IB DP Biology- A3.1 Diversity of organisms- IB Style Questions For HL Paper 1A -FA 2025
▶️ Answer/Explanation
The three-domain classification system was created using comparisons of ribosomal RNA (rRNA), which revealed major evolutionary differences between groups of organisms.
✅ Answer: (B)
✅ Answer: (B)
Question
How do autotrophs living in an aquatic ecosystem obtain carbon?
A. By diffusion of dissolved carbon dioxide and hydrogen carbonate ions
B. By feeding on heterotrophs and obtaining carbon from carbohydrates
C. By active transport of carbon dioxide directly from the atmosphere
D. By ingesting organisms with carbonate shells
▶️Answer/Explanation
Answer: A
Explanation:
Autotrophs (like algae and cyanobacteria) in aquatic ecosystems obtain carbon in the form of:
- Dissolved carbon dioxide (CO₂)
- Hydrogen carbonate ions (HCO₃⁻)
These forms of carbon are naturally dissolved in water, and autotrophs absorb them by diffusion across their cell membranes. Once inside, the carbon is used in photosynthesis to produce organic molecules like glucose.
Question
The electron micrograph shows the detailed structure of a prokaryotic cell.
How is this cell different from a eukaryotic cell?
A. Eukaryotic cells are compartmentalized, whereas this cell is not.
B. This cell contains ribosomes, whereas eukaryotic cells do not.
C. Eukaryotic cells contain DNA, whereas this cell does not.
D. This cell has a cell wall, whereas eukaryotic cells do not.
▶️Answer/Explanation
Answer: A.
Explanation:
- Prokaryotic cells, like bacteria, lack membrane-bound organelles. That means they do not have compartments such as a nucleus, mitochondria, or endoplasmic reticulum.
- Eukaryotic cells, on the other hand, are compartmentalized — they have internal membranes that divide the cell into different organelles with specialized functions (like the nucleus for DNA storage).
