Biology Labs 1-3

California gall wasp

Andricus quercuscalifornicus; insect that induces oak apple gall formation on valley oak trees.

Valley oak

Quercus lobata; host tree species where oak apple galls develop.

Inquiline

An organism that uses the gall for shelter or food without directly killing the gall wasp larva.

Parasitoid

An organism (e.g., Torymus californicus) that lays eggs inside the gall chamber, parasitizing and killing the gall wasp larva.

Large, irregular hole in gall

Indicates predation by a larger animal (e.g., bird or small mammal).

Small, circular hole in gall

Indicates exit of an adult wasp or unknown insect that successfully emerged.

Remains of two individuals in larval chamber

Indicates parasitism by a parasitoid wasp.

Observation vs. Inference

An observation is direct measurement or recording of data; an inference is a logical explanation or interpretation of that observation.

Hypothesis

A tentative, testable, and falsifiable explanation for an observed phenomenon.

Null Hypothesis (H₀)

A statistical hypothesis asserting that there is no significant difference, effect, or relationship between observed data and expected theoretical ratios.

Alternative Hypothesis (HA)

A statistical hypothesis asserting that an experimental treatment or variable produces a real, significant effect.

Purpose of a two-tailed t-test

To compare the means of two distinct groups and determine if differences are statistically significant.

Two-Tailed T-Test vs. Chi-Square Test

A t-test compares continuous numeric means between two groups, whereas a Chi-Square test compares categorical observed counts to expected counts.

Five processes of microevolution

Natural selection, mutation, genetic drift, gene flow (migration), and non-random mating.

Genetic drift

Random changes in allele frequencies over generations due to chance events.

Impact of small population size on genetic drift

Small populations experience stronger genetic drift, leading to faster allele fixation (p=1) or loss (p=0).

Bottleneck Effect

A type of genetic drift resulting from a sudden, severe reduction in population size due to an environmental event or disaster.

Founder Effect

A type of genetic drift occurring when a small subset of individuals colonizes a new area, establishing a population with reduced genetic variation.

Allele Fixation

The state when an allele reaches a frequency of 1.0 (100%) in a population, resulting in the total loss of alternative alleles.

Allele Loss

The total elimination of an allele from a population's gene pool, leaving its frequency at 0.0.

Gene flow

The transfer of alleles into or out of a population due to movement of fertile individuals or gametes.

Conditions for Hardy-Weinberg Equilibrium

No mutations, random mating, no natural selection, extremely large population size, and no gene flow (migration).

Hardy-Weinberg Assumption: Infinite Population Size

Eliminates random sampling errors and prevents genetic drift from altering allele frequencies over generations.

Hardy-Weinberg Assumption: Random Mating

Ensures every individual has an equal chance of mating with any other individual, preventing mate choice from altering genotype frequencies.

Hardy-Weinberg allele frequency formula

p + q = 1, where p is the frequency of the dominant allele and q is the frequency of the recessive allele.

Hardy-Weinberg genotype frequency formula

p^2 + 2pq + q^2 = 1, where p^2 is homozygous dominant, 2pq is heterozygous, and q^2 is homozygous recessive.

Three conditions necessary for natural selection

Phenotypic variation in a trait, heritability of the trait, and differential fitness/survival based on the trait.

Directional Selection

A mode of natural selection that favors individuals at one phenotypic extreme, shifting the population's trait distribution in that direction.

Stabilizing Selection

A mode of natural selection that favors intermediate phenotypes while selecting against extreme phenotypes, reducing trait variation.

Disruptive Selection

A mode of natural selection that favors individuals at both phenotypic extremes over individuals with intermediate traits.

Adaptation vs. Acclimation

Adaptation is an evolutionary, inherited trait across generations; acclimation is a short-term, temporary physiological change in a single individual.

Biological level at which evolution occurs

Populations evolve over generations; individual organisms do not evolve in their lifetime.

Non-random nature of natural selection

Survival and reproduction depend non-randomly on inherited traits matching environmental demands.

Primary source of new genetic variation

Mutations, which introduce novel alleles into a population.

Purpose of a Chi-Square goodness-of-fit test

To determine whether observed experimental outcomes differ significantly from expected theoretical frequencies.

Chi-Square Formula

where O is the observed count and E is the expected count for each category.

Formula for degrees of freedom in Chi-Square test

df = c - 1, where c is the number of categories.

Standard Alpha Level (\alpha)

The significance threshold (typically \alpha = 0.05) used to determine whether to accept or reject the null hypothesis.

Interpretation when calculated Chi-Square > Critical Value

Reject the null hypothesis (H₀); differences between observed and expected results are statistically significant.

Interpretation when calculated Chi-Square < Critical Value

Accept the null hypothesis (H₀); differences between observed and expected results are due to chance alone.

Oak Gall Hypertrophy

Abnormal, rapid enlargement of plant tissue induced by insect larvae to form protective gall walls.

Mendelian 3:1 Phenotypic Expectation in Chi-Square

In a monohybrid cross (Aa x Aa), expected counts are 75% dominant phenotype and 25% recessive phenotype.

Oak Apple Gall Community Species

1. Valley Oak (host tree)

2. California Gall Wasp (gall maker/herbivore)

3. Parasitoid Wasp (e.g., Torymus californicus, kills wasp larva)

4. Inquiline Wasp/Beetle (uses gall for shelter/food) 5. Bird/Rodent (predator that tears gall open).

Observation vs. Inference

An observation is direct information gathered using the senses or tools (e.g., "The gall has a 2mm circular hole").

An inference is a logical interpretation or conclusion based on observations and prior knowledge (e.g., "An adult wasp emerged from this gall").

What Makes a Hypothesis Scientific?

A scientific hypothesis must be both testable (able to be evaluated through experiments or observations) and falsifiable (able to be proven wrong by evidence).

Hypothesis vs. Prediction

A hypothesis is a proposed, testable explanation for a biological phenomenon ("Parasitoid wasps target smaller galls because they are easier to penetrate").

A prediction is a specific, measurable outcome expected if the hypothesis is true ("If gall size decreases, the rate of parasitoid emergence will increase").

5 Processes of Microevolution

1. Natural Selection (differential survival/reproduction)

2. Genetic Drift (random chance events in allele frequencies)

3. Gene Flow (migration of individuals/alleles between populations)

4. Mutation (creation of new alleles)

5. Non-Random Mating (sexual selection or inbreeding).

Importance of Mutation in Evolution

Mutation is the ultimate source of all novel genetic variation. Even though single mutation rates are low, without mutation there would be no new alleles for natural selection, genetic drift, or gene flow to act upon.

Population Size vs. Fixation/Loss Time

Smaller populations (N) experience stronger genetic drift, causing alleles to reach fixation (p=1.0) or loss (p=0.0) much faster. Larger populations resist drift, taking many more generations for alleles to fix or be lost.

Initial Allele Frequency vs. Fixation/Loss Time

Higher initial frequencies (p) make an allele far more likely and faster to reach fixation (p=1.0), while lower initial frequencies make an allele more likely to be lost (p=0.0) early on by chance.

Low (0.2) vs. Normal (0.7) Migration Rates

Both rates cause allele/genotype frequencies between populations to homogenize (become similar) over time. However, the higher rate (0.7) achieves equilibrium and genetic uniformity much faster than the lower rate (0.2).

Why Real Populations Rarely Meet HWE

HWE requires 5 strict conditions (no drift/infinite size, no gene flow, no mutation, random mating, no selection). Real environments constantly experience finite population sizes, migration, mutations, mate choice, and selective pressures.

Conditions of Natural Selection Met in Lab

1. Variation: Multiple prey colors (paper dots) and predator beak types existed. 

2. Heritability: Surviving prey colors reproduced based on survival proportions.

3. Differential Fitness: Camouflaged prey survived predator attacks better than non-camouflaged prey.

Random vs. Non-Random Results

Results were non-random. Predators actively selected easier-to-see prey colors first, leading to directional changes in prey color frequencies based on camouflage effectiveness rather than pure chance.

Biological Level of Evolution

The population level changed over time. Individual prey items (paper dots) never changed color; rather, the overall color frequencies of the prey population shifted across generations.

Simulating Mutation in Lab Setup

Introduce a brand new paper dot color (e.g., neon yellow) in generation 2 or 3 that was not present in the original starting population to represent a novel genetic allele.

Simulating Genetic Drift in Lab Setup

Remove a large batch of prey paper dots at random without looking (a natural disaster bottleneck) or transfer a small random sample of dots to a new habitat board (a founder effect).

Simulating Gene Flow in Lab Setup

Move a fixed number of paper dots between two different habitat boards (representing migration between two distinct prey populations) during the reproduction phase.