Which one of the following words has been used by Prof. R. Misra for ecosystem

Mulching helps in

Agrostology is related with the study of

Find out the population density when $N$ is $1000$ and $S$ is $100\, m ^{2}$

$I.$ Many xerophytic plants have thick cuticle on leaf epidermis and sunken stomata

$II.$ Some xerophytic plants have special photosynthetic pathway $(CAM)$ that enables their stomata close during day

$III.$ Opuntia has spines (modified leaves), photosynthetic phylloclade (stem)

$IV.$ All adaptations are genetically fixed in all organisms

Choose the combinations of correct option