Observe evolution in action. Simulate how populations adapt to environmental pressures over generations.
Natural selection is the process by which organisms better adapted to their environment tend to survive and produce more offspring. This fundamental mechanism of evolution was first described by Charles Darwin in his 1859 book "On the Origin of Species."
Key Insight: Natural selection acts on existing variations in a population. It does not create new traits but favors those that provide a survival or reproductive advantage in a specific environment.
Variation: Individuals in a population vary in their traits. This variation arises from genetic mutations and recombination during reproduction.
Inheritance: Traits are passed from parents to offspring. The genetic basis of traits ensures that advantageous characteristics can be inherited.
Selection Pressure: Environmental factors create challenges that affect survival and reproduction. These pressures determine which traits are advantageous.
Time: Over many generations, advantageous traits become more common in the population, leading to evolutionary change.
| Type | Description | Example |
|---|---|---|
| Stabilizing Selection | Favors intermediate variants and acts against extreme phenotypes | Human birth weight - very small or very large babies have lower survival rates |
| Directional Selection | Favors one extreme phenotype over the mean or other extreme | Peppered moth coloration during the Industrial Revolution |
| Disruptive Selection | Favors extreme phenotypes over intermediate ones | African seedcracker finches with small or large beaks, but not medium |
| Sexual Selection | Selection based on mating advantages rather than survival | Peacock tail feathers or deer antlers used in mating displays |
Peppered Moths: During the Industrial Revolution in England, tree trunks became darkened by soot. Dark-colored moths, which were previously rare, became more common as they were better camouflaged against predators.
Darwin's Finches: On the Galapagos Islands, different species of finches evolved different beak shapes adapted to the specific food sources available on each island.
Antibiotic Resistance: Bacteria can evolve resistance to antibiotics when exposed to them. Bacteria with mutations that provide resistance survive and reproduce, passing on the resistance genes.
HIV Evolution: The human immunodeficiency virus (HIV) evolves rapidly within infected individuals, making it difficult for the immune system to control and for treatments to remain effective.
Misconception: "Evolution is just a theory."
Correction: In science, a theory is a well-substantiated explanation of some aspect of the natural world. Evolution is both a fact (populations change over time) and a theory (the explanation of how and why this happens).
Misconception: "Natural selection produces perfect organisms."
Correction: Natural selection produces organisms that are well-adapted to their specific environment, not perfect ones. Traits are often compromises between competing demands.
Misconception: "Evolution has a goal or direction."
Correction: Evolution is not progressive or goal-oriented. It simply favors traits that work in a given environment at a given time.
In this simulation, creatures vary in a single trait (e.g., speed, camouflage, or size). The environment favors certain trait values, causing the population to evolve over generations.