Question

What do you understand by natural selection? Give examples.

Answer 1

Natural selection is a natural process in which organisms that are better adapted to their environment tend to survive and reproduce more than those that are less adapted.

Complete answer:
Natural selection is an important evolutionary mechanism. It states that nature selects organisms that can survive and reproduce in changing environmental conditions, while organisms that cannot survive are eliminated. The genes responsible for an organism's survival are passed down through generations.
To begin, most organisms' characteristics are inherited, or passed down from parent to offspring, though how traits were inherited was unknown. Second, more offspring are born than can survive. All organisms' reproductive capacity exceeds the availability of resources to support their numbers.
Treefrogs, for example, are occasionally eaten by snakes and birds. Gray Treefrogs blend well in dark wooded areas on tree bark, and Green Tree Frogs blend well in marshes and swamps. A Green Tree Frog on the bark of a tree is easier to find than a Green Tree Frog on a green leaf.Green Tree Frogs that venture into uncamouflaged habitats are thus more likely to be eaten by predators. Because eaten Tree Frogs do not live to have more baby Tree Frogs, natural selection has favoured Tree Frogs that live in more camouflaged habitats.
This helps to explain the geographic distribution of Gray and Green Tree Frogs. The Grey Tree Frogs wooded habitat is larger and extends further north, whereas the Green Tree Frogs swamp and marsh habitat is concentrated in the south. Both habitats are present in the area where Gray and Green Treefrogs overlap, but in different locations.
Giraffes are thought to have had shorter necks. Their feeding habits caused their necks to grow longer, and the genes from such animals were passed down to future generations. The evolution of the giraffe we see today took millions of years. Natural selection causes a population to become more adapted to its local environment; it is the only mechanism known for adaptive evolution.

Note:
To put it another way, natural selection is a process that results in some animals and plants being better adapted to their natural environment than others. Those plants and animals have a better chance of survival, reproduction, and population growth than those that are less adapted to their environment. As a result, better adapted plants and animals can pass on their advantageous characteristics (coded for by genes) to their offspring via inheritance.