Biology: Micro-Producers, Photosynthetic Protists, and Plant Diversity

Micro-Producers

• Definition: Organisms that create their own food from nonliving environmental materials, primarily through photosynthesis.
• Types:
  • Prokaryotic: Includes prokaryotic producers like cyanobacteria.
  • Eukaryotic: Incorporates eukaryotic producers, such as plants and protists.
• Characteristics of Prokaryotic Producers:
  • Lack a nucleus.
  • Most possess a cell wall.
  • Exhibit a tremendous genetic diversity.

Energy & Carbon Sources in Autotrophs

• Autotrophs are categorized into two major groups based on how they obtain energy and carbon:
  • Photoautotrophs: Use light as an energy source. Examples include:
  • Photosynthetic prokaryotes (e.g., cyanobacteria)
  • Plants
  • Certain protists (e.g., algae)
  • Chemoautotrophs: Use inorganic chemicals as energy sources. Examples include:
  • Certain prokaryotes (e.g., Sulfolobus).
  • Heterotrophs can be classified into:
  • Photoheterotrophs: Use light but require organic compounds.
  • Chemoheterotrophs: Derive energy and carbon from organic compounds. Examples include many prokaryotes, protists, fungi, and animals.

Importance of Cyanobacteria

• Classification: Gram-negative photoautotrophs.
• Functions:
  • Generate oxygen and perform nitrogen fixation.
  • Possess internal membranes (thylakoids) similar to chloroplasts.
• Historical Significance: Known as some of the oldest fossils, dating back over 3.5 billion years, and essential components of marine and freshwater ecosystems.

Types of Photosynthetic Protists

• Eukaryotic Producers: Not classified strictly as plants, animals, or fungi. Usually unicellular and autotrophic. Significant for aquatic food webs.
• Red Algae:
  • Contain phycoerythrin, which gives them a reddish color.
  • Typically multicellular; largest forms are seaweeds.
• Green Algae:
  • Named for their chloroplasts, closely related to plants, which likely evolved from them.

Factors Influencing Protist Biomass

• Declining biomass linked to increasing ocean temperatures.
• Upwelling is crucial for nutrient delivery to phytoplankton, essential for their growth. Warm surface water acts as a barrier to this process.

Ecological Roles of Protists

• Symbionts: Play a role in forming and nourishing coral reefs.
• Producers: Act as pioneers in new environments, aiding in soil development.

Plant Diversity and Adaptation

• Key Traits of Plants:
  • Alternation of Generations: Life cycle alternates between haploid gametophytes and diploid sporophytes.
  • Dependent Embryos: Embryos develop within the female gametophyte.
  • Apical Meristems: Growth regions for roots and shoots.

Bryophytes: Non-Vascular Plants

• Classified as herbaceous (nonwoody) and typically rely on water for fertilization due to flagellated sperm.
• Reproductive Cycle: The female gametophyte retains the diploid embryo, which illustrates the evolution of land plants.
• Ecological Importance: Sphagnum moss (peat moss) forms significant peat deposits, used for fuel and inhibiting decay of organic materials.

Seedless Vascular Plants: Ferns

• First plants able to grow tall; adapted to moist environments due to flagellated sperm.
• Life Cycle: Most are homosporous, producing one type of spore. Some are heterosporous, producing different spores.
• Transport Systems:
  • Xylem: Conducts water and minerals; characterized by lignin-reinforced tracheids.
  • Phloem: Distributes organic compounds, aiding plant growth and structural support.