Biodiversity, endemic species and hotspots
Near a village there are two patches of land: one is a mixed forest with hundreds of kinds of trees, insects and birds, and the other is a farm of a single crop. After a pest attack, the forest still stands, but the farm is bare.
Biodiversity is the variety of living organisms on the Earth. A species found naturally only in one region is endemic (Nilgiri tahr, lion-tailed macaque). A region with many endemic species and heavy habitat loss is a biodiversity hotspot (Western Ghats, Himalayas). Today's diversity arose as small differences gave survival advantages over many generations; fossils are the record of this change.
In the figure : Endemic species + habitat loss = hotspot.
Rule 1: Endemic species plus habitat loss make a hotspot — Both conditions must hold: many species found nowhere else and serious loss of habitat.
- Easy : The Western Ghats has many endemic species and has lost much forest.
- Medium : A big forest with no endemic species and no loss is not a hotspot.
- Exam-type : Losing one hotspot habitat can erase species that live nowhere else.
Rule 2: More diversity means more stability — Different species do different jobs, so the ecosystem and farms are safer when many kinds exist.
- Easy : Farmers keep varieties that resist drought, pests or poor soil.
- Medium : Algae give oxygen, fungi recycle waste, bees and bats pollinate.
- Exam-type : Mangrove forests reduce damage from cyclones.
When one species disappears, the species that depend on it may also decline.
Thinking that every rare species is endemic, or that fossils are living organisms.
Memory clue: E-H-F — Endemic, Hotspot, Fossil. Many kinds = safe system.
Spot the difference
| Term | Meaning | Example |
|---|---|---|
| Endemic species | Found naturally only in one region | Nilgiri tahr |
| Hotspot | Many endemic species and heavy habitat loss | Western Ghats |
| Fossil | Preserved remains in rocks | Fossil plants |
Practice questions
- 1What is biodiversity?
- 2What is an endemic species?
- 3What does a fossil tell us?
- 4Why do farmers keep many crop varieties?
- 5Why are hotspots important for conservation?
- 6How do mangroves help during a cyclone?
- 7A region has 800 plant species and 200 are endemic. What percent are endemic?
- 8A farmer grows 5 varieties and a pest kills 2 of them. What fraction of the varieties survive?
Show answers (try them yourself first)
- 1The variety of living organisms on the Earth.
- 2A species found naturally only in one region.
- 3How life has changed over time; older layers have simpler organisms.
- 4Diversity reduces the risk of crop failure.
- 5They hold many endemic species that are losing habitat.
- 6They act as a protective barrier and reduce destruction.
- 7200 ÷ 800 × 100 = 25 percent.
- 83 of 5, that is 3/5.
Why and how we classify organisms
A teacher puts twenty shoes on a table and asks the class to sort them. One child sorts by colour, another by size, a third by the type of use. Each gets a different but correct grouping.
Biological classification is the scientific grouping of organisms by shared features. Criteria include external features, mode of nutrition (autotroph or heterotroph), internal structure, cell structure (prokaryote or eukaryote, cell wall), level of organisation, ecological role, reproduction and DNA. Classification makes study orderly, helps name new organisms and supports conservation.
In the figure : The criterion decides the group.
Rule 1: Change the criterion, change the group — One organism can sit in different groups depending on what you choose to compare.
- Easy : An eagle is a carnivore by food and a flying animal by habit.
- Medium : A tiger is a carnivore by food and a mammal by body features.
- Exam-type : Amoeba and a human differ by level of organisation, not by having cells.
Rule 2: Go from broad to detailed features — Start with easily visible features, then use cell structure, internal parts and DNA.
- Easy : First ask: plant-like or animal-like?
- Medium : Then ask: does it have a true nucleus and a cell wall?
- Exam-type : Finally compare DNA to see common ancestry.
Similar features often point to a common ancestor, so classification also shows relationships.
Using only one feature, such as colour or habitat, which may group unrelated organisms together.
Memory clue: N-C-L-E-R-D — Nutrition, Cell type, Level of organisation, Ecological role, Reproduction, DNA. Many features, not one.
Spot the difference
| Criterion | Question asked | Example |
|---|---|---|
| Nutrition | Does it make its own food? | Plant vs animal |
| Cell type | Does it have a true nucleus? | Bacterium vs amoeba |
| Level of organisation | One cell or many? | Amoeba vs human |
Practice questions
- 1Name the two modes of nutrition.
- 2What does a eukaryote have that a prokaryote lacks?
- 3Give one benefit of classification.
- 4Why can the same organism fit in more than one group?
- 5Why do scientists use many features instead of one?
- 6How can classification help conservation?
- 7A student sorts 20 animals into carnivores and herbivores and finds 8 carnivores. How many are herbivores?
- 8Of 30 organisms, 18 are heterotrophs and the rest are autotrophs. What fraction are autotrophs?
Show answers (try them yourself first)
- 1Autotrophic and heterotrophic.
- 2A true, membrane-bound nucleus.
- 3It helps identify and name newly discovered organisms.
- 4Because the grouping depends on the criterion chosen.
- 5One feature alone could put unrelated organisms together.
- 6It identifies organisms that are threatened with extinction.
- 720 − 8 = 12 herbivores.
- 830 − 18 = 12 autotrophs, 12/30 = 2/5.
Classification systems over time and the five kingdoms
A new student's school bag has books of many subjects. At first she thinks of two piles, then notices a few books fit neither, so she makes a third pile, and later more. Biologists did the same with living things.
Aristotle grouped animals by habitat. In the 18th century Linnaeus proposed two kingdoms (Plantae, Animalia). Haeckel added Protista, Copeland added Monera, and Whittaker added Fungi to make the five kingdoms. The five kingdom system uses cell type, cell wall, level of organisation and mode of nutrition. Carl Woese later proposed three domains from DNA data: Bacteria, Archaea and Eukarya.
In the figure : Systems grew as knowledge grew.
Rule 1: Each new system fixed a problem of the old one — Misfit organisms led to new kingdoms.
- Easy : Amoeba moves like an animal but is unicellular, so Protista was added.
- Medium : Bacteria have no true nucleus, so Monera was added.
- Exam-type : Mushrooms absorb food but do not move, so Fungi was added.
Rule 2: Use four criteria to place a kingdom — Cell type, cell wall, level of organisation and mode of nutrition decide the kingdom.
- Easy : Prokaryote, unicellular: Monera.
- Medium : Eukaryote, chitin wall, heterotroph: Fungi.
- Exam-type : Eukaryote, cellulose wall, autotroph: Plantae.
Viruses have no cellular organisation, so they do not fit any of the five kingdoms.
Thinking that the five kingdom system is final, or that colour is a main criterion.
Memory clue: Two, Three, Four, Five — add Protista, Monera, Fungi (P-M-F).
Spot the difference
| Kingdom | Cell type | Nutrition |
|---|---|---|
| Monera | Prokaryote | Autotrophic or heterotrophic |
| Fungi | Eukaryote | Heterotrophic (absorb) |
| Plantae | Eukaryote | Autotrophic |
Practice questions
- 1Who proposed the five kingdom system?
- 2Which kingdom was added in the three kingdom system?
- 3Who proposed the three domains?
- 4Why were bacteria placed in a separate kingdom?
- 5Why were fungi separated from plants?
- 6Why do classification systems keep changing?
- 7How many kingdoms were added in going from the two kingdom to the five kingdom system?
- 8The two kingdom system dates from 1758 and the five kingdom system from 1969. How many years passed?
Show answers (try them yourself first)
- 1R. H. Whittaker.
- 2Protista.
- 3Carl Woese.
- 4They have no true nucleus.
- 5They do not make their own food and absorb nutrients.
- 6New tools and knowledge reveal new facts.
- 75 − 2 = 3 kingdoms.
- 81969 − 1758 = 211 years.
Monera, Protista and Fungi
Bread that is left in a damp box grows green fuzz, a pond drop shows tiny swimmers, and a pinch of curd makes more curd. These very different things belong to three small kingdoms.
Monera are unicellular prokaryotes (bacteria, cyanobacteria): some cause disease, many are useful (Lactobacillus, Rhizobium) and some make biogas. Protista are unicellular eukaryotes (Amoeba, Paramecium, Euglena) found in water. Fungi are mostly multicellular eukaryotes with chitin cell walls that absorb food through a mycelium; yeast is unicellular but still a fungus.
In the figure : Nucleus and cell wall separate the three kingdoms.
Rule 1: Check the nucleus first — No true nucleus means Monera; a true nucleus and one cell means Protista.
- Easy : A slide of bacteria shows no membrane-bound nucleus.
- Medium : A pond organism with a nucleus and cilia is a protist.
- Exam-type : Cyanobacteria are blue-green algae but still prokaryotes.
Rule 2: Fungi absorb food and decompose — Heterotrophs with chitin walls that live on dead matter are fungi.
- Easy : Mushrooms grow on decaying logs.
- Medium : Aspergillus and Penicillium give enzymes and antibiotics.
- Exam-type : Yeast is placed in fungi because its wall is chitin.
Many fungi are saprophytes and decomposers, so soil fertility and recycling depend on them.
Calling yeast a protist because it is unicellular, or calling cyanobacteria plants.
Memory clue: Monera = No nucleus, Protista = Pond, one cell, Fungi = Filaments, chitin.
Spot the difference
| Kingdom | Cell | Example |
|---|---|---|
| Monera | Unicellular, no true nucleus | Bacteria, cyanobacteria |
| Protista | Unicellular, true nucleus | Amoeba, Euglena |
| Fungi | Mostly multicellular, chitin wall | Mushroom, Aspergillus |
Practice questions
- 1Name the kingdom of bacteria.
- 2What is a mycelium?
- 3Which two fungi are used for antibiotics and enzymes?
- 4Why is yeast classified as a fungus?
- 5Why are fungi called decomposers?
- 6Why are protists important in water?
- 7Mushroom cultivation takes 40 days per crop. How many crops can be grown in 200 days?
- 8A bacterium divides into two every 20 minutes. How many bacteria after 1 hour starting from one?
Show answers (try them yourself first)
- 1Monera.
- 2A network of fine filaments of a fungus.
- 3Aspergillus and Penicillium.
- 4Its cell wall is made of chitin.
- 5They feed on dead matter and recycle nutrients.
- 6They are a link in food chains and some make oxygen.
- 7200 ÷ 40 = 5 crops.
- 81 → 2 → 4 → 8, so 8 bacteria.
Kingdom Plantae and its five classes
On a hill walk, you see algae in a pond, moss on a wall, a fern in the shade, a pine tree with cones and a mango tree with fruits. Each shows a step in plants adapting to life on land.
Plantae are multicellular autotrophs with cellulose walls, divided into five classes. Thallophyta (algae) have a simple thallus. Bryophyta (moss) grow on moist land and need water to reproduce. Pteridophyta (ferns) have true roots, stems, leaves and vascular tissue but no seeds. Gymnosperms (pine) bear naked seeds on cones. Angiosperms bear flowers and seeds in fruits.
In the figure : Each group adds a new survival feature.
Rule 1: Each group solves a land problem — Water need falls and transport, seeds and flowers appear step by step.
- Easy : Bryophytes: first step on land but they still need moisture.
- Medium : Pteridophytes: vascular tissue carries water and food.
- Exam-type : Gymnosperms and angiosperms: seeds free them from water for reproduction.
Rule 2: Identify the group by its key feature — Look for thallus, no vascular tissue, vascular tissue without seeds, naked seeds, or fruits.
- Easy : No vascular tissue, small, needs water: Bryophyta.
- Medium : Vascular tissue but no seeds: Pteridophyta.
- Exam-type : Seeds inside fruits: Angiosperm.
Lichens are a partnership of an alga and a fungus and are bioindicators of clean air.
Thinking that ferns produce seeds, or that gymnosperm seeds are inside fruits.
Memory clue: T-B-P-G-A — Thallus, Bryo, Ptrido, Gymno, Angio: simple to complex.
Spot the difference
| Group | Key feature | Example |
|---|---|---|
| Bryophyta | No vascular tissue; needs water | Moss |
| Pteridophyta | Vascular tissue; no seeds | Fern |
| Gymnosperm | Naked seeds on cones | Pine |
Practice questions
- 1Name the five classes of Plantae.
- 2What are xylem and phloem?
- 3Which group bears flowers and fruits?
- 4Why are bryophytes called the amphibians of the plant kingdom?
- 5Why are the leaves of gymnosperms needle-like?
- 6Why are angiosperms the most diverse plant group?
- 7Among 40 plants, 6 are bryophytes, 8 pteridophytes, 10 gymnosperms and the rest angiosperms. How many angiosperms?
- 8In the same group of 40, what fraction bears seeds?
Show answers (try them yourself first)
- 1Thallophyta, Bryophyta, Pteridophyta, Gymnosperm and Angiosperm.
- 2Vascular tissues carrying water and food.
- 3Angiosperms.
- 4They need water for reproduction.
- 5To reduce loss of water.
- 6Flowers attract pollinators and fruits spread seeds.
- 740 − (6 + 8 + 10) = 16 angiosperms.
- 8(10 + 16) ÷ 40 = 26/40 = 13/20.
Invertebrates: Porifera to Echinodermata
A rock-pool visitor lifts a sponge, a sea anemone, a snail and a starfish. All four have no backbone, yet they are built very differently.
Invertebrates lack a notochord. Porifera (sponges) are cellular with pores. Cnidaria (hydra, jellyfish) have tissues and tentacles with one opening. Platyhelminthes (flatworms) have bilateral symmetry. Nematoda (roundworms) have two openings. Annelida (earthworm) are segmented. Arthropoda have jointed legs and an exoskeleton. Mollusca are soft-bodied, often with a shell. Echinodermata (starfish) have a calcium carbonate internal skeleton.
In the figure : Body organisation rises from cells to organ systems.
Rule 1: Complexity of organisation increases — Cellular, then tissue, then organ, then organ system.
- Easy : Sponge: cellular level, no true tissues.
- Medium : Hydra: tissue level with tentacles.
- Exam-type : Earthworm: organ system level with segments.
Rule 2: Pick the identifying feature — Pores, tentacles, flat body, two openings, segments, jointed legs, shell, or spiny skin point to the phylum.
- Easy : Jointed legs and an outer skeleton: Arthropoda.
- Medium : Soft body with a shell: Mollusca.
- Exam-type : Spiny skin and internal calcium skeleton: Echinodermata.
Hygiene, cooked food and boiled water protect us from parasitic worms.
Saying all worms are the same phylum, or that starfish have an exoskeleton.
Memory clue: P-C-P-N-A-A-M-E — Porifera, Cnidaria, Platyhelminthes, Nematoda, Annelida, Arthropoda, Mollusca, Echinodermata.
Spot the difference
| Phylum | Key feature | Example |
|---|---|---|
| Porifera | Pores, cellular level | Sponge |
| Annelida | Segmented body | Earthworm |
| Arthropoda | Jointed legs, exoskeleton | Insect, crab |
Practice questions
- 1Which phylum has pores in the body?
- 2Which phylum has jointed appendages?
- 3What is the internal skeleton of echinoderms made of?
- 4Why do cnidarians catch prey better than sponges?
- 5Why do roundworms with two openings have an advantage?
- 6How does an exoskeleton help arthropods?
- 7A collection has 12 sponges, 9 jellyfish, 14 earthworms and 25 insects. How many invertebrates in all?
- 8What fraction of the collection is arthropods?
Show answers (try them yourself first)
- 1Porifera.
- 2Arthropoda.
- 3Calcium carbonate.
- 4They have tentacles and do not depend on water currents.
- 5Food moves in one direction through mouth and anus.
- 6It protects, reduces water loss and supports muscles.
- 712 + 9 + 14 + 25 = 60.
- 825/60 = 5/12.
Chordates, vertebrates and adaptations
A zoo guide shows a fish, a frog, a lizard, a crow and a cow, and asks what they share. The answer is hidden inside the body: a backbone developed from a notochord.
Chordates have a notochord. Protochordates (Amphioxus) have it at some stage of life. Vertebrates have a backbone that protects the spinal cord and are grouped as fish, amphibians, reptiles, birds and mammals by habitat use, body covering and reproduction. Adaptations such as fins and gills, feathers and hollow bones, thick fur and mammary glands arose through structural change over long periods.
In the figure : Notochord first, backbone next.
Rule 1: The notochord is the key criterion — Without a notochord: non-chordata. With a notochord: chordata, then protochordata or vertebrata.
- Easy : Earthworm and starfish lack a notochord.
- Medium : Amphioxus has a notochord but no backbone.
- Exam-type : Frog, crow and cow have a backbone.
Rule 2: Match the feature to the group — Body structure suits the environment.
- Easy : Gills and fins suit fish in water.
- Medium : Feathers and hollow bones suit birds in flight.
- Exam-type : Mammary glands give mammals milk for the young.
Adaptations are outcomes of structural change over long periods, not sudden changes.
Believing that every animal with a hard skeleton is a vertebrate.
Memory clue: FARBM — Fish, Amphibians, Reptiles, Birds, Mammals.
Spot the difference
| Group | Key body feature | Example |
|---|---|---|
| Fish | Gills and fins | Carp |
| Birds | Feathers, hollow bones | Crow |
| Mammals | Mammary glands | Human |
Practice questions
- 1What is a notochord?
- 2Name the five groups of vertebrates.
- 3What is a protochordate?
- 4Why does a starfish belong to non-chordata?
- 5How do fins and gills help fish?
- 6What do mammary glands do?
- 7A park survey finds 30 birds, 20 mammals and 10 fish. What percent are birds?
- 8In a pond with 50 animals, 20 percent are vertebrates. How many are vertebrates?
Show answers (try them yourself first)
- 1A flexible rod-shaped structure that gives internal support.
- 2Fish, amphibians, reptiles, birds and mammals.
- 3A chordate that has a notochord at some stage but no backbone.
- 4It lacks a notochord.
- 5They allow movement and breathing in water.
- 6They feed milk to the young.
- 730 ÷ 60 × 100 = 50 percent.
- 850 × 20 ÷ 100 = 10 vertebrates.
Hierarchy of classification and binomial nomenclature
A tiger is called bagh, puli or tigre in different places, and confusion follows when scientists in different countries talk about it. To avoid this, every organism gets one two-part Latin name.
Classification is hierarchical: Kingdom, Phylum, Class, Order, Family, Genus, Species. Each lower group shares more features and belongs to the group above it. Binomial nomenclature, introduced by Linnaeus, gives each organism a scientific name with a genus (capital letter) and a species (small letters), italicised in print and underlined in handwriting.
In the figure : Broad to specific, like an address.
Rule 1: Seven levels from broad to specific — Kingdom, Phylum, Class, Order, Family, Genus, Species.
- Easy : The tiger is in Mammalia (class) and Felidae (family).
- Medium : A genus has fewer members than a class but more shared features.
- Exam-type : Two organisms in the same family are also in the same order and class.
Rule 2: Write the scientific name correctly — Genus first with a capital, species next in small letters, italics or underlined.
- Easy : Panthera tigris is the tiger, and Panthera leo is the lion.
- Medium : Mangifera indica is the mango.
- Exam-type : Pisum sativum is the pea.
The species name alone is not enough; the genus and species together make the unique name.
Writing both words with capital letters, or writing the species first.
Memory clue: K-P-C-O-F-G-S — King Philip Came Over For Good Soup.
Spot the difference
| Level | Tiger | Pea |
|---|---|---|
| Family | Felidae | Fabaceae |
| Genus | Panthera | Pisum |
| Species | P. tigris | P. sativum |
Practice questions
- 1Who introduced binomial nomenclature?
- 2Which is the broadest level in the hierarchy?
- 3In which language are scientific names written?
- 4Why do we need universal scientific names?
- 5What is a species?
- 6How should a printed scientific name be written?
- 7The hierarchy has 7 levels. How many levels are above the family?
- 8A student writes the scientific names of 6 organisms. How many words are written in all?
Show answers (try them yourself first)
- 1Carolus Linnaeus.
- 2Kingdom.
- 3Latin or a Latinised form.
- 4Local names differ and cause confusion.
- 5A group of similar individuals that can interbreed and produce offspring.
- 6In italics, with the genus in a capital letter and the species in small letters.
- 74 levels (kingdom, phylum, class, order).
- 86 × 2 = 12 words.