Biology : Taxonomy Part-I

Total Questions: 50

1. Biologists have so far known, found and identified a large number of species in the plant and animal kingdom. In terms of numbers, the largest found and identified so far is from among the — [I.A.S. (Pre) 1996]

(a) Fungi
(b) Plants
(c) Insects
(d) Bacteria

Correct Answer: (c) Insects

Solution:All insects belong to the group 'Insecta' which is a class of phylum Arthropoda. Class Insects represents the largest number of world species. Over 1.5 million living animal species have been described - of which more than 1 million are insects.

2. Who discovered bacteria? [56th to 59th B.P.S.C. (Pre) 2015]

(a) Fleming
(b) Lamble
(c) Temin
(d) Leeuwenhoek

Correct Answer: (d) Leeuwenhoek

Solution:Antony Van Leeuwenhoek is regarded as the father of microbiology. He is known for the discovery of bacteria. He was born on October 24, 1632 in Delft, Netherlands.

In the late 17th century, Leeuwenhoek began observing microorganisms in various samples, including pond water, his own saliva, and other substances. He meticulously described the shapes, sizes, and movements of these tiny organisms, which he initially called "animalcules".

His meticulous observations and descriptions laid the foundation for the field of microbiology, which is the study of microorganisms. Leeuwenhoek was not only a keen observer but also a skilled craftsman, building microscopes that were significantly more powerful than those available at the time.

3. Bacteria can be seen by: [U.P.P.C.S. (Pre) 1995]

(a) Naked eye
(b) Compound microscope
(c) Hand lens
(d) None of the above

Correct Answer: (b) Compound microscope

Solution:Bacteria are microscopic living organisms. Most of the bacteria are just 0.5 to 5.0 micron (µm) in size but some of them are about 0.5 mm or more in size. Some of the microscopic organisms can be seen by a compound microscope as it can magnify an object up to 1500-2000 times.

4. Assertion (A): Some bacteria can synthesize their own food. [U.P.P.C.S. (Pre) 2000]

Reason (R): These bacteria have green matter called chloroplasts.

(a) Both (A) and (R) are true, and (R) is the correct explanation of (A).
(b) Both (A) and (R) are true, but (R) is not the correct explanation of (A).
(c) (A) is true, but (R) is false.
(d) (A) is false, but (R) is true.

Correct Answer: (c) (A) is true, but (R) is false.

Solution:Bacteria have a wide range of diets. Some are heterotrophs and others are autotrophs. Most heterotrophic bacteria are saprobes (they absorb dead organic material like rotting flesh). Some of these parasitic bacteria kill their host while others help their host. Autotrophic bacteria make their own food, either by photosynthesis (which uses sunlight, carbon dioxide, and water to make food) or by chemosynthesis (which uses carbon dioxide, methane, and chemicals like ammonia, hydrogen sulphide to make food). Phototrophic bacteria do not have chloroplast. Bacteriochlorophylls are photosynthetic pigments that occur in various phototrophic bacteria.

5. Which of the following statement about bacteria is correct: [U.P.P.C.S. (Pre) 1995]

(a) They are on the borderline of living and non-living
(b) They are on the borderline of plants and animals
(c) They are on the borderline of flowering and non-flowering plants
(d) None of the above

Correct Answer: (d) None of the above

Solution:Bacteria are single-celled microbes. They are unicellular organisms consisting of prokaryotic cells. Their cell structure is simpler than that of other organisms as there is no nucleus or membrane-bound organelles. Bacteria are universal, can be found everywhere. There are some harmful bacteria that can cause illness and disease. There are other bacteria that are essential for us to survive. Bacteria in the digestive system also supply needed vitamins like biotin and vitamin K and are our primary source for some of these nutrients.

6. Which one of the following is responsible for differentiation between Gram-positive and Gram-negative bacteria? [Jharkhand P.C.S. (Pre) 2013]

(a) Cell membrane
(b) Cell wall
(c) Ribosome
(d) None of the above

Correct Answer: (b) Cell wall

Solution:There are two different types of cell wall in bacteria, called Gram-positive and Gram-negative. The names originate from the reaction of cells to the Gram stain, a test long-employed for the classification of bacterial species. Gram-positive bacteria possess a thick cell wall containing many layers of peptidoglycan and teichoic acids. In contrast, Gram-negative bacteria have a relatively thin cell wall consisting of a few layers of peptidoglycan surrounded by a second lipid membrane containing lipopolysaccharides and lipoproteins.

7. The smallest organism, capable of autonomous growth and reproduction, is: [56th to 59th B.P.S.C. (Pre) 2015]

(a) Virus
(b) Bacteria
(c) Mycoplasma
(d) Bacteriophage

Correct Answer: (c) Mycoplasma

Solution:Mycoplasma is the smallest known organism, capable of autonomous growth and reproduction. Mycoplasmas are incredibly tiny, with diameters ranging from 0.2 to 0.3 microns (0.2 to 0.3 micrometers), making them one of the smallest free-living organisms. They have the ability to grow and reproduce independently, meaning they don't require a host cell to survive and replicate, unlike some other microorganisms like viruses. Mycoplasmas lack a rigid cell wall, which distinguishes them from other bacteria and places them in a separate class called Mollicutes. This lack of a cell wall makes them sensitive to osmotic changes and some antibiotics.

They have a relatively simple cell structure, including a plasma membrane, ribosomes, and a small genome, consisting of a double-stranded circular DNA molecule. While small, Mycoplasmas can be pathogenic, causing infections in various animals, including humans. They are found in a wide variety of environments, including humans, animals, plants, and even some marine environments.

8. Assertion (A): Amoeba reproduces by fission. [I.A.S. (Pre) 2005]

Reason (R): All unicellular organisms reproduce by asexual methods.

(a) (A) and (R) both correct, and (R) is the correct explanation of (A).
(b) (A) and (R) both correct, but (R) is not the correct explanation of (A).
(c) (A) is correct, (R) is wrong.
(d) (A) is wrong, (R) is correct.

Correct Answer: (a) (A) and (R) both correct, and (R) is the correct explanation of (A).

Solution:Amoeba is an unicellular organism which has the ability to alter its shape, primarily by extending and retracting pseudopods. Amoeba reproduces by fission. Binary fission is a type of asexual reproduction practiced by unicellular organisms in which the parent cell divides into two daughter cells.
Generally unicellular organisms reproduce by asexual methods only, while some unicellular eukaryotes (like Paramecium) are capable of both asexual and sexual reproduction.

9. Consider the following: [I.A.S. (Pre) 2021]

1.Bacteria

2. Fungi

3. Virus

Which of the above can be cultured in artificial/synthetic medium?

(a) 1 and 2 only
(b) 2 and 3 only
(c) 1 and 3 only
(d) 1, 2 and 3

Correct Answer: (a) 1 and 2 only

Solution:Bacteria and fungi can be cultured in artificial/synthetic medium. Many of them can be grown on nutritive media (e.g., nutrient agar, dextrose agar) to form colonies that can be seen with naked eyes. Viruses require a living host cell for replication. They cannot be cultured in artificial/synthetic medium due to lack of metabolic machinery of their own. Viruses can be grown in vivo (within a whole living organism, plant, or animal) or in vitro (outside a living organism in cells in an artificial environment). Infected host cells (eukaryotic or prokaryotic) can be cultured and grown, and then the growth medium can be harvested as a source of virus.

10. Warm-blooded animals are those which are able to keep their body temperature — [R.A.S./R.T.S. (Pre) 1996]

(a) Lower than environment
(b) Higher than environment
(c) Constant temp. all time
(d) Equal to the atmospheric temp.

Correct Answer: (c) Constant temp. all time

Solution:Warm-blooded creatures like mammals and birds are able to keep their bodies at a constant temperature. They do this by generating their own heat when they are in a cooler environment and by cooling themselves in a hotter environment. This process of maintaining a consistent environment inside the body is called homeostasis.

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