Life-history theory is like a game plan for how animals grow and live their lives. Just like how you plan your day, animals plan their whole life from birth to old age.
They plan how much time they spend eating, sleeping, playing, and finding a mate. They also plan how many babies they want to have and when to have them.
Animals need to make these plans because they only have limited resources, like food, water, and energy. They need to make the most out of what they have to live as long and as successful a life as possible.
There are two main ways animals can use their resources. They can either use them to grow bigger and stronger, or they can use them to have more babies.
Animals that live in places with lots of food and few predators can afford to grow bigger and slower. They can take their time finding a mate and having babies because they have plenty of resources to support them.
But animals that live in dangerous places with little food need to reproduce as quickly as possible before they are eaten or starve. They will not grow as big so they can spend more energy producing babies and taking care of them.
In conclusion, life-history theory is like a game plan for animals on how to use their limited resources wisely, whether to grow bigger and stronger or to have more babies quickly, depending on their environment.