What is ecological hierarchy? Name the levels of ecological hierarchy.

Study the food chain below, correct it and convert it into a pyramid of energy.

$Mulberry\to Sparrow\to Caterpillar\to Kite.$

For thousands of years the human population on the earth increased very slowly.

In the year 10,000 BCE, the estimated population was 50 million.
In 1700 CE, the population was only about 1 billion. Then it started accelerating very fast.
In 2000 CE, it had crossed 6 billion.
By 2050 CE, it is expected to cross 9 billion. What do you think has caused the huge increase?
 

Name four shelters used by animals.