Module 3

• base pair sequences encode instructions for gene regulation and making proteins and hormones
• base pair sequences are disrupted by errors in transcription
• errors in replication impact chromosome
• mutations are caused by mutagens and inaccurate copying
• mutagens break down DNA, errors in repair result in slight differences
• examples of mutagens: cigarettes, radiation
• mutagens can cause cancer in adults
• mutagens that affect gamete cells can cause mutations in offpsring
• base excision repair: removes single damaged base
• nucleotide excision repair: removes small section of DNA surrounding damage
• why do mutations in viruses have quicker effects?

  viruses replicate rapidly
• how can mutations impact the covid virus?

  mutation in spike protein makes it easier to bind to receptor
• artificial selection: humans choose desirable traits
• neural crest hypothesis: selection for tame behavior (domestication) reduces number of migrating neural crest cells
• neural crest cells encode for different cell functions, migrate to specific areas of embryo during development
• full neural crest migration: different cell types are widely distributed
• limited neural crest migration: fewer cells that don't reach as many areas
• what neural cell types contribute to the traits of domestication?

  lighter coat: melanocytes

  shorter snout: osteoblasts/bone

  floppy ears: chondroblasts/cartilage

  hormone levels/reproduction: adrenal cells
• the farm fox experiment found that selection for tamability results in genetic changes (domestication)
• morphological changes observed in the farm fox experiment:

  • body size/proportion
  • lost pigment
  • curled tails, shorter tails
  • floppy ears
• behavioral changes observed in the farm fox experiment:

  • lose seasonal reproduction pattern
  • open eyes and ears earlier, greater social bonding window
  • corticosteroid surge, fear response delayed
  • decreased adrenal gland activity, increased serotonin
• behavior is controlled by regulatory genes, polygenes control early development
• what systems are targeted in early development?

  neural and endocrine
• in domestication, rates of developmental processes change, delayed neural crest migration
• what was observed from delayed neural crest migration in farm fox experiment?

  • skin (pigment)
  • shorter snouts
  • decreased sexual dimorphism
  • earlier sexual maturity and larger litter size
• approaches before ethology: vitalists, reflexologists, behaviorists
• vitalists: behaviors are instincts of mystical qualities
• reflexologists: behaviors are purely mechanical
• behaviorists: learning causes all behaviors
• comparative study of behavior: behavior patterns are explained by natural selection
• reflex arc:

  1. sensory input (stimuli) felt by sensory neurons
  2. travel to spinal cord
  3. signals motor neuron, motor ouput
• in reflex-arc, initial signal stops at spinal cord, allow faster response time
• most reflexes are passed down genetically, not learned
• innate behaviors: complex/ongoing activity triggered by stimuli (orienting, motivating)
• sow bug kinesis: attracted to moisture, stimuli directs movement
• fixed action pattern was discovered by konrad lorenz
• fixed action pattern:

  1. action-specific potential: motivation
  2. innate-releasing mechanism: selective response to stimuli
  3. fixed motor pattern: respond by innate, repetitive motor activity
• example of fixed action pattern:

  1. motivation: keep eggs together to incubate
  2. stimuli: see egg or resembling object outside nest
  3. motor: roll egg back to nest with beak
• imprinting occurs during certain development window, irreversible behavior
• TInbergens 4 questions:

  1. function/adaptation
  2. causation/mechanism
  3. development/ontogeny
  4. evolution/phylogeny