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All 13 Flashcards — Modes of nutrition
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Question
What two things does a mode of nutrition describe?
Answer
Where an organism gets its **energy** and where it gets its **carbon**.
Question
Define an autotroph.
Answer
An organism that **makes its own organic carbon** from an inorganic source (**CO₂**). 'Auto' = self-feeding.
Question
Define a heterotroph.
Answer
An organism that obtains organic carbon by **taking in organic molecules** made by other organisms. 'Hetero' = feeding on others.
Question
What is a mixotroph?
Answer
An organism that can use **both modes** — making its own food like an autotroph AND taking organic food like a heterotroph (e.g. Euglena).
Question
What carbon source do all autotrophs use?
Answer
**Carbon dioxide (CO₂)** — an inorganic carbon source.
Question
Distinguish a photoautotroph from a chemoautotroph.
Answer
Both fix CO₂, but a **photoautotroph** uses **light** for energy, while a **chemoautotroph** oxidises **inorganic chemicals** (e.g. H₂S).
Question
What is holozoic nutrition?
Answer
Heterotrophic feeding in which food is **ingested and digested INTERNALLY** inside the body (most animals).
Question
What is a saprotroph?
Answer
A heterotroph that feeds on **dead** organic matter, digesting it **EXTERNALLY** with secreted enzymes and absorbing the products (decomposers).
Question
What is a parasite (as a mode of nutrition)?
Answer
A heterotroph that feeds on a **living host** and **harms** it (e.g. a tapeworm, a head louse).
Question
How do you tell a saprotroph from a holozoic feeder?
Answer
Saprotroph digests **externally** and feeds on **dead** matter; a holozoic feeder ingests food and digests it **internally**.
Question
Give an example of a chemoautotroph.
Answer
Some bacteria around **deep-sea vents** that oxidise chemicals such as hydrogen sulfide for energy.
Question
How does oxygen requirement relate to nutrition?
Answer
It is part of the niche: an **obligate aerobe** needs O₂, an **obligate anaerobe** is poisoned by it, a **facultative anaerobe** can use it or do without.
Question
How do you classify a mode of nutrition from a data row?
Answer
Read the **energy source AND carbon source together** — e.g. light + CO₂ = photoautotroph; oxidising chemicals + CO₂ = chemoautotroph.
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Topic 2.10 hub
Ecological niches
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