Lack of space in a population could lead to an increase in

Step 1: Analyze the question The question asks what happens when a population has too little space, which means overcrowding. This is a population ecology idea.

Step 2: Explain the concept When a population becomes too crowded, density-dependent factors begin to limit its growth. These include:

• Competition for food, water and mates
• Spread of communicable diseases, because organisms are in close contact
• Increased stress and aggression
• Build-up of waste products

Think of a overcrowded school hostel or a crowded motor park. Infections like cholera, measles or tuberculosis spread quickly when people live very close together.

Step 3: Evaluate each option

• A. Water scarcity: This depends on the environment, rainfall and water sources. Lack of space does not directly cause it, though overcrowding may increase demand for water. It is not the best answer.
• B. Birth rate: Overcrowding usually reduces the birth rate because of stress and competition for resources, so this is wrong.
• C. Disease rate: Close contact helps pathogens and parasites spread easily, so disease rate increases. This is correct.
• D. Drought: Drought is a climatic condition caused by lack of rainfall. Population space has no direct effect on it, so this is wrong.

Step 4: Answer The correct option is C. disease rate.

Exam tip: For overcrowding questions, remember the chain: overcrowding → competition + easy spread of disease → higher death rate and lower birth rate. Drought and rainfall are climatic factors, not population factors, so you can eliminate them quickly.