STB 415 – APPLIED ECOLOGY OSUNTECHCOLLEGE 2023/2024 First Semester Examination

ANSWER

Here are the answers to your exam questions in the requested format:

Question 1a:
i. Lichen – Lichens are symbiotic associations between fungi and algae or cyanobacteria. The fungi provide structure and protection, while the algae or cyanobacteria perform photosynthesis, producing food for both organisms.

ii. Lentic water (with examples) – Lentic water refers to still or standing water bodies, such as lakes, ponds, and marshes. These ecosystems support a variety of organisms adapted to low-flow conditions. Example: Lake Victoria.

iii. Lotic water (with example) – Lotic water refers to flowing water systems such as rivers, streams, and brooks. These environments have high oxygen levels due to constant water movement. Example: The Amazon River.

iv. Bacteriophage – A bacteriophage is a virus that infects and replicates within bacteria. It consists of DNA or RNA enclosed within a protein coat and is used in bacterial control and genetic research.

v. Chemoautolithotroph – These are organisms that obtain energy from the oxidation of inorganic substances (e.g., sulfur, iron, or ammonia) and use carbon dioxide as their carbon source. Example: Nitrosomonas, a bacterium that oxidizes ammonia.

Question 1b:
The zones in a marine water habitat include:

  1. Epipelagic Zone (Sunlight Zone) – The uppermost layer where sunlight penetrates, supporting photosynthetic organisms.
  2. Mesopelagic Zone (Twilight Zone) – A region with limited light, home to bioluminescent organisms.
  3. Bathypelagic Zone (Midnight Zone) – No sunlight, with organisms adapted to high pressure and darkness.
  4. Abyssopelagic Zone (Abyssal Zone) – Extremely cold and high-pressure, with deep-sea creatures like anglerfish.
  5. Hadalpelagic Zone (Trench Zone) – The deepest part of the ocean, found in trenches like the Mariana Trench.

Question 2a:
Traits considered when examining colony morphology:

  1. Shape (circular, irregular, filamentous)
  2. Size (small, medium, large)
  3. Color (white, cream, yellow, etc.)
  4. Margin (smooth, undulate, lobate, serrate)
  5. Elevation (flat, raised, convex, umbonate)
  6. Texture (moist, dry, mucoid)
  7. Opacity (transparent, translucent, opaque)

Question 2b:
Units of measurement in bacteriology:

  1. Micrometer (µm) – Measures bacterial cell size.
  2. Nanometer (nm) – Used for viruses and small cellular structures.
  3. Colony-forming unit (CFU) – Estimates viable bacteria in a sample.

Question 2c:
Four basic dyes used in bacteriology:

  1. Crystal violet
  2. Safranin
  3. Methylene blue
  4. Carbol fuchsin

Question 3a:
Microorganisms in the nitrogen cycle:

  1. Nitrogen fixation – Bacteria (e.g., Rhizobium) convert atmospheric nitrogen (N₂) into ammonia (NH₃).
  2. Nitrification – Nitrifying bacteria (Nitrosomonas, Nitrobacter) convert ammonia into nitrites (NO₂⁻) and nitrates (NO₃⁻).
  3. Assimilation – Plants absorb nitrates to synthesize proteins.
  4. Ammonification – Decomposers break down organic nitrogen into ammonia.
  5. Denitrification – Denitrifying bacteria (Pseudomonas) convert nitrates back into nitrogen gas (N₂), releasing it into the atmosphere.

Question 4a:
Roles of marine microbes in the ocean:

  1. Primary producers – Phytoplankton perform photosynthesis, forming the base of the food web.
  2. Nutrient cycling – Bacteria break down organic matter, recycling nutrients.
  3. Bioremediation – Some bacteria degrade pollutants, including oil spills.

Question 4b:
Physical conditions enhancing microbial survival in freshwater:

  1. Temperature – Optimal growth occurs within a specific temperature range.
  2. pH levels – Most microbes prefer neutral pH, though some thrive in acidic or alkaline environments.
  3. Oxygen levels – Aerobic microbes require oxygen, while anaerobes thrive in low-oxygen conditions.
  4. Salinity – Low salinity is ideal for freshwater microbes.
  5. Light availability – Affects photosynthetic microorganisms like cyanobacteria.
  6. Nutrient availability – Organic and inorganic nutrients support microbial growth.
  7. Turbidity – Suspended particles can influence microbial growth and interactions.
  8. Competition and predation – Affects microbial diversity and survival.
  9. Moisture – Essential for microbial metabolic activities.

Question 5a:
(i) Shape of bacteria

  1. Coccus – Spherical-shaped bacteria (e.g., Staphylococcus).
  2. Bacillus – Rod-shaped bacteria (e.g., Escherichia coli).
  3. Spirillum – Spiral-shaped bacteria (e.g., Spirillum volutans).
  4. Vibrio – Comma-shaped bacteria (e.g., Vibrio cholerae).

(ii) Arrangement of bacterial cells

  1. Diplococci – Pairs of cocci (e.g., Neisseria).
  2. Streptococci – Chains of cocci (e.g., Streptococcus).
  3. Staphylococci – Clusters of cocci (e.g., Staphylococcus).
  4. Diplobacilli – Pairs of bacilli (e.g., Moraxella).
  5. Streptobacilli – Chains of bacilli (e.g., Streptobacillus).

Question 5b:
Types of fixation:

  1. Heat fixation – Uses heat to kill bacteria and adhere them to a slide for staining.
  2. Chemical fixation – Uses chemicals (e.g., formaldehyde) to preserve bacterial structures.

 

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