Diseases and competition are important factors that affect how populations of living things grow and change. They can make a big difference in how stable or how large a population can be.

1. How Diseases Affect Populations:

• Diseases can quickly shrink the size of a population. When a sickness (pathogen) enters a group of living things, it can spread very fast, especially if they are packed closely together, like in crowded places.
• This fast spread can lead to many individuals dying at once. This change can upset the balance between how many are being born and how many are dying, which will lower the overall population.

2. The Role of Competition:

• Living things compete for important resources like food, water, and space. When these resources are hard to find, they must fight for what they need, which often means that only the strongest or best adapted will survive.
• This competition helps determine the carrying capacity. Carrying capacity is the largest number of individuals that an environment can support without running out of resources.

3. Patterns of Population Growth:

• At first, when a population starts to grow, it can increase very quickly. This is called exponential growth. But once the population gets larger, things like disease and competition start to have a stronger effect.
• This change leads to what is known as logistic growth. In this phase, the population levels off around the carrying capacity, meaning it stabilizes rather than just keeps getting bigger.

In summary, both diseases and competition help keep populations in check. They work together to make sure that ecosystems remain stable and healthy.