E.6 Further Studies of Behavior - PowerPoint Presentation

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E.6 Further Studies of Behavior

Honey bees • live in hives with 30,000 – 40,000 individuals • behaviors are integrated into a complex colony • There are three castes of honey bees each of which has different tasks. • The single queen bee is normally the only member of the colony to lay eggs.

E.6.1 Describe the social organization of honey bee colonies and one other non-human exampleSlide2

• The

worker bees do all the jobs that are needed to maintain the colony. • The drones do nothing to help the colony to survive, but if they successfully mate with virgin queens they spread the genes of the colony to new colonies. • Workers eject drones from the colony at the end of the season during which virgin queens are available

•

Scout bees

locate patches of food and communicate the location through a dance languageSlide3

Waggle Dance of the Honey BeeSlide4

Naked mole rats

• form large underground societies with far-ranging systems of tunnels and a central nesting area • colonies may contain up to 80 individuals • contain a division of labor among the colony members with some working as tunnelers while others, depending on the size of their bodies, performing other tasks such as defenseSlide5

• there is also a reproductive division of labor similar to that seen in insects

• other kinds of mole rats live alone or in small family groupsSlide6

E.6.2 Outline how natural selection may act at the level of the colony in the case of social organisms

• all behavior appears to have its beginnings in the underlying genetic program of the individual • innate behaviors may be modified by interactions with the environment • organisms may develop opportunities to learn through their experiences with their environment • any behavioral adaptation acquired may affect the organism’s fitness (their ability survive and reproduce) and are products of natural selectionSlide7

• behaviors that lead to greater reproductive success become more common in a species over time

• few species live totally solitary lives with many living in cooperative groups of the same species in a very organized way • these organisms divide resources and activities between them and are mutually dependent (they do not survive or successfully reproduce outside the group)Slide8

E.6.3 Discuss the evolution of altruistic behavior using two non-human examples

• Altruism is a behavior that benefits others and involves risk or cost to the performer • Altruistic behavior towards non-relatives is usually explained in terms of trade-offs, where individuals weigh up the costs and benefits of helpful behavior • Cooperation will evolve in systems where, over time, individuals will obtain some benefit such as survival and reproduction • In many bird species, parents are assisted in raising their young by other birds called “helpers at the nest”Slide9

• In species of both mammals and birds, individuals that detect a predator will send out an alarm signal, alerting other members of their group even though it calls the predator’s attention to the caller

• Lionesses with cubs will allow all cubs in the pride to nurse, including cubs of other females • Other example (wolves) in Senior Bio 2, pg 207 show cooperative hunting and defenseNOTE WELL; Parental care is not considered to be altruismSlide10

Altruism transcending speciesSlide11

Wolves coordinating attack against grizzly bearSlide12

E.6.4 Outline two examples of how foraging behavior optimizes food intake, including bluegill fish foraging for

Daphnia • Foraging is a type of behavior that involves a trade-off between a food’s energy content and the cost of obtaining it • Natural selection favors individuals whose foraging behavior is as energetically efficient as possible; i.e. animals feed on prey that maximize their net energy intake per unit of foraging time • Animals that acquire energy efficiently during foraging may increase their fitness by having more energy available for reproductionSlide13

Example:

1. shore crabs • feed primarily on intermediate-sized mussels which will give them the greatest energetic return • larger mussels would give them more energy, but would take much more energy to crack openSlide14

2

. bluegill sunfish • when feeding on Daphnia, bluegills do not feed randomly but tend to select prey based on “apparent size”, selecting larger prey individuals, which supply the most energy • however, smaller prey will be selected if larger prey are too far away because more distant, larger prey will expend more energy to acquire • the proportion of small prey to large prey eaten also varies with the overall density of prey • experiments have shown that bluegills foraged nonselectively at lower prey density, but at higher prey density, they favored large preySlide15
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3. smallmouth bass

• consume both minnows and crayfish with no overall preference; minnows are the optimal prey in some situations, and crayfish in others • minnows contain more usable energy per unit weight (crayfish have the harder to digest exoskeleton), but they may require more energy to pursue • crayfish, though easier to catch, have large claws and more aggressive resistance making them harder to subdueSlide17

• there are also trade-offs in the relative abundance and size of each type of prey

• the bass is able to integrate all the relative variables and respond in a highly efficient foraging behavior involving switching between minnows and crayfish as conditions changeSlide18

E.6.5 Explain how mate selection can lead to exaggerated traits

• The success of an individual is measured not only by the number of offspring it leaves, but also by the quality or likely reproductive success of those offspring • Who the mate is, then, becomes important • Darwin introduced the concept of sexual selection which is a special type of natural selection that produces anatomical and behavioral traits that affect an individual’s ability to acquire matesSlide19

• There are two types of sexual selection:

intrasexual (male-male competition) and intersexual selection (mate choice) See Senior Bio. Pp. 342 (green book) • In intersexual selection, males generally advertise themselves as potential mates and the females choose among them • Intersexual selection results in exaggerated traits, such as elaborate plumages • Female preference for elaborate male ornaments is well documented and selection strongly favors any trait that confers greater ability to outcompete other malesSlide20

• This has resulted in males tending to be larger than females since larger males would intimidate smaller males and would be the one to mate with the female

• The result of these differences is referred to as sexual dimorphism • Examples include: 1. the long-tailed willow bird • females prefer males with long tails • when tails have been artificially shortened or lengthened, females still preferred males with the longest tails; may represent healthiest or oldest male Slide21

2

. male peacock • female peahens prefer to mate with males having greater numbers of eyespots in their tail feathers • to the female, this may represent better health and success at living longer, which genetically may be passed to her offspring (still being debated by biologists)In both cases, it is believed that natural selection has favored the evolution of behaviors that maximize the reproductive success of males and femalesBy evaluating and selecting mates with superior qualities, an animal can increase its reproductive successSlide22
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E.6.6 State that animals show rhythmical variations in activity

E.6.7 Outline two examples illustrating the adaptive value of rhythmical behavior patterns • Environmental cues, such as day length, timing, and the height of tides, temperature, and phase of the moon are often used by animals to establish and maintain a pattern of activity • These cues assist in survival by synchronizing important events in the life cycle of an organism such as mating, birth, rearing of offspring, collection and storage of food reserves and body fat, and periods of torporSlide24

• Biorhythms

in response to environmental stimuli are said to be exogenous because the stimulus is external to the organism • Rhythms that continue in the absence of external cues are said to be endogenousSlide25

Two examples showing rhythmical behavior patterns are:

1. Northern flying squirrel • An inhabitant of forests in N. America • Active at night and usually sleeps from dawn to dusk • Experiments with flying squirrels have shown that environmental cues are needed to keep biological clocks tuned to external conditions • External cues, such as day length and night length, adjust the clock, so that the rhythmic behavior it controls is synchronized with the outside worldSlide26

• If a squirrel is placed in constant light or constant darkness, its rhythmic activity continues, but the duration of its activity (one period of activity plus one period of inactivity) falls a little more out of sync with the outside world each daySlide27

2. Coordinated spawning in corals

• Broadcast spawning by corals is a tightly synchronized process characterized by coordinated release of gametes with 30-60 minute time windows once each year • In shallow water corals, annual water temperature cycles set the month, lunar periodicity the day, and sunset time the hour of spawning • This regulation is critical for achieving high fertilization rates