Question

Question 5: What are the major causes of species losses in a geographical region?

Class 12 - Biology - Biodiversity and Conservation Page 269

Answer 1

Biodiversity is the variety of living forms present in various ecosystems. It includes variability among life forms from all sources including land, air, and water. Biodiversity around the world is declining at a very fast pace. The following are the major causes for the loss of biodiversity around the world.

(i) Habitat loss and fragmentation: Habitats of various organisms are altered or destroyed by uncontrolled and unsustainable human activities such as deforestation, slash and burn agriculture, mining, and urbanization. This results in the breaking up of the habitat into small pieces, which effects the movement of migratory animals and also, decreases the genetic exchange between populations leading to a declination of species.



(ii) Over-exploitation: Due to over-hunting and over-exploitation of various plants and animals by humans, many species have become endangered or extinct (such as the tiger and the passenger pigeon).

(iii) Alien species Invasions: Accidental or intentional introduction of non-native species into a habitat has also led to the declination or extinction of indigenous species. For example, the Nile perch introduced in Lake Victoria in Kenya led to the extinction of more than two hundred species of native fish in the lake.

(iv) Co­−extinction: In a native habitat, one species is connected to the other in an intricate network. The extinction of one species causes the extinction of other species, which is associated with it in an obligatory way. For example, the extinction of the host will cause the extinction of its parasites

Answer 2

Answer:

Biodiversity is referred to the variety of living forms found in different ecosystems including variability observed in life forms from different sources such as air, water and land. However, biodiversity all around the globe is fast declining. Following are the major causes:

• Habitat loss and fragmentation – uncontrolled and unsustainable human activities such as slash, deforestation, mining, burn agriculture and urbanization causes habitats of different entities to be destructed or altered. This leads to the breakup of habitat into smaller pieces affecting the migration of animals and also a decline in the genetic exchange between populations resulting in a decline in the species.

• Co-extinction – One species is connected to the other in a native habitat in an intricate network. Hence, extinction of one species causes the extinction of the other wherein they are associated with each other in an obligatory connection. For instance, the extinction of host would cause the extinction of parasites.

• Over-exploitation – Humans have caused species to get extinct or endangered due to over-exploitation and over-hunting of different plants and animals. (extinction of passenger pigeons and tigers)

• Alien species invasions – Intentional introduction of non-native species into a particular habitat causes extinction of indigenous species. Example – Nile perch caused the extinction of more than two hundred species of native fish of Lake Victoria in Kenya when they were introduced in the lake.