Here's why:

* Life processes require energy: From basic cellular functions like growth and repair to more complex activities like movement, reproduction, and maintaining body temperature, all living organisms need energy to carry out these processes.

* Source of energy: Living things obtain energy from their environment. Plants use sunlight for photosynthesis, while animals get energy by consuming other organisms.

* Energy fuels all life: Without energy, life as we know it wouldn't exist.

Think of it this way: Energy is like the fuel that powers a car. Just as a car cannot move without fuel, living things cannot function without a source of energy.