophic) protists
•Unicellular or Colonial
•Aquatic (live in water)
The Chlorophytes (green algae) appear to be
ancestral to the plants
Phylogeny of the Plants
Terrestrial (Land) Plants

The move from aquatic habitat to land
creates a number of problems:
◦ Protection against drying
◦ Transport of sperm to egg
◦ Structural support

Plants that have specialized adaptations to
solve these problems can live in drier
environments, while those that do not are
restricted to moist environments
Protection against drying
Water loss in
plants is called
Transpiration
 Terrestrial plants
are protected
against
transpiration by:

◦ Epidermis
◦ Waxy “cuticle”
◦ Stomata
Transport of sperm to egg
Algae and aquatic plants, since they live in
water, have a natural unbroken water
pathway for sperm to swim to the egg
 Seedless plants can only reproduce
sexually under moist conditions. The
“gametophyte” is low to the ground and
only grows in moist habitats
 Seed plants are less restricted because
they provide an internal water pathway in
a specialized “pollen tube”

Structural Support

Algae and aquatic plants are supported by
the buoyancy of the water they live in.
◦ Bryophytes, which lack strong supportive
tissues, are very small and low to the ground
◦ Tracheophytes, supported by a series of
hollow tubes with thickened cell walls, can
grow much taller
And now, some video.

http://www.youtube.com/watch?v=X4L3r
_XJW0I
Distinguishing Plants from Algae
Alternation of Generations
 Multicellular, dependent embryo
 Walled spores produced in sporangia
 Multicellular gametangia
 Apical meristems
 See pages 602-603 in textbook

Alternation of Generations
Gametophyte (n)
produces gametes (n)
 Gametes fuse to form
zygote (2n)
 Zygote develops into a
dependent, multicellular
embryo (2n)
 Embryo grow into the
sporophyte (2n)
 Sporophyte produces
spores (n) by meiosis
 Spores grow and
develop forming the
gametophyte (n)

Multicellular Embryo
The zygote
will develop
into an
embryo
within the
parent plant
 The parent
provides
protection
and
nourishment

Spores and Sporangia
Haploid spores will
be produced in
specialized organs on
the sporophyte
generation plant
called sporangia
 The spores are
protected by a
protective wall

Gametangia (produce gametes)
Moss Archegonium – Note the
mature eggs
Moss Antheridium – will produce
sperm cells
Apical Meristem



Growth of
multicellular organisms
begins with cells that
have not yet
differentiated.
In plants,
undifferentiated tissue
is called meristem.
Meristem tissue at the
tip (apex) of a root or
shoot is “apical”
meristem
Bryophytes
•Lack vascular tissue
•Reproduce with spores
Mosses
Liverworts
Classes of Bryophytes
Bryophyte Classes
Hornworts
 Liverworts
 Mosses
 See page 608 in Textbook

Objectives
5. Describe the life cycle of mosses, and compare their
gametophyte and sporophyte generations.
6. Discuss the features that distinguish ferns and other seedless
vascular plants from algae and bryophytes.
7. Describe the life cycle of ferns, and compare their
sporophyte and gametophyte generations.
8. Compare the generalized life cycles of homosporous and
heterosporous plants.
9. Name and briefly describe the four phyla of seedless vascular
plants.
Life Cycle of Mosses
Mosses – Comparing generations
Sporophyte Generation
◦ Temporary
◦ Dependent upon the
gametophyte
◦ Taller, grows from the
top of the gametophyte
◦ Not photosynthetic
Gametophyte Generation
◦ Permanent/Long lived
◦ Independent
◦ Shorter, grows from the
soil/anchored with
rhizoids
◦ Photosynthetic
Tracheophytes – Vascular plants

Vascular tissue provides advantages
◦ Efficient transport of water and nutrients
◦ Structural support
Tracheophyte phylogeny
Tracheophytes
include all plants
with vascular
tissue
 The tracheophytes
are subdivided
into seedless
plants and seed
plants
 Seed plants are
subdivided into
gymnosperms and
angiosperms
(flowering plants)

Vascular Seedless Plants
Ferns and Horsetails
•Have vascular tissue
•Reproduce with Spores
http://www.youtube.com/watch?v=xN8c_X0LNcg
Fern Life Cycle



The gametophyte
generation is small, flat
and nonvascular,
resembling a liverwort
The gametophyte dies
once the sporophyte is
established
The sporophyte is the
prominent generation
◦ Vascular
◦ Long lived
Ferns – Comparing Generations

Sporophyte
◦ Permanent/Long lived
◦ Independent once
established
◦ Produces a rhizome
for storage and
asexual reproduction
◦ Forms “fronds”

Gametophyte
◦ Temporary, dies once
the sporophyte is
established
◦ Nonvascular, small and
low to the ground
◦ Resembles liverwort
◦ Flattened form
captures and holds
water
Homosporous and Heterosporous

Homosporous Plants
◦ Most seedless vascular
plants
◦ Single type of spore
◦ Spores give rise to
monoecious (bisexual)
gametophytes

Heterosporous Plants
◦ All seed plants and
some seedless vascular
plants
◦ Two types of sporangia,
each producing a
different type of spore
◦ Megaspores give rise to
the female gametophyte
◦ Microspores give rise to
the male gametophyte
Seedless Vascular Plants

Lycophytes
◦ Most ancient group of vascular plants
◦ “club mosses” and “spike mosses”
◦ Superficially resemble mosses, but vascular

Whisk Ferns
◦ Branching stems, but no roots

Horsetails
◦ Photosynthetic stems with rings of branches or
small leaves

Ferns
◦ Horizontal stems with large “fronds” divided into
leaflets
Lycophytes
Whisk Ferns
Horsetails
Ferns
AP Biology
Chapter 30
Seed Plants: Gymnosperms and Angiosperms
Chapter 30 Objectives
1. Compare the features of seeds with those of spores
and discuss the advantages of plants that reproduce
primarily by seeds rather than by spores.
2. Trace the steps in the life cycle of a pine, and
compare its sporophyte and gametophyte
generations.
3. Summarize the features that distinguish
gymnosperms from bryophytes and ferns.
4. Name and briefly describe the four phyla of
gymnosperms.
Seed Plants
Seeds provide many advantages over spores
• Multicellular embryo
• Stored food
• Protection
• Mechanisms for dispersal
Conifers – Pine seeds
Flowering Plants –
Apple seeds
Life Cycle Trends
Alternation of generations continues in
the seed plants, but the gametophyte is
diminished to the point of being
microscopic
 By enclosing the gametophyte entirely
within the sporangium, the need for a film
of water for transport of sperm is
eliminated. The pathway is fully enclosed.
 Motility in sperm is lost in most seed
plants and diminished in others

Life Cycle of the Pine
The Pine tree is the sporophyte
generation
 Gymnosperms are heterosporous. The
megasporangium is located in an ovulate
cone. The microsporangium is in a pollen
cone.
 The female gametophyte develops entirely
within the megasporangium
 The male gametophyte is enclosed within
the pollen grain

Gymnosperm Life Cycle
Microsporangium
The pollen cone
contains
microsporangia,
which will
produce the
pollen grains
 The male
gametophyte is
within the pollen
grain

Megasporangium



The ovulate cone
contains the
megasporangium
The female
gametophyte is
enclosed within it
Pollination results
in the growth of a
pollen tube into
the ovule, directly
depositing a sperm
cell
Same deal, different diagram
Evolutionary significance

The gymnosperms had advantages over
seedless plants:
◦ With the gametophyte protected and sperm
delivered directly by the pollen tube,
gymnosperms were able to survive in much
drier environments than any of the seedless
plants.
◦ The climate became drier in the Mesozoic,
giving the advantage not only to the
gymnosperms, but also to the reptiles over
the amphibians
Concept check 30.1 p. 621
1.
2.
3.
Contrast sperm delivery in seedless
plants with sperm delivery in seed plants
What features not present in seedless
plants have contributed to the
enourmous success of seed plants on
land?
If a seed could not enter dormancy, how
might that affect the embryo’s transport
or survival?
Gymnosperms
Vascular, seed
producing plants
 “naked seed” – seeds
are not completely
enclosed by the
ripened ovary
 Generally have
needle-like (pines) or
scale-like (cedars)
leaves

Gymnosperm Phylogeny (p. 622-3)

Cycads
◦ Resemble palms, but are gymnosperms. The
cycads were the prominent large plants of the
mesozoic


Gnetophytes
Ginkgoes
◦ A deciduous gymnosperm, only one species still
exists

Conifers
◦ Pines, spruce, redwoods . . . The most diverse
group of gymnosperms
Chapter 30 Objectives
5. Summarize the features that distinguish
flowering plants from other plants
6. Diagram the parts of a flower. Describe the
structure and function of each part
7. Briefly explain the life cycle of a flowering
plant and describe double fertilization.
Angiosperms (Flowering Plants)
Vascular seed plants
 Have a wide variety
of adaptations for
transferring pollen
 Seeds mature inside
of the ripened ovary
of the flower, forming
“fruit” which
protects, nourishes,
and aids dispersal of
the seeds

Parts of a Flower
What parts can you recognize?
Double Fertilization
Double fertilization occurs only in the
angiosperms
 The pollen grain will produce 2 sperm
cells, one which will fertilize the egg to
form the zygote (2n) and another which
will fertilize the diploid female
gametophyte, producing a triploid cell
which will form the endosperm

The Endosperm and Cotyledons
The endosperm contains stored food
(mostly starch) which will contribute to
the early growth of the embryo
 The endosperm will form either 1 or 2
seed leaves called cotyledons
 Angiosperms are categorized as either
monocots or dicots based on the number
of cotyledons

Angiosperm life cycle
Chapter 30 Objectives
8. Define fruit. Discuss adaptive advantages of
fruits. Give examples
9. Contrast dicots and monocots, the two classes
of flowering plants.
10. Discuss the evolutionary adaptations of
flowering plants.
11. Summarize the evolution of gymnosperms from
seedless vascular plants, and trace the evolution
of flowering plants from gymnosperms
Fruit
Fruit is the
ripened ovary of
a flower
 Fruit may contain
stored food and
moisture
 Fruit provides a
mechanism for
seed dispersal

Monocots vs. Dicots
Monocots vs. Dicots
Advantages of Flowering Plants
Many flowering plants attract animal
pollinators, which increase the likelihood of
pollen grains actually resulting in pollination
 Seeds of flowering plants contain far more
stored food than the seeds of gymnosperms.
The endosperm provides for rapid growth of
the embryo after germination
 Fruit facilitates seed dispersal through a wide
variety of mechanisms: wind, water, animals

Trends in Plant Evolution



Animal pollinators greatly increase the rate
of cross-pollination, which in turn increases
the amount of genetic recombination and
variation that occurs within a species
Greater variation results in both more
opportunities for adaptation and a more
rapid rate of evolution
The connection between flower and
pollinator results in co-evolution. The flower
and the pollinator both evolve in relation to
each other
Pollinator/Flower Coevolution

Wasp mimicry
◦ https://www.youtube.com/watch?v=h8I3cqpgnA

The hoverfly
◦ https://www.youtube.com/watch?v=MQlq5Qt
RI9o

Overdramatic artistic pollinator
representation
◦ https://www.youtube.com/watch?v=MQlq5Qt
RI9o
Concept Check 30.3 p. 632
1.
2.
It has been said that an oak is an acorn’s
way of making more acorns. Write an
explanation that includes these terms:
Sporophyte, gametophyte, ovule, seed,
ovary and fruit
Compare and contrast a pine cone and a
flower in terms of structure and
function
Concept Check 30.3 p. 632
3. Do speciation rates in closely related
clades of flowering plants show that
flower shape is correlated with the rate
at which new species form, or that
flower shape is responsible for this rate?
Explain.