To solve this problem, we need to understand the definition of natality.$\newline$Natality is a term used in ecology and population biology.$\newline$Let's analyze each option:$\newline \bullet$Option 1: Number of individuals leaving the habitat.$\newline$ - This refers to emigration, not natality.$\newline \bullet$Option 2: Birth rate.$\newline$ - Natality is defined as the birth rate, which is the rate at which new individuals are added to a population through reproduction.$\newline$ - Therefore, this option correctly defines natality.$\newline \bullet$Option 3: Death rate.$\newline$ - This refers to mortality, not natality.$\newline \bullet$Option 4: Number of individuals entering a habitat.$\newline$ - This refers to immigration, not natality.$\newline$Based on the analysis, the correct definition of natality is given by Option 2: Birth rate.$\newline$Therefore, the correct option is Option 2.