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.
