Answer:
We have just seen that pathogens constitute a diverse set of agents. There are correspondingly diverse ranges of mechanisms by which pathogens cause disease. But the survival and success of all pathogens require that they colonize the host, reach an appropriate niche, avoid host defenses, replicate, and exit the infected host to spread to an uninfected one. In this section, we examine the common strategies that are used by many pathogens to accomplish these tasks.
Explanation:
The first step in infection is for the pathogen to colonize the host. Most parts of the human body are well-protected from the environment by a thick and fairly tough covering of skin. The protective boundaries in some other human tissues (eyes, nasal passages and respiratory tract, mouth and digestive tract, urinary tract, and female genital tract) are less robust. For example, in the lungs and small intestine where oxygen and nutrients, respectively, are absorbed from the environment, the barrier is just a single monolayer of epithelial cells.
Skin and many other barrier epithelial surfaces are usually densely populated by normal flora. Some bacterial and fungal pathogens also colonize these surfaces and attempt to outcompete the normal flora, but most of them (as well as all viruses) avoid such competition by crossing these barriers to gain access to unoccupied niches within the host.
A. a tropical disease caused by a parasite
Answer:
Explanation:
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Answer;
Without the keystone species, the rocky inter-tidal ecosystem would be dramatically different or cease to exist altogether
Explanation;
Keystone species have low functional redundancy. This means that if the species were to disappear from the ecosystem, no other species would be able to fill its ecological niche.
For instance; the starfish Pisaster ochraceus is a keystone species in the rocky marine inter-tidal communities off the northwest coast of North America. It feeds on the mussel Mytilus californianus and is responsible for maintaining much of the local diversity of species within certain communities.
Pain while urinating (burning)
feeling like you need to urinate more frequently
pain or pressure in lower back
odd smelling urine
