Biology 1114 first quiz
Mutation definition
A permanent change in an organism's DNA sequence that may or may not result in phenotypic change • Occur randomly • Ultimate source of all genetic variation
What is a Prediction
A statement of what will happen if your hypothesis is correct given a specific set of experimental circumstances • Outlines how to test hypothesis by specifying the dependent and independent variables
Gene
A unit of DNA that codes for a protein; unit of heredity
Genotype
An individual's set of genes; the pair of alleles an organism has for a gene
circular logic
Assuming your claim is already proven and then using your "proven" claim to support itself.
Heritability of tannin concentration phenotype: h 2 = 0.5 in population 1, h2 = 0.2 in population 2 After many generations of identical herbivory selective pressures, which of the following do you predict will occur? A. Both populations of oaks will show identical increases in average acorn tannin concentrations B. Both populations of oaks will show increases in average acorn tannin concentrations, but the increase will be greater in population 1 than in population 2 C. Both populations of oaks will show increases in average acorn tannin concentrations, but the increase will be greater in population 2 than in population 1. D. We need to know Ve values before an accurate prediction can be made.
B
In the Alzheimer's in class activity, one of the hypothesis options was 'Beta-amyloid is associated with memory loss because the proteins are found in patients with Alzheimer's.' What was incorrect about this hypothesis? Select all that apply. A. It includes the independent variable B. It uses circular logic. C. It lacks a mechanistic explanation. D. It includes the study organism used in the experiment.
B and C
Survival
Differential survival among phenotypes
More on evolution
Evolution is not always predictable! • Evolution does not always results in better adapted populations! • Evolution can happen via multiple mechanisms
Given the information provided, write a hypothesis for the research question: Are melatonin levels associated with colic cramps?
H: Colic cramps are associated with low melatonin levels because this hormone inhibits serotonin activity which causes intestinal cramping.
Response to the environment
Individuals with phenotypes better suited to the environment survive and reproduce
Ve
Phenotypic Variation due to Environmental Variation at Population Level
Variation
Pre-existing variation needed for population response to environmental change
Reproduction
Survivors reproduce while non-survivors don't (differential reproduction), pass on alleles to next generation
We determined that Ve was lowest in population 4. Select the answer that correctly describes why this was the correct choice.
The individuals in this population are not experiencing any environmental variation and thus no phenotypic variation is explained by environmental effects.
sample size
The number of subjects used in an experiment or study. Generally, the larger the better.
Phenotype
The set of observable physical characteristic of an organism; product of genes and the environment
Frequency
Think percent; how common an allele is in a population relative to the other alleles for that gene
Vp
Total phenotypic variation due to both genetic variation and environmental variation Phenotypic variation of a population
pseudoreplication
experiment appears replicated but is NOT because the samples are not truly independent of each other
gene flow
movement of alleles from one population to another
heritability
the proportion of phenotypic variation in a population attributable to genotypic variation (h^2)
Mutation
the ultimate source of all genetic variation • By default, introducing a new allele changes allele frequencies
What is a scientific hypothesis?
thesis: tentative mechanistic explanation of an observation that is testable and falsifiable • Explanation must answer the question why? • always include a "because statement"
Pseudoreplication occurs...
when samples are not independent yet used as replicates
Assume h^2 = 0.8 for human height in our class. Which of the following is accurate given this heritability? A. 80% of your height (as an individual) is determined by your genetics, 20% is due to your environment B. 80% of the variation in height in this class is explained by genetic variation C. Both A and B are correct interpretations.
80% of the variation in height in this class is explained by genetic variation
A conclusion A. is formed from the evidence of a single study B. is extremely highly supported by evidence C. Is something science has proven to be true
A
A group of lady bugs has variation for spot number phenotype and this variation is genetically controlled. There is no relationship between spot number and any environmental pressure in the lady bug's environment. Roughly thirty percent of the population migrates away to a different location and allele frequencies substantially change in the population as a result of the migration. If the allele frequency changes are maintained in the next generation, select the answer that correctly describes this scenario A. The population has evolved by gene flow. B. This population has evolved by genetic drift. C. This population has evolved by natural selection. D. This population has evolved by mutation
A
In the Alzheimer's in class activity, one of the prediction options was 'If my hypothesis is correct, then mice injected with beta-amyloid will forget chores they have previously been taught because the proteins degenerate brain cells associated with memory.' What was incorrect about this prediction? A. It includes an explanatory statement B. It doesn't include the dependent variable C. It doesn't include the independent variable D. It needs to be more generalized so it can be applied to multiple experiments
A
In the Alzheimer's in class activity, one of the hypothesis options was 'Beta-amyloid will cause mice to forget previously learned chores because the proteins degenerate brain cells associated with memory.' What was incorrect about this hypothesis? Select all that apply. A. It includes the study organism B. It includes the dependent variable C. It includes the independent variable D. It uses circular logic.
A and B
Select all of the answers that correctly describe genetic drift. A. A random evolutionary mechanism B. Results in adaptation C. May or may not result in changing allele frequencies from generation to generation D. Does not result in better adapted populations
A and D
Evolution
A change in allele frequencies in a population from generation to generation
Definition of Evolution: What mechanisms can evolution occur by?
A change in allele frequencies in a population from generation to generation Can occur via 4 mechanisms: Natural selection, mutation, gene flow, genetic drift
Evolution is described as a scientific theory. Given our discussions of how to talk about science and the definition of a theory, select all the correct statements below. A. There is extremely high experimental support for evolution. B. Evolution unifies many hypotheses. C. Scientists have proven that evolution is correct. D. Scientists have extremely high confidence that the theory of evolution is correct
A,B and D
We determined population 2 had the lowest Vg. Select the answer that correctly describes why this was the correct choice.
All of the individuals in population 2 were genotypically identical and thus no phenotypic variation could be explained by genotypic variation.
Allele
Alternate forms of the same gene; different alleles may code for different phenotypes
A group of scientists wants to determine if fin length variation is genetically or environmentally controlled. They think the presence of predator pressure may be an environmental determinant of fin length. The scientists take eggs from short-tailed parents and raise them in both low and high predator pressure environments. They also take eggs from long-tailed parents raise them in both low and high predator pressure environments. The scientists then evaluate the tail length of the fish hatched from the eggs at adulthood. Select the correct dependent variable for this experiment. A. Level of predation pressure. B. Tail length at adulthood. C. Tail length of the parents of the eggs. D. The eggs.
B
In our evolution case study, the bird population initially had three beak size phenotypes--small, medium, and large. Following the drought, you correctly predicted that the next generation would have exclusively large and medium beaked birds as the smallest food source had died out. Which of the following accurately describes why there were no small beaked birds in the next generation? A. The birds with small beaks mutated to have large or medium beaks because that is the more beneficial phenotype for their environment. B. The small beaked birds died and thus didn't contribute alleles for small beaks to the next generation. C. The small beaked birds migrated to an area with better food availability. D. The small beaked birds died randomly.
B
Since this question requires you to identify the best hypothesis from a series of choices, you must consider the elements of a well constructed hypothesis and what information should NOT be included. Select all of the correct answers to complete the phrase. A scientific hypothesis SHOULD A. contain the independent and dependent variables. B. state the basic relationship of interest. C. include a mechanistic explanation D. provide details about experimental design E. reiterate the relationship of interest as the explanatory statement.
B and C
We determined that all four population had Vp > 0. We also know that population 2 has Vg = 0 and population 4 has Ve = 0. Select the answers that correctly describe the relationship between Vp, Ve, and Vg. A. Vp can be greater than 0 even if both Ve and Vg in a population are 0. B. Vp describes total phenotypic variation in a population irrespective of whether that variation has environmental or genetic causes. C. As long as Ve OR Vg are greater than 0, Vp will also be greater than 0.
B and C
How do genes affect phenotypes? Select the best answer A. Genes code for proteins and are the only influence on an organism's phenotype. B. Genes code for proteins and are one factor that affects an organism's phenotype C. An organism's genetic are not associated with its phenotype
B.
All individuals in a population have the exact same allele that codes for a given phenotypic characteristic (aka that is the only allele present in the population). Ve = 0 for this trait in this population. Given this information, what does h^2 equal in this population? • A. 1 • B. 0 • C. Something in between 1 and 0
B. Zero NO genetic variation in the population → thus, no phenotypic variation can be explained by genotypic variation because there is none • (also in this scenario, because Ve and Vg both = 0, Vp is also 0)
Cross-fostering experiment: the common garden of animals
Break up litters at birth, randomly redistribute young among family groups • Assess hunting prowess phenotype of cross fostered pups at adulthood • Distinguish environmental vs. genetic effects? • If genetic effect: Pack A pups always have high hunting prowess no matter the pack that raises them, vice versa for pack B pups • If environmental: Pack A pups have low hunting prowess when raised in Pack B, vice versa for pack B pups
Carefully determine if each answer accurately describes the action of each evolutionary mechanism. Having red fur is extremely advantageous relative to all other fur color phenotypes in a population of sloths. Predictably, red is the most common fur color phenotype in the population and this characteristic is heritable. Which of the following is the most likely explanation for the high frequency of red fur color relative to all other color phenotypes? A. Many individuals transitioned from other colors to red-furred as this was advantageous for their survival and reproduction. B. Many individuals in the population likely experienced the mutation that resulted in red fur coloration as it was highly advantageous in the sloths' environment. C. Neither option is correct.
C
Evaluate the definition of evolution. Select the correct statement based on this definition. A. An individual organism can evolve B. If allele frequencies stay the same over time, the population still may have evolved. C. Individuals cannot evolve. Populations evolve
C.
In the Alzheimer's in class activity, one of the prediction options was 'If my hypothesis is correct, then mice injected with beta-amyloid will experience memory loss.' What was incorrect about this prediction? A. It included the study organism used in the experiment B. It didn't include the independent variable C. I didn't include the dependent variable D. It didn't have an explanatory statement
C.
Inherited
Characteristic passed from parent to offspring via genes
Spider questions: Phenotypic Variation due to Genotypic Variation at Population Level example
Color controlled by 1 gene with 3 alleles Additive effects of pigment production
What does h^2 = 1 indicate?
Complete heritability → all phenotypic variation is due to genotypic variation • Heritability is typically high when phenotypic variation due to environmental variation is low
'The character "feather color" has a heritability of 0 in a population of crows. Given this information, which of the following may be true?' A.Another population of crows may have a heritability of greater than 0 for feather color. B. All individuals of this population may have identical alleles for feather color. C. The phenotypic variation for feather color in the population with a heritability of 0 would be less than in a population with a heritability of more than 0. D. Two of the above are correct. E. All of the above are correct.
D
A population of alpacas all have an identical fur length phenotype. During a particularly cold winter, longer fur would be beneficial as it would provide them with greater insulation. Select the correct answer given this information. A. The alpacas will evolve by natural selection as longer hair would be favorable in their environment. B. A mutation for longer fur will likely develop in this population. C. Alpacas with longer fur will likely migrate into this population as they have a beneficial phenotype for the cold winter environment. D. The alpacas will not evolve by natural selection for fur length phenotype.
D
Which of the following accurately describes natural selection? A. Natural selection acts on pre-existing variation in a population. B. Natural selection occurs when individuals shift to a different phenotype better suited to their novel environment. C. Populations become better adapted to novel environments as individuals with beneficial phenotypes reproduce more than others without that phenotype. D. Two of the above are correct. E. All of the above are correct.
D
In a population of fish, there is substantial variation in fin length phenotype. If a fish is raised in an environment with high predator pressure, that fish will develop a smaller tail at adulthood as long tails make them easier to catch. If a fish is raised in an environment with low predator pressure, that fish will develop a longer tail as greater length increases swimming speed and the threat of predators is low. Further, eggs from short tailed parents when raised with low predator pressure develop long tails. Eggs from long tailed parents when raised with high predator pressure develop short tails. The tail length differences observed in this scenario are a product of evolutionary change by natural selection.
False
Multiple studies have shown that annual plants tend to advance their flowering time more with warming temperatures than perennial plants. Since several studies have found this link between annual plants and greater flowering advancement with temperature, we can form the Theory of Annual Flowering Advancement as this fits the key components of a scientific theory.
False
Vg
Genetic variance different phenotypes in a population due to different genotypes
In the questions above, you selected that the hypothesis should or should not include the independent and dependent variables. For either response, this means you'll need to identify the variables to ensure that they are either present or absent as per your answer to the question above. Select the correct independent variable (IV) and dependent variable (DV) from Dr. Reddy's experiment
IV = hypocretin injection, DV = frequency of sleep attacks
The question prompt provided above specifies the heritability for feather color is 0. Considering the definition of heritability you selected from your previous answer, select the answers that correctly describe a heritability of 0 for a given phenotypic characteristic. Refer to specific examples we discussed in class to help you eliminate incorrect answers. A. Ve must by very high for heritability to be 0. B. If heritability for a characteristic is 0, Vp is also 0. C. If heritability for a characteristic is 0, Vg must be 0. D. All of the above are correct.
If heritability for a characteristic is 0, Vg must be 0.
For the wolf pack experiment: What are the independent and dependent variables?
Independent: • pack of origin (genes) AND pack the pups are raised in (environment) Dependent: • Number of successful kills/attempt
What's wrong with this hypothesis and why do we care? • H: Mice given supplemental melatonin in their food will experience a lower number of intestinal cramps/10 minutes because this hormone inhibits serotonin activity which causes intestinal cramping
Limits ability to test hypothesis to a single experiment → how does this affect our confidence in our findings based on repeated testing?
Waterfowl: genetic control of predisposition for migration phenotype BUT migratory route is learned (environmental control of phenotype) • Family groups migrate together for 1-2 seasons Is this migratory behavior as a phenotype determined by genes, the environment or both?
Migratory behavior phenotype both genetic AND environmentally determined
Song birds: Fledglings complete autumn migration independent of their parents. Migratory behavior as a phenotype—is phenotype determined by genes, the environment, or both?
Migratory phenotype = genetically controlled • Both predisposition for migration AND time-and direction compass genetically controlled
You observe a population of birds that are genetically identical, sharing the same allele for height. Height differences are the result only of environmental effects. Taller stature would be beneficial for feeding on taller plants. Can this population evolve by natural selection?
NO
Apply your answers from the previous questions to analyze each answer option for the original question prompt provided below. Carefully determine if each answer fits what information should be included or excluded from a properly formed hypothesis given your prior answers. Dr. Reddy is investigating the neurological basis for narcolepsy. Narcolepsy is a disorder of the brain in which people experience uncontrollable bouts of sleep sometimes called "sleep attacks." Dr. Reddy is specifically interested in a neurotransmitter called hypocretin which promotes wakefulness and has been implicated in other sleep disorders. To test the effects of hypocretin on the frequency of narcoleptic sleep attacks, she separates 40 mice with narcolepsy into two groups. The first group includes 20 mice with low levels of hypocretin in their brains and these mice receive no injection. The second group includes 20 mice who also have low levels of hypocretin, but receive an injection to increase their brain hypocretin levels to established normal values. Dr. Reddy determines the frequency of sleep attacks during the 24 hour period for each mouse. Select the best hypothesis given the information provided.
Narcolepsy is associated with low levels of hypocretin because this hormone promotes wakefulness and therefore low levels of hypocretin would be inadequate to maintain wakefulness
Which group of birds is most likely to immigrate to the island with predator pressure?
No differences between the groups for probability of migration! Why? • Gene flow is random with respect to environmental pressures in the new environment
If beak size is determined by which foods nestlings eat most frequently during their early development and is NOT an inherited trait, would the population evolve in response to drought? A. Yes B. No
No! • Evolution can only happen for traits determined by genes (alleles) • Remember: "change in allele frequency" - evolution
gene expression based on
Non-genetic factors affect gene expression • Phenotype is the product of BOTH genes and the environment • Genotype expressed in the environment of the organism • Two genetically identical hydrangeas planted in different areas • What factors may affect flower color phenotype? • Pink = basic soil, blue = acidic soil with more free Al
Vp = Vg + Ve
Phenotypic variation = Genotypic variation + Environmental variation
common garden experiment
Plants of known genetics grown in controlled environmental conditions to assess effects of genes vs. environment on phenotype
inherited characteristics
Populations can only evolve regarding traits that are inherited (passed from parents to offspring)
GIven: Colic: 3 hours of crying 3 or more days a week, usually worst before nightfall • Severe intestinal cramping • Baby neurological development: • Serotonin → hormone produced by intestines during evening; stimulates smooth muscle contraction • Melatonin→ hormone produced in brain that inhibits serotonin • Colic babies: symptoms usually dissipate at roughly the same developmental stage when brains produce melatonin more efficiently What is a good observational question?
Question: Are melatonin levels associated with colic cramps?
genetic drift
Random events change allele frequency from generation to generation
Why replication is important
Replicates ensure that your results aren't caused by odd-ball events • Represent a population mean response
Conclusion
Results from a single experiment that tested a single hypothesis • Conclusions may support or refute the hypothesis
Analysis
Scientific conclusions are based on evidence Conclusions: result from 1 study testing 1 hypothesis
• If we're interested in the effect of melatonin on cramping, why did one group of mice receive no melatonin?
Serves as a control group: a group that does NOT receive the treatment but is identical in all other ways to the treatment groups; serves as point of comparison
Population
Set of individuals of a species that live in the same area and interbreed
Evolution: observations and inferences
Survival, reproduction, response to environmental pressure, variation Inferences: Survival and reproduction differ among varied phenotypes in response to an environmental pressure. Individuals with phenotypes better suited to the environment pass their alleles to offspring at a greater rate than individuals with phenotypes poorly suited to their environment. Alleles for adaptive phenotype well suited to the current environment more common in the population in the next generation.
The two packs significantly differ in hunting prowess phenotype. • Pack A has a significantly higher successful hunt rate (# successful kills/hunting attempts) than Pack B. • Hunting: learned behavior (learning environ. = environmental effect on phenotype) BUT also has genetic component • ALL other environmental factors equal between packs • Form a hypothesis for the differences in hunting prowess phenotype between the two packs based on genetic vs. environmental (learned) effects on phenotype.
The difference in hunting prowess phenotypes is due to genetic differences between the two packs. Pack A pups inherit alleles that result in greater hunting prowess that are not present in the other pack. OR The difference in hunting prowess is environmental and thus results from learned behaviors. Pups in Pack A learn greater skill at hunting from their more skilled parents.
prove
The p-word = prove • We NEVER prove things in science • Why? (hint: think of the key components of a scientific hypothesis) • Why is this a good thing?
We determined that Population 2 could not evolve by natural selection. If this population has phenotypic variation, why could it not experience natural selection for this trait? Select all that apply.
The phenotypic variation was due to environmental effects. The individuals in the population were all genotypically identical so the variation was not genetically determined.
Imagine a predator is introduced to the island Birds' non-camo color and large tails make them easy to catch Hypothesis: How will the population likely respond to the introduction of the predator?
The population will likely die out or decline Observation: • Without variation, populations cannot respond to environmental change via evolution Inference: • Evolution is not goal-oriented. • Organisms don't mutate or adapt because they "need" to • Individuals/populations poorly suited to environment may die out
What's wrong with this hypothesis? • H: Colic cramps are associated with low melatonin levels because babies with lower melatonin have more cramping symptoms.
Uses circular logic Circular logic: Explaining that X will happen because X will happen • Doesn't provide a mechanistic explanation for why the event occurs
Natural selection acts ONLY on this portion of phenotypic variation
Vg
h^2=
Vg/Vp or Vg/(Vg+Ve)
Is it possible for a character to vary in a population and have a heritability of 0?
Yes When? • The phenotypic variation for the character results entirely from environmental variation
Can one population of a species have h^2 = 0 for a specific phenotype but in another population have h2 = 0.4 for that same phenotype?
Yes Why? • Different gene pools between populations • Different environmental effects between populations
New individuals arrive to the island—have different alleles than island population • Green color and smaller tails Hypotheses: Will the population evolve as a result of the new arrivals?
Yes, as long as they reproduce Inference: Evolution can occur via migration, or gene flow, as new alleles are introduced to a population
What is the scientific method?
a method of procedure that has characterized natural science since the 17th century, consisting in systematic observation, measurement, and experiment, and the formulation, testing, and modification of hypotheses. • How we learn about the world around us • Systematic, logical approach to study • Science is cyclical—the process keeps going and going continually adding to our knowledge • Key steps: Observation and Question, Hypothesis, Prediction, Testing, Analysis and Conclusions
A scientist is studying the effects of age on matabolic rate. She assigns 40 mice to the old group (older than 1 year) and 40 mice to the young group (younger than 1 year) and evaluated the average metabolic rate between the two groups. In the young group 70% of individuals were male and in the old group 80% of the individuals were female. Sex is an example of a(n)
confounding variable
Confounding variables:
factors that affect the results that were not controlled for • Why is this important? • Try to anticipate these and include in experimental design • Name some possible confounding variables that should be controlled for and enter them in toph
Examples of Non-adaptive (random) evolution?
gene flow, genetic drift mutation
Relate heritability to natural selection
h^2 determines the how strongly a character in a population can respond to natural selection
Evolution by natural selection can act ONLY on..
heritable characteristics • Need to differentiate effects of environmental vs. genetic variation on phenotypic variation
Observation/Question
identify a problem to be solved or ask a specific question to be answered
natural selection
individuals with certain heritable characteristics are more likely to survive/reproduce in their environment because of those characteristics. • Alleles for these characteristics thus become more common in next generation
Phenotype is the product of
inherited genotype and environmental influences
Spider questions: Phenotypic Variation due to Environmental Variation at Population Level
intense color stimulates phenotype
Evaluate the following hypothesis: Increased carbon dioxide concentrations result in global warming because as carbon dioxide levels have increased in the past hundred years average temperatures have also increased. What's wrong with this hypothesis?
it uses circular logic
What is an example of Adaptive (non-random) evolution?
natural selection - Individuals with certain inherited traits survive/reproduce more than other individuals as their traits make them better suited to their environment
Barring introduction of new alleles into the population, can this population (all big beaks and big tails) evolve?
• No! • Observation: • Allele frequencies can't change if 100% of the population has the same allele • Inference: • Evolution works on preexisting variation in a population
Should we say, "I believe in science"?
• Not a great way to phrase scientific thought • Why not? (hint: think about what belief is) • Science is based on evidence • We don't believe in facts—they are still factual no matter how we feel about them
Do random occurences always result in evolution?
• Random occurrences can result in evolution of populations. • These populations are not better suited to their environment.
Experiment: Mice with low melatonin production • melatonin supplements in food for 2 weeks; 3 groups (+0, +5mg, +10mg melatonin/day, 20 mice/group) • Observe # intestinal cramps/10 minutes via ultrasound at end of 2 weeks What are the independent and dependent variables?
• Variables: factors of interest to scientists that can change • Independent variable: • what the scientist changes to understand its effects on the system -the melatonin supplement • Dependent variable: • how the scientist measures the system's response to the independent variable -# of intestinal cramps/10 minutes