Biology_Today_-_October_2016

Desert Biome

Location : It is present in rain shadow (area beyond high mountains

which cut off clouds e.g., Tibet), lack of cloud intercepting mountains

(e.g., Thar) or lying away from cloud seeding regions. E.g., Sahara

(Africa), Gobi, Arabian and Thar of Asia. Rajasthan lies in the Thar

desert.

Physical Characteristics : Desert can be cold (e.g., Tibet, Gobi) or

hot (e.g., Thar, Sahara). In true deserts, rainfall is less. Ground is sandy

or rocky. Vegetation is sparse.

Flora : It consists of three types of plants. (i) Ephemerals or short lived

annual herbs which grow during period when sufficient moisture is

available. (ii) Cacti and other succulent xerophytes (e.g., Euphorbia

species) which store water. (iii) Deep rooted shrubs and small trees

which are able to obtain water from the water table. Tall succulents,

mostly cacti, are abundant in deserts.

Fauna : Animals are kangaroo/desert rat, hare, fox, jackal, cat, rattle

snake, coral snake, lizards. Camel is adapted to desert conditions as

it can protect its eyes and nostrils from dust, has insulated spreading

feet, and is capable of tolerating dehydration upto 40% with highly

reduced urine output.

Grassland

Location : U.S.A, Canada, South America.

Physical Characteristics : There is hot summer, cold winter. Root

system is extensive. Grazing and fire help maintain grassland and

prevent woody species to invade the area.

Flora : Grasses are dominant with nongraminaceous herbs, mostly

leguminous (maintain nitrogen fertility of soil), scattered bushes and

occasional tree.

Fauna : Fauna consists of deer, elk, bison, wolf, prairie dog, bear,

bighorn sheep, rabbit, mice.

Tropical Savannah

Location : Savannah occurs in North Australia, India, Central and

Southern Africa including east-central S. Africa.

Physical Characteristics : Indian savannahs are largely anthropogenic

being derived from tropical forests and maintained by grazing as

well as fire. Availability of soil moisture determines composition and

productivity.

Flora : Common trees and shrubs of Indian savannahs are Acacia,

Butea, Prosopis, Zizyphus and Capparis. Many of them perform C 4

photosynthesis that is helpful in maintaining high productivity even

under conditions of low soil moisture.

Fauna : Hoofed herbivores are quite common. Animals include

antelope, zebra, giraffe, goat, rhino, elephant, fox, wolf, lion, tiger,

kangaroo.

Altitudinal Biome

Location : Occurs near the top of very high mountains having

permanent snow, e.g., Himalayas. It is treeless region and lies above

the timber-line.

Physical Characteristics : Slopy, well drained with little peat or

bog, herbaceous flowering plants and dwarfed trees.

Flora : Trees of lower region become tiny shrubs in this area. Other

constituents are lichens, mosses, grasses, herbs and small shrubs like

Artemesia, Anemone.

Fauna : Common animals include mountain goat, yak, wolves, snow

leopard, snow bear, rabbit, willlow grouse and some migratory birds.

ENVIRONMENTAL FACTORS

s Environmental or ecological factors are the constituents of environment which directly or indirectly influence the form and
functioning of organisms in any specific way.

Biotic factors

Living components of an environment constitute

biotic factor, which interact with abiotic factors of the

environment.

Abiotic factors

These factors are non-living factors, substances and conditions of the environment

which influence survival, function, behaviour and reproduction of organisms.

Major abiotic factors include temperature, water, light and soil.

Environmental factors

Abiotic Factors

1. Temperature

s Temperature or degree of hotness and coldness is the most relevant environmental factor. The average temperature varies

seasonally. It ranges from subzero levels in polar areas and high altitudes to more than 50°C in tropical deserts in summer.

s In some unique habitats, such as thermal springs and deep-sea hydrothermal vents, average temperature exceeds 100°C.

s Temperature not only influences the physiological functions but also the geographical distribution of many plants and animals.

s Temperature has a direct effect on the working of enzymes. Through enzymes, it influences basal metabolism, activity and other

physiological functions of the organism.