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Unit 5: Biological Evolution
Unit 5: Biological Evolution
Standard B – 5: The student will demonstrate an understanding of biological evolution and
the diversity of life.
This unit is about Biological Evolution and will answer the following questions:
 What is Biological Evolution?
 What is Natural Selection?
 Why is variation among organisms important for Biological Evolution?
 What evidence is there to support Biological Evolution?
 What do scientists use to construct Phylogenetic Trees?
 What do Phylogenetic Trees show us about how living things are related?
Unit 5 Test: _______________________
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Unit 5: Biological Evolution
Natural Selection
What do you think of when you think about evolution?
What are some things (living or nonliving) that have changed over
time?
___________ _____________ is considered the Father of Evolution. He developed the theory after
many years of research and collecting data. He traveled all over the world aboard a ship called the
______________. Of all of his stops, the ________________ _____________ were the most
influential in his research. Here he noticed _________ among the species of the islands. This
____________ seemed to correspond to the needs the environment provided. For example, the
tortoises on islands where the food was higher off the ground had long necks, whereas tortoises on
islands where the food was on the ground had short necks. What other things did he observe on his
voyage?
Darwin was able to conclude that species must ___________ to their environment in order to survive.
This is called _____________ ______________. In order for this to occur, there must be _________
among the species within the population. Some organisms are better suited to meet their needs in the
environment. This is called ____________. In order for their offspring to be able to survive in the
same environment, with the same conditions, they have to be able to pass those traits to them. This
is called ____________. Darwin also proposed that there is a struggle to survive due to
overpopulation and limited resources. This concept is often referred to as survival of the fittest.
Beneficial adaptations arose over many generations.
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Unit 5: Biological Evolution
NATURAL SELECTION EXPLAINS HOW BIOLOGICAL EVOLUTION OCCURS.
There are 4 main principles.
1) Overproduction of Offspring

The ability of a population to have many _____________ raises the changes that some will
___________ but also increases the competition for _____________.
2) Variation of Inherited Traits

Within every population, variation exists among ___________ ____________ of the
individuals.

Variation exists in the ____________ of the individuals within every population.

An organism’s _____________ may influence its ability to find, obtain, or utilize its
resources and also might affect its ability to reproduce.

Variations among organism’s _____________ is controlled by the organism’s genotype and
the environment.
o Those with beneficial phenotypes survive, reproduce, and pass them on to their
offspring. Those that don’t have them, end up dying.
3) Adaptation

The process of ______________ leads to the increase in frequency of a particular
structure, physiological process, or behavior in a population of organisms that makes the
organisms better able to survive and reproduce.
o With every generation, organisms with specific beneficial inherited traits become
more ______________.
o As each generation progresses, those organisms that carry genes that hinder their
ability to meet day-to-day _________ become less and less prevalent in the
population.

Those without a particular _________ to their environment will be less likely
to find resources, live, and reproduce. Therefore their unbeneficial traits will
NOT be passed to the next generation.
o The ________ _________ of a population can change over time due to this.

The concept of ___________ is used to measure how a particular trait contributes to
reproductive success in a given environment and results from _____________.
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Unit 5: Biological Evolution
4) Descent with Modification

As the ____________ of a population changes, the entire process of ____________
__________ can yield populations with new phenotypes adapted to new conditions.

l____________ ___________ can produce populations that have different structures, live
in different niches or habitats from their ancestors. Each successive living species will have
descended, with modification, from previous generations.

More individuals will have the successful ________ in successive generations, as long as
those _________ are beneficial to the environmental conditions.
Explain how this picture represents the 4 Principles of Natural Selection
Two Types of Evolution
Microevolution
Macroevolution
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Unit 5: Biological Evolution
Genetic Processes Contribute to Biological Evolution
Use your textbook and previous knowledge to complete the comparison chart below on reproduction.
Sexual Reproduction

.Results in genetically unique offspring.





Uses the process of meiosis to create
gametes.


Asexual Reproduction


Will have a higher chance of survival in a
changing environment due to all
organisms being genetically unique. This
means they will all respond different to
changes in the environment.
Involves 1 parent, with one set of genes.
The only method of achieving genetic
variability in offspring is through a mutation
in the DNA.


Reproduction rate is much higher.
Question for Thought
What if every single organism on Earth had exactly the same DNA and reproduced asexually?
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Unit 5: Biological Evolution
Genetic Diversity
A population shares a common __________ __________.
There is great ___________ __________ among the individuals
within a population.

This leads to __________ variation.
o This is necessary for ___________ __________
to occur.

This is stored in the population’s ____________ __________.

Measured by ____________ ______________.
o Measures how common an allele is in a population.
o Can be calculated for each allele in a gene pool.
Example:
In a crop field growing on the outside of the city, you can find 5000 pea plants. Within that population
of pea plants, there are both tall and short plants. The following is what you know about their
genotypes:
Genotype
# of Individuals
TT
Tt
tt
Total
2156
1736
1108
5000
Genotypic
Frequency
TT:
Tt:
tt:
Phenotypic
Frequency
Tall:
Allele Frequency
T:
Short:
t:
Show your work in the space below.
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Unit 5: Biological Evolution
There are many ways for genetic variation to occur within a population. Read about the following and
fill in the chart.
Mutations
Recombination
Hybridization
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Unit 5: Biological Evolution
Genetic Variability Leads to Biological Evolution
Mechanisms of Evolution
Natural Selection is the ______________ mechanism of biological evolution.
- There are many _________ that can lead to biological evolution.
Factors that Affect Genetic Variability
Genetic variation is ____________ and ensures that each new __________ will result in individuals
with ________ genotypes and phenotypes. This leads to ____________ _____________.
- There are many factors that can lead to genetic variability.
1.
4.
2.
5.
3.
Gene Flow
- The __________ of alleles between _____________.
- Occurs when individuals join new ___________ and ____________.
- Keeps _____________ populations similar.
- Low gene flow increases the chances that __ ________ will evolve into different ____.
Genetic Drift
- A ________ in allele __________ due to chance.
- Causes a loss of _________ __________.
- Most common in __________ populations.
Non-Random Mating
- __________ has an important effect on the evolution of a population.
- ___________ produce many ________ continuously, making the value of each _____.
- ________ produce less ________, so they are choosy about who they ______ with.
- limits the frequency of the ________ of certain __________
Mutations
- A change in the _________ of an organism.
DNA  ________  Protein  _________
- Increases the _________ and types of allele changes within a population.
Natural Selection
- The main ___________ to biological evolution.
- Allows for the most _______ phenotypes to survive & be passed to future generations.
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Unit 5: Biological Evolution
Hardy-Weinberg Equilibrium
Biologists use __________ to study populations.
Provides a ___________ for understanding how _________ evolve.
Describes populations that are NOT ____________. This means the __________ are staying the
same.
Has 5 conditions that must be met:
1.
2.
3.
4.
5.
Speciation
The process of forming a new _________ by biological evolution from a pre-existing species.
Can arise when species become _____________.
- Populations become ___________ when there is no ______ _________.
- Isolated populations ___________ to their own ____________.
- Genetic ____________ can add up over many generations.
- Can happen in a number of ways.
Reproductive
Geographic
Behavioral
Temporal
Isolation
Isolation
Isolation
Isolation
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Unit 5: Biological Evolution
Environmental Factors Lead to Biological Evolution
Catastrophic Events
Examples:
Climatic Changes
Examples:
Continental Drift
Examples:
Patterns of Evolution
There are many patterns to how evolution can occur.
- __________________________
- ___________________________
- __________________________
- ___________________________
- __________________________
- ___________________________
- __________________________
Let’s look at some examples.
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Unit 5: Biological Evolution
Evidence of Biological Evolution
Evidences of Evolution
Evidence of ___________ ancestry among ___________ comes from many _________.
Four main evidences:
1.
2.
3.
4.
Fossils (Paleontology)
* Paleontology is the study of ____________ ________.
* Provides valid evidence of _______ ________ and ____________ changes
over time.
* Comparing current and ancient _________ shows a _________ of gradual
________.
* Tells a ________ of the types of ________ that lived on _________.
Comparative Anatomy
* The study of the _________ of ___________.
* Studying anatomical ______________.
- Homologous Structures : Same ___________, Different _____________
- Analogous Structures: Same ______________, Different ________________
- Vestigial Structures: Structures that no longer ___________ a purpose.
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Unit 5: Biological Evolution
Embryology
* The study of l_________ development of _________.
* Comparing the anatomies of ___________.
- An early stage of an organism:
* Pre-Birth
* Pre-Hatching
* Pre-Generation
Biochemistry (Molecular Biology)
* Comparing the __________ and
____________ of organisms to look for ________.
* Studies ________ and ___________ to provide _________ for biological evolution.
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Unit 5: Biological Evolution
Phylogeny
Organization of Evolutionary Evidence
Once various sources (fossils, anatomy, embryology, and biochemistry) of information have been
analyzed, scientists attempt to determine the ____________ of a species, or its evolutionary history.
Once the phylogeny is determined, a ______________ tree is constructed which shows how living
things are related to one another. Scientists don’t rely on only one piece of information to ensure an
accurate picture of the history of the evolution of a particular group of organisms. The more evidence
they can gather, the more reliable their hypotheses are about how living things are related.
Field of Paleontology
 The _____________ _____________ provides information regarding the dates and order of
____________ for phylogenies.
 ____________ fossils are fossils that show links in traits between groups of organisms used to
document intermediate stages in the evolution of a species.
o They _________ evolutionary relationships.
 The biggest challenge of using fossils to determine phylogenies is that the fossil record is
_____________. There are many reasons it is incomplete.
Field of Biochemistry
 _____________ can be constructed by assuming that differences in _______, ________, and
other _________ increase over time. The ________ the overall genetic _____________, the more
recently a pair of species shares a common ancestor.
 The time since a pair of species has diverged can be estimated under the assumptions of a
“__________ _________”.
 Even though a comparison of the _______ sequences of 2 species provides some of the most
reliable ____________, there are challenges with this approach.
Field of Anatomy
 ________________ can be constructed by assuming anatomical differences ___________ with
time. The more ____________ 2 organisms are anatomically, the more ___________ related they
are.
o The accumulation of differences over time is called ___________.
o Anatomical structures that share a common form but not a common function are
______________. They show common ancestry.
 Evolutionary biologists study anatomy to help them create _______________.
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Unit 5: Biological Evolution
 Sometimes structures or organisms may suggest a common ancestry since they are similar in
shape and function but in fact they are not from a common ancestor. This is only a result of two
separate species adapting to similar environments over time.
o This is called ________________. Structures with similar functions but different structures
are called _____________. They DO NOT show common ancestry.
Field of Embryology
 The development of ___________ allow scientists to construct phylogenies between different
groups of organisms that may have such different anatomical structures that it’s difficult to
compare otherwise.
Taxonomy & Phylogenetic Trees
There are _________ domains of life on earth.
All living things are classified into 1 of these
domains of life. Under each domain,
organisms are further classified – based on
the evidences gathered to create phylogenies.
There is a hierarchal structure of classification
(taxonomy) of organisms:
>
>
>
>
>
>
>
A _____________ ____________ is a scientific diagram that biologists use to represent
____________. It classifies organisms into major _________ based on evolutionary relationships.
They are used to classify species in the order in which they descended from a common ancestor.
Speciation could be thought of as a branching of a family tree then extinction is like the loss of one of
the branches.
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Unit 5: Biological Evolution
Some phylogenetic trees only express the order of divergence of a species. They don’t show time.
Some phylogenetic trees indicate an estimated time
of divergence.
Which groups are most closely related?
Which groups are least closely related?
Which groups diverged first (longest ago) in the lineage?
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