BIOLOGY CH16 EVOLUTION
10pts
NAME_____________________________
ESSENTIAL QUESTIONS
1. Who was Charles Darwin and what is his theory of Descent with Modification?
2. What is Evolution and how do mutations allow it to happen?
3. Are humans still evolving? Why or Why not?
4. Why is the concept of Evolution just a theory and not considered a Scientific Law?
What is the difference between these two types of Scientific Certainty?
BIOLOGY CH16 EVOLUTIONARY THEORY
NAME______________________
BRIEFLY DESCRIBE THE FOLLOWING SCIENCETISTS INFLUENCE ON
DARWIN’S THINKING
1. LAMARCK
2. LYELL & HUTTON
3. CUVIER
4. MALTHUS
5. DEFINE NATURAL SELECTION
WHAT ARE THE 4 STEPS OF EVOLUTION THROUGH NATURAL SELECTION?
BRIEFLY DESCRIBE EACH:
6.
7.
8.
9.
10. WHAT FIELDS OF SCIENCE DOES DARWINS IDEA UNIFY?
BIOLOGY CH16 EVOLUTION
NAME_____________________________
15pts Feel Free to use the power-point (Found on the calendar)or any materials I
have given you to answer the questions.
ESSENTIAL QUESTIONS
1. What are the 5 types of evidence used to support the theory of evolution? Give a brief
definition with examples for each
a.
b.
c.
d.
e.
2. What is an Adaptation?
3. What are the three types of Adaptations and describe each with an example
a.
b.
c.
4. What is Speciation and how does it happen?
5. What are the 5 types of evolution? Give an example for each
a.
b.
c.
d.
e.
BIOLOGY CH16 VOCABULARY
CHARLES DARWIN : The Father of Evolution through Natural Selection, he observed change through
“Descent with Modification.” Wrote on the Origin of Species in 1859
SPECIES : Organisms so similar they can interbreed and produce VIABLE (fertile) offspring
NATURAL SELECTION: greater reproductive success displayed by individuals with ADAPTIVE traits
VARIATION: differences within a population
ADAPTATIONS: traits that are selected for because they help an organism survive and reproduce
EVOLUTION: Changes in species over time- Occurs when genes in a population change/shift to
enhance survival and reproduction
JEAN BAPTISTE LAMARCK: Observed organisms change/evolve by passing down AQUIRED TRAITS
LYELL AND HUTTON: Geologists who proposed GRADUALISM as the source of change
CUVIER: Geologist who proposed CATASTROPHISM as the source of change
EVIDENCE FOR EVOLUTION: Comes from Fossils, Comparative Anatomy, Embryology, Biochemistry,
Biogeography, and others!
EVIDENCE FOR EVOLUTION
FOSSIL EVIDENCE: Records of past organisms show common ancestry
COMPARATIVE ANATOMY: the study of similarities in organisms of common ancestry
Vestigial Structures- appendix, whale pelvis
Analogous Structures – bee wing v. bird wing
Homologous structure - your hands-whale flipper
EMBRYOLOGY: The study of how embryos develop to show common ancestry- you had gills and a tail!
BIOCHEMISTRY: The similarity in gene sequence
BIOGEOGRAPHY: The study of how organisms are distributed today and in the fossil record
3 TYPES OF ADAPTATIONS
STRUCTURAL ADAPTATIONS: Physical feature like a wing to fly or fins to swim
PHYSIOLOGICAL ADAPTATION: Body functions like the production of venom or the ability to tolerate heat
BEHAVIORAL ADAPTATION: When organisms work together like a wolf pack, or school of fish
3 TYPES OF NATURAL SELECTION
DIRECTIONAL SELECTION: When a direction in phenotypes is favored- bigger brains
STABILIZING SELECTION: When 1 average phenotype is selected for – 7lb babys
DISRUPTIVE SELECTION: When 2 extreme phenotypes are selected for simultaneously- different colored
butterflies
SPECIATION: The formation of new species through evolution
5 TYPES OF EVOLUTION
DIVERGENT: When new species are formed that have different features- Tiger & Lion
CONVERGENT: When species change to be similar to other species- Kangaroo & Deer
ADAPTIVE RADIATION: When species form to fill new or open ecological niches- Darwin’s Finches
COEVOLUTION: When species evolve together and rely on one another for survival- birds & flowers
EXTINCTION: When species evolutionary sequence ends-99% of all species over time have become extinct
EVOLUTION
BIO.B.3.1.1: Explain how natural selection can impact allele frequencies of a population.
BIO.B.3.1.2: Describe the factors that can contribute to the development of new species (isolating mechanisms, genetic drift, founder effect,
migration).
BIO.B.3.1.3: Explain how genetic mutations may result in genotypic and phenotypic variations within a population.
BIO.B.3.2.1: Interpret evidence supporting the theory of evolution (fossil, anatomical, physiological, embryological, biochemical, and genetic
code).
BIO.B.3.3.1: Distinguish among the scientific terms: hypothesis, inference, law, theory, principle, fact, and observation.
BIO.B.1.2.1: Describe how the process of DNA replication results in the transmission and/or conservation of genetic information.
BIOCH16
NAME_________________________
POWERPOINT OUTLINE
Chapter 16 Evolution
ESSENTIAL QUESTIONS
Who was Charles Darwin and what is his theory of Natural Selection
What is Evolution and how do mutations allow it to happen?
Are humans still evolving?
Why or Why not?
Why is the concept of Evolution just a theory and not considered a Scientific Law?
What is the difference between these two types of Scientific Certainty?
Chapter 16 Evolution
Charles Darwin is the father of evolutionary theory!
MUTATIONS are natural changes in organisms, occasionally(very rarely,) they’re beneficial.
Humans are still evolving-here’s a photo of me from high school. Just kidding…INDIVIDUALS can’t evolve!….but our species is.
Evolution is a theory but some believe it may be the most influential in modern scientific thought because of its very broad
implications
Emergence of Evolutionary Thought
Evolution is the process by which SPECIES change over time.
A Theory is a BROAD explanation that has been tested and supported.
Like most theories, evolutionary theory keeps developing and expanding.
Most of Darwin’s ideas remain scientifically supported.
The Emergence of Evolutionary Thought
Early Explanations of life’s diversity
If species were individually and perfectly created at one time and one place
Then….
Why were organisms different in different regions of earth?
Why are current organisms different from ancient organisms?
If each species is different, why are there the same fundamental structures and body plans to do different things in animals?
Charles Darwin 1809-1882
Charles Darwin was the NATURALIST aboard the HMS Beagle. His job was to collect animals and plants for identification and
potential commercial value.
The Beagle’s mission was to map the ports of South America. They left in 1831 and returned 5 years later in 1836.
Charles Darwin 1809-1882
Darwin witnessed a tremendous diversity of animal life both living and FOSSILIZED
He traveled to the Galapagos Islands and collected a bunch of different birds, but it turned out they were all FINCHES!
He became convinced that species change over time
Darwin’s Influences
Darwin was influenced by a number of Scientists and their thoughts including:
Jean Baptiste Lamarck
Thomas Malthus
Charles Lyell & James Hutton
Georges Cuvier
Darwin’s Influences: Jean Baptiste Lamarck
Lamarckian Inheritance
Lamarck noticed that each organism is usually well ADAPTED to its environment.
He proposed that organisms change over time as they adapt to changing environments.
Darwin once accepted this idea because it proposed a role for inheritance in evolution.
Larmack thought early Giraffes stretched their necks to feed and they’re newly acquired Long neck was then passed off to
offspring….._WRONG___!!!Acquired traits are not hereditable (or are they?)
Lamarckian Inheritance
Some of Lamarcks ideas still have relevance today though and he may be right in a way…check out Epigenetics for an extra credit
project!
Darwin’s Influences: Thomas Malthus
Malthus:
“The tragedy of the COMMONS”
Populations tend to grow faster than the food supply needed to feed it
Darwin’s Influences:
Charles Lyell & James Hutton
Lyell & Hutton- GRADUALISM
Changes occur over vast periods of time in geology; land formations move and topography changes
Darwin’s Influences: Georges Cuvier
Cuvier - CATASTROPHISM
Geologic changes occur rapidly and have catastrophic outcomes for living things,
…..like extinction
Darwin’s Theory: DESCENT with Modification
Darwin’s Dangerous Idea:
He didn’t publish his findings until he was 50!
“On the Origin of Species” 1859
Evolutionary pathway resembled a branched tree
NOT a ladder from lower forms to higher forms
All CONTEMPORARY species have descended from earlier species
DESCENT WITH MODIFICATION: Organisms today evolved from previous species as a result of Natural Selection
Darwin’s Observations
Individuals in a population VARY some of these variations are inheritable
Populations produce more OFFSPRING than the environment’s food, space, and other assets.
Therefore, species COMPETE for resources
EVOLUTION BY NATURAL SELECTION
Evolution is a change in the inherited characteristics of a population from one generation to the next.
Darwin’s theory predicts that;
Over time, the number of individuals that carry ADAPTIVE traits will increase in a population.
Every living thing has the potential to produce many offspring, but not all of those offspring are likely to SURVIVE and reproduce.
Individuals that have traits that suit their environment are more likely to survive.
Individuals that have certain traits tend to produce more offspring than others do.
These differences are part of natural selection.
The Mechanism of Natural Selection
Selection and Adaptation
Darwin’s theory explains why living things vary in form and match their environment.
Each ENVIRONMENT presents unique challenges and opportunities to survive and reproduce.
So, each species evolves because of the “selection” of those individuals that survive the challenges or make best use of the
opportunities.
The Mechanism of Natural Selection
Put another way, each species becomes adapted to its environment as a result of living in it over time.
An ADAPTATION is an inherited trait that is present in a population because the trait helps individuals survive and reproduce in a
given environment.
Darwin’s theory explains evolution as a gradual process of adaptation.
Note that Darwin’s theory refers to populations and species—not individuals—as the units that evolve.
–Also, keep in mind that a species is a group of populations that can INTERBREED
DARWINS THEORY OF EVOLUTION BY NATURAL SELECTION
4 Steps in Darwin’s Theory of Evolution by Natural Selection.
Step 1 Overproduction: Every population is capable of producing more offspring than
can possibly survive.
Step 2 Variation: Variation exists within every population. Much of this variation is in
the form of inherited traits.
Step 3 Selection: In a given environment, having a particular trait can make individuals
more or less likely to survive and have successful offspring. So, some individuals leave more
offspring than others do.
Step 4 Adaptation: Over time, those traits that improve survival and reproduction will
become more common.
The Mechanism of Natural Selection
VOCABULARY
Natural Selection: greater reproductive success displayed by individuals with favorable traits
Variation: differences within a population
Adaptations: traits that are selected for because they help an organism survive and reproduce
Evidence for Evolution
Evidence for Evolution comes from each of the following disciplines
The Fossil Record
Embryology
Biogeography
Comparative Anatomy
Development Biology or
Biochemistry
Evidence for Evolution
A Fossil is a record of an animal that is preserved in rock
Found in SEDIMENTARY Rock
Fossils show overall structural scheme of how organism evolved
Including:
Body scheme
Social Structure
Feeding behavior
New fossils in upper layers, older fossils in lower layers
Mobility
Evidence for Evolution
Evidence from the fossil record allows us to piece together an Evolutionary SEQUENCE
The Evolutionary Sequence of Modern Cetacea (Whales)
New fossils in upper layers, older fossils in lower layers
Comparative Anatomy
HOMOLGOUS Structure:
Similar structures in related organisms suggests organisms share a common ancestor
Human Hand = Whale flipper
ANALOGOUS Structures
Similar structures in nonrelated organisms show evolution recreates similar solutions to different environmental challenges
Kangaroo vs Deer
Vestigial Organs
VESTIGIAL Organs with no apparent use, but resemble functional structures in ancestors
Tailbones
Appendix
Wisdom Teeth
Whale Pelvis
Comparative Embryology
Ontogeny Recapitulates Phylogeny- Organisms with common descent have similar organs
Embryos undergo many physical and genetic changes as they develop into mature forms.
Scientists compare the EMBRYOLOGICAL development of species to look for similar patterns and structures. Such similarities most
likely derive from an ancestor that the species have in common.
For example, at some time during development, all vertebrate embryos have a tail. Vertebrates are animals that have backbones.
Vertebrates breathe though lungs but as embryos, all vertebrates have gills that becomes the Eustachian tube in man
Biochemistry
To explain the patterns of change seen in anatomy, scientists make testable predictions.
For example, if species have changed over time, the GENE that determine their characteristics should also have changed.
Genes can change by mutation and that such change can make new varieties appear.
A comparison of DNA or amino-acid sequences shows that some species are more genetically similar than others.
Chimps –Humans 99% Homology
These comparisons, like those in anatomy, are evidence of hereditary relationships among the species.
Biogeography
Study of species distribution on Galapagos Islands look similar to South American species
Each island would have to had it own special creation event for each species.
Darwin contended one species MIGRATED from South America and underwent Adaptive Radiation
How Do Variations Arise?
Natural selection IS NOT the cause of variation
Mutation - Random changes in DNA sequences in the parents genome
Gene Shuffling - mixing of parental chromosomes can create new genetic combinations
Variation arises randomly. Variations are then SELECTED on by nature.
Variations which are selected for are called ADAPTATIONS
Adaptations and Speciation
Types of Adaptations
STRUCTURAL Adaptations: Involve structure or anatomy - Bird’s beak, Anteaters sticky tongue
PHYSIOLOGICAL Adaptations: Functions in organisms
- Poison Venom in a snake, ink of an octopus
BEHAVIORAL Adaptations: Behavior aids in survival and reproduction
Wildebeasts/ Caribou/ Bird Migration
Wolves Hunt in Packs
Fish swim in schools
Species & Speciation
Species: A group of organisms that are so similar they can interbreed and produce VIABLE/FERTILE offspring
Some Organisms are similar enough to form Hybrids-they can breed but the offspring is infertile
Horses + Donkey = Mule
Lion + Tiger = Liger
…Not the same species but a HYBRID
Human male + human female = human baby…same species!
3 Types of Natural Selection
Directional Selection: Shifts a population toward one extreme form of a trait
Stabilizing Selection:Shifts a population toward intermediate (medium) traits
Disruptive Selection:Extreme phenotypes are more common
DIRECTIONAL Selection
Shifts a population toward one extreme form of a trait
4 million years ago there were heavy cheetahs
Over time, light, fast animals reproduced more successfully
Natural selection favored the genes that pushed the cheetah’s weight in one direction…lighter
Or the Human Brain…it has continued to grow larger with more convolutions (gyrii) over time
STABILIZING Selection:
Shifts a population toward intermediate (medium) traits
Example: Most human babies weight ~ 7pounds
DISRUPTIVE Selection:
Extreme phenotypes are more common
Example: African butterflies appear as either bright orange or bright blue
These colors mimic other butterflies that are foul-tasting; less likely to be eaten
Intermediate butterflies look like neither, and are more likely to be eaten
Patterns of Evolution
SPECIATIONOrganisms which are separated by distance + gene pool will no longer interbreed. Each group becomes new species
Species become dissimilar or more alike over time through gradual Change
5 Types of Evolution
Divergent Evolution:
Coevolution
Adaptive Radiation:
Extinction
Convergent Evolution:
DIVERGENT EVOLUTION:
Single population is split into 2 or more populations.
CONVERGENT EVOLUTION:
2 dissimilar species evolve in ways to make them APPEAR more similar
Sugar Gliders- winged marsupials in Australia
Flying Squirrels - Winged squirrels in Northern Hemisphere
COEVOLUTION
Organisms are part of one other’s environment, so they can affect one another’s evolution. Species that live in close contact often have
clear adaptations to one another’s existence.
ADAPTIVE RADIATION
Over time, species may split into two or more lines of descendants, or lineages. The process tends to speed up when a new species enters
an environment that contains few other species. (FINCHES)
EXTINCTION
If all members of a lineage die off or simply fail to reproduce, the lineage is said to be extinct. The fossil record shows 99% of all species
have become EXTINCT
The Pace of Evolution and Earth History
Gradualism: Over time, new species arise as environment change
If true, we should see intermediate species in fossil record…not always true
Catastrophism: Rapid catastrophic events shape earth and living thing
THE CURRENT ACCEPTED THEORY
PUNCTUATED EQUILIBRIUM: Species exist for long periods of time without changes,
then large changes occur over short periods of time
Populations & Evolution
Larger populations tend to have more genetic variation
Smaller populations tend to have less genetic variation
Genetic Drift/Founder Effect- Loss of genetic variation due small population sizes.
Extinction more likely-10,000 years ago, almost all cheetahs go extinct due to climate changes. Resulting cheetahs have little genetic
diversity
BIOLOGY
NAME_________________________
BRAINSTORMING
USE THE FOLLOWING DIAGRAM TO COMPARE AND CONTRAST DARWIN AND
LAMARCK’S IDEAS CONCERNING CHANGES IN SPECIES
LIST 3 DIFFERENCES AND 3 SIMILARITIES FOR EACH HERE
DIFFERENCES
1
2.
3.
SIMILARITIES
1.
2.
3.
4 SQUARES ACTIVITY 10PTS
COMPARE AND CONTRAST DARWIN AND LAMARCKES IDEAS CONCERNING CHANGES IN SPECIES.
.USE THE TECHNQUES DEMONSTRATED TO GENERATE A 6 SENTENCE PARAGRAPH WITH TOPIC
SENTENCE 4 SUPPORTING STATEMENTS AND SUMMARY SENTENCE
TOPIC SENTENCE:
4 SUPPORTING STATEMENTS
SUMMARY STATEMENT
PLEASE WRITE YOUR 6 SENTENCE PARAGRAPH HERE USING THE 4 QUARTERS AND
VENN DIAGRAMS
BIOLOGY
NAME_________________________
4 SQUARES ACTIVITY 10PTS
USE THE FOLLOWING DIAGRAM TO COMPARE AND CONTRAST DIRECTIONAL, DISRUPTIVE,
AND STABILIZING SELECTION
LIST 3 DIFFERENCES AND 3 SIMILARITIES FOR EACH HERE
DIFFERENCES
1
2.
3.
SIMILARITIES
1.
2.
3.
COMPARE AND CONTRAST DIRECTIONAL, DISRUPTIVE, AND STABILIZING SELECTION.
USE THE TECHNQUES DEMONSTRATED TO GENERATE A 6 SENTENCE PARAGRAPH WITH TOPIC
SENTENCE 4 SUPPORTING STATEMENTS AND SUMMARY SENTENCE
TOPIC SENTENCE:
4 SUPPORTING STATEMENTS
SUMMARY STATEMENT
PLEASE WRITE YOUR 6 SENTENCE PARAGRAPH HERE USING THE 4 QUARTERS AND
VENN DIAGRAMS
BIOLOGY CH17 EVOLUTION
NAME_____________________________
15pts Feel Free to use the power-point (Found on the calendar)or any materials I have
given you to answer the questions.
ESSENTIAL QUESTIONS
1. What are the 5 conditions necessary for Hardy Weinberg Equilibrium to occur?
a.
b.
c.
d.
e.
2. What is a species?
3. What are the three major patterns of selection and describe each. Please include a
graph for each type to illustrate your answers.
a.
b.
c.
4. What is Reproductive isolation?
5. What are the 5 mechanisms that can help reproductive isolation to occur?
a.
b.
c.
d.
e.
BIOCH17
POWERPOINT OUTLINE
Chapter 17 Population Genetics and Speciation
ESSENTIAL QUESTIONS
How is microevolution studied?
How is phenotypic variation measured?
How are genetic variation and change measured?
How does genetic variation originate?
NAME_____________________________
POPULATION GENETICS
How is microevolution studied?
Microevolution can be studied by observing changes in the numbers and types of alleles in populations.
The study of microevolution in this sense is POPULATION genetics.
GENETICS AND EVOLUTION
Charles Darwin knew that heredity influences characteristics, but he did know about GENES.
We can now study and predict genetic variation and change that underlie evolution.
MICROEVOLUTION
Microevolution or POPULATION GENETICS is evolution at the level of genetic change in populations.
The study of genetics and evolution are advancing together.
The link from microevolution to macroevolution—SPECIATION—can be studied in detail.
PHENOTYPIC VARIATION
How is phenotypic variation measured?
Biologists study polygenic phenotypes by measuring each INDIVIDUAL in the population and then analyzing the distribution of the
measurements.
The variety of phenotypes that exists for a given characteristic depends on how many genes affect it.
PHENOTYPIC VARIATION
POLYGENIC traits or characters are influenced by several genes. Examples include human eye color and height.
A distribution is an overview of the relative frequency and range of a set of values.
Often, some values in a range are more common than others.
A normal distribution, or BELL curve, is one that tends to cluster around an average value in the center of the range.
MEASURING VARIATION AND CHANGE
How are genetic variation and change measured?
Genetic variation and change are measured in terms of the ALLELE FREQUENCY in the gene pool of a population.
A frequency is the proportion or ratio of a group that is of one type. To study genetic change, the frequency of each allele in a
population can be tracked over time.
The particular combination of alleles in a population at any one point in time makes up a gene pool.
What is the ALLELE Frequency of the “b” eye color gene in your class??
SOURCES OF GENETIC VARIATION
How does genetic variation originate?
The major source of new alleles in natural populations is MUTATION in gametes or “germ cells.”
Evolution cannot proceed if there is no variation.
Mutation generates new alleles at a slow rate.
Only mutations in germ cells (egg and sperm) are passed on to offspring.
Section 2: Genetic Change
KEY IDEAS
What does the Hardy-Weinberg principle predict?
How does sexual reproduction influence evolution?
Why does population size matter?
What are the limits of the force of natural selection?
What patterns can result from natural selection?
EQUILIBRIUM AND CHANGE
What does the Hardy-Weinberg principle predict?
The Hardy-Weinberg principle predicts that the frequencies of alleles and genotypes in a population will NOT change unless at
least one of five forces acts upon the population.
The forces that can act against GENETIC EQUILLIBRIUM are gene flow, nonrandom mating, genetic drift, mutation, and natural
selection.
HARDY WEINBERG EQUILIBRIUM
A population in which no genetic change occurred would be in a state of genetic equilibrium.
Genetic change in a population can be measured as a change in genotype frequency or ALLELE FREQUENCY.
A change in one doesn’t necessarily mean a change in the other.
THE 5 CONDITIONS OF HARDY WEINBERG EQUILIBRIUM
1. GENE FLOW
Gene flow occurs when genes are added to or removed from a population.
Gene flow can be caused by MIGRATION, the movement of individuals from one population to another.
2. NONRANDOM MATING
In sexually reproducing populations, any limits or preferences of MATE choice will cause nonrandom mating.
3. GENETIC DRIFT
Chance events can cause rare alleles to be lost from one generation to the next, especially when populations are small.
Such random effects on allele frequencies are called genetic drift.
4.MUTATION
Mutation can add a new allele to a population.
5. NATURAL SELECTION
Natural selection acts to eliminate individuals with certain traits from a population.
As individuals are eliminated, the alleles for those traits may become less frequent in the population.
Thus, both allele and genotype frequencies may change.
SEXUAL REPRODUCTION AND EVOLUTION
How does sexual reproduction influence evolution?
Sexual reproduction creates the possibility that mating patterns or BEHAVIORS can influence the gene pool of a population.
For example, in animals, females sometimes select mates based on the male’s size, color, ability to gather food, or other
characteristics. This kind of behavior is called sexual selection and is an example of nonrandom mating.
SEXUAL REPRODUCTION AND EVOLUTION
Another example of nonrandom mating is INBREEDING, in which individuals either self-fertilize or mate with others like
themselves.
Inbreeding is more likely to occur if a population is small. In a small population, all members are likely to be closely related.
POPULATION SIZE AND EVOLUTION
Why does population size matter?
Allele frequencies are more likely to remain stable in LARGE populations than in small populations.
Population size strongly affects the probability of genetic change in a population.
Genetic drift is a strong force in small populations and occurs when a particular allele DISAPPEARS.
NATURAL SELECTION AND EVOLUTION
What are the limits of the force of natural selection?
Natural selection acts only to change the relative frequency of alleles that exist in a population. It acts on genotypes by removing
UNSUCCESSFUL phenotypes from a population.
Natural selection is a result of the following facts:
–All populations have genetic variation.
–Individuals tend to produce more OFFSPRING than the environment can support.
–Populations depend upon the reproduction of individuals.
GENETIC RESULTS OF SELECTION
The result of natural selection is that each allele’s frequency may increase or decrease depending on the allele’s effects on survival
and reproduction.
Although natural selection is not the only force that can cause evolution, it is a powerful force.
WHY SELECTION IS LIMITED
The key lesson that scientists have learned about evolution by natural selection is that the ENVRIONMNET
does the selecting.
Only characteristics that are expressed can be targets of natural selection. If a mutation results in rare recessive alleles, for
example, selection cannot operate against it.
For this reason, genetic disorders (such as cystic fibrosis in humans) can persist in populations.
PATTERNS OF NATURAL SELECTION
What patterns can result from natural selection?
Three major patterns are possible in the way that natural selection affects the distribution of polygenic characters over time.
These patterns are Directional selection, Stabilizing selection, and Disruptive selection
Directional Selection
In directional selection, the “peak” of a normal distribution moves in one direction along its range.
In this case, selection acts to eliminate on extreme from a range of phenotypes, making them less common.
Stabilizing Selection
In stabilizing selection, the bell-curve shape becomes NARROWER.
In this case, selection eliminates individuals that have alleles for any extreme type.
Stabilizing selection is very common in nature.
Disruptive Selection
In disruptive selection, the bell curve is “disrupted” and pushed apart into TWO peaks.
In this case, selection acts to eliminate individuals with average phenotype values.
Section 3: Speciation
KEY IDEAS
How can species be defined?
How do we know when new species have been formed?
Why is studying extinction important to understanding evolution?
DEFINING SPECIES
A species is generally defined as a POPULATION that can interbreed and usually produce fertile offspring.
Other definitions for species may be used for fossils or for organisms that reproduce asexually. Species may be instead be defined
based on their physical features, their ecological roles, and their genetic relatedness.
FORMING NEW SPECIES
How do we know when new species have been formed?
Speciation has occurred when the net effects of evolutionary forces result in a population that has unique features and is
REPRODUCTIVELY isolated.
SPECIATION
Each population of a single species lives in a different place.
In each place, natural selection acts upon each population and tends to result in offspring that are better adapted to each specific
environment.
If the ENVIRONMENTS differ, the adaptations may differ. This is called divergence and can lead to the formation of new species.
Speciation is the process of forming new species by evolution from preexisting species
REPRODUCTIVE ISOLATION
Reproductive isolation is a state in which two populations can no longer interbreed
From this point on, the groups may be subject to different forces, so they will tend to diverge over time.
Through divergence over time, populations of the same species may differ enough to be considered SUBSPECIES.
Subspecies are simply populations that have taken a step toward speciation
REPRODUCTIVE ISOLATION
Any of the following mechanisms may contribute to the reproductive isolation of populations:
Geography
Ecological Niche
Mating Behavior and Timing
Polyploidy
Hybridization
EXTINCTION: THE END OF SPECIES
Why is studying extinction important to understanding evolution?
The species that exist at any time are the net result of both speciation and extinction.
Extinction occurs when a species fails to produce any more descendants. Extinction, like speciation, can only be detected after it is
complete.
EXTINCTION THE END OF SPECIES
More than 99% of all of the species that have ever lived becoming extinct.
Many cases of extinction are the result of ENVIRONMENTAL change.
If a species cannot adapt fast enough to changes, the species may be driven to extinction.
BIO CH17 VOCABULARY REVIEW
Chapter 17 Population Genetics and Speciation
MICROEVOLUTION: the study of changes in allele frequency of a population
POPULATION: A group of organism of the same species that are breeding
PHENOTYPIC VARIATION: the allele frequencies within a population
NORMAL DISTRIBUTION: the bell curve
ALLELE FREQUENCY: the ratio of specific alleles in a population
GENETIC VARIATION: the different forms of alleles and traits in a population
HARDY WEINBERG EQUILIBRIUM: IS an IDEAL condition (IMPOSSIBLE) in which no evolution or allele
frequency change occurs (EQUILIBRIUM)- when all of the following DO NOT HAPPEN
GENE FLOW: the gain or loss of new alleles through immigration or emmigration
MUTATION: change in DNA sequence
NONRANDOM MATING: reproductive selection, females choose mates selectively
GENETIC DRIFT: small populations can have major changes in allele frequency
NATURAL SELECTION: when the environment favors a particular allele over another
FOUNDER EFFECT: the initial alleles/individuals in a population have great effect on allele frequency
POPULATION SIZE: the larger the population the smaller the impact of individual changes in allele frequency
SPECIATION: the development of new species through directional, disruptive or stabilizing selection
REPRODUCTIVE ISOLATION: a barrier to reproduction amoung individuals that leads to new species
Geography: physical barriers like rivers, canyons, oceans –squirrels in grand canyon
Ecological Niche: organisms are performing different roles in an ecosystem – Darwin Finches
Mating Behavior and Timing: migrations, mating dances in birds
Polyploidy: changes in chromosome number
Hybridization : pairings between similar species- liger
PENNSYLVANIA STATE STANDARDS: EVOLUTION
BIO.B.3.1.1: Explain how natural selection can impact allele frequencies of a population.
BIO.B.3.1.2: Describe the factors that can contribute to the development of new species (isolating mechanisms, genetic
drift, founder effect, migration).
BIO.B.3.1.3: Explain how genetic mutations may result in genotypic and phenotypic variations within a population.
BIO.B.3.2.1: Interpret evidence supporting the theory of evolution (fossil, anatomical, physiological, embryological,
biochemical, and genetic code).
BIO.B.3.3.1: Distinguish among the scientific terms: hypothesis, inference, law, theory, principle, fact, and observation.
BIO.B.1.2.1: Describe how the process of DNA replication results in the transmission and/or conservation of genetic
information.
SUPERCONDENSED CHAPTER 16-17 REVIEW
BIOLOGY CH16 Evolution
CHARLES DARWIN : The Father of Evolution through Natural Selection,
he observed change through “Descent with Modification.” Wrote on the Origin of Species in 1859
DESCENT WITH MODIFICATION: Organisms today evolved from previous species as a result of Natural Selection
SPECIES : Organisms so similar they can interbreed and produce VIABLE (fertile) offspring
NATURAL SELECTION: greater reproductive success displayed by individuals with ADAPTIVE traits
VARIATION: differences within a population
ADAPTATIONS: traits that are selected for because they help an organism survive and reproduce
EVOLUTION: Changes in species over time- Occurs when genes in a population change/shift to enhance survival and reproduction
JEAN BAPTISTE LAMARCK: Observed organisms change/evolve by passing down AQUIRED TRAITS
LYELL AND HUTTON: Geologists who proposed GRADUALISM as the source of change
CUVIER: Geologist who proposed CATASTROPHISM as the source of change
EVIDENCE FOR EVOLUTION: Comes from Fossils, Comparative Anatomy, Embryology, Biochemistry, Biogeography, and others!
FOSSIL EVIDENCE: Records of past organisms show common ancestry
COMPARATIVE ANATOMY: the study of similarities in organisms of common ancestry
Vestigial Structures- appendix, whale pelvis
Analogous Structures – bee wing v. bird wing
Homologous structure - your hands-whale flipper
EMBRYOLOGY: The study of how embryos develop to show common ancestry- you had gills and a tail!
BIOCHEMISTRY: The similarity in gene sequence
BIOGEOGRAPHY: The study of how organisms are distibuted today and in the fossil record
3 TYPES OF ADAPTATIONS
STRUCTURAL ADAPTATIONS: Physical feature like a wing to fly or fins to swim
PHYSIOLOGICAL ADAPTATION: Body functions like the production of venom or the ability to tolerate heat
BEHAVIORAL ADAPTATION: When organisms work together like a wolf pack, or school of fish
3 TYPES OF NATURAL SELECTION
DIRECTIONAL SELECTION: When a direction in phenotypes is favored- bigger brains
STABILIZING SELECTION: When 1 average phenotype is selected for – 7 lb babys
DISRUPTIVE SELECTION: When 2 extreme phenotypes are selected for simultaneously- different colored butterflies
SPECIATION: The formation of new species through evolution
BIO Chapter 17 Population Genetics and Speciation
MICROEVOLUTION: the study of changes in allele frequency of a population
POPULATION: A group of organism of the same species that are breeding
PHENOTYPIC VARIATION: the allele frequencies within a population
NORMAL DISTRIBUTION: the bell curve
ALLELE FREQUENCY: the ratio of specific alleles in a population
GENETIC VARIATION: the different forms of alleles and traits in a population
HARDY WEINBERG EQUILIBRIUM: IS an IDEAL condition (IMPOSSIBLE) in which no evolution or allele
(EQUILIBRIUM)- when all of the following DO NOT HAPPEN
GENE FLOW: the gain or loss of new alleles through immigration or emmigration
MUTATION: change in DNA sequence
NONRANDOM MATING: reproductive selection, females choose mates selectively
GENETIC DRIFT: small populations can have major changes in allele frequency
NATURAL SELECTION: when the environment favors a particular allele over another
FOUNDER EFFECT: the initial alleles/individuals in a population have great effect on allele frequency
POPULATION SIZE: the larger the population the smaller the impact of individual changes in allele frequency
SPECIATION: the development of new species through directional, disruptive or stabilizing selection
REPRODUCTIVE ISOLATION: a barrier to reproduction amoung individuals that leads to new species
Geography: physical barriers like rivers, canyons, oceans –squirrels in grand canyon
Ecological Niche: organisms are performing different roles in an ecosystem – Darwin Finches
Mating Behavior and Timing: migrations, mating dances in birds
frequency change occurs
Polyploidy: changes in chromosome number
Hybridization : pairings between similar species- liger
BIOLOGY CH16 -17 REVIEW
Types of Natural Selection and Evolution
NAME________________________
Identify the type of natural selection – stabilizing, directional, or disruptive.
1. The peppered moth becomes lighter in color over time. ____________________
2. Giraffe necks become longer. __________________
3. Most human males are between 5’7” and 6’2”. _____________________
4. Poison dart frogs appear as either a bright orange or a bright blue. ____________
5. Whales have become larger in size over time. _________________
6. Shell color of limpets are pure white or dark tan. _______________
7. Most small anoles lizards are between 3 and 6 inches long. _________________
8. Anteaters’ tongues have gotten progressively longer over time. ______________
Identify the pattern of microevolution – mutations, genetic drift, gene flow, random
mating, natural selection
1. By chance, only the red flowers were pollinated by bees, so only red flowers show
up in the next generation.
2. Due to a change in a base in the DNA code, a new color appears in the wings of
local moths.
3. Female marine iguanas will only mate with males who bob their heads.
4. When large seeds are available, birds with large beaks survive and reproduce
more often than birds with small beaks.
5. A rabbit with brown fur moves into a region where there are only gray rabbits.
6. Due to a lack of available food, only the small marine iguanas survive and pass on
their genes.
7. The base adenine is replaced with guanine, resulting in a new enzyme that allows
the organism to digest more meat.
8. A storm blows a group of yellow finches into an area where there were only
brown finches previously.
9. The female bird-of-paradise will only mate with the male who dances in a certain
way for her.
10. For unknown reasons, only the black mice mated in the spring, so no white mice
were seen in the following months.
Identify the pattern of macroevolution – coevolution, convergent evolution, or divergent
evolution.
1. Sharks and porpoises have the same fin formations. __________________
2. Primitive flatworms evolved into jellyfish and parasitic roundworms.
________________
3. Moth-pollinated plants often have spurs or tubes the exact length of a certain
moth’s “tongue.” ________________
4. Birds and bats both have wings for flight. ____________________
5. Primitive algae split into gymnosperms and angiosperms. ________________
6. Songbirds have evolved different beaks for seed-eaters and worm-eaters.
__________________
7. 20 species of Honeycreepers in Hawaii have evolved to feed on different diets.
___________________
8. Acacias trees have large, hollow thorns in which ants live. On the tips of its
leaflets, the plant makes a substance used by the ants as food. The ants defend the
tree from herbivores by attacking/stinging any animal that even accidentally
brushes up against the plant, and prune off seedlings of any other plants that
sprout under “their” tree. ____________________
SAMPLE ESSAYS- FINAL QUESTIONS
1. COMPARE AND CONTRAST DARWINS AND LAMARCKES THEORIES OF HOW SPECIES
CHANGE. BE SURE TO MENTION EACH PERSONS VIEWS ON HOW SPECIES CHANGE,
ADAPTATIONS, INHERITED & ACQUIRED TRAITS AND VARIATION.
2. HOW DOES THE CURRENT THEORY OF PUNCTUATED EQUILIBRIUM COMBINE THE
THINKING OF DARWIN, LYELL & HUTTON, CUVIER, AND MALTHUS? DOES LAMARCKES
IDEAS HAVE ANY RELEVANCE?
3. DESCRIBE THE 3 TYPES OF NATURAL SELECTION USING GRAPHS TO DESCRIBE
CHANGES IN THE POPULATION.
4. DESCRIBE HOW SPECIATION OCCURS. USE EXAMPLES LIKE LEOPARDS OR FINCHES
AND BE SURE TO INCLUDE FACTORS THAT LEAD TO REPRODUCTIVE ISOLATION, AS
WELL AS THE DEFINITON FOR POPULATIONS AND SPECIES