Chapter 12: Patterns in Life: Diversity and Classification

• The Earth has a huge variety of living organisms.
• Some organisms are microscopic, such as bacteria and algae.
• Some organisms are large and complex, such as trees, birds and mammals.
• This variety of life forms is called biodiversity.

Meaning of Biodiversity

• Biodiversity means the variety of living organisms found on Earth.
• It includes:
• Plants
• Animals
• Fungi
• Bacteria
• Other microorganisms

Importance of Biodiversity

• Biodiversity is essential for life on Earth.
• Every organism plays an important role in nature.
• Examples:
• Algae release oxygen.
• Plants prepare food through photosynthesis.
• Fungi and bacteria decompose dead matter and recycle nutrients.
• Birds, bees and bats help in pollination.
• Plants provide food and shelter to many organisms.

Human Dependence on Biodiversity

• Humans depend on biodiversity for:
• Food
• Shelter
• Medicines
• Clothing
• Livelihood

Biodiversity and Farming

• Farmers have traditionally used different crop varieties.
• Crop diversity helps in:
• Drought tolerance
• Pest resistance
• Growth in poor soil
• Reducing crop failure
• Strengthening food security

Need for Classification

• There are millions of organisms on Earth.
• To study them properly, scientists group them according to their similarities and differences.
• This scientific grouping is called classification.

• India has a very diverse natural landscape.
• It includes:
• Mountains in the north
• Desert in the west
• Rainforests in North East India
• Plateaus in the south
• Long coastlines along the Arabian Sea and Bay of Bengal
• These regions have different:
• Soil types
• Temperature
• Rainfall
• Habitats
• Because of these varied habitats, India supports a large variety of plants and animals.

Endemic Species

• Some species are found naturally only in a particular region.
• Such species are called endemic species.

Examples of Endemic Species in India

• Nilgiri tahr
• Lion-tailed macaque
• Nepenthes khasiana, an Indian pitcher plant
• Neelakurinji

Biodiversity Hotspot

• A biodiversity hotspot is a region that:
• Supports a large number of endemic species
• Has undergone significant habitat loss

Important Biodiversity Hotspots Related to India

• Western Ghats
• Indo-Burma region, including North East India
• Himalayas
• Sundaland, including the Nicobar Islands

Importance of Biodiversity Hotspots

• These areas are important because they:
• Support rich biodiversity.
• Protect many endemic species.
• Maintain food webs.
• Help ecosystems remain healthy.
• Need urgent conservation.

• Biodiversity on Earth was not always the same.
• It changed gradually over a very long period of time.
• Small differences among individuals affected their chances of:
• Survival
• Reproduction
• Adaptation
• Organisms with useful features survived better in changing conditions.
• These useful features were passed from one generation to the next.
• Over many generations, these changes gave rise to new forms of life.

Main Idea

• Present-day biodiversity is the result of:
• Continuous changes
• Long periods of time
• Interaction between organisms and their surroundings
• Evolutionary relationships
• Classification helps us study this biodiversity in a systematic way.

• Organisms can be grouped in different ways.
• The same organism can be placed in different groups depending on the criterion used.

Examples of Grouping Criteria

• Habitat
• Land organisms
• Water organisms
• Air organisms
• Food habits
• Herbivores
• Carnivores
• Omnivores
• Body structure
• Animals with wings
• Animals with legs
• Animals with scales
• Animals with backbone
• Time of activity
• Active during the day
• Active during the night
• Active both day and night

Important Point

• Scientists choose important and meaningful features to classify organisms.
• Classification is a systematic way of organising living diversity.

Scientists use many characteristics to classify living organisms.

1. External Features

• These are visible characteristics.
• Examples:
• Shape
• Size
• Colour
• Body covering
• Body organisation

2. Mode of Nutrition

• Organisms are grouped according to how they obtain food.

Types

• Autotrophic organisms
• They prepare their own food.
• Example: green plants
• Heterotrophic organisms
• They depend on other organisms for food.
• Examples: animals and fungi

3. Internal Structures

• Scientists study internal features such as:
• Skeleton
• Organs
• Tissues
• Organ systems

4. Cell Structure

• Organisms are classified on the basis of:
• Unicellular or multicellular body
• Prokaryotic or eukaryotic cell
• Presence or absence of cell wall

5. Ecological Role

• Organisms may be grouped as:
• Producers
• Consumers
• Decomposers

6. Reproduction

• Organisms are classified according to their method of reproduction.
• Reproduction may be:
• Asexual
• Sexual
• Both sexual and asexual

7. Genetic Similarity

• Scientists study DNA to understand genetic similarity.
• Similar DNA shows that organisms may have a common ancestry.

• Earth has millions of organisms.
• Without classification, it would be difficult to study them.
• Classification helps us arrange organisms in an organised manner.

Biological Classification

• Biological classification is the scientific system of grouping living organisms on the basis of similarities and differences.

Importance of Biological Classification

• Classification helps in:
• Making the study of organisms organised and systematic
• Understanding similarities and differences among organisms
• Understanding how organisms are related
• Studying how organisms interact
• Identifying and naming newly discovered organisms
• Supporting biodiversity conservation
• Providing a common system for scientists worldwide

Example: Pakke Tiger Reserve

• Pakke Tiger Reserve in Arunachal Pradesh has many bird species.
• It supports four species of hornbills:
• Rufous-necked Hornbill
• Oriental Pied Hornbill
• Great Hornbill
• Wreathed Hornbill
• Classification helps scientists:
• Keep track of many species.
• Distinguish similar-looking organisms.
• Understand links between birds, trees and fruits.
• Study biodiversity more accurately.

• Classification systems have changed with time.
• New discoveries and better tools, such as microscopes, helped scientists improve classification.

Aristotle’s Classification

• Aristotle grouped animals mainly on the basis of:
• Habitat
• External appearance

Habitat-Based Groups

• Land animals
• Water animals
• Air animals

Limitation

• This system was not very accurate because it used only easily visible features.

Two Kingdom Classification

• In the 18th century, organisms were divided into two kingdoms:
• Plantae
• Animalia

Kingdom Plantae

• Included organisms that:
• Do not move from place to place
• Prepare their own food

Kingdom Animalia

• Included organisms that:
• Move from place to place
• Depend on others for food

Limitation

• This system created confusion for organisms like:
• Amoeba
• Paramecium
• Bacteria

Three Kingdom Classification

• A third kingdom called Protista was added.
• Protista included unicellular microscopic organisms.

Four Kingdom Classification

• Scientists later discovered that bacteria do not have a true nucleus.
• So, bacteria were placed in a separate kingdom called Monera.

Four Kingdoms

• Monera
• Protista
• Plantae
• Animalia

Five Kingdom Classification

• Fungi were later placed in a separate kingdom.
• This was because fungi:
• Do not prepare their own food.
• Absorb nutrients from dead and decaying matter.
• Have a different mode of nutrition from plants.

Five Kingdoms

• Monera
• Protista
• Fungi
• Plantae
• Animalia

Important Scientist

• The five kingdom classification was proposed by Robert H. Whittaker in 1969.

• Five kingdom classification groups all life forms on the basis of important features.

Main Criteria of Five Kingdom Classification

• Cell type
• Prokaryotic or eukaryotic
• Cell structure
• Presence or absence of cell wall
• Level of organisation
• Unicellular or multicellular
• Mode of nutrition
• Autotrophic or heterotrophic
• Ecological role
• Producer, consumer or decomposer

• Kingdom Monera includes unicellular prokaryotic organisms.

Main Features

• They are single-celled.
• They do not have a true nucleus.
• Their genetic material is not enclosed in a nuclear membrane.
• They may live in:
• Soil
• Water
• Air
• Hot springs
• Extreme environments
• Inside human bodies
• Inside animals

Examples

• Bacteria
• Cyanobacteria

Useful Bacteria

• Lactobacillus
• Helps in curd formation.
• Rhizobium
• Helps in nitrogen fixation.
• Some bacteria help in:
• Biogas production
• Breaking down pollutants
• Nutrient cycling

Harmful Bacteria

• Some bacteria are pathogens.
• They can cause diseases in humans, animals and plants.

Cyanobacteria

• Cyanobacteria are also called blue-green algae.
• They are autotrophic.
• They produce food by photosynthesis.
• They were among the earliest organisms to release oxygen into the atmosphere.

• Kingdom Protista includes unicellular eukaryotic organisms.

Main Features

• They are single-celled.
• They have a true nucleus.
• They mostly live in:
• Water
• Moist places
• Some protists are autotrophic.
• Some protists are heterotrophic.
• Some have a cell wall, while others do not.

Examples

• Amoeba
• Paramecium
• Euglena
• Chlamydomonas

Importance of Protists

• Protists are important in aquatic food chains.
• They help by:
• Producing oxygen
• Serving as food for small animals
• Helping in nutrient cycling
• Acting as decomposers in some cases

• Fungi are mostly multicellular eukaryotes.
• Their cell wall is made of chitin.

Main Features

• They do not prepare their own food.
• They are heterotrophic.
• They absorb nutrients from dead and decaying matter.
• Most fungi are saprophytes.
• Some fungi are parasites.
• Some fungi live in symbiotic relationships.
• They reproduce by spores.
• They grow best in warm and moist conditions.

Examples

• Yeast
• Bread mould
• Aspergillus
• Penicillium
• Mushroom

Special Point About Yeast

• Yeast is unicellular.
• Still, it is placed in Kingdom Fungi because its cell wall is made of chitin.

Importance of Fungi

• Fungi act as decomposers.
• They break down dead plants and animals.
• They convert complex organic matter into simpler substances.
• They help in:
• Nutrient recycling
• Maintaining soil fertility
• Maintaining ecological balance

Uses of Fungi

• Some fungi are used to make:
• Antibiotics
• Enzymes
• Food products
• Mushrooms are used as food.
• Mushroom farming is useful because it requires:
• Less space
• Low investment
• Short growing cycle

• Kingdom Plantae includes multicellular autotrophic eukaryotes.

Main Features

• Plants are multicellular.
• They are autotrophic.
• They prepare food by photosynthesis.
• Their cells have a rigid cell wall made mainly of cellulose.
• They form the base of most food chains.
• They release oxygen, which is essential for life.

Main Groups of Kingdom Plantae

• Thallophyta
• Bryophyta
• Pteridophyta
• Gymnosperms
• Angiosperms

Thallophyta Algae — Primitive Plants

• Thallophytes are among the simplest plant forms.

Main Features

• Their body is called a thallus.
• The body is not differentiated into true:
• Root
• Stem
• Leaves
• They are mostly found in:
• Water
• Moist places
• They can directly exchange:
• Gases
• Nutrients
• Water

Example

• Spirogyra

Advantages

• Simple body helps them survive in water.
• They can absorb water and nutrients easily.

Challenges

• They cannot live properly on land.
• They depend mainly on aquatic or moist environments.

Bryophyta — First Steps on Land, Still Need Water

• Bryophytes include mosses and liverworts.
• They show an important shift from water to land.

Main Features

• They grow in:
• Moist places
• Shady places
• Damp rocks
• Old walls
• Soil surfaces during monsoon
• They have root-like structures called rhizoids.
• They may have simple stem-like and leaf-like structures.
• They do not have well-developed vascular tissues.
• They need water for reproduction.

Examples

• Marchantia
• Moss

Special Name

• Bryophytes are called amphibians of the plant kingdom.
• This is because:
• They can live on land.
• But they need water for reproduction.

Advantages

• They can live on moist land.
• Their body is more differentiated than thallophytes.

Challenges

• They always need moisture.
• They lack vascular tissues.
• They cannot grow very tall.

Pteridophyta — Adaptation to Land and Having Structural Transport System

• Pteridophytes are more advanced than bryophytes.

Main Features

• They have true:
• Roots
• Stems
• Leaves
• They have vascular tissues:
• Xylem
• Phloem

Functions of Vascular Tissues

• Xylem transports water.
• Phloem transports food.

Reproduction

• They do not produce seeds.
• They still need water for reproduction.

Example

• Fern

Advantages

• They can live on land.
• They can transport water and food to different parts of the plant.
• They have a better body organisation than bryophytes.

Challenges

• They do not produce seeds.
• They need water for reproduction.

Gymnosperms — Reproduction Without Water

• Gymnosperms are seed-producing plants.
• The word gymnosperm means naked seed.

Main Features

• They produce seeds.
• Their seeds are not enclosed inside fruits.
• Seeds are often exposed on cones.
• They do not require water for fertilisation.
• They are adapted to cold and dry regions.
• They may have needle-like or scale-like leaves.

Examples

• Pine
• Cycas

Advantages

• They reproduce without water.
• Their seeds protect the embryo.
• Needle-like leaves reduce water loss.
• They can survive in dry and cold conditions.

Challenges

• Seeds are not enclosed in fruits.
• Seed dispersal is less efficient than angiosperms.

Angiosperms — Efficient Reproduction and Seed Dispersal

• Angiosperms are flowering plants.
• They are the most diverse plant group on Earth.

Main Features

• They have well-developed:
• Roots
• Stems
• Leaves
• They produce:
• Flowers
• Fruits
• Seeds
• Their seeds are enclosed inside fruits.
• Flowers help in pollination.
• Fruits help in seed dispersal.

Examples

• Gulmohar
• Rose
• Mango
• Grass
• Pea

Advantages

• Flowers attract pollinators.
• Fruits protect seeds.
• Fruits help seeds spread to new places.
• They can occupy many types of environments.

Challenges

• Reproduction may depend on pollinating agents such as:
• Insects
• Birds
• Wind
• Water

Table 12.3: Classes of Kingdom Plantae with Advantages and Challenges

Overall Pattern in Plant Evolution

• Plant groups show a sequence of structural changes.
• Early plants depended on water.
• Later plants developed:
• Vascular tissues
• Seeds
• Flowers
• Fruits
• These features helped plants survive better on land.

• Kingdom Animalia includes multicellular heterotrophic eukaryotes.

Main Features

• Animals are multicellular.
• They are heterotrophic.
• They depend on other organisms for food.
• Most animals can move from place to place.
• They respond quickly to stimuli.
• They show coordinated behaviour.
• Their cells do not have cell walls.

Basis of Animal Classification

• One major criterion for classifying animals is the presence or absence of a notochord.

Notochord

• A notochord is a flexible rod-like structure.
• It provides support to the body.

Main Groups of Animals

• Animals are divided into:
• Non-chordata or Invertebrates
• Chordata

Chordata is Further Divided Into

• Protochordates
• Vertebrates

Invertebrates — Animals Without a Notochord

• Invertebrates do not have a notochord.
• They show many types of body organisation.
• Their body organisation ranges from simple to complex.

Major Invertebrate Groups

• Porifera
• Cnidaria
• Platyhelminthes
• Nematoda
• Annelida
• Arthropoda
• Mollusca
• Echinodermata

Porifera — Pore-Bearers

• Porifera includes sponges.

Main Features

• They are aquatic animals.
• They are multicellular.
• They lack true tissues and organs.
• Their body has many pores.
• Water flows through the pores.
• Water brings food and oxygen.
• Water also carries away waste.
• They remain fixed in one place.

Example

• Sponge

Level of Organisation

• Cellular level organisation

Cnidaria — True Tissues and Active Feeding

• Cnidarians show tissue-level organisation.

Main Features

• They have true tissues.
• They have tentacles.
• Tentacles help in capturing prey.
• They have a single opening.
• The same opening is used for:
• Food intake
• Waste removal

Examples

• Hydra
• Jellyfish
• Corals

Level of Organisation

• Tissue level organisation

Platyhelminthes — Flatworms

• Platyhelminthes are commonly called flatworms.

Main Features

• Their body is flattened.
• They show bilateral symmetry.
• Their body has:
• Head-tail region
• Front-back region
• They have a single opening for:
• Food intake
• Waste removal
• Many flatworms are parasitic.
• Parasitic forms may have:
• Hooks
• Suckers

Example

• Tapeworm

Level of Organisation

• Organ level organisation

Nematoda — Roundworms

• Nematodes are commonly called roundworms.

Main Features

• They have elongated cylindrical bodies.
• They have two openings:
• Mouth
• Anus
• They may live in:
• Soil
• Water
• Host tissues
• Male and female worms are distinct.

Example

• Roundworm

Level of Organisation

• Organ system level organisation

Annelida — Segmented Worms

• Annelids have segmented bodies.

Main Features

• Their body is cylindrical.
• Their body is divided into segments.
• They have a body cavity.
• They possess organ system level organisation.
• Muscles help in movement.
• Nerve cord helps in control and coordination.

Example

• Earthworm

Advantage of Segmentation

• Segmentation helps in:
• Flexible movement
• Better body control
• Efficient locomotion

Arthropoda — Jointed Appendages and an External Skeleton

• Arthropoda is the largest animal group.
• The word arthropoda means jointed appendages.

Main Features

• They have jointed legs or appendages.
• Their body is segmented.
• Different body segments perform different functions.
• They have a hard external skeleton called exoskeleton.

Examples

• Insects
• Crabs
• Spiders
• Beetles

Advantages of Exoskeleton

• The exoskeleton:
• Protects the body
• Reduces water loss
• Supports powerful muscles
• Helps survival in dry and exposed environments

Mollusca — Organ System Level Organisation with Soft Bodies

• Molluscs have soft bodies.

Main Features

• They show organ system level organisation.
• Their body is soft.
• Many molluscs have a shell.
• The shell protects the soft body.
• Their body may have:
• Distinct head
• Muscular foot
• Hump

Examples

• Snail
• Squid
• Octopus

Echinodermata — Internal Support Without a Notochord

• Echinoderms are marine animals.
• The word echinodermata means spiny skin.

Main Features

• They have a hard internal skeleton.
• The skeleton is made of calcium carbonate.
• They do not have a notochord.
• Internal skeleton helps in:
• Protection
• Controlled movement

Examples

• Starfish
• Sea urchin

Looking Across Invertebrates

• From sponges to echinoderms, body organisation becomes more complex.
• New structural features improve:
• Feeding
• Movement
• Protection
• Survival

Main Changes Seen in Invertebrates

• Development of true tissues
• Development of bilateral symmetry
• Development of two openings in digestive tract
• Development of body cavity
• Development of segmentation
• Development of exoskeleton or endoskeleton
• Development of organ systems

Protochordates — The Appearance of the Notochord

• Protochordates are primitive chordates.
• They have a notochord at least once during their life.

Main Features

• They show the beginning of chordate features.
• Their notochord provides internal support.
• They help us understand how animals with a notochord evolved from simpler forms.

Example

• Amphioxus

Vertebrates — Animals with a Backbone

• Vertebrates have a vertebral column, also called a backbone.

Main Features

• They have an internal skeleton.
• The backbone supports the body.
• It protects the spinal cord.
• They have complex organ systems.
• They show advanced sensory abilities.
• They show coordinated behaviour.
• They can have larger body size and efficient movement.

Main Groups of Vertebrates

• Fish
• Amphibians
• Reptiles
• Birds
• Mammals

Basis of Vertebrate Classification

• Vertebrates are classified on the basis of:
• Habitat
• Body covering
• Reproduction
• Body structure

• Adaptations are special features that help organisms survive in their environment.
• These adaptations are outcomes of structural changes over long periods of time.

Examples of Adaptations

• Fish
• Have fins for swimming.
• Have gills for breathing in water.
• Birds
• Have feathers for flight.
• Have hollow bones to make the body light.
• Camels
• Store fat to survive in desert conditions.
• Polar bears
• Have thick fur to survive in cold regions.
• Mammals
• Have mammary glands to feed young ones.

Main Idea

• Different organisms have different body structures.
• These structures help them survive in different environments.

• Classification follows a step-by-step order.
• It starts from broad groups and moves to smaller and more specific groups.
• At each lower level, organisms share more common features.

Classification Hierarchy

• Kingdom
• Phylum
• Class
• Order
• Family
• Genus
• Species

Example: Classification of Tiger

• Kingdom: Animalia
• Phylum: Chordata
• Class: Mammalia
• Order: Carnivora
• Family: Felidae
• Genus: Panthera
• Species: Panthera tigris

Example: Classification of Pea Plant

• Kingdom: Plantae
• Phylum: Magnoliophyta
• Class: Magnoliopsida
• Order: Fabales
• Family: Fabaceae
• Genus: Pisum
• Species: Pisum sativum

Importance of Hierarchy

• It helps scientists:
• Identify organisms accurately.
• Compare organisms.
• Study relationships among organisms.
• Understand evolutionary connections.

• Different languages use different names for the same organism.
• This can create confusion.

Example

• Tiger is called:
• Bagh in Hindi
• Puli in Tamil
• Tiger in English
• Tigre in French
• To avoid confusion, scientists use a universal naming system called binomial nomenclature.

Binomial Nomenclature

• Binomial nomenclature is a system of giving every organism a scientific name with two parts.
• This system was introduced by Carolus Linnaeus.

Two Parts of Scientific Name

• Genus name
• Species name

Examples

• Tiger: Panthera tigris
• Mango: Mangifera indica

Explanation

• In Panthera tigris:
• Panthera is the genus.
• tigris is the species.
• In Mangifera indica:
• Mangifera is the genus.
• indica is the species.

Genus

• A genus includes closely related species.
• Example:
• Tiger and lion belong to the genus Panthera.

Species

• A species is a group of similar organisms that can interbreed and produce offspring.

Rules for Writing Scientific Names

• The scientific name has two parts:
• Genus
• Species
• The genus name is written first.
• The genus name begins with a capital letter.
• The species name is written second.
• The species name begins with a small letter.
• The scientific name is written in italics when printed.
• When handwritten, both words are underlined separately.

Example

• Printed form: Panthera tigris
• Handwritten form: Panthera tigris should be underlined separately.

Three Domain System

• The five kingdom classification is useful but has limitations.
• With advances in microscopes and genetic studies, scientists began to compare organisms at the DNA level.

Carl Woese’s Three Domain System

• Carl Woese proposed the three domain system in 1977.

Three Domains of Life

• Bacteria
• Archaea
• Eukarya

Importance

• This system showed that microscopic life forms are more diverse than previously believed.
• It is based mainly on genetic differences.

• Fossils are preserved remains or traces of plants and animals.
• They are found in layers of:
• Rocks
• Sand
• Mud

Importance of Fossils

• Fossils act as natural records of the past.
• They help us understand how life changed over millions of years.
• They provide evidence for evolution.

Fossil Layers

• Older rock layers generally contain simpler organisms.
• Newer rock layers generally contain more complex organisms.

Fossils Help Scientists Understand

• Evolution of life
• Relationship between present and ancient organisms
• Changes in biodiversity over time
• Past environments of Earth

Meet a Scientist — Birbal Sahni

• Birbal Sahni was an eminent Indian scientist.
• He studied fossil plants.
• He founded the Birbal Sahni Institute of Palaeosciences in Lucknow.

Contributions

• He helped link present-day plants with their ancestors.
• His studies showed that life on Earth has a long and connected history.
• His work continues to inspire young scientists.

• Every species plays an important role in nature.
• When one species disappears, other species depending on it may also decline.

Roles of Different Organisms

• Plants
• Produce food and oxygen.
• Animals
• Pollinate flowers.
• Disperse seeds.
• Microorganisms
• Recycle nutrients.

Major Threats to Biodiversity

• Pollution
• Deforestation
• Overuse of resources
• Climate change
• Habitat loss

Effects of Biodiversity Loss

• Food chains are disturbed.
• Ecosystem balance is affected.
• Species depending on each other may decline.
• Natural resources become reduced.
• Human life is also affected.

Example: Sangai Deer and Phumdis

• Phumdis are floating grasslands found in Loktak Lake, Manipur.
• They support the Sangai deer.
• Sangai deer is endemic to Manipur.
• Habitat loss of phumdis can seriously affect the Sangai deer population.

Conservation

• Biodiversity conservation is necessary to:
• Protect endangered species.
• Maintain ecological balance.
• Preserve habitats.
• Protect food webs.
• Support human survival.

At a Glance — Summary

• Biodiversity is the variety of life forms present on Earth.
• Life exists in many forms, from simple bacteria to complex animals.
• India is rich in biodiversity because of its varied habitats.
• Species found only in a particular region are called endemic species.
• A biodiversity hotspot is rich in endemic species but faces habitat loss.
• Classification is the scientific grouping of organisms.
• Classification is based on:
• Cell structure
• Number of cells
• Mode of nutrition
• Ecological role
• Reproduction
• Genetic similarity
• The five kingdom classification was proposed by Robert H. Whittaker.
• The five kingdoms are:
• Monera
• Protista
• Fungi
• Plantae
• Animalia
• Monera includes unicellular prokaryotes like bacteria and cyanobacteria.
• Protista includes unicellular eukaryotes like Amoeba, Paramecium and Euglena.
• Fungi includes heterotrophic organisms with chitin cell walls, such as yeast, moulds and mushrooms.
• Plantae includes multicellular autotrophic organisms with cellulose cell walls.
• Kingdom Plantae is divided into:
• Thallophyta
• Bryophyta
• Pteridophyta
• Gymnosperms
• Angiosperms
• Plant evolution shows the gradual development of:
• Vascular tissues
• Seeds
• Flowers
• Fruits
• Animalia includes multicellular heterotrophic eukaryotes.
• Animals are classified on the basis of the presence or absence of a notochord.
• Animals without a notochord are called invertebrates.
• Invertebrate groups include:
• Porifera
• Cnidaria
• Platyhelminthes
• Nematoda
• Annelida
• Arthropoda
• Mollusca
• Echinodermata
• Protochordates have a notochord at least once during life.
• Vertebrates have a backbone.
• Vertebrates include:
• Fish
• Amphibians
• Reptiles
• Birds
• Mammals
• Classification hierarchy is:
• Kingdom → Phylum → Class → Order → Family → Genus → Species
• Scientific naming follows the binomial system.
• Binomial nomenclature was introduced by Carolus Linnaeus.
• Scientific names have two parts:
• Genus
• Species
• Example:
• Tiger: Panthera tigris
• Mango: Mangifera indica
• Fossils are preserved remains of organisms and provide evidence of evolution.
• Birbal Sahni was an Indian scientist who studied fossil plants.
• Biodiversity is threatened by:
• Pollution
• Deforestation
• Overuse of resources
• Climate change
• Habitat loss
• Protecting biodiversity is important for:
• Ecosystem balance
• Food security
• Conservation of species
• Survival of life on Earth.

Important Keywords and Definitions

1. Biodiversity

Biodiversity means the variety of living organisms found on Earth, including plants, animals, fungi, bacteria and other microorganisms.

2. Classification

Classification is the scientific method of grouping organisms on the basis of their similarities, differences and evolutionary relationships.

3. Biological Classification

Biological classification is the systematic grouping of living organisms based on their features, structure, nutrition, reproduction and relationships.

4. Endemic Species

Endemic species are species that are found naturally only in a particular region and nowhere else in the world.

Example: Nilgiri tahr, Lion-tailed macaque, Neelakurinji.

5. Biodiversity Hotspot

A biodiversity hotspot is a region that has a large number of endemic species and has also suffered significant habitat loss.

6. Habitat

Habitat is the natural place where an organism lives.

Example: Forest, pond, desert, ocean.

7. Evolution

Evolution is the gradual change in living organisms over many generations, leading to the development of new forms of life.

8. Adaptation

Adaptation is a special feature or change that helps an organism survive better in its environment.

Example: Thick fur in polar bears, fins and gills in fish.

9. Autotrophic Nutrition

Autotrophic nutrition is a mode of nutrition in which organisms prepare their own food.

Example: Green plants prepare food by photosynthesis.

10. Heterotrophic Nutrition

Heterotrophic nutrition is a mode of nutrition in which organisms depend on other organisms for food.

Example: Animals and fungi.

11. Producer

A producer is an organism that prepares its own food and forms the base of a food chain.

Example: Green plants.

12. Consumer

A consumer is an organism that depends on other organisms for food.

Example: Deer, tiger, human beings.

13. Decomposer

A decomposer is an organism that breaks down dead plants and animals into simpler substances.

Example: Bacteria and fungi.

14. Prokaryote

A prokaryote is an organism whose cell does not have a true, membrane-bound nucleus.

Example: Bacteria.

15. Eukaryote

A eukaryote is an organism whose cell has a true, membrane-bound nucleus.

Example: Amoeba, plants, animals and fungi.

16. Unicellular Organism

A unicellular organism is an organism made up of only one cell.

Example: Amoeba, bacteria, Paramecium.

17. Multicellular Organism

A multicellular organism is an organism made up of many cells.

Example: Plants, animals, mushrooms.

18. Cell Wall

A cell wall is a rigid outer covering present outside the cell membrane in some organisms. It gives support and protection to the cell.

Example: Plant cell wall is made of cellulose.

19. Chitin

Chitin is a tough substance that forms the cell wall of fungi.

20. Cellulose

Cellulose is a substance that forms the cell wall of plant cells.

21. Five Kingdom Classification

Five kingdom classification is a system of classifying living organisms into five major groups.

The five kingdoms are:

• Monera
• Protista
• Fungi
• Plantae
• Animalia

22. Kingdom Monera

Kingdom Monera includes unicellular prokaryotic organisms.

Example: Bacteria and cyanobacteria.

23. Kingdom Protista

Kingdom Protista includes unicellular eukaryotic organisms.

Example: Amoeba, Paramecium, Euglena.

24. Kingdom Fungi

Kingdom Fungi includes mostly multicellular, heterotrophic eukaryotes with a cell wall made of chitin.

Example: Mushroom, yeast, bread mould.

25. Kingdom Plantae

Kingdom Plantae includes multicellular, autotrophic eukaryotes with a cell wall made of cellulose.

Example: Algae, moss, fern, pine, mango tree.

26. Kingdom Animalia

Kingdom Animalia includes multicellular, heterotrophic eukaryotes that usually show movement and quick response to stimuli.

Example: Fish, birds, insects, human beings.

27. Cyanobacteria

Cyanobacteria are unicellular prokaryotic organisms that can perform photosynthesis.

They are also called blue-green algae.

28. Saprophyte

A saprophyte is an organism that obtains nutrition from dead and decaying organic matter.

Example: Many fungi.

29. Parasite

A parasite is an organism that lives in or on another organism and obtains food from it.

Example: Tapeworm.

30. Symbiosis

Symbiosis is a close relationship between two different organisms in which both may benefit.

Example: Lichen is a symbiotic association between an alga and a fungus.

31. Mycelium

Mycelium is a network of fine thread-like structures found in fungi.

32. Spore

A spore is a reproductive structure produced by fungi and some plants. It helps in reproduction and dispersal.

33. Thallophyta

Thallophyta is a group of simple plants whose body is not differentiated into true root, stem and leaves.

Example: Spirogyra.

34. Thallus

A thallus is a simple plant body that is not divided into root, stem and leaves.

35. Bryophyta

Bryophyta is a group of simple land plants that grow in moist places and need water for reproduction.

Example: Moss, Marchantia.

36. Rhizoids

Rhizoids are root-like structures found in bryophytes. They help in attachment and absorption.

37. Pteridophyta

Pteridophyta is a group of plants that have true roots, stems and leaves, and vascular tissues, but do not produce seeds.

Example: Fern.

38. Vascular Tissue

Vascular tissue is a transport tissue in plants that carries water, minerals and food.

It includes:

• Xylem
• Phloem

39. Xylem

Xylem is a vascular tissue that transports water and minerals from roots to other parts of the plant.

40. Phloem

Phloem is a vascular tissue that transports food from leaves to other parts of the plant.

41. Gymnosperms

Gymnosperms are seed-producing plants in which seeds are not enclosed inside fruits.

Example: Pine, Cycas.

42. Naked Seeds

Naked seeds are seeds that are not enclosed inside fruits.

They are found in gymnosperms.

43. Cone

A cone is a reproductive structure found in gymnosperms where seeds are often present.

Example: Pine cone.

44. Angiosperms

Angiosperms are flowering plants that produce seeds enclosed inside fruits.

Example: Mango, rose, pea, grass.

45. Pollination

Pollination is the transfer of pollen grains from the anther to the stigma of a flower.

46. Seed Dispersal

Seed dispersal is the spreading of seeds away from the parent plant.

Seeds may be dispersed by:

• Wind
• Water
• Animals
• Birds
• Insects

47. Notochord

A notochord is a flexible rod-like structure that provides internal support to the body in chordates.

48. Non-chordata

Non-chordata are animals that do not have a notochord.

They are also called invertebrates.

49. Invertebrates

Invertebrates are animals that do not have a backbone or notochord.

Example: Sponge, Hydra, earthworm, insects.

50. Chordata

Chordata is a group of animals that have a notochord at least once during their life.

51. Protochordates

Protochordates are primitive chordates that have a notochord at least once during their life.

Example: Amphioxus.

52. Vertebrates

Vertebrates are animals that have a backbone or vertebral column.

Example: Fish, frog, snake, bird, human being.

53. Vertebral Column

The vertebral column, also called the backbone, is an internal skeletal structure that supports the body and protects the spinal cord.

54. Porifera

Porifera is a group of simple aquatic animals with many pores on their body.

Example: Sponge.

55. Cnidaria

Cnidaria is a group of aquatic animals with tissue-level organisation and tentacles for capturing prey.

Example: Hydra, jellyfish, corals.

56. Tentacles

Tentacles are long, flexible structures used by some animals to capture food.

Example: Hydra uses tentacles to catch prey.

57. Platyhelminthes

Platyhelminthes are flatworms with bilateral symmetry.

Example: Tapeworm.

58. Bilateral Symmetry

Bilateral symmetry means the body of an organism can be divided into two equal halves along one plane.

59. Nematoda

Nematoda is a group of roundworms with cylindrical bodies and two openings, mouth and anus.

Example: Roundworm.

60. Annelida

Annelida is a group of segmented worms with organ system level organisation.

Example: Earthworm.

61. Segmentation

Segmentation means division of the body into repeated sections or segments.

62. Arthropoda

Arthropoda is a group of animals with jointed appendages and a hard external skeleton.

Example: Insects, crabs, spiders.

63. Exoskeleton

An exoskeleton is a hard external skeleton that protects the body and reduces water loss.

Example: Beetle’s hard outer covering.

64. Mollusca

Mollusca is a group of soft-bodied animals, many of which have a protective shell.

Example: Snail, squid, octopus.

65. Echinodermata

Echinodermata is a group of marine animals with a hard internal skeleton made of calcium carbonate.

Example: Starfish, sea urchin.

66. Endoskeleton

An endoskeleton is an internal skeleton present inside the body.

Example: Skeleton of vertebrates and echinoderms.

67. Binomial Nomenclature

Binomial nomenclature is the scientific system of naming organisms using two words: genus and species.

Example: Panthera tigris.

68. Genus

A genus is a group of closely related species that share common features.

Example: Panthera includes tiger and lion.

69. Species

A species is a group of similar organisms that can interbreed and produce offspring.

70. Scientific Name

A scientific name is a universal name given to an organism using the binomial system.

Example: The scientific name of tiger is Panthera tigris.

71. Hierarchy of Classification

The hierarchy of classification is the step-by-step arrangement of organisms from broad groups to specific groups.

The order is:

• Kingdom
• Phylum
• Class
• Order
• Family
• Genus
• Species

72. Fossil

A fossil is the preserved remain or trace of an ancient plant or animal found in rocks, sand or mud.

73. Fossil Evidence

Fossil evidence refers to information obtained from fossils that helps scientists understand how life changed over time.

74. Three Domain System

The three domain system is a modern classification system based mainly on genetic differences.

The three domains are:

• Bacteria
• Archaea
• Eukarya

75. DNA

DNA is the genetic material present in living cells. It carries instructions for growth, development and functioning.

76. Common Ancestry

Common ancestry means that different organisms have evolved from a shared ancestor.

77. Conservation

Conservation means protecting and preserving natural resources, organisms and habitats.

78. Habitat Loss

Habitat loss means destruction or reduction of the natural home of an organism.

79. Climate Change

Climate change means long-term changes in temperature, rainfall and weather patterns, which can affect biodiversity.

80. IUCN Red Data List

The IUCN Red Data List is a list that gives information about species that are threatened or at risk of extinction.

Quick Revision Keywords

• Biodiversity – variety of life
• Classification – grouping of organisms
• Endemic species – found only in one region
• Hotspot – rich biodiversity area under threat
• Monera – unicellular prokaryotes
• Protista – unicellular eukaryotes
• Fungi – chitin cell wall, heterotrophic
• Plantae – autotrophic, cellulose cell wall
• Animalia – multicellular heterotrophs
• Notochord – flexible support rod
• Vertebrates – animals with backbone
• Binomial nomenclature – two-word scientific naming
• Fossils – preserved remains of ancient life
• Conservation – protection of biodiversity