BIOL 107 Lecture Notes - Eusociality, Phloem, Waggle Dance

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Published on 25 Jan 2013
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53.4
behaviour can evolve into systems of information exchangecommunication, which may become
elaborated as displays or signals, if it benefits both the sender and receiver
animals communicate using sensory modes, differing in how it is performed, properties of signals,
and what can be communicated
visual signals: easy to produce, come in endless variety, can be changed rapidly, clear indicate
position of signaller
o not useful at night or low light areas; predators can use deception
pheromones: molecules used for chemical communication btwn individuals of same species;
specific, information-rich messages
o ex mammals marking territory/trails
o remain in environment longer than visual signals, but not rapid exchange
auditory signals: cannot convey complex info as rapidly as visuals, but can be used at night or in
dark areas
o transmitted in complex environments (forests), receiver does not have to focus on signaller;
can communicate over larger distances than with visual signals
tactile signals: used when visuals signals is difficult (ex dance of honeybees)
o waggle dance: conveys info about distance and direction of food source
o round dance: food source is within 80 metres; involves bee running rapidly in circle and
reversing direction; odour (indicates flower) + dance = chemical + tactile cues
electrical signals: used by fish to generate electric fields in water by emitting electrical impulses;
used for sensing objects and communication
o males emit lower frequencies, females higher, and relates to status in group
o can determine sex, identity, social position of fish by electric signals; locate prey by
distortions in electric field
53.5
social behaviour evolves when cooperating conspecifics achieve higher rates of survival and
reproduction than if they had lived alone (ants, bees, wasps, lions)
many degrees of social system complexity exist among living species
social systems are dynamic; individuals repeatedly communicate with one another and adjust
relationships b/c costs and benefits experienced by individuals change with age, sex, physiological
condition, status
must understand how individuals that join together benefit from doing so
groups may confer many types of benefits (hunting success, expand food range) [hawk most
successful when attacked solitary pigeons)
but costs a lotinterferes with food (pigeons’ seeds) and inhibit others’ attempts to produce or
injure offspring; higher exposure to diseases and parasites
most widespread form of social system (SS) is association btwn 1/2 parents with immature,
independent offspring; some have more adult individuals
simple mammalian SS, solitary females pairs care for young, older offspring may still be present
when next generation is bornhelp rear newborns; females stay in group but men usually leave.
Thus most helpers are females
altruistic acts: behaviours that reduce helper’s reproductive chances but increases fitness of
helped individual; favoured by natural selection
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