1st PUC Biology Question and Answer Chapter 1: The Living World

1^st PUC Biology The Living World Question and Answer:

Question 1.
Why are living organisms Classified?
Answer:
Classifying living organisms is essential for studying them systematically. It helps group organisms based on easily observable characteristics, making it more convenient to understand and research the diversity of life.

Question 2:
Why are the classification systems changing now and then?
Answer:
Classification systems change as new organisms are discovered through ongoing research and technological advancements. To accommodate these new findings, existing classifications must be regularly updated and refined.

Question 3:
What different criteria would you choose to classify people that you meet often?
Answer:
We could classify people based on physical appearance, skin colour, profession, relationship, gender, and geographic location.

Question 4: 
What do we learn from identifying individuals and populations?
Answer:
Identifying individuals and populations provides insights into their lifestyle, geographic location, culture, social and economic status, language, food habits, beliefs, and how they influence others or different populations.

Question 5: 
The scientific name of Mango is given below. Identify the correctly written name:
(a) Mangifera Indica 
(b) *Mangifera Indies*
Answer:
(a) *Mangifera indica* 

(*Note: The genus name is capitalized, while the species name is written in lowercase and italicized.*)

Question 6: 
Define a taxon. Give some examples of taxa at different hierarchical levels.

Answer: 
A *taxon* is a category or rank in the biological classification system used to group organisms based on shared characteristics. Each taxon represents a specific level in the classification hierarchy. Examples of taxa at different hierarchical levels include:

• Kingdom: Animalia
• Phylum: Chordata
• Class: Mammalia
• Order: Carnivora
• Family: Felidae
• Genus: Panthera
• Species: Panthera leo (lion)

Question 7:
Can you identify the correct sequence of taxonomical categories? 

(a) Species → Order → Phylum → Kingdom 
(b) Genus → Species → Order → Kingdom 
(c) Species → Genus → Order → Phylum 

Answer: 
Based on the taxonomical hierarchy,
both (a) and
(c) provide the correct sequences.

Question 8: 
Define and explain the following terms: 

• Phylum
• Class
• Family
• Order
• Genus

Answer: 
(i) Phylum:
Phylum is the classification rank below the kingdom, based on broad structural characteristics of animals or plants. For example, chordates are placed in the phylum Chordata because they possess a notochord and a dorsal hollow nerve cord.

(ii) Class:
Class is the rank that comes after phylum, grouping related orders. It focuses on more specific traits. For instance, the class Mammalia includes the orders Primates (e.g., monkeys, gorillas) and Carnivora (e.g., tigers, cats, dogs), which are all mammals characterized by having mammary glands and hair.

(iii) Family:
Family is a category that groups related genera with fewer similarities than genus and species. It is based on both vegetative and reproductive traits in plants and other significant traits in animals. For example, the genera Solanum, Petunia, and Datura belong to the family Solanaceae. In animals, the genera Panthera and Felis are classified under the family Felidae.

(iv) Order:
Order is a higher rank than family, classified based on a broader set of characteristics. While families and genera focus on specific traits, orders are based on a more general similarity. For example, the animal families Canidae and Felidae are grouped into the order Carnivora, and the plant families Convolvulaceae and Solanaceae are part of the order Polemoniales.

(v) Genus:
The genus is a rank that groups closely related species with several shared characteristics. It is broader than species but more specific than family. For example, the species potato and brinjal belong to the genus Solanum. Similarly, the lion, tiger, and leopard belong to the genus Panthera, while domestic cats belong to a different genus, Felis.

Question 9:
How does a key aid in the identification and classification of an organism?

Answer: 
A key is a tool that helps in identifying and classifying organisms by presenting contrasting pairs of characteristics, known as a couplet. The user chooses between two opposite options, leading to the acceptance of one and the rejection of the other. Each statement in a key is referred to as a lead. Separate taxonomic keys are used for different taxonomic categories such as family, genus, and species, to assist in accurate identification.

Question 10:
Illustrate the taxonomical hierarchy with suitable examples of a plant and an animal.

Answer: 
Plant Example: 

• Plant: Mango
• Kingdom: Plantae
• Phylum: Angiospermae
• Class: Dicotyldonae
• Order: Sapindales
• Family: Anacardiaceae
• Genus: Mangifera
• Species: Indica

Animal Example:

• Animal: Human
• Kingdom: Animalia
• Phylum: Chordata
• Class: Mammalia
• Order: Primates
• Family: Hominidae
• Genus: Homo
• Species: Sapiens

1st PUC Biology The Living World One Mark Questions

Question 1:
Name the basic unit of classification.
Answer: 
The basic unit of classification is *species*.

Question 2:
Define a species.
Answer:
A species is the most fundamental level of classification, consisting of organisms that can interbreed and produce fertile offspring.

Question 3:
Who is considered the father of taxonomy?
Answer:
*Carolus Linnaeus* is regarded as the father of taxonomy.

Question 4: 
What is a taxon?
Answer:
A taxon is any group or category used in classification.

Question 5:
What is the scientific name of coconut?
Answer:
The scientific name of coconut is *Cocos nucifera*.

Question 6: 
What is a key?
Answer:
A key is an analytical tool used for the identification of plants and animals, based on their similarities and differences.

Question 7:
Name the scientific method of naming a species developed by Carolus Linnaeus.
Answer:
The scientific method of naming a species used by Carolus Linnaeus is called *binomial nomenclature*.

Question 8:
Who discovered that viruses are crystallizable?
Answer:
Stanley discovered that viruses are crystallizable.

Question 9:
What is a capsid?
Answer:
The outer protein coat of a virus is called a *capsid*.

Question 10: 
What are DNA viruses and RNA viruses?
Answer:
Viruses that possess DNA as their genetic material are referred to as *DNA viruses*, while those that contain RNA as their genetic material are called *RNA viruses*.

Question 11:
Which virus causes brain fever?
Answer: 
The virus that causes brain fever is the *Japanese Encephalitis virus*.

Question 12:
Mention the Nucleic acid of HIV.
Answer:
The nucleic acid of HIV is *single-stranded RNA*.

Question 13: 
Which is the nucleic acid is found in bacteriophages?
Answer: 
Bacteriophages contain *double-stranded DNA*.

Question 14: 
What are methanogenic bacteria?
Answer:
Methanogenic bacteria are those that produce methane as a metabolic byproduct.

Question 15: 
Give an example of a symbiotic bacteria.
Answer:
An example of a symbiotic bacteria is *Rhizobium leguminosarum*.

Question 16:
What are autotrophs?
Answer: 
Autotrophs are organisms that synthesize their own food using inorganic substances, typically through processes like photosynthesis or chemosynthesis.

Question 17: 
Who discovered bacteria?
Answer: 
*Anton von Leeuwenhoek* is credited with the discovery of bacteria.

Question 18:
Give an example of nitrifying bacteria.
Answer: 
An example of nitrifying bacteria is *Nitrosomonas*.

Question 19:
What are antibiotics?
Answer: 
Antibiotics are chemical substances
produced by microorganisms that inhibit the growth of other microorganisms.

 Question 20: 
Name the bacteria that cause typhoid and tuberculosis.
Answer: 
Typhoid is caused by *Salmonella typhi*, while tuberculosis (TB) is caused by *Mycobacterium tuberculosis*.

Question 21:
What is the characteristic blue pigment of Nostoc?
Answer: 
The characteristic blue pigment of Nostoc is *phycocyanin*.

Question 22: 
What are planktons?
Answer: 
Plankton are microscopic, free-floating organisms in water, which can be either plants (phytoplankton) or animals (zooplankton).

Question 23: 
Why are protists classified as eukaryotes?
Answer: 
Protists are classified as eukaryotes because their cells contain a true nucleus, which is enclosed by a nuclear membrane.

Question 24: 
What is isogamy and anisogamy?
Answer:
Isogamy refers to the fusion of similar gametes, while anisogamy refers to the fusion of dissimilar gametes.

Question 25: 
What is an algal bloom?
Answer: 
An algal bloom is a rapid and excessive growth of algae in a water body, often leading to a dense concentration of algal cells.

Question 26:
What pigment gives diatoms their golden-brown colour?
Answer: 
The pigment that gives diatoms their golden-brown colour is called *diatomin*.

Question 27: 
Which organism is commonly referred to as ‘pond silk’?
Answer: 
The organism commonly known as ‘pond silk’ is *Spirogyra*.

Question 28: 
What are saprobes?
Answer: 
Saprobes are organisms that feed on dead organic matter to obtain their nutrients.

Question 29: 
What is mycelium?
Answer: 
Mycelium is the vegetative part of a fungus, consisting of a network of hyphae.

Question 30: 
What is the first discovered antibiotic?
Answer: 
The first discovered antibiotic is *penicillin*.

Question 31: 
What are hyphae?
Answer: 
Hyphae are long, filamentous structures that can be branched or unbranched and may be septate (having cross-walls) or non-septate (lacking cross-walls). They make up the mycelium of fungi.

Question 32:
What is mycelium?
Answer:
Mycelium is the body of a fungus, consisting of a network of thread-like structures known as hyphae.

Question 33: 
Mention one harmful effect of fungi.
Answer: 
Fungi can cause diseases in various organisms, including plants (e.g., *Koleroga*), animals (e.g., athlete’s foot), and humans (e.g., *Aspergillosis*).

Question 34:
Why are deuteromycetes referred to as ‘imperfect fungi’?
Answer:
Deuteromycetes are called ‘imperfect fungi’ because only their asexual reproductive stages are known, and their sexual reproduction has not been observed.

Question 35: 
What is a slippered animalcule?
Answer:
The term “slippered animalcule” refers to *Paramecium*.

Question 36:  
State the occurrence and function of cilia.
Answer:  
Cilia are found in the phylum Protozoa and serve as locomotor organs, helping organisms move through their environment.

Question 37:  
What are the locomotor organelles of the class Rhizopoda/Sarcodina?
Answer: 
The locomotor organelles of the class Rhizopoda/Sarcodina are *pseudopodia* (false feet).

Question 38: 
Who proposed the five-kingdom classification?
Answer: 
The five-kingdom classification was proposed by *R. H. Whittaker*.

Question 39: 
Who is known as the father of biology?
Answer:  
*Aristotle* is known as the father of biology.

Question 40:  
Differentiate between aplanospores and conidia.
Answer: 
Aplanospores are formed endogenously, within the sporangia, while conidia are formed exogenously, outside the sporangia.

Question 41: 
What are the two kingdoms in the two-kingdom classification?
Answer:  
The two kingdoms in the two-kingdom classification are *Animalia* (animals) and *Plantae* (plants).

Question 42:  
What are the two types of locomotion in Monera?
Answer: 
The two types of locomotion in Monera are *flagella* and *gliding*.

Question 43:  
What do the terms amphitrichous and lophotrichous mean?
Answer: 
    • Amphitrichous: Refers to a cell that has one flagellum at each of its two ends.  

    • Lophotrichous: Refers to a cell that has a tuft of flagella at one or both ends.

Question 44:  
What is phytoplankton?
Answer:  
Phytoplankton are microscopic, autotrophic organisms that float passively on the surface of water.

Question 45:  
In what form is food stored in Euglena?
Answer:  
Food in Euglena is stored in the form of *starch*.

Question 47:
Write the scientific name of a heterothallic fungus.
Answer:
The scientific name of a heterothallic fungus is *Rhizopus stolonifera*.

Question 48:
What is a zygospore?
Answer:
A zygospore is a reproductive structure formed by the fusion of gametes in certain fungi.

Question 49:
What is the method of sexual reproduction in Basidiomycetes?
Answer:
The method of sexual reproduction in Basidiomycetes is called *somatogamy*.

Question 50:
Name the two phases in the life cycle of a plant.
Answer:
The two phases in the life cycle of a plant are the *sporophyte* and the *gametophyte*.

Question 51:
In what form is carbohydrate stored in animal cells?
Answer:
Carbohydrates are stored in animal cells in the form of *glycogen*.

1st PUC Biology The Living World Two Marks

Question 1: 
Write a note on bacteriophages.

Answer: 
Bacteriophages, commonly known as phages, are viruses that specifically infect bacteria. They were discovered by Frederick Twort. Bacteriophages typically have a tadpole shape and contain DNA as their genetic material. They are categorized into two main groups: T-even phages and T-odd phages, based on their structural characteristics and infection mechanisms.

Question 2: 
Write the differences between virus and viroid.

Answer:

1. Structure:

• Virus: Consists of an outer protein coat called a capsid and inner nucleic acid (either DNA or RNA).
• Viroid: Composed solely of RNA without any protein coat.

2. Disease Hosts:

• Virus: Can cause diseases in both animals and plants.
• Viroid: Primarily causes diseases in plants only.

3. Genetic Material:

• Virus: Some viruses contain DNA as their genetic material, while others contain RNA.
• Viroid: Contains only RNA as its genetic material.

Question 3:
What is symbiosis? Give an example of symbiotic bacteria.
Answer:
Symbiosis refers to the mutual relationship between two different organisms, where both benefit from living together. An example of symbiotic bacteria is *Rhizobium*.

Question 4:
Write the names of different shapes of bacteria. (Gulbarga 2005)
Answer:
The different shapes of bacteria are Cocci, Bacilli, and Spirillum.’

Question 23: 
What are the characteristic features of Euglenoids? 

Answer:

• Euglenoids are freshwater organisms typically found in stagnant water.
• Instead of a cell wall, they possess a protein-rich layer called a pellicle, which makes their body flexible.
• They have two flagella: one short and one long.
• While they are photosynthetic in the presence of sunlight, they can act as heterotrophs by preying on smaller organisms when deprived of sunlight.
• The pigments in euglenoids are similar to those found in higher plants.
• Example: *Euglena*.

Question 24.
How are ascomycetes different from Basidiomycetes?

Answer:

 1st PUC Biology The Living World Five Marks Questions

Question 1.
Write a short note on Binomial Nomencia. ture and guidelines for Binomial nomenclature.

Answer:

Binomial Nomenclature was introduced by Carolus Linnaeus. In this system, every organism is given a scientific name consisting of two parts. The first part represents the genus (generic name), and the second part represents the species (specific epithet). For example, in Homo sapiens, “Homo” is the generic name, and “sapiens” is the specific epithet.

Guidelines for Binomial Nomenclature:

1. Scientific names are usually in Latin or derived from Latin, regardless of the organism’s origin.
2. These names are written in italics (or underlined when handwritten).
3. The first part of the name represents the genus, while the second part represents the species.
4. The genus name starts with a capital letter, and the species name begins with a lowercase letter (unless it is derived from a proper noun, in which case it starts with a capital letter).
5. The name of the author who described the species is abbreviated and added after the species name. Example: Homo sapiens

This system ensures uniformity and avoids confusion in naming organisms across the world.

Question 2.
Mention all the Taxonomic aids and briefly describe them.

Answer:

Taxonomic aids are collections or tools that assist in the identification and classification of species. Some important taxonomic aids include:

• Herbarium: A herbarium is a collection of dried, pressed, and preserved plant specimens mounted on sheets. These sheets are organized according to a recognized classification system, serving as a reference for future studies and research.

• Botanical Gardens: These are specialized gardens where living plant species are cultivated for research and reference. Each plant in a botanical garden is labelled with its scientific name and family, aiding in plant identification.

• Museum: Biological museums store preserved specimens of plants and animals, allowing taxonomists to study various species and compare their characteristics.

• Zoological Parks: These parks house wild animals in protected environments under human care. Zoological parks provide an opportunity to observe animals’ food habits and behaviours, contributing to taxonomic knowledge.

• Keys: A key is a tool used to identify plants and animals based on their similarities and differences. It is a step-by-step process that helps narrow down the species by comparing characteristics.

These aids are essential for the proper identification, study, and classification of living organisms.

Question 3.
Describe the steps involved in the classification of an organism.

Answer:

Steps Involved in the Classification of an Organism:

1. The organism is thoroughly examined and described based on its morphological and other characteristics.
2. These characteristics are compared to known organisms to identify similarities or differences with any existing groups or taxa.
3. The organism is then assigned to a known taxon that shares similar characteristics.
4. If the organism exhibits unique traits that are not found in any previously described organisms, it is placed in a new group.
5. A new name is assigned if the organism has not been described before, or its correct scientific name is confirmed.

These steps ensure accurate classification and naming in the biological taxonomy system.

Question 4.
Write short notes on keys.

Answer:
Keys: A key is an analytical tool used to identify plants and animals based on their similarities and differences. It operates through contrasting characters, usually presented in pairs called couplets. Each couplet offers two opposite options, leading to the selection of one, which directs the user to the next step in the identification process. Each choice within the key is known as a lead.

There are two main types of keys:

1. Indented Keys: These present a sequence of choices between two or more statements regarding the characteristics of a species.
2. Bracketed Keys: In these, pairs of opposing characters are used for identification, with numbers on the right of each statement guiding the user to the next choice in the series.

Keys simplify the process of identifying species by narrowing down the options step-by-step.

Question 5.
Write a note on flora, Manuals and Mono-graph.

Answer:
Monographs, Manuals, and Flora:

1. Monographs: A monograph provides a comprehensive account of all available information about a specific family or genus. It compiles detailed data on various aspects of the organisms within that group, offering a thorough resource for taxonomic study.
2. Manuals: Manuals compile information related to a specific region or area. They include keys and descriptions of families, genera, and species, aiding in the identification and classification of organisms within that area.
3. Flora: A flora contains detailed descriptions of the habitat and distribution of plant species in a particular region. Floras are important for documenting plant biodiversity. Examples of floras in India include Flora of British India, Flora of Simensis, and Flora of Delhi.

These resources are essential for studying plant taxonomy, distribution, and identification.

Question 6.
Write the general characters of the kingdom Monera. (8 characters.)

Answer:
General Characteristics of Kingdom Monera:

1. Monerans are prokaryotes, meaning they lack a true nucleus.
2. The nuclear membrane is absent.
3. The cell wall of monerans is composed of murein (peptidoglycan).
4. Cytoplasmic organelles such as mitochondria, Golgi bodies, and endoplasmic reticulum are absent.
5. Ribosomes are of the 70S type.
6. The genetic material consists of double-stranded DNA in the form of a circular loop, called the nucleoid, which is not associated with histone proteins.
7. Photosynthetic monerans have pigments, but the pigments are found inside lamellae, not chloroplasts.
8. The mode of nutrition can be either autotrophic (self-feeding) or heterotrophic (feeding on others). Cell division occurs through binary fission, without mitosis or meiosis.

These characteristics define the basic structure and function of organisms within the Kingdom of Monera.

Question 7.
Write the general characters of the kingdom Mycota. (8 characters).
Answer:

1. They lack chlorophyll and are primarily saprophytes, with some acting as parasites.
2. Mycelium, The fungal body, comprises branched or unbranched filaments known as hyphae.
3. Their cell walls are made of either fungal cellulose or chitin.
4. Fungi can be unicellular or multicellular eukaryotes.
5. They store glycogen and oil as their reserve food materials.
6. They are typically non-motile.
7. Primitive fungi have haploid mycelia, while more advanced groups display dikaryotic mycelia.
8. Reproduction occurs through both asexual and sexual means, with the asexual phase involving spore formation.