Photosynthesis Photosynthetic Organisms 2 — Questions and Answers
Question 1: Which group of bacteria performs oxygenic photosynthesis and is credited with oxygenating Earth's early atmosphere?
- Purple sulfur bacteria
- Cyanobacteria (Correct answer)
- Green sulfur bacteria
- Heliobacteria
Correct answer: Cyanobacteria
Cyanobacteria were the first organisms to perform oxygenic photosynthesis, releasing O2 as a byproduct and transforming Earth's atmosphere.
Question 2: What is the primary photosynthetic pigment in brown algae (phaeophytes)?
- Phycoerythrin
- Fucoxanthin (Correct answer)
- Phycocyanin
- Zeaxanthin
Correct answer: Fucoxanthin
Fucoxanthin is the dominant accessory pigment in brown algae, giving them their characteristic brownish color.
Question 3: Which photosynthetic organisms form symbiotic relationships with fungi to create lichens?
- Mosses and ferns
- Algae or cyanobacteria (Correct answer)
- Purple sulfur bacteria
- Diatoms
Correct answer: Algae or cyanobacteria
Lichens are mutualistic associations where algae or cyanobacteria provide photosynthate to fungi, which provide shelter and moisture.
Question 4: Euglenoids are unique photosynthetic protists because they:
- Lack a nucleus
- Can switch between autotrophy and heterotrophy (Correct answer)
- Only live in saltwater
- Use hydrogen sulfide as an electron donor
Correct answer: Can switch between autotrophy and heterotrophy
Euglena can photosynthesize in light and consume organic matter in darkness, making them mixotrophic organisms.
Question 5: Which terrestrial plants are considered the most evolutionarily primitive photosynthetic land plants?
- Ferns
- Conifers
- Liverworts and mosses (bryophytes) (Correct answer)
- Flowering plants
Correct answer: Liverworts and mosses (bryophytes)
Bryophytes (mosses, liverworts, hornworts) were among the first plants to colonize land and lack vascular tissue.
Question 6: Diatoms are important marine photosynthesizers distinguished by their:
- Spiral chloroplasts
- Silica cell walls called frustules (Correct answer)
- Red pigmentation
- Lack of a nucleus
Correct answer: Silica cell walls called frustules
Diatoms have intricate glass-like cell walls (frustules) made of silica, which preserve well in the fossil record.
Question 7: Which type of plant has evolved to perform CAM photosynthesis as an adaptation to arid environments?
- Ferns
- Mangroves
- Cacti and succulents (Correct answer)
- Water lilies
Correct answer: Cacti and succulents
CAM plants like cacti open stomata at night to fix CO2, minimizing water loss during hot, dry days.
Photosynthesis Photosynthetic Organisms 2
Which group of bacteria performs oxygenic photosynthesis and is credited with oxygenating Earth's early atmosphere?