Class 9 BiologyChapter 12NCERT 12.7, 12.7.1 and 12.8
Adaptations, the hierarchy of classification and binomial names
Every organism has an address, and a two word name the whole world shares.
Think it over
- Your home has an address: country, state, city, street, house number. What would an address for a tiger look like?
- A tiger is bagh in Hindi and puli in Tamil. How would scientists in Brazil and Japan know they mean the same animal?
- A cat and a tiger share a family; a tiger and a cow share only a class. Which pair has more in common, and why?
In one minute
- Body features are outcomes of long change: fins and gills for water, feathers and hollow bones for flight, stored fat in camels, thick fur in polar bears, milk glands in mammals.
- Classification is hierarchical: Kingdom, Phylum, Class, Order, Family, Genus, Species. Like boxes inside boxes: the smaller the box, the fewer its members and the more they have in common.
- Binomial nomenclature, introduced by Carolus Linnaeus, gives each organism a two part Latin or Latinised name: genus then species, as in Panthera tigris.
- Genus starts with a capital, species is all small letters, and the name is italic in print or underlined by hand.
Adaptations as outcomes of structural change
Animal bodies today are the result of changes in structure over very long periods. Each feature is a solution to a survival problem in a particular place. Match them up.
Structure meets survival
0 of 5 matched
Tap a feature on the left, then the problem it solves.
A fish is not fins plus gills plus scales bolted together: the parts work as a team for life in water, and a bird's feathers, light bones and strong chest muscles work as a team for the air. That is why the animal world looks so varied. Every habitat on the Earth asks different questions, and each vertebrate body is one set of answers.
Quick check
Hollow bones in birds are best explained as an adaptation for:
Show the answer
B. Flight Light bones filled with air spaces, together with feathers, let birds get airborne.
The hierarchical nature of classification
Classification runs in steps, from very broad groups to small, precise ones: Kingdom, Phylum, Class, Order, Family, Genus, Species. Every group is part of the group above it, and the lower you go, the more features the members share. Step down the pyramid and watch the crowd shrink.
Zoom down the hierarchy
Kingdom Animalia
| Kingdom | Animalia | Many cells, no cell walls, eat other organisms. |
|---|---|---|
| Phylum | Chordata | A notochord at some stage of life. |
| Sub-phylum | Vertebrata | A backbone around the spinal cord. |
| Class | Mammalia | Mammary glands feed the young; hair or fur. |
| Order | Carnivora | Flesh eaters with teeth for tearing. |
| Family | Felidae | The cat family. |
| Genus | Panthera | The roaring cats, with a similar skull: tiger, lion and others. |
| Species | P. tigris | Tigers only: they interbreed and have young tigers. |
| Kingdom | Plantae | Many cells, cellulose walls, make their own food. |
|---|---|---|
| Phylum | Magnoliophyta | Flowering plants: seeds enclosed in fruits. |
| Class | Magnoliopsida | Flowering plants with two seed leaves (dicots). |
| Order | Fabales | An order of dicots that includes the bean family. |
| Family | Fabaceae | The bean family: pods of seeds. Gulmohar is one too. |
| Genus | Pisum | Pea plants. |
| Species | P. sativum | The garden pea. |
| Kingdom | Plantae | Many cells, cellulose walls, make their own food. |
|---|---|---|
| Phylum | Magnoliophyta | Flowering plants: seeds enclosed in fruits. |
| Class | Magnoliopsida | Dicots: two seed leaves, net-veined leaves. |
| Order | Sapindales | An order that also holds neem and citrus. |
| Family | Anacardiaceae | The cashew family: mango and cashew. |
| Genus | Mangifera | Mango trees. |
| Species | M. indica | The common mango, named after India. |
* Mango is our extra example, not in the book. You may also meet
It works like a postal address. "India, Kerala, Kochi, MG Road, house 12" finds one house among millions; "Animalia, Chordata, Mammalia, Carnivora, Felidae, Panthera, tigris" finds one species among millions. Give a biologist the address and they know exactly which organism you mean, what it can be compared with, and who its nearest relatives are.
Quick check
Members of which level share the most features with each other?
Show the answer
D. Species The lower the level, the more features members share. Species is the lowest level.
Scientific naming: the binomial system
Local names change from language to language: the same tiger is bagh, puli, tiger and tigre. So biologists everywhere use one naming scheme, binomial nomenclature, which Carolus Linnaeus brought in during the 1700s. Each kind of organism is given a name of two words, in Latin or made to look Latin.
In Panthera tigris (tiger) and Mangifera indica (mango), the first word is the genus and the second is the species. A genus gathers closely related species: Panthera tigris and Panthera leo, the lion, are both roaring cats with similar skulls. A species is a group of similar individuals that can interbreed and have offspring. Genus plus species gives a name that means one organism everywhere.
Name builder
Genus first, species second.
1 Genus
2 Species
- Panthera tigris: Tiger
- Panthera leo: Lion
- Mangifera indica: Mango
- Pisum sativum: Garden pea
- Nasikabatrachus sahyadrensis: Purple frog
3 Spot the mistake
- panthera tigris Write it as Panthera tigris. The genus always starts with a capital letter. Rule broken: Genus needs a capital. Panthera tigris. The genus always starts with a capital letter.
- Mangifera Indica Write it as Mangifera indica. The species part is written all in small letters, even when it comes from a place name. Rule broken: Species in small letters. Mangifera indica. The species part is written all in small letters, even when it comes from a place name.
- leo Panthera Write it as Panthera leo. Genus first, then species. Rule broken: Genus comes first. Panthera leo. Genus first, then species.
- Pisum sativum Write it as Pisum sativum. In print the name is in italics; by hand you underline it. Rule broken: Italics or underline. Pisum sativum. In print the name is in italics; by hand you underline it.
The rules in short: two parts, genus then species; the genus starts with a capital and the species is in small letters; the whole name is in italics in print, or underlined when handwritten.
Five kingdoms were a big step forward, but they still did not capture everything. Once scientists could compare organisms by their DNA, a further idea arrived: Ready to go beyond.
Three domains of life
Carl Woese, 1977, from comparing DNA
- Bacteria
Most of the old Monera: bacteria and cyanobacteria.
- Archaea
Also prokaryotes, but their DNA is very different from bacteria. Many live in extreme places.
- Eukarya
Every organism with a true nucleus: Protista, Fungi, Plantae and Animalia.
Next level up: you meet domains properly in higher classes. For Class 9, the five kingdoms are the system to learn. You may also meet
- Genus
- A group of closely related species that share common features.
- Species
- A group of similar individuals that can interbreed and produce offspring.
- Binomial nomenclature
- Naming each organism with two words, genus and species.
Quick check
Which is written correctly in print?
Show the answer
B. Panthera leo Genus first with a capital letter, species in small letters, the whole name in italics.