Which organisms are called primitive and how are they different from the so-called advanced organisms?

The organisms which have ancient body design that that have not changed much over the course of time, are known as primitive or lower organism.

Advanced organisms are those who have accumulated changes and acquired their particular body designs relatively recently.

The difference between the two are : 

1. Primitive organisms have simpler body design where as advanced or younger organisms have complex body design.

 These are differences between amphibians and reptiles:

Major divisions in kingdom plantae are—

(i) Thallophyta
(ii) Bryophyta
(iii) Pteridophyta
(iv) Gymnosperms
(v) Angiosperms.

Basis for classification plantae division :

1. Whether the plant body has well differentiated, distinct components is the basis for the first level of classification. 

2. Whether the differentiated plant body has special tissues for the transport of water and other substances within it forms the basis for the second level of classification.

3. Whether the plants bear the seeds forms the next level of classification.

4. Whether the seeds are enclosed within fruits.

Classification is advantageous in the following way:

(i) Classification makes the study of huge varieties of organisms easy.

(ii)  It helps us to understand the interrelationship among different groups of organisms.

(iii) It helps in the specific identification of any given organism.

(iv) The study of a few representatives from each distinct group helps us to integrate the idea of life as a whole.

(v) It reveals the relationships among various groups of organisms.

(vi) It provides information about plants and animals, which occur in specific geographical regions.

(vii) It indicates the evolutionary relationship by establishing the gradually increasing complexity of form and structure in different groups of organisms.