Patterns in Life Diversity and Classification Class 9 Notes Science Chapter 12

Experts have designed these Class 9 Science Notes and Exploration Chapter 12 Patterns in Life Diversity and Classification Class 9 Notes for effective learning.

Class 9 Science Chapter 12 Patterns in Life Diversity and Classification Notes

Class 9 Science Exploration Chapter 12 Notes

Class 9 Science Chapter 12 Notes – Class 9 Patterns in Life Diversity and Classification Notes

→ Angiosperms: Flowering plants that produce seeds enclosed within a fruit.
Example: Mango, Gulmohar.

→ Autotrophic Nutrition: A mode of nutrition in which an organism makes its own food, by photosynthesis.

→ Bilateral Symmetry: An arrangement of the body in which it can be divided into two equal halves along one plane.

→ Binomial Nomenclature: A system of naming organisms using two Latin names (genus and species), introduced by Carolus Linnaeus.

→ Biodiversity: The enormous variety of living organisms found on the Earth. It also includes species diversity, genetic diversity and ecosystem diversity.

→ Biodiversity Hotspot: A region that supports a large number of endemic species and has undergone significant habitat loss.
Example: The Western Ghats.

→ Biological Classification: The scientific system of grouping living organisms based on their similarities and differences.

→ Cyanobacteria (Blue-green algae): Photosynthetic prokaryotes classified under Kingdom Monera. These are among the first organisms to produce oxygen.

→ Endemic Species: Species that are found only in a particular region of the world and not naturally occurring anywhere else.
Example: Nilgiri tahr in India.

→ Endoskeleton: An internal skeletal structure that supports the body. Found in echinoderms and vertebrates.

→ Eukaryote: An organism whose cells have a well-developed nucleus and membrane-bound organelles.
Example: Amoeba, plants, animals.

→ Exoskeleton: A hard outer covering found in arthropods that provides protection, reduces water loss and supports muscles.

→ Fossil: Preserved remains or traces of plants or animals found in layers of rocks, sand or mud.

→ Genus: A classification group consisting of closely related species that share common features.

→ Gymnosperms: Plants that produce seeds not enclosed in a fruit; seeds are often found on cones.
Example: Pine.

→ Heterotrophic Nutrition: A mode of nutrition in which an organism depends on other organisms for food.

→ Invertebrate: An animal that lacks a notochord or vertebral column.
Example: Sponge, earthworm, crab.

→ Lichen: A symbiotic association between a heterotrophic fungus and an autotrophic alga. Used as a bioindicator of air pollution.

→ Mycelium: A network of fine filaments (hyphae) that form the body of a fungus.

→ Notochord: A flexible, rod-shaped structure that provides internal body support in chordates.

→ Phloem: The vascular tissue in plants responsible for transporting food (sugars) from leaves to other parts of the plant.

→ Prokaryote: An organism whose cells lack a nucleus and membrane-bound organelles.
Example: Bacteria.

→ Protochordate: A primitive chordate that possesses a notochord at least once during its life.
Example: Amphioxus.

→ Rhizoids: Root-like structures in bryophytes that help anchor the plant and absorb water.

→ Saprophyte: An organism that feeds on dead or decaying organic matter.
Example: Mushroom.

→ Segmentation: The division of the body into repeating units (segments). It is seen in annelids and arthropods.

→ Species: A group of organisms consisting of similar individuals capable of interbreeding and producing offsprings.

→ Stromatolite: Layered rock structures formed by ancient cyanobacteria. They provide some of the earliest evidence of life on Earth.

→ Thallus: A simple, undifferentiated plant body without true roots, stems or leaves, found in thallophytes (algae).

→ Vascular Tissue: Specialised tissues (xylem and phloem) in plants that transport water and food throughout the body.

→ Vertebral Column: A backbone made of vertebrae that supports the body and protects the spinal cord in vertebrates.

→ Vertebrate: An animal that possesses a vertebral column.
Example: Fish, bird, human.

→ Xylem: The vascular tissue in plants responsible for transporting water and minerals from roots to other parts of the plant.

Introduction

• Life on the Earth exists in an enormous variety of forms, from microscopic organisms invisible to the naked eye to giant trees, and from glowing jellyfish to soaring eagles. This immense variety of living organisms is known as biodiversity.
• Biodiversity is essential for life on Earth. Microscopic algae in oceans release most of the oxygen we breathe, fungi and bacteria decompose waste and make soil fertile, and birds, bees and bats pollinate flowers.
• For centuries, farmers have relied on their knowledge of diverse crop varieties with traits like drought tolerance and pest resistance, strengthening food security.
• Scientists group and classify organisms based on their shared characteristics and evolutionary relationships to study life systematically.
• Classification helps us understand how organisms are related and how they function.

India as a Biodiversity Hotspot

• The natural landscape of India is diverse, with mountains in the north, desert in the west, rainforests in the North East, plateaus in the south, and long coastlines along the Arabian Sea and the Bay of Bengal.
• Each region has distinct soil types and different climatic conditions like temperature and rainfall, which together support a wide variety of species.
• Endemic species are species restricted to a particular region and not found naturally anywhere else. Examples found only in India including Nilgiri tahr, Lion-tailed macaque, Indian pitcher plant (Nepenthes khasiana) and Neelakurinji.
• Biodiversity hotspots are regions that support a large number of endemic species and have undergone significant habitat loss. Global biodiversity hotspots in and around India are the Western Ghats, Indo-Burma (including North East India), the Himalayas, and Sundaland (including the Nicobar Islands).
• Protecting biodiversity hotspots is important because they support food webs and help ecosystems to remain healthy.

How has the Biodiversity Evolved?

• Today’s diversity is the outcome of continuous changes over a vast span of time, shaped by interactions between organisms and their surroundings.
• The biodiversity that we see today was not always the same. Small differences among individuals have transformed the biodiversity into what we witness today and affected their chances of survival and reproduction.
• These differences accumulated over many generations and gave rise to new forms of life.
• Ancient Indian traditions, such as the Sangam Tinai classification of landscapes and the protection of sacred groves, show a sophisticated ecological understanding that preserved locally diverse habitats.

How to Classify Organisms?

Scientists often look at broad and easily visible features first, and then at more detailed features.

→ Some Criteria to Classify Living Organisms:

The criteria used for grouping living organisms include:

1. External features: Visible characteristics like shape, size and body organisation.
2. Mode of nutrition: Autotrophic (make their own food) or heterotrophic (depend on others).
3. Internal structures: Skeletal patterns, presence or absence of organs and types of tissues.
4. Cell structure: Unicellular or multicellular, eukaryote or prokaryote, presence or absence of cell wall.
5. Ecological role: Producer, consumer or decomposer.
6. Reproduction: Asexual and/or sexual methods.
7. Genetic similarity: Similarities in inherited features studied through DNA.
   Similar features in organisms suggests that they have evolved from common ancestors.

The Need for Classification

• The scientific system of grouping living organisms based on their similarities and differences is known as biological classification.
• It makes study of living organisms more organised and systematic.
• It helps us understand similarities, differences and relationships among living beings.
• It helps in identifying and naming newly discovered organisms.
• It helps biodiversity conservation by identifying organisms under threat of extinction.
• It allows scientists worldwide to discuss organisms using a common system.

Biological Classification Systems Over Time

• Aristotle (4th century BCE): Grouped animals based on habitat (land, water, air) and external appearances.
• Carolus Linnaeus (1758): Two Kingdom System – Plantae (do not move, make own food) and Animalia (move, depend on others for food).
• Ernst Haeckel (1866): Three Kingdom System – added Protista for microscopic unicellular organisms.
• Herbert F. Copeland (1938): Four Kingdom System – separated bacteria into Monera because they lack a true nucleus.
• Robert H. Whittaker (1969): Five Kingdom System – Monera, Protista, Fungi, Plantae and Animalia. Fungi were separated because of heterotrophic nutrition and chitin cell walls.
• Carl Woese (1977): Three Domain System based on DNA studies – Bacteria, Archaea and Eukarya.

Five Kingdom Classification

All life forms are grouped based on four main criteria:

1. cell type (prokaryote or eukaryote)
2. level of organisation (unicellular or multicellular)
3. cell structure (presence or absence of cell wall)
4. mode of nutrition (Autotrophic or heterotrophic)

→ Kingdom Monera—Unicellular Prokaryotes

• Unicellular prokaryotes like bacteria and cyanobacteria.
• Found everywhere, including soil, water, air, hot springs, extreme environments and even inside human bodies.
• Some are harmful (pathogens) and cause diseases, but many are useful, like Lactobacillus and Rhizobium.
• Cyanobacteria are autotrophs; some bacteria break down pollutants like oil, pesticides and sewage.
• They are also found in the gut of ruminants and are responsible for the production of biogas from their dung.
• Cyanobacteria (blue-green algae) were among the first organisms to produce oxygen through photosynthesis. About 2.5 billion years ago, oxygen accumulated in the atmosphere, made the Earth suitable for other forms of life.

→ Kingdom Protista—Unicellular Eukaryotes

• Unicellular eukaryotes without a cell wall or with a cell wall made up of cellulose. Examples: Amoeba, Paramecium, Euglena.
• They live in water or moist places; some are autotrophic, others are heterotrophic.
• They are an important link in aquatic food chains, produce oxygen, serve as food for small animals, and some act as decomposers.

→ Kingdom Fungi- Multicellular, Heterotrophic Eukaryotes with a Cell Wall

• Mostly multicellular eukaryotes; cell wall made of chitin.
• Heterotrophic: Absorb nutrients through fine filaments that form a network called the mycelium.
• Most fungi are saprophytes (feed on dead organic matter); some are symbiotic, some are parasites.
  Examples: Yeast (unicellular, but placed under Fungi because its cell wall is chitin), mushrooms, bread mould, Aspergillus and Penicillium (used to make enzymes and antibiotics).
• Fungi are important decomposers; they recycle nutrients and maintain soil fertility.

→ Kingdom Plantae- Multicellular, Autotrophic Eukaryotes with a Cell Wall

• Multicellular, autotrophic eukaryotes that perform photosynthesis.
• Their cell walls are mainly made of cellulose, which provides support and protection.
• Plants form the base of most food chains and release oxygen essential for life.

Kingdom Plantae is divided into five classes:

(a) Thallophyta (algae):
Simplest plants with an undifferentiated thallus body. Mostly aquatic.
Example: Spirogyra.

(b) Bryophyta (mosses, liverworts):
Have rhizoids, leaf-like and stem-like structures but no vascular tissue. Need water for reproduction. Known as the ‘amphibians of the plant kingdom’.
Examples: Marchantia, moss.

(c) Pteridophyta (ferns):
First land plants. True roots, stems and leaves; vascular tissues (xylem and phloem) present. Still need water for reproduction. Do not produce seeds.
Examples: Pteris,Dryopteris.

(d) Gymnosperms (pines, cycads):
Well adapted to cold and dry regions. Produce seeds on cones; seeds are not enclosed in fruits. Needle-like leaves reduce water loss. Do not need water for fertilisation.

(e) Angiosperms (flowering plants):
Plants with most complex body organisation. Produce flowers and fruits; seeds are enclosed in fruits. Most diverse plant group on Earth.
Examples: Gulmohar, mango.

→ Kingdom Animalia- Multicellular, Heterotrophic Eukaryotes

• Multicellular, heterotrophic eukaryotes without a cell wall.
• Shows locomotion, rapid response to stimuli and coordinated behaviour.
• On the basis of the presence or absence of a notochord (a flexible rod-shaped structure), animals are classified into Non-chordata (Invertebrata) and Chordata.
• Invertebrate phyla (in order of increasing complexity): Porifera, Cnidaria, Platyhelminthes, Nematoda, Annelida, Arthropoda, Mollusca, Echinodermata.
• Protochordates, such as Amphioxus, possess a notochord at least once during their life.
• Vertebrates have a vertebral column (backbone) and are classified into five groups: fish, amphibians, reptiles, birds and mammals.

Features of the Invertebrate Phyla:

1. Porifera (sponges):
Simplest body plan. Lack organisation of tissues and organs. Pores in the body, Sponges remain fixed at one place, aquatic.

2. Cnidaria (Hydra, jellyfish, corals):
Tissue level organisation; tentacles for catching prey; single opening for food and waste.

3. Platyhelminthes (flatworms):
Bilateral symmetry; flattened body; body organisation allows better coordination of movement; many are parasites with hooks and suckers. These cause infectious diseases in humans. They live in the human alimentary canal.

4. Nematoda (roundworms):
Elongated, cylindrical body; two openings (mouth and anus); organ system level. Distinct male and female worms.

5. Annelida (earthworms):
Segmented body – greater flexibility; body cavity; organ system level organisation. Muscles help in locomotion and nerve cord helps in control and coordination.

6. Arthropoda (insects, crabs, spiders):
Jointed appendages; fragmented body with different segments specialised for different functions; hard exoskeleton; most diverse animal group.

7. Mollusca (snails, squids, octopuses):
Organ system level of organisation; soft body often protected by a shell; muscular foot and a hump.

8. Echinodermata (starfish, sea urchins):
Spiny skin; lack notochord but internal skeleton of calcium carbonate provides them protection and controlled movement; marine.

→ Features of Protochordates (Amphioxus):

• Possess a notochord atleast once during their life. This structure provides internal support without restricting movement and represents a crucial change in body organisation.
• Protochordates are primitive type of chordates which help us understand how animals with a notochord may have arisen from simpler forms.

→ Features of the Vertebrate Classes (animals with a back bone)

• Possess a vertebral column (backbone), an internal skeletal structure that supports the body and protects vital organs, such as the brain and the spinal cord.
• Internal framework allows a larger body size, efficient movement and the development of complex organ systems.
• Shows advanced sensory abilities and coordinated behaviour.

Vertebrates are classified into five groups:

1. Fish: Aquatic; streamlined body; breathe through gills; move using fins; covered with scales; lay eggs in water.
2. Amphibians: Live on both land and water (like frogs, toads); moist, scale-less skin; breathe through lungs and skin; lay eggs in water.
3. Reptiles: Land-dwelling (like lizards, snakes, turtles); dry, scaly skin; breathe through lungs; lay eggs on land with a leathery shell.
4. Birds: Body covered with feathers; forelimbs modified into wings; hollow bones for flight; lay hard-shelled eggs; warm-blooded.
5. Mammals: Body covered with fur or hair; mammary glands produce milk to feed young; warm-blooded; mostly give birth to live young (viviparous); examples include humans, dogs, whales.

Adaptations as Outcomes of Structural Change

Diversity in animals reflects changes in their body structure over long periods of time.
Examples:
Fins and gills for fish, feathers and hollow bones for birds, thick fur for polar bears, fat storage (hump) for camels, mammary glands in mammals.

→ The Hierarchical Nature of Classification:

• Kingdom → Phylum/Division → Class → Order → Family → Genus → Species
• At each lower level, organisms share more common features.
• Classification helps scientists identify, compare and study organisms accurately, and understand how they are related.

Scientific Naming – The Binomial System

• A universal two-part naming system called binomial nomenclature was introduced by Carolus Linnaeus in the 18th century.
• Every name has two parts in Latin— the genus name first (capital letter) and the species name second (lower case). The name is italicised in print or underlined when handwritten.
• Examples: Tiger is Panthera tigris; lion is Pcmthera leo\ mango is Mangifera indica.

→ Three-domain system Carl Woese (1977):

• The five-kingdom classification offered a more comprehensive way to group organisms compared to the previous systems, but it still could not fully explain the diversity of life.
• Latest advances in genetic research aided in modifying this classification. With advances in microscopes and genetic studies, scientists began to compare organisms at the DNA level.
• Organisms with similar DNA are considered to have a common ancestry.
• Based on the genetic data, Carl Woese (1977) proposed the three-domain system: Bacteria, Archaea, Eukarya.
• This system showed that microscopic life forms are far more diverse than previously believed.

Fossils as Evidence

• Fossils are preserved remains of plants and animals found in layers of rocks, sand and mud.
• Older layers contain simpler organisms, while newer layers show more complex forms.
• Fossils of ancient cyanobacteria are found in stromatolites, discovered in Rajasthan and Madhya Pradesh.

Biodiversity Under Threat

• Each species plays an important role in nature – plants produce food and oxygen, animals pollinate and disperse seeds, microorganisms recycle nutrients.
• Human activities like pollution, deforestation, overuse of resources and climate change are reducing biodiversity.
• When one species disappears, others that depend on it may also decline and eventually disappear.