Transcript Evolution and Adaptation

5.2 Adaptation
1. Explain how a species adapts to
its niche.
2. Describe convergent evolution
and co-evolution, and relate each
to the concept of niche.
3. Predict changes that may occur
in an ecosystem if biodiversity is
reduced
Evolution and Adaptation
• Ecosystems change over time. Mountains rise and
erode, rivers change course, and climate factors such as
temperature and rainfall may vary dramatically.
• A change in the environment will affect the niches of
the organisms in that environment.
– Evolution is a change in the characteristics of a population
of organisms over time. Evolution happens when some
individuals have genetic variations that allow them to produce
more offspring than other members of the population. Over
time, these changes, or adaptations, will be passed from
generation to generations.
Evolution and Adaptation
• ... our ancestors had larger jaws, so there was room in
the human mouth for 32 permanent teeth, including
third molars—wisdom teeth. But now our jaws are
smaller. The result: There’s no longer room in most of
our mouths to house 32 teeth. So the last teeth we
develop—our wisdom teeth—often become impacted,
or blocked from erupting.’2
Evolving in a Niche
• Evolution causes populations of organisms to
be adapted to specific niches in the
environment. This reduces competition with
other species.
• Ecologists call an organism with a small niche a
specialized species. The koala is an example
of a specialized species. It feeds only on the
leaves of the eucalyptus trees. Specialized
species are often vulnerable to extinction.
Evolving in a Niche
• Ecologists call a species with a wide niche a
generalized species. A generalized species has
several alternate food sources and is more likely
to survive in a changing environment.
– Generalized species such as mice or cockroaches
survive well in areas altered by human activity
because they can easily change their behaviors to fit
new environmental conditions.
Convergent Evolution
• The independent development of similar
adaptations in two species with similar niche is
called convergent evolution. The wings of
birds and bats are an example of convergent
evolution. Birds and mammals are different
types of animals, and the bird and bat evolved
flight independently. However, both species
evolved wings as an adaptation to a niche that
required flying through the air.
Convergent Evolution
Co-evolution
• Species that interact closely may become adapted to
one another through a process called co-evolution.
– Co-evolution can occur as a result of feeding relationships.
Plants and caterpillars are an example of co-evolution. Many
plants have poisonous chemicals that prevent insects from
eating them. Some caterpillars have the ability to resist these
poisons. They can feed on plants that other insects cannot
eat. These caterpillars often become specialized and feed
only on the poisonous plants. The plant and caterpillar have
co-evolved: As the plant adapted to producing poisonous
chemicals, the caterpillar adapted by resisted them.
Homework
Find three species that have gone through an
adaptation process. List the three species, their
adaptations, and the cause of their adaptation –
changes in the environment.