Plants:  an introduction
  1. Evolution of land plants
    1. first organisms to colonize dry habitats
    2. altered the habitat
    3. advantage: new opportunities
  2. Major steps in evolution of plants
    1. adaptations to drier habitats: stomata, cuticle
      1. characteristics shared between green algae and plants
        1. cellulose cell walls
        2. starch
        3. chlorophylls a and b
      2. example: mosses
    2. becoming terrestrial, step 2
      1. structural adaptations: wood, vascular tissue, roots
      2. example: ferns
    3. Gymnosperms
      1. first true leaves, seeds, pollen
    4. Angiosperms
      1. flowers
  3. Characteristics of main groups of plants
    1. mosses
      1. lack true leaves, extensive vascular tissue
      2. sporophytes dependent upon gametophytes (haploid dominant)
      3. swimming sperm
    2. ferns
      1. true leaves, vascular tissue
      2. sporophytes and gametophytes independent
      3. swimming sperm
    3. Gymnosperms: conifers
      1. gametophytes dependent upon sporophyte: diploid dominant
      2. male gametophyte contained inside pollen
      3. seeds
    4. Angiosperms: flowering splants
      1. flowers
  4. adaptations to extremly dry habitats
    1. different photosynthetic pathways
      1. limiting water loss and photorespiration
Study questions
1.  Create a table of the characteristics of the four main groups of land plants (non-vascular seedless, vascular seedless, gymnosperms, angiosperms) and green algae.  Then see if you can construct a phylogeny "blind" (i.e. without consulting the text book) of these groups, using the green algae as an outgroup.

2.  Discuss the importance for survival on dry land for each of the following characteristics:  cuticle, stomata, pollen, vascular tissue, flowers.  Are they all equally important?

3.  To some extent, evolution of each major innovation for surviving on dry land (cuticle & stomata:  mosses;  vascular tissue:  ferns;  pollen and seeds:  gymnosperms) lead to the replacement of one group by another in the fossil record (i.e., the number of fossils from the more ancient group drops as the number of fossils of the more derived group increases).  In terms of species interactions, what appears to have happened in each case?

4.  Both C4 and CAM photosynthetic pathways result in isolation of gas exchange from the electron cascade and synthesis of glucose.  Both are most common in plants inhabiting dry environments.  Why might this be advantageous in dry environments?

5.  Looking at the life-cycle figures in the text, be sure you understand the cellular processes (fusion, mitosis or meiosis) that is occurring at each step in each life cycle.

see also:  text problems # 4, 5, 6;  concept review #1, applying ideas #2, 3

Answers