1. All single-celled eukaryotic organisms are placed under which kingdom?
Correct Answer: B
Kingdom Protista includes all single-celled eukaryotic organisms. These organisms have a true nucleus and membrane-bound organelles, which distinguish them from prokaryotes. Protists include organisms such as Amoeba, Paramoecium, Chlamydomonas and Euglena. They show great diversity in their structure and mode of nutrition. Some are autotrophic like algae, while others are heterotrophic like protozoans. Most protists live in aquatic environments or moist habitats.
2. Although all single-celled eukaryotes are placed in Kingdom Protista, its boundaries are:
Correct Answer: C
Kingdom Protista includes all unicellular eukaryotic organisms. However, the boundaries of this kingdom are not clearly defined because protists show a wide diversity in structure, nutrition and life cycles. Some protists resemble plants, others resemble animals or fungi. Because of these overlapping characteristics, scientists sometimes find it difficult to clearly separate Protista from other kingdoms. As scientific understanding improves, the classification of protists may continue to change.
3. A photosynthetic protistan may be considered by different biologists as:
Correct Answer: B
Some protists are photosynthetic and resemble plants in their structure and function. Because of this similarity, some biologists may classify them as protists while others may consider them as plants. This shows that the boundaries of Kingdom Protista are not clearly defined. Protists include organisms with characteristics similar to plants, animals and fungi, which makes their classification sometimes difficult.
4. Which of the following groups are included under Kingdom Protista in this book?
Correct Answer: A
In the five-kingdom classification described in this book, Kingdom Protista includes several groups of unicellular eukaryotic organisms such as Chrysophytes, Dinoflagellates, Euglenoids, Slime moulds and Protozoans. These organisms show diverse characteristics and modes of nutrition. Some are photosynthetic like algae, while others are heterotrophic like protozoans. Because of this diversity, Protista forms a very varied group of organisms.
5. Members of Kingdom Protista are primarily:
Correct Answer: B
Most members of Kingdom Protista live in aquatic environments such as ponds, lakes, rivers and oceans. Some protists also live in moist soil or inside the bodies of other organisms. Because they require water for movement, feeding and reproduction, they are mainly found in water or damp habitats.
6. Kingdom Protista forms a link with kingdoms of:
Correct Answer: A
Kingdom Protista includes a wide variety of unicellular eukaryotic organisms. Some protists resemble plants because they are photosynthetic, some resemble animals because they are heterotrophic and capable of movement, and others show characteristics similar to fungi. Because of these similarities, Protista forms a connecting link between the plant, animal and fungal kingdoms in biological classification.
7. Protists are eukaryotic organisms because their cells contain:
Correct Answer: B
Protists are eukaryotic organisms, meaning their cells possess a well-defined nucleus surrounded by a nuclear membrane. In addition, their cells contain membrane-bound organelles such as mitochondria, endoplasmic reticulum and Golgi bodies. These structures help carry out important cellular functions like energy production, protein synthesis and transport of materials within the cell. This distinguishes protists from prokaryotic organisms such as bacteria.
8. Some protists move with the help of:
Correct Answer: B
Many protists are capable of movement and use special structures such as flagella or cilia for locomotion. Flagella are long whip-like structures that help the organism swim through water, while cilia are short hair-like structures that beat rhythmically to move the cell. These structures allow protists to move in aquatic environments in search of food or suitable conditions.
9. Protists reproduce by:
Correct Answer: C
Protists can reproduce both asexually and sexually. Asexual reproduction commonly occurs through methods such as binary fission or multiple fission, where a single cell divides to produce new individuals. Some protists also reproduce sexually through the fusion of gametes or other forms of genetic exchange. This ability to reproduce in different ways helps protists adapt to changing environmental conditions and increases genetic variation within their populations.
10. Protists reproduce sexually by a process involving:
Correct Answer: B
Sexual reproduction in protists involves the fusion of gametes. In this process, two specialized reproductive cells combine to form a zygote. This fusion results in genetic recombination, producing offspring with genetic variation. Sexual reproduction helps protists adapt to changing environmental conditions and increases diversity within their populations.
11. Protists reproduce sexually by a process involving:
Correct Answer: B
Sexual reproduction in protists occurs through a process that involves the fusion of two cells or gametes. When these cells fuse, their genetic material combines and forms a zygote. The zygote later develops into a new organism. This process introduces genetic variation among protists and helps them adapt better to changing environmental conditions.
12. Chrysophytes include which of the following organisms?
Correct Answer: A
Chrysophytes are a group of protists that include diatoms and golden algae, also called desmids. These organisms are mostly aquatic and occur in both freshwater and marine environments. They are microscopic and often float freely in water. Chrysophytes are important primary producers in aquatic ecosystems because many of them carry out photosynthesis and contribute to the food chain in water bodies.
13. Chrysophytes such as diatoms and golden algae are found in:
Correct Answer: C
Chrysophytes include organisms such as diatoms and golden algae (desmids). They are mainly aquatic and occur in a wide range of water bodies. These organisms are found both in freshwater environments like ponds and lakes as well as in marine environments such as seas and oceans. Because they can live in different aquatic habitats, they are widely distributed in nature and play an important role as primary producers in aquatic ecosystems.
14. Chrysophytes are microscopic organisms that float passively in water currents and are called:
Correct Answer: B
Chrysophytes such as diatoms and golden algae are microscopic organisms that live in aquatic environments. They usually float freely in water and move passively with water currents rather than swimming actively. Such organisms are called plankton. Plankton form an important part of aquatic ecosystems because they serve as a major source of food for many aquatic animals and play a key role in the food chain.
15. Aquatic organisms that produce more than 50% of the Earth's oxygen and act as primary producers in the marine food chain include:
Correct Answer: A
Diatoms and green algae are important microscopic photosynthetic organisms found in aquatic environments. They perform photosynthesis and release oxygen into the atmosphere. Scientists estimate that more than 50% of the oxygen present on Earth is produced by these aquatic microorganisms. They also act as primary producers in marine ecosystems because they form the base of the aquatic food chain, providing energy and food for many aquatic organisms such as small fish, zooplankton and other marine animals.
16. Most chrysophytes such as diatoms and golden algae are:
Correct Answer: B
Chrysophytes include diatoms and golden algae (desmids). They are mostly aquatic organisms found in freshwater as well as marine environments. These organisms are microscopic and float passively in water currents as plankton. Most chrysophytes contain photosynthetic pigments and are able to perform photosynthesis, which allows them to produce their own food. Because of this ability, they act as primary producers in aquatic ecosystems and form an important part of the aquatic food chain.
17. In diatoms, the cell wall is composed of two thin overlapping shells that fit together like a:
Correct Answer: A
In diatoms, the cell wall is unique and consists of two thin overlapping halves called valves. These two parts fit together in a way similar to a soap box, where one half slightly overlaps the other. This special structure protects the cell and gives diatoms their characteristic appearance. The cell wall is also embedded with silica, making it hard and resistant. Because of this, the remains of diatoms can accumulate in large quantities in aquatic sediments.
18. The cell walls of diatoms are indestructible because they are embedded with:
Correct Answer: C
The cell walls of diatoms contain silica (silicon dioxide). Because of this silica deposition, their walls become very hard and resistant to decay. Even after the diatoms die, their silica walls remain intact and accumulate at the bottom of water bodies. Over long periods, these deposits form diatomaceous earth, which has many industrial uses such as filtration, polishing and insulation.
19. The accumulation of diatom cell wall deposits over billions of years is called:
Correct Answer: A
Diatoms have cell walls made of silica, which are very hard and resistant to decay. When diatoms die, their silica cell walls settle at the bottom of water bodies such as lakes and oceans. Over millions and billions of years, these deposits accumulate and form a thick layer called diatomaceous earth. This material is widely used in industries for filtration, polishing, insulation and as an abrasive substance.
20. Diatomaceous earth is used mainly for:
Correct Answer: A
Diatomaceous earth is formed from the accumulated silica cell walls of dead diatoms. Because the particles are very fine and gritty, this material has useful industrial properties. It is commonly used as a polishing material and as a filtering agent for substances such as oils, syrups and beverages. Its porous structure helps remove impurities during filtration.
21. Diatoms are the chief ______ in the oceans.
Correct Answer: B
Diatoms are microscopic photosynthetic organisms found abundantly in oceans and other water bodies. They perform photosynthesis using sunlight and produce organic food from carbon dioxide and water. Because they manufacture their own food and form the base of the marine food chain, they are considered the chief producers in oceans. Many aquatic organisms depend directly or indirectly on diatoms for food.
22. Dinoflagellates are mostly:
Correct Answer: B
Dinoflagellates are a group of protists that are mostly found in marine environments. Many of them are photosynthetic and contain pigments that allow them to perform photosynthesis. They are important components of marine plankton and play a significant role as primary producers in ocean ecosystems. Some dinoflagellates can also cause phenomena such as red tides.
23. Dinoflagellates may appear yellow, green, brown, blue or red mainly because of:
Correct Answer: A
Dinoflagellates are mostly marine and photosynthetic organisms. They contain different types of pigments in their cells, such as chlorophyll and other accessory pigments. The presence and combination of these pigments give dinoflagellates various colours such as yellow, green, brown, blue or red. These pigments also help them capture light energy for photosynthesis. Because of their pigmentation and photosynthetic ability, many dinoflagellates act as important primary producers in marine ecosystems.
24. In dinoflagellates, the cell wall contains stiff plates made of:
Correct Answer: A
The cell wall of dinoflagellates is unique because it contains stiff plates made of cellulose on the outer surface. These plates are called theca or thecal plates and they provide protection and structural support to the cell. The presence of these cellulose plates gives dinoflagellates a rigid covering and characteristic appearance. This structure helps them survive in marine environments where many of them exist as part of plankton.
25. In dinoflagellates, the two flagella are arranged as:
Correct Answer: C
Most dinoflagellates possess two flagella that help in their movement. One flagellum lies longitudinally and runs along the length of the organism, while the other lies transversely in a groove or furrow between the cellulose wall plates. The transverse flagellum encircles the body and helps the organism spin as it moves, while the longitudinal flagellum helps propel it forward. This arrangement gives dinoflagellates a characteristic spinning movement in water.
26. Rapid multiplication of red dinoflagellates such as Gonyaulax causes:
Correct Answer: B
Some dinoflagellates, such as Gonyaulax, reproduce very rapidly under favorable environmental conditions. When their population increases enormously, they form dense concentrations in seawater. These organisms contain pigments that give the water a reddish appearance, a phenomenon known as red tide. Red tides may release toxins that can harm marine organisms such as fish and shellfish, and sometimes affect human health as well.
27. Toxins released during red tides can kill marine animals such as:
Correct Answer: B
During red tides, certain dinoflagellates multiply rapidly and release toxic substances into the water. These toxins can harm or even kill many marine organisms. Fish are particularly affected because the toxins interfere with their normal physiological processes. Large fish kills are sometimes observed during severe red tide events. These toxins can also accumulate in shellfish and may become harmful to humans if contaminated seafood is consumed.