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BMEN 515 Lecture Notes - Inclusive Fitness, Eusociality, Natural Selection

Biomedical Engineering
Course Code
BMEN 515
William Huddleston

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Animals must find their way around their environment
PILOTING: ORIENTATION BY LANDMARKSmost animals find their way by knowing and remembering the structure of
their environment piloting.
HOMING: RETURN TO A SPECIFIC LOCATIONthe ability to return over long distances to a nest site, burrow, or other
specific location homing.
o Distance-and-direction navigation: requires knowing in what direction and how far away the destination is. With
a compass to determine direction and a means of measuring distance, humans can navigate.
o Bicoordinate navigation: true navigation, requires knowing the latitude and longitude of both the current
position and the destination.
o How do animals determine distance and direction Two obvious means of determining direction are the sun and
the stars.
o The stars offer two sources of info about direction: moving constellations and a fixed point. One point that does
not change during the night is Polaris (North Star) and always indicates north.
How Do Animals Communicate with One Another?
Visual signals are rapid and versatile
Visual signals are easy to produce, come in an endless variety, can be changed rapidly, and clearly indicate the position
of the signaller.
Most animals are sensitive to light and can receive visual signals.
The extreme directionality of visuals signals means that the received must be looking directly at the signaller.
Not useful at night or in environments that lack light.
Chemical signals are durable
Molecules used for chemical communication between individuals of the same species are called pheromones. It can
communicate very specific, information-rich messages.
Pheromones remain in the environment for some time after they are released.
Vocal and visual displays disappear as soon as the animal stops signalling or displaying.
Its durability makes them useful for marking trails, marking territories, or indicating location.
Unsuitable for rapid exchange
Auditory signals communicate well over a distance
Auditory signals cannot convey complex info as rapidly as visual signals can.
Can be sued at night and in dark environments.
Can go around objects that would interfere with visual signals; can be transmitted in complex environments (e.g.
Often better at getting attention of receiver b/c receiver does not have to be focused on the signaller to receive the
Useful for communicating over long distances.
Tactile signals can communicate complex messages
Animals in close contact use tactile interactions extensively, especially under conditions in which visual communications
is difficult.
Electric signals can convey messages in murky water
Some species of fish generate electric fields by emitting a series of electric pulses and can be used both for sensing
objects in the immediate surroundings and for communication.
Why Do Animal Societies Evolve?
Social behaviour evolves when, by cooperating, conspecifics individuals can achieve higher rates of survival and
reproduction than they would if they lived alone.
Social systems are dynamic; individuals repeatedly communicate with one another and adjust their relationship. Their
relationships change regularly b/c costs and benefits experienced by individuals in a social system change with their age,
sex, physiological condition, and status.
Group living confers benefits but also imposes costs
It may improve hunting success or expand the range of food that can be captured.
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