For plants it was turning sunlight into chlorophyl.
For animals ,that depends on which animal or organism the question pertains to. The main problem here is with the ambiguity of the question.
hunted animals and gathered wild plants
They survive thourgh the water cycle. First it starts in evaporation,condensation,precipitation,runoff and then transpiration. It then starts all over again.
Plants came first before animals.
Plants came first before animals.
The animal that first evolved, I guess. But no one knows what that was (because it lived millions and billions of years ago) or if there was an animal that evolved before all other animals. It would have eaten plants though because plants are plants, not animals and they use photosynthesis to survive.
plants so the animals can have oxygen
Plants were first.
plants
Unicellular plants and animals were first forms of life on Earth
Animals were created first, then shortly after plants were created because some animals were made to not eat meat, so plants were created.
Glucose is found in both plants and animals. Plants produce glucose by photosynthesis, and animals consume glucose (it is the first reactant for cellular respiration).
Animals are the same as humans as far as breathing in oxygen and breathing out carbon dixoide. In order for plants to grow they need carbon dioxide in order to complete the process of photosynthesis which creates oxygen.