Download Natural selection: Survival of the Fittest Sponge

Natural selection: Survival of the Fittest Sponge
Natural selection is one of the basic mechanisms of evolution, along with mutation, migration, and genetic drift.
It is a mechanism by which populations adapt and evolve. In its essence, it is a simple statement about rates of
reproduction and mortality: Those individual organisms who happen to be best suited to an environment
survive and reproduce most successfully, producing many similarly well-adapted descendants. After numerous
such breeding cycles, the better-adapted are more prevalent. Nature has filtered out poorly suited individuals
and the population has evolved. (American Museum of Natural History)
Another definition: It is the process by which living things having traits that better enable
them to adapt to specific environmental pressures, as predators,changes in climate, or competition for food or m
ates, will tend to survive and reproduce in greater numbers than others of their kind,
thus ensuring the perpetuation of those favorable traits in succeeding generations. (Dictionary.com)
There is variation in traits.
For example, some beetles are green and some are brown.
There is differential reproduction.
Since the environment can't support unlimited population growth,
not all individuals get to reproduce to their full potential. In this
example, green beetles tend to get eaten by birds and survive to
reproduce less often than brown beetles do.
There is heredity.
The surviving brown beetles have brown baby beetles because this trait has a
genetic basis.
End result:
The more advantageous trait, brown coloration, which allows the beetle to have more
offspring, becomes more common in the population. If this process continues, eventually,
all individuals in the population will be brown.
If you have variation, differential reproduction, and heredity, you will have evolution by natural
selection as an outcome. It is as simple as that.
Adapted from Understanding Evolution http://evolution.berkeley.edu/evolibrary/article/evo_25