For survival of pathogen within the environment of the host, pathogen have to :-

Answer

### Step-by-Step Text Solution:

1. **Understanding the Question**: The question asks about the requirements for a pathogen to survive within the host's environment. This involves how pathogens interact with and adapt to the conditions present in the host's body.

2. **Definition of Pathogen**: A pathogen is any organism that can cause disease, including bacteria, viruses, fungi, and parasites. For a pathogen to thrive, it must successfully navigate the host's defenses and environmental conditions.

3. **Adaptation to Host Environment**: Pathogens must adapt to the specific conditions of the host's body. This includes:
- **pH Levels**: Different parts of the body have varying pH levels (e.g., skin, stomach, intestines). A successful pathogen must be able to withstand or thrive in these specific pH conditions.
- **Temperature**: The human body maintains a relatively constant temperature (around 37°C). Pathogens must be able to survive and reproduce at this temperature.
- **Nutrient Availability**: Pathogens need to access nutrients within the host to survive and multiply. They must be able to utilize the nutrients available in the host's environment.

4. **Examples of Pathogen Survival**:
- **Pathogen 1**: This pathogen successfully enters through the skin and adapts to the skin's pH, allowing it to survive and thrive.
- **Pathogen 2**: This pathogen attempts to enter through the skin but fails to adapt to the skin's pH and subsequently dies. This illustrates that without proper adaptation, the pathogen cannot survive.

5. **Conclusion**: For a pathogen to survive within the host's environment, it must adapt to the various conditions present in that environment. This includes adjusting to pH levels, temperature, and nutrient availability.