Biological Evolution
Standard B – 5.1
Standard B-5
The student will
demonstrate an
understanding of
biological evolution
and the diversity of
life.
Indicator B – 5.1:
Summarize the
process of natural
selection.
Key Concepts
• Biological evolution: microevolution,
macroevolution
• Natural Selection
• Overproduction of offspring
• Variation: inherited traits
• Adaptation: fitness, survival of the fittest
• Descent with modification
What You Already Know!
In the 6th grade, you
summarized the basic
function of the structures of
animals that allow them to
defend themselves, to
move, and to obtain
resources. In the 8th grade,
you explained how
biological adaptations of
populations enhance their
survival in a particular
environment.
What You Should Understand
After This Lesson
• What biological evolution is.
• The difference between microevolution
and macroevolution.
• How biological evolution occurs because
of natural selection.
• The 4 principles of natural selection.
Objective
• Compare microevolution and
macroevolution.
• Summarize the process of natural
selection.
• Explain how changes in the environment
may result in the appearance or
disappearance of particular traits.
Vocabulary
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biological evolution
microevolution
macroevolution
natural selection
variation
adaptation
heritability
fitness
gene pool
population
What is Evolution?
What do you think about when you hear
the word evolution?
Name some things (living or nonliving) that
have changed over time.
Let’s watch a video.
Charles Darwin
Charles Darwin (2-12-1809)
– Developed the theory of
evolution.
– Father of evolution
– Sailed around the world on
a 5-yr. voyage aboard the
HMS Beagle.
• Observed life and
vegetation as well as
collected specimens at
every port to come up
with his hypothesis
about the way life
changes over time.
Charles Darwin
&
Natural Selection
• The Galapagos Islands
– Of all of his stops, this
was the most influential
to the theory.
– Although the islands
were close together,
they had varying
climates.
• The plants and animals
varied from island to
island as well.
– Collected many
samples for further
observation.
How do you Survive?
Darwin concluded that in order to survive,
organisms must be able to adapt to their
environments. Environments are
constantly undergoing change. If the
organisms want to continue to live, they
have to be able to respond to that change.
Some can adapt more easily than others.
This is called fitness. Those that survive,
must be able to pass that adaptation on to
the next generation. This is heritability.
Charles Darwin & Natural Selection
Darwin realized that organisms struggle to
survive.
– Compete for food, space, escaping from
predators, finding a mate, locating shelter
– Only some organisms live long enough to
produce offspring
• The Struggle for Existence
• Survival of the Fittest
Natural Variation
Charles Darwin
argued that
natural variation
is present in ALL
organisms.
Organisms vary in
size, color, shape,
biochemistry,
physiology, etc.
Natural Selection
• Darwin explains natural selection.
– Happens in nature (no human intervention)
– Occurs when organisms with certain
variations survive, reproduce, and pass their
variations to the next generation.
• Organisms without these certain variations
will die and NOT pass them on to their
offspring.
4 Principles of Natural Selection
1. Overproduction of Offspring
2. Variation of Inherited Traits
3. Adaptation
4. Descent with Modification
Overproduction of Offspring
The ability of an
organism to have many
offspring increases its
chances of surviving.
However, it also
increases the completion
for resources. Organisms
tend to produce more
offspring than can or will
survive.
Spider Eggs
Variation of Inherited Traits
Within any population,
variation exists among
the inherited traits of the
individuals. This variation
refers to the phenotype, or
physical trait, of the
individual. This phenotype
can allow an organism to
better gain the resources
they need in order to
survive. These variations
are controlled by both
genes and the
environment.
Adaptation
Adaptations lead to the
increase in frequency of
a particular trait. With
every generation,
organisms with this
favorable trait become
more adapted to their
environment. Those
organisms without the
favorable trait become
less and less in the
population. The gene
pool of a population
can change over time.
Descent with Modification
As the environment of a population changes, the entire
process of natural selection can yield populations with
new phenotypes. Natural selection can produce
populations with different phenotypes from their
ancestors. As long as those successful traits are
beneficial to the organism, they will continue to passed
down.
Two Types of Evolution
Microevolution
• Happens on a small
scale.
• Within a single
population.
Macroevolution
• Happens on a large
scale.
• Transcends the
boundary of a single
species.
Simulation
Let’s look at a well-known example of
natural selection: The Peppered Moth