Explanation:

The earliest attempt to classify organisms was made by Aristotle, a Greek philosopher and scientist, who lived from 384-322 BC. Aristotle classified organisms on the basis of their habitat, size, and structure. He classified organisms into two groups: plants and animals. He further divided animals into those with blood (vertebrates) and those without blood (invertebrates). This classification system was not based on any scientific principles but was more based on observation and common sense.

Aristotle's classification system was widely accepted until the 18th century when Carl Linnaeus introduced a more scientific basis for classification. Linnaeus developed a hierarchical system of classification based on the morphological characteristics of organisms. He classified organisms based on their physical characteristics and grouped them into categories that reflected their relatedness.

Linnaeus' classification system was widely accepted and used for many years until the development of molecular biology and genetics. Today, classification is based on evolutionary relationships and is often referred to as phylogenetics.

Key Points:
- Aristotle made the earliest attempt to classify organisms.
- His classification system was based on observation and common sense.
- Aristotle classified organisms into two groups: plants and animals.
- Carl Linnaeus introduced a more scientific basis for classification.
- Linnaeus' classification system was based on the morphological characteristics of organisms.
- Today, classification is based on evolutionary relationships and is often referred to as phylogenetics.