Download Examples of Natural Selection

Examples of Natural Selection:
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In a habitat there are red bugs and green bugs. The birds prefer the taste of the red
bugs, so soon there are many green bugs and few red bugs. The green bugs reproduce and
make more green bugs and eventually there are no more red bugs.
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In an ecosystem, some giraffes have long necks and others have short ones. If
something caused low-lying shrubs to die out, the giraffes with short necks would not get
enough food. After a few generations, all the giraffes would have long necks.
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A species of rats live in a certain type of tree with the branches evenly spaced. Smaller
rats could not reach from branch to branch and larger rats would break the branches and fall.
Soon, all rats were just the right size for the tree branches.
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Deer mice that migrated to the sand hills of Nebraska changed from dark brown to light
brown over several generations, to better hide from predators in the sand.
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Galapagos finches all have different types of beaks. During drought, the finches with the
larger beaks survived better than those with smaller beaks. During rainy times, more small
seeds were produced and the finches with smaller beaks fared better.
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In one ecosystem, lizards that had long legs could climb better to avoid floods and reach
food.
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Insects become resistant to pesticides very quickly, sometimes in one generation. If an
insect is resistant to the chemical, most of the offspring will also be resistant. Considering that
insect generations can be a matter of weeks, insects in an area can become immune to a
chemical within months.
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The bacterium Pseudomonas metabolizes nylon; but, when a certain type of this
bacterium that did not eat nylon was placed in an environment where nylon was the only food,
the bacterium evolved until it ate the nylon.
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Peacock females pick their mate according to the male’s tail. The ones with the largest
and brightest tails mate more often. Today, males that do not have bright feathers are very
rare.
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The peppered moth used to be a light color with black spots. When the atmosphere in
London became filled with soot because of the Industrial Revolution, the white trees became
darker and light colored moths were eaten by birds more readily. Within months, moths
became darker and lighter moths were rare. After the Industrial Revolution, light colored moths
were found in greater numbers.
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Rat snakes are all very similar except in coloring. Some are striped and some are green,
black, and orange. This is due to living in many different types of terrain and adapting to the
environment.
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Warrior ants have a chemical signal that tells other ants in the family not to attack.
Some have adapted and learned to imitate the chemical signal from other colonies so they can
invade and take over another colony and the workers will never know.
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Sharks are colored white on the underside and blue or gray on the top. This is their
camouflage as the top blends with the water color to someone looking down into the water
and the bottom blends with the light coming through the water from above.
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Bacteria have become resistant to antibiotics and this can happen very quickly, since
bacteria can produce several generations within one day. The strongest bacteria are the last to
die and the antibiotics sometimes do not kill all of them.
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The field mustard plant survived a drought in southern California because of genetic
changes that made it produce flowers earlier. Plants that survive a drought have to have a short
growing season and the field mustard evolved quickly.
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Because of its long body, the moray eel’s mouth did not produce enough suction to
catch prey; so, it adapted and grew a second set of jaws and teeth.
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Humans have evolved and are still evolving. There are people more resistant to malaria
that live in Africa.
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Humans don’t become lactose intolerant as some species do. This is thought to be
because of the domestication of cattle.
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Early humans survived because of a certain hand shape that could either toss a spear or
throw a rock the best.
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In the 18th century, researchers found in an island community where there was a
genetic disposition to mate earlier and have larger families. Over 140 years, the age at first
reproduction dropped from 26 to 22 and this was due to natural selection.