FURTHER STUDIES OF BEHAVIOUROption E.6
ASSESSMENT STATEMENTS E.6.1 Describe the social organization of honey
bee colonies and one other non-human example.
E.6.2 Outline how natural selection may act at the level of the colony in the case of social organisms.
E.6.3 Discuss the evolution of altruistic behaviour using two non-human examples.
E.6.4 Outline two examples of how foraging behaviour optimizes food intake, including bluegill fish foraging for Daphnia.
E.6.5 Explain how mate selection can lead to exaggerated traits.
E.6.6 State that animals show rhythmical variations in activity.
E.6.7 Outline two examples illustrating the adaptive value of rhythmical behaviour patterns.
SOCIAL ORGANIZATION Two or more animals interacting with
each other Some animals show limited interaction
while others are extremely sociable Examples?
HONEY BEE COLONIES Nest above ground, usually inside a hollow
tree Wax combs with individual compartments
(cells) for storing honey and rearing young Each hive has one queen whose job it is to lay
eggs Workers are also female, but sterile Workers search for nectar and pollen;
make wax and honey; and feed and protect the young
Workers live for about 6 weeks; queen up to 2 years
Male honey bees (drones) develop from unfertilized eggs and mating with queen is only function
OFFSPRING Queen lays eggs in cells Unfertilized eggs = males Fertilized eggs = females
All fed glandular secretions called royal jelly for the first few days
Larvae destined to be workers are then switched to a less nutritious diet of honey and pollen
Those destined to be queens continue to be fed royal jelly
PHEROMONES Secretions produced by queen to control the
hive Inhibit ovarian development in workers Passed by licking pheromone from queen’s
body and then transferring to food which is exchanged
Most colonies: 60,000 in number If colony gets too large, queen leaves with
“swarm” and establishes a new hive leaving a new young queen behind
SOURCE OF FOOD “scout” bees find source of nectar and
do a waggle dance to indicate the direction and distance of the source
Another chemical is released from the mouth area when the colony is in danger and the signal is spread around to the others
ROLES OF BEES IN THE SOCIAL ORGANIZATION OF THE COLONYQueen Fertile female •Lays eggs
•Produces pheromones which calm the colony and cause other females to be sterile
Worker Sterile female •Feeds the larvae•Produces wax and honey•Searches for nectar and pollen•Protects the hive
Drone Fertile male developed from an unfertilized male
•Mates with the queen
Life cycle video
SOCIAL ORGANIZATION IN CHIMPANZEES Most of our knowledge attributed
to Jane Goodall (ethologist) Highest order of chimp society is
the community Made up of 40-60 members Party smaller group within the
community Party may be all male, a family, or a
nursery unit Make up of parties depends on the food
supply
HIERARCHY Males
Highest ranking is 20-26 yrs old Dominance determined by physical fitness
and fighting ability Strong social bonds exist
Important for keeping out intruders, hunting, and sharing food
Females Dominance in females is linked to age May migrate to other communities Responsible for care of young
COMMUNICATION AMONG CHIMPANZEES Facial expressions Vocalizations Chimp Talk
NATURAL SELECTION Acts on entire honey bee colony, not
individuals Genes selected are those that promote
social organization Pheromones How to find nectar Making of wax Taking care of young
ALTRUISM Worker bees are altruistic They help the queen produce offspring
rather than reproduce themselves Kin selection causes the evolution of
altruism Result is a decrease in fitness* of the
altruist and an increase in the fitness of a close relative
*ability to survive and reproduce
Belding’s ground squirrel Live in mountains of
southwest U.S. Preyed upon by
hawks and coyotes When a predator
approaches, one of the ground squirrels gives a high-pitched call which alerts the rest of the population to the nearby danger
Alarm squirrel (usually female) is more likely to be killed
Females live close to their family, while males live afar
Alarm squirrel does not increase its own fitness but it is increasing the fitness of its relatives
If all the female’s close relatives are dead, she does not sound alarm calls
Naked mole rats Rat colonies can be
up to 100 individuals Live in burrows in
East Africa Workers make
nesting chambers and forage for plant roots needed for food which it brings to queen
Larger workers stay near queen and young
Queen suppresses the sexual behavior of the other females by secreting pheromones in her urine
Also suppresses sexual behavior of the males by bullying except when she is in estrus (ovulating)
Main predator is snake Queen will send workers to attack
snake Workers are sacrificed so queen can
live and preserve the genes of the family
FORAGING BEHAVIOR OPTIMIZES FOOD INTAKE
What an animal eats is essential to survival and ability to reproduce
Behavioral ecologists study foraging behaviors and predict how an animal will forage in a certain set of conditions
They base their predictions on cost-benefit analysis of the behavior
Cost – energy used to locate, catch, and eat food
Benefit – calories of energy gained
SMALL MOUTH BASS Forages for either
minnows or crayfish Minnows have
more energy per unit weight
Crayfish are easier to catch
Small mouth bass show no preference
Each may be optimal under different conditions
BLUEGILL SUNFISH Eats Daphnia Bluegill sunfish
usually forage for the larger ones
They will select smaller Daphnia if the larger ones are too far away
Not selective when density of Daphnia is low
Selective for larger if high density
SCIENTIFIC PREDICTION & RESULTS Prediction:
Bluegills would eat large Daphnia 100% of the time
Results: bluegills only ate large Daphnia 57% of the time
Reasons? Young bluegills not
as efficient as the older ones
Lack of ability to see the size?
Lack of skill?
MATE SELECTION LEADS TO EXAGGERATED TRAITS
Females prefer more highly decorated males
Also size and shape of their tales
Largest tail signifies the healthiest bird with the best chance for healthy offspring
Quality of tail measured by number of eyespots that it has
Studies show that the more eyespots a peacock has the higher number of mates it has
Experiments show that offspring of males with larger tails and more eyespots are larger at birth and survive better in the wild
Could peacock tails become a disadvantage?
Animals show rhythmical variations in activity Reproductive
rhythm Once a year coral
release millions of gametes in a synchronized mass spawning ritual
Predators overwhelmed with more food than they can eat
Feeding behavior North American flying squirrel flies at night Gets the most food and the least
competition
Daily rhythms Diurnal and circadian are both used
to describe a 24-hour cycle of behavior Behaviors are controlled internally
(endogenous), but external (exogenous) cues such as light are important in sychronization
Flying squirrel experiment Placed in total darkness, activity
continued on a 24-hour cycle even without light
Biological clocks are internal mechanisms which keep the animal in sync with its environment, but external cues regulate the biological clock so that it fits a changing environment
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