Natural selection
Definition:
Natural selection is the process by which living organisms adapt and change over time. It is one of the fundamental mechanisms of evolution, famously proposed by Charles Darwin in 1859.
At its core, natural selection is simple: individuals with traits that are better suited to their environment are more likely to survive and reproduce. Because they survive longer, they pass those helpful traits on to their offspring, making those characteristics more common in the population over many generations.
Examples:
1. Random Variation: Long ago, giraffe ancestors had short necks, but some were born with slightly longer necks due to random genetic differences.
2. Environmental Pressure: Food on the ground became scarce. The best leaves were high up in the trees.
3. Survival: The "short-necked" giraffes couldn't reach the food and died off. The "long-necked" giraffes ate well and survived.
4. Inheritance: The survivors passed their "long-neck" genes to their babies.
5. Result: Over many generations, the entire species ended up with long necks because that was the only trait the environment allowed to survive.
Natural selection in bacteria and antibiotics:
Bacteria and antibiotics:
Antibiotics are drugs that we can take to kill bacteria that are causing diseases in our body.
There are many antibiotics. But doctors are finding that many antibiotics do not work any more. Bacteria have become resistant to them.
This is what happens:
