labs 4-5, case study, appendices B and C Flashcards
rapid evolution in action
Pink Bollworms:
Major pest of cotton, invasive in the U.S.
Larvae reduce cotton yield by eating flowers and seeds.
Rapid population growth: up to five generations per growing season.
Management Strategies:
Pheromone Traps: Lure and capture pests.
Sterilization: Release irradiated moths.
Chemical Insecticides:
Drawbacks: Toxicity, killing beneficial insects, resistance evolution.
Biotechnological Solution:
Bt Cotton:
Contains a gene from Bacillus thuringiensis that produces an insecticidal toxin.
Effective but can lead to Bt resistance over generations.
lake washington sticklebacks
Evolved rapidly from lightly plated to heavily plated in response to clearer water conditions and increased predation by trout.
Key Takeaway:
Rapid evolution can alter ecological dynamics and influence predator-prey interactions
mechanisms of evolution
Natural Selection:
Variation: Individuals differ in traits.
Heritability: Traits are passed from parents to offspring.
Differential Success: Some traits enhance survival/reproduction.
Other Mechanisms:
Mutation:
Source of new genetic variation.
Example: Cadherin mutations confer Bt toxin resistance in pink bollworms.
Migration:
Gene flow between populations can introduce new traits.
Genetic Drift:
Random changes in allele frequencies, especially in small populations.
Founder Effect: A few individuals establish a new population with different allele frequencies.
trade-offs and constraints
Adaptive Trade-offs:
Higher fitness in one environment often reduces fitness in another.
Example: Camouflage on white sand is ineffective on dark sand.
Constraints:
Evolutionary changes are limited by pre-existing structures and genetic pathways.
managing resistance evolution
Bt Toxin and Resistance:
Cadherin gene mutations create resistance to Bt toxin.
Resistance alleles (e.g., “r”) rise in frequency when Bt cotton is overused.
Strategies to Delay Resistance:
Refuge Strategy:
Plant non-Bt cotton nearby to maintain susceptible alleles in the pest population.
Integrated Pest Management:
Combine multiple pest control strategies to reduce reliance on a single method.
genetics and evolution
Population Genetics:
Combines Mendelian genetics with Darwinian evolution.
Evolutionary changes occur when traits associated with fitness become more common.
Heritable Variation:
Variation among individuals arises due to different alleles for the same genes.
Quantitative Traits:
Traits like height and intelligence are influenced by multiple genes and the environment.
pop dynamics vs pop ecology
Population Dynamics:
Changes in population size and composition over time.
Driven by biotic (e.g., competition, predation) and abiotic (e.g., weather, habitat) factors.
Population Ecology:
The study of factors influencing population changes.
Applications: Managing wildlife populations, controlling pests, and conserving endangered species.
geometric growth- assumptions of model
Discrete reproduction (e.g., annual plants, salmon returning to spawn).
Unlimited resources and negligible predation or competition.
exponential growth- key features of model
Positive feedback: Growth accelerates as population size increases.
Example: Invasive species (e.g., water hyacinth) in resource-abundant habitats.
logistic growth
definition: Accounts for resource limitations, resulting in an S-shaped curve.
Growth slows as population approaches K.
Early growth resembles exponential growth; levels off at K
metapop and source/sink systems
Metapopulations:
A collection of subpopulations connected by dispersal.
Source-Sink Systems:
Sources: Stable populations that supply emigrants.
Sinks: Populations dependent on immigration for survival.
Allee Effect:
Reduced growth rate at low population densities.
Causes: Difficulty finding mates, reduced group protection.
Demographic Stochasticity:
Random events (e.g., birth/death) influencing small populations
Growth Models:
Geometric: Discrete reproduction.
Exponential: Continuous reproduction.
Logistic: Resource-limited growth.
electrophoresis
Purpose:
Identifies enzyme variants based on electrical charge differences caused by amino acid substitutions.
Process:
Enzymes migrate differently in a gel based on their charge.
Can detect mutations resulting in distinct enzyme forms called allozymes.
Enzyme Structures:
Monomeric Enzymes: Produce a single, functional polypeptide chain.
Dimeric Enzymes: Require two polypeptides to become active; heterozygotes can produce three variants.
Polymorphism
Definition:
Proportion of loci with multiple alleles in a population.
Monomorphic Loci:
Most common allele frequency ≥ 0.95.
Heterozygosity (H):
Average proportion of heterozygous individuals per locus.
Hardy-Weinberg Equilibrium
Key Concept:
Allele frequencies remain constant across generations under specific conditions.
Conditions for Genetic Equilibrium:
Large population size (to minimize genetic drift).
No gene flow (immigration/emigration).
No mutations, or mutations are balanced.
Random mating (no selective breeding).
No natural selection.
Eq:
p^2+2pq+q^2=1
p^2= homozy. dominant (A1A1)
q^2= homozy. recessive (A2A2)
2pq= heterozy. (A1A2)
p+q=1 –> allele frequencies
pop genetics
Population:
Group of the same species living in one area, freely interbreeding.
Gene Pool:
All alleles present in a population.
Allele Frequencies:
Proportion of each allele in the gene pool.
genetic drift
Definition:
Random changes in allele frequency due to chance events.
Effects:
Faster allele loss in small populations.
Loss of heterozygosity, leading to a population dominated by homozygotes.
Founder Effect:
A new, isolated population differs genetically from the parent population.
Population Bottleneck:
Drastic population reduction causes loss of genetic diversity.
when do you reject null hypothesis
when the calculated x value is greater than the critical x value
character state
a character passed on from an ancestor to its descendant either unmodified or in a modified form
derived character state
can be found in one taxon (unique derived character)
shared derived character
found in more than one taxon
parsimony
a principle in phylogenetics which forces one to accept the shortest tree(s) that explain(s) all the character states
-more efficient and more correct
polytomy
an unresolved group of 3+ taxa
test of significance
evaluates the probability of rejecting the null hypothesis when it’s actually true
chi-square test
used to test a hypothesis in an experiment in which the data are frequency data, rather than continuous data
evidence for zoonotic transmission (from one animal species to humans)
similarities in genome organization of the 2 viruses
there are plausible rotes of transmission
two species co-occur in the same geographic location
two viruses are closely related (phylogenetic relatedness)
virus is prevalent in the wild host
what was the results of the HIV case study
-they identified the stool they collected as belonging to 1) gorillas, 2) P.t. troglodytes and 3) P.t. vellerosus
-only antibodies of stool from P.t. troglodytes reacted with HIV-1 antigens
-they isolated 16 strains of SIV from P.t.troglydtes stool
results show SIV is prevalent in wild P.t. troglodytes
hunter hypothesis
humans came in contact with Simian Immunodeficiency Virus (SIV) when hunting/butchering primates and became infected with a mutated strain of SIV called HIV
-known as a zoonotic transmission, when a virus is transmitted from an animal host to humans
what is HIV (human immunodeficiency virus)
a virus that causes AIDS
