Ch 21 self review

What are the major microbial communities in marine environment? (marine planktons)

Marine plankton are motile microbial communities that include bacteria, archaea, algae, protozoa, and microscopic fungi. They are categorized by size and type:

• Nanoplankton: Includes smaller algae, flagellated protists, and filamentous cyanobacteria.

• Picoplankton: Consists of bacteria and smaller eukaryotes.

• Femtoplankton (Virioplankton): These are marine viruses, which are the most numerous members of marine ecosystems.

Role of marine phytoplankton in the marine ecosystem?

Marine phytoplankton function as the primary producers at the base of the marine food web. Their major roles include:

• Global Gas Regulation: They produce a substantial portion of the world's oxygen and consume significant amounts of atmospheric $CO_2$ through photosynthesis.

• Nutrient Fixation: Certain members, such as Trichodesmium, are responsible for both carbon dioxide fixation and nitrogen fixation.

• Energy Production: They convert light energy into biomass, providing the fundamental energy source for consumers like zooplankton and fish.

• Carbon Transport: Fragments of decaying phytoplankton sink as "marine snow," which transports organic carbon from the photic zone to the deeper ocean and benthos.

Predominant phytoplankton include cyanobacteria like Prochlorococcus (the ocean's most abundant oxygenic phototroph) and Synechococcus, as well as eukaryotic groups like diatoms and dinoflagellates.

What are the predominant phytoplankton (phototrophs) found in marine ecosystem?

The predominant phytoplankton (phototrophs) in marine ecosystems include both cyanobacteria and eukaryotic groups:

• Cyanobacteria: These include Prochlorococcus (the ocean’s most abundant oxygenic phototroph), Synechococcus (also highly abundant), and Trichodesmium.

• Eukaryotic Phytoplankton: This group consists of diatoms, dinoflagellates, and various other algae.

What is the most abundant microoranisms found in marine ecosystem?

The most abundant microorganisms on Earth are SAR11 (Sargasso Sea).

What is mixotrophy?

Mixotrophy is when an organism both fixes CO2 (autotrophy) and consumes prey (heterotrophy).

What kind of organisms are found at the ocean floor and near to hydrothermal vent?

• Ocean floor: Contains barophiles (pressure-dependent) and psychrophiles.

• Hydrothermal vents: Feature thermophiles and chemolithoautotrophs (sulfur oxidizers, methanogens).

What kind of human pathogens can grow well in marine environment?

• Human pathogens like Vibrio cholerae grow well in marine environments because they are halotolerant.

How is dead zone formed in eutrophic lakes?

• A dead zone is formed in eutrophic lakes when high nutrient levels cause algal blooms; the subsequent decomposition of this organic matter consumes all oxygen, creating an anoxic region.

What are the primary producers and decomposers in soil ecosystem?

• In soil, plants and lithotrophs are primary producers, while bacteria and fungi (like actinomycetes) are the main decomposers.

Differentiate ectomycorrhizae and endomycorrhizae.

• Ectomycorrhizae colonize the external surface of roots.

• Endomycorrhizae have hyphae that penetrate plant cells.

How does mycorrhizae help plant growth?

• They help growth by greatly enhancing the plant's uptake of water and minerals.

Which pathway is more favored in wetland environment? (methanogenesis)

Wetlands favor the methanogenesis pathway (conducted by archaea)

What are endophytes and epiphytes? What is the beneficial role of endophytic or epiphytic microbes to the plant host?

• Endophytes live inside plant tissues, while epiphytes grow on the surface. They benefit hosts by protecting them from pathogens and predators (e.g., producing alkaloids).