Chapter 22: Plant Diversity

Comparison of Water and Land as Habitats for Plants

WATER LAND

Water Close to each cell Under land surface, evaporates quickly above surface

Minerals Close to each cell On or under land surface

Gases Dissolved at low concentrations Plentiful in the air

Support Provides buoyancy, support Much less support for parts in air

Light Cuts out some wavelengths and lowers intensity

Much light available

Temperature Little fluctuations, slow change Changes more rapid, wider extremes

Reproduction Motile gametes swim Water seldom available for swimming gametes

Dispersal Water carries offspring to new locations

Water seldom available to carry offspring to new locations

Adaptations of Land Plants to Terrestrial Environments

PROBLEM ADAPTATION

1. Obtaining water and mineral nutrients when they no longer surround entire plant

Rhizoids or roots

2. Transporting water within the plant Xylem

3 Transporting food from sites of manufacture to sites of use Phloem

4. Preventing evaporation from surfaces exposed to air Cuticle

5. Obtaining gases for photosynthesis and respiration Stomata

6. Obtaining sunlight for photosynthesis Leaves

7. Supporting body in medium lacking buoyancy Xylem

8. Coordinating plant growth and plant response to changes in the environment

Hormones

9. Getting gametes to together without reliable supply of water for sperm

Pollen

10. Dispersing new individuals to suitable locations Airborne spores, then seeds

Differences Between Bryophyta and Tracheophyta

BRYOPHYTA TRACHEOPHYTA

1. No vascular tissue Vascular tissue present in sporophytes

2. No true roots, stems, leaves; rootlike rhizoids anchor plant and absorb water

Most modern forms have roots, stems, and leaves in sporophyte generation

3. Not more than a few cm tall Usually more than a few cm high

4. Sporophyte dependent on gametophyte generation

Sporophyte independent, self-sufficient

5. Gametophyte generation dominant Sporophyte generation dominant

6. Gametophyte independent, self-sufficient

Gametophyte independent (“lower” vascular plants) or dependent on sporophyte (gymnosperms and angiosperms

7. Water needed for swimming sperm during sexual reproduction

Water needed for swimming sperm except in angiosperms and higher gymnosperms

8. Lack of vascular tissue restricts to moist envs

Wide range of habitats

A. Metaphyta: Plant Kingdom

1. Bryophyta (Phylum) • Simpler plants; lack vascular system (transport

tubes such as xylem & phloem)• Depend on H2O to a greater extent than

vascular plantsEx: mosses & liverworts

Moss

2. Tracheophyta (Phylum) • Higher plants• 3 main groups possess water vascular system, so LESS

DEPENDENT ON H2O mosses (evolutionary advantage)1. P. Pterophyta (ferns) sperm require water for fertilization2. Gymnosperms/ conifers (cone-bearing) most ancient seed plants - POLLEN TUBE carries sperm- adaptation for terrestrial life3. Angiosperms/ flowering plants POLLEN TUBE carries sperm - Adaptation for terrestrial life/ *life cycle

Tracheids

B. Processes Essential to Sexual Reproduction

1. Meiotic Cell Division reduces species chromosome number by ½ haploid gametes2. Fertilization restores species chromosome number (egg & sperm nuclei fuse- forms zygote)

• Haploid (n) – cell has one member of each pair of chromosomes

• Diploid (2n) – cell has both members of each chromosome pair

C. Reproduction in Mosses & Ferns

1. Alternation of Generations life cycle in which a spore producing plant (sporophyte) alternates with a gamete producing plant (gametophyte)a. Sexual reproduction by a gametophyte alternates with… b. Asexual reproduction by a sporophyte

2. Mosses common moss plant is the gametophyte3. Ferns common fern plant is the sporophyte

NOTE: * Review life cycles handout * Life cycles dependent upon water for fertilization * Habitat restricted/limited by water

Plant Life Cycle• Have 2 alternating phases

known as “Alternation of Generations”1. diploid phase (2N) sporophyte / spore-producing plant2. haploid phase (N) gametophyte/ gamete-producing plant)

Moss Life Cycle

Fern Life CycleProthallus- gametophyte

D. Alternation of Generations (Plant Reproduction)

1. What are the generations?

SPOROPHYTE GAMETOPHYTE

Ferns Leaf-like frond(dominant)

Heart-shaped

Mosses Stalk/capsule Short leafy shoot(dominant)

Flowers Entire plant(dominant)

Pollen grain/ ovule

Cont. Alternation of Generations

2. Which plants have ONLY ONE kind of gametophyte and which plants have TWO KINDS of gametophytes Can you tell why???

• FERNS ONE gametophyte --- Has both antheridia AND archegonia

• MOSS TWO gametophytes --- Antheridia and archegonium on separate leaf-like stalks

• FLOWERS TWO gametophytes --- Microscopic pollen and ovule

Cont. Alternation of Generations

3. What alternates?• Processes Mitosis/ meiosis/ fertilization• Nutrition Dependent (hetertrophic)/

independent (autotrophic)• Chromosome # Diploid/ haploid• Size Dominant (large/ conspicuous)/

not dominant (smaller/ inconspicuous)• Duration Most of life cycle/ short time

period• Sex Asexual (spores)/ sexual (gametes)

4. In plant reproduction, what stage is between the diploid parent plant and the diploid young offspring plant?

• Haploid gametophyte stage5.In plant reproduction, what cell division

process is used to make the gametes?• Mitosis- gametophytes are haploid

SUMMARY OF MAJOR PLANT CHARACTERISTICS (METAPHYTA)(Autotrophic, multicellular, cell wall of cellulose

COMMON NAME PHYLUM NAME VASCULARTISSUE

ORGANS LIFE CYCLE HABITAT

MossesLiverworts

Bryophyta Absent No true roots, stems, leaves

Need water for

Gametophyte dominant, fusion of egg & sperm

fertilization!

Moist areas

Ferns(Felicineae)

Tracheophyta(Pterophyta)

Present/ xylem& phloem

True roots, leaves, develop from rhizome (underground stems) Need water for

Sporophyte dominant, distinct multicellulargametophyte(prothallium)

fertilization!

Moist areas

Conifers(Gymnospermae)- Wind-pollinated

Tracheophyta(Coniferophyta)

Present/ xylem& phloem

True roots, stems, leaves Pollen tube

Sporophyte dominant, seeds & cones

carries sperms

Wide-spread

Flowering Plants(Angiospermae)-Most evolutionary advanced plants- Wind/ animal-pollinated

Tracheophyta(Anthophyta)

Present/ xylem& phloem

True roots, stems, leaves

Pollen tube

Sporophyte dominant,floweres & seeds

carries sperms

Wide-spread