What variables can affect the performance of a marathon runner?

Explanation:

There are a wide range of variables that can effect a marathon runner such as

Physical Fitness State

Mental Health State

Endurance levels

Weather

Environment

Hidration levels

etc.

As seen by the list above there are countless variables that can affect a marathon runner, the two main ones being their Physical and Mental Health state. If a runner is not physically prepared for a race then their body can easily turn on them and they can suffer from muscle cramps, fatigue, fainting, etc. While at the same time, if the runner is not mentally prepared for a race they can quickly lose interest and the desire to win/finish which are crucial.

clumped distribution, because you'de have all of the population gathered in a relatively small are.

it's the most common because it provides protection and a mate for reproduction

example: humans, seeweed, cattles, etc.