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Organisms and Population

Organisms and Population

Edited By Team Careers360 | Updated on May 09, 2022 05:37 PM IST

Organism and its Environment
The branch of science that studied the relationship between living things and the environment is called ecology. The various levels of organization are:
(i) Organism: each animal/bird who is part of a species.
(ii) Population: A group of species that can reproduce.
(iii) Communities: A diverse group of people come together to form communities.
(iv) Biomes: Large number of plants and animals found in the climate zone.

Major Abiotic Factor

(i) The most important biotic factor affecting the environment, as well as living organisms, is temperature. The temperature around the poles is much lower than the average temperature near the equator. The polar region temperature rises from the subzero and rises to 500C in the hot summer desert. Temperature will affect the rate of metabolism and physiology of the body as it affects enzyme kinetics. Those creatures that can withstand high temperatures are called eurythermal. Eg, dog, cat, red algae, etc. while a large number of organisms tolerate a small temperature called stenothermal. Eg, anaconda, crocodile, penguin. Tolerance of living organisms depends on the type of environment in which they are found.

(ii) Another important abiotic factor for life is water on which it depends. The area where the water level is low is called deserts where only endangered species can survive. In a body of water, the composition and pH of water are very important. The salt content of some species is very high called euryhaline, eg, crab and molly fish while in some organisms the level of salt tolerance is very low called stenohaline eg, haddock, goldfish, etc. Marine living things are found to be small. accustomed to seawater and vice versa due to its distinct osmotic nature.

(iii) Another important feature of the abiotic factor is light that is useful in the process of photosynthesis and can be seen in the case of autotrophs. The main source of light, most commonly known, is the sun. The demand for light varies from living thing to living thing as some organisms need more light while other organisms need less light. There are different types of plants that are classified according to the light needed, short day plants and long day plants. In animals, small fluctuations in light will affect a variety of plant functions including migration, reproduction, and feeding. The level of the sun's spectrum is very important for health. The spectrum contains ultraviolet radiation that is extremely harmful to living organisms while different colors of the visible spectrum are not found in marine organisms found at various depths of the ocean.

(iv) Another important abiotic factor affecting biodiversity and population is soil. The nature of the soil and the characteristics vary depending on the type of climate, as well as the climatic process, soil growth, soil transport, or sedimentary. There are a variety of parameters that affect the type of soil such as pH, the minerals present in the soil, and the environment. Apart from this, other parameters such as pH, mineral composition, and topography depend on the type of plants and animals present.

Reactions Abiotic Factors

Biodiversity reacts differently to different abiotic factors. The answers to the abiotic factor are:

(i) Regulators: These are the organisms that can maintain homeostasis and control leading to constant body temperature, osmotic saturation, etc. This area can be seen in the story of birds and mammals as well as a few vertebrates and invertebrates. In humans, body temperature is maintained at 37 degree celsius leading to homeostasis. In the summer when the temperature is too high the body sweats to maintain a body temperature similar to the process of evaporation leading to cooling. In winter, the outside temperature is very low so the body saves continuously to keep the internal body temperature warming. In the case of plants, this internal body temperature monitor does not exist.

(ii) Conformers: These are living organisms that can control their body temperature. Their bodies emit or absorb heat that leads to an increase or decrease in body temperature leading to a thermoregulation process that is a powerful process. In the case of small animals, the surface-to-volume ratio is large so that body heat is released quickly, therefore, the animals are not in a polar zone. The evolutionary process will lead to a number of benefits.

(iii) Partial Controls: These are the species of animals that can control but to a certain extent depending on the environment. Organisms simply receive confirmation when they cross this line.

(iv) Migration: The movement of animals from one place to another according to their needs. For example, winter migratory birds from Siberia to Keoladeo National Park (Bharatpur) in Rajasthan due to stressful conditions in their area.

(v) Spores: There are certain microorganisms that include bacteria, fungi, etc. to stop their growth during adverse environmental conditions. As in winter, animals get hibernation, while in summer they get a summer sleep called a festival.


An element that helps an animal to survive or reproduce in its habitat is called adaptation. It is noteworthy that living things tend to adapt to their environment. For example, in desert plants such as Opuntia, they have thick pieces, leaves that have been transformed into spines, and a damp stomata to reduce transpiration and photosynthesis with the help of the CAM method. While in the case of high altitudes such as mountains and hills, people have shown high altitude sickness caused by nausea, shortness of breath, fatigue, palpitations, etc. red blood cells so that more oxygen can bind to it and increase respiration rate. There are certain behavioral responses that can be observed in a variety of animals based on natural conditions.


Population Attributes

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The group of people that includes those species that are able to breed among themselves and that leads to the formation of fertile offspring is called the population. There are various demographic factors including birth rate and death rate. Population growth is called birth rate while mortality rate is declining. Another characteristic of the population is the measure of gender, the age distribution that can be represented as an age pyramid that reflects the demographic status. The number of people in the pyramid of age may appear to be increasing, stable, and shrinking. Population growth is a feature of a growing population that includes more young people than adults. The situation in which young and old are equal at the time is called stable while older people are compared to younger and the age pyramid is said to be declining.

NCERT Books Link:

Population Growth

The size of the population of any species may never stop, depending on the availability of food sources, weather conditions, and predators. There are four main reasons for the change in population density:

(i)Natality: Described as the number of children born over a period of time.

(ii) Death: Described as the death toll in a given period.

(iii) Immigration: It is defined as the number of people who come to a habitat from different places for a period of time.

(iv)Emigration: It is defined as the number of types of population that exit the habitat for other places.

If the Population density is N at time t, then its density at time t+1 is represented as

Nt + 1 = Nt + [(B + I) - (D + E)]

When overcrowding is represented by N during t, the birth rate is represented by B + I while the mortality rate is represented by D + E.

NCERT Notes Subject Wise Link:

Population Interactions

Interactions between different organisms can be divided into two categories, namely, interspecific interactions and intraspecific interactions. When an interaction occurs between similar species then it is called an Intraspecific interaction while an interaction between different organisms then it is called an interspecific interaction.

(i) Predation: Cooperation when a deer is killed by an invader. This is important in keeping predators afloat. In plants, herbivores act as predators. In some plants, a variety of habits are found that help them to protect themselves from predators. Familiarity may include thorns such as preservatives or protective substances such as caffeine, nicotine, quinine, etc., used for commercial purposes.

(ii) Competition: An interaction between an organism in which both organisms compete for a variety of resources including food, water, habitat, etc. Meat may be of the same type or of different types. This interaction occurs when resources are limited. According to the Gause Policy on Competitive Exclusion. The two adjacent models will compete for the same services and are not competitive so the lower one will be released during the competition.

(iii) Parasitism: An interaction where one type is dependent on another type which leads to the benefit of one type and harms another. Those parasites feed on the outer surface of living organisms called ectoparasites. For example, marine fish include ectoparasitic copepods. In the case of birds, there is Brood parasitism where birds lay their eggs in the bird's nest while the host incubates them.

(iv) Commensalism: An interdependence of species where it is recognized that one species benefits and the other is neither benefited nor harmed. For example, an orchid growing like an epiphyte on a mango branch.

(v) Mutualism: An interaction where both species will benefit from each other. Examples are lichens (the relationship between algae and fungi), and mycorrhiza (symbiotic relationship between fungi and high plant roots).

(vi) Amensalism: An interaction between an organism in which one species is harmed while another species is harmless or harmless.

NCERT Solutions Subject wise link:

NCERT Exemplar Solutions Subject wise link:

Frequently Asked Question (FAQs)

1. What is adaptation? Give Examples.

Any quality of an organism that allows it to live and reproduce in its own place is called adaptation. It is a fixed attribute and living things tend to adapt to their environment. Desert plants with a thick cuticle or submerged stomata to reduce water loss by changing the air are an example of adaptability. Organisms also show physical adaptations such as people exhibiting high altitude illnesses such as nausea, vomiting, heart palpitations, etc. and they become accustomed to the environment after some time.

2. What are the different types of responses that Living Organisms have in relation to Abiotic Factors?

Different types of biological responses include:

  • Regulate
  • conform
  • Partial Controls
  • Migration
  • suspend (spores)
3. What Are The Key Factors That Contribute to Demographic Change?

Population density changes mainly because of the following factors:

  • Natality
  • Mortality
  • Immigration
  • Emigration
4. Explain briefly about the major abiotic factors.

One of the great abiotic features is Temperature.

Temperature is one of the strongest forces affecting living and nonliving things on Earth. Next, water is also a necessary abiotic factor in living organisms and the environment. Many organisms are altered due to the availability of less or more water. Finally, light. Light is the most important abiotic factor in plant survival and the last aspect of abiotic soils that greatly affects biodiversity and plant growth.

5. What is a morphological defense mechanism?

The Morphological Defense Mechanism is one of the most important protective mechanisms in plants such as the cactus whose leaves have been transformed into sharp thorns to prevent weeds from eating them. Some plants, such as using a morphological defense mechanism, have the edges of their spiny leaves or sharp edges that prevent insects from eating them.

6. Why are marine fish kept in freshwater aquariums having little chance of survival?

The chances of survival are diminished when marine fish are immersed in fresh seawater because their body is accustomed to concentrating large amounts of salt in the ocean floor. Since a fish cannot control the water that enters its body through osmosis, it causes its body to swell and eventually die.

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