Loading biol110..

Natural selection is a process by which a population becomes better adapted to its' environment over time (a more succinct definition of natural selection is “differential reproduction” – the best adapted individuals are more likely to reproduce then less well adapted individuals – these better adapted individuals pass on more of their genes to the next generation than individuals without these advantageous traits).  However, environments are always changing and thus the adaptations in an environment also change.  Changing environments drive evolution via natural selection.

For natural selection to act upon a population, there must be certain conditions: 

• First, there must be an overproduction of individuals that results in competition for resources and a struggle for existence (in other words, there are more individuals than resources to support these individuals). 
• Second, there also must be variation within the population - a population of identical individuals cannot be acted upon by natural selection. 
• Third, the variation must be heritable (in other words, due to genes). Natural selection can only act on available genetic variation within a population at any given time. 

It is also important to note that natural selection can only cause organisms to adapt to the environmental conditions at that time. If the environment changes, then the selective pressures may change, and different genetic traits may be favored.

Watch this video from TED-ED on some of the most common myths and misconceptions about evolution and then answer the questions that follow. 

To watch this video on YouTube (and see closed captioning) - press the arrow icon in the bottom right corner of the video player.

Now test your understanding with these practice problems: