What are pathogens, and how can they infect the human body? be descriptive. you!

We normally think of pathogens in hostile terms—as invaders that attack our bodies. But a pathogen or a parasite, like any other organism, is simply trying to live and procreate. Living at the expense of a host organism is a very attractive strategy, and it is possible that every living organism on earth is subject to some type of infection or parasitism (Figure 25-1). A human host is a nutrient-rich, warm, and moist environment, which remains at a uniform temperature and constantly renews itself. It is not surprising that many microorganisms have evolved the ability to survive and reproduce in this desirable niche. In this section, we discuss some of the common features that microorganisms must have in order to be infectious. We then explore the wide variety of organisms that are known to cause disease in humans.

measuring light intensity

light meters can be used to measure light intensity. the meter is held at the soil surface and pointed in the direction of the maximum light intensity, and then the meter is read.

errors can be made when measuring light intensity by accidentally shading the light meter. the reliability of the results can be checked by taking many samples.