Lab 1

• Green algae/charophytes are considered to be the ancestral source of all plants
• The first land plants likely originated 450-470 million years ago
• Liverworts, mosses and hornworts are sometimes collectively called bryophytes. They are sport bearing, primitive plants that require humid environments
• Lycophytes and monilophytes are both spore bearing and well adapted to human environments
• Vascular tissues are usually xylem and phloem
• Vascular tissue allows:

  • the survival of plants in habitats with less humidity
  • plants to grow taller since water and nutrients can be transported throughout the plant
• Gymnosperms and angiosperms are seed-bearing vascular plants
• The seed is a significant step in evolution of land plants as they protect the embryo and pack. nutrients with the embryo to support the young plant
• Gymnosperms are called "naked seed bearing" because their seeds aren't enclosed in chambers (fruits)
• All conifers are gymnosperms
• Angiosperms have chambers called ovaries where the seed develops
• Angiosperms have been the dominant clade of plants since 100 million years ago
• There are approximately 250 000 angiosperm species
• Phylogenetic tree:

  A) Ancestral green algae (charophytes)

  B) liverworts

  C) mosses

  D) hornworts

  E) non-vascular spore bearing (bryophytes)

  F) lycophytes

  G) monilophytes

  H) seedless vascular

  I) seeded vascular

  J) gymnosperms

  K) angiosperm

  
• alternation of generations is a unique trait of land plants; found in all land plants and some algae
• Most non-vascular plants have a dominant gametophyte
• Most vascular plants have a dominant sporophyte
• Most non-vascular plants and seed bearing plants are heterosporous
• Most seedless vascular plants are homosporous
• • Gametophytes are haploid
  • Gametes are haploid
  • Zygotes are diploid
  • Sporophytes are diploid
  • Spores are haploid
• Alternation of generation:

  A) Gametophyte

  B) mitosis

  C) gametes

  D) fertilization

  E) zygote

  F) mitosis

  G) sporophyte

  H) meiosis

  I) sportes

  J) mitosis

  
• Homosporous plants release one type of spore that becomes a bisexual gametophyte
• Heterosporous plants produce two types of spores that form unisexual gametophytes
• Organisms in the kingdom plantae are eukaryotic and characterized by their ability to perform photosynthesis
• Algae are found in various aquatic environments
• Charophytes have a layer of sporopollenin that prevents the drying of zygotes
• charophytes don't exhibit alternation of generations
• Chlamydomonas sp.

  • small (<25 micrometers), rounded, unicellular algae
• Zygnema sp.

  • multicelular filamentous algae found in shallow water
  • close relative to modern land plants
  • star shaped chloroplast
• Chlamydomonas sp.

  
• Zygnema sp.

  
• Chara sp.

  • multicellular freshwater algae
  • stem-like and leaf-like thallus (undifferentiated tissue) and multicellular rhizoid (affixes the algae to the bottom of the water body)
  • reproduce either vegetatively of sexually, but don't show alternation of generations
  • close relative to modern land plants
• Chara sp.

  
• All non-vascular plants demonstrate alternation of generations

  • gametophyte is dominant
  • sporophyte is reduced and grows on the female gametophyte once the egg is fertilized
• Non vascular plants are hetersporous
• Non vascular plants lack true roots, stems and leaves

  • have root-like rhizoids, stem-like structures, and leaf-like structures
• Since non-vascular plants have no vascular tissue, they are relatively short
• Polytrichum sp. (hair moss)

  • widely distributed moss
  • the gametophyte is the green stem-like and leaf-like structures anchored by rhizoids
  • the sporophyte arises from the femalte gametophyte and is composed of a stalk called the seta, and a capsule where the spores are formed and expelled (when the capsule opens at the operculum)
• Polytrichum sp. (hair moss)

  A) sporophyte (capsule)

  B) sporophyte (seta)

  C) Gametophyte

  
• Seedless vascular plants have well developed leaves, stems, and roots