1. Darwin’s Finches

2. Q:How did Darwin explain these adaptations, or different beaks?
A:Natural selection! 3 main points:
1. Far more offspring are produced than the environment can hold. Overproduction leads to a struggle for existence among the individuals of a population.
2) Individuals in a population vary in many traits - no two individuals are alike.
3) Those individuals with traits best suited to the local environment will have the greatest reproductive success. They will leave the greatest number of surviving, fertile offspring. They will reproduce more of the same. This unequal reproductive success = natural selection.
Nature decides what traits are most fit.
Adaptation is the accumulation of favorable variations in a population over time.
Ex: beaks well equipped for available food sources, and markings that reduce predation = finches survive to produce more. (Survival of the Fittest)
Ex:(See diagram of natural selection in beetles)

3. Darwin also looked at “Artificial Selection” going on with farming.
Humans have been modifying other species for centuries by selecting breeding stock with certain traits.
These vegetables and flowers no longer look like their ancestors.

4. Artificial Selection in pets - have been bred for human fancy.
Dog breeds - all are descendants from one ancestral population
of wolves
“Humans” screened the heritable traits of populations instead of
“nature’” or the natural environment.

5. Natural selection in action today:
Antibiotic-resistant forms of tuberculosis-causing bacteria have made the disease a threat again in the U.S. The lung infection of this patient is shown in red.