Tag: zoology

A retrovirus has been identified as a single-stranded positive sense RNA virus which has an intermediate DNA that helps it target the host cell as an obligate parasite. This virus reverses the usual pattern and uses its transcriptase enzyme to produce DNA. The transmission of these viruses been generally cell-to-cell. In human beings, cancer can be triggered by proto-oncogenes present in the retrovirus which are mistakenly incorporated into proviral DNA or by the disruption of the cellular proto-oncogenes

• Cancer is a class of diseases characterized by out-of-control cell growth. There are over 100 different types of cancer, and each is classified by the type of cell that is initially affected.
  
• Cancer harms the body when damaged cells divide uncontrollably to form lumps or masses of tissue called tumors. Tumors can grow and interfere with the digestive, nervous, and circulatory systems, and they can release hormones that alter body function. Tumors that stay in one spot and demonstrate limited growth are generally considered to be benign.
  

The basic unit of ecological hierarchy is individual because a community starts building from an individual which grows onto form an entire ecosystem. 

The biosphere is made up of the parts of Earth where life exists, but there is uneven distribution of living organisms in the biosphere. The biosphere extends from the deepest root systems of trees, to the dark environment of ocean trenches, to lush rain forests and high mountains.
Scientists describe the Earth in terms of spheres - Lithosphere, Atmosphere, Hydrosphere. Since life exists on the ground, in the air, and in the water, biosphere overlaps all these spheres. Biosphere has existed for about 3.5 billion years.

A.An organism is an individual living thing. It can be as simple as a single-celled Amoeba or it can be as complex as a human being.
B.A tissue is a collection of structurally similar cells acting together to perform a specific function.
C.An organelle is a small constituent of a cell that has a specific function. For example, mitochondria (called as powerhouse of the cell) aids in generating energy for cell functions.
D.An organ is a group of tissues that performs a specific function. For example, stomach and kidney are organs. 

The biosphere is a global ecosystem composed of living organisms (biotic) and the nonliving (abiotic) factors from which they derive energy and nutrients. It is a relatively thin life-supporting stratum of Earth's surface, extending from a few kilometres into the atmosphere to the deep-sea vents of the ocean. 

All the biotic and the abiotic components together form biosphere or ecosystem. A biosphere is composed of all living organisms and nonliving things. The population is the number of individuals in a given area. Biome includes all flora and fauna. A trophic level is defined as the position of an individual in the food chain. So, the correct answer is option C.

The biosphere is the biological component of earth systems, which also include the lithosphere, hydrosphere, atmosphere, etc. The biosphere includes all living organisms on earth, together with the dead organic matter produced by them.