Describe some of the main issues that involve our environment, and provide examples of how these issues affect our environment.

These are some of the main issues in our environment.
1) Pollution
Air pollution, Water pollution and Soil pollution are a common problem which require million of years to recoup.
2) Global Warming
    Human practices like emission of greenhouse gasses, burning of plastics and the likes which results to the rise of the temperature of the ocean and earth's surface.
3) Overpopulation
The world is crowded and would require more resources to sustain all the needs of the population. There will be scarcity and humans will be forced to develop and practices which can harm the environment.

A mosquito in which the agent of diseases undergoes a a portion of its life cycle is known as a biological vector.

Explanation:

A malarial parasite undergoes half of its life cycle in a female Anopheles mosquito and the remaining half of the pathogenic phase in a human being. The parasite multiplies in the body of the female Anopheles mosquito and as that mosquito bites a healthy individual he becomes infected. Thus the mosquito serves as a vector that transmits the pathogen form a unhealthy individual to a healthy individual.