Zoology Blog by Dr Rahul Kait

   Host parasite relationship is a strange inter-specific association where one organism called as parasite is benefitted and the other organism called as host is harmed, where host always wants to get rid of the parasite whereas the parasite never wants to leave the host.  There are various degrees of interdependence of parasites on the host, which depend on the nature of  parasite and the degrees of parasitism i.e. an obligatory parasite depends on the host all throughout life  where as facultative parasites depend on host for a particular stage of life cycle.  Among obligate parasites the degree of interdependence on the host also varies for example Staphylococci and Streptococci are obligatory parasites but they can reproduce in ex-situ environment i.e. outside the body of the host in nutrient media whereas Rickettsia, which have structure akin to bacteria show a small degree of metabolic activities outside the body of host but they can’t grow whereas t...

We find in nature that different organisms are linked to each other through various ways, such as through the food chain or food web, through sharing of the common resources like food, shelter and mate. Organisms interact with each other in many ways and these interactions have been categorised as inter-specific and intra-specific interactions.   Intra-specific Interactions: These are the interactions which take place between the individuals of same species.  Inter-specific Interactions : These are the interactions which take place between the organisms of different species. Inter-specific interactions may involve such relations where both the interacting individuals may get benefited and the association is non-obligatory or both the interacting individuals may get benefited and the association is obligatory, or one may get benefited and other remains unaffected or one may get benefited and other is harmed as such, such inter-specific interactions are called as Proto-cooperat...

  Why do we classify organisms?  Is now well know to us.There are different schools of thought as for as the classification of the organisms is concerned. They include biological Taxonomy, Hierarchical Taxonomy, phenetic Taxonomy and cladistic taxonomy.  Cladistics  is what we will be dealing with, in the current blog. It is a a modern system of classification of organisms which takes into account many aspects in addition to morphological characters i.e. form which was a sole criterion for Linnaean classification. Origin of cladistics dates back to early 1900AD but it was Willi Henning in 1960s  who coined the term cladistics/phylogenetic systematics, he also developed methodology related to cladistic analysis.  Cladistics is a biological classification system which  groups organisms on the basis of shared ancestral characters. It takes into account the evolutionary relatedness e.g.  all the organisms having hair are placed in one group called as...

What was the need of giving scientific names to the organisms?  It was the inquisitive nature of the human beings and desire to know more about the objects and organisms around him that lead to naming of the animals. In pre historic times when mode of communications and transport were in the infancy,  when human beings used to live in the isolated places and independent societies, each society had its own language. The name of same organism in different languages was different e.g  peacock is a English name of a bird which is known as Moore in Hindi, Pfau in German, paon in French,  tovus in Uzbek languages and so on, similarly the lion is the English name of an animal which is known as sheer or Singh in Hindi, pinyen in Chinese, raion in Japanese and so on. Now can you imagine a Japanese trying to tell about the lion to an Indian when they hardly know about each other's language. Exactly same problem was started to be felt when the mode of transport evolved and diff...

In the previous write up we came to  know about how the system of five kingdom classification evolved from two kingdom classification, through three and four kingdom classification  systems  and how the six  kingdom classification has come into being by a little advancement over the five kingdom classification.   R.H. Whittaker in 1969 introduced Five Kingdom classification.    This system of classification holds its ground even today as the criteria chosen for the classification are logical and scientific.    The five kingdoms as were proposed by Whittaker include 1. MONERA 2. PROTISTA 3. FUNGI 4. PLANTAE 5. ANIMALIA. This system of classification takes into account five criteria, which are as under:    1. Complexity of the cell: On the basis of complexity of the cell, all living organisms are categorized into two groups which include prokaryotes and eukaryotes. A. Prokaryotes: Those organisms which lack well d...

In the previous topic we discussed briefly about the nomenclature, classification, Taxonomy and Systematics. We came to know that classification is grouping of organisms based on the similarities in their traits. The idea of the classification is very old, which dates back to the evolution of first civilized human society . The fundamental principals of classification have kept on changing  from time to time where as its essence has remained same althrough out. Now, today we would discuss the historical background of classification. Human beings of ancient time started naming organisms as per their choice.  The first clue of the classification comes from Vedas and Upanishids between 1500 B.C to 600 B.C. The eminint scholars of India were CHARAKA and SUSRUTA. In Vedas several terms have been used for plants and their parts. The plants of medicinal importance were collected and studied during that period .  Greek scholars like HIPPOCRATES and DEMOCRITUS around 460B.C. to 37...