NEET Important Notes on Organisms and Population

The German Philosopher, Professor, Naturalist, and Biologist ‘Ernst Haeckel’ take credit in coining the term “Ecology”. At the biophysical level of environment, ecology is the natural state of interaction, reproduction, and survival across abiotic and biotic components. This level is also called the ‘Organismic Phase.’ 


For living species, life on earth is both comfortable and extreme, due to multiple internal and external factors. Understanding the concept of organisms and populations together is an interesting and also an informational piece of content. 


Hence, the following are some of the important pointers, factors, characteristics and other related noted from the organism and population NCERT text versions. After a thorough reading, you can also test your understanding of the ecology concepts, by trying out the FAQs section at the end of this learning module. 


2 Important Terms to Know 

Before we go for deeper learning, the terms ‘Habitat’ and ‘Niche’ are basic and significant ones inside the study of environmental sciences, ecology, and biology. Given below are the definitions for the same.

  • HABITAT: The natural surrounding/environment of a given organism is its Habitat. By thriving here, organisms adapt and develop their suitable survival mechanisms and defence system at times of threat.

  • NICHE: All the external and internal resources or factors that are required by a given organism in its natural environment is Niche. Niche gives an idea about an organism’s functional role for that particular ecosystem/habitat.


The 4 Major Abiotic Factors with 5 Tolerances

In any particular ecosystem, Light, Soil, Water, and Temperature are the 4 major abiotic factors noted. The tolerance to these factors are listed as 5 below:

  1. Stenothermal - When the temperature levels cannot be tolerated (intolerance).

  2. Eurythermal - When the temperature and its changes are bearable (tolerance).

  3. Photoperiodism - Plants are directly influenced by the amount of sunlight they acquire for flowering purposes. This varies across plants as short-day, long-day, and some-day neutral plants.  Some-day ones do not have any impact over its flowering process from sunlight. 

  4. Stenohaline - When the changes in salinity cannot be well-managed (intolerance).

  5. Euryhaline - When the salinity and the changes are supportable (tolerance).

Species tend to have their defence mechanism and other coping strategies to overcome and balance the changes that happen in their natural habitat (or at least inside their niche). Some of the best responses to the mentioned above abiotic factors are given in the following context.


What are the Possible Responses to Abiotic Factors?

  • Adaptation: Adapting to the new ecosystem is the most common way of responding to changes that occur in the abiotic system. Species can adapt physiologically, morphologically or even behaviourally. 

  • Suspended Animation: In the case of algae, fungi and many other microorganisms, they try to avoid the unfavourable changes/conditions by forming a thick-walled spore. For example, seed dormancy is a form of suspension to give protection to its seeds from desiccation. 

  • Conforming: Conform or confirming is observed in a majority of animals and plants when they are unable to maintain their temperature internally like that of poikilotherms. Conformers are the extreme opposite to Homeotherm (animals that maintain their thermal homeostasis).

  • Allen’s Rule: For minimizing heat loss, mammals in colder regions or climate have smaller ears and limbs. Blubber is a classic example. 

  • Migration: Predominantly noted in birds, species mirage, i.e. move from 1 region to another area temporarily. Albatross, Osprey, Siberian Crane, Eurasia Blackcap are some of the examples of birds that migrate. 


Important Notes on Organisms and Populations

Organisms and populations are directly proportional to each other and changes in 1 system affect the other. Some of the important pointers regarding population along with organisms as a complete data set are given in the following:

  1. In a specific geographical location, the number of inbreeding species count refers to its ‘total population.’  

  2. Age pyramid, Sex ratio, Birth rate, Death rate, immigrating new individuals, people who emigrate, etc. are some of the ‘Population Attributes.’ 

  3. The per cent (%) coverage or biomass for a set of organisms and populations is called ‘Population Density’.

  4. Counting each organism is not possible to calculate the population density. Indirect means such as faecal pellets of a tiger or the count of fish caught per 1 trap or the pugmarks left by an animal are essential. 

  5. Mortality, Natality, Immigration, and Immigration are the 4 factors that affect population growth. This can be evaluated by the formula Nt+1 = Nt + [{(B + I) – (D + E)}]. 

  6. Population interaction includes Mutualism (all species win), Competition (both species lose), Parasitism (1 harmed and 1 win), Predation (1 harmed and 1 win), Commensalism (1 harmed and 1 not affected), and Ammensalism (1 harmed and the other not affected). 

FAQ (Frequently Asked Questions)

1. What is Hibernation?

The Hibernation is a form of resting phase, where animals escape from cole weathers by hiding inside their shelters for a longer duration. This form of a survival strategy is called Winter Sleep and is observed in organisms such as rodents, bats and squirrels.

2. What are the Attributes that a Population has but Individuals do not Possess?

Birth rate (natality), the death rate (mortality), age distribution, sex ratio (females: males) and population density are some of the attributes that a population has but individuals do not possess.

3. Name a Few Plants that have a Chemical Defence Mechanism.

Nicotine, quinine, caffeine, opium and caltrops are some of the plants that release noxious chemical substances as a form of defence mechanism.

4. What is the Difference Between an Endotherm and Exotherm?

Endotherms are animals that have a body temperature that is different from their environment. Examples include fishes and reptiles. The body temperature will remain constant in the case of exothermic organisms (exothermic). Many mammals and bird species are exotherms.

5. What are Camouflaging Organisms?

Also referred to as Cryptic Colouring, Camouflaging organisms are species that have a tactic defence mechanism of escaping from their predators by disguising their location, movement or identity. Madagascar and Panther’s chameleon species possess this super-defence of changing their body colour to the environment. Even lizards, jaguars and frogs are camouflaging organisms.