Q.Organism having characteristic of both plant and animal are called :
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Euglenoids: The Shape-Shifting Solar-Powered Swimmers
Imagine a tiny, single-celled organism living in a pond. It's a warm, sunny day, and this creature is lazily swimming, using a long whip-like tail called a flagellum. It's green — because inside it, there are chloroplasts, just like in a plant leaf, busily making food from sunlight. It's acting like a plant.
Now imagine the sun goes down, or the pond gets murky. This same creature doesn't starve. It simply stops photosynthesizing, and starts absorbing organic nutrients from the water around it, or even engulfing small particles. It's now acting like an animal.
This is the euglenoid — a living contradiction that refuses to be neatly classified as plant or animal. It's a protist, a member of the kingdom that catches everything that doesn't fit neatly into the other four kingdoms.
The key intuition: Euglenoids are mixotrophic — they can switch between being photosynthetic (like a plant) and heterotrophic (like an animal) depending on the environment. This dual lifestyle is their defining survival trick.
The Precise Statement
Euglenoids are a group of mostly unicellular, flagellated protists, primarily found in freshwater habitats. Their most distinctive features are:
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No Cell Wall: Unlike plants or many other protists, they lack a rigid cell wall. Instead, they have a protein-rich pellicle — a flexible, elastic layer just beneath the cell membrane. This pellicle gives them their remarkable ability to change shape (a movement called metaboly or euglenoid movement), allowing them to squeeze through narrow spaces.
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Mixotrophic Nutrition: They are phototrophic in the presence of light (using chloroplasts with chlorophyll a and b) and saprotrophic or phagotrophic in darkness (absorbing dissolved nutrients or engulfing food particles). This is not a choice they make consciously; it's a metabolic switch triggered by environmental conditions.
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Locomotion: They move primarily using one or two flagella. One flagellum is usually long and emerges from a pocket called the reservoir (or gullet), while the other may be short or non-functional. They also have a stigma (eyespot) — a light-sensitive structure near the reservoir that helps them detect and swim toward optimal light for photosynthesis.
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Storage: They store food as a unique carbohydrate called paramylon, not starch.
Euglenoid Characteristics (Key Exam Points)
Habitat=Freshwater (ponds, ditches)Cell Covering=Protein pellicle (flexible, no cell wall)Nutrition=Mixotrophic (photosynthetic + heterotrophic)Locomotion=Flagella (usually 1–2)Storage=ParamylonExample=Euglena
Why This Matters for Exams …
Some organisms show a mix of plant-like and animal-like features; Euglena is the classic example, being photosynthetic yet motile. …
Euglena shows both plant and animal characters.
Euglena possesses chloroplasts and carries out photosynthesis like a plant, but in the dark it behaves like an animal, moving by a flagellum and taking in food (heterotrophic). Because it blurs the plant-animal boundary it is placed in Protista. …
- CBSE 2023Set ANNUAL1 markQ.Name the protein-rich layer found in Euglenoids.
›Reveal solutionSolution
Euglenoids lack a true cell wall; instead, they have a flexible, protein-rich outer covering called the pellicle.
Euglenoids are discussed under Kingdom Protista in the Biological Classification chapter. Most of them are found in freshwater habitats, and they show characteristics of both plants and animals.
The pellicle: instead of a rigid, non-living cell wall (like in plant cells), euglenoids have a living, protein-rich outer covering called the pellicle, which makes their body form flexible rather than fixed. This flexibility, along with a flagellum used for movement, allows euglenoids to change shape to some extent.
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- CBSE 2023Set ANNUAL1 markQ.What is the connecting link between plants and animals?
›Reveal solutionSolution
Euglena (Euglenoids) is the connecting link between plants and animals, because it combines a plant-like feature (chloroplasts for photosynthesis) with animal-like features (no cell wall, heterotrophic nutrition in the dark, and movement by a flagellum).
Euglena is a unicellular, freshwater organism that does not fit neatly into either the plant or the animal kingdom:
- Plant-like characters: It possesses chloroplasts and carries out photosynthesis (autotrophic nutrition) in the presence of sunlight. …
- CBSE 2023Set ANNUAL1 markMCQQ.Organism having characteristic of both plant and animal are called :(a) Paramecium(b) Euglena(c) Mycoplasma(d) Bacteria
›Reveal solutionSolution
Euglena shows both plant and animal characters.
Euglena possesses chloroplasts and carries out photosynthesis like a plant, but in the dark it behaves like an animal, moving by a flagellum and taking in food (heterotrophic). Because it blurs the plant-animal boundary it is placed in Protista. …
- CBSE 2019Set ANNUAL1 markQ.Write the name of the connecting link between plants and animals.
›Reveal solutionSolution
Euglena, a member of Kingdom Protista (Euglenoids), is considered the connecting link between plants and animals because it has chlorophyll like a plant but an animal-like flexible pellicle and locomotion.
Euglena is a unicellular, fresh-water organism placed under the group Euglenoids in Kingdom Protista. It possesses chloroplasts and carries out photosynthesis in sunlight, a plant-like trait — but in the absence of sunlight it can switch to feeding on smaller organisms (heterotrophic nutrition), an animal-like trait. Instead of a rigid cell wall, it has a protein-rich flexible covering called a pellicle, and it moves actively using flagella, both animal-like feat …
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