1 Review In what kind of environments are green algae found 2 Apply Concepts How is water essential to the life cycle of a bryophyte 3 Review What function do vascular tissues allow Infer The size of plants increase dramatically with the evolution of vascular tissue. How might these two events be related

CH 22 INTRODUCTION TO PLANTS

22.2 Seedless Plants

Green Algae

 “Green algae” are classified with plants  “Algae” applies to any photosynthetic eukaryote other than a land plant  Found in fresh and salt water  Absorb moisture and nutrients directly from their surroundings.

 Switch back and forth between haploid and diploid  Not always with every generation.

Life Cycle of Chlamydomonas

 Haploid and asexual under suitable conditions.

Life Cycle of Chlamydomonas

 Unfavorable conditions uses sexual reproduction  Release gametes that fuse into a diploid zygote (sporophyte) with thick protective wall.

 Zygote begins to grow once conditions become favorable  Divides by meiosis to produce four haploid cells that swim away, mature, and reproduce asexually.

Bryophytes

 Mosses, hornworts, and liverworts  Specialized reproductive organs enclosed by other, non-reproductive cells.

Mosses and Other Bryophytes

 Waxy, protective coating that makes it possible for them to resist drying  Rhizoids  Thin filaments that anchor them to the soil  Absorb water and minerals.

Why Bryophytes Are Small

 Do not make lignin, a substance that hardens cell walls  Do not contain true vascular tissue.

Alternation of Generations

 Gametophyte  Dominant, recognizable stage  Carries out most of the photosynthesis.

 Sporophyte  Dependent on gametophyte for water and nutrients.

 Sperm swim to egg using flagella  Needs water for fertilization.

Gametophyte

 Spore sprouts and grows into gametophyte  Forms rhizoids that grow into ground and shoots that grow into the air.

 Gametes are formed in reproductive structures at the tips of the gametophytes  Archegonia- where eggs are produced  Antheridia- where sperm are produced

 Egg and sperm fuse to form zygote  Zygote marks the beginning of the sporophyte stage.

 Sporophyte grows within the gametophyte, depending on it for water and nutrients.

 Sporophyte grows out of the gametophyte and develops a long stalk ending in a capsule called the sporangium.

 Haploid spores produced in capsule by meiosis  Released when capsule ripens and opens.

Vascular Plants

 Contain vascular tissue (xylem and phloem)  Enables vascular plants to move fluids through their bodies against the force of gravity.

 Xylem  Carries water and minerals up from the roots  Phloem  Carries sugar and carbohydrates from photosynthesis.

Seedless Vascular Plants

 Club mosses, horsetails, and ferns  True vascular tissues  Strong roots  Rhizomes  Large leaves called fronds.

 Spores produced by the sporophyte grow into thin, heart-shaped haploid gametophytes.

 Sperm and eggs are produced in antheridia (sperm) and archegonia (egg)  Fertilization requires water.

 Diploid zygote develops into a new sporophyte plant  Dominant stage  Haploid spores develop on the undersides of the fronds in sporangia.

Keeping Ferns in Check

   Ferns often crowd out tree seedlings blocking efforts to regrow trees after logging. To understand the fern better, scientists measured the number of viable spores per square centimeter of soil at various distances from existing ferns. They counted spores in July as the ferns were just starting to grow and in November after spores had been released.

 Graph the data from the table. Be sure to plot the data from July on one line and November on a second. Be sure the graph is fully labeled and oriented correctly.

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Calculate What percentage of the spores after dispersal are found within 4 meters of the parent plants Interpret Graphs Are spore numbers higher before or after dispersal- Explain Draw Conclusions Would cutting down nearby clusters of ferns prevent ferns from invading patches of the forest that have just been cut for timber- explain your reasoning based on the data