Evolution and Natural Selection SURVIVAL OF THE FITTEST

Charles Darwin and Natural Selection Charles Darwin is best known for his contributions to the theory of Evolution On a five year voyage on a ship called the Beagle, Darwin recorded his observations of organisms and fossils he found along the way This led Darwin to develop the idea of evolution and natural selection

Survival of the Fittest “Survival of the Fittest” means that those organisms best adapted to their environment will survive, reproduce, and pass on genes “Fittest” means best adapted, not strongest!

What is an Adaptation? Any heritable trait an organism has that helps it to survive What are some adaptations of this falcon?

Abut Adaptations If an organism does not have adaptations to best fit its environment, it will die “Survival of the Fittest” Example: Bird beaks-Imagine that birds had different sized beaks in an area where the food source was seeds. In order to crack them, the birds needed a large, strong beak. Which would survive and reproduce?

Natural Selection Species have the potential to increase exponentially, but environmental factors maintain lower population numbers Resources required to sustain life Environmental conditions Relationships among organisms in food web Changing environments select for specific phenotypes Those organisms with favorable adaptations survive, reproduce, and pass on their alleles to future generation Over time, the accumulation of favored alleles leads to a change in species (change over time = evolution)

Case Study: Antibiotic Resistant Bacteria Organisms are constantly changing and adapting; bacteria reproduce and evolve quickly to adapt to constant changes! Humans often use antibiotics to combat harmful bacteria (ex. Staphylococcus) Some bacteria are born with a natural resistance (an adaptation!) to the antibiotic These bacteria will survive and reproduce, creating a group that are resistant to the drugs