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Evolution Part II
Mrs. Cabak and Mrs. Osakwe
Campbell Middle School
Life Science
th
7
grade
How does Natural Selection
affect the evolution of species on
Earth?
COEVOLUTION
The evolution of two or more
species that is due to mutual
influence, often in a way that
makes the relationship more
mutually beneficial…
The ant and acacia tree are
examples: the ant protects the
tree and the tree has special
structures that make food for
ants.
Flowers and pollinators are also
examples of coevolution.
Flower and
pollination
PUNCTUATED EQUILIBRIUM
The theory that speciation occurs in
spurts of major genetic alterations
that punctuate long periods of little
change. Punctuated equilibrium is a
model of evolution in which short
periods of drastic change in
species, including mass extinctions
and rapid speciation, are separated
by long periods of little or no
change.
NATURAL SELECTION
The process by which Individuals
that are better adapted to their
environment survive and
reproduce more successfully
than less well adapted
individuals do; a theory to
explain the mechanism of
evolution. There are four parts:
overproduction, inherited
variation, struggle to survive,
and successful reproduction.
VARIATION
Marked difference or deviation from the normal or recognized form, function or
structure. Darwin noticed that the animals and plants on the Galápagos Islands were
a lot like those in Ecuador. However, they were not exactly the same. The finches of
the Galápagos Islands, for example, were a little different from the finches in Ecuador.
And the finches on each island differed from the finches on the other islands. The
beak of each finch is adapted to the way the bird usually gets food.
ADAPTATION
An alteration or adjustment in structure or
habits, often hereditary, by which a species
or individual improves its condition in
relationship to its environment.
Populations constantly undergo natural
selection. After two groups have separated,
natural selection may act on each group in
different ways. Over many generations, the
separated groups may evolve different sets
of traits. If the environmental conditions
for each group differ, the adaptations in the
groups will also differ.
SPECIATION
The evolutionary formation of
new biological species, usually by
the division of a single species
into two or more genetically
distinct ones. Speciation often
begins when a part of a
population becomes separated
from the rest. The process of
separation can happen in several
ways. For example, a newly
formed canyon, mountain range,
or lake can divide the members
of a population.
GEOGRAPHIC (ALLOPATRIC) SPECIATION
Evolution of
two or more
species from a
single species
following
geographic
isolation.
GRADUALISM
The view that speciation
proceeds by
imperceptibly small,
cumulative steps over
long periods of time
rather than by abrupt,
major changes.
ABSOLUTE (RADIOISOTOPE) DATING
Scientists can determine the age of a fossil more
precisely. Absolute dating is a method that
measures the age of fossils or rocks in years. In one
type of absolute dating, scientists examine
atoms. Atoms are the particles that make up all
matter. Atoms, in turn, are made of smaller
particles. Some atoms are unstable and will decay
by releasing energy, particles, or both. When an
atom decays it becomes a different, and more
stable, kind of atom. Each kind of unstable atom
decays at its own rate. The time it takes for half of
the unstable atoms in a sample to decay is the halflife of that type of unstable atom. By measuring the
ratio of unstable atoms to stable atoms, scientists
can determine the approximate age of a sample of
rock.
RELATIVE DATING
The proper chronological placement of a feature,
object, or happening in the geologic time scale
without reference to its absolute age. Sedimentary
rock has many layers. The oldest layers are usually
on the bottom. The newest layers are usually on
the top. The layers can tell a scientist the relative
age of fossils. Fossils found in the bottom layers are
usually older than the fossils in the top layers. So,
scientists can determine whether a fossil is older or
younger than other fossils based on its position in
sedimentary rock. Estimating the age of rocks and
fossils in this way is called relative dating.
FITNESS
The extent to which an organism is adapted to or able to produce
offspring in a particular environment.