Connecting Link Between Living and Non-Living:
A virus is considered a connecting link between living and non-living entities. Viruses are not considered living organisms because they lack the ability to carry out metabolic processes on their own. They can only replicate inside the cells of living organisms. However, viruses possess genetic material (DNA or RNA) like living organisms and can undergo evolution through mutation.

Study of Microorganisms:
Microbiology is the study of microorganisms, including bacteria, viruses, fungi, and protozoa. Microorganisms are ubiquitous in nature and play crucial roles in various ecological processes, such as nutrient cycling and decomposition. Microbiology also encompasses the study of microbial genetics, pathogenesis, and biotechnology.

Hard Covering of Bacteria:
The hard covering of bacteria is known as the cell wall. The cell wall provides structural support and protection to the bacterial cell. It helps maintain cell shape and prevents the cell from bursting due to osmotic pressure. The composition of the cell wall varies among different types of bacteria, with some having a thick layer of peptidoglycan, while others may have additional layers like an outer membrane.

Disease Caused by Plasmodium:
Malaria is a disease caused by the Plasmodium parasite. Plasmodium is transmitted to humans through the bite of infected Anopheles mosquitoes. The parasite infects red blood cells and causes symptoms like fever, chills, and flu-like illness. If left untreated, malaria can lead to severe complications and even death.

Fungal Disease of Wheat:
Stripe rust, also known as yellow rust, is a fungal disease that affects wheat crops. The fungus Puccinia striiformis causes stripe rust by infecting wheat leaves and reducing photosynthetic activity. This leads to yellowish stripes on the leaves, affecting the plant's growth and yield. Stripe rust can be controlled through fungicide applications and planting resistant wheat varieties.