Edit · Oak Gall Wasp Biology, Life Cycle, and Ecological Interactions

What causes oak apple galls on valley oaks?

The California gall wasp (Andricus quercuscalifornicus) lays eggs on oak twigs, and the larvae induce abnormal tissue growth, forming galls.

Describe the life cycle of the California gall wasp.

Eggs are laid on oak twigs in fall → overwinter → hatch in spring → larvae develop inside galls → bore out as adults in late summer/fall.

Define inquiline; in the context of oak galls.

An organism (e.g., moth or beetle) that uses the gall for shelter or food without harming the gall wasp larvae.

Define parasitoid; in the context of oak galls.

An organism (e.g., parasitic wasp) that lays eggs inside gall wasp larvae, killing them. "Wasp Galls On Trees"

Define predator; in the context of oak galls.

A larger organism (e.g., bird or mammal) that preys on gall inhabitants, including gall wasps.

How do observations differ from inferences in Lab 1?

Observations are direct descriptions (e.g., "The gall has a hole"), while inferences are interpretations (e.g., "The hole was made by a predator").

What is a testable hypothesis?

A hypothesis that can be supported or rejected through experimentation or observation (e.g., "Larger galls have higher survival rates of gall wasp larvae").

What is a falsifiable hypothesis?

A hypothesis that can be proven wrong through evidence (e.g., "All galls contain gall wasp larvae" is falsifiable if a gall without larvae is found).

What is the purpose of a t-test in Lab 1?

To compare the mean gall sizes between groups (e.g., galls with gall wasps vs. predators) and determine if the differences are statistically significant.

 What does a critical value in a t-test tell you?

The threshold that the calculated t-value must exceed to reject the null hypothesis (i.e., to conclude that the difference is significant).

If your t-test result is not significant, what might explain this?

Small sample size, high variability in gall sizes, or no real difference between the groups. Check data collection and assumptions.

What pattern might you expect in a histogram of gall sizes?

1. A distribution showing the frequency of different gall sizes, which may reveal if galls cluster around a specific size.

How do you use a dichotomous key in Lab 1?

Follow a series of yes/no questions to identify the organisms inside a gall (e.g., "Does the organism have wings? → Go to step 2").

* Dichotomous keys are used to systematically identify organisms or objects by narrowing down characteristics through paired choices until the correct identification is reached.

What is microevolution?

Changes in allele frequencies in a population over generations.

What are the three main processes of microevolution explored in Lab 2?

Mutations, genetic drift, and gene flow.

What is a mutation?

A permanent change in a DNA sequence, often from replication errors.

How do mutations affect biological fitness?

Most are neutral, some are detrimental, and some are beneficial depending on the trait and environment.

What is the relationship between genome length and mutation rate?

1. Organisms with longer genomes generally have lower mutation rates per base to avoid harmful mutations.

Why do scientists generate new flu vaccines each year?

The influenza virus has a high mutation rate, causing rapid genetic changes that require updated vaccines.

What is genetic drift?

Random changes in allele frequencies over time due to chance, especially in small populations.

What happens to alleles in small populations due to genetic drift?

Alleles may be lost (frequency = 0) or fixed (frequency = 1) more quickly.

How does population size affect the time to fixation or loss of alleles?

Smaller populations fix or lose alleles faster than larger populations.

How does initial allele frequency influence genetic drift outcomes?

Alleles with higher initial frequency are more likely to become fixed; lower frequency alleles are more likely to be lost.

What is gene flow?

The movement of alleles between populations through migration or gamete transfer.

How does gene flow affect populations?

Increases genetic variation and changes allele/genotype frequencies.

What is the Hardy-Weinberg model?

1.  A mathematical model predicting allele and genotype frequencies remain constant if no evolution occurs.

List the five conditions for Hardy-Weinberg equilibrium.

1. No mutation
2. No (natural) selection
3. No gene flow
4. Large population size
5. Random mating

 What evolutionary mechanisms cause populations to deviate from Hardy-Weinberg equilibrium?

Mutation
Natural selection 
Genetic drift
Gene flow
Non-random mating.

How does migration rate influence gene flow in the Koi simulation?

Higher migration rates lead to faster changes in allele and genotype frequencies.

What factors limit gene flow?

Organism traits,
Environmental barriers,
Distance
Reproductive isolation.

Why are mutations important in evolution despite small changes in allele frequencies?

They provide the genetic variation that natural selection and other processes act upon.

How do allele and genotype proportions change over time with low vs. high migration rates?

Low migration slows allele frequency changes; high migration accelerates them.

What is natural selection?

Differential survival and reproduction of individuals with advantageous traits.

What conditions are necessary for natural selection?

1. Variation in traits
2. Differential survival/reproduction
3. Heritability of traits.

What is fitness in the context of natural selection?

The ability of an organism to survive and reproduce in a given environment.

How does phenotype relate to fitness?

1. Phenotype (physical traits) is influenced by genotype and determines fitness (e.g., a "beak" type that allows efficient prey capture).

What is the purpose of the chi-square test in Lab 3?

To determine if observed data (e.g., prey caught by color) differ significantly from expected data, assessing whether natural selection is acting non-randomly.

What is the null hypothesis (H₀) in a chi-square test?

Differences between observed and expected data are due to chance.

What is the alternative hypothesis (H₁) in a chi-square test?

1. Differences between observed and expected data are significant (non-random).

How do you perform a chi-square test?

Calculate the chi-square statistic using the formula:

where O = observed frequency and E = expected frequency. Compare the result to the critical value for your degrees of freedom.

At what biological level does evolution occur?

Evolution occurs at the population level, not the individual level.

How do you set up the natural selection simulation in Lab 3?

Form groups of 3, use tools as "bird beaks" (e.g., chopsticks), bowls as "bird stomachs," colored paper dots as "prey," and a fabric board as the habitat. Distribute 100 prey randomly.

How could you adapt the natural selection simulation to demonstrate mutation?

Introduce a new "prey" color or trait randomly in one generation and observe its frequency over time.

How could you adapt the natural selection simulation to demonstrate genetic drift?

Use a small population size (e.g., 20 prey) and randomly remove individuals without regard to their traits.

How could you adapt the natural selection simulation to demonstrate gene flow?

Introduce prey from another "population" (e.g., a different habitat) and observe changes in allele frequencies.

Were the results of the natural selection simulation random or non-random? How can you tell?

If the chi-square test shows a significant difference from expected, the results are non-random (natural selection is acting). If not, the results are random.

If predators with clothespins catch mostly red prey in Habitat #1, what does this suggest about the environment?

The red prey may be more visible or easier to catch in Habitat #1, indicating the environment favors predators that target red prey.

How do you calculate percent survivors; in the natural selection simulation?

(Number of survivors / Initial number of prey) × 100.

What is the critical value;in a chi-square test?

The threshold that the calculated chi-square statistic must exceed to reject the null hypothesis (i.e., to conclude that the difference is significant).

Assumptions of HWE

Large population… No genetic drift

Mating is random…. No sexual selection

Lack of mutation… No new variation

Lack of migration… No gene flow

Lack of selection… No natural selection

HWE ASSUMES NO EVOLUTION