1. The lowest velocity used to escape the gravitational pull of the Earth is called escape velocity.

2. The escape velocity of the Earth is 11.2 km/second.

1. Excretion is the process in which all metabolic wastes are passed out of the body. Excretion in humans occurs in several processes through various organs and internal organs of the body.

2. Diffusion is the most common process of excretion in lower organisms. The human body is an extraordinary machine, where various life-processes (respiration, circulation, digestion, etc.) occur simultaneously. As a result, many of the waste products produced in our bodies are in various forms including carbon dioxide, water, and nitrogenous products such as urea, ammonia, and uric acid.

1. Ornithology is a branch of zoology that studies birds. It studies different species of birds, their size, shape, colour, behaviour, habitat, reproduction and other aspects.

2. Ornithologists use a variety of methods to collect information about birds, such as field surveys, bird watching, studying bird behavior, and studying fossils.