It Is Likely That You Taught First-Year Biology Students About the “Peppered Moth”

01 Microevolution Unique Gene Pools TEACHER NOTES

It is likely that you taught first-year biology students about the “peppered moth”. Prior to starting this unit, assign students a task. Have Microevolution: Unique Gene Pools them go to this website http://www.techapps.net/interactives/pepperMoth 1 s.swf and work their way through the components of the animations. The site is very well done and it will serve as nice introduction as well as a good review of basic evolutionary concepts and how man and the environment impact natural selection.

Charles Darwin

• Charles Darwin (1809-1882) is credited with proposing that the mechanism for th process of evolution is natural selection. • Darwin spent five years on a voyage tha took him around the world with the majority of his time spent in South Ameri 2 and its neighboring islands. • Darwin published his theory with compelling evidence for evolution in his 1859 book On the Origin of Species, overcoming scientific rejection of earlier concepts of transmutation of species.

http://en.wikipedia.org/wiki/Charles_Darwin contains FAR more information about Charles 3 He established that all species of life have descended over time from Darwin. common ancestors, and proposed the scientific theory that this branching pattern of evolution resulted from a process that he calle natural selection, in which the struggle for existence has a similar effect to the artificial selection involved in selective breeding.

Prior Knowledge Prior 3

Charles Darwin

• By the 1870s the scientific community and much the general public had accepted evolution as a fa

• However, many favored competing explanations and it was not until the emergence of the modern evolutionary synthesis from the 1930s to the 195 4 that a broad consensus developed in which natur selection was the basic mechanism of evolution.

• In modified form, Darwin's scientific discovery i the unifying theory of the life sciences, explainin the diversity of life.

01 Microevolution Unique Gene Pools TEACHER NOTES Darwin’s Observations n

• Populations change over time as evidenced by the fossil record. • There are always more offspring produced than the preceding generation. Darwin's example considers the "slowest breeder • Populations, if left unchecked, grow at a geometric rate rather than an arithmetic of all the animals", elephants. Also point out his 5 rate. • Darwin used an example involving elephants to illustrate the points above. math was a bit flawed since he neglected death He estimated that if elephants underwent unrestricted reproduction, that in 740-750 years there would be 19 million elephants rates AND did not assume a 50-50 split of male produced from just one original pair. what will happe vs. female offspring!

Students will most likely ask you, “What’s the difference between geometric rate and arithmetic tion to predict rate?” The simple answer is arithmetic rates are linear, i.e. 2, 4, 6, 8, 10 etc. while geometric rates Darwin’s Observations are not linear but rely on a different mathematical function such as an exponential function.

6 These observations are what helped Charles

or simulated popula or Darwin formulate natural selection as the mechanism for evolution. Natural selection is

the “theory of evolution” . Evolution does occur. Species do change over time as the fossil record

demonstrates.

http://www.idlex.freeserve.co.uk/idle/evolution/s ex/elephant.html provides a nice explanation of the “math”

thods to data from a real Darwin’s Elephant Problem

“There is no exception to the rule that every organic being naturally increase at so high a rate that if not destroyed, the earth would soon be This site has a “calculator” that lets students set covered by the progeny of a single pair .... The Elephant is reckoned to be the slowest parameters relating to Darwin’s Elephant breeder of all known animals, and I have taken some pains to estimate its probable minimum rate of natural increase: it will be under the Problem so they can understand just how wrong 7 mark to assume that it breeds when thirty years old, and goes on breeding till ninety years old, Darwin was. bringing forth three pairs of young in this interval; if this be so, at the end of the fifth century there would be alive fifteen million http://www.athro.com/evo/elframe.html elephants, descended from the first pair.” (Darwin, 1859 p.64)

[See SP 2.2; Essential knowledge 1.A.1] to apply mathematical me Darwin’s Observations

• There is variation within a given species and the majority of this variation is inherit 8 This litter of kittens vary with respect to coat pattern and color. Emphasize that there is a difference between • Any variation may, to some degree, affect the ability of an organism to reproduce an contribute genes to the gene pool, thus affecting evolutionary success. heredity and mutation. • Species change over time. These changes are related to traits that are inherited or a from an alteration of the genetic code. • Some inherited traits are beneficial and contribute to survival. • Whether a trait is beneficial or not is a function of the environment in which it lives

LO 1.3 The student is able to the population in future. 01 Microevolution Unique Gene Pools TEACHER NOTES Adaptations and Fitness • An adaptation is a genetically controlled trait that is favored by natural selection and gives the organism a reproductive advantage ensuring the trait is passed on to its Ask students to compare these two hares and

tural descendants. 9 identify the differences in their traits. The • This trait may also allow the individual students should come up with coat color, length to survive longer thus increasing the reproductive rate of that individual.

[See SP 7.1; of ears, length of limbs, body shape, etc.

It’s one thing to “identify” traits and yet another Adaptations and Fitness to explain their importance or implication! • The antelope hare lives in the desert, and the snowshoe hare lives in the the environment. mountains. The long limbs of the antelope hare help • Explain how the differences in their dissipate body heat and keep the hare cool. The traits enhance their ability to survive in 10 their respective environments. brown coat color helps it to blend in with its • Evolutionary success or fitness refers to environment, thus be less obvious to potential the contribution of genes to the gene pool and NOT how long an organism predators. The snowshoe hare has smaller ears lives. and shorter limbs with a rounder body. This 10 helps keep the hare warmer. The white coat

time to a change in color helps it to also blend in with its environment. The Effect of Environmental Change

• Earth’s environment is NOT STATIC, but rather ever changing. • As a consequence, traits or adaptations that were favorable Environmental changes often cause a shift in may become unfavorable. • The peppered moth, Biston betularia is native to England selection pressures. Traits that were once and exists in two forms, one is dark and the other light with a “peppered” appearance. Birds are its main predator. beneficial to a population of organisms may

11 na of role the investigate quantitatively and qualitatively to ta • Prior to the industrial revolution, only 2% of the moths were dark. become detrimental and vice versa. • The industrial revolution produced vast amounts of sulfur dioxide and soot from the burning of coal which altered the environment. • Fifty years later 95% of the moths were dark. http://www.techapps.net/interactives/pepperMoth • Propose an explanation!

11 s.swf

idence provided by da Explanation: The trees were previously light and Industrial Melanism covered in lichens, thus peppered moths had the advantage of camouflage over dark moths. (You

England has since may have to point out the peppered moth near regulated the burning o

connect evolutionary changes in a population over in a population over connect evolutionary changes coal and as a result, the the top of photo A.) trees are returning to th original state (A). 12 Consequently, the colo among the population o [See SP 2.2, 5.3; Essential knowledge 1.A.1] moths in Britain has The SO2 gas produced from the industrial shifted back so that the peppered moths are onc revolution killed the lichens. Furthermore, the again favored. soot produced during the burning of coal

12 collected on tree trunks changing their appearance and darkening them. As a result, the darker moth is now more camouflaged and less likely to be eaten by birds. LO 1.2 The student is able to evaluate ev in evolution. selection LO 1.5 The student is able to Essential knowledge 1.A.2] 01 Microevolution Unique Gene Pools TEACHER NOTES Evolution Defined

• Evolution is defined as a change in the inherited characteristics of biological populations over successive generations. • Evolutionary processes give rise to Students need to be clear on the approaching diversity at every level of biological 13 organization, from the molecular to the definitions and distinctions AND have some macroscopic. illustrative examples they can discuss on the AP • As a result diversity is prevalent among molecules such as DNA as well as Exam. individual organisms and species of organisms.

Remind students that a gene is a sequence of DNA nucleotides that specify a particular polypeptide chain and that genes code for proteins.

on over time on over Have students generate an example for each of Microevolution the 4 example “causes” of microevolution. [See SP 2.2, 5.3;

to qualitatively and and qualitatively to Microevolution is simply a change in gene frequency Many correct answers are possible! within a population. • Evolution at this scale can be observed over short periods of tim such as from one generation to the next. • Example: The frequency of a gene for pesticide resistance in a natural selection favored the gene (sickle 14 s in a populati population of crop pests increases. • • Such a change might come about because cell anemia & malaria) – natural selection favored the gene – the population received new immigrants carrying the gene (gene flow) the population received new immigrants – nonresistant genes mutated into a resistant version of the gene • – of random genetic drift from one generation to the next carrying the gene (light skinned population provided by data 14 crosses with dark skinned population

resulting in hybrids) • some nonresistant genes mutated to the resistant version (natural immunities to natural selection in evolution. evolution. in selection natural disease among populations) [See SP 7.1; Essential knowledge 1.A.2] • because of random genetic drift from one evaluate evidence connect evolutionary change generation to the next (founder effect) Microevolution

• A gene is a sequence of DNA nucleotides that specify a particular polypeptide chain. Really emphasize those last two bullets! When • Genes code for proteins. • An allele is a particular form of a gene. students write about evolution it is VERY For example: B represents the allele for 15 black coat color and b for white coat color. important that they can “say what they mean and • Selection acts on phenotype because differential reproduction an survivorship depend on phenotype not genotype. mean what they say”. These last two bullets • Natural selection acts on individuals, but only populations belong in the response to any evolution free- evolve. response question!

to a change in the environment. Essential knowledge 1.A.1] quantitatively investigate the role of role the investigate quantitatively LO 1.2 The student is able to LO 1.5 The student is able to 01 Microevolution Unique Gene Pools TEACHER NOTES Macroevolution Macroevolution is evolution on a scale of separated Macroevolution will be dealt with separately and gene pools (not individuals). • Think of it as an accumulation of changes which result in the definition of macroevolution varies by speciation (forming a new species). textbook. • Macroevolutionary studies focus on change that occurs at or 16 above the level of species, in contrast with microevolution, which refers to smaller evolutionary changes (typically -it can explain the evolution of more complicated described as changes in allele frequencies) within a species or population. things like the how the eye evolved • The process of speciation may fall within the purview of either, -it can explain how speciation occurs depending on the forces thought to drive it. -it can explain how populations on a broader 16 scale evolve

[See SP 7.2; Essential

environment, natural More Evolution Terms

• Species-a group of interbreeding organisms that produce viable and fertile

is able to describe speciation in in speciation describe to is able offspring in nature • Gene pool-sum total of all the genes in a given species

tion and connect it to change in • Allelic frequency-is the percent occurrence for a given allele

knowledge 1.C.2] LO 1.24 The student gene frequency, change in genetic drift. selection and/or an isolated popula

Emphasize the importance of meiosis and sexual reproduction as the driving force of evolution. Meiosis is responsible new phenotypic combinations upon which natural selection can

[See SP 6.2; act. Sources of Genetic Variation Meiosis recombines alleles in new How does variation in a population or gene pool arise? 1. Mutations, gene duplication and chromosome fusion provide the raw combinations which results in unique gametes material for evolution. 2. Meiosis and sexual reproduction produce new recombinants of phenotypes due to the way chromosomes line up on the upon which natural selection operates.

The wisteria pictured metaphase plate and crossing over. Meiosis 18 on the right has a mutation causing it coupled with fertilization produces offspring to produce white flowers instead of purple flowers. with different combinations of alleles. The genetic complement that the zygote receives will

18 be different from either parent and is different

from any sibling. Identical twins are genetically identical to one another but the likelihood that two siblings (not identical twins) will be is able to construct an explanation of the multiple multiple the of explanation an construct to is able genetically identical is extremely remote 223 × 223. Tell students that the genetic “shuffling” during meiosis is like getting a new hand when playing cards. processes that increase variation within a population. population. a within variation increase that processes LO 3.28 The student Essential knowledge 3.C.2] 01 Microevolution Unique Gene Pools TEACHER NOTES Types of Mutations

• MOST mutations are deleterious as well as recessive. • Obviously, mutations occurring in Emphasize that mutations lead to genetic somatic cells do not affect future generations. variation. These next slides explain each of these 19 • Only mutations occurring in mutation types. Students should have prior gametes affect future generations. Mutations may cause sheep to have a 5th • Mutations can occur at either the But this is not evoluti knowledge of genes, DNA, and mutations from gene or chromosomal level. Pre-AP Biology.

Point Mutations: Synonymous vs. Nonsynonymous Point mutations occur when one Students should be aware of DNA, RNA, nucleotide is substituted for another. The genetic code contains “synonyms” for codons, amino acids and the mechanisms of the coding of amino acids. For example the DNA codons GGA, GGG, GGT, GGC all code for the amino acid proline. protein synthesis. If it has been a year or two Therefore, as long as the codon has GG in 20 positions 1 & 2, a mutation in position three since their first biology course, you may have to has no consequence, proline will be coded le processes that increase variation within within variation increase that processes le for regardless. refresh their memory. Also, it’s the synonyms This sort of mutation is called a when expressed as a phenotype, provides synonymous or silent mutation. (pun intended) that will confuse students—too bad we can’t decide on a single term to describe 20 a single anomaly!

Point Mutations: Synonymous vs. Nonsynonymous

Point mutations that do result in a different amino acid are called a nonsynonymous or [See SP 6.4, 7.2; Essential knowledge 3.C.1] missense mutations. Missense mutations can affect the protein in one of THREE ways: (Remember the new amino acid will have a different R group on the protein) 1. It can result in a protein that does not Emphasize that intermolecular force interactions 21 function as well as the original protein. (This happens most often.) between R groups establish the shape of a 2. It can result in a protein that functions better than the original protein. protein, thus establishing its function. 3. It can result in a protein that functions like the original protein. This is usually because the R groups are similar. (both polar or both nonpolar, etc.)

Gene Duplication able to construct an explanation of the multip the of explanation an construct to able able to predict how a change in genotype, how predict to able Genes can be duplicated and occasionally the duplication moves a gene from one chromosome to another. Each gene will accumulate different mutations altering the protein that is subsequently synthesized. Analogy: Evolution is more like editing a book Myoglobin is a protein that binds with oxygen in the muscles. This gene has been duplicated and modified many times. It has given rise to the hemoglobin rather than writing a book from scratch. Genes gene. are duplicated and then moved; once duplicated

22 [See SP 6.2; Essential knowledge 3.C.2] genes are moved, they experience different mutations which can result in different proteins. As you might imagine, there can also be cutting

22 and pasting or copying and pasting errors!

variation that can be subject to natural selection. selection. natural to subject be can that variation LO 3.28 The student is a population. LO 3.24 The student is 01 Microevolution Unique Gene Pools TEACHER NOTES Neutral Mutations

Naturally evolving proteins gradually accumulate mutations while continuing to fold into stable structures.

This process of neutral evolution is an important mode o genetic change and forms the basis for the molecular clock. 23 • Cytochrome c is a small protein found on the mitochondrial membrane. This is illustrating that there are some proteins • Between mammals and reptiles there are 15 different that have been around for a “long time”. That amino acids or mutations. being the case, over time, these proteins 23 experience mutations that do not affect the function of a protein. For example both human and dog hemoglobin found in red blood cells Neutral Mutations carry oxygen, yet the two proteins vary only • Mammals and reptiles diverged 265 million years ago. slightly in their amino acid sequencing. • That means on average cytochrome c mutated every 17 million years. • In comparing the evolution of other organisms and their cytochrome c Cytochrome c is an example of this as well. The one mutation every 17 million years holds true. average rate of these mutations can be used as an 24 evolutionary clock. le processes that increase variation within within variation increase that processes le when expressed as a phenotype, provides

Changes in Cytochrome C [See SP 6.4, 7.2; Essential knowledge 3.C.1] Explain that a pseudogene is a gene that has been duplicated but certain mutations have rendered 25 this gene nonfunctional so it is never transcribed

Above is a comparison ancestral cytochrome c and human cytochrome c. or translated. It is part of the genome that is This gene has been highly conserved as it is a protein used in the electron transport chain of the mitochondria. Missense mutations occur more frequently in pseudogenes (genes that have been duplicated, then mutated simply conserved. and are no longer functional) than in functional genes.

Cytochrome c Comparison able to construct an explanation of the multip the of explanation an construct to able

able to predict how a change in genotype, how predict to able Molecular homology of cytochrome c (see three-letter code of amino acids) 1 6 10 14 17 18 20 Human Gly Asp Val Glu Lys Gly Lys Lys Ile Phe Ile Met Lys Cys Ser Gln Cys His Thr Val Glu Pig ------Val Gln - - Ala ------Chicken - - Ile ------Val Gln ------Dogfish ------Val - Val Gln - - Ala ------Drosophila <<< ------Leu Val Gln Arg Ala ------Wheat <<< - Asn Pro Asp Ala - Ala - - - Lys Thr - - Ala - - - - - Asp Yeast <<< - Ser Ala Lys - - Ala Thr Leu - Lys Thr Arg - Glu Leu - - - - -

• A dash indicates that the amino acid is the same one found at that position in human molecule. Assign the Amino Acid Sequences and

26 [See SP 6.2; Essential knowledge 3.C.2] • All the vertebrate cytochromes (the first four) start with glycine (Gly). Evolutionary Relationships activity as • The Drosophila, wheat, and yeast cytochromes have several amino acids that precede the sequence shown here (indicated by <<<). homework! • In every case, the heme group of the cytochrome is attached to Cys-14 and Cys-17 (human numbering).

variation that can be subject to natural selection. selection. natural to subject be can that variation a population. LO 3.24 The student is LO 3.28 The student is 01 Microevolution Unique Gene Pools TEACHER NOTES Hemoglobin Comparison Ask the students to speculate as to why soybeans This is a comparison between the Human beta chain 0 • differences in the amino acid Gorilla 1 sequence of human hemoglobin might have a protein similar to hemoglobin. Gibbon 2 and different species. Rhesus monkey 8 Dog 15 • The last three species do not have Horse, cow 25 distinction between α and β chain Leghemoglobin removes oxygen that would kill Mouse 27 27 • There is an inverse relationship Gray kangaroo 38 between the difference in the a bacteria living in the root of the soybean. This Chicken 45 amino acid sequence and how Frog 67

closely related the organisms are bacterium “fixes” nitrogen in the roots of the Lamprey 125 humans. Sea slug (a mollusk) 127 Soybean (leghemoglobin) 124 • The β chain of hemoglobin has soybean or takes nitrogen from the air and 146 amino acids. 27 changes it into a usable form that the plant can use.

Hemoglobin Comparison

28 A nice visual representation of the biochemical le processes that increase variation within within variation increase that processes le differences. when expressed as a phenotype, provides

Frameshift Mutation

• A frameshift mutation occurs as a result of either an insertion o

[See SP 6.4, 7.2; Essential knowledge 3.C.1] deletion of a nucleotide. • This changes the amino acid sequence of the protein from that po forward. • Almost all frame shift mutations are deleterious. Interesting example but emphasize that most 29 • Recently, bacteria were found growing in a pool of nylon wastes (Flavobacterium) frameshift mutations do not result in a functional • These bacteria were actually digesting the nylon waste. protein. • Upon examining the genome of these bacteria, it was found there was a frameshift mutation in their DNA that caused the productio of three different enzymes that could digest the nylon.

Evolution of Hemoglobin Gene able to construct an explanation of the multip the of explanation an construct to able able to predict how a change in genotype, how predict to able

Take some time to explain this and the evolution

30 [See SP 6.2; Essential knowledge 3.C.2] of hemoglobin genes. It drives home the point that genes are duplicated and experience different mutations.

There have also been major change in chromosome structure that result changes within populations which can, in turn, result in the emergence of new species. These include: 31 a. inversions b. deletions c. duplication d. translocations e. fusions 31 Chromosomal rearrangement is another source of genetic variation.

Chromosomal Rearrangement

Compare the karyotype of a human (H) and a chimpanzee (C). Notice the great apes have 24 pairs of chromosomes compared to 23 pairs of chromosomes in a 32 human. Why the difference? le processes that increase variation within within variation increase that processes le Chromosome #2 in the human is

when expressed as a phenotype, provides the result of a fusion of two chimpanzee chromosomes.

Human Impact on Gene Pools [See SP 6.4, 7.2; Essential knowledge 3.C.1] Ask students to give examples of artificial 33 selection. They should come up with dog breeding, horse breeding, disease-resistant crops, It is well documented that humans have had an impact on certain gene pools. etc. For example, humans have selected for certain desirable traits within the mustar family and cultivated different agricultural products for human consumption.

Artificial Selection able to construct an explanation of the multip the of explanation an construct to able able to predict how a change in genotype, how predict to able When humans manipulate a gene pool it is called artificial selection. There are often consequences involved in such manipulations. For example in agriculture farmers try to increase crop production, which may lead to many farmers growin only one variety of a particular crop such as corn. This leads to a loss of genetic Emphasize the point that artificial selection can diversity. If a disease attacks that particular variety of corn, the farmers growing that variety lose their entire crop. lead to the loss of genetic diversity. This has led

34 [See SP 6.2; Essential knowledge 3.C.2] to the creation of the Svalbard Global Seed Vault which on an island off of Norway. It is a place where seeds are kept and maintained to preserve genetic diversity.

• When antibiotics are applied to a population of microorganisms treat an infection, some of the microorganisms may be naturally immune to the drug. • Why? A random mutation occurred in the genetic code of the This concept of “things” becoming resistant to microorganism conferring its resistance. some sort of human treatment as a result of 35 • These resistant microorganisms continue to flourish and cause disease. artificial selection is important. Examples of this • The only remaining option a physician has is to treat the infectio with a different antibiotic and hope that none of the surviving include antibiotic resistant bacteria, herbicide microorganisms possess a different random mutation that makes them resistant to the second antibiotic as well. resistant weeds and insecticide resistant insects.

The mechanism pictured is that of penicillin. (note the artist’s use of the “P”s). It is

nisms and phenotypic variations Antibiotics and Artificial Selection illustrating how the drug attacks a bacterial pathogen. • The increase in antibiotic- resistant bacteria has caused doctors to reduce the number There are many related topics of discussion you of prescriptions written for can explore with students if time permits such as: 36 antibiotics in general. • About 70% of pathogenic Are we overusing antibiotics? Is it a good idea bacteria are resistant to at least one antibiotic and are to let your immune system struggle for a few called “super bugs” or MDR bacteria. (multidrug resistant) days at the first sign of a cold? If fever is our

36 immune system’s first response to infection, what purpose is it serving?

tween genetic variations in orga tween genetic variations MRSA or Methicillin-resistant Staphylococcus aureus • MDR bacteria do not respond to “first line of defense” antibiotics. • These types of bacteria are most commonly found in hospitals. Depending upon where you live, MDR bacteria 37 • Skin boils or similar lesions that do not heal are also commonly found on sports equipment in often result. • MDR bacteria can attack locker rooms as well as nail salons. internal organs upon gaining entry into the body. 37

Reducing or Eliminating Gene Pools able to explain the connection be • Human activities often augment genetic drift and diminish gene flow for many species. Just interesting…Collared lizards in the wild • This reduces genetic variation thereby disrupting adaptive processes both locally have been the subject of a number of studies of and globally within a species.

[See SP 7.2; Essential knowledge 3.C.1] • This impact is illustrated within populations sexual selection. In captivity if two males are 38 of collared lizards (Crotaphytus collaris) living in the Missouri Ozarks. placed in the same cage they will fight to the • Forest fire suppression has reduced habitat and disrupted gene flow in this lizard, thereby death. Males have a blue-green body with a light altering the balance toward drift and away from gene flow. This balance can be restored brown head. Females have a light brown head by managed landscape burns. 38 and body.

LO 3.26 The student is in populations. 01 Microevolution Unique Gene Pools TEACHER NOTES Ask students “Why TWO to the 23rd?” First, they should know that humans have 46 chromosomes which can be arranged into 23 [See Effect of Sexual Reproduction pairs with the “last” pair being XX if female and XY if male. Since gametes are haploid, they have Sexual reproduction recombines genes in new ways. This results in unique offspring that differ from either parent or sibling. Humans make 223 different kinds of gametes. Fertilization means that the uniqueness of an individual is only 23 chromosomes. 223 × 223. Or the probability that two siblings will be genetically identical (excluding identical twins) is 446. [See SP 6.2; We use 2 because there are 2 chromosomes in a 39 pair, and you have 23 pairs. In order to figure out the probability you raise 2 to the 23rd power, Sexual reproduction is like shuffling a deck of cards and every time getting a new and unique hand dealt. It is the major driving which gives you 8.3 million different force of evolution.

39 possibilities for only the egg or sperm. So, if you the connection between take 8.3 million times 8.3 million, you get 64 trillion different possibilities for fertilization, rsity necessary for evolution. without even considering crossing over. That’s a lot of unique phenotypes upon which natural

selection can act! able to represent is able to construct an explanation of the multiple multiple the of explanation an construct to is able

Created by:

Carol Leibl 40 Science Content Director National Math and Science

SP 7.1; Essential knowledge 3.A.2] LO 3.10 The student is LO 3.28 The student population. a within variation increase that processes meiosis and increased genetic dive Essential knowledge 3.C.2]