Life Science

• Species are not immutable. We watch and cause them to change
• Evolution is a change in allele frequencies within a population
• A gene is a section of DNA instructing on how to produce a trait
• An allele is one variant of a gene
• Natural Selection is 3 things: Variation, Heritable, Differential reproductive success
• If the 3 conditions for natural selection are occuring, evolution by natural selection is happening
• Persistent selection can dramatically change the morphology, behavior, and physiology of the individuals in a population
• Directional selection: selection that favors one allele over another (cow breeding to produce more milk over time)
• Stabilizing Selection: The selection that favors individuals that are more stable in their phenotype (Babies stay a certain weight over time)
• Disruptive Selection: A type of selection that favors individuals with extreme phenotypes (Small and big fish get territory, but the middle sized fish is pushed out)
• To enhance cooperation you: tinker with perceived costs and benefits, distinguish the cheaters from kind people, and reduce the perceived vulnerability of partners
• Kindness why and when: shared genes, reciprocity, and maladaptive behavior
• When "r" is really large, cooperation becomes extreme
• ur body has two systems for responses to stimuli and coordinating info within the body:

  • Hormones
  • Neurons
• A nervous system collects information about the organism’s internal and external environments, processes that information, and responds by sending signals to muscles and glands
• Glial cells: the support staff for neurons

  • Outnumbers neurons 10-50x
  • Insulates axons with myelin
  • Induce tight junctions between neurons
  • Provide nutrients to neurons
• nervous system functioning:

  1. Signal (Initiates action potential in response to external stimuli: sound, smell, sight, etc)
  2. Travels from dendrite down axon
  3. Synapses with another cell (a muscle, gland, or another neuron; causing a response)
• Neurons are specialized for receiving electrical and chemical info via dendrites and transmitting it via axons
• Action potential:

  1. Resting State
  2. Depolarizing State
  3. Repolarizing State
  4. Undershoot
  5. Return to Resting State
• An action potential is a self-propagating, all-or-none change in the membrane potential, that travels down an axon
• Estrogen: Maintains and regulates female reproductive system

  • Improves object memory
  • Improves manual dexterity 
  • Improves performance in articulation
  • Effective treatment for depression 
• Testosterone: Maintains and regulates male reproductive system and secondary sex characteristics

  • Improves performance on spatial tasks (mental rotation in humans, maze running in rats)
• Initial energetic investment in reproduction is typically larger for females because of larger gametes, internal gestation, and lactation
• Because female reproductive investment is initially higher, they are vulnerable early on in the process. We expect the evolution of more discriminating mate choice
• Initially lower reproductive investment and paternity uncertainty lead to male-male competition for access to mates, reduced choosiness, mate guarding, and sperm competition
• Polygyny - One male bonds with multiple females
• Polyandry -  one female bonds with multiple males
• Monogamy: one female bonding with one male
• Our senses are all variations on a theme: cells responding to physical or chemical stimuli by opening channels within neurons and stimulating or blocking action potentials
• Synapse Functioning:

  1. Action potential arrives at terminal button 
  2. Calcium channels open and calcium rushes in
  3. Vesicles fuse with terminal button membrane
  4. Neurotransmitter dumped into synapse
  5. Neurotransmitter binds with postsynaptic receptors, causes: muscle contraction or action potential
  6. Re-uptake/enzymatic breakdown of neurotransmitter
• At the synapse, an action potential is converted to a chemical signal, releasing neurotransmitters to stimulate tissue or another neuron
• How our pleasure center works:

  1. Neuron is stimulated (in response to your behavior)
  2. Dopamine is released into the synapse
  3. Receptors on adjacent cells bind to dopamine and fire
  4. Happiness ensues
• Seretonin: A neurotransmitter that affects sleep, appetite, anxiety, and mood
• When you block the reuptake transporter protein for serotonin, it reduces depression (Zoloft, Prozac, etc)
• Adenosine: Over the course of a day, adenosine builds up in brain synapses, when adenosine receptors are filled, the ion channels open and the cell becomes less likely to fire. Adenosine is like a brake to brain activity. (And when you sleep, it is reabsorbed)
• Inclusive fitness = direct fitness + indirect fitness
• Hamilton's Rule: B * r > C
• How to determine coefficient of relatedness: every connection between a parent and their offspring is 0.5, you find every way two individuals could have inherited the same allele from an ancestors, for each path you calculate the probability, and then add the probabilities for each possible path
• Spatial association: treat those around you as kin

  Social association: treat those from childhood as kin

  Phenotype matching: treat those who resemble you as kin
• Hormones are regulators, secreted by glands, that alter gene function in target cells elsewhere in the body. They help regulate growth and development, responses to the environment, and homeostasis