Characteristics of Unicellular Eukaryotes
- Unicellular eukaryotes
- Primarily aquatic
- Link between plants (Algae), fungi, and animals
- Well defined nucleus & membrane-bound organelle
- Mode of Nutrition – Photosynthetic (holophytic); holozoic
- Euglena – Mixotrophic
- Reproduction
- Asexual or vegetative – Budding, binary fission, multiple fission
- Sexual reproduction by cell fusion
- e.g. conjugation in paramecium
| Characteristics | Diatoms | Dinoflagellates | Euglena | Slime Moulds |
|---|---|---|---|---|
| Division | Chrysophyta | Pyrrhophyta | Euglenophyta | – |
| Producer | Major Chief Producer | 2nd Chief Producer | – | – |
| Characteristics | Pearls of the ocean | Protists with 2 flagella | Do not have cell wall, they have a protein rich layer called pellicle which makes their body flexible | Saprophytic protists |
| Habitat | Freshwater as well as marine | Mainly marine | Majority of them found in fresh water, in stagnant water | The body moves along decaying twigs and leaves engulfing organic material. |
| Mode of Nutrition | Holophytic | Holophytic (producer) | Mixotrophic: Holophytic (photosynthetic) & Heterotrophs (saprobic), they are photosynthetic in the presence of sunlight,(Stigma-Photoreceptive part) when deprived of sunlight they behave like heterotrophs by predating on other smaller organisms. | Saprophytic |
| Cell Wall | Cell wall is made up of cellulose, silica particles are embedded at many places, the cell walls form two thin overlapping shells, which fit together as in a soap box.The walls are embedded with silica and thus the walls are indestructible.Silicated cell wall is called frustule,have Epitheca and Hypotheca | Cell wall has stiff cellulose plates,also have Epitheca and Hypotheca, known as armoured algae | Cell wall absent, pellicle – protein-rich layer | The spores possess true walls, Cellulose in the cell walls of their spores. |
| Ecdysis | Shedding of theca | Shedding of theca | – | – |
| Flagella | They are immobile because flagella are absent, they float passively on the surface of water (plankton) | One flagella is transverse & other is longitudinal, special type of movement (whirling whips) | One large functional flagella, a short and a long one | – |
| Pigments | Chl a, Chl c, Xanthophyll (Fucoxanthin) | Chl a, Chl c, Xanthophyll (Dinoxanthin) | Chl a, Chl b, xanthophyll – pigments identical to higher plants | – |
| Stored Food | Leucosin (chrysolaminarin) & fats (oil) | Starch | – | – |
| Appearance | Golden algae | Yellow-green, brown, blue or red | – | Under suitable conditions, they form an aggregation called plasmodium |
| Special Characters | Oil-filled vacuole | Bioluminescence – Luciferin + O2 —– Luciferase —–> Light + Oxyluciferin, Histone absent in chromosome of dinoflagellates | – | – |
| Reproduction | Binary fission, Reduction in size due to asexual reproduction To restore size, sexual reproduction occurs |
Binary fission, Gonyaulax – Shows rapid multiplication due to which sea appears red. This is called RED TIDE. Blooms of dinoflagellates happen when conditions are right, meaning there are plenty of nutrients | – | During unfavourable conditions, plasmodium forms fruiting bodies which bear spores at their tip |
| Environmental Impact/Special Character/Importance | Diatoms have left behind large amount of cell wall deposits in their habitat; this accumulation over billions of years is referred to as ‘diatomaceous earth’. Being gritty this soil is used in polishing, filtration of oils and syrups. | Toxins released by large numbers can kill marine animals | Photosynthetic in sunlight, heterotrophic in absence of sunlight | Extremely resistant spores survive for many years. The spores are dispersed by air currents. |