Welcome to the one-shot lecture on 'The Living World' for Class 11 Biology. We will cover the entire chapter in this session. Let's start with a thought-provoking question: What is life? Think about what comes to your mind when you hear this question.

There are two ways to approach the definition of life: a religious/spiritual perspective and a scientific perspective. In this lecture, we will focus on the biological definition of life. I encourage you to share your thoughts in the chat.

• ★This is a one-shot lecture on 'The Living World'.0:05
• ★The question posed is: What is life?0:15
• ★We will focus on the scientific definition of life.0:30
• ★Students have 30 seconds to respond in the chat.0:45

Life is defined as a series of chemical reactions involving biomolecules. These biomolecules include proteins, carbohydrates, lipids, enzymes, and nucleic acids. The outcomes of these reactions lead to growth and development.

Reproduction is another key outcome of these chemical reactions. Additionally, consciousness arises from the interactions of these biomolecules. Cellular organization and metabolism are also results of these chemical reactions.

All these characteristics contribute to what we call living organisms. Living organisms can vary in shape and structure based on their cellular composition. For example, tiny organisms with prokaryotic cells can be classified as bacteria.

• ★Life is a series of chemical reactions involving biomolecules.2:06
• ★Biomolecules include proteins, carbohydrates, lipids, enzymes, and nucleic acids.2:10
• ★Key outcomes of chemical reactions include growth, reproduction, and consciousness.2:20
• ★Living organisms vary in shape and structure based on cellular composition.2:30

Example: Bacteria are tiny organisms formed from prokaryotic cells.2:35

Life is defined by chemical reactions among biomolecules. These reactions lead to characteristics such as growth, development, reproduction, consciousness, cellular organization, and metabolism.

Living organisms can be categorized into bacteria, fungi, plants, and animals based on their shape and structure. According to NCERT, there are five main features of life, although there are more.

Features of life can be classified into two categories: fundamental and defining. Fundamental features have exceptions, while defining features do not.

For example, if we say all organisms in kingdom Monera have a cell wall, this is a defining feature because it has no exceptions.

• ★Life is characterized by chemical reactions among biomolecules.5:04
• ★Key features of life include growth, development, and reproduction.5:10
• ★Fundamental features have exceptions; defining features do not.5:20
• ★All organisms in kingdom Monera have a cell wall is a defining feature.5:40

Example: An example of a defining feature is that all organisms in kingdom Monera have a cell wall.5:40

Myoplasma does not have a cell wall. This makes it a fundamental statement. There are no exceptions to this rule.

Plants are generally green, but there are exceptions. Non-green plants can be orange or red. This characteristic is also fundamental due to these exceptions.

Prokaryotic organisms are defined by the absence of a nucleus. This is a defining feature with no exceptions. The term 'prokaryote' specifically refers to organisms lacking a nucleus.

Unicellular prokaryotes belong to the kingdom Monera. This is another defining characteristic. All unicellular eukaryotes are classified as protists, which is also a defining feature.

• ★Myoplasma does not have a cell wall.8:37
• ★Plants are generally green, but exceptions exist.8:50
• ★Prokaryotic organisms lack a nucleus, a defining feature.9:00
• ★Unicellular prokaryotes are classified under kingdom Monera.9:10

Example: All unicellular eukaryotes are classified as protists.10:00

Mammary glands are a defining characteristic of all mammals. Every mammal, including the platypus, possesses mammary glands. Their presence is non-negotiable for classification, regardless of whether they are functional or non-functional.

Growth is defined as an increase in cell number and body mass. This increase is referred to as the twin characters of growth: increase in cell number and increase in body mass.

In unicellular organisms, growth is synonymous with reproduction. Every time a unicellular organism grows, it also reproduces. Thus, growth and reproduction are directly linked in these organisms.

• ★Mammary glands are a defining characteristic of all mammals.10:43
• ★Growth is defined as an increase in cell number and body mass.10:58
• ★In unicellular organisms, growth equals reproduction.11:22

Example: Every unicellular organism grows and reproduces simultaneously.11:22

Extrinsic growth refers to growth occurring from the outside or exterior. An example is the snow layer on mountains in Kashmir during December. This type of growth is primarily associated with non-living things.

Extrinsic growth can also be illustrated through personal examples, such as wearing a jacket. When I wear a jacket, that is also considered extrinsic growth because it happens from the outside.

• ★Extrinsic growth occurs from the outside.13:42
• ★Snow on mountains in Kashmir is an example of extrinsic growth.13:50
• ★Wearing a jacket demonstrates extrinsic growth.14:04
• ★Extrinsic growth is mainly shown by non-living things.14:10

Example: Wearing a jacket is an example of extrinsic growth.14:04

Intrinsic growth means growth from the inside of an organism. Living organisms typically show intrinsic growth. Growth can be classified into two types: intrinsic and extrinsic.

Humans stop vertical growth at certain ages—boys at 21 and girls at 18—but horizontal growth continues. Plants are unique as they can exhibit both vertical and horizontal growth throughout their lifetime. This is called indefinite growth, attributed to meristematic cells, which enable unlimited growth.

• ★Intrinsic growth refers to growth from the inside.15:52
• ★Plants exhibit indefinite growth due to meristematic cells.15:52
• ★Humans have a stop in vertical growth at certain ages.15:52
• ★Definite growth refers to limited growth, unlike plants' unlimited growth.15:52

Example: Humans stop vertical growth at ages 21 for boys and 18 for girls, but plants continue to grow indefinitely.15:52

Growth can be limited or unlimited. There are exceptions where non-living things also show growth. Therefore, growth is placed in the category of fundamental characteristics of living organisms.

Examples of non-living things that show growth include sand dunes and glaciers. This type of growth is classified as extrinsic growth. Now, let's move on to reproduction. Reproduction is the formation of new individuals of similar kinds, following the principle of 'like begets like'. For instance, a dog gives birth to a puppy, and a cat gives birth to a kitten.

• ★Growth can be limited or unlimited, with exceptions.17:52
• ★Growth is categorized as a fundamental characteristic of living organisms.17:52
• ★Reproduction is the formation of new individuals of similar kinds.17:52
• ★'Like begets like' is a key principle in reproduction.17:52

Example: A dog gives birth to a puppy, illustrating 'like begets like'.17:52

An individual can complete its life cycle without reproduction. However, a species cannot survive in the future without reproduction. If everyone stops reproducing, there will be no future generations, as seen in Japan's declining birth rates.

There are two main types of reproduction: asexual and sexual. Asexual reproduction involves a single parent and produces offspring that are identical to the parent. In contrast, sexual reproduction can involve one parent (uniparental) or two parents (biparental). An example of uniparental sexual reproduction is the hibiscus flower.

• ★An individual can complete its life cycle without reproduction.20:06
• ★A species cannot exist in the future without reproduction.20:10
• ★Asexual reproduction involves a single parent.20:15
• ★Uniparental sexual reproduction can occur, e.g., hibiscus flower.20:20

Example: The hibiscus flower is an example of uniparental sexual reproduction.20:25

Fungi reproduce mainly through spore formation, which is their primary method of reproduction. They can also reproduce sexually and asexually.

Yeast reproduces by budding, where one bud can produce another bud. This process continues, allowing for rapid population growth.

Planaria exhibits regeneration, meaning it can regrow lost parts. Algae reproduce through fragmentation, where a part of the organism breaks off and develops into a new individual.

Mosses have a developmental stage known as the protonema stage, which will be discussed in detail in the plant kingdom section.

• ★Fungi reproduce mainly through spore formation.22:24
• ★Yeast reproduces by budding, producing new buds.22:30
• ★Planaria can regenerate lost parts.22:36
• ★Algae reproduce through fragmentation.22:42

Example: In yeast, one bud can produce another bud, leading to rapid population increase.22:30

Infertile couples undergoing IVF represent a case of reproductive intervention. This highlights the complexity of reproduction beyond natural processes.

Mules serve as an example of a hybrid that is typically sterile. This illustrates exceptions in reproduction that challenge traditional definitions of species.

• ★Infertile couples using IVF demonstrate reproductive intervention.24:23
• ★Mules are hybrids that are usually sterile.24:25
• ★Reproductive exceptions challenge traditional definitions of species.24:27
• ★The classification of reproductive exceptions is debated in biology.24:29

Example: Mules, which are hybrids of horses and donkeys, are typically sterile and cannot reproduce.24:25

Metabolism is the sum total of all reactions happening in the body. It can be classified into two main processes: anabolism and catabolism.

Anabolism involves the joining of simple molecules to form complex molecules. For example, photosynthesis is an anabolic process. In contrast, catabolism is the breakdown of complex substances into simpler substances. The key difference is: anabolism is simple to complex, while catabolism is complex to simple.

• ★Metabolism is the sum total of all reactions in the body.26:28
• ★Anabolism: simple molecules join to form complex molecules.26:35
• ★Catabolism: complex substances break down into simple substances.26:43
• ★Anabolism is simple to complex; catabolism is complex to simple.26:50

Example: Photosynthesis is an example of an anabolic process.26:35

Metabolism is not present in non-living things. It is a characteristic exclusive to living organisms. However, metabolic reactions can occur outside living organisms in a controlled environment, like in a test tube. These isolated metabolic reactions are neither living nor non-living, but the reactions themselves are considered living.

Now, let's discuss size. What is smaller, an atom or a cell? An atom is smaller than a cell. When multiple cells are combined, they form tissues or larger structures.

• ★Metabolism is not present in non-living things.28:38
• ★Isolated metabolic reactions in a test tube are neither living nor non-living.28:45
• ★Atoms are smaller than cells.28:55
• ★Combining multiple cells results in tissues or larger structures.29:00

Example: An example of combining cells is the formation of tissues in multicellular organisms.29:05

Cells combine to form tissues. Multiple tissues come together to form organs. When multiple organs are joined, they create organ systems. This hierarchy illustrates cellular organization, which is a characteristic unique to living organisms.

Within a cell, there is also organization and a division of labor. For example, mitochondria are responsible for energy production, while chloroplasts handle pigmentation in plant cells. This internal organization allows cells to function properly.

• ★Cells combine to form tissues.30:37
• ★Tissues combine to form organs.30:45
• ★Organs combine to form organ systems.30:50
• ★Cellular organization is unique to living organisms.31:00

Organisms are defined by their organization and their ability to respond to stimuli. This response is a key feature of consciousness. For example, when a ball is thrown at you, you can either dodge it, catch it, or get hit by it. These reactions are responses to the stimuli presented.

The ability to respond to stimuli is facilitated by sensory organs. These include the eyes, ears, nose, mouth, and skin. Each of these organs detects stimuli and helps the organism react appropriately, often indicating danger or significant events.

• ★Organisms respond to stimuli, showcasing consciousness.32:45
• ★Responses to stimuli can be dodging, catching, or being hit.32:55
• ★Sensory organs include eyes, ears, nose, mouth, and skin.33:10
• ★Responses indicate awareness of danger or significant events.33:25

Consciousness is awareness of the surroundings and the ability to respond to external stimuli. Only living things exhibit consciousness. Inanimate objects, like a phone, do not respond to stimuli in the same way living beings do.

For example, if you hit your sibling, they will likely hit you back almost instantly. This illustrates the concept of responding to stimuli. However, consider a person in a coma. They do not respond to external stimuli, leading to questions about their consciousness. The terms 'defining' and 'fundamental' are discussed in relation to consciousness and unconsciousness.

• ★Consciousness is awareness of surroundings and response to external stimuli.34:52
• ★Only living things exhibit consciousness.34:55
• ★Inanimate objects do not respond to stimuli.34:58
• ★A person in a coma raises questions about consciousness.35:15

Example: If you hit your sibling, they will respond quickly, demonstrating consciousness.35:05

Cellular consciousness refers to a person's responsiveness to medicine even when they are unresponsive externally. This indicates that consciousness can exist at a cellular level, which is termed cellular consciousness.

Self-consciousness is the awareness of one's appearance and social presentation. This trait is primarily observed in humans. Animals do not exhibit self-consciousness regarding their appearance, as they do not care how they look. Humans, however, prepare their appearance for social functions, showcasing their self-consciousness.

• ★Cellular consciousness is responsiveness at a cellular level.37:15
• ★Self-consciousness is unique to humans, reflecting awareness of appearance.37:25
• ★Animals generally do not exhibit self-consciousness about their looks.37:35
• ★Humans prepare their appearance for social functions, indicating self-consciousness.37:45

Example: Humans dress up nicely for functions, showing self-consciousness.37:55

Humans have consciousness, which helps us understand the world. Different languages have unique names for the same organism, causing confusion. For example, the mango is called 'mahinhandu' in Kannada and 'midi pandu' in other languages. This variation led scientists to realize a problem: everyone has their own name for organisms, making identification difficult.

To solve this, scientists created a system of scientific names. Every organism, including plants, animals, and bacteria, has a scientific name. The scientific name for mango is $Mangiferaindica$.

• ★Different languages have unique names for the same organism.39:09
• ★Scientists developed a system of scientific names to avoid confusion.39:19
• ★Every organism has a scientific name, including plants and bacteria.39:27
• ★The scientific name for mango is $Mangiferaindica$.39:35

Example: The mango is known as 'mahinhandu' in Kannada and its scientific name is $Mangiferaindica$.39:25

The scientific name for mango is $Mangiferaindica$. Binomial nomenclature consists of two parts: the genus name and the species name. The prefix 'bi' in binomial means 'two'.

There are other naming systems such as tromial and monomial nomenclature, but they are not part of the syllabus. Binomial nomenclature was proposed by Carl Linnaeus, known as the father of taxonomy, in his book 'Systema Naturae'.

• ★The scientific name for mango is $Mangiferaindica$.41:14
• ★Binomial nomenclature consists of two parts: genus name and species name.41:14
• ★Carl Linnaeus proposed binomial nomenclature in 'Systema Naturae'.41:14
• ★The prefix 'bi' in binomial means 'two'.41:14

Example: Students are encouraged to ask for '1 kg manifa' to illustrate the confusion of common names.41:14

In biological nomenclature, the first word is the genus name, and the second word is the species or specific epithet. For example, in *Mangifera indica*, *Mangifera* is the genus and *indica* is the species.

Scientific names must adhere to specific rules. They are generally in Latin and written in italics. Regardless of the organism's origin, the scientific name cannot be in local languages like Tamil or Hindi.

• ★The first word in a scientific name is the genus name.43:22
• ★The second word in a scientific name is the species or specific epithet.43:25
• ★Biological names are generally in Latin and written in italics.43:30
• ★Scientific names cannot be in local languages.43:35

Example: In the case of the frog found in the Western Ghats, its scientific name must be in Latin, not in local languages.43:45

Biological names must be handwritten with both words separately underlined or printed in italics to indicate their Latin origin. The first word denotes the genus and starts with a capital letter. The specific epithet, or second word, starts with a small letter.

When typing, students should ensure names are Latinized. This means following the capitalization rules: genus with a capital letter and species with a small letter.

• ★Biological names are underlined or italicized to show Latin origin.45:39
• ★The genus name starts with a capital letter; the species name starts with a small letter.45:45
• ★Names should be Latinized when typed.45:55
• ★Content is relevant to NCERT and unit exams.46:05

Example: For example, in the name *Homo sapiens*, 'Homo' is the genus and 'sapiens' is the species.45:50

Taxonomy is the science of classifying organisms. It involves organizing living beings into groups based on their characteristics and utility. Just like organizing clothes in a wardrobe, where you separate pants, shirts, and other items, taxonomy classifies different animals into categories.

The process of classification includes identification, nomenclature, and organization. The first step in taxonomy is called characterization, which helps in understanding the distinct features of organisms.

• ★Taxonomy is the science of classification of organisms.47:41
• ★Classification is similar to organizing clothes in a wardrobe based on utility.47:41
• ★The first step in taxonomy is characterization.47:41
• ★Taxonomy involves identification, nomenclature, and organization.47:41

Example: Organizing clothes in a wardrobe illustrates the concept of classification in taxonomy.47:41

The first step of taxonomy is characterization. In this step, we observe the features of an organism. For example, we note the color and design of a jacket. This jacket is black with bright orange branding, similar to the Swiggy color.

The second step is identification. Here, we determine what type of item we are observing. Is it a pant? No. Is it a shirt? No. Is it a t-shirt? No. It is a jacket. This process helps us identify the organism in biological taxonomy.

• ★Characterization involves observing features of an organism.50:34
• ★Identification determines the type of organism being observed.50:35
• ★Classification groups organisms based on shared characteristics.50:36
• ★Nomenclature is the final step, involving naming the organism.50:37

Example: A black jacket with orange branding illustrates the steps of taxonomy.50:38

Classification organizes living organisms into categories: kingdom, class, order, family, genus, and species. For example, a jacket can be classified and stored in a wardrobe. This process is similar to how we classify animals.

Nomenclature is the naming of organisms based on their classification. In this case, the jacket is humorously named 'Bob'. Taxonomy encompasses observation, identification, classification, and nomenclature.

• ★Classification involves kingdom, class, order, family, genus, and species.52:36
• ★Nomenclature is the naming of organisms based on their classification.52:36
• ★Taxonomy includes observation, identification, classification, and nomenclature.52:36

Example: The jacket is humorously named 'Bob' as an example of nomenclature.52:36

Taxonomy is the science of classification of organisms. It involves organizing living things into categories based on shared characteristics.

Systematics is taxonomy plus the study of evolutionary relationships. It includes identification, description, and explanation of biological diversity, emphasizing evolutionary connections among organisms.

• ★Taxonomy is the science of classification of organisms.54:40
• ★Systematics incorporates evolutionary relationships into taxonomy.54:45
• ★Systematics involves identification, description, and explanation of biological diversity.54:50
• ★Ultimate attention is requested for the next 10 minutes.54:55

Taxonomical hierarchy classifies organisms into ranks or categories. A taxon is a specific rank, such as family, order, or class. Think of it like police ranks: constable, head constable, inspector, and so on. Each rank is a taxon.

The ascending order of taxonomy goes from species to kingdom. This means we move upwards from species to kingdom. The descending order is the reverse, moving from kingdom down to species. More organisms are present at the kingdom level than at the species level.

• ★Taxonomical hierarchy classifies organisms into ranks.56:58
• ★A taxon is a specific rank in taxonomy, like family or order.57:05
• ★Ascending order in taxonomy is from species to kingdom.57:13
• ★More organisms are found at the kingdom level than at the species level.57:25

At the kingdom level, we have more organisms compared to the genus level. General characters are more prevalent at the kingdom level. For example, modes of nutrition and presence of chlorophyll are general characters. As we move down the taxonomic hierarchy, the number of organisms decreases, and there are many exceptions to general characters.

Sponges and humans both belong to the kingdom Animalia. However, sponges and humans do not share similarities despite being in the same kingdom.

• ★More organisms exist at the kingdom level than at the genus level.59:15
• ★General characters are more prevalent at the kingdom level.59:25
• ★Sponges and humans belong to the kingdom Animalia but do not share similarities.60:00

Example: Sponges are different from humans despite both being classified under Animalia.60:05

At the kingdom level, organisms show less similarity. For example, leopards, tigers, elephants, and pandas have minimal similarities. As we move down the taxonomic hierarchy, the similarities among organisms increase significantly.

A species is defined as a group of individual organisms with similarities. For instance, dog breeds like Golden Retrievers, Dobermans, and Labradors share many similarities, illustrating this concept.

• ★Organisms show less similarity at the kingdom level compared to lower taxonomic levels.61:20
• ★As one moves down the taxonomic hierarchy, similarities among organisms increase.61:25
• ★A species is a group of individual organisms with similarities.61:30

Example: Dog breeds such as Golden Retrievers and Labradors illustrate increased similarities within a species.61:35

Multiple species can be grouped together to form a genus. For example, Panthera tigris (tiger) and Panthera leo (lion) share common features that classify them under the genus Panthera.

The term 'genus' represents a higher taxonomic rank than species. When combining species with common characteristics, such as Panthera leo and Panthera tigris, we classify them under the genus Panthera.

• ★Multiple species can be grouped into a genus.63:26
• ★Examples include Panthera tigris (tiger) and Panthera leo (lion).63:35
• ★The genus is a higher taxonomic rank than species.63:45
• ★Panthera is an example of a genus that includes both tigers and lions.63:55

Example: Panthera tigris and Panthera leo are classified under the genus Panthera due to their common features.64:05

Joining similar genera results in the formation of a family. For example, the cat family includes the genera Panthera (big cats) and Felis (small cats). When these two genera combine, they create the cat family.

When two different families are combined, such as the cat family and the dog family, they form an order. Cats and dogs belong to the order Carnivora.

• ★Joining similar genera forms a family.65:36
• ★Example of family: cat family includes Panthera and Felis.65:45
• ★Combining different families results in an order.66:00
• ★Cats and dogs belong to the order Carnivora.66:15

Example: The cat family includes genera like Panthera and Felis.65:50

The order Carnivora includes families such as Felidae (cats) and Canidae (dogs). Species make up the genus, and genera make up the family in biological classification.

When two different orders, for example, Primata and Carnivora, are combined, they form a class called Mammalia. Several classes together make up a phylum in the biological classification hierarchy.

• ★The order Carnivora consists of families like Felidae and Canidae.68:21
• ★Combining two orders forms a class, specifically Mammalia from Primata and Carnivora.68:21
• ★Several classes together make up a phylum in biological classification.68:21
• ★In plants, the term 'division' is used instead of 'phylum'.68:21

Example: Combining the orders Primata and Carnivora results in the class Mammalia.68:21

The five kingdom classification includes Monera, Protista, Fungi, Plantae, and Animalia. Humans belong to the kingdom Animalia, phylum Chordata, subphylum Vertebrata, and class Mammalia.

Taxonomical categories are structured as follows: kingdom, phylum, subphylum, class, order, family, genus, and species. The scientific name for humans is $Homosapiens$. Students must memorize the table of common names and their scientific names.

• ★The five kingdoms are Monera, Protista, Fungi, Plantae, and Animalia.70:28
• ★Humans are classified as $Homosapiens$ in the kingdom Animalia.70:28
• ★Taxonomical categories include kingdom, phylum, subphylum, class, order, family, genus, and species.70:28
• ★An example of a scientific name is $Muscadomestica$ for housefly.70:28

Example: The scientific name for housefly is $Muscadomestica$.70:28

ICBN stands for International Code for Botanical Nomenclature. It provides the rules for naming plants. Similarly, ICZN stands for International Code for Zoological Nomenclature, which governs the naming of animals.

Binomial nomenclature consists of two components: the generic name (X) and the specific name (Y). This naming system was proposed by Carl Linnaeus. The taxonomic hierarchy includes categories such as kingdom, phylum, class, order, family, genus, and species.

• ★ICBN is the International Code for Botanical Nomenclature.73:05
• ★ICZN is the International Code for Zoological Nomenclature.73:10
• ★Binomial nomenclature has two components: generic name (X) and specific name (Y).73:20
• ★Taxonomic hierarchy includes kingdom, phylum, class, order, family, genus, and species.73:30

Example: The housefly is an example of an organism that falls under binomial nomenclature.73:35

Biological nomenclature follows universal rules. The first word in a biological name represents the genus, while the second word is the specific epithet. These names are derived from Latin. When handwritten, scientific names should be underlined.

A matching exercise is introduced to identify taxonomic categories: family, order, class, and phylum. Phylum is a higher taxonomic category than genus. Knowing the classification helps answer questions about these categories.

• ★The first word in a biological name is the genus.75:37
• ★The second word in a biological name is the specific epithet.75:37
• ★Biological names must be in Latin.75:37
• ★Phylum is a higher taxonomic category than genus.75:37

As we move down the taxonomic hierarchy, the general characters decrease. The taxonomic category with the least general character compared to genus is species. Species is the most basic unit of classification in biology.

Some similarities in taxonomy can also be referred to as specific characters. This distinction is important when considering taxonomic relationships.

• ★General characters decrease as one moves down the taxonomic hierarchy.77:46
• ★Species has the least general character compared to genus.77:55
• ★The basic unit of classification in biology is species.78:05
• ★Some similarities can also be called specific characters.78:15

Example: The question asks which taxonomic category is less general than genus, and the answer is species.78:00

The chapter has been completed. Students are encouraged to share their feedback in the comment section.

The instructor acknowledges students from Telangana and expresses gratitude for their participation.

• ★The chapter is finished.79:47
• ★Students should comment on their experience.79:48
• ★Instructor appreciates student engagement.79:50