The correct answer here is "cell membrane". Generally it makes sure that nothing enters or leaves the cell, except by its highly guarded "gates", such as ion channels, that let some particles through - but they're very picky about whom to let in!
The regulatory centers for the respiratory and circulatory systems are found in the cerebrum
Answer:
The simplest virions consist of two basic components: nucleic acid (single- or double-stranded RNA or DNA) and a protein coat, the capsid, which functions as a shell to protect the viral genome from nucleases and which during infection attaches the virion to specific receptors exposed on the prospective host cell.
Answer: True
Succession is the phenomena in which changes in the biotic and abiotic factors of the environment leads to change in the ecosystem. A succession is a process in which a biological community is replaced by another biological community until a mature ecosystem is formed this process is influence by environmental factors. Primary succession is the primitive environment where no biotic community previously existed it is followed by secondary and subsequent succession were life forms develop and form an ecosystem. Some of the environmental factors are:
Topographical : These are the change in the region or habitat were succession occurs. Landslides, volcanic eruption, glacier melting etc. are the examples , as these topographical changes can bring reformation of the landscape. The disturbance caused by these topographical changes will allow the disturbance tolerant species to repopulate the habitat. This can be a transition from primary to secondary succession.
Soil : It is an abiotic factor.The growth of the plants requires suitable soil conditions. The type of soil will affect which species will inhabit the area. The soil moisture and pH greatly affect the number of plant species in an area.
Climate : It can influence the direction of succession. Climatic factors includes rain, wind etc. For example a region lacking proper rainfall the species will be tolerant to dry and drought conditions. The region with heavy rainfall, the species will be more tolerant to moisture. Wind being a climatic factor can cause wind erosion affect the soil quality. Wind can lead to heavy forest fires can therefore, wiped out community.
