Table of Contents – pages iv-v Unit 1: What is Biology? Unit 2: Ecology Unit 3: The Life of a Cell...

Unit 1: What is Biology?Unit 2: EcologyUnit 3: The Life of a CellUnit 4: GeneticsUnit 5: Change Through TimeUnit 6: Viruses, Bacteria, Protists, and FungiUnit 7: PlantsUnit 8: InvertebratesUnit 9: VertebratesUnit 10: The Human Body

Unit 1: What is Biology?

Chapter 1: Biology: The Study of LifeUnit 2: Ecology Chapter 2: Principles of Ecology Chapter 3: Communities and Biomes Chapter 4: Population Biology Chapter 5: Biological Diversity and ConservationUnit 3: The Life of a Cell Chapter 6: The Chemistry of Life Chapter 7: A View of the Cell Chapter 8: Cellular Transport and the Cell Cycle Chapter 9: Energy in a Cell

Unit 4: Genetics

Chapter 10: Mendel and Meiosis

Chapter 11: DNA and Genes

Chapter 12: Patterns of Heredity and Human Genetics

Chapter 13: Genetic Technology

Unit 5: Change Through Time Chapter 14: The History of Life Chapter 15: The Theory of Evolution Chapter 16: Primate Evolution Chapter 17: Organizing Life’s Diversity

Unit 6: Viruses, Bacteria, Protists, and Fungi

Chapter 18: Viruses and Bacteria

Chapter 19: Protists

Chapter 20: Fungi

Unit 7: Plants

Chapter 21: What Is a Plant?

Chapter 22: The Diversity of Plants

Chapter 23: Plant Structure and Function

Chapter 24: Reproduction in Plants

Unit 8: Invertebrates

Chapter 25: What Is an Animal?

Chapter 26: Sponges, Cnidarians, Flatworms, and

Roundworms

Chapter 27: Mollusks and Segmented Worms

Chapter 28: Arthropods

Chapter 29: Echinoderms and Invertebrate

Chordates

Unit 9: Vertebrates Chapter 30: Fishes and Amphibians

Chapter 31: Reptiles and Birds

Chapter 32: Mammals

Chapter 33: Animal Behavior

Unit 10: The Human Body

Chapter 34: Protection, Support, and Locomotion

Chapter 35: The Digestive and Endocrine Systems

Chapter 36: The Nervous System

Chapter 37: Respiration, Circulation, and Excretion

Chapter 38: Reproduction and Development

Chapter 39: Immunity from Disease

Plants

What is a Plant?

The Diversity of Plants

Plant Structure and Function

Reproduction in Plants

Chapter 24 Introduction: Reproduction in Plants

24.1: Life Cycles of Mosses, Ferns, and Conifers

24.1: Section Check

24.2: Flowers and Flowering

24.2: Section Check

24.3: The Life Cycle of a Flowering Plant

24.3: Section Check

Chapter 24 Summary

Chapter 24 Assessment

What You’ll Learn

You will compare and contrast the life cycles of mosses, ferns, and conifers.

You will sequence the life cycle of a flowering plant.

You will describe the characteristics of flowers, seeds and fruits.

• Review the steps of alternation of generations.

Section Objectives:

Section Objectives:

• Survey and identify methods of reproduction and the life cycles of mosses, ferns, and conifers.

• An alternation of generations consists of a sporophyte stage and a gametophyte stage.

• All cells of a sporophyte are diploid.

Alternation of GenerationsAlternation of Generations

• Certain cells of a sporophyte undergo meiosis, which produces haploid spores.

• These spores undergo cell divisions and form a multicellular, haploid gametophyte.


• The female gamete is an egg and the male is a sperm.

• When a sperm fertilizes an egg, a diploid zygote forms. This is sexual reproduction.


• If the embryo develops to maturity, the cycle can begin again.

• This basic life cycle pattern is the same for most plants. However, there are many variations on this pattern within the plant kingdom.

• Most people have never even seen the female gametophyte of a flowering plant.


• Botanists usually refer to the bigger, more obvious plant as the dominant generation.

• The dominant generation lives longer and can survive independently of the other generation.


Dominant generation

• Most plants also can reproduce asexually by a process called vegetative reproduction.

• The new plants have the same genetic makeup as the original plant.

• In this type of reproduction, new plants are produced from existing plant organs or parts of organs.

Asexual reproductionAsexual reproduction

Asexual reproductionAsexual reproduction

• The new plants have the same genetic makeup as the original plant.

• The gametophyte stage is the dominant generation in mosses.

• A haploid moss spore can germinate and grow to form a protonema (proh tuh NEE muh). It is a small green filament of cells that can develop into the gametophyte.

Life Cycle of MossesLife Cycle of Mosses


Male gametophyte (n)

Female gametophyte (n)

GAMETOPHYTE GENERATION

Sperm

Egg

Mitosis

Zygote (2n)

Fertilization

Gametophyte (n)

SPOROPHYTE GENERATION

2n

Developing sporophyte

Sporophyte

(2n)

Capsule

Meiosis

Capsule opens releasing spores

Germinating spores

Protonema

n

• Some moss gametophytes also reproduce by vegetative reproduction.

• They can break into pieces when dry and brittle then, when moisture returns, each piece can grow and form a protonema then a gametophyte.


• Unlike mosses, the dominant stage of the fern life cycle is the sporophyte stage.

• The fern sporophyte includes the familiar fronds.

• On the underside of some fronds are sori, which are clusters of sporangia.

Life Cycle of FernsLife Cycle of Ferns

• Meiosis occurs within the sporangia, producing haploid spores.


• A spore can germinate to form a heart-shaped gametophyte called a prothallus

• The prothallus produces both archegonia and antheridia on its surface.

Prothallus

Archegonium

Antheridium


• The flagellated sperm released by antheridia swim through a film of water to eggs in archegonia. If fertilization occurs, the diploid zygote can develop into the sporophyte.

• Once the sporophyte produces green fronds, it can carry on photosynthesis and survive on its own.


Click image to view movie.


• The mature fern sporophyte consists of a rhizome from which roots and fronds grow.

Roots

Rhizome

Fronds


Prothallus Archegonium

Egg

Rhizoids

Antheridium

Spores (n)

Growing prothallus

Sperm

Fertilization

Zygote

Roots

RhizomeFronds

Cell divisions

Sorus

Sporangium

Meiosis


2n


n


The Life Cycle of ConifersThe Life Cycle of Conifers

• The dominant stage in conifers is the sporophyte generation.

• The adult conifer produces male and female cones on separate branches of one plant.

• Cones contain spore-producing structures, or sporangia, on their scales.


• Female cones, which are larger than the male cones, develop two ovules on the upper surface of each cone scale.

• A megaspore is a female spore that eventually becomes the female gametophyte.


• Male cones have sporangia that undergo meiosis to produce male spores called microspores.

• Each microspore can develop into a male gametophyte, or pollen grain.


• In conifers, pollination is the transfer of pollen grains from the male cone to the female cone.

EggPollen grain

Micropyle


• The opening of the ovule is called the micropyle (MI kruh pile).

• The pollen grain adheres to a sticky drop of fluid that covers the micropyle. As the fluid evaporates, the pollen grain is drawn closer to the micropyle.


• Although pollination has occurred, fertilization does not take place for at least a year.

• As the pollen grain matures, it produces a pollen tube that grows through the micropyle and into the ovule.


• A sperm nucleus from the male gametophyte moves through the pollen tube to the egg.

• If fertilization occurs, a zygote forms.

• A seed coat forms around the ovule as the mature seed is produced. Mature seed are released when the female cone opens.

The Life Cycle of ConifersThe Life Cycle of ConifersOvuleFemale cone

Male cone

Megaspores

MicrosporesMicrospore mother cell

Meiosis

Female gametophyte

Two archegonia with egg cells

Male gametophyte (pollen grain)


n

Egg

Pollen grain

Micropyle

Fertilization

Sperm nucleus

Maturing pollen grain

One egg is fertilized

Stored food

Embryo

Cotyledons

Seed coat

Seed

SPOTOPHYTE GENERATION

2n

Young seedling

Adult sporophyte

Question 1

D. They are structures of liverworts.

C. They are diploid.

B. They have the same genetic makeup as the original plant.

A. They are an example of vegetative reproduction.

Which of the following is NOT true of gemmae?

The answer is C. Gemmae are haploid.

Male gametophyte (n)

Female gametophyte (n)


Sperm

Egg

Mitosis

Zygote (2n)

Fertilization

Gametophyte (n)


2n

Developing sporophyte

Sporophyte

(2n)

Capsule

Meiosis

Capsule opens releasing spores

Germinating spores

Protonema

n

Question 2

This figure represents mosses because it reveals a dominant gametophyte generation and displays the presence of a protonema.

Question 3

D. mosses

C. conifers

B. liverworts

A. ferns

A prothallus is a structure belonging to _______.

The answer is A, ferns.

• Identify the organs of a flower.

Section Objectives:

• Examine how photoperiodism influences flowering.

What is a flower?What is a flower?

• The process of sexual reproduction in flowering plants takes place in a flower, which is a complex structure made up of several organs.

The structure of a flowerThe structure of a flower

• A flower’s structure is genetically determined and usually made up of four kinds of organs: sepals, petals, stamens, and pistils.

The structure of a flowerThe structure of a flower

Modifications in flower structureModifications in flower structure

• A flower that has all four organs—sepals, petals, stamens, and pistils—is called a complete flower.

Modifications in flower structureModifications in flower structure• A flower that lacks one or more organs is

called an incomplete flower.

• For example the flowers of plants such as sweet corn, and grasses, have no petals and are adapted for pollination by wind rather than by animals.

PhotoperiodismPhotoperiodism

• The relative lengths of daylight and darkness each day have a significant effect on the rate of growth and the timing of flower production in many species of flowering plants.

• The response of flowering plants to daily daylight-darkness conditions is called photoperiodism.


• Plant biologists originally thought that the length of daylight controlled flowering.

• However, they now know that it is the length of darkness that controls flowering, and that the darkness must be uninterrupted.


• Plants are short-day plants, long-day plants, day-neutral plants, or intermediate day plants.

• A short-day plant flowers when the number of daylight hours is shorter than that of its critical period.

PhotoperiodismPhotoperiodism• Short-day plants usually flower sometime

during late summer, fall, winter, or spring.

PhotoperiodismPhotoperiodism• A long-day plant flowers when the number

of daylight hours is longer than that of its critical period.

• Long-day plants usually flower in summer, but also will flower if lighted continually.


• Some plants will flower over a range in the number of day-light hours. These plants are called day-neutral plants.

• An intermediate-day plant will not flower if days are shorter or longer than its critical period.

PhotoperiodismPhotoperiodism• Photoperiodism is a

physioloical adaptation of all flowering plants that ensures the production of flowers at a time when there is an abundant population of pollinators.

Question 1

D. anther

C. stigma

B. sepal

A. peduncle

In flowers, the _______ receives the pollen.

The answer is C, stigma.

Petals

Stigma

Style

Ovary

Pistil

Peduncle

Sepal

Filament

AntherStamen

Question 2

D. day-neutral plants

C. intermediate-day plants

B. long-day plants

A. short-day plants

Plants that flower year-round are most likely to be _______.

The answer is D, day-neutral plants.

Question 3

D. styles

C. sepals

B. anthers

A. stamens

The _______ encircle the peduncle below the petals.

The answer is C, sepals.

Petals

Stigma

Style

Ovary

Pistil

Peduncle

Sepal

Filament

AntherStamen

• Survey and identify the methods of reproduction, growth, and development in flowering plants.

Section Objectives:

• Outline the processes in which cells differentiate during the formation of seeds and fruits and during seed germination.

The Life Cycle of an AnthophyteThe Life Cycle of an Anthophyte• The life cycle of flowering plants is similar to

that of conifers in many ways.

Pollen sac with microspore mother cells

Anther

Ovary

Adult sporophyte plant

Young seedling

Germinating seed

Seed

Fruit with seeds

Endosperm nucleus

ZygotePollen tube

Pollen tube

Female gametophyte

Egg

Double fertilization

Fertilization


2n


Four megaspores

Ovule with megaspore mother cell

Microspores in fours Pollen grain

Meiosis

Sperm

Tube nucleus

Male

gametophyte

The Life Cycle of an Anthophyte

The Life Cycle of an Anthophyte

n

Development of the female gametophyteDevelopment of the female gametophyte

• In anthophytes, the female gametophyte is formed inside the ovule within the ovary.

• In the ovule, a cell undergoes meiosis and produces haploid megaspores.

• In most flowering plants, the megaspore’s nucleus undergoes mitosis three times, producing eight haploid nuclei.

• The two remaining nuclei, which are called polar nuclei, are enclosed in one cell.

Development of the female gametophyteDevelopment of the female gametophyte• These eight nuclei make up the female

gametophye. Cell walls form around each of six nuclei, one of which is now called the egg cell.

• This cell, the central cell, is located at the center of the female gametophyte.

Development of the female gametophyteDevelopment of the female gametophyte

• The other five cells eventually disintegrate.

Embryo sac (female gametophyte)

Central cell

Egg cell

Micropyle

Ovule

• Haploid microspores are produced by meiosis within the pollen sac.

• The nucleus of each microspore undergoes mitosis.

• A thick, protective wall surrounds these two nuclei. This structure is the immature male gametophyte, or pollen grain.

Development of the male gametophyteDevelopment of the male gametophyte

Development of the male gametophyteDevelopment of the male gametophyte• When the pollen grains mature, the anther

usually splits open.

Pollen sacs

ANTHER

Microspore mother cell (2n)

Generative nucleus

Tube nucleus

Pollen grain(male gametophyte)

Microspores(n)

MEIOSIS

PollinationPollination

• In anthophytes, pollination is the transfer of the pollen grain from the anther to the stigma.

• Depending on the type of flower, the pollen can be carried to the stigma by wind, water, or animals.

• Most anthophytes that are pollinated by animals produce nectar in their flowers.


• Nectar is a liquid made up of proteins and sugars and usually collects in the cuplike area at the base of petals.

• Animals, such as insects and birds, brush up against the anthers while trying to get to the nectar.


• The pollen that attaches to them can be carried to another flower, resulting in pollination.


• Some of the bright, vivid flowers attract pollinators, such as butterflies and bees.

PollinationPollination• Flowers that are pollinated by beetles and

flies have a strong scent but are often dull in color.

• Many flowers have structural adaptations that favor cross-pollination—pollination between two plants of the same species.

• This results in greater genetic variation because a sperm from one plant fertilizes an egg from another.

FertilizationFertilization• Inside each pollen grain are two haploid nuclei,

the tube nucleus and the generative nucleus.Pollen grainStigma

Style

Ovary

Central cell

Ovule

Egg cell

Two sperm nuclei

Pollen tube

Tube nucleus

• The tube nucleus directs the growth of the pollen tube down through the pistil to the ovary.

• The generative nucleus divides by mitosis, producing two sperm nuclei.

FertilizationFertilization

• The sperm nuclei move through the pollen tube to a tiny opening in the ovule called the micropyle.


Pollen grainStigma

Style

Ovary

Central cell

Ovule

Egg cell

Two sperm nuclei

Pollen tube

Tube nucleus

• One of the sperm unites with the egg forming a diploid zygote, which begins the new sporophyte generation.

• The other sperm nucleus fuses with the central cell, which contains the polar nuclei, to form a cell with a triploid (3n) nucleus.

Double Fertilization

One sperm fertilizes the central cell (3n)

One sperm fertilizes the egg cell (2n)


• This process, in which one sperm fertilizes the egg and the other sperm joins with the central cell, is called double fertilization.

• The triploid nucleus will divide many times, eventually forming the endosperm of the seed.

• The endosperm is food storage tissue that supports development of the embroyo in anthophyte seeds.


Seeds and FruitsSeeds and Fruits

Ovary

Fused petals

Stamen

Ovules

Sepals

Fruit

Seed formationSeed formation

• After fertilization takes place, seed development begins.

• Inside the ovule, the zygote divides and develops into the embryo plant.

• The triploid central cell develops into the seed’s endosperm.

Seed formationSeed formation• The wall of the

ovule becomes the seed coat, which can aid in seed dispersal and help protect the embryo until it begins growing.

Seed formationSeed formation


Fruit formationFruit formation

• As the seeds develop, the surrounding ovary enlarges and becomes the fruit.

• A fruit is the structure that contains the seeds of an anthophyte.

• A fruit is as unique to an anthophyte as is its flower, and many anthophytes can be identified by examining their fruits.

Fruit formationFruit formation• Some plant foods

that we call vegetables or grains are actually fruits.

• For example, green peppers are fleshy fruits that are often referred to as vegetables.

Fruit formationFruit formation


Seed dispersalSeed dispersal• The dispersal of seeds is important because it

reduces competition for sunlight, soil, and water between the parent plant and its offspring.

• Animals such as raccoons, deer, bears, and birds help distribute many seeds by eating fruits.

Seed dispersalSeed dispersal• Seeds that are eaten usually pass through the

digestive system undamaged and are deposited in the animal’s wastes.

• Plants that grow in or near water, produce fruits or seeds with air pockets in the walls that enable them to float and drift away from the parent plant.

Seed dispersalSeed dispersal

• The ripened fruits of many plants split open to release seeds with structural adaptations for dispersal by wind or by clinging to animal fur.

Seed germinationSeed germination

• At maturity, seeds are fully formed.

• The seed coat dries and hardens, enabling the seed to survive environmental conditions that are unfavorable to the parent plant.

• The seeds of some plant species must germinate within a short period of time or die.

Seed germinationSeed germination

• The seeds of some plant species can remain in the soil until conditions are favorable for growth and development of the new plant.

• This period of inactivity in a mature seed is called dormancy. The length of time a seed remains dormant can vary from one species to another.

Seed germinationSeed germination• Even under harsh conditions, the seeds of

desert wildflowers and some conifers can survive dormant periods of 15 to 20 years.

Requirements for germinationRequirements for germination• Germination is the beginning of the

development of the embryo into a new plant.

Requirements for germinationRequirements for germination

• Once metabolism has begun, the seed must continue to receive water or it will die.

• Just before the seed coat breaks open, the rate of respiration in the plant embryo increases rapidly.

• Some seeds have specific requirements for germination.

• Water is important because it activates the embryo’s metabolic system.

Requirements for germinationRequirements for germination• For example, some germinate more readily

after they have passed through the acid environment of an animal’s digestive system.

• The seeds of some conifers will not germinate unless they have been exposed to fire.

Requirements for germinationRequirements for germination

Vegetative reproductionVegetative reproduction

• The roots, stems, and leaves of plants are called vegetative structures.

• When these structures produce a new plant, it is called vegetative reproduction.

Vegetative reproductionVegetative reproduction• Some modified stems of anthophytes, such

as potato tubers, can produce a new plant from each “eye” or bud.

• Using vegetative reproduction to grow numerous plants from one plant is frequently referred to as vegetative propagation.

Vegetative reproductionVegetative reproduction

• Even smaller pieces of plants can be used to grow plants by tissue culture.

• Pieces of plant meristematic tissue are placed on nutrient agar in test tubes or petri dishes.

Vegetative reproductionVegetative reproduction• The plants grown from cuttings and tissue

cultures have the same genetic makeup as the plants from which they came and are botanical clones.

• There is great diversity in the flowers, seeds, fruits, and vegetative structures of anthophytes.

• Anthophytes are divided into families based on these differences.

Protists

Monocots

Dicots

Oak Fagaceae

Magnolia Magnoliaceae

Cactuc Cactaceae

Milkweed Asclepiadaceae

Cocoa Sterculiaceae

Chicory AsteraceaeCaraway

Apiaceae

Coleus Lamiaceae

Raspberry Rosaceae

Lily Liliaceae

Grass Poaceae

Orchid Orchidaceae

Palm Arecaceae

Most anthophytes that produce nectar are pollinated by _______.

Question 1

D. machines

C. water

B. animals

A. wind

The answer is B, animals.

Question 2In anthophytes, _______ is the transfer of immature male gametophytes from the anther to the stigma.

D. vegetative reproduction

C. pollination

B. germinationA. double fertilization

The answer is C, pollination.

Question 3

Why can insects see some flower marking that humans cannot see?

Many of these flower markings are visible only to organisms, like insects, that can detect ultraviolet light. The human eye cannot detect ultraviolet light.

Question 4

What is the difference between the functions of a tube nucleus and a generative nucleus?

Answer

The tube nucleus directs the growth of the pollen tube down through the pistil to the ovary. The generative nucleus divides by mitosis, producing two sperm nuclei.

• The gametophyte generation is dominant in mosses. Archegonia and antheridia form on separate or the same gametophyte. Fertilization requires a film of water on the gametophyte.

Life Cycles of Mosses, Ferns, and Conifers

• Archegonia and antheridia develop on a prothallus, the fern gametophyte. Fertilization requires a film of water on the gametophyte. The sporophyte generation is dominant in ferns.

• Conifers have cones in which a male or female gametophyte forms. Sperm nuclei form in pollen grains and eggs form in ovules. The embryo is protected in a seed.

Life Cycles of Mosses, Ferns, and Conifers

• Flowers are made up of four organs: sepals, petals, stamens, and pistils. A flower lacking any organ is called incomplete. Complete flowers have all four organs.

Flowers and Flowering

• Photoperiodism—responses of flowering plants to daylight-darkness conditions affects flower production. Plants are called short-day, long-day, day-neutral, or intermediate depending upon their photoperiodic response.

• The male gametophyte develops from a microspore in the anther. The female gametophyte develops from a megaspore in the ovule.

The Life Cycle of a Flowering Plant

• Double fertilization occurs when a sperm nucleus joins with an egg to form a zygote. The second sperm nucleus joins the central cell to form endosperm.

• Fruits and seeds are modified for dispersal. Seeds can stay dormant for a long time before they germinate.

The Life Cycle of a Flowering Plant

Question 1

During the life cycle of conifers, microspores develop into _______.

D. pollen grainsC. megaspores

B. micropylesA. archegonia

The answer is D, pollen grains.

Question 2

How is photoperiodism associated with pollination?

Answer

Photoperiodism is a physiological adaptation of all flowering plants that ensure the production of flowers at a time when there is an abundant population of pollinators.

Question 3The process whereby one sperm fertilizes the egg and the other sperm joins with the central cell is called _______.

D. germination

C. double fertilization

B. vegetative reproduction

A. photoperiodism

The answer is C, double fertilization.

Double Fertilization

One sperm fertilizes the central cell (3n)

One sperm fertilizes the egg cell (2n)

Question 4

The _______ is the structure that contains the seed of an anthophyte.

D. egg cellC. ovule

B. stamenA. fruit

The answer is A, fruit.

Question 5Food storage tissue that supports development of the embryo in anthophyte seeds is the _______.

D. ovuleC. endosperm

B. microsporeA. megaspore

The answer is C, microspore.

Question 6

The dormancy period of a seed ends with _______.

D. dispersal

C. pollination

B. germination

A. fertilization

The answer is B, germination.

Question 7The radicle of a plant embryo develops into a _______.

D. rootC. cotyledon

B. pair of leavesA. stem

The answer is D, root.

Question 8

What pushes a seedling upward through the soil when it emerges from its seed?

Answer

This push or force results from water pressure inside the seedling’s cells.

Question 9A flower that naturally has four petals, eight stamens, and one pistil is an example of a (n) _______.

D. male flowerC. monocot

B. incomplete flowerA. dicot

The answer is A, dicot.

Question 10In flowering plants, _______ begins the sporophyte generation.

D. pollinationC. fertilization

B. germinationA. meiosis

The answer is C, fertilization.

Photo CreditsPhoto Credits

• National Cotton Council of America

• PhotoDisc

• Photo Essentials

• Matt Meadows

• Digital Stock

• USDA

• Corbis

• Alton Biggs

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