Download Distinguish between the four main groups of land plants

AP Biology, Chapter 29
Plant Diversity I: The Colonization of Land
SUMMARY
INTRODUCTION
AN OVERVIEW OF PLANT EVOLUTION
Structural, chemical, and reproductive adaptations enabled plants to colonize land
1. Summarize the terrestrial adaptations of plants.
a. Apical meristems for longitudinal growth of subterranean and aerial organs
b. Embryophytes: multicellular, dependent embryos retained by the female
c. Alternation of generations with a dormant, resistant spore stage
d. Waxy cuticle and gas exchange through stomata for water conservation
e. Xylem and phloem for distribution of water+mineral and organic products
f. Secondary biosynthetic products: tannins, lignins, sporopollenin
2. Define and distinguish between the stages of the alternation of generations
reproductive cycle. Compare the life cycle of humans with alternation of generations.
a. Stages
i. Sporophyte: multicelluar diploid that performs meiosis
ii. Haploid spores grow by mitosis into gametophyte
iii. Gametophyte makes gametes
iv. Gametes fuse to form diploid zygote
v. Zygote divides by mitosis to form sporophyte
b. Human haploids do not grow by mitosis into a multicellular organism
The history of terrestrial adaptation is the key to modern plant diversity
3. Describe the four great evolutionary episodes in the history of land plants.
a. Ordovician, 475 mya
i. Charophytes  land plants
ii. Sporopollenin, jacketed gametangia, vascular tissue
b. Early Devonian, 400 mya
i.  ferns
ii. Seedless vascular plants
c. Late Devonian, 360 mya
i.  gymnosperms
ii. Seeds
d. Cretaceous, 130 mya
i.  angiosperms
ii. Seeds protected in ovaries
4. Distinguish between the four main groups of land plants.
a. Bryophytes
i. Mosses and liverworts
ii. Seedless and avascular with primitive tissues
b. Pteridophytes
i. Ferns, lycophytes, horsetails
ii. Seedless with an independent gametophyte
c. Gymnosperms
i. Conifers, ginkgoes, cycads
ii. Cone-bearing, seeds not enclosed in a flower or fruit
d. Angiosperms
i. Flowering plants
ii. Seeds enclosed in fruit
THE ORIGIN OF PLANTS
Plants probably evolved from green algae called charophytes
5. Describe five shared derived homologies that link charophyceans and land plants.
a. Homologous chloroplasts: pigments, stacked thylakoids, DNA sequence, # of
membranes
b. Biochemical similarity: cell wall composition, peroxisomal enzymes
c. Mitosis and cytokinesis
i. Nuclear membrane disassembly
ii. Spindle persists until cytokinesis
iii. Cell plate for cytokinesis in some charophytes
d. Similar sperm ultrastructure
e. Genetic relationship: nuclear and rRNA sequences
Alternation of generations in plants may have originated by delayed meiosis
6. Describe a likely hypothesis for the origin of alternation of generations in plants.
a. No multicellular alternation of generations in modern charophytes
i. Multicellular form is haploid
ii. Fertilization takes place on the haploid
iii. Meiosis immediately follows
b. Hypothesis
i. Zygote divides by mitosis before meiosis
ii. Advantage: more cells available for meiosis
Adaptations to shallow water preadapted plants for living on land
7. Explain how adaptations of charophycean algae to shallow water preadapted plants for
life on land.
a. Sporopollenin protects spores
b. Protective sheath on oogonium
8. Distinguish between the kingdoms Plantae, Streptophyta, and Viridiplantae. Note
which of these is used in the textbook. [6th edition]
a. Plantae: land plants; embryophytes (used in the 6th edition)
b. Streptophyta: embryophytes + charophyta
c. Viridiplantae: embryophytes + charophyta + chlorophyta
BRYOPHYTES
The embryophyte adaptation evolved in bryophytes
9. List and distinguish between the three phyla of bryophytes. Briefly describe the
members of each group, note their common names, and indicate which phylum
represented the earliest plants.
a. Bryophyta
i. Feathery with thin sporophyte stalks topped with sporangium
ii. Commonly called mosses (ex. "peat")
b. Hepatophyta
i. Lobed with gemmae cups for asexual reproduction
ii. Commonly called liverworts
c. Anthocerophyta
i. Sporophytes horn or spike-shaped
ii. Commonly called hornworts (ex. Sphagnum)
iii. These are most closely related to fully vascular plants
The gametophyte is the dominant generation in the life cycle of bryophytes
10. Describe the structure of the sporophyte and gametophyte stages of bryophytes.
Explain why most bryophytes grow close to the ground.
a. Sporophyte
i. Thin stalk or spike tipped with sporangium
ii. Grow up out of the archegonium after fertilization
b. Gametophyte
i. Dominant form
ii. Green with small leaflike, stemlike, and rootlike (rhizoids) parts
iii. Lacks well-developed vascular tissue and supporting tissue
iv. Can't transport water very far
12. On a diagram the life cycle of a bryophyte, label the gametophyte and sporophyte
stages and the locations of gamete production, fertilization, and spore production.
a. See 5th edition, page 553
The three divisions of bryophytes are mosses, liverworts, and hornworts
13. Describe the ecological and economic benefits of bryophytes.
a. Form habitats of tiny animals
b. Pioneer species; helps soil formation
c. Store carbon
d. Mined for fuel and for use as a soil amendment
THE ORIGIN OF VASCULAR PLANTS
Introduction
Additional terrestrial adaptations evolved as vascular plants descended from
bryophyte-like ancestors
14. Describe the adaptations of vascular plants, including modifications of the life cycle
and modifications of the sporophyte, that have contributed to their success on land.
a. Dominant sporophyte generation
b. Modifications
i. Branched sporophyte for producing more spores
ii. Vascular tissue with chains of cells including xylem with lignified walls
The branched sporophytes of vascular plants amplified the production of spores and
made more complex bodies possible
SEEDLESS VASCULAR PLANTS
Introduction
A sporophyte-dominant life cycle evolved in seedless vascular plants
15. Distinguish between homosporous and heterosporous conditions.
a. Homosporous: one type of spore, bisexual gametophyte (ex. ferns)
b. Heterosporous: micro- (male) and mega- (female); separate gametophytes
16. Explain why seedless vascular plants are most commonly found in damp habitats.
a. Swimming sperm
b. Fragile gametophytes
The three divisions of seedless vascular plants are lycophytes, horsetails, and ferns
17. Compare the structures of lycophytes, pteridophytes, and sphenophytes.
a. Lycophytes
i. Large (40 m) woody trees in the fossil record
ii. Currently prostrate hebaceous vines and epiphytes
iii. Simple, microphyll leaves; sporangia on stalks
iv. Separate gametophyte; non-photosynthetic; persistent, relies on
mycorrhizae
b. Sphenophytes (horsetails)
i. Once very diverse; fossil forms to 15 m
ii. Reduced to 15 species; now found in swampy areas
ii. Green jointed stems with tiny leaves
iii. Stem tip cones harbor sporangia
c. Pteridophytes
i. Ferns, whisk ferns, and horsetails
ii. Well-developed roots with lignified vascular tissue
iii. Complex megaphyll leaves; sori are clusters of sporangia on leaf
bottoms
18. Describe the production and dispersal of fern spores.
a. Each sorus on the leaf bottom is a cluster of sporangia
b. Springlike devices hurl spores
c. Spores are small enough to be blown by the wind
19. Describe the major life cycle differences between mosses and ferns.
a. Ferns have a separate sporophyte stage
b. Fern sporophyte is larger
c. See fern life cycle, 5th edition, page 556
Seedless vascular plants formed vast "coal forests" during the Carboniferous period
20. Explain how coal is formed and note during which geologic period the most extensive
coal beds were produced.
a. Formation
i. Anoxic swamps limited decay
ii. Dead plants built up and were heated and compressed
b. Geologic period: Carboniferous, 290-360 mya