HL2 Biology: E.6d Food, Sleep, Sex

DBQ p.335- Rhythmical Behavior Patterns

1. The bats start flying slightly after sunset, and as the sun sets earlier as winter approaches, they follow the change in the sunset time (i.e. start flying earlier). Bats fly relatively shorter flights during autumn, but the frequency of flights increases.

2. (a) During the summer, the flight of the bats are long and last almost the entire night (especially towards the end of the summer), while in autumn, the flights are very short. During the summer, the length of the flights increase as the season ends, while in autumn, it shortens as winter nears. Lastly, flights during the summer seem more detached (have) gaps in individual flights, while in autumn, the flights are more consistent.
(b) In the summer, the bat flights may be longer because it is warmer during the night and they can afford to fly the entire night, while in autumn, it is too cold to fly at midnight, and hence, only fly immediately after sunset. Another reason might be that in the summer, the nights are shorter and they can fly the entire time, while in autumn, the nights get longer, and thus they cannot afford to fly the entire time (energy waste).

3. One may say that the patterns change with the ups and down of sunset/sunrise times and hence change with seasons. However, this argument may be refuted, because this only shows data for one year, and one cannot be sure whether these are just random fluctuations or actual patterns (data from multiple years or cumulative years must be used).


HL2 Biology: E.6b Reciprocal Altruism

Reciprocal Altruism

This type of altruism is very rare, and is thought as a key to human success. We socialize with friends, strangers and non-relatives, which is different from kin selection because you are not doing this to pass down our own genes through relatives. Reciprocal altruism is different in this sense because the whole group benefits together.

Reciprocal altruism is thought to be our evolutionary roots of moral behavior, gratitude, guilt, trust, and so on, as a way to socialize with others to benefit each other.

This behavior is also seen in other organisms, for example, vampire bats. Since these bats lose heat quickly due to their high surface area to volume ratio, they tend to starve quickly. Hence, bats even make friendly relationships with non-relatives to donate or receive blood when either of them are starving.

HL2 Biology: E.6c Kin Selection

Kin Selection

This concept is categorized under altruistic behavior, where one’s own fitness is reduced while others’ are increased, which is formally known as inclusive fitness. Behind this idea is the sharing of genes between relatives, and by unselfishly protecting and caring for relatives, one’s own genes are kept alive and passed down via their relatives.

An example of kin selection is shown in honey bees, whose haplodiplontic lifecycle allows different degrees of relatedness amongst the population. Hence, although they generally protect and care for each other, the worker bees tend to assist their sisters more than their brother drones.

Another example is seen in jackals. When the wild dogs mature, they are ready to leave their family, but often times their parents use their teeth and gently bite the mature child’s neck area to keep them in the family as a babysitter for the next generation of pups.

HL2 Biology: E.3b Learned Behavior

DBQ p. 328- Birdsong- Innate or Learned?

1. Both sonograms I and II display Z. leucophyrys songs of similar durations and frequency ranges. Hweover, the patters of I and II are slgihtly different: while I ends in a pattern of short wavelength sounds, II ends in a decreaseing frequencey patternw with detached sounds.

2. (a) Sonogram III shows a similar duration as with sonograms I and II. Sonogram III ends with a sequence of decreasing frequency notes like in Sonogram II, while sonogram I displays a pattern at the end with short wavelength sounds generally constant in pitch. Furthermore, while sonograms I and II have finer, short wavelength patterns in the second parts of the songs, III shows a less distinct, less fine patter at this part of the song.
(b) The song of white-crowned sparrows is both innate and learned. If the third sonogram is the rudimentary template subsoung, it means that the initial song they know is a result of genes- innate behavior. When seeing sonogram I, this RTS is modified, most likely due to hearing other males’ songs during the critical period of imprinting- learned behavior. Hence, it can be concluded that the song of this bird is a result of both types of behavior. On the other hand, one might say that other males’ songs have no influence and so the variations in I, II, and III are purely innate.

3 (a) Both sonograms V and IV are similar in duration and the general frequency range. However, while V begins with a sustained note of one frequency, IV begins with a series of notes of differing frequencies.
(b) Both sonograms V and I and II are similar in duration and show similar patterns. However, sme patterns are different between V and I and II: while the second part of the song with high-wavelength sounds are shorter in V, they are longer in I and II and the middle part of the song does not follow a distinct pattern in V, whereas in I and II, there are.
(c) One reason why birds rarely imitate other species is that they do not recognize other species’ songs because they are too different from their rudimentary template subsongs. Another reason is, it would be a disadvantage for a bird to learn a different bird’s song because they would end up attracting the females of the other species.
(d) This observation is evidence for learned behavior because the hand-reared birds of V sing a similar song with a different species (strawberry finch- the general frequency, range, parts of the pattern between V and III were similar). However one can refute this argument by saying that these similar parts between V and IV are not a result of imitating the strawberry finch’s song but is a result of imitating a white-crowned sparrow’s song with a similar pattern.

HL2 Biology: E.3a Innate Behavior

DBQ p. 326- Chemotaxis in Woodlice
1. One method to lure the woodlice into the arms of the syringe would be to put another woodlice into one of the arms of the syringe. To keep the second woodlouse already in the arm to not move to the already present woodlouse in the syringe, a small net-like structure can be attached at the very end of one of the arms of the syringe. That way, the woodlouse in the syringe can move into the arm, while the other remains put at the end of the arm. Another method would be to change the independent variable to food scent (put food-scented air into the syringe), but instead of testing chemotaxis, this would test foraging behavior.

2. Generally, in all species, more woodlice moved into the arms of the scented syringe. Furthermore, O. asellus had the highest number of lice moving into both scented and unscented arms of the apparatus (148 and 69 respectively), while A. vulgare had the second highest number for the scented arm and the lowest number for the unscented arm (115 and 55 respectively), and  P. scaber had the lowest number for the scented arm and the second lowest for the unscented arm (101 and 62 respectively).

3. The woodlice must have chemoreceptors because they were able to distinguish between scented and unscented environments, and more were attracted to the scent of the members of their own species.

4. (a) Many subjects moved to the scented arm of the apparatus because they were most likely attracted to the scent of other members of the species, which makes evolutionary sense because finding other members of one’s species is absolutely necessary to reproducing.
(b) Some subjects moved to the unscented arm perhaps because they assumed there was no competition for resources (e.g. food) in that area due to the lack of other woodlice.

HL2 Biology: E.4c Neurotransmitters & Drugs

Addiction to psychoactive drugs

  • Factors contributing to addiction:

1. Dopamine secretion: drugs that are addictive stimulate synapses involving dopamine, which makes the user feel pleasure because dopamine activates the reward pathway.
2. Genetic predisposition: although specific genes are still unknown, addiction to psychoactive drugs is thought to be hereditary, like with alcoholism
3. Social factors: cultural tradition, peer pressure, traumatic circumstances/experiences, deprivation, mental health issues can encourage and even enhance addiction to psychoactive drugs but it can also prevent it

  • Examples
    • Cocaine
      • Excitatory psychoactive drug
      • Highly addictive
      • Mechanism
        • once in the body, it binds to membrane proteins involved in reuptake of dopamine
        • dopamine cannot be absorbed by the presynaptic neuron anymore, resulting in an increased concentration of dopamine in the synapse
        • hence, cocaine users’ reward pathway is artificially stimulated, leading to constant euphoria
        • cocaine-induced depression can occur because of increased tolerance and adaptation by the body, which decreases the secretion of dopamine by the brain
      • Crack: vaporous so easy uptake into body and stronger effects
  • THC (tetrahydrocannabinol)
    • Chemical in cannabis that causes most of the psychoactive effects
    • Receptors are in many places in the brain
      • cerebellum, hippocampus, cerebral hemisphere
    • Mechanism
      • it binds to cannabinoid receptors, which is at a synapse where signaling chemicals are released by postsynaptic neuron to bind to presynaptic neuron
      • THC blocks release of excitatory neurotransmitters
      • hence, THC is an inhibitory psychoactive drug
    • General effects
      • psychomotor behavior, short-term memory is disrupted
      • appetite stimulated
      • other effects noted by users

HL2 Biology: E.4b Neurotransmitters & Personality

Psychoactive drugs

Drugs in general

  • chemical substances ingested/injected/inhaled by a person 
  • changes function of body

Psychoactive drugs

  • change function of brain
  • synapses are altered
    • excitatory drugs: promotes excitatory and inhibits inhibitory neurotransmitter transmission at synapses
    • inhibitory drugs: inhibits excitatory and promotes inhibitory neurotransmitter transmission at synapses
  • how synapses are altered
    • some drugs have similar chemical structure as the neurotransmitter
      • can bind to neurotransmitter receptors on the post-synaptic membrane and acts as a competitive inhibitor
      • usual effect is hindered as well
    • some drugs have similar chemical structure AND effect
      • can bind to neurotransmitter receptors on the post-synaptic membrane and acts as a competitive inhibitor
      • same effect is achieved but cannot be broken down so effect lasts longer
    • some drugs interfere with the recycling of neurotransmitters at a synapse
      • hinders breakdown and/or reabsorption into the pre-synaptic membrane
      • neurotransmitter’s effect is extended
  • examples
    • excitatory
      • nicotine
      • cocaine
      • amphetamines
    • inhibitory
      • benzodiazepines
      • alcohol
      • THC