Tag: biology

The endocrine system includes ductless glands that secrete hormones and release them directly into the blood. This makes option E correct about the system. Second messengers are the low molecular weight molecules that serve to transmit and amplify the signal of hormones, the first messenger, to initiate the downstream enzyme cascade inside the cell. Second messenger pathway is activated by binding of hormones to the receptor molecules present on the surface of target cells only. 

Endangered species is a species facing a high risk of extinction in the near future due to a decrease in its habitat, excessive predation or poaching. 
The population of vulnerable species is presently sufficient but can become endangered in near future due to loss of habitat.
Critically endangered taxon is facing a high risk of extinction in the wild and can become extinct any moment in the immediate future. 
Lion (Panthera leo persica) is at a higher risk of extinction due to loss of habitat.

Until the 20th century, the asiatic cheetah was quite common and roamed all the way from Arabia to Iran, Afghanistan and India. 

Extinct: A species those having no living members.
Endangered: A species those are facing high risk of extinction in the wild in near future.
Critically endangered:  A taxon is critically endangered when it is facing an extremely high risk of extinction in the wild in the immediate future.
Vulnerable: A taxon is vulnerable when it is not critically endangered or endangered but is facing a high risk of extinction in the medium-term future.
Thus, the correct answer is option B.

The dodo (Raphus cucullatus) is an extinct flightless bird that was endemic to the island of Mauritius, east of Madagascar in the Indian ocean. It became extinct in 14th century from Mauritius because of large-scale hunting. Dodo was helpful in pollinating and propagating seed of this tree species. Subfossil remains show the dodo was about 1 metre (3 ft 3 in) tall and may have weighed 10.6–21.1 kg (23–47 lb) in the wild. 

Ex-situ conservation is the preservation of components of biological diversity outside their natural habitats. Cryopreservation is the only option here where the species are preserved at very low temperature to preserve structurally intact living cells and tissues.

Endangered species is a species facing a high risk of extinction in the near future due to a decrease in its habitat, excessive predation or poaching e.g., Ailurus fulgens (Red Panda), Bentinckia nicobarica. 

The IUCN 'Red List' (2004) documents the extinction of 784 species (including 338 vertebrates, 359 invertebrates and 87 plants) in the last 500 years. Some examples of recent extinctions include the dodo (Mauritius), quagga (Africa), thylacine (Australia), stellers sea cow (Russia) and three subspecies (Bali, Javan, Caspian) of tiger.

The dodo is an extinct flightless bird, that was endemic to the island of Mauritius, east of Madagascar in the Indian Ocean. The scientific name is Raphus cucullatus. The Dodo was first described in 1601 from the island of Mauritius. By 1681 it had become extinct as a result of hunting by Dutch colonists. It became extinct becuase of its flesh and the bird was flightless too, which increased its predation and poaching.

Reed buntings are some of the most 'adulterous' birds on record. As a result, over half the chicks in a nest may not have been fathered by the female's mate. Feigning injury to lure potential predators away from their nests, which are built dangerously close to the ground albeit amongst dense vegetation, is one of the ways that parent birds protect their young. Reed buntings are wetland birds and widespread throughout central and northern Europe.