Biology Today - February 2018

Landscape

Unit of land distinguished by a natural boundary and having patches of different ecosystems, HJ, Southern peninsula.

Biome

A large regional unit delimited by a specific climatic zone, having a particular major vegetation zone and its associated fauna, HJ, tundra, desert,

temperate deciduous forest, tropical rain forest.

Biosphere

Biologically inhabited part of earth alongwith its physical environment consisting of lower atmosphere, land and water bodies.

Flow chart : Ecological levels of organisation

ENVIRONMENT, WEATHER, CLIMATE, HABITAT AND NICHE

Environment

• It is the sum total of all biotic and abiotic factors, substances and conditions that surround and potentially influence organisms
  without becoming their constituent part. Various components of environment are interlinked as well as interdependent.

Weather

• The short-term properties of the atmosphere such a heat, cold, cloud, rain, wind, etc., at a given place and time is called weather.


• It varies from place to place at the same time and also at the same place at different times.

Climate

• It refers to the average weather conditions of a particular area.


• Temperature and rainfall are the most important factors that determine the climate of an area.


• On the basis of variation in mean temperature along the latitude, four climatic zones have been recognised which is discussed
  in the table given below:
  Zone Latitude Average mean
  temperature

Winter season Characteristic vegetation

(i) Tropical zone 0°-20° > 24°C Nil Tropical forests

(ii) Sub-tropical zone 20°-40° 17°-24°C Mild winter Sub-tropical deciduous forests

(iii) Temperate zone 40°-60° 7°-17°C Winter with occasional snow Mixed coniferous forests

(iv) Arctic and Antarctic zone 60°-80° < 7°C Severe, prolonged winter

with abundant snow

Arctic vegetation

Habitat

• Habitat refers to a specific place where a species normally lives. It is delimited by a combination of factors such as pond,
  desert, river, valley, saline soil, etc., where a community resides.


• For examples the habitat of the malarial parasite,3ODVPRGLXPYLYD[ is the red blood corpuscles of human for a part of its
  life cycle and stomach of the female $QRSKHOHV mosquito for the other part of its life cycle.


• More than one animal or plant species may live in the same habitat.

Niche

• This refers to the specific part of habitat occupied by individuals of a species which is circumscribed by its range of tolerance,
  range of movement, microclimate, type of food and its availability, shelter, type of predator and timing of activity.


• Tadpole and adult frog occupy different ecological niches as the former is herbivorous aquatic while the latter is carnivorous
  amphibian.


• An ecological niche supports a single species. Each species occupies a distinct niche and no two species occupy the same niche.


• Sometimes unrelated organisms occupy same niche, through their habitats are different, known as ecological equivalents.
  In the same habitat, a common resource can be exploited by a group of species, called guild.