AP Biology Course Review Part 3

7.1 Introduction to Natural Selection 

• Evolution: the change in the genetic makeup of a population over time and is supported by multiple lines of evidence 

• Natural Selection: the process by which organisms, having adaptations suited for a particular environment, having a greater chance of survival and reproduction, thereby passing the adaptations to subsequent generations

  • Charles darwin credited with theory

    • Pop grow exponentially and overpopulate, exceeding their resources

    • Overpopulation results in competition/struggle for existence

    • Evolution occurs as advantages traits accumulate in a population

    • Populations contain variance and unequal fitness

    • Best-fit individuals survive and get to pass on their traits to offspring

Competition for Limited Resources

• Competition: when organisms struggles with other organisms to get limited resources

  • Compete for resources such as space, food, mates, nutrients, light

  • Differences in phenotypes= how competitive an organism is

    • Differential survival

Favorable Phenotypes Improve Chances of Survival

• Variation: refers to genetic differences among organisms within a population

  • Mutations and sexual reproduction increase variation within populations

• Adaptations: traits that provide an advantage in a particular environment

  • Individuals with adaptations have a greater chance of survival and reproduction

  • # of individuals within a pop having adaptations can increase over time

Evolutionary Fitness is measured by reproductive fitness

• Fitness:ability of an organism to survive and produce fertile/viable offspring0

• Reproductive success: production of offspring

  • Over several generations is a component of evolutionary fitness

• Heritability: ability to pass on adaptations to successive generations

  • Due to selection, the traits of individuals that have more reproductive success become more common in the pop

Ecosystem stability determines the rate and direction of evolution

• Biotic and abiotic that can be more or less table

  • Environments can experience major disruptions and change quickly or change slowly  over time

  • Populations are less likely to evolve in environments that remain stable over long periods of time

  • Unstable environment>faster rate of evolution

Evolution leads to quiet crickets in Kauai

• Variation: males have specially shaped wings with a scraper and teeth that produce a chirp when rubbed together

  • Due to random mutation, some male crickets with a mutation are silent like females

• Heritability: both traits are heritable

• Competition: males compete for mates and chripring males have reproductive success

• Biotic factors: one islands has an invasive fly species lays maggots on the back of crickets

  • The maggots burrow into the crickets and emerge week later>kills crickets

  • Flys use sound to locate crickets

  • Natural selection>> silent male crickets are likely to survive to reproduce because flies can't find them to lay eggs on

1. Using a diagram, create an illustrated model of the process of natural selection.  Your diagram should include representation of the following principles: 

• Variation among organisms

• Competition 

• Adaptation

• Overproduction of offspring

• Limited environmental resources

• “fitness”

2. Explain what is meant by the two phrases “differential survival” and “reproductive success”. 

   1. Differential survival is the difference in the phenotype of organisms in response to their environmental competition for resources such as space, food, mating, nutrients, light, etc. Reproductive success is the measure of the production of offspring which is seen over several generations.

3. Explain what it means for an organism to have “fitness,” and how this affects members of a population.

   1. When an organism has “fitness”, it means the organisms of the population have the ability to survive and produce fertile offspring which is how the population continues- without the ability to produce viable offspring, the population would not be able to continue

4. Explain how evolution led to the development of quiet crickets in Kauai.

   1. The change in the genetic makeup of a population overtime, or evolution led to the development of quiet crickets in Kauai because due to the competition for mates and the success for the silent male crickets are flies could not lay eggs on them, the allele for silent male crickets increased producing a population consisting of mainly quieter male crickets. 

7.2 Natural Selection

Natural Selection acts on Phenotypic Variations in Populations

• Genetic variation: genotypic and phenotypic differences between individuals in a population

  • Genetic variation>> different phenotypes and/or adaptations

• Due to natural selection, individuals with more favorable traits are more likely to survive to reproduce

• Genetic variation increases the prob a pop of organisms will survive under changing environmental conditions

  • If environment changes>one of phenotypes may be better suited for the changed condition

Types of Selection

• Stabilizing selection: eliminates extremes (reduces variance) and makes tall peak

• Diversifying selection: extremes grow and intermediates decrease (may lead to 2 species)

• Directional selection: entire population shifts one way due to change in allele frequency

Environments change and apply selective pressures to populations

• Selective pressure: any biotic or abiotic factors influencing survivability (disease, predation, climate, food availability)

• Changing environments introduce different selective pressures on populations 

  • Individual fitness relative to the environmental conditions

  • Phenotypes selected for can be selected against when environmental conditions change and vice versa

Environments change and apply selective pressures to populations

• England: peppered moths vary in color

• After industrial revolution> soot from coal-burning factories and homes covered many trees

  • Result: darker-colored moths were well camouflaged and more likely to survive to reproduce

    • Over time, dark-colored phenotype became most common with pop of moths

  • After clean air act was passed, lighter phenotype became more common once again

Some phenotypic variations significantly increase or decrease fitness of the organism

• Fitness: reproductive success over generations

  • Phenotype that decreases chances of survival/reproduction>> negatively impacts fitness

  • Phenotype that increases chances of survival/reproduction>> positively impacts

DDT Resistance Significantly Increases Fitness of Insect Populations

• DDT was commonly used insecticide to combat insect-borne diseases (banned in US in 1972)

  • Still used in some countries to combat malaria (through mosquitos)

• Natural Variation>> some individual insects are resistance to DDT

  • Resistant individuals are not killed by DDT and survive to pass on resistance to offspring

  • Over time: entire populations of insects can become resistant since those individuals survive to pass on their traits

1. Explain why populations are the smallest units of life that can evolve.

   1. Populations are the smallest unit of life that can evolve because it is a group of the same organisms that interbreed to create the next generation through natural selection.

2. Describe what a selective pressure is, and how selective pressures are responsible for: 

   1. Directional selection

   2. Stabilizing selection

   3. Disruptive selection 

      1. Selective pressure is any biotic or abiotic factor influencing survivability; directional selection is when am entire population shifts one way due to a change in allele frequency, disruptive selection is when extremes grow and the middle intermediate decreases, and stabilizing selection is when the extremes are eliminated and makes a tall peak.

3. Explain how the following factors can affect the evolution of species: 

   1. the environment 

   2. mutations in genes

   3. fitness of organisms 

   4. human activities 

      1. The changing environments introduces new selective pressures that changes the selection of a certain allele in what it favors; mutations in genes result in the introduction of a new phenotype that may also be favored and change the phenotype of a species; the fitness of an organism also affects the evolution of species as the inability to produce viable offspring hinders the growth of a population; human activities such as the use of DDT also affects the natural variation of animals as some are resistant to the DDT while others are not.

4. Identify the cause of variation in populations and how this creates new phenotypes that natural selection can act on.

• The cause of variation in populations is selective pressures that may include diseases, predations, climate, food availability, etc, which favors certain phenotypes or alleles or a species that would have a greater chance of survival and reproduction to pass those adaptations to subsequent generations.

5. Explain how it is possible for these mosquitos to also become resistant to the pesticide DUET.

• It is possible for the mosquitos to also become resistant to the pesticide DUET because the mosquitos that are resistant to the DUET pesticide will be able to survive and pass on the resistance gene to the offspring, while the insects that are not will die that will overtime create a population of mosquitos that can become resistant since those that survive can pass on their traits

6. Describe how the Industrial Revolution influenced changes in the peppered moth population in England’s forests during the 19th and 20th centuries.  Explain how it was possible for the Clean Air Act to affect changes in the fitness of the moths.

• The Clean Air Act was able to reduce the pollution and started to favor the lighter colored moths in comparison to the darker color moths that were favored previous to the Clean Air Act; so after, the lighter color moths were more abundant as they were able to blend in, survive, and reproduce.

7.3 Artificial Selection

Through Artificial selection, humans affect variation in other species

• Artificial selection: process by which humans select desirable traits in other species and selectively breed individuals with the desired traits

  • Agricultural or economic practices ( growing certain crops with specific characteristics breeding certain animals for sport or sale)

  • May result in phenotype that would not otherwise exist in nature

  • Can lead to more OR less genetic diversity

  • Humans can select any trait (or combination of traits) as desirable, and choose to breed individuals within the populations to get desired outcome

    • Depending on which traits are selected for and how often, the genetic diversity of population can change over time

Similar Selective pressures result in similar phenotypic adaptations

• Convergent evolution: process by which similar environmental conditions select for similar traits in different populations or different species over time

  • Can be observed in distantly or unrelated

    • Referred to as analogous structures

    • ex. Selective pressure of similar aquatic environments can select for streamlined bodies in vertebrates like fish and mammals

1. Artificial selection can remove harmful characteristics from a population while preserving favorable ones.  Explain how this can affect genetic diversity of a population and why this can put a population at risk for extinction.

   1. Artificial selection can affect genetic diversity of a population because when one trait is bred for, it decreases genetic diversity or the traits that were not wanted and it can put a population at risk of extinction in the case of an extreme change as there will not be any other adaptation that may be able to survive.

2. Explain what convergent evolution is and give example of it.

   1. Convergent evolution is when similar environmental conditions select for similar traits in different populations over time and an example are birds and bats that both have wings that serve the same function but have evolved differently.

3. Longhorn cattle are the descendants of cattle that were brought to the Americas by Columbus in 1493.  These particular cattle were eventually brought to Mexico and some escaped to form feral cattle herds who were subject to predation by bears, wolves and mountain lions.  It was observed that the cattle with longer horns had higher survival rates and that the horn length in the population of cattle was increasing over time.  Explain how artificial selection has been used to maintain the length of horns in Longhorn cattle.  

   1. Artificial selection can include the breeding of the longhorn cattle with longer horns to maintain the length and survivability/viability of later generations.

7.4 Population Genetics

Evolution is driven by random occurrences

• A mutation is a random change in an organism’s genome

  • Alteration in a DNA sequence

  • Can contribute to changes in the genetic makeup of a population over time

  • Creates genetic variation within a population

  • Provides new phenotypes that contribute to evolution by natural selection

• Genetic drift is a nonselective process occurring in small populations

  • Founder effect refers to a random process that reduces genetic variation within a small pop due to separation from a larger pop

    • Migration + geological events can isolate populations 

    • Genetic makeup of a founder pop can be different from original pop

• Migration/gene flow: movement of individuals between populations causing exchange of alleles between populations

  • Introduces new gene into populations= increases genetic variation

  • Continued migration between populations REDUCES genetic diversity between populations over time 

  • Adds or subtracts alleles from the pop

Reduction of genetic variation can increase the differences between populations of the same species

• Genetic drift: random change in the frequency of a particular allele within a population

  • Non-selective process generally occurring in small populations

    • Increased death rates + low reproductive rates

    • Natural catastrophes (fires, volcanic eruptions, etc,)

• Bottleneck events can contribute to genetic drift

  • A large, diverse population suddenly reduced to small population

  • Smaller pop more susceptible

Random processes play a role in the evolution of specific populations

• Genetic variation is the raw material of evolution

• Fitness is relative to specific environmental conditions

  • As conditions change, fitness can change

  • Different phenotypes can be selected for or against according to changes in the environment

  • Evolution in a population cannot occur if there is no genetic variation within the population

• Null hypothesis: hypothesis that states experimental variables have NO relationship and experimental observations are the result of chance

• Alternative hypothesis: one of several hypothesis stating experimental variables have a relationship and the experimental observations are the result of some nonrandom cause

1. Describe the process of genetic drift.  Explain why genetic drift takes place less often in a large population.

   1. Genetic drift is a nonselective process that occurs in small populations that takes place less often in a large population because larger populations have a larger gene pool that may not be any loss of genetic variation to reduce the effects in comparison to a smaller population

2. Compare and contrast the founder effect with a bottleneck event and describe how they both affect the allele frequencies in a gene pool.

   1. The founder effect is a random process that reduces genetic variation to start a new population such as migration while a bottleneck event is when a larger population is reduced to a small population.

3. Describe the difference between genetic drift and gene flow.

   1. Genetic drift is when there is a random change in the frequency of a particular allele within a population by either the bottleneck effect or founder effect; while gene flow is the movement of individuals between populations causing the exchange of alleles between populations (migration)

4. Explain what it means for an organism to have “fitness,” and how this affects members of a population.

   1. When an organism has “fitness”, it means the organisms of the population have the ability to survive and produce fertile offspring which is how the population continues- without the ability to produce viable offspring, the population would not be able to continue

5. Explain how mutations may actually benefit members of a population.

   1. Mutations may actually benefit members of a population because the introduction of a new trait may be more favored in an environment that may change the allele frequency of a population that may be more suited for a niche in comparison to other species

6. Explain how natural selection results in an increase in the frequency of beneficial alleles in a population over time, and a decrease in the frequency of deleterious (harmful) alleles.

   1. Natural selection may increase in the frequency of beneficial alleles because the adaptation which is suited better for a particular environment are able to survive and reproduce, passing on that trait that will decrease the frequency of the deleterious allele.

7. Describe how mutations contribute to the evolution of a population.

   1. Mutations change the expression of the protein that introduces a new allele to a population that can be passed onto the next generation that may be favored or deleterious and increases genetic diversity.

8. Explain how the process of sexual reproduction affects the evolutionary process.

   1. Sexual reproduction increases the genetic diversity- when an organism that has a favored trait and mates with other organisms, there is a higher chance of passing on the favorable trait to affect the evolutionary process in the favor of one trait or another.

7.5 Hardy-Weinberg Equilibrium

What is the Hardy-Weinberg modelF used to describe? And predicting allele frequencies in a non evolving population

• A population in hardy weinberg equilibrium is NOT evolving

  • Frequencies of alleles and genotypes stay the same generation after generation

1. List the five conditions necessary for Hardy-Weinberg equilibrium 

• Large population = no genetic drift

  • There is a sampling error in small populations; they are not representative of the entire pop and thus genetic drift is likely to occur

• No mutations = no gene flow

  • No mutations can occur b/c mutations can introduce a trait that may be favored/selected or or it could be selected against

• No net migration = no genes are modified, deleted, or duplicated

  • When organisms enter/leave a population, they bring their DNA/genes with them. They may have characteristics that are selected for/against, causing natural selection (NOT ALLOWED AT GENETIC EQUILIBRIUm)

• Random mating = no sexual selection

  • Otherwise organisms are choosing mates based on favored characteristics (selection)

• Absence of selection = no natural selection

  • Provide a null hypothesis

  • Cannot be selection otherwise traits that are favored may increase in the population, shifting allele frequencies; traits selected against will also shift allele frequencies

2. p2 + 2pq + q2 is used to determine genotype and/or phenotype frequencies of individuals in a population

• p2 =frequency of the homozygous dominant genotype

• 2pq =frequency of the heterozygous  genotype

• q2 =frequency of the homozygous recessive genotype

3. p + q = 1 is used to determine the frequency of a particular allele in a population

• p=frequency of the dominant allele

• q= frequency of the recessive allele

• percent/proportion> give a percent %

• Frequency of allele or genotype> give decimal value (0 to 1)

• Number of individuals> take proportion and multiply by total in population

4. Changes in allele frequencies provide evidence for the occurrence of evolution in a population

5. Describe five factors that can disrupt the Hardy-Weinberg equilibrium

• Mutations: changes in genes can occur through random events that delete, insert or substitute nucleotides

• Non-random mating: individuals choose to mate with another based on certain traits

• Gene flow: new genes can be introduced to populations

  • Migration of individuals in or out of a population

• Genetic drift: changes in the allele frequency within a population can occur due to random environmental events

  • Bottleneck and founder effect

• Natural selection: alleles improve or reduce fitness for individuals to survive and reproduce in a given environment 

6. If p = 0.2, and q = 0.8, give the frequencies of the following:

   1. Homozygous dominant genotype 

• p2 + 2pq + q2= 1; 0.2^2=0.04 or 4%

2. Heterozygous genotype Aa

3. Homozygous recessive genotype

• p^2 0.8^2=0.64

4. Dominant phenotype A

1. The Hardy-Weinberg equilibrium is a mathematical model used to study the allele frequencies in a population.  Explain why such a model is a valuable tool for studying the gene pools of real populations.  

   1. The hardy-weinberg equilibrium is a valuable tool for studying the gene pools of real populations as not all populations evolve or changing in a short period of time, which is calculated in the equation that is used when the population is not evolving and the frequencies of alleles and genotypes stay the same generation after generation

2. Using a drawing, illustrate and explain how each of the following mechanisms can affect allele frequencies in a population: 

   1. Mutation: introduces new alleles into a population gene pool that changes the favorability of genes in a population

   2. gene flow: migration of organisms introduces new genes into populations to increase genetic variation while the continued migration between populations reduces the genetic variation

   3. genetic drift: the random change such as natural catastrophic events change the frequency of a particular allele within a population

   4. nonrandom mating : the preference to mate with particular characteristics will create a greater allele frequency of those that are selected for 

   5. selection (natural or otherwise): When a certain allele or gene is favored in an environment, they would be more fit and reproduce to increase the allele frequency of the organisms that can survive and reproduce

3. Explain why heterozygotes can have survival advantages over homozygotes in a population. 

   1. Heterozygotes can have a survival advantage over homozygotes in a population as they have a higher fitness and whatever allele is not chosen for can still be passed on to the next generation such as sickle cell and the heterozygotes not showing symptoms. 

4. Explain how each of the following affect the allele frequency of a population:

   1. Small population: they have less genetic variance and are subject to catastrophic events that can greatly reduce the allele frequency of the population

   2. Large population: because it is assumed that there are more organisms in the population, they are less susceptible to change in the allele frequency as there are organisms that can reproduce to make up for any losses in the gene pool

   3. Sexual selection: the frequency of the population can change much similarly like natural selection in which it may be directional selection.

7.6 Evidence for Evolution

What is the difference between an extant and extinct species?

• Extinct is a species no longer alive; extant is a living species of a class of animals

What are some ways fossils can be dated?

• Age of the rocks where a fossil is found

• The rate if decay of isotopes including carbon-14

• Geographical data

• Morphological traits represent modified traits shared among different species

What are the differences between homologous structures, vestigial structures, and analogous structures?

• Homologous structures: variation in a structure that was present in a common ancestor

  • Ex. bone structure of humans, cat legs, horse legs, bat wings, dolphin fins

• Vestigial structure: reduced or obsolete feature that serve little or no purpose for the organism

  • Ex. bone structure for legs in some snakes, human tailbone

• Analogous structures: structures that evolved independently in different species due to similar environmental conditions/selective pressures (SAME PURPOSE like bat/bird wings)

List the three pieces of biochemical evidence discussed in the video:

• Comparison of DNA nucleotide sequences or amino acid sequences

  • Share same/similar genetic code; process of gene expression; same genetic language of DNA and RNA

  • DNA/ RNA are carriers of genetic information through transcription, translation, and replication

  • Major features of genetic code are shared among all modern living system

  • Metabolic pathways to produce ATP are conserved across all domains (glycolysis)

The more amino acid differences in a protein shared by different species, the more time has passed since their divergence.

1. Describe how the following pieces of evidence for evolution support Darwin’s theory of evolution through natural selection, and give an example of each: 

2. Geographical: evidence based on characteristics of a habitat or land area (such as the galapagos finches)

3. Geological: evidence based on environmental features of the land over time (Fossils document patterns of evolution and changes in environmental conditions over time)

4. Physical: evidence based on phenotypes of species

5. Biochemical: evidence based on the chemical composition of living things (Comparison of biomolecules such as DNA and proteins)

6. Mathematical: evidence based on calculations and statistics (Mathematical models and simulations are used to illustrate and support evolution)

      2. Explain why fossil remains can be used as evidence of evolution and how they are dated.

Fossil remains can be used as evidence of evolution by seeing the structures to compare with modern animal structures to see homologous, analogous, and vestigial structures. 

      3. Explain how the pentadactyl (5 digits) limb and vestigial structures both provide evidence for common ancestry in vertebrates.

• The pentadactyl limb and vestigial structure is when and organism has evolved and there is now a reduced or obsolete feature that serves little to no purpose for the organism; and it is used to provide evidence of common ancestry because the bone structure for certain organisms may show that their previous ancestors may have had the same trait and can be similarly compared to other current organisms to find common ancestry based off of traits 

      4. Describe how analogous structures are different than homologous structures.  Which one indicates evolution in a common environment?

• Analogous structures are different from homologous structures because analogous structures are developed in different species as a result of similar environmental pressures while homologous structures are the variation of a structure that was present in a common ancestor. Analogous indicates evolution in a common environment because the selective pressures from the environmental conditions cause evolution or change over generations.

      5. Think back on what you have learned so far. Explain how the following processes provide evidence for common ancestry among living organisms:

1. Cellular Respiration: Most organisms that perform cellular respiration have most likely have evolved from a common ancestor and was selected for rather than independently evolving

2. Cell Signaling: cell signalling is used to respond to changes in an environment, so common ancestors may have responded differently to the environmental conditions to create different structures in species but can still be compared biochemically to find common ancestors 

3. Cell Division: cell division results in the increased gene pool or diversity which can be proves that the different structures of organisms is created through the numerous cell divisions created from reproduction

4. Gene Expression: gene expression is dependent on the organisms but provides evidence  for common ancestry among living organisms as the difference in what structure is expressed can be different but can also be similar because once again- the environment can prompt different gene expression for organisms to diverge away from the typical organism phenotype

7.7 Common Ancestry

1. List three types of structural evidence supports common ancestry of all eukaryotes.

• membrane -bound organelles

• Linear chromosomes

  • Contain nucleus

• Genes that contain introns

  • Do not code for proteins

  • RNA processing removes introns  prior to protein synthesis

2. What are the structural similarities of chloroplasts and mitochondria?

• Have double-membrane

• Contain circular genomes

• Contain ribosomes

• Endosymbiotic theory> describes process and evidence supporting similarities

3. What is the endosymbiotic theory?

Organelles such as mitochondria and chloroplasts were one prokaryotic cells as they are the same size as prokaryotic cells, use binary fission, and have their own circular DNA

4. How are eukaryotic genomes different from prokaryotic genomes?

• Eukaryotes have multiple linear chromosomes

  • Made up of tightly coiled DNA with histone proteins

  • Capped with telomeres

  • Found inside nucleus

  • Genomes are large

• Prokaryotic genomes: 

  • Contain single circular chromosomes

  • Occurs in the cytoplasm

  • Genomes are small

• Describe how the following items indicate common ancestry for all eukaryotes on Earth: 

  • Membrane bound organelles (endosymbiosis): membrane bound organelles such as mitochondria are found in almost all eukaryotic cells and shows common ancestry as they  have the ability to use binary fission to replicate which is a similarity between chloroplasts and mitochondria (in animal and plants cells) 

  • Linear chromosomes: most eukaryotic cells also have linear chromosomes which means that the common organism that the organisms descended from also had the same trait of having linear chromosomes that contain the nucleus

  • Genes containing introns: most eukaryotes also have a common genetic code but the removal for introns prior to protein synthesis is what causes the difference in the phenotype of the organisms which also show that most eukaryotic organism have common ancestry because of the same or similar DNA

7.8 Continuing Evolution

How has it been determined that all life has evolved and continues to evolve?

Evolution is an ongoing process in all living organisms

• Example: the finches of the Galapagos Islands

Genomic changes over time lead to all species’ evolution

• Mechanisms of genetic change include:

  • Changes in DNA:

    • Gene mutations + chromosomal mutations

• Cell division:

• Sexual reproduction increases game diversity; independent assortment; crossing over

• Environmental disruptions:

  • Sudden changes in environment; changes in allele and/or gene frequencies within a population

Continuous change in the fossil record is evidence of continued evolution

• Fossils: preservation/ impression of an organism that lived in the past

  • Provide a record of an organism over time

  • Strata layers arrange fossils in the order they were deposited

  • New fossils mark changes in the environment

    • New selective pressure>changes in frequency of certain adaptations in a given population

    • Transition fossils can show the evolutionary changes as one group evolves into another

  • fossils>> incomplete chronicle of evolutionary change

How does resistance contribute to evolution?

Resistance to various chemicals= species’ evolution

• Evolution of resistance to chemicals evident through natural selection

  • Mutations can result in resistance

  • Resistant organisms could be selected for under conditions where the trait is advantageous

  • Frequency of resistance can increase within pop over time if trait provides better fitness

• Evolution of resistance to antibiotics, herbicides, chemotherapy drugs is an ongoing process

How do pathogens contribute to the evolution of other populations?

• Pathogens: infectious agent that can produce a disease 

  • Evolve and cause emergent diseases

  • Pathogenic genomes experience high mutation rates> increased diversity

• Pathogens are chemically compatible with the host and can change the phenotypes selected for/against in host population

• EX: 2009 swine flu pandemic (new strain of the H1N1 influenza subtype caused by the reassortment of the genes found in the human and swine flu)

  • H protein on the surface of the virus was originally seen in pigs

• EX: COVID-19 Pandemic (variation of the coronavirus family discovered on 2009)

  • Causes respiratory illness

• 
  

1. Describe how the fossil record is used to illustrate continuous evolutionary change.

   1. Fossil records are used to illustrate continuous evolutionary change as the observations of the structures can be compared to the previous generations to see changes between generations to conclude evolutionary change

2. Identify and explain the specific ways that genomic changes over time lead to all species’ evolution. 

   1. Genomic changes over time that lead to all species’ evolution includes changes in DNA that include mutations, independent assortment and crossing over in cell division that occurs during sexual reproduction as well as environmental disruptions that change the allele or gene frequency in a population

3. Support each of the following claims with evidence about how it is an example of evolution as a continuous process in living things:

   1. Antibiotic resistance has developed in bacteria

      1. Antibiotic resistance occurs in which the population shows reliance as some individuals can withstand the exposure to antibiotics that then pass the resistance to offspring and other bacteria in the population that changes the phenotype of the population but is continuous as other antibiotics may be used to continue the cycle.

   2. Chemotherapy resistance has developed in cancer cells

      1. Just like bacteria, cancer cells that develop drug resistance towards the chemotherapy in which the resistant cells continue to develop through the checkpoints of the cell cycle while the non resistant cells die, which creates a majority of cells being resistant as those are the ones who can survive and replicate.

   3. Pesticide resistance has developed in insects

      1. When pesticides are first used, it kills many insects that are not resistant which is the majority. But the few insects that are resistant to the pesticide survive due to the preexisting expression of the gene that creates resistance that allows them to survive and reproduce and pass on the gene for pesticide resistance- overtime the majority of the population would become resistant

   4. Genomic changes in viruses cause novel diseases 

      1. Mutation rates are often high in viruses which allows for a fast evolution with the fast reproduction cycle. For example, viruses that have previously caused diseases can be mutated to cause new diseases that have not been previously prevented by vaccines.

4. Explain how pathogens are able to cause evolution of a host population

   1. Pathogens are able to cause evolution of a host population in which they produce a disease that are chemically compatible with a host and change the phenotype selected for or against in the host population, so as reproduction continues, the allele or gene frequency may change as well as different characteristics may be chosen for that may not have been the case previously.

7.9 Phylogeny

What do phylogenetic trees and cladograms have in common? What is the difference between them?

• They both show relationships between lineages & represent hypotheses and are constantly being revised based on evidence

• Phylogenetic tree: a branched diagram showing the evolutionary relationships among species

  • Shows changes over time calibrated by fossils or a molecule clock

• Cladogram: diagram used to show evolutionary relationships amongst species

  • Includes any group on a cladogram sharing a common ancestor

What is a clade?

• Any group on a cladogram sharing a common ancestor

What do shared derived characters indicate?

• Indicate ancestry and are informative

What is an outgroup?

• Represents the lineage that is least closely related to the remainder of the organisms to provide a reference of comparison to help determine how the main group fits in the evolutionary tree of life

What does a node represent on a phylogenetic tree?  What does the root represent?

• The node is where 2 lines meet and represents the most common ancestor

• Root represents the common ancestor of all species on the phylogenetic tree or cladogram

What kind of data can be used to construct a phylogenetic tree?  Which type of data is usually more accurate?

• Morphological similarities from living or fossil species

• DNA and protein sequence similarities>molecular data typically provide more accurate/reliable evidence than morphological traits

What is a derived character?

• Trait in a recent species, having evolved from an ancestral trait (shown in tables)

1. Describe the following pieces of evidence that can be used to construct phylogenetic trees and provide two examples of each: 

   1. Morphological: using observations seen through fossils or living species can be used to determine similarities and be categorized which is not usually accurate

   2. Molecular: DNA and protein sequences of organisms can be compared to see similarities of organisms and group them in phylogenetic trees

2. A student claims that DNA evidence is more reliable than fossil evidence for construction of cladograms.  Justify the student’s claim.

   1. Using DNA evidence is more reliable than fossil evidence for the construction of cladograms as they more accurately show the similarity of the sequence to show if organisms share a common ancestor.

3. Explain why the fossil record is incomplete and why fossils are not the only evidence that should be used in determining phylogeny of a species.

   1. Fossils are not the only evidence that should be used in

4. Explain what Darwin meant when he talked about the common descent of all life, and what the significance is of the following items on a phylogenetic tree:

   1. Nodes

   2. Branche

5. Describe the difference between a phylogenetic tree and a cladogram.  

6. Describe the difference between shared characteristics and shared derived characteristics on a cladogram.  Explain what the outgroup on a cladogram is used for.  How is this used to determine relationships among groups of organisms?

7. Explain why phylogenetic trees and cladograms can be used as models to predict changes in species over time.

8. Explain how scientists are using phylogenetics to study HIV and COVID-19.  Click the link to view a phylogenetic tree of the Coronavirus.

7.10 Speciation

When does speciation occur? When populations are reproductively isolated from each other

• Speciation: the creation of new species that results in diversity of life forms

What is a species? A group capable of interbreeding and exchanging genetic information to produce viable, fertile offspring

Reproductive isolation is critical for speciation

• Biological barriers keep members of two species from interbreeding and producing fertile offspring

• Prevents gene flow between populations

What do prezygotic barriers do?

• Prevent production of a fertilized egg

• Habitat isolation: species occupy different habitats and rarely come in contact

• Temporal isolation: species breed during different times of day, seasons, or years

• Behavioral isolation: species have different courtship behaviors or mate preferences

• Mechanical isolation: reproductive structural differences prevent successful mating and reproduction

• Gamete isolation: sperm of one species may not be able to fertilize the eggs of another species

What do postzygotic barriers do?

• Prevent a zygote from developing into a viable, fertile offspring

• Hybrid inviability: mating results in zygote, but incompatibility may stop development of the zygote

• Hybrid sterility: a hybrid offspring is produced that is vigorous but may be sterile

• Hybrid breakdown: first-gen hybrids are viable and fertile but resulting generations are feeble or sterile

• EX: horse + donkey = nonviable mule

  • Usually due to differences in # of chromosomes in the games are different. Horses have 64 chromosomes and donkeys have 62, and mule at 63; during meiosis, mule cannot make viable gametes b/c of uneven chromosomes because they can't be split 

Contrast allopatric speciation with sympatric speciation.

• Allopatric speciation is the evolution of new species due to individuals from the same population being geographically isolated over a long period of time 

• Sympatric speciation is the evolution of new species due to individuals being reproductively isolated from a surviving ancestral population meaning there is no geographic barrier and may be a result of a genetic mutation, habitat differentiation, or sexual selection

What are some causes of sympatric speciation?

• Genetic mutations such as polyploidy

• Habitat differentiation

• Sexual selection

Contrast punctuated equilibrium with gradualism

• Punctuated equilibrium is evolution that occurs rapidly after a long period of stasis or period of little to no change (that may even be for long periods of time) in which changing ecological conditions are the stimulus for evolution while

• Gradualism is evolution that occurs slowly over hundreds of thousands or millions of years in which ecological conditions change gradually over a long period of time

What causes divergent evolution? Give an example

• When adaptation to new habitats results in phenotypic diversification

What is adaptive radiation?

• Evolution of new species that allows empty ecological roles or niches to filled

  • Darwin’s finches on the Galapagos island: changes in size and form of beak enabled different species of finches to utilize different food sources

1. Explain what the biological species concept is.  Why is this species concept inapplicable to asexually reproducing organisms? That species can be defined as a group of interbreeding and exchanging genetic information to produce viable, fertile offspring; this does not apply to asexually reproducing organisms as they do not interbreed or exchange genetic information to create offspring but rather create exact replicas of themselves with exact copies of the parental DNA.

2. Explain why reproductive isolation is the critical factor that keeps species separate from one another.

3. Create a t-chart that illustrates the differences between the two schools of thought regarding the rate of evolutionary change:  punctuated equilibrium versus gradualism

4. Explain how divergent evolution results in adaptive radiation. 

5. Explain how the Galapagos finches are an example of adaptive radiation.

6. Draw an example of each of the following examples of reproductive isolation caused by a prezygotic barrier.  Your drawing should explain how each type of isolation leads to the formation of a new species without using any words. 

   1. Habitat isolation 

   2. Behavioral isolation 

   3. Temporal isolation 

   4. Mechanical isolation 

   5. Gamete isolation

7. Describe the difference between a prezygotic barrier and of a postzygotic barrier.  

8. Distinguish between allopatric and sympatric speciation. 

9. Recall that sexual selection is the process by which females of a species seeking a mate select the males of their species based on an attractive appearance or behavior.  Explain how sexual selection could lead to reproductive isolation.

7.11 Extinction

What can cause extinction rates to increase?

• Extinction: disappearance of a species, such that no future generations will naturally populate the Earth

  • Naturally occur, part of history; can be onion on a small scale over long periods of time; amd serve as a marker for geological time

• They can occur on a large scale + wipe out large numbers of species at one time

  • Caused by catastrophic changes to an ecosystem such as solar flares, rising sea levels, volcanic eruptions, or asteroid impacts

  • Species diversity severely decreases

What human activities can drive catastrophic ecosystem changes?

• Habitat loss, climate change, habitat degradation, pollution, poaching, invasive species

What is speciation?

• The process by which populations of organisms become reproductively isolated and new species form

How do speciation and extinction affect species biodiversity?

• High species biodiversity= high levels of speciation and low levels of extinction

• Low species diversity = low levels of speciation and high levels of extinction

What is a niche?

• Describes the role an organism plays within its environment

  • Ex. producer, decomposer, scavenger, consumer, etc.

• When species goes extinct, it leaves an open niche for another species to occupy

  • Can lead to rapid speciation rates and adaptive radiation

    • After dinosaurs went extinct, ancestral mammal group occupies open niche and experienced adaptive radiation

1. Describe factors that are known to contribute to extinction. Explain the effect that these factors have on species diversity.

2. Explain how anthropogenic (man-made) climate change has affected the process of speciation on planet Earth.

3. Explain how extinction makes new niches available for other species to occupy and its effect on adaptive radiation.  Provide an example of a time that this happened in Earth’s history. 

7.12 Variations in Populations

The level of variation in a population affects population dynamics

• Variation: refers to different combination of alleles (genotypes) and phenotypes found in a population

  • Results from  mutations and crossing over during meiosis

  • Genotypes + environmental factors = individual’s phenotype

  • Genetic diversity influences population’s ability to respond to changes in the environment

  • Pop with little genetic diversity>risk of extinction

California condors have little genetic diversity

• 1987: became extinct in wild

  • Threatened by habitat loss, peaching, lead poisoning

• Last 27 in wild captured, bred, reintroduced into wild

• Entire pop of condors are descendants of 14 birds bred in captivity>little genetic diversity

• Existing population is less resilient to environmental change, maintained through captive breeding

Genetically diverse populations are more resilient to environmental change

• Diverse pop have individuals with variety of adaptations

  • More likely to contain individuals who can withstand new environmental pressures

  • Environmental pressures include: climate change, catastrophic geological events, habitat loss, human interference, change in food source, predation

Not all individuals in a diverse population are susceptible to a disease outbreak

• Antibiotic resistance= population resilience

• Some individuals can withstand exposure to antibiotics = antibiotic resistance

  • Pass resistance to offspring + other bacteria in the pop

Alleles that are adaptive in one environmental condition may be deleterious in another

• Deleterious traits: those that reduce the chance of survival

• Adaptive traits: those that increase the chance of survival

  • Selective pressures of the environment determine whether the trait is an advantage or disadvantage

1. Explain how the diversity of a population affects its ability to withstand environmental pressures.

2. Describe the effect that a lack of genetic variation has on the population of California Condors. 

3. Describe how antibiotic resistance arises within a population.

4. Compare and contrast deleterious and adaptive traits and give an example of each. Describe how each one of these affects the fitness of an organism.

7.13 Origins of Life on Earth

What scientific evidence provides support for models of the origin of life on Earth?

• Geological evidence: Earth formed approximately 4.6 billion years ago; environment too hostile for life until 3.9 bya

  • Earliest fossil evidence for life dates to 3.5 bya

What are the models for the origin of life on Earth?

• Primitive Earth provided inorganic precursors that organic molecules could have been synthesized

• Presence of free energy and absence of significant quantity of atmospheric oxygen

• Organic molecules transported to Earth by a meteorite or celestial event

What is the RNA World Hypothesis?

• Monomers served as building blocks for formation of complex molecules (amino acid/nucleotides)

• Joining of monomers= polymers that could replicate, store, transfer information

• RNA World Hypothesis: proposed RNA could have been the earliest genetic molecule

1. Illustrate a scene from early Earth that explains the conditions that existed on our planet 4.6 billion years ago.  Explain why this environment was not favorable for the survival of living things.    

   1. The environment 4.6 billion years ago on Earth was hostile, consisting of gases and solids with no atmosphere and a molten surface. This environment was not favorable for the survival of living organisms as the atmosphere lacked oxygen and an ozone layer which is essential for life to sustain.

2. Discuss reasons why early Earth’s atmosphere did not favor multicellularity.

   1. Earth’s atmosphere did not favor multicellularity because according to the RNA world hypothesis, an RNA molecule was first created, and was unstable until the formation of DNA, which was more stable and was able to withstand multicellular life.

3. The primitive Earth had conditions that were optimal for the formation of organic molecules.  Describe these conditions and the process by which organic molecules could have formed.  

   1. According to the primordial soup ideology, the collection of complex molecules produced by natural chemical reactions in which further reactions could take place to produce cells such as the speculation of life beginning when carbon-based molecules were energized by lightning to create organic molecules and cells. 

4. Scientists claim that inorganic molecules could have formed organic molecules outside of a living cell.  Describe the role of dehydration synthesis in this process. 

   1. Dehydration synthesis is the process of creating a larger molecule from smaller molecules with the release of water. Chemical reaction convert organic molecules came together in Earth’s atmosphere which may have been through dehydration synthesis, allowing water to continue cycling. For example, in the Miller-Urey experiment simulating the ancient water cycle, complex molecules such as amino acids were produced.

Type of selection: 

• Directional selection

  • at first it was going to larger beaks from drought

  • During el nino, smaller beaks were more successful

Causes:

• Topography

  • Low islands have cactus shrubs

  • Needle like beak perfect for insects

  • Woodpecker, with robust beak for beetle larvae

  • Cactus finch with long sharp for cactus flowers

  • Large,, medium, small ground finches

• Drought (vegetation disappears except for cactus and bare trees)

  • Medium ground finches had to compete for food (originally small seeds but started to eat spiny, sharp, large seeds)

    • Originally died

    • Beaks became bigger

• El nino brough x10 more rain, more vines and vegetation

  • When drought struck, large seeds were scare 

  • Big beaks couldn't survive and small beaks survived to eat small seeds from vines

• Different noises/songs and appearance which keeps them from not mating (differentiates species)