Section 1
Sexual Reproduction
in Seedless Plants
Section 1
Focus
Overview
Before beginning this section
review with your students the
objectives listed in the Student
Edition. This lesson begins with a
discussion of alternation of generations, which occurs in all plants. It
continues with the life cycle of a
moss to introduce the reproductive
structures and life cycles of nonvascular plants. A fern is used to
illustrate the reproductive structures
and life cycles of seedless vascular
plants.
Reproduction in Nonvascular Plants
Objectives
● Summarize the life cycle of
a moss.
13B
● Summarize the life cycle of
13B
a fern.
● Compare and Contrast
the life cycle of a moss with
the life cycle of a fern.
13B
Key Terms
archegonium
antheridium
sorus
Bellringer
Place a moss and a fern on your
desk. Instruct students to write a
short paragraph that describes a
moss or fern plant. Tell them to be
as descriptive as possible about the
plant’s general appearance and
where it lives.
The carpet of green you often see near streams and in moist, shady
places is usually made up of mosses or liverworts. As you learned in
the previous chapter, these small, relatively simple plants are nonvascular plants. They do not have a vascular system for distributing
water and nutrients. Mosses and liverworts do not usually thrive
outside moist places because they must be covered by a film of
water to reproduce sexually.
Like all plants, nonvascular plants have a life cycle called alternation of generations. In this type of life cycle, a gamete-producing
stage, or gametophyte, alternates with a spore-producing stage, or
sporophyte. Gametophytes produce gametes (eggs and sperm) in
separate multicellular structures. The structure that produces eggs
is called an archegonium (ark uh GOHN ee uhm). The structure that
produces sperm is called an antheridium (an thuhr IHD ee uhm).
Sporophytes produce spores in a sporangium. The gametophytes of
nonvascular plants are larger and more noticeable than are the
sporophytes. This difference in size is very pronounced in the liverworts, as you can see in Figure 1.
Figure 1 Reproductive structures of a liverwort
Sporophytes, which grew
from archegonia under
the cap of a female stalk
The gametophytes of Marchantia, a common liverwort,
produce male and female gametes on separate stalks.
Motivate
Antheridia on top
of a male stalk
Discussion/Question
Tell students that the sperm of a
nonvascular plant must swim to an
egg cell for fertilization to occur.
Ask students to describe environmental conditions that would
enable nonvascular plants to reproduce sexually. (Nonvascular plants
are able to reproduce sexually wherever moisture is abundant. Shady
areas near streams are ideal habitats.
In drier habitats, nonvascular plants
can reproduce sexually after a rainfall
or heavy dew.) LS Interpersonal
TAKS 2 Bio 6D (grade 10 only), 8C
TAKS 3 Bio 7B, 13A; Bio 5A, 13B
Sporophytes
Male
stalks
Female
stalks
Archegonia under the
cap of a female stalk
530
Chapter Resource File
pp. 530–531
Student Edition
TAKS Obj 2 Bio 8C
TAKS Obj 3 Bio 7B
TAKS Obj 3 Bio 13A
TEKS Bio 7B, 8C, 13A, 13B
Teacher Edition
TAKS Obj 2 Bio 6D, 8C
TAKS Obj 3 Bio 7B, 13A
TEKS Bio 5A, 6D, 6E, 7B, 8C, 10C,
13A, 13B
530
• Lesson Plan GENERAL
• Directed Reading
• Active Reading GENERAL
• Data Sheet for Quick Lab
GENERAL
Planner CD-ROM
• Reading Organizers
• Reading Strategies
Chapter 24 • Plant Reproduction
Transparencies
TT Life Cycle of a Moss
TT Life Cycle of a Fern
Life Cycle of a Moss
The life cycle of a moss is summarized in Figure 2. Sexual reproduction results in a fertilized egg, or zygote. The diploid zygote grows into
a new diploid sporophyte. As you can see, a moss sporophyte grows
from a gametophyte and remains attached to it. The sporophyte
consists of a bare stalk with a spore capsule (sporangium) at its tip.
Spores form by meiosis inside the spore capsule. Therefore, as in all
plants, the spores are haploid. The spore capsule opens when the
spores are mature, and the spores are carried away by wind or water.
When a moss spore settles to the ground, it germinates and grows into
a “leafy” green gametophyte. Archegonia and antheridia form at the
tips of the haploid gametophytes. Eggs and sperm form by mitosis
inside the archegonia and antheridia. Remember, moss gametophytes
grow in tightly packed clumps of many individuals. When water
covers a clump of mosses, sperm can swim to nearby archegonia and
fertilize the eggs inside them.
Diploid (2n)
2
Haploid (n)
3
An adult sporophyte produces
spores within its spore capsule.
Spores grow into male
and female gametophytes.
The word archegonium
comes from the Greek
words archegonos,
meaning “first of a race.”
Knowing this makes it
easier to remember that a
new and genetically
different individual grows
from an archegonium when
its egg is fertilized.
Figure 2 Moss life cycle.
In mosses, a sporophyte that
consists of a spore capsule on
a bare stalk alternates with a
“leafy,” green gametophyte.
Meiosis
Adult
sporophyte
Spores
Spore capsule
(sporangium)
Germinating spore
4
Gametophytes
produce gametes
inside antheridia
and archegonia.
Mitosis
Using the Figure
Walk students through the moss life
cycle shown in Figure 2, starting
with the zygote. Point out that the
zygote divides mitotically. Repeated
mitotic cell divisions result in a
multicellular, diploid organism
called the sporophyte. In mosses,
the sporophytes are not green, and
they consist of a bare stalk topped
with a spore capsule. Reproductive
cells in the spore capsule undergo
meiosis, which reduces the chromosome number from diploid to
haploid. Point out that the spores
grow into either male or female
gametophytes, which are haploid. In
mosses, the gametophytes are green
and have leaflike structures. Finally,
point out that when fertilization (the
union of an egg and a sperm) occurs
and a new zygote is formed, the
diploid chromosome number is
restored, and a new sporophyte
generation begins. LS Visual
Bio 6E, 10C, 13B
Male
Young sporophyte
Teach
Female
Gametophytes
READING
GENERAL
SKILL
BUILDER
1
A zygote develops
into a new sporophyte.
Mitosis
Antheridia
Sperm
Archegonia
Zygote
5
Egg
Sperm swim to
and fertilize eggs
inside the archegonia.
Fertilization
531
MISCONCEPTION
ALERT
Spores The term spore does not have a single, concise definition as students might think.
Two things are generally true of spores. First,
they are unicellular; second, they have a protective outer covering. In some bacteria, spores
form from regular cells when environmental
conditions are harsh. These cells lose most of
their water and develop a protective outer
covering. Many of these bacteria also produce toxins, which help the spores remain
viable in harsh environments. The spores
of fungi and plants are haploid, droughtresistant, and easily transported by wind or
water. The spores of fungi and plants develop
into multicellular individuals (by mitotic cell
division) without fusing with another cell.
Brainstorming Ask students to
identify the haploid structures in a
plant’s life cycle (spores, male and
female gametophytes, eggs, and
sperm). Ask which are unicellular
(spores, sperm, and eggs) and which
are multicellular (male and female
gametophytes). Ask students to
identify the haploid structures in an
animal’s life cycle (egg and sperm).
Ask if these are unicellular or multicellular (unicellular). Ask students
to identify the diploid structures in
a plant’s life cycle (sporophyte,
zygote). Ask which is unicellular
(zygote) and which is multicellular
(sporophyte). Ask students to identify the diploid structures in an
animal’s life cycle (all stages of
development from the zygote to the
adult). Ask which of these structures is unicellular (zygote) and
which are multicellular (all other
stages of development).
LS Interpersonal Bio 6E, 10C, 13B
Chapter 24 • Plant Reproduction
531
Reproduction in Seedless
Vascular Plants
Teach, continued
continued
SKILL
BUILDER
GENERAL
Math Skills Ask students to use
the information in Figure 3 to estimate the number of spores that one
fern plant might produce. To help
them with their calculations, have
students assume that only half of
the frond is visible in the photo,
each sporangium produces 100
spores, and one plant produces 12
fronds. (A sample calculation would
be as follows: 260 sori per frond 30
sporangia per sorus 100 spores per
sporangium 12 fronds per plant
= 9,360,000 spores per plant.)
LS Logical TAKS 1 Bio/IPC 2C; Bio 13B
Figure 3 Sori on a fern
frond. Many sori are visible
on this portion of a frond from
a polypody fern. Each sorus
consists of about 20–30
sporangia.
Observing a Fern
Gametophyte
Skills Acquired
Observing, making
comparisons, making
conclusions
Observing a Fern
Gametophyte 13B
Teacher’s Notes
Tell students that fern gametophytes develop on moist soil
and are very small.
You can observe the archegonia and antheridia
of a fern gametophyte with a microscope.
Materials
prepared slide of a fern gametophyte with archegonia
and antheridia, compound microscope
Answers to Analysis
1. Answers will vary but should
be consistent with the diagrams in Figure 4.
2. A new sporophyte begins its
growth in an archegonium.
This process occurs because
the egg remains in the archegonium, and a sperm cell swims
from an antheridium to the
archegonium where it fertilizes
the egg.
You may recall that the seedless vascular plants include
the whisk ferns, horsetails, club mosses, and ferns. The
seedless vascular plants differ from the nonvascular
plants because they have efficient water- and foodconducting systems of vascular tissue. Like the
nonvascular plants, the seedless vascular plants thrive in
moist, shady places. They can reproduce sexually only
when a film of water covers the gametophyte. Eggs form
in archegonia, and sperm form in antheridia. The
archegonia and antheridia develop on the lower surfaces
of the gametophytes. In most species of seedless vascular
plants, both eggs and sperm are produced by the same
individual. In some species, however, eggs and sperm are
produced by separate gametophytes.
Unlike nonvascular plants, seedless vascular plants
have sporophytes that are much larger than their gametophytes. Some ferns, for example, have sporophytes that are
as large as trees. On the other hand, the gametophytes of
ferns are thin, green, heart-shaped plants that are less than 1 cm (0.5
in.) across. The sporophytes produce spores in sporangia. In horsetails and club mosses, sporangia develop in cones. In ferns, clusters of
sporangia form on the lower surfaces of fronds, as shown in Figure 3.
A cluster of sporangia on a fern frond is called a sorus . The word
sorus comes from the Greek word soros, meaning “a heap.”
Analysis
Procedure
1.
Examine a slide of a
fern gametophyte
under low power of a microscope. Move the slide until
you can see a cluster of
archegonia. Now, switch to
high power, and focus on one
archegonium. Draw and label
what you see.
Fern Gametophytes (56)
2. Switch back to low power,
and move the slide until you
can see several egg-shaped
structures. These are
antheridia. Now, switch to
high power, and focus on one
antheridium. Draw and label
what you see.
1. Describe the appearance of
an archegonium and an
antheridium.
2. Critical Thinking
Drawing Conclusions In
which structure, an archegonium or antheridium, does the
growth of a new sporophyte
begin? Explain.
532
TAKS 1 Bio/IPC 2C, 2D; Bio 13B
REAL WORLD
IPC Benchmark Mini-Lesson
CONNECTION
pp. 532–533
Student Edition
TAKS Obj 2 Bio 8C
TAKS Obj 3 Bio 7B
TAKS Obj 3 Bio 13A
TEKS Bio 7B, 8C, 13A, 13B
Teacher Edition
TAKS Obj 1 Bio/IPC 2C, 2D
TAKS Obj 2 Bio 8C
TAKS Obj 4 IPC 8A
TEKS Bio 6E, 8C, 13B
TEKS Bio/IPC 2C, 2D
TEKS IPC 8A
532
Garden centers and florists often receive calls
about insects on ferns and flower arrangements that include fern leaves. When the fern
leaves have sporangia on them, people often
mistake the sori or sporangia for insects. A
close look at these spore-producing structures reveals that they are lined up in rows
across from each other. Insect pests, such as
scale and mealy bugs, rarely line up in such
regular patterns.
Chapter 24 • Plant Reproduction
Biology/IPC Skills TAKS 4 IPC 8A
Distinguish between physical and chemical changes
in matter, such as ... stages in the rock cycle.
Activity Have students use the Internet to research
how fossils and fossil fuels are formed. As students to
prepare a poster showing the stages that lead to the
formation of fossils and fossil fuels.
Life Cycle of a Fern
The life cycle of a fern is summarized in Figure 4. A fertilized egg, or
zygote, grows into a new sporophyte. The diploid sporophyte produces
spores by meiosis. The haploid spores fall to the ground and grow into
haploid gametophytes. Fern gametophytes produce gametes by mitosis—eggs in archegonia and sperm in antheridia. Sperm swim to
archegonia and fertilize the eggs inside them.
Diploid (2n)
2
Figure 4 Fern life cycle.
In ferns, a large sporophyte
with leaves called fronds
alternates with a small, green,
heart-shaped gametophyte.
Haploid (n)
Sporangium
An adult sporophyte produces
spores in clusters of sporangia.
3
Mitosis
Meiosis
The spores grow into a
gametophyte.
Spores
4
Lower
surface
Gametophytes produce
gametes inside antheridia
and archegonia.
Mature
gametophyte
Adult
sporophyte
Close
Reteaching
Summarize the life cycles of mosses
and ferns. Emphasize that all plants
alternate between a haploid phase
and a diploid phase in their life
cycles. Tell students that in mosses
and ferns, the multicellular forms
in both phases are visible with the
unaided eye. Point out that the
gametophyte phase in mosses is
dominant and that the sporophytes
are not photosynthetic. Also point
out that the sporophyte phase is
dominant in ferns but that the
young sporophytes are dependent
on the gametophytes. LS Verbal
TAKS 2 Bio 8C; Bio 6E, 13B
Antheridium
Frond
Quiz
Rhizome
Roots
1. What is the name of the single-
Archegonium
5
Mitosis
1
A zygote develops into
a new sporophyte.
celled, haploid reproductive
structure of plants? (spore)
2. What is the meaning of the
phrase alternation of generations? (It means that plants have a
life cycle that alternates between
haploid and diploid phases.)
3. What is the name of the structure that makes up the first stage
of a new plant’s life cycle?
(zygote)
Sperm swim to the
archegonia and
fertilize eggs.
Zygote
Young
sporophyte
Sperm
Egg
Mitosis
Fertilization
Section 1 Review
List five major steps in the life cycle of a moss.
List five major steps in the life cycle of a fern.
13B
Critical Thinking Analyzing Information
13B
What are the major differences between the moss
life cycle and the fern life cycle?
13B
Critical Thinking Forming Reasoned
Opinions Which reproductive structures, gametes
or spores, are responsible for the dispersal (spread)
13A 13B
of seedless plants? Justify your answer.
TAKS Test Prep What is the function of an
13B
archegonium?
A to produce sperm
C to produce spores
B to produce eggs
D to conduct water
533
Answers to Section Review
1. First, a zygote grows into a sporophyte by
mitotic cell division. Next (2), the sporophyte
forms spores following meiotic cell division.
Then (3), the spores grow into gametophytes
by mitotic cell division. After the gametophytes
form eggs and sperm by mitotic cell division
(4), eggs are fertilized by sperm and a new
zygote forms (5). Bio 13B
2. First, a zygote grows into a sporophyte by
mitotic cell division. Next (2), the sporophyte
forms spores following meiotic cell division.
Then (3), the spores grow into gametophytes
by mitotic cell division. After the gametophytes
form eggs and sperm by mitotic cell division
GENERAL
(4), eggs are fertilized by sperm and a new
zygote forms (5). Bio 13B
3. Spores are responsible for the dispersal of seedless plants. Spores are drought-resistant and can
be transported in the air or in water. TAKS 3 Bio
13A; 13B
4. In mosses, the gametophyte is dominant; in
ferns, the sporophyte is dominant. Mosses
form separate male and female gametophytes,
while ferns form a gametophyte that produces
both eggs and sperm. Bio 13B
5. A. Incorrect. The antheridium produces sperm.
B. Correct. C. Incorrect. The sporangium produces spores. D. Incorrect. There are no
structures for conducting water in the moss
plant. Bio 13B
Alternative
Assessment
GENERAL
Poster Have student groups make
posters that depict the life cycles of
mosses and ferns. Suggest that they
use color-coding to identify the
structures common to the life cycles
of these two groups. (Both have a
zygote, a sporophyte, spores, a gametophyte, antheridia, archegonia, eggs,
and sperm.) Students also can use
color-coding to highlight the differences between the life cycles of
mosses and ferns. (Mosses have separate male and female gametophytes,
while ferns have both antheridia and
archegonia on each gametophyte.)
LS Verbal Co-op Learning
Bio 6E, 13B
Chapter 24 • Plant Reproduction
533
Section 2
Section 2
Focus
Sexual Reproduction
in Seed Plants
Overview
Before beginning this section
review with your students the
objectives listed in the Student
Edition. This lesson introduces
reproduction in seed plants, including seed structure and formation.
Discussion of the reproductive
structures and life cycle of gymnosperms features a coniferous
plant. The lesson on reproductive
structures and the life cycle of
angiosperms includes a discussion
of insects in the fertilization process
and the formation of endosperm by
double fertilization.
Reproductive Structures
of Seed Plants
Objectives
● Distinguish the male and
female gametophytes of seed
plants.
13B
Reproduction in seed plants (gymnosperms and angiosperms) is
quite different from reproduction in seedless plants. For one thing,
you need a microscope to see the gametophytes of seed plants, as
Figure 5 shows. Also, spores are not released from seed plants. The
spores remain within the tissue of a sporophyte and develop into
two kinds of gametophytes—male gametophytes, which produce
sperm, and female gametophytes, which produce eggs. The tiny
gametophytes of seed plants consist of only a few cells. A male
gametophyte of a seed plant develops into a pollen grain, which has
a thick protective wall. A female gametophyte of a seed plant develops inside an ovule (AHV yool), which is a multicellular structure
that is part of the sporophyte. Following fertilization, the ovule and
its contents develop into a seed.
Because the gametophytes of seed plants are very small, seed plants
are able to reproduce sexually without water. Wind and animals
transport pollen grains to the structures that contain ovules. The
transfer of pollen grains from the male reproductive structures of a
plant to the female reproductive structures of a plant is called
pollination. When a pollen grain reaches a compatible female reproductive structure, a tube emerges from the pollen grain. This tube,
called a pollen tube, grows from a pollen grain to an ovule and
enables a sperm to pass directly to an egg.
● Describe the function of
each part of a seed.
13B
● Summarize the life cycle of
a conifer.
13B
● Relate the parts of a flower
to their functions.
13B
● Summarize the life cycle of
an angiosperm.
13B
Key Terms
pollen grain
ovule
pollination
pollen tube
seed coat
cotyledon
sepal
petal
stamen
anther
pistil
ovary
double fertilization
Bellringer
Give each student five different
kinds of seeds and have them list
similarities and differences.
Examples include various beans,
peas, maple seeds, pine seeds,
coconuts, and poppy. Remind them
of the discussion about pollen
dispersal at the beginning of the
chapter and point out that seeds
are also adapted to different means
of dispersal, including wind, water,
and ingestion and elimination by
animals. This exercise can lead into
a discussion of seed structure and
function. TAKS 2 Bio 13A; Bio 13B
Figure 5 Seed plant gametophytes
The tiny gametophytes of seed plants develop within specialized structures that
form in the reproductive parts of a flower.
Pollen grains
Pollen grains are transferred to a female
structure during pollination.
Male reproductive
structure
Ovules
A pollen grain consists
of only two or three cells.
Female reproductive
structure
The female gametophyte
within an ovule consists of
only seven cells.
534
Chapter Resource File
• Lesson Plan GENERAL
• Directed Reading
• Active Reading GENERAL
pp. 534–535
Student Edition
TAKS Obj 2 Bio 8C
TAKS Obj 3 Bio 7B
TAKS Obj 3 Bio 13A
TEKS Bio 7B, 8C, 13A, 13B
Teacher Edition
TAKS Obj 2 Bio 8C
TAKS Obj 3 Bio 13A
TAKS Obj 5 IPC 4B
TEKS Bio 6E, 8C, 10C, 13A, 13B
TEKS IPC 4B
534
Chapter 24 • Plant Reproduction
Transparencies
Planner CD-ROM
• Reading Organizers
• Reading Strategies
TT Bellringer
TT Seed Plant Gametophyte
TT Seed Structure
Seeds
As you learned in the previous chapter, seeds contain the embryos of
seed plants. A plant embryo is a new sporophyte. A seed forms from
an ovule after the egg within it has been fertilized. The outer cell
layers of an ovule harden to form the seed coat as a seed matures.
The tough seed coat protects the embryo in a seed from mechanical
injury and from a harsh environment. The seed coat also prevents
the embryo from immediately growing into a young plant by keeping out water and oxygen. Deprived of water and oxygen, the
embryo stops growing and cannot resume its growth until water
and oxygen can pass through the seed coat. Often, a seed must be
exposed to cold temperatures, or the seed coat must be damaged,
before the seed can take in water and oxygen. Thus, seeds enable the
embryos of seed plants to survive conditions that are unfavorable
for plant growth for long periods of time.
Seeds also contain tissue that provides nutrients to plant embryos.
In gymnosperms, this nutritious tissue is part of the female
gametophyte. The seeds of angiosperms, however, develop a nutritious tissue called endosperm. Endosperm originates at the same
time an egg is fertilized. In some angiosperms, such as corn and
wheat, endosperm is still present in mature seeds. In other
angiosperms, such as beans and peas, the nutrients in the
endosperm have already been transferred to the embryo by the time
a seed is mature.
Leaflike structures called cotyledons (kah tuh LEE duhnz), or
seed leaves, are a part of a plant embryo. Cotyledons function in the
transfer of nutrients to the embryo. The embryos of gymnosperms
have two or more cotyledons. For example, pine embryos have eight
cotyledons. In the flowering plants, the embryos of monocots have
one cotyledon, and the embryos of dicots have two cotyledons. The
structure of three types of seeds is shown in Figure 6.
Interpreting Graphics
After reading the chapter,
trace or make a sketch of
Figure 6 without the labels.
On separate pieces of
paper, write down the
labels. Without referring to
your book, match the labels
with the correct parts of
your sketch.
Teaching Tip
Origins of Embryos Tell students
that in some plants, such as citrus,
the embryo contained within the seed
doesn’t always develop from a fertilized egg. Instead, it develops from
other cells in the ovule. Plants that
grow from such embryos are identical to their female parent. Bio 6E, 10C, 13B
Bean seed
Wing
Endosperm (3n)
Embryo
Seed coat
Embryonic
leaves
Seed coat
Gymnosperm Flash Cards Have
students write the key terms for this
section on separate note cards.
Then, have them write a definition
on the back of each card as they
read the section. Have students
divide their cards into three groups:
characteristics of gymnosperms only
(none found only in gymnosperms);
characteristics of angiosperms only
(sepal, petal, stamen, anther, pistil,
ovary, double fertilization); and characteristics of both gymnosperms and
angiosperms (pollen grain, ovule, pollination, pollen tube, seed coat, cotyledon). Have students use their cards
for the Reteaching exercise.
Teach
Seeds have many similarities and differences in structure.
Corn grain
Activity
LS Verbal
Figure 6 Seed structure
Pine seed
Motivate
READING
SKILL
Cotyledons
Embryonic
root
BUILDER
Embryonic
root
Embryo
Reading Organizer As students
read about the plant life cycles in
this chapter, have them develop
cycle concept maps. LS Verbal
Cotyledons
Seed coat
fused to ovary wall
Female
gametophyte (n)
Bio 6E, 10C, 13B
535
did you know?
A Sunflower Seed is Not Just a Seed A
sunflower seed is a dry fruit (called an achene)
with a seed inside. The edible part is the actual
seed, which consists mainly of cotyledons. A
corn kernel is also not just a seed but a dry
fruit (called a caryopsis) with a seed inside. The
outer covering of a corn kernel is not easily
removed, as is the outer covering of a sunflower seed. The edible part of the corn fruit
is the whole kernel. Bio 13B
GENERAL
IPC Benchmark Fact
There is a limit on how much protection a tough seed
coat provides for a seed embryo against mechanical
injury. A mechanical injury to a seed occurs when the
kinetic energy of an object that strikes a seed
exceeds the intrinsic strength of the seed coat.
Remind students that kinetic energy—that is, energy
of motion—depends on an object’s mass and its
speed. Consequently, more massive objects require
less speed in order to damage a seed coat.
TAKS 5 IPC 4B
Group Activity
Dissecting Seeds Bring a variety
of seeds to class, including at least
one type of gymnosperm seed
(pine, spruce, fir), one type of dicot
seed (bean, pea, melon, squash),
and one type of monocot seed
(corn, wheat, iris). Make a longitudinal cut through at least one seed
of each type. Have students examine the whole and opened seeds
using their unaided eyes and a dissecting microscope. Ask students to
compare the characteristics of the
three different types of seeds.
LS Visual Co-op Learning TAKS 2 Bio 8C
Chapter 24 • Plant Reproduction
535
Cones
Teach, continued
continued
Activity
Plant Propagator Plant propagators work for wholesale and retail
nurseries where they grow plants
for sale. A plant propagator grows
plants from seeds and by a variety
of vegetative methods. Have students use library references or
online databases to find out about
plant propagation in the nursery
and floral industries. Have students
write reports summarizing their
findings. LS Verbal Bio 3D
Figure 7 Male and female
pine cones. This branch of an
Austrian pine has an immature
seed cone and many pollen
cones.
Observing the
Gametophytes of
Pines Bio 10C, 13B
Skills Acquired
Observing, making
comparisons, drawing
conclusions
Seed plants are the most successful of all plants. The success of the
seed plants is due in part to the specialized structures in which
seeds develop. In angiosperms, the ovules (immature seeds) are
completely enclosed by sporophyte tissue at the time of pollination.
In gymnosperms, the ovules are not completely enclosed by sporophyte tissue until after pollination.
The gametophytes of gymnosperms develop in cones, which
consist of whorls (circles) of modified leaves called scales.
Gymnosperms produce two types of cones. Male cones, or pollen
cones, produce pollen grains within sacs that develop on the surface
of their scales. Female cones, or seed cones, produce ovules on the
surface of their scales. Many gymnosperms produce both male and
female cones on the same plant. As shown in Figure 7, the numerous
small pollen cones lie to the left of the large seed cone. In some gymnosperms, male and female cones form on separate plants.
Pollen cones produce large quantities of pollen grains that are
carried by wind to female cones. At the time of pollination, the
scales of a female cone are open, exposing the ovules. When a pollen
grain lands near an ovule, a slender pollen tube grows out of the
pollen grain and into the ovule. The sperm moves through the pollen
tube and enters the ovule. Thus, the pollen tube delivers a sperm to
the egg inside the ovule. Seed cones close up after pollination and
remain closed until the seeds within them are mature. This process
can take up to two years.
Observing the Gametophytes
of Pines 13B
Teacher’s Notes
Ask students to look for similarities between the two types
of cones when they are examined under a microscope.
You can observe the gametophytes of a pine with
a microscope.
Materials
prepared slides of the following: male pine cone, female
pine cone, pine ovule; hand lens; compound microscope Immature female pine cone
Answers to Analysis
1. Both have whorls of scales, but
male cones are smaller than
female cones and contain
pollen, while female cones contain eggs and eventually seeds.
2. The growth rate of pollen tubes
in pines is extremely slow.
Analysis
Procedure
1.
Examine prepared
slides of male and
female pine cones first with a
hand lens and then under the
low power of a microscope.
3. Examine a prepared slide of a
pine ovule under the low
power of a compound microscope. Compare what you
see with the photo above.
2. Make a sketch of each type
of pine cone, and label the
structures that you recognize.
4. Draw a pine ovule, and label
the following structures:
scale, ovule, egg, pollen tube
(if visible).
Transparencies
TT Life Cycle of a Conifer
1. Compare and Contrast
the structure and contents of
male and female pine cones.
2. Critical Thinking
Applying Information It
takes 15 months for a pine
pollen tube to grow through
the wall of a pine ovule. How
would you describe the rate of
pollen-tube growth in pines?
536
Cultural
Awareness
pp. 536–537
Student Edition
TAKS Obj 2 Bio 8C
TAKS Obj 3 Bio 7B
TAKS Obj 3 Bio 13A
TEKS Bio 7B, 8C, 13A, 13B
Teacher Edition
TAKS Obj 2 Bio 8C
TAKS Obj 5 IPC 4B
TEKS Bio 3D, 3F, 6E, 8C, 10C, 13B
TEKS Bio/IPC 3C
TEKS IPC 4B
536
George Washington Carver George
Washington Carver (1864–1943) was a
horticulturist whose agricultural research
revolutionized the economy of the southern
United States by encouraging farmers to grow
more than just cotton. He urged farmers to
grow sweet potatoes, peanuts, pecans, and
soybeans. In 1896, the same year he received
Chapter 24 • Plant Reproduction
his master’s degree at Iowa State College of
Agriculture and Mechanic Arts, Carver was
asked to head the Department of Agriculture
at Tuskegee Institute, in Alabama. There he
helped to develop more than 300 industrial
products from peanuts, 100 from sweet
potatoes, and 75 from pecans.
Bio/IPC 3C; Bio 3F
Life Cycle of a Conifer
Most gymnosperms are conifers, a group that includes pines. You can
trace the stages in the life cycle of a pine in Figure 8. In pines, as in all
plants, a diploid zygote results from sexual reproduction. The zygote
develops into an embryo, which then becomes dormant (inactive).
The embryo and the surrounding tissues form a seed. When their
seeds are mature, seed cones open, and the seeds fall out. A pine seed
has a wing that causes it to spin like the blade of a helicopter. Thus,
pine seeds often travel some distance from their parent tree.
When conditions are favorable for growth, the seeds grow into
new sporophytes. An adult pine tree produces both male and female
cones. Spores form by meiosis, which occurs inside immature
cones. The spores grow into gametophytes, which produce eggs and
sperm by mitosis. After pollination, a pollen tube begins to grow
from each pollen grain toward the eggs inside an ovule. Fertilization
occurs as a sperm fuses with an egg, forming a zygote that will grow
into a new sporophyte.
Diploid (2n)
Using the Figure
Figure 8 Conifer life
cycle. In conifers, a very large
sporophyte that produces
cones alternates with tiny
gametophytes that form on
the scales of cones.
Haploid (n)
4
Meiosis
Scale
Female
spore
Spores develop into
male and female
gametophytes.
Eggs
(within female
gametophyte)
Ovule
3
Immature
seed cone
Male and female
spores form on
the scales of
the cones.
Gametophytes
Pollen
(male gametophytes)
Meiosis
Male spore
Pollen
cone
Pollination
Fertilization
Adult sporophyte
5
2
Mitosis
An adult pine produces
male and female cones.
1
The zygote and ovule develop
into a seed, which grows into
a new sporophyte.
Mitosis
Sperm
After pollination, sperm
enter the ovule through
a pollen tube, and
fertilization occurs.
LS Visual TAKS 2 Bio 8C; Bio 6E, 10C, 13B
Group Activity
Mature
seed cone
Pollen
tube
Pine seed
(with wing)
Scale
Young sporophyte
Zygote
537
did you know?
What is a “Jumping Bean”? Jumping beans,
which are grown in Central and South
America, are the seeds of plants in the spurge
family. A jumping bean contains a moth larva.
The jumping movements occur when the moth
larva inside changes position with a jerk. The
jumping bean is also known as the “bronco
bean” or “leaper.”
Walk students through the
gymnosperm life cycle shown in
Figure 8, starting with the zygote.
Point out that, as in animals and
other multicellular eukaryotic
organisms, repeated mitotic cell
divisions of the zygote result in a
multicellular diploid organism. In
plants, the multicellular diploid
organism is called the sporophyte.
Reproductive cells in the mature
sporophyte undergo meiosis.
During this process, the chromosome number is reduced from
diploid to haploid. Point out that
there are two kinds of spores produced—male spores (microspores)
and female spores (megaspores)—
and that these spores grow into
two different types of gametophytes—pollen grains, or male
gametophytes (microgametophytes), that produce sperm cells
and female gametophytes (megagametophytes) that produce egg cells.
Both kinds of gametophyte are
haploid. Finally, point out that
when fertilization (the uniting of an
egg and a sperm) occurs and a new
zygote is formed, the diploid chromosome number is restored, and a
new sporophyte generation begins.
IPC Benchmark Fact
When a pine seed falls to the ground the force of
gravity causes it to accelerate toward Earth’s surface
at approximately 9.8 m/s2. However, a pine seed’s wing
reduces the rate of acceleration by giving the seed
some upward lift as it spins in the air. Provide the students with some pine seeds and have them measure
the mass of each seed. Next, have students drop each
from various heights and time how long it takes each
seed to reach the ground. Then, have students calculate each pine seed’s average acceleration using
Newton’s second law a F/m and compare this
number with the expected acceleration.
TAKS 5 IPC 4B
Diversity of Pollen Grains
Provide students with a variety of
flowers with pollen or give them
pollen alone (for example, pollen
from a pine tree). Have students
make wet-mount slides of pollen
samples to observe the intricately
detailed coats of pollen grains. Have
students draw what they observe.
You could also provide them with
pictures (for example, from a college biology textbook) showing
electron micrographs of some
pollen grains.
English Language
LS Kinesthetic
Learners
Chapter 24 • Plant Reproduction
537
Flowers
Teach, continued
continued
Observing the
Arrangement of
Parts of a Flower
TAKS 2 Bio 8C;
TAKS 3 Bio 13A; Bio 10C, 13B
Skills Acquired
Observing, making
comparisons, drawing
conclusions
Teacher’s Notes
Provide a variety of monocot
and dicot flowers for the class
and have each student examine
one of each type.
Ask students to think about
how the flowers they examine
are pollinated. (Flowers that are
open and have stamens and stigmas exposed are likely crosspollinated. Flowers that are
closed and have stamens and
stigmas that are not exposed are
likely self-pollinated.)
Figure 9 Basic flower
structure. The four basic
parts of a flower—sepals,
petals, stamens, and pistils—
are arranged in concentric
whorls.
Stamen
Anther
Filament
Observing the Arrangement
of Parts of a Flower 13A
13B
TAKS 2, TAKS 3
Answers to Analysis
1. Answers may vary. Students
should comment on color, size,
and numbers of sepals and
petals.
2. Answers will vary. Students
should suggest that large,
brightly colored petals may
attract animal pollinators
(such as insects) while flowers
with small, inconspicuous
petals are probably windpollinated.
3. Answers may vary. Students
should note the following:
monocots have flower parts in
multiples of three; dicots have
flower parts in multiples of
two, four, or five.
In angiosperms, gametophytes develop within flowers. The basic
structure of a flower is shown in Figure 9. Flower parts are
arranged in four concentric whorls. The outermost whorl consists
of one or more sepals (SEE puhlz), which protect a flower from
damage while it is a bud. The second whorl consists of one or
more petals , which attract pollinators. The third whorl consists of
one or more stamens (STAY muhnz), which produce pollen. Each
stamen is made of a threadlike filament that is topped by a pollenproducing sac called an anther . The fourth and
innermost whorl of a flower consists of one or
more pistils , which produce ovules. Ovules
Petal
develop in a pistil’s swollen lower portion,
which is called the ovary. Usually, a stalk, called
the style, rises from the ovary . Pollen lands on
and sticks to the stigma—the swollen, sticky tip
of the style.
Flowers may or may not have all four of the
basic flower parts. A flower that has all four
Stigma
parts is called a complete flower. Flowers that
Style Pistil
lack any one of the four types of parts are called
Ovary
incomplete flowers. If a flower has both stamens and pistils, it is called a perfect flower.
Sepal
Flowers that lack either stamens or pistils are
called imperfect flowers.
You can see how the parts of flowers are arranged
by dissecting flowers.
Materials
gloves, monocot flower, dicot flower, paper, tape
Procedure
1.
Put on gloves. Examine
a monocot flower and
a dicot flower. Locate the
sepals, petals, stamens, and
pistil of each flower.
2. Separate the parts of each
flower, and tape them to a
piece of paper. Label each
set of parts.
3. Count the number of petals,
sepals, and stamens in each
flower. Record this information below each flower.
Analysis
1. Compare and Contrast
the appearance of the sepals
and petals of each flower.
INCLUSION
• Learning Disability
538
3. Critical Thinking
Justifying Conclusions
Explain why each flower is from
either a monocot or a dicot.
538
Strategies
pp. 538–539
Student Edition
TAKS Obj 2 Bio 8C
TAKS Obj 3 Bio 7B
TAKS Obj 3 Bio 12B
TAKS Obj 3 Bio 13A
TEKS Bio 7B, 8C, 12B, 13A, 13B
Teacher Edition
TAKS Obj 2 Bio 8C
TAKS Obj 3 Bio 7B, 13A
TEKS Bio 7B, 8C, 10C, 13A, 13B
2. Critical Thinking
Forming a Hypothesis
For each flower, suggest a
function for the petals based
on their appearance.
• Attention Deficit
Disorder
Using Figure 9 as a guide, ask students to
make a clay model of the basic flower structure. The parts of the flower can be labeled
with straight pins and strips of paper stuck
into the model. The model should be made
to lie flat on a piece of cardboard for easy
display. Students can show their understanding of the parts of the flower by
describing them in a short presentation of
tape recording. Bio 13B
Chapter 24 • Plant Reproduction
Transparencies
TT Floral Structure
TT Life Cycle of Angiosperms
Flowers and Their Pollinators
Many flowers have brightly colored petals, sugary
nectar, strong odors, and shapes that attract animal
pollinators. Flowers are a source of food for pollinators such as insects, birds, and bats. For example, bees
eat nectar and collect pollen, which is a rich source of
protein they feed to their larvae. A bee gets coated
with pollen as it visits a flower and then carries that
pollen to other flowers.
Bees locate flowers by scent first and then by color
and shape. Bee-pollinated flowers are usually blue or
yellow and often have markings that show the location of nectar. Moths, which feed at night, tend to visit heavily
scented white flowers, which are easy to find in dim light. Flies may
pollinate flowers that smell like rotten meat.
Many flowers are not pollinated primarily by insects. Red flowers,
for instance, may be pollinated by hummingbirds. Some large white
flowers that open at night are pollinated by nighttime visitors—bats,
as seen in Figure 10. Many flowers, such as those of grasses and
oaks, are pollinated by wind. Wind-pollinated flowers are usually
small and lack bright colors, strong odors, and nectar.
Teaching Tip
Figure 10 Bat pollination.
This lesser long-nosed bat pollinates an organ pipe cactus as
it feeds on the pollen of the
plant’s flowers.
GENERAL
Double Fertilization in
Angiosperms Have students
make a Graphic Organizer similar
to the one at the bottom of this
page to illustrate the process of
double fertilization in angiosperms,
discussed on the following page.
Ask students to use the applicable
vocabulary words for this section,
plus any other words that they wish
to include. LS Visual Bio 10C, 13B
Protecting Honeybees
TAKS 3 Bio
Protecting Honeybees
TAKS 3
B
ees pollinate more species of
plants than any other animal.
The most familiar of the more than
20,000 species of bees is the
European honeybee, Apis mellifera, which was imported to the
United States in the 1600s.
Beekeepers raise honeybees
mainly for the honey they produce. However, the bees also
benefit farmers by pollinating
more than 90 kinds of crop plants,
which are worth $10 billion a year.
Threats to Honeybees
Since 1990, the population of
beekeeper-raised honeybees has
decreased by 25 percent in the
United States. Some of this
decline is due to pesticide use
and loss of food sources, but the
major culprits are parasites,
pests, and diseases. The most
serious problem currently facing
U.S. honeybees is the varroa
mite. This tiny, blood-sucking
parasite probably entered the
United States in the 1980s. It
now infests beehives throughout
most of North America, causing
approximately $160 million worth
of damage each year.
The small hive beetle is a pest
that was introduced to the southern United States from Africa in
1998. The immature beetles tunnel through hives in search of
honey and pollen, killing the developing bees and forcing entire
colonies to abandon their hives.
American foulbrood is a bacterial disease that attacks developing honeybees. Highly contagious,
the disease has the potential to
spread rapidly throughout the
United States.
Research to the Rescue
Scientists at the Kika De La
Garza Subtropical Agricultural
Research Center in Weslaco,
Texas are studying ways to defeat
the biological threats to honeybees. The scientists test natural
and synthetic chemicals for use in
controlling varroa mites and small
hive beetles. They are also working to develop new antibiotics that
will be effective against the bacteria that cause American foulbrood.
www.scilinks.org
Topic: Crop Pollination
Keyword: HX4053
539
Teaching Strategies 7B; Bio 13B
• Tell students that in addition
to food plants, many rare and
endangered plants are also
pollinated by honeybees.
Scientists are worried that
honeybee losses could cause
declines in rare and endangered plant populations.
• Have students research crop
pollination using the Web site
in the Internet Connect box on
this page and write a report
summarizing their findings.
Discussion
• In what ways are bees important in food production?
(They produce honey, and they
pollinate the flowers of many
food crops.)
• Why have European honeybee populations declined in
the United States in the last
decade? (Many European
honeybees have been killed
by diseases, parasites, and
pesticides.)
Graphic Organizer
Use this graphic organizer with
Teaching Tip on this page.
Pollen grains
with 2 sperm
Sperm (n)
+
egg (n)
Fertilization
Zygote
2n
Sperm (n)
+
2 nuclei (n)
Fertilization
Endosperm
3n
Pollination
Flowers
Ovules with
1 egg
Chapter 24 • Plant Reproduction
539
Life Cycle of an Angiosperm
Figure 11 summarizes the life cycle of an angiosperm. Following fer-
tilization, the zygote and the tissues of the ovule develop into a seed,
which grows into a new sporophyte. The adult sporophytes of
angiosperms produce spores by meiosis. These spores grow into
gametophytes. The female gametophytes grow inside the ovules,
which develop within the ovary of a pistil. The male gametophytes,
or pollen grains, are produced in the anther of a stamen. A pollen
grain contains two sperm cells. One sperm fuses with the egg, forming the zygote. The other sperm fuses with the haploid nuclei of two
other cells produced by meiosis. The fusing of three haploid (n) cells
forms a triploid (3n) cell that develops into endosperm. This is a
process called double fertilization.
Close
Reteaching
Have students construct a crossword puzzle using the terms
presented in this section and the
definitions they wrote as directed
in the lesson opener Activity.
LS Verbal
Quiz
Figure 11 Angiosperm
life cycle. In angiosperms,
a large sporophyte alternates
with tiny gametophytes.
GENERAL
1. What do male and female gametophytes produce, respectively?
(sperm and eggs)
2. What are the three main components of a seed? (embryo,
endosperm, seed coat)
3. Which is larger in a conifer, the
sporophyte or the gametophyte?
(sporophyte)
Diploid (2n)
2
A flower produces male
spores inside its anthers
and female spores inside
its pistil.
Haploid (n)
Male spores
Anther
Meiosis
Stamen
Adult
sporophyte
Pollination
Gametophytes
Meiosis
Ovule
Flower
Ovule
the male equivalent of the pistil?
(the stamen)
Mitosis
Alternative
Assessment
Seed
coat
4
Pollination occurs
when a pollen grain
lands on the stigma
of a pistil.
Mature female spore
(female gametophyte)
3n nucleus
Endosperm
(3n)
1
Seed
Pollen
tube
Mitosis
The zygote and ovule develop
into a seed, which grows into
a new sporophyte.
Pollen
tube
Sperm
Sporophyte
embryo
Provide students with a variety of
cones and fruits. Try to include
pine, spruce, and fir cones. Try to
include peaches; tomatoes, grapes,
or blueberries; apples; beans; nuts;
strawberries; pineapple or figs; and
elm or maple fruits. Provide a
botany textbook or field guide
that students can use to classify
the fruits. LS Visual
Spores develop into
male and female
gametophytes.
Pollen grains
(male gametophytes)
Pistil
4. Which structure in a flower is
3
Double
fertilization
5
Egg
Zygote
Sperm enter an ovule
through a pollen tube,
and fertilization occurs.
Section 2 Review
Distinguish pollen grains from ovules.
TAKS 2 Bio 8C; Bio 8A, 8B, 10C, 13B
Describe the function of each part of a seed.
Summarize the life cycle of a conifer.
Critical Thinking Summarizing Information
5A 13B
13A
13B
Critical Thinking Relating Concepts How is
each part of a flower suited to its function?
13A
What are the main events in the life cycle of an
angiosperm?
13B
TAKS Test Prep In angiosperms, pollen is
13B TAKS 3 Bio 13A
produced in sacs called
A sepals.
C pistils.
B anthers.
D ovules.
540
Answers to Section Review
pp. 540–541
Student Edition
TAKS Obj 2 Bio 8C
TAKS Obj 3 Bio 7B
TAKS Obj 3 Bio 13A
TEKS Bio 5A, 7B, 8C, 13A, 13B
Teacher Edition
TAKS Obj 2 Bio 8C
TAKS Obj 3 Bio 13A
TEKS Bio 8A, 8B, 8C, 10C, 13A, 13B
540
1. A pollen grain is a male gametophyte that contains cells that form sperm cells and a pollen
tube. An ovule is a sporophyte structure that
contains a female gametophyte, in which an
egg cell forms. Bio 5A, 13B
2. The embryo is the young sporophyte, the food
reserves (endosperm) nourish the young sporophyte when the seed germinates, and the seed
coat protects the embryo from harsh environmental conditions. TAKS 3 Bio 13A
3. First, a zygote grows into a sporophyte by
mitotic cell division. Next, the sporophyte forms
male and female spores in cones following meiotic cell division. Then, the spores grow into
Chapter 24 • Plant Reproduction
male and female gametophytes by mitotic cell
division. After the gametophytes form eggs and
sperm by mitotic cell division, eggs are fertilized
by sperm and a new zygote forms. The zygote and
surrounding tissue develop into a seed. Bio 13B
4. Answers should summarize the information in
Figure 11. TAKS 3 Bio 13A
5. Answers may vary. Bio 13B
6.
A. Incorrect. The sepals protect
a flower from damage while it is a bud.
B. Correct. C. Incorrect. The pistils produce
ovules. D. Incorrect. The ovules produce
female gametophytes. TAKS 3 Bio 13A; Bio 13B
Asexual Reproduction
Section 3
Section 3
Focus
Vegetative Reproduction
Objectives
Most plants are able to reproduce asexually. The new individuals
that result from asexual reproduction are genetically the same
as the parent plant. Plants reproduce asexually in a variety of
ways that involve nonreproductive parts, such as stems, roots, and
leaves. The reproduction of plants from these parts is called
vegetative reproduction. Many of the structures by which plants
reproduce vegetatively are modified stems, such as runners, bulbs,
corms, rhizomes, and tubers. Table 1 describes these structures.
Vegetative reproduction is faster than sexual reproduction in
most plants. A single plant can spread rapidly in a habitat that is
ideal for its growth by reproducing vegetatively. Therefore, a mass of
hundreds or even thousands of individuals, such as a stand of
grasses or ferns, may have come from one individual. To learn about
one unique method of vegetative reproduction in one plant, look at
Up Close: Kalanchoë, on the next two pages.
Overview
● Describe several types of
vegetative reproduction in
plants.
13B
● Distinguish sexual reproduction in kalanchoës from
asexual reproduction in
kalanchoës.
13B
● Recommend several
ways to propagate
plants.
13A 13B TAKS 3
Key Terms
vegetative
reproduction
plant propagation
tissue culture
Bellringer
Ask students to think of examples
of how flowering plants reproduce
without making seeds. Help them
by asking about gardening, hiking,
or other nature experiences they
may have had. Students may have
seen clumps of plants of the same
type, strawberry runners, or clusters of bulbs. Ask students why all
the plants in a lawn might look the
same. (They are all clones from one
plant.) LS Interpersonal
Table 1 Stems Modified for Vegetative Reproduction
Name
Description
Runner
Horizontal, aboveground stem
Bulb
Very short, stem with
thick, fleshy leaves;
only in monocots
Corm
Very short, thickened,
underground stem with
thin, scaly leaves
Rhizome
Horizontal
underground stem
Tuber
Swollen, fleshy,
underground stem
Before beginning this section
review with your students the
objectives listed in the Student
Edition. The purpose of this lesson
is to introduce the different ways
that plants reproduce without
forming seeds. The lesson describes
asexual reproduction in one plant
species in detail. It concludes with
a discussion of how plants can be
propagated vegetatively.
Examples
Airplane plant,
Bermuda grass
Onion,
daffodil,
tulip
TAKS 3 Bio 13A; Bio 13B
Gladiolus,
crocus
Motivate
Demonstration
Iris, fern, sugar cane
Potato,
caladium
541
Chapter Resource File
• Lesson Plans GENERAL
• Directed Reading
• Active Reading GENERAL
• Data Sheet for
Exploration Lab GENERAL
Planner CD-ROM
• Reading Organizers
• Reading Strategies
• Supplemental Reading Guide
A Feeling for the Organism: The Life and
Work of Barbara McClintock
Show students example of bulbs
(lily, onion, tulip); corms (crocus,
gladiolus); rhizomes (iris); runners
(airplane plant, strawberry); and
tubers (potato). Point out that all
of these are modified stems and
therefore have buds that can grow
into new plants. Demonstrate vegetative propagation by rooting an
airplane plant or a potato. Be sure
to include a bud in the section
you set up for
English Language
Learners
rooting. LS Visual
TAKS 3 Bio 13A; Bio 10C, 13A
Transparencies
TT Bellringer
TT Stems Modified for Vegetative
Reproduction
Chapter 24 • Plant Reproduction
541
Up Close
Up Close
Kalanchoë TAKS 2, TAKS 3
Kalanchoë
Scientific name: Kalanchoë daigremontiana
TAKS 3 Bio 13A; Bio 10C, 13B
Teaching Strategies Bring
specimens of Kalanchoë daigremontiana to class. Let
students propagate the plant
by planting stem cuttings, leaf
cuttings, or plantlets.
• Point out to students that the
formation of plantlets along
the leaf margin that occurs in
kalanchoës is a very unusual
form of asexual reproduction
that occurs in only a few
species. Tell students that
these plants are often grown
commercially because of
their unusual appearance and
method of asexual reproduction. Also tell students that
because kalanchoës are easy
to grow, they often become
serious greenhouse weeds.
• For interest, take students to
a greenhouse where succulents are grown, or have a
horticulturist talk to students
about the characteristics and
propagation of kalanchoës
and other succulents.
• CAM photosynthesis may
be difficult for students to
comprehend. Help students
understand CAM photosynthesis by having them
illustrate the process.
LS Visual
Transparencies
TT External Structure of Kalanchoë
TT Internal Structures of Kalanchoë
Size: Grows from 30 cm (1 ft) to 1 m (3 ft) tall
Range: Native to southwestern Madagascar; cultivated
worldwide
Habitat: Semiarid tropical grassland with moist summers and
well-drained, fertile soil
Importance: Kalanchoës (kal an KOH eez) are grown as indoor
potted plants and as outdoor perennials in warm climates.
External Structures
Leaves The fleshy leaves are
bluish green, with purple markings
and saw-toothed margins. Leaf
blades range from 12 to 25 cm
(4 to 10 in.) long. Leaves are
arranged in pairs that are
opposite one another.
Flowers A cluster of flowers
forms on a flowering stalk that
grows from the end of a stem.
The flowers are bell-shaped and
about 2.5 cm (1 in.) long. Flower
parts occur in fours.
Each flower produces
many tiny seeds.
▲
Flower
▼ Plantlet
Plantlets Tiny new
plants develop along leaf
margins. These plantlets
are a means of vegetative
reproduction. When a
plantlet falls to the ground,
it grows into a new plant.
▼
▼ Leaf cutting
Air roots
Stem and leaf cuttings
Air roots The roots that grow
Kalanchoës are often propagated
vegetatively by planting stem
and leaf cuttings.
from the stems and from
plantlets originate from
stem tissue.
542
INCLUSION
Strategies
pp. 542–543
Student Edition
TAKS Obj 2 Bio 6D
TAKS Obj 3 Bio 13A
TEKS Bio 6D, 10C, 13A, 13B
Teacher Edition
TAKS Obj 2 Bio 6D, 8C
TAKS Obj 3 Bio 13A
TEKS Bio 6D, 8C, 10C, 13A, 13B
542
Many commercial fruit trees are composed of
two different plants. Fruit trees, such as those
that produce apples and citrus fruits, are typically composed of one variety (genotype) of a
species grafted onto another variety. The root
stock is often that of a hardy variety that can
withstand harsh environmental conditions and is
resistant to diseases common for that crop. The
scion (SEYE on), or the part that is grafted onto
the root stock, is a variety that has desirable
characteristics (such as flavor, color, early fruit
set), but it is not always well adapted to the environmental conditions under which it is grown.
Chapter 24 • Plant Reproduction
• Developmental Delay
Bring a variety of vegetation, such as those
listed in Table 1, for students to observe,
touch, and sketch during class. Placing them
in dirt, water, or in a cool dark place over
time will allow roots and stems to sprout
and begin to grow. The changes observed
each day should be discussed, recorded, and
drawn. Student understanding of the different stems used for vegetative reproduction
would be greater for having observed the
process in person. Bio 13B
Internal Structures
Up Close
Leaf structure Kalanchoës are succulents, which means
they have fleshy leaves and stems that store water.
A kalanchoë leaf shows how some succulents
are adapted for conserving water. A thick
cuticle covers the leaf, and the
epidermis (outer layer of cells)
consists of several layers of
cells. Relatively few, very
small stomata dot
the leaf surfaces.
Kalanchoë
Discussion
• Ask students to describe sexual and asexual reproduction
in kalanchoës. (Kalanchoës
are flowering plants that
reproduce sexually by forming
seeds following pollination
and fertilization. They reproduce asexually by forming
plantlets containing roots,
stems, and leaves on the margins of the mother plant’s
leaves. They can also produce
new plants from pieces of
stems and leaves.)
• Ask students how the genetic
composition of a plantlet
compares with that of the
mother plant. (The two are
identical because the plantlets
are clones of the mother plant.)
• Ask students to name some
adaptations found in kalanchoës that enable them to
survive in dry environments.
(Kalanchoës have thick, fleshy
leaves and stems that store
water; the leaves have a thick
cuticle, several layers of epidermal cells, and few stomata; the
plants photosynthesize using the
CAM process, which enables
them to have their stomata open
at night and capture energy
from the sun during the day.)
Cuticle
Epidermis
Mesophyll
Epidermis
Stoma
Vascular
bundle
▼
Central vacuole
Large central vacuole The cells inside
a leaf, called the mesophyll cells, have a
large central vacuole that can hold a great
deal of water.
Organelles
Mesophyll cell
Night
Day
Mesophyll cells
CO2
CO2
CAM photosynthesis Kalanchoës belong to the
Crassulaceae family, a group of succulent plants that are
adapted to hot climates. Photosynthesis in kalanchoës
involves a process called crassulacean acid metabolism (CAM).
The stomata of CAM plants open only at night, unlike those
of other plants. At night, the plants fix carbon dioxide by using it
to make malic acid. The malic acid is stored in the large central
vacuoles of the mesophyll cells. In daytime, the stomata remain
closed, which prevents water loss. Carbon dioxide is released
from malic acid during the day and used by the Calvin cycle to
make sugar.
Calvin
cycle
Malic
acid
Sugar
Central
vacuole
Cell
wall
Cell
membrane
Cytoplasm
LS Interpersonal
TAKS 2 Bio 6D (grade 10 only);
TAKS 3 Bio 13A
543
SOCIAL STUDIES
CONNECTION
Like Kalanchoë daigremontiana, many other
horticulturally important plants are natives of
Madagascar, which is an island off the southeast coat of Africa. One such plant is the rosy
periwinkle, Catharanthus roseus, which is a
popular bedding plant in the United States
and the original source of two cancer treatment drugs. Have students use the Internet to
research other economically important plants
to find out where they are grown and how
much income they bring to the countries
where they are grown. LS Interpersonal
did you know?
Asexual reproduction is energy efficient.
Asexual reproduction enables plants to
produce many offspring by using less energy
than is required for sexual reproduction.
However, because offspring produced asexually
are genetically identical to their parent, they
are all equally susceptible to any environmental
condition or disease to which the parent was
susceptible. Sexual reproduction results in
genetic variation among the offspring, which is
particularly advantageous when the environment
is very changeable or when new disease-causing
agents enter the environment.
TAKS 2 Bio 8C; TAKS 3 Bio 13A; Bio 13B
Chapter 24 • Plant Reproduction
543
Plant Propagation
Close
Reteaching
Ask students to describe characteristics of plants that would indicate
that they have been asexually propagated. (uniformity of appearance, as
in flower color, fruit color and size,
plant size, etc.) Bio 13B
Quiz
People grow plants for many purposes, such as for food, to beautify
homes, or to sell. Most field crops, such as cereal grains, vegetables,
and cotton, are grown from seed. Many other plants are grown from
vegetative parts. Growing new plants from seed or from vegetative
parts is called plant propagation.
Plants are often propagated using the structures the plants produce
for vegetative reproduction. Bulbs and corms divide as they grow,
forming many pieces that can each grow into a new
plant. Rhizomes, roots, and tubers can be cut or
broken into pieces with one or more buds that can
grow into new shoots. But people also grow plants
from vegetative parts that are not specialized for
vegetative reproduction. For example, pieces of
plants, such as the stems of ivys and the leaves of
African violets, are cut from the parent plant. The
cuttings are then used to grow new plants. Figure 12
shows a method of propagating trees called budding. In another technique called tissue culture,
pieces of plant tissue are placed on a sterile medium
and used to grow new plants. Table 2 summarizes
some of the methods of vegetative plant propagation
that are widely used to grow plants.
Figure 12 Budding pears.
A bud from a desirable variety
of pears is attached to a stem
of another pear species. The
bud will grow into a branch
that produces the desirable
variety of pears.
GENERAL
1. What is the most common part
of a plant that is involved in
asexual reproduction? (stems) Bio 13B
2. Can plants that reproduce asexually also reproduce sexually?
(yes) Bio 13B
3. How do CAM plants compare
with most other plants in the
way in which they undergo photosynthesis? (CAM plants have
their stomata open at night, when
the stomata of most other plants
are closed. Carbon dioxide is fixed
during the night, stored, and then
used in the Calvin cycle to make TAKS 3
sugar during the day.) LS Verbal Bio 13A
Alternative
Assessment
Table 2 Methods of Vegetative Plant Propagation
Method
Description
Examples
Budding
and grafting
Small stems from one plant are attached to
larger stems or roots of another plant.
Grape vines, hybrid roses, fruit and
nut trees
Taking
cuttings
Leaves or pieces of stems or roots are cut from
one plant and used to grow new individuals.
African violets, ornamental trees and
shrubs, figs
Tissue
culture
Pieces of tissue from one plant are placed on a
sterile medium and used to grow new individuals.
Orchids, potatoes, many houseplants
GENERAL
Garden Design Have students use
poster board to design a garden
that includes both sexually and
asexually reproducing plants. Have
students include the name of each
plant and how it reproduces in
table format.
English Language
Section 3 Review
Describe four types of vegetative reproduction
Critical Thinking Justifying Conclusions
in plants, and give an example of each.
Why would someone choose to propagate a
particular plant for commercial purposes by
using vegetative structures instead of seed?
13B
Classify methods of reproduction in kalanchoës
as sexual or asexual.
Learners
TAKS 1 Bio/IPC 2C; TAKS 2 Bio 8C, 13B
Recommend five ways to propagate plants.
Transparencies
TT Methods of Vegetative Plant
Propagation
13B
13B
13B
TAKS Test Prep Bermuda grass reproduces
asexually by means of horizontal, aboveground
13B 13A TAKS 2
stems called
A corms.
C tubers.
B rhizomes.
D runners.
544
Answers to Section Review
pp. 544–545
Student Edition
TAKS Obj 3 Bio 13A
TEKS Bio 7B, 8C, 13A, 13B
Teacher Edition
TAKS Obj 1 Bio/IPC 2C
TAKS Obj 2 Bio 8C
TAKS 3 Bio 13A
TEKS Bio 8C, 13A, 13B
TEKS Bio/IPC 2C
544
1. Bulbs are short stems with thick, fleshy leaves
(daffodil, onion, tulip); corms are short, thickened underground stems with thin, scaly leaves
(crocus, gladiolus); rhizomes are horizontal
underground stems (fern, iris, sugar cane);
tubers are swollen, fleshy, underground stems
(potato, caladium); runners are aerial stems
that form roots (airplane plant, kalanchoë);
plantlets form on leaves (kalanchoë) Bio 13B
2. Formation of seeds is sexual reproduction.
Formation of plantlets on the leaf margins or
growth of new plants from pieces of stems or
leaves is asexual reproduction. Bio 13B
Chapter 24 • Plant Reproduction
3. planting seeds; planting vegetative reproductive
structures such as bulbs, corms, tubers, rhizomes, or plantlets; budding or grafting; taking
stem or leaf cuttings; tissue culture Bio 13B
4. Someone might choose to propagate a plant
commercially using vegetative structures to
produce a new crop rapidly and/or to produce
a crop of identical plants. Bio 13B
5.
A. Incorrect. Corms are short,
underground stems. B. Incorrect. Rhizomes are
horizontal, underground stems. C. Incorrect.
Tubers are swollen, fleshy, underground stems.
D. Correct. TAKS 2 Bio 13A; Bio 13B
Study
CHAPTER HIGHLIGHTS
ZONE
Key Concepts
●
In mosses, the “leafy” green gametophytes are larger than the
sporophytes, which consist of a bare stalk and a spore capsule.
●
In the life cycle of a fern, the sporophytes are much larger
than the gametophytes. The thin, green, heart-shaped
gametophytes produce both sperm and eggs.
●
Nonvascular plants and seedless vascular plants need water
for fertilization because sperm must swim to eggs.
archegonium (530)
antheridium (530)
sorus (532)
Section 2
2 Sexual Reproduction in Seed Plants
The tiny gametophytes of seed plants develop from spores
that remain within sporophyte tissues. Male gametophytes
develop into pollen grains. Female gametophytes develop
inside ovules.
●
A seed contains an embryo, which is a new sporophyte, and
a supply of nutrients for the embryo. The cotyledons of an
embryo help transfer nutrients to the embryo. A seed coat
covers and protects a seed.
●
In gymnosperms, male and female gametophytes develop in
separate cones on the sporophytes. After fertilization, ovules
develop into seeds, which grow into new sporophytes.
●
Flowers have four types of parts—petals, sepals, stamens,
and pistils. Petals attract pollinators. Sepals protect buds and
may also attract pollinators. Pollen forms in the anthers of
stamens. Seeds develop in the ovary of a pistil.
●
In angiosperms, male and female gametophytes develop
in the flowers of the sporophytes. After fertilization, ovules
develop into seeds, which grow into new sporophytes.
3 Asexual Reproduction
GENERAL
Assign students to four cooperative
groups. Have each group draw and
label a life cycle diagram of a different type of plant (moss, fern,
gymnosperm, angiosperm). Collect
the diagrams, and then redistribute
them to the groups for evaluation,
making sure that none of the
groups gets its own diagram back.
Discuss each life cycle diagram,
making corrections as necessary.
Section 1
1 Sexual Reproduction in Seedless Plants
●
Alternative
Assessment
Key Terms
pollen grain (534)
ovule (534)
pollination (534)
pollen tube (534)
seed coat (535)
cotyledon (535)
sepal (538)
petal (538)
stamen (538)
anther (538)
pistil (538)
ovary (538)
double fertilization (540)
Chapter Resource File
• Science Skills Worksheet
• Critical Thinking
Worksheet
• Test Prep Pretest GENERAL
• Chapter Test GENERAL
GENERAL
Section 3
●
Vegetative reproduction is the growth of new plants from
nonreproductive plant parts, such as stems, roots, and leaves.
●
Kalanchoës are succulents that are often grown as potted
plants and readily reproduce either vegetatively or by seeds.
●
People often grow plants from their vegetative structures.
This is called vegetative propagation.
vegetative reproduction (541)
plant propagation (544)
tissue culture (544)
545
Answer to Concept Map
Plants reproduce
The following is one of several possible
answers to Performance Zone item 15.
sexual reproduction
by
which involves
eggs
which are produced in
sperm
fertilization
asexual reproduction
archegonia
which involves
in
spores
vegetative
reproduction
female cones
of
gymnosperms
stems
leaves
within
seedless plants
with
roots
ovules
club mosses
which are produced in
anthers
that fuse during
to produce a
zygote
antheridia
of
in
stamens
seedless
plants
in
ovaries
male cones
that are part of
of
pistils
gymnosperms
flowering
plants
club mosses
in
flowering plants
Chapter 24 • Plant Reproduction
545
Performance
ZONE
CHAPTER 24
ANSWERS
Using Key Terms
1. a Bio 5A, 13B
2. d Bio 5A, 13B
3. b Bio 13B
4. a Bio 5A, 13B
5. a. Pollen grains are mature male
gametophytes that consist of
only two or three cells and
produce sperm cells. An ovule
is a multicellular structure that
develops in a female cone or in
the ovary of a flower and in
which a female gametophyte
that contains an egg cell
develops.
b. A sepal encloses and protects a
flower bud, while a petal usually attracts animal
pollinators.
c. A cotyledon is a structure of a
plant embryo in all seeds, and
endosperm is a triploid food
supply that is not part of the
embryo and is found only in
angiosperm seeds.
d. Reproduction is the process by
which organisms produce offspring. Propagation is the
process of producing plants
(or other organisms) from a
seed or from vegetative
structures.
and ferns is called a(n)
13B
a. archegonium.
c. ovule.
b. sporangium.
d. antheridium.
546
kalanchoës produce for vegetative
13B
reproduction?
a. seeds
c. flowers
b. plantlets
d. bulbs
from a pollen grain directly to an egg in
an ovule.
13B
a. pollinator
c. endosperm
b. seed coat
d. pollen tube
11. Which of the following structures is not used
to propagate dicots vegetatively?
13B
a. tubers
c. bulbs
b. rhizomes
d. stem cuttings
3. In conifers, the sporophyte produces spores
and gametophytes in
13B
a. flowers.
c. sori.
b. cones.
d. sporangia.
4. Which part of a flower produces eggs?
a. pistil
c. stamen
b. petal
d. sepal
13B
10. Which of the following structures do
2. In seed plants, the ____ transfers sperm
12. Look at the flower in the photograph
below. It is the flower of the unicorn plant.
How is this flower probably pollinated?
Justify your answer.
13B
13B
5. For each pair of terms, explain the
difference in their meanings.
a. pollen grain, ovule
b. sepal, petal
c. cotyledon, endosperm
d. reproduction, propagation
Understanding Key Ideas
6. Mosses and liverworts thrive in a moist
environment because they need _____ for
reproduction.
13B
a. bees
c. water
b. birds
d. wind
7. The life cycle of a moss differs from the life
cycle of a fern in that
13B
a. the gametophyte is absent in ferns.
b. the sporophyte is absent in mosses.
c. moss spores do not form on leaves.
d. the gametophytes of mosses are green.
8. In angiosperms, the zygote and the first cell
of the endosperm form by
a. mitosis.
b. meiosis.
c. pollination.
d. double fertilization.
13B
13.
What is being done to
counter biological threats to honeybees
in Texas?
14. What is the function of the fruits in which
seeds mature? (Hint: See Chapter 23,
Section 1.)
13B
15.
Concept Mapping Make a concept
map that explains how plants reproduce.
Try to include the following terms in
your map: archegonium, antheridium, egg,
sperm, ovule, zygote, stamen, anther, pistil,
ovary, fertilization, spore, and vegetative
reproduction.
3E
546
12. Students should recognize that this flower is
probably bee pollinated because it is yellow,
has a landing platform, and has pollen guides
showing the location of nectar.
TAKS 3 Bio 12B, Bio 13B
pp. 546–547
Review and Assess
TAKS Obj 2 Bio 8C
TAKS Obj 3 Bio 7B, 12B
TEKS Bio 3B, 5A, 7B, 8C, 13A, 13B
when a new plant grows from a
a. leaf.
c. stem.
b. root.
d. seed.
1. A structure that produces eggs in mosses
6. c TAKS 3 Bio 7B, TAKS 2 Bio 8C,
Bio 13B
Bio 13B
Bio 5A, 13B
Bio 5A, 13B
Bio 13B
Bio 13B
9. Vegetative reproduction has not occurred
Using Key Terms
Understanding Key Ideas
7. c
8. d
9. d
10. b
11. c
CHAPTER REVIEW
13. Scientists are testing chemicals that can be
used against varroa mites and small hive beetles and developing new antibiotics that will
be effective against bacteria that cause
American foulbrood.
14. The dispersal of seeds is the main function of
fruits. TAKS 3 Bio 7B, Bio 13B
Chapter 24 • Plant Reproduction
Assignment Guide
Section
1
2
3
Questions
1, 6, 7, 15, 16, 22
2, 3, 4, 5, 8, 12, 13, 14, 15, 17, 18,
19, 22
5, 9, 10, 11, 19, 20, 21, 22
Critical Thinking
Alternative Assessment
Critical Thinking
16. Evaluating Conclusions All nonvascular
20. Finding Information Use the media center
16. Answers will vary. Students
should offer evidence to support
their conclusion. Some students
may recognize that this conclusion is not valid because nonvascular plants are found in dry
climates. These plants survive in
shady spots under trees and
rocks, where moisture accumulates occasionally, and near
springs, creeks, and rivers.
plants require a film of water for sperm to
swim through and fertilize eggs. Therefore,
many people conclude that nonvascular
plants are not able to survive in very dry
climates, such as deserts. Is this a valid
conclusion? Justify your answer.
13A
17. Justifying Conclusions A classmate has
found a plant whose flowers lack petals
and have many stamens. Your classmate
tells you that the plant is wind-pollinated.
Justify this conclusion.
13B
18. Applying Information Explain how pesti-
cide use could reduce the number of plants
in a geographic area.
19. Evaluating Methods You are asked to grow
a large number of identical potted plants
for a florist. The plants can be grown from
either seeds or cuttings. Which method of
plant propagation would you use? Justify
your choice.
13B
or Internet sources to find out how the
plants commonly sold in your local garden
centers and plant nurseries are propagated.
Write a report summarizing the most common method used to propagate each of the
plants you researched. Explain why each
plant is usually propagated by this method
instead of another method.
13B
21. Working Cooperatively Go with two or three
of your classmates to visit a wholesale plant
grower. Orchid growers would be an excellent choice if one is in your area. Find out
how tissue culture is used to propagate
different kinds of plants. Try to find out
information on two methods of vegetative
propagation that are not described in this
chapter. Prepare an illustrated report of your
findings to share with the class.
13B
22. Career Connection Plant Breeder Use the
media center or Internet to find out about
the field of plant breeding. Write a report on
your findings. Your report should include a
job description, the training required, names
of employers, growth prospects, and an
average starting salary.
3D
TAKS Test Prep
Use the drawing of a plant seed below and your
knowledge of science to answer questions 1–3.
1. Which structure is the embryonic root?
A A
C C
B B
D D
13B
2. Which structure is the source of nutrients
A
for the embryo?
F A
G B
B
C
D
13B
13B
Test
Choose the best possible answer for each question,
even if you think there is another possible answer
that is not given.
547
Standardized Test Prep
1. A. Incorrect. A shows the endosperm.
B. Correct. C. Incorrect. C shows the cotyledon. D. Incorrect. D shows the seed coat.
Bio 13B
2. F. Correct. G. Incorrect. The embryonic
root gives rise to the mature plant root.
H. Incorrect. The cotyledon transfers nutrients
to the embryo. J. Incorrect. The seed coat
protects the plant embryo. Bio 13B
3. A. Incorrect. Nonvascular plants reproduce by
spores. B. Incorrect. Gymnosperms do not
have cotyledons. C. Incorrect. Dicots have two
cotyledons. D. Correct. Bio 13B
17. The primary role of petals is
to attract animal pollinators.
Therefore, the absence of petals is
a strong indication that the plant
is wind-pollinated. Bio 13B
18. Pesticides can kill insect pollinators such as bees and flies.
Reducing the number of insect
pollinators in an area can result
in a reduced number of flowering
plants which depend on insect
pollination.
19. Answers will vary, but students
should recommend a type of
vegetative propagation, such as
cuttings or tissue culture since
these methods produce plants that
are genetically identical to each
other and to their parent plant.
Bio 13B
H C
J D
3. What type of plant produced this seed?
A nonvascular
C dicot
plant
D monocot
B gymnosperm
TAKS 2 Bio 8C, TAKS 3 Bio 13A
Alternative Assessment
20. Answers will vary. Bio 13B
21. Answers will vary. Bio 13B
22. Plant breeders are scientists who
work to improve plants that have
commercial value. Plant breeders
make crosses between plants that
have desirable characteristics and
select plants with the most desirable combination of traits. Some
plant breeders use genetic engineering in their work. Plant
breeders work for universities,
federal agencies, and private
industries. To become a plant
breeder, you must obtain a
master’s degree or a Ph.D. in
agronomy, horticulture, or plant
breeding. Starting salary will vary
by region. Bio 3D
Chapter 24 • Plant Reproduction
547