Organisms vary.
They look different.
Don't believe me?
Go outside and look around.
Still don't believe me?
Grab a ruler.
Measure some leaves.
They'll be different.
This is a rabbit.
Some rabbits are slightly darker than others,
some are slightly lighter.
Some of the variation we see
gets passed down to offspring.
Offspring tend to look like their parents.
More offspring are born
than can be supported by the environment.
In other words,
things die.
Some things get eaten by predators.
Some get sick and die.
Some just get unlucky
and get hit by cars.
Some of the variation we see
is responsible for determining
who lives and reproduces
and who dies.
Those organisms that are well adapted
to their environment
tend to live and have lots of babies.
Those that are poorly adapted
to their environment
tend to die.
These rabbits live on a white background.
Dark colored rabbits are easier to see
so they tend to get eaten by predators.
Light colored rabbits are harder to see
so they tend to live and reproduce.
Over time, some individuals
survive and reproduce better
than other individuals
because of certain characteristics.
In this example, coat color.
These characteristics get passed down
to their offspring who then
survive and reproduce better than other individuals
and the population can end up looking
quite a bit different than
what it did in the past.
This is evolution by natural selection.
