IB DP Biology- B4.2 Ecological niches - IB Style Questions For SL Paper 1A -New Syllabus
▶️ Answer/Explanation
An abiotic factor is a non-living component of the environment that influences living organisms. Examples include temperature, salinity, light intensity, and pH.
The salinity surrounding marram grass on a sand dune is a physical, non-living condition, making it an abiotic factor.
In contrast, the other options involve biological interactions, which are biotic factors.
✅ Answer: (C)
▶️ Answer/Explanation
Answer: A. A fungus that digests its food externally and absorbs the products of digestion
Explanation:
A saprotroph is an organism that feeds on dead or decaying organic matter by secreting digestive enzymes externally and then absorbing the nutrients after breakdown. This process is characteristic of fungi, such as molds and mushrooms, which act as decomposers in ecosystems.
Fungi release enzymes onto dead material, digest it outside their bodies, and then absorb the resulting simple nutrients — this external digestion defines saprotrophic nutrition.
Option Evaluation:
A. Correct — Fungi are classic examples of saprotrophs, performing external digestion followed by absorption.
B. Incorrect — The beetle is a detritivore, as it ingests and digests dead material internally.
C. Incorrect — This describes a mixotroph or heterotrophic protist (e.g., Euglena), which uses endocytosis to ingest food, not external digestion.
D. Incorrect — A giraffe is a herbivore that feeds on living plants and digests food internally, not a saprotroph.