- Living world
- Characteristics of living world
- Ability to sense surroundings
- Diversity in the living world
- Need for classification
- Objectives of classification
- Test yourself
As such when we say living, we tend to connect to certain properties that some of the organisms exhibit. Some of the unique features that immediately come to our mind are growth, reproduction, metabolism, ability to sense the surroundings, etc. Also, there is huge diversity in the living world. So, how indeed, we define living? What is life?
Let us try to understand this by looking into the characteristics that we discussed above.
Growth is simply the increase in mass and size but it can also be an increase in the number of individuals which we term as population growth. So growth of an organism is due to cell division and accumulation of substances in the cells. This increases the mass and size of an individual.
Reproduction is the process by which the progeny is produced which helps in the perpetuation of an individual’s race. The two main types of reproduction are as follows:
- Sexual reproduction – the production of new living organisms by combining genetic information from two individuals of different types.
- Asexual reproduction – it does not involve the fusion of gametes or change in the number of chromosomes. Therefore, termed asexual.
Living organisms are made up of chemical constituents that are continuously synthesized and utilized. The chemical reactions which aid these processes are termed metabolic reactions. Thousands of metabolic reactions occur in a living organism simultaneously. The sum total of all these reactions is termed as Metabolism. Metabolism aids in cellular organization.
4. Ability to sense surroundings:
All the living organisms have the ability to sense the surroundings and generate responses accordingly. Though the sensory mechanism is different for plants, animals, and other organisms they all perceive the surroundings. This could be termed as consciousness.
In the above-discussed properties, growth, of course, is a living character but cannot be defined as an all – inclusive living character. This is because we tend to see even non-living substances like rocks grow over a period of time. But due to the accumulation of substances from the external environment. Further, some of the hybrid living organisms like mules are sterile which do not exhibit reproduction. Hence, we cannot consider reproduction alone as an exclusively defining property of living organisms.
Metabolism, as discussed, is the sum total of all the chemical reactions happening in the living organism. Though isolated metabolic reactions can be replicated in a cellular free environment, in-vitro, these are considered as living reactions. No non-living system exhibits metabolic reactions. Hence, metabolism and cellular organization are the defining feature of living organisms. Moreover, along with metabolism, living organisms exhibit the ability to sense the surroundings. Hence, could add the defining features of living organisms.
Apart from these, the other characteristics include movement, organization, energy, homeostasis, and adaptation are also considered as some of the characteristics of the living world.
Diversity in the living world
The term diversity in the living world refers to the existence of a huge variety of organisms in a wide range of environments. Certainly the organisms vary in size, morphology, color, anatomy, habitats, and habits. Each different type of organism is called a specie. A total of 1.7 -1.8 million species have been discovered to date. This total refers to Biodiversity or diversity in the living world. These species could be existing or extinct. The extinct species are termed as fossils.
What is the need for classification?
As there are millions of species, it is very difficult to understand their nature and properties. To overcome this, we group them. Also, it becomes very difficult to understand the relationships between organisms. To overcome these problems, we introduce concept of biological classification.
The grouping of organisms based on the similarities and differences at different levels is known as Biological Classification.
Classification of organisms helps us to arrive at certain general conclusions by studying few organisms of a given group. This helps in establishing the phylogenetic relationships.
Objectives of Classification:
- To easily identify organisms and species
- Categorization of the organisms based on similarities and differences
- Another objective is to understand the evolutionary trends
- Moreover, to establish connections for the fossils, extinct, and existing organisms.