E.6

Further Studies of Behavior

E6.1• Honeybees are eusocial animals that live in colonies.• Offspring are born with designated responsibilities and functions (Castes)• Castes: Queen, Worker, Drone• Queen:

– Produces eggs– Flies only to mate– Controls colony activity with scent– mates only once and stores sperm throughout life– Lays thousands of eggs

• Worker:– All females, sterile– Harvest and produce food– Feed Queen and Drones– Defend colony from attack– Live about 30 days– Nurse young bees– Build Hive

• Drone:– Haploid males– Mate and then die

E6.1• Meerkats live in colonies called mobs• They consist of 20-30 meerkats• Meerkats have an alpha class of meerkat,

which is groomed by the subordinate class• Subordinate females will babysit and feed

alpha females offspring• Meerkats build elaborate underground

network tunnels to live in.• Some meerkats are designated to be

sentry meerkats. • Sentry meerkats stand watch and signal to

other meerkats when danger approaches• Sentry meerkats are the first to leave the

burrow to check for danger

E6.2

• A whole colony is more than the sum of its parts• All the individuals are closely related• Certain advantageous traits in a caste of the colony will

improve the fitness of the queen of that colony. • The genes for that colony’s caste will get passed on to

the next queen of the next colony.• Honey Bees with traits advantageous for finding food

will increase the survival chance of their queen and eventually outcompete other queen and their colonies for food.

E6.3

• Altruistic Behavior (behavior in which an organism will support other organisms at a cost to itself) evolves when the behavior increases the chances of the altruist’s genes being propagated.

• It is based on a cost-benefit analysis• The cost is the risk an organism takes when

performing altruistic behaviors• The benefit is the chance that the altruistic

behavior will cause the genes to be propagated

E6.3

• Honeybees will sting aggressors to the colony and die themselves

• They decrease their own fitness by 100% to increase the fitness of the colony

• Workers are sterile and thus have no chance of passing on their genes

• So, there is little risk of losing fitness when a worker dies for the queen, which has all of the worker’s genes

E6.4• Werner and Hall conducted

experiments with Bluegill fish eating Daphnia

• The fish will alter its behavior to minimize the costs (movement) of finding food and maximizing the benefits (nutrition)

• When daphnia are high in population, bluegill fish eat the largest daphnia to maximize their nutrition.

• As daphnia become less dense in population, the bluegill fish starts to eat smaller daphnia in equal proportion

E6.4

• The Northwestern crow eats a gastropod called the whelk.

• To eat whelks, the crow must drop the shell from a certain height a certain number of times to break it.

• Flying higher costs energy, but flying multiple times costs energy as well.

• The crows minimize the cost of breaking the shell by always dropping the shells from a certain height to minimize return trips without flying unnecessarily high.

E6.5• Sexual selection can lead to exaggerated

traits• When mates are selected based on a

trait, those traits give the organism more fitness and a higher likelihood to reproduce.

• So, while the trait may not have other useful features except mate selection, organisms without the traits are naturally selected out

• The trait becomes more exaggerated as further generations choose mates with more exaggerated variations of the traits

• Peacocks, for example, choose the male mates based on the display of their tail feathers.

• Those with larger and more colorful tail feathers are chosen and pass on their genes.

• Throughout the generations, peacocks with more and more colorufl feathers are selected and pass on their genes.

E6.6

• Animals show rhytmic variations in activity• There are:– Diurnal (daily) cycles: like wake/sleep – Seasonal cycles: Hibernation– Lunar cycles

E6.7• Deer reproduce seasonally as a seasonal cycle• This adaptation increases the chances of survival of the offspring• Producing more offspring is metabolically expensive• Deer mate in October and November, which

ensures that the offspring will be born in the late spring-early summer

• This increases the chance of the offspring surviving without having to overproduce offspring, wasting resources.

E6.7• The Uca (Fiddler crab) has a lunar

reproductive cycle• The male crabs come out of their

burrows and display their enlarged claws during the full moon and new moon

• The fiddler crabs have this adaptation because it allows them to mate when the tides are ideal for the survival of their offspring.

• The Crabs prefer the receding tides for the release of eggs