Hint: Plants are photosynthetic eukaryotic organisms that consist of a cell wall made up of cellulose and make their food by the process of photosynthesis. Animals are multicellular eukaryotic organisms that consume organic material and breathe Oxygen to survive which depends upon plant and various plant materials for their food.
Plants and animals need oxygen where the plant produces food and oxygen with the process of photosynthesis and this food and oxygen is used by animals for their nutrition and the process of respiration. Therefore plants are known as producers that occupy the first trophic level. Animals use oxygen and the food which is prepared by the plants and use it as a source of energy and release carbon dioxide which is used by the plants for the process of photosynthesis. When the animals perform excretion or are degraded after their deaths, the minerals and nutrients from the residues from their bodies are then absorbed by the plants again. In this way, plants and animals are interdependent for food and other various important materials. plants and animals are interdependent in an ecosystem as they are dependent on each other for their survival for basic needs like food, shelter, protection, and propagation.
Additional information: The main consequence of dependence between plants and animals in an ecosystem is the food chain. The plant consumes the dead and decaying matter from the soil for their nutrients and gets consumed by the plant-eating animals for their survival. These plant-eating animals are consumed by the carnivals for their nutrition and survival. When living organisms die they get decomposed and form a part of the soil which is again consumed by the plants and the cycle continues to exist in its way. Plants and animals are dependent for reproduction as there are certain bees that are carriers of pollen and are transferred between flowers. They obtained the nectar of flowers as their nutrients and established a symbiotic relationship between themselves. Some animals act as a carrier of seeds for plant reproduction which is important for survival in a sufficient area.
Note: There are around 80000 species of edible plants on earth among which $90\%$ of the food is consumed by humans which includes only 30 plant species. A snail can sleep for over three years and the slugs consist of four noses. The only animal that can't jump is the elephant and the horns of rhinoceros are made up of hairs.