Linnaeus considered a few characters of organisms for classifying them. Later many characters were considered for classifying organisms. Morphological, anatomical, embryological characters were considered.

Many organisms were not fitting into his classification. Frogs have lungs and they are amphibians while their larva, tadpole is aquatic and respires through gills. It is difficult to classify frogs according to his method. All flying organisms such as birds, bats, flying insects were grouped together. Ostrich, emu and penguin are flightless birds and hence they cannot be classified by his method.

Aristotle classified living organisms into plants and animals. Animals were classified into walking (terrestrial), flying (birds) and swimming {aquatic) based on their locomotion. Based on the presence or absence of red blood animals were classified into Enaima and Anaima.

Kingdom Monera includes bacteria which are prokaryotic organisms lacking a nuclear membrane.

There are many organisms like the Mules, worker bees etc. which are sterile but they show the characteristics of living organism. Hence, Reproduction cannot be considered as a character to define living organisms

Reasons for reduction in Population of sparrows:
1. Absence of native plants which provide habitats (shelter, insects as food etc.)
2. Grocery stores being replaced with Supermarkets (gunny bags were pecked by sparrows for grains earlier.)
3. Cell phone radiation from Towers. Sparrow population is disappearing. fast. Thus it is important to conserve sparrows which is becoming endangered because every animal is an important link is an ecosystem.

1. Purple pig-nosed Frog was discovered in the Western Ghats.
2. It has shiny purple skin and spends its entire adult life underground.
3. It is called Bhupathy's purple frog by the scientists in memory of Subramaniam Bhupathy a respectable herpetologist who lost his life is the Western Ghats.

Prokaryotes which have the ability to grow in extreme conditions like volcano vents, hot springs and polar ice caps are called extremophiles. They have adaptations such as :
1. Capacity to synthesize their food without sunlight and oxygen by utilizing hydrogen sulphide and other chemicals from the volcanic vents.
2. Some of them produce methane (Methanogens).
3. Some live in salty environments (Halophiles).
4. Some are thermoacidophiles which thrive in acidic environments and at high temperature.

1. The main criteria of systematics is identifying, describing, naming, arranging, preserving and documenting the organisms.
2. Evolutionary history of the species and the environmental adaptations and interrelationship between species are also being investigated in systematics

(i) This family consists of more than one species in the genus it is known as polytypic genus.
(ii) Species are intrageneric
(iii) A single genus is Felis which has a number of closely related species.
(iv) Different species of a single genus show the same morphological characteristics but their behavior varies
(v) Eg: Felis domestica (Domestic cat)
Felis margarita (Jungle cat)
Felis silvestris (Wild cat)