Chapter 7: Diversity in Living Organism

 

Diversity in Life Forms 

Introduction

• A wide variety of life forms exist around us, each differing in characteristics.
• Even among humans, differences exist in height, facial features, and hand-span.
• Comparing humans with a monkey shows more similarities than with a cow.

Activity 7.1

• Different breeds of cows (Desi and Jersey) exhibit distinct characteristics.
• Within Desi cows, variations exist, yet they are identifiable as a group.
• Identification is based on key characteristics while ignoring minor differences.

Diversity in Life

• Organisms vary greatly in size, from microscopic bacteria to large blue whales (30m) and redwood trees (100m).
• Lifespan varies from a few days (mosquitoes) to thousands of years (pine trees).
• Color ranges from transparent worms to vibrant birds and flowers.
• This diversity has evolved over millions of years.

Need for Classification

• Due to the vast number of species, studying them individually is impractical.
• Scientists group organisms based on similarities to form categories.
• Major groups are formed using fundamental characteristics (broad classification).
• Subgroups are created based on less significant characteristics (detailed classification).

Conclusion

• Classification helps in systematically studying organisms by grouping them based on similarities and differences.

Basis of Classification

Introduction

• Classification of living organisms has been attempted since ancient times.
• Aristotle classified animals based on habitat (land, water, air), but this method is misleading since organisms in the same habitat can be very different (e.g., corals, whales, sharks).
• A better classification system is needed based on fundamental characteristics rather than superficial similarities.

What is a Characteristic?

• A characteristic is a specific feature or function of an organism.
• Examples:
  • Having five fingers is a characteristic.
  • The ability to move (humans) versus being stationary (banyan tree) is also a characteristic.

Hierarchical Classification System

• Classification follows a hierarchy, where fundamental characteristics form the broadest groups, and further subdivisions are made using less fundamental traits.
• Example:
  • Just as the foundation stones of a wall determine the shape of the wall, fundamental characteristics determine major classifications.

Key Characteristics Used for Classification

1. Type of Cell (Prokaryotic vs. Eukaryotic)

• Prokaryotic cells: No well-defined nucleus (e.g., bacteria).
• Eukaryotic cells: Have a nucleus and membrane-bound organelles (e.g., plants, animals).
• Presence of a nucleus allows multicellularity and specialization of functions.

2. Cellular Organization (Unicellular vs. Multicellular)

• Unicellular organisms: Single-cell life forms (e.g., Amoeba).
• Multicellular organisms: Cells work together with division of labor (e.g., worms, humans).

3. Mode of Nutrition (Autotrophic vs. Heterotrophic)

• Autotrophic: Organisms that produce their own food (e.g., plants through photosynthesis).
• Heterotrophic: Organisms that obtain food from others (e.g., animals).
• Nutrition type influences body design.

4. Level of Organization in Plants

• Among plants, classification is based on the complexity of body structures.

5. Body Organization in Animals

• Animals are classified based on development, body organization, and specialized organs (e.g., presence of a skeleton).

Conclusion

• Classification is based on fundamental characteristics that create broad groups.
• More specific characteristics help in forming sub-groups.
• Different classification criteria apply to plants and animals due to their structural and functional differences.

Classification and Evolution 

1. Basis of Classification

• Organisms are categorized based on body design, form, and function.
• Some characteristics influence major changes in body design more than others.
• Once a body design appears, it affects all future modifications.

2. Role of Time in Classification

• Characteristics that evolved earlier are more fundamental than those that appeared later.
• Classification is closely linked to evolution, as organisms evolve by accumulating changes that improve survival.

3. What is Evolution?

• Definition: Evolution is the gradual accumulation of changes in an organism’s body design to adapt and survive better.
• Charles Darwin introduced this concept in 1859 in his book The Origin of Species.

4. Evolution and Classification

• Some organisms have ancient body designs that have changed very little over time.
• Other organisms have recently evolved body designs with more modifications.
• Older organisms are sometimes called ‘primitive’ or ‘lower’, while newer ones are called ‘advanced’ or ‘higher’.
• These terms are misleading—what matters is that some organisms have existed longer while others evolved more recently.
• Over time, complexity in body design tends to increase, meaning that older organisms are generally simpler and younger ones more complex.

The Hierarchy of Classification

1. Classification of Living Organisms

• Biologists involved in classification:
  • Ernst Haeckel (1894), Robert Whittaker (1969), and Carl Woese (1977).
  • They classified all living organisms into broad groups called kingdoms.

2. Whittaker's Five-Kingdom Classification

• Five kingdoms proposed by Whittaker:
  1. Monera
  2. Protista
  3. Fungi
  4. Plantae
  5. Animalia
• Organisms are grouped based on:
  • Cell structure
  • Mode and source of nutrition
  • Body organization

3. Woese's Modification

• Carl Woese (1977) modified the classification of Monera, dividing it into:
  1. Archaebacteria (Archaea)
  2. Eubacteria (Bacteria)

4. Hierarchical Classification

• Organisms are classified into smaller and smaller groups. The classification hierarchy includes:
  1. Kingdom
  2. Phylum (for animals) / Division (for plants)
  3. Class
  4. Order
  5. Family
  6. Genus
  7. Species

5. Species - The Basic Unit

• Species is the most specific level of classification.
• Organisms belong to the same species if they are similar enough to breed and perpetuate.

Monera

1. Characteristics of Monera

• Lack of defined nucleus: Organisms in this group do not have a nucleus or membrane-bound organelles.
• Unicellular: All organisms in Monera are unicellular and do not exhibit multi-cellular body designs.

2. Diversity in Monera

• Cell Wall:

  • Some organisms in Monera have a cell wall; others do not.
  • The presence or absence of a cell wall affects body design significantly, but the effects are different from multi-cellular organisms.

• Mode of Nutrition:

  • Autotrophic: Some organisms synthesize their own food (e.g., through photosynthesis).
  • Heterotrophic: Others obtain food from the environment.

3. Examples of Organisms in Monera

• Bacteria
• Blue-green algae (Cyanobacteria)
• Mycoplasma

These organisms vary widely in their characteristics but share the basic features of being unicellular and lacking a defined nucleus.

Protista 

1. Characteristics of Protista

• Unicellular eukaryotes: Organisms in this group are unicellular and eukaryotic, meaning they have a defined nucleus and membrane-bound organelles.
• Mode of Nutrition:
  • Autotrophic: Some Protists can produce their own food (e.g., through photosynthesis).
  • Heterotrophic: Others obtain food from the environment.

2. Movement in Protista

• Many Protists use appendages for movement:
  • Cilia: Hair-like structures that help in locomotion.
  • Flagella: Whip-like structures for movement.

3. Examples of Protista

• Unicellular algae
• Diatoms
• Protozoans

These organisms are varied in form and function but share the characteristic of being unicellular eukaryotes.

Fungi 

1. Characteristics of Fungi

• Heterotrophic eukaryotes: Fungi are heterotrophic (they obtain food from external sources) and eukaryotic (have a defined nucleus and membrane-bound organelles).
• Mode of Nutrition:
  • Saprotrophs: Some fungi feed on decaying organic matter.
  • Parasites: Some fungi feed on the living protoplasm of a host organism.

2. Multicellularity in Fungi

• Fungi can become multicellular at certain stages in their life cycle.

3. Cell Wall Composition

• Fungi have cell walls made of a tough complex sugar called chitin.

4. Examples of Fungi

• Yeasts
• Molds
• Mushrooms

5. Symbiotic Relationships

• Some fungi form symbiotic relationships with blue-green algae (cyanobacteria), where both organisms benefit. These are called lichens.
• Lichens appear as slow-growing, colored patches on the bark of trees.

Plantae 

1. Classification of Plants

• The first level of classification depends on whether the plant body has well-differentiated, distinct parts.

  • Plants with clearly defined parts (roots, stems, leaves) are classified differently from those that don't have these parts.

• The next level of classification is based on the presence of specialized tissues for the transport of water and other substances.

  • Vascular plants: Have specialized tissues like xylem and phloem for transport.
  • Non-vascular plants: Lack such specialized tissues.

• Further classification focuses on:

  1. Ability to bear seeds:
     • Some plants produce seeds (seed-bearing plants), while others do not (spore-producing plants).
  2. Seeds enclosed within fruits:
     • Angiosperms (flowering plants) have seeds enclosed within fruits.
     • Gymnosperms (non-flowering plants) have seeds exposed, usually on cones.

Thallophyta 

1. Characteristics of Thallophyta

• Undifferentiated body design: Plants in this group do not have well-differentiated body parts like roots, stems, and leaves.
• Commonly known as algae: These plants are generally referred to as algae.
• Habitat: They are predominantly aquatic, living in both freshwater and marine environments.

2. Examples of Thallophyta

• Spirogyra
• Ulothrix
• Cladophora
• Ulva
• Chara

These plants are simple in structure, without specialized tissues for transport, and are primarily found in aquatic habitats.

Bryophyta 

1. Characteristics of Bryophyta

• Amphibians of the plant kingdom: Bryophytes are often called the amphibians of the plant kingdom because they thrive in damp environments.
• Differentiated plant body: The plant body is differentiated into stem-like and leaf-like structures. However, these parts are simple and lack the complexity of true stems and leaves found in higher plants.
• Lack of specialized tissues: Bryophytes do not have specialized tissues (like xylem and phloem) for conducting water and other substances. This means water absorption and transportation are limited to diffusion.

2. Examples of Bryophyta

• Moss (Funaria)
• Marchantia

Bryophytes are small, simple plants found in moist habitats and depend on water for reproduction.

Pteridophyta 

1. Characteristics of Pteridophyta

• Differentiated plant body: The plant body is differentiated into roots, stems, and leaves, making it more complex than Bryophytes.
• Specialized tissues for conduction: Pteridophytes have specialized tissues, such as xylem and phloem, for the conduction of water and other substances. This allows for more efficient nutrient and water transport throughout the plant.

2. Reproduction and Classification

• Cryptogams: The reproductive organs in Pteridophytes are inconspicuous and hidden, which is why they are often referred to as cryptogams (plants with hidden reproductive organs).
• Phanerogams: Plants with well-differentiated reproductive parts that eventually produce seeds are called phanerogams.
• Seed production: Seeds, which result from sexual reproduction, consist of the embryo and stored food that supports the embryo's initial growth during germination.

3. Examples of Pteridophyta

• Marsilea
• Ferns
• Horse-tails

These plants are more complex than Bryophytes and reproduce using spores rather than seeds.

Gymnosperms 

1. Characteristics of Gymnosperms

• Naked seeds: The seeds are not enclosed within fruits; they are exposed or "naked," which is reflected in the term gymnosperm (from Greek: gymno meaning "naked" and sperma meaning "seed").
• Perennial, evergreen, and woody: Gymnosperms are usually woody plants, and they can live for many years (perennial). They are typically evergreen, meaning they retain their leaves throughout the year.

2. Examples of Gymnosperms

• Pines
• Deodar

Gymnosperms are a group of seed-bearing plants that include trees and shrubs, known for their reproductive structure of exposed seeds, typically found in cones.

Angiosperms 

1. Characteristics of Angiosperms

• Covered seeds: Angiosperms, also known as flowering plants, produce seeds that are enclosed within an ovary, which later becomes a fruit.
• Cotyledons: The seeds contain cotyledons, which are also known as seed leaves. These cotyledons often emerge and become green during the germination process, providing initial nourishment to the embryo.
• Classification: Angiosperms are divided into two main groups based on the number of cotyledons in their seeds:
  • Monocots: Seeds with one cotyledon.
  • Dicots: Seeds with two cotyledons.

2. Examples of Angiosperms

• Monocots: Examples include maize, wheat, and tamarind.
• Dicots: Examples include green gram, peas.

3. Activity Observations

• Soaked seeds test: Soak seeds like green gram, wheat, maize, peas, and tamarind. When the seeds become tender, split them:
  • Seeds that break into two equal halves are dicot seeds.
  • Seeds that do not break into two equal halves are monocot seeds.

Other Characteristics of Monocots and Dicots:

• Roots:

  • Monocots: Have fibrous roots.
  • Dicots: Have tap roots.

• Leaves:

  • Monocots: Have parallel venation (veins run parallel to each other).
  • Dicots: Have reticulate venation (veins form a network).

• Flowers:

  • Monocots: Flowers typically have three petals or multiples of three.
  • Dicots: Flowers typically have four or five petals or multiples of these numbers.

These characteristics help distinguish monocots from dicots and further classify them in the plant kingdom.

Animalia 

Characteristics of Animalia:

• Eukaryotic: Animals have cells with a defined nucleus and membrane-bound organelles.
• Multicellular: Animals are made up of many cells.
• Heterotrophic: Animals obtain their nutrition by consuming other organisms, unlike plants which are autotrophic.
• No Cell Walls: Animal cells do not have rigid cell walls like plant cells.
• Mobility: Most animals are capable of movement at some stage of their life cycle.

Further Classification:

Animals are classified based on:

• The extent and type of differentiation in their body design. This includes the presence of specialized tissues, body symmetry, segmentation, and other structural features that differentiate animal groups.

Porifera 

Characteristics of Porifera:

• Non-motile: Porifera are sessile animals, meaning they are fixed to a solid surface.
• Pores: Their bodies are covered with numerous pores or holes. These pores are connected to a canal system that facilitates water circulation.
• Water Circulation: The canal system helps circulate water through the body, bringing in food and oxygen while removing waste.
• Minimal Differentiation: The body structure has minimal differentiation, meaning they lack true tissues and organs.
• Skeleton: Porifera have a hard external layer or skeleton, which provides support.
• Habitat: They are primarily found in marine environments.

Examples:

• Commonly called sponges. Examples include species shown in diagrams or images (e.g., Euspongia, Spongilla).

Coelenterata (Cnidaria) 

Characteristics of Coelenterata:

• Aquatic: Coelenterates live in water, primarily marine environments.
• Body Cavity: They have a central cavity (gastrovascular cavity) that is involved in digestion and circulation.
• Body Structure: The body is made up of two layers of cells:
  • Outer layer: Covers the outside of the body.
  • Inner layer: Lines the inside of the body.
• Body Design Differentiation: More advanced body design compared to Porifera, with two cell layers and differentiation into tissue.
• Solitary or Colonial: Some species are solitary, like Hydra, while others form colonies, like corals.

Examples:

• Jellyfish
• Sea Anemones
• Corals

Platyhelminthes (Flatworms) 

Characteristics of Platyhelminthes:

• Body Complexity: More complex than Porifera and Coelenterata.
• Bilateral Symmetry: The body is bilaterally symmetrical, meaning the left and right halves of the body are mirror images.
• Triploblastic: These animals have three layers of cells:
  • Ectoderm (outer layer)
  • Mesoderm (middle layer)
  • Endoderm (inner layer)
  This allows the formation of differentiated tissues and some organs.
• No Coelom: Despite having three cell layers, there is no true internal body cavity (coelom), so organs are not housed in a well-developed cavity.
• Dorsoventral Flattening: The body is flattened from top to bottom, leading to the name "flatworms."
• Habitat: They can be free-living or parasitic.

Examples:

• Free-living: Planarians
• Parasitic: Liver flukes, Tapeworms

Nematoda (Roundworms) 

Characteristics of Nematoda:

• Body Symmetry: Bilaterally symmetrical.
• Triploblastic: The body has three layers of cells:
  • Ectoderm (outer layer)
  • Mesoderm (middle layer)
  • Endoderm (inner layer)
  This allows for the development of tissues.
• Cylindrical Body: The body is cylindrical, unlike flatworms that are dorsoventrally flattened.
• Pseudocoelom: They possess a body cavity, known as a pseudocoelom, which is not fully lined with mesoderm, unlike a true coelom.
• No True Organs: There are tissues, but no fully developed internal organs like in higher animals.

Examples of Nematoda:

• Parasitic Worms:
  • Ascaris (roundworm)
  • Wuchereria (causes elephantiasis)
  • Pinworms

Annelida (Segmented Worms) 

Characteristics of Annelida:

• Body Symmetry: Bilaterally symmetrical.
• Triploblastic: The body is made up of three layers of cells:
  • Ectoderm (outer layer)
  • Mesoderm (middle layer)
  • Endoderm (inner layer)
  This allows for the formation of differentiated tissues and organs.
• True Coelom: Annelids have a true body cavity (coelom) that is fully lined with mesoderm, providing space for internal organs.
• Segmented Body: Their body is divided into a series of repeated segments, which allows for specialization and greater complexity in function.
• Extensive Organ Differentiation: As a result of the true coelom, annelids have well-developed organs and organ systems.
• Habitat: Annelids can be found in a variety of habitats including fresh water, marine water, and on land.

Examples of Annelida:

• Earthworm (Lumbricus)
• Leech (Hirudo)
• Marine Worm (Nereis)

Arthropoda (Jointed-Legged Animals) 

Characteristics of Arthropoda:

• Body Symmetry: Bilaterally symmetrical.
• Body Segmentation: The body is divided into distinct segments, with each segment potentially having specialized appendages.
• Open Circulatory System: The blood does not flow through well-defined blood vessels but instead flows freely in the coelomic cavity, bathing the organs directly.
• Jointed Appendages: The defining characteristic of arthropods, "arthropod" meaning "jointed legs". This includes legs, antennae, and other appendages.
• Exoskeleton: Arthropods have an external skeleton made of chitin that provides support and protection.
• Coelom: The coelom is blood-filled and serves as a space for organs to be suspended.
• Habitat: Arthropods are found in almost all environments, including land, air, and water.

Examples of Arthropoda:

• Prawn (Palaemon)
• Scorpion (Palamnaeus)
• Spider (Aranea)
• Butterfly (Papilio)
• Housefly (Musca)
• Cockroach (Periplaneta)
• Centipede (Scolopendra)

Mollusca 

Characteristics of Mollusca:

• Body Symmetry: Bilateral symmetry.
• Coelom: The coelomic cavity is reduced in size.
• Segmentation: There is little to no segmentation of the body.
• Circulatory System: Molluscs typically have an open circulatory system, meaning the blood is not confined to vessels and is free-flowing in the body cavity.
• Excretion: Molluscs have kidney-like organs to perform excretion.
• Foot: Molluscs possess a muscular foot that is used for movement and anchoring to surfaces.

Examples of Mollusca:

• Chiton
• Octopus
• Snail (Pila)
• Mussel (Unio)

Echinodermata 

Characteristics of Echinodermata:

• Body Structure: Known as spiny-skinned organisms, with hard calcium carbonate structures that form their skeleton.
• Habitat: Exclusively free-living marine animals.
• Symmetry: Triploblastic (three layers of cells).
• Coelom: They possess a coelomic cavity.
• Movement: Echinoderms have a unique water-driven tube system used for movement and other functions.

Examples of Echinodermata:

• Antedon (feather star)
• Holothuria (sea cucumber)
• Echinus (sea urchin)
• Asterias (sea star)

Protochordata 

Characteristics of Protochordata:

• Symmetry: Bilaterally symmetrical.
• Body Layers: Triploblastic (three layers of cells).
• Coelom: They possess a coelomic cavity.
• Notochord: A defining feature is the presence of a notochord at some stage of their life. The notochord is a long rod-like support structure that runs along the back, separating the nervous tissue from the gut. It provides a point for muscle attachment, aiding in movement.

Habitat: Marine animals.

Examples of Protochordata:

• Balanoglossus
• Herdmania
• Amphioxus

Vertebrata 

Characteristics of Vertebrata:

• Internal Skeleton: Presence of a true vertebral column and internal skeleton.
• Symmetry: Bilaterally symmetrical.
• Body Layers: Triploblastic (three layers of cells).
• Coelom: Coelomic animals with a well-developed body cavity.
• Segmentation: Body is segmented.
• Tissue & Organ Differentiation: High level of differentiation in body tissues and organs.

Defining Features of Chordates (Including Vertebrates):

1. Notochord: A rod-like structure providing support.
2. Dorsal Nerve Cord: A hollow nerve cord running along the back.
3. Triploblastic: Three germ layers present.
4. Paired Gill Pouches: Present at some stage of development.
5. Coelomate: Having a well-developed coelomic cavity.

Classification of Vertebrates:

Vertebrates are further divided into six classes, which include:

1. Cyclostomata
2. Pisces (Fishes)
3. Amphibia
4. Reptilia
5. Aves (Birds)
6. Mammalia (Mammals)

Cyclostomata 

Characteristics of Cyclostomata:

• Jawless Vertebrates: Lack true jaws.
• Body Shape: Elongated, eel-like body.
• Mouth Structure: Circular, suctorial mouth.
• Skin: Slimy and scaleless.
• Feeding Habit: Ectoparasites or borers of other vertebrates.
• Examples:
• Petromyzon (Lamprey)
• Myxine (Hagfish)

Pisces 

Characteristics of Pisces:

• Habitat: Exclusively aquatic.
• Body Covering: Skin covered with scales or plates.
• Respiration: Breathe using gills that extract dissolved oxygen from water.
• Body Shape: Streamlined body for efficient movement in water.
• Locomotion: Muscular tail used for movement.
• Temperature Regulation: Cold-blooded (ectothermic).
• Heart Structure: Two-chambered heart.
• Reproduction: Lay eggs (oviparous).
• Types Based on Skeleton Composition:
  • Cartilaginous Fish: Skeleton made entirely of cartilage (e.g., Sharks).
  • Bony Fish: Skeleton made of both bone and cartilage (e.g., Tuna, Rohu).

Examples:

• Synchiropus splendidus (Mandarin fish)
• Caulophyryne jordani (Angler fish)
• Pterois volitans (Lion fish)
• Torpedo (Electric ray)
• Scoliodon (Dog fish)
• Sting ray
• Labeo rohita (Rohu) – A commonly consumed freshwater fish.
• Exocoetus (Flying fish) – Has wing-like pectoral fins that allow it to glide above water.
• Anabas (Climbing perch) – Has the ability to survive in low-oxygen environments and can move on land using its pectoral fins.
• Hippocampus (Sea horse) – Unique fish where males carry eggs in a brood pouch until they hatch.

Key Features in Fish Anatomy:

• Mouth – Used for feeding.
• Pectoral fins – Helps in steering and balancing.
• Pelvic fins – Assist in stabilization.
• Dorsal fin – Helps in maintaining balance.
• Tail fin – Aids in propulsion and movement.
• Scales – Protect the body and reduce friction in water.
• Brood pouch (in Sea horse) – Male carries and nurtures developing embryos.

Amphibia 

Key Characteristics of Amphibians:

• Can live both in water and on land.
• Lack scales, unlike fish.
• Have mucus glands in their skin to keep it moist.
• Respire through gills (in the larval stage) and lungs (in adults).
• Cold-blooded animals.
• Have a three-chambered heart (two atria and one ventricle).
• Lay eggs in water; their larvae (e.g., tadpoles) are aquatic.

Examples of Amphibians:

• Rana tigrina (Common Frog) – Found in freshwater environments.
• Toad – Similar to frogs but with drier, bumpier skin.
• Hyla (Tree Frog) – Lives on trees and has adhesive pads on its feet.
• Salamander – Has a long tail and a lizard-like appearance.

Reptilia 

Key Characteristics of Reptiles:

• Cold-blooded animals.
• Covered with scales to prevent water loss.
• Breathe through lungs at all stages of life.
• Most have a three-chambered heart, but crocodiles have a four-chambered heart.
• Lay eggs with tough coverings on land, unlike amphibians.
• Do not depend on water for reproduction.

Examples of Reptiles:

• Turtle – Hard protective shell for defense.
• Chameleon – Can change color for camouflage.
• King Cobra – One of the largest venomous snakes.
• House Wall Lizard (Hemidactylus) – Commonly found in houses.
• Flying Lizard (Draco) – Has wing-like skin extensions for gliding.

Aves 

Key Characteristics of Aves (Birds):

• Warm-blooded animals (maintain constant body temperature).
• Have a four-chambered heart for efficient circulation.
• Body covered with feathers for insulation and flight.
• Forelimbs modified into wings for flying (except flightless birds).
• Lay eggs with hard shells for reproduction.
• Breathe through lungs with air sacs for efficient respiration.

Examples of Aves:

• White Stork (Ciconia ciconia) – A migratory bird.
• Ostrich (Struthio camelus) – The largest flightless bird.
• Male Tufted Duck (Aythya fuligula) – A diving bird.
• Pigeon – Common city bird.
• Sparrow – Small songbird.
• Crow – Intelligent and adaptable bird.

Mammalia 

Key Characteristics of Mammals:

• Warm-blooded animals (maintain constant body temperature).
• Four-chambered heart for efficient circulation.
• Possess mammary glands for producing milk to nourish young.
• Body covered with hair/fur for insulation.
• Have sweat and oil glands in the skin.
• Mostly give birth to live young (except monotremes like platypus and echidna, which lay eggs).
• Breathe through lungs with a well-developed diaphragm.

Examples of Mammals:

• Whale – A marine mammal adapted for aquatic life.
• Human – Highly developed brain and social behavior.
• Cat – A carnivorous domestic animal.
• Rat – A rodent with high adaptability.
• Bat – The only flying mammal.

Carolus Linnaeus

• Carolus Linnaeus (also known as Karl von Linne) was born in Sweden and worked as a doctor.
• At the age of 22, Linnaeus published his first paper on plants.
• He was the personal physician of a wealthy government official, during which time he studied the diversity of plants in his employer’s garden.
• Linnaeus published 14 papers and released the renowned book Systema Naturae, which laid the foundation for modern taxonomy.
• His classification system was simple and aimed at organizing plants for easy identification.

Nomenclature

Need for Systematic Naming of Living Organisms

Living organisms are found all over the world, and different languages have different names for the same organism. This can create confusion when people from different regions try to communicate about a specific species. To resolve this issue, scientists have developed a systematic way of naming organisms, known as scientific nomenclature.

This system ensures that each organism has a unique name that is recognized worldwide, similar to how chemical symbols and formulas are universally used in chemistry.

Scientific Naming and Its Origin

The system of naming organisms scientifically was introduced by Carolus Linnaeus in the 18th century. It follows a classification system that groups organisms based on their similarities. However, instead of listing the entire classification hierarchy, only the genus and species names are used.

Rules for Writing Scientific Names

1. The genus name begins with a capital letter.
2. The species name begins with a small letter.
3. When printed, the scientific name is written in italics.
4. When handwritten, both the genus and species names are underlined separately.

Activity 7.4: Scientific Names of Common Animals and Plants

Common Name	Scientific Name
Dog	Canis lupus familiaris
Cat	Felis catus
Mango	Mangifera indica
Banyan Tree	Ficus benghalensis
House Sparrow	Passer domesticus

Observations

• Scientific names are in Latin.
• They follow the naming conventions (Genus name capitalized, species name in lowercase).
• These names are different from common names but provide a universal way to identify species worldwide.

Mind Map