http://download.elearningontario.ca/repository/1235730000/SBI3UPU03/SBI3UPU03A05/overview.ht
ml
SBI3U: Biology, Grade 11, University Preparation
Unit 3: Evolution
Activity 5: Macro vs Micro Evolution
Overview | Expectations | Content | Assignment
Overview
Now that you understand some of the mechanisms that drive evolution, you will take a look at
evolution on a small scale (micro) and on a large scale (macro). You will learn that evolution may
occur gradually or in spurts. In this activity you will have the opportunity to discuss how humans can
affect the course of evolution.
Content
Macro versus Micro
These two images show a macro scale on the left and a
micro scale on the right. Macro means to have a
broader perspective while micro means to have more of
a close up perspective.
Microevolution
Microevolution refers to the change in frequency of alleles in a population resulting from genetic drift,
gene flow, natural selection, or mutation. Microevolution is the change of a population on a small
scale.
Earlier you saw how the peppered moth was
reduced in number and the black moths increased
in number during the industrial revolution. There
was a change in the frequency of these alleles
after the emission of soot from the coal changed
the environment. This is an example of
microevolution.
Macroevolution
Macroevolution refers to evolutionary change at or above
the species level. This can mean that a totally new
species forms (speciation) or that species can change
into another species (cladogenesis) over time.
Recall that phylogeny is the study of the evolutionary
relations between species. How species are related in
their evolutionary history can be represented by an
evolutionary “tree” which is called a cladogram. A
cladogram shows the hierarchical classification of a
species based on ancestry. The diagram on the right
shows the origin of three domains; Bacteria, Archaea and Eucaryota, together with phya found within
each domain.
Taxon
In order to better understand how one species originates from another, we need to take a look at the
classification of living things. Taxonomy refers to the organization and classification of things in a
hierarchical structure. The classification of living things was put forth by a scientist mentioned earlier,
Carolus Linnaeus. Linnaeus is known as the “father” of taxonomy.
Modes of Selection
Taxonomy of living things
The top of the diagram to the left shows the most specific level and the bottom
shows the least specific level of organization under Linnaeus’s system of taxonomy.
All living things fall into three domains: Bacteria, Archaea, and Eucaryota. Within
these three domains there are six kingdoms of living organisms: Animalia,
Eubacteria, Archaebacteria, Protista, Fungi, and Plantae. These kingdoms are then
further divided into phyla (singular phylum): classes, orders, families, genus, and
then species.
When referring to a particular species, a dichotomous (two-part) name is used that
includes the genus name and the species name. For example, humans are called
Homo sapiens. Homo is the genus name and sapiens is the species name.
Find out more on microevolution and macroevolution, cladograms, and
taxonomy.
Microevolution
Macroevolution
Cladograms
Taxonomy
Portfolio:
Notes help prepare you for tests. Keep all of your notes in your portfolio. Be prepared to submit your
portfolio notes and organizers to your teacher for assessment at various times during the course.
Use your portfolio to make detailed notes on microevolution and macroevolution, cladograms,
taxonomy and any words in bold.
Next
Content
Now that you have been introduced to the terms, let’s look at some of the evolutionary theories of
macroevolution.
Recall that macroevolution is the evolution that creates new species or changes species, while
microevolution is the change within species that results in new allele frequencies.
Evolution is proposed to have taken billions of years. It was first thought to have occurred gradually
over time as one species evolved from another, generating the diversity seen today. This is called
the theory of gradualism. However, one concern with this theory was that if evolution occurred
gradually, there should be fossils of transitional forms of the various species alive today. However,
there are gaps in the fossil records with no gradual form changes, which would suggest that this may
not be how evolution occurs.
Punctuated Equilibrium
Two scientists, Niles Edredge and Stephen Jay Gould, came up
with a theory that addressed this concern. They proposed the
theory of punctuated equilibrium. The theory states:


speciation occurs in isolated populations so transitional
forms are hard to find;

speciation occurs rapidly;

speciation occurs in bursts;
bottlenecks, founder effects, directional selection are the
driving forces.
Find out more on Gradualism and Punctuated Equilibrium.
Gradualism
Paleospecies
Punctuated Equilibrium
Portfolio:
Notes help prepare you for tests. Keep all of your notes in your portfolio. Be prepared to submit your
portfolio notes and organizers to your teacher for assessment at various times during the course.
Use your portfolio to make detailed notes on gradualism, fossil record and punctuated equilibirum.
Check Your Understanding
Identify each of the following as an example of macroevolution or microevolution. Tell if it supports the
theory gradualism or punctuated equilibrium.
1.
The Cambrian explosion (a period of rapid evolutionary change where many complex
organisms evolved).
Answer
2.
The evolutionary change of animals and terrestrial plants.
Answer
3.
Beetles with a green sheen are more prevalent than beetles with a black sheen.
Answer
Back