CBSE Class 10 Science 2020 · Paper 31/3/2 · Question 19(a)

(a) An ecosystem is made up of all the interacting organisms of an area (biotic components) together with the non-living components of their environment (abiotic components); the living and non-living components interact with each other. (b) Autotrophs trap solar energy and convert it into food (chemical energy) by photosynthesis. All other organisms depend on them for food, directly or indirectly, so they form the first level and pass the food energy on to the next level of the food chain. (c) Grass $\to$ insects $\to$ frogs $\to$ snakes: frogs are at the third trophic level and are secondary consumers (carnivores).