Download AP Biology, Chapter 38 Angiosperm Reproduction and

AP Biology, Chapter 38
Angiosperm Reproduction and Biotechnology
Flowers of Deceit
38.1 Flowers, double fertilization, and fruits are unique features of the angiosperm life cycle
Intro
1. Outline the angiosperm life cycle.
Dominant diploid sorophyte
Meiosis yields haploid microspores and megaspores
Microspores  male gametophyte  sperm
Megaspores  female gametophyte  egg
Sperm + egg  zygote  diploid sporophyte
Flower Structure and Function
Intro
2. Describe the functions of sepals, petals, stamens, and carpels.
Sepals: green modified leaves surrounding and protecting the petals
Petals: colored modified leaves in animals-pollinated flowers
Stamens: male reproductive organs, produce pollen
Carpels: female reproductive organs, produce ovules
3. Distinguish between: a) complete and incomplete flowers, b) bisexual and
unisexual flowers, and c) monoecious and dioecious plant species.
Complete and incomplete
Complete have sepals, petals, stamens, carpals
Incomplete don't
Bisexual vs. unisexual
Bisexual = perfect = having stamens and carpals
Unisexual have either stamens or carpals
Monoecious and dioecious
Monoecious have both male and female on the same plant
Dioecious have separate male and female plants
4. Explain by which generation, structures, and processes gametes are produced.
Female
One megaspore divides 3 times by mitosis
 one egg + 2 polar nuclei + 5 other
Male
Each microspore divides once by mitosis
 one tube nucleus + one generative nucleus
Generative nucleus divides again by mitosis giving 2 sperm
Development of Male Gametophytes in Pollen Grains
Development of Female Gametophytes (Embryo Sacs)
Pollination
5. Explain how pollen can be transferred between flowers.
Grasses and most trees: by wind, large amounts of pollen
Animal-pollinated make less pollen
Coevolution of Flower and Pollinator
Double Fertilization
6. Describe the sequence of events that lead from pollination to fruit formation.
Pollen on the stigma sends pollen tube down the style
Enters the ovary and grows through the micropyle
One sperm + egg  zygote
One sperm + polar nuclei  3n  endosperm
Ovule  seed; ovary wall  fruit
7. Outline the process of double fertilization and describe the function of endosperm.
Process
One sperm + egg  zygote
One sperm + polar nuclei  3n nucleus
3n nucleus divides to form a multinucleate cell = endosperm
Nourishes the embryo
Stores nutrients for the seedling
In dicots, transfers nutrients to the cotyledons
8. Explain the adaptive advantage of double fertilization in angiosperms.
No food stored unless fertilization occurs
Saves energy and resources
Seed Development, Form and Function
Intro
Endosperm Development
Embryo Development
9. Describe the development of a plant embryo from the first mitotic division to
the embryonic plant with rudimentary organs.
Zygote  terminal cell + basal cell
Terminal cell  proembryo
Basal cell  suspensor
Proembryo
Forms two lobes in dicots, the cotyledons
Apical shoot meristem forms between the cotyledons
Apical root meristem forms where the embryo meets the
suspensor
Structure of the Mature Seed
10. From a diagram, identify the following structures of a seed and recall a
function for each: seed coat, embryo, hypocotyl, radicle, epicotyl, plumule,
endosperm, and cotyledon.
See diagram, 9th edition, page 808
Functions
Seed coat: protects and maintains dormancy
Embryo: the dormant young sporophyte
Hypocotyl: embryonic stem below the cotyledon
Radicle: embryonic root, emerges first during germination
Epicotyl: embryonic stem above the cotyledon
Plumule: embryonic shoot tip and leaves
Endosperm: food storage tissue in monocot seeds
Cotyledon: seed leaves; store food for use by the seedling
Seed Dormancy: An Adaptation for Tough Times
11. Explain how seed dormancy can be advantageous to a plant and describe some
conditions for breaking dormancy.
Dormancy ensures germination at advantageous time/place/conditions
Variation in dormancy breaking
Desert: after enough rain
Crowded undergrowth: after fire
After extended cold: germination in the spring
Seed Germination and Seedling Development
Fruit Form and Function
12. Explain how fruit forms and ripens. List the functions of fruit.
Ovary wall thickens into pericarp
Types
Simple fruits form from one ovary in one flower
Aggregate fruits form from multiple ovaries in one flower
Multiple fruits form from many flowers
Ripening
Senescence of pod  opening
Softening  enzymes digest cell walls
Acids converted into sugars  sweetening
38.2 Flowering plants reproduce sexually, asexually, or both
Intro
Mechanisms of Asexual Reproduction
13. Describe the natural mechanisms of vegetative reproduction in plants, including
fragmentation and apomixis.
Fragmentation
Pieces of leaf, stem, or root may separate and regenerate
Stolons and adventitious roots may become separated fro the parent
Apomixis
= embryo formation from a diploid parent cell in the ovule
Seed contains a clone of the parent
Known to occur in dandlions
Advantages and Disadvantages of Asexual Versus Sexual Reproduction
14. Explain the advantages of using both sexual and asexual reproduction.
Sexual
New combinations of traits for changing environments
Slower and more complicated
Young offspring small and vulnerable
Asexual
Fixed combination of traits for constant environment
Simpler and faster
Offspring less vulnerable since they are mature parts
Mechanisms That Prevent Self-Fertilization
15. Describe mechanisms that prevent self-pollination and explain how this contributes to
genetic variation.
Some self-pollinate, most avoid it
Separate sexes
Different maturation times for stamens and carpals
Physical arrangement of stamens and carpals
Biochemical self-incompatibility
Cross pollination increases combinations of traits
Vegetative Propagation and Agriculture
Intro
16. Describe various methods that horticulturists use to vegetatively propagate
plants from cuttings.
Cuttings
Pieces removed, suitably treated, can give an entire plant
Ex.: potato eyes, African violet leaves, vine sections
Many cultivars are sterile, anyway
Grafting
Piece of one stem inserted into another
Nearly all citrus (scion) are grafted onto lemon roots (stock)
Plant tissue culture: excised cells grown in sterile conditions
Clones from Cuttings
Grafting
Test-Tube Cloning and Related Techniques
17. Explain how the technique of plant tissue culture can be used to clone and
genetically engineer plants.
Entire plants can be grown from single cells
Excised under sterile conditions
Placed in defined growth medium with hormones
Cell  undifferentiated callus  organs
Excised cells may be genetically altered before culturing
18. Describe the process of protoplast fusion and its potential agricultural impact.
Protoplast = plant cell with cell wall removed using enzymes
Protoplasts from different species can be fused
After tissue culture the fused product has a combination of parent traits
38.3 Humans modify crops by breeding and genetic engineering
Intro
Plant Breeding
19. Explain how selective breeding by humans has changed fruits.
Increase size
Increase number of flowers on the plant
Increase sugar content
Plant Biotechnology and Genetic Engineering
Intro
Reducing World Hunger and Malnutrition
Reducing Fossil Fuel Dependency
The Debate over Plant Biotechnology
Intro
20. Summarize the major concerns about the safety of plant biotechnology.
Issues of Human Health
Concern: introduces new allergens like Bt protein
No evidence of adverse effects
Possible Effects on Nontarget Organisms
Pollen from GMO toxic outside of agricultural environment
Addressing the Problem of Transgene Escape
Pesticide-resistance genes may be carried from GMO to weeds