Cytotoxic T cells use two basic mechanisms to destroy target cells: 1. Cytotoxic T cells release perforins which create pores on the target cells and granzymes which stimulate the apostosis of the target cells by exocytosis. 2. Cytotoxic T cells bind specific membrane receptors on the target cells and stimulate apostosis process which eliminate the target cells.
This phenomenon is not rare in the animal kingdom. Known as alternative mating strategies, it is employed by a subgroup of males that are usually incapable of facing the larger males in direct confrontations.
These "sneaky males" as they are sometimes called, will employ alternative strategies to mate with females. Which strategy will be dominant is dependent on the environmental factors and is not permanent. In some conditions where food is not that abundant, there will be less larger males and thus, the smaller males employing this strategy will be more common. At other times the opposite will occur.
However, in most cases and most probably here, the end result will be a coexistence of this traditional and alternative mating strategy, where males will exhibit a greater diversity in phenotype.
Answer:
B) The Light Microscope
Explanation:
Using a light microscope, one can view cell walls, vacuoles, cytoplasm, chloroplasts, nucleus and cell membrane. Light microscopes use lenses and light to magnify cell parts. However, they usually can achieve a maximum of 2000x magnification which is not sufficient to see many other tiny organelles.
Answer: The early earth environment was having hydrogen in abundant amount. the early atmosphere was full of methane, ammonia, hydrogen sulfide and water. Today the atmosphere contains 0.03% of carbon dioxide in the environment which was higher in the early days of life. There was no life because of less amount oxygen in the environment.
Now the environment is full of oxygen and has less amount of carbon.
