An ecosystem is the group of food supply, predation, and competition. The chapter Organisms And Populations NCERT highlights the fitness of individuals, measured by their survival, growth rate, and reproductive success. Therefore, the population of a species in a given ecosystem or habitat depends on several factors such as climate, food supply, and predators. A species' population can increase or decrease depending on the aforementioned factors. The population that increases is known as the "expanding population," while the one that decreases is called "contracting population." Organisms And Populations Class 12 NCERT explains how food and energy availability affects the populations of organisms in an ecosystem. The population grows when food and energy are abundant in the environment. On the other hand, it decreases when these resources are scarce within the ecosystem.
Organisms And Populations Class 12 NCERT highlights that habitat includes all biotic and abiotic elements having a specific role in supporting the species present there. It determines where a particular organism lives or spends most of its time during its life cycle. Organisms And Populations NCERT states that population growth can be measured using birth rate, survival rate, age structure, density, and population stability. Population ecology stands for the population dynamics (the changes in the size of the population) of an individual species, population, or community. The study of population dynamics is known as Demography, while ecology is known for its Population Biology. Organisms And Populations Class 12 NCERT is about the Population Dynamics of a natural population for one year.
Organisms are living beings. An individual organism is called a cell or molecule. All organisms go through the same basic life steps: start with a single cell and divide into two cells. There are different organisms, including bacteria, plants, animals, and humans. Some organisms may be unicellular (one cell), while others may be multicellular (many cells). Organisms can grow from a single cell to an enormous size.
Organisms can be broadly categorised into two – macroscopic and microscopic. Macroscopic organisms are readily observable by the naked eye, such as people, trees, and animals. Though some unicellular organisms fall under this category, most microscopic organisms are multicellular and large (turtles and crocodiles). Microscopic organisms include single-celled organisms such as bacteria, algae, protozoa, and fungi.