Chapter 13 Key Concepts

  • All living organisms can be divided among three basic domains, on the basis of DNA sequence relationships.
  • Bacteria occur as single cells and are the most numerous organisms in the sea. They are crucial in decomposition.
  • Bacteria reproduce asexually, but DNA exchange as a form of sexuality is known.
  • Bacteria are capable of gaining energy with many mechanisms of metabolism.
  • Cyanobacteria are photosynthetic cells or chains of cells, but the benthic forms usually live in association with anoxic sediments.
  • The protists and allies include organisms that are at the cellular level of organization only, sometimes with tissues, but may also consist of multicellular forms.
  • Diatoms occur as single cells or chains of cells, are photosynthetic, and have a cell wall that is impregnated with silica.
  • Ubiquitous and usually filamentous groupings of cells, fungi are very important in the decomposition of particulate organic matter.
  • Fungi reproduce by means of fruiting bodies, which form and release spores.
  • Fungi are major sources of damage and occasionally disease to marsh grasses and sea grasses.
  • Fungi live in a mutualistic association with algae to form lichens, which live in a band in the very high intertidal zone.
  • Fungi also live in a mutualistic association with roots of some marsh grasses and sea grasses.
  • Seaweeds are eukaryotic, multicellular, photosynthetic, and usually attached to a substratum. They take up nutrients from the surrounding water and do not have the extensive support structures or other adaptations needed for life in air.
  • A seaweed usually occurs as a thallus, consisting of holdfast, stipe, and blade.
  • Seaweeds are classified by the different pigments used in gathering light for photosynthesis, by their storage products, and by the types of flagellae in their spores.
  • Seaweeds depend on light for photosynthesis and can adjust to the decrease in light with the increase in depth.
  • Seaweeds have a complex life cycle, with differently shaped thallus stages alternating with dispersing stages.
  • Why do seaweeds have complex life cycles in the first place? It may have to do with alternative performance in differing microenvironments.
  • Sea grasses are true flowering plants. The flowers are simplified, however, and the pollen is transported by water.
  • Sea grasses reproduce by asexual growth, via a subsurface rhizome system.
Back to top