Download Concept 40.4 Moving through Space Presents

Chapter 40
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Key Concepts
40.1 Behavior Is Controlled by the Nervous
System but Is Not Necessarily Deterministic
40.2 Behavior Is Influenced by Development
and Learning
40.3 Behavior Is Integrated with the Rest of
Function
40.4 Moving through Space Presents
Distinctive Challenges
40.5 Social Behavior Is Widespread
40.6 Behavior Helps Structure Ecological
Communities and Processes
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Of all animal characteristics, adjustments
of behavior are often the most visible
responses to environmental change.
◦ Example: Many migratory animals are changing
the timing of their migrations in response to
climate change.
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Behavioral shifts into new habitats may be
the best hope for survival if conditions
where they currently live become too
warm.
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An animal’s nervous system activates and
coordinates behaviors.
In humans, particular types of behavior
depend on the function of particular brain
regions; for example, if Broca’s area is
damaged, the person will have difficulty
speaking and writing.
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Other evidence for the neural basis of
behavior comes from the study of highly
stereotyped animal behaviors, called fixed
action patterns:
◦ Expressed by animals without prior learning and
often resistant to modification by learning
 Examples: begging behavior by gull chicks, web
spinning by spiders
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Behaviors evolve: if certain alleles produce
more adaptive behaviors than others,
natural selection can favor those alleles.
Many studies establish that genes can
exert important effects on behavior.
Drosophila (fruit flies)mutants for the gene
per have altered circadian rhythms.
When the flies are kept in constant
darkness, episodes of activity followed 19hour or 29-hour rhythms, depending on
the mutation.
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Experiments with wild populations of
house mice collected from Florida to
Maine.
When the wild mice were reared in the lab
in identical conditions, mice from
progressively more northern populations
tended to build bigger nests.
This points to evolution by natural
selection of a genetically controlled,
behavioral propensity to build bigger nests
in populations from locations where big
nests are an advantage.
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Studies using artificial selection show that behavior
can evolve rapidly.
In an experiment with mice, individuals that ran the
fastest on a running wheel were selected for mating.
Their offspring were selected in the same way for
many generations.
After 13 generations, the selected mice on average
ran more than twice as far as control mice.
Further studies showed critical changes in the brains
of the selected mice, indicating that a difference had
evolved in the neural control of running behavior.
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Biological determinism: behaviors of
animals are hardwired by genetics
Some simple animals exhibit determinism.
◦ Example: Clams are inflexible in many of their
responses to their environment.
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Biological determinism was once applied
to human behaviors.
At one time, it was believed that mental
capacity was correlated with brain size and
that the mental capacities of racial groups
could be predicted by measuring relative
brain sizes.
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Although support for the idea of biological
determinism waned during WWII and the
Holocaust, when people were slaughtered
based on the idea of genetic inferiority,
there is an increasing trend of support for
determinism today.
It is important to remember that articles
written for the general public are not
always well supported by objective,
statistically supported, relevant data for
scientific conclusions.
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Behavior is dramatically more flexible than
any other biological trait. This is true in
part because learning modifies behavior.
New research also shows epigenetic
effects on behavior, which can have
lifelong influences and may be transmitted
from one generation to the next.
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Learning: the ability of an individual animal to
modify its behaviors as a consequence of
individual experiences
Experiments with mice show that
they learn the layout and hiding
places of their environment and
that this learning helps them
escape predation by screech owls.
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Behavioral imprinting: early studies of
animal behavior by Konrad Lorenz showed
that geese hatchlings learned to view him
as their “parent” if he associated with them
right after hatching.
This type of learning takes place in a
narrow window of time early in postnatal
life and, after that, is inflexible.
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Indigo buntings migrate at night and
navigate by the stars.
Experiments showed that they must know
where the north star is and that this must
be learned during the 1st few weeks of life.
In a planetarium, young birds learned to
identify any star that the sky appeared to
be rotating around.
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The males of many bird species use
specific songs to attract females.
The songs are not inherited, but must be
learned in the 1st month after hatching
from the father, who is singing nearby the
nest.
Particular brain regions are required for
this learning.
If a young male learns the song of a
different species it will later sing an
incorrect song and attract females of the
incorrect species.
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An animal’s early experience can have
multiple lifelong effects.
Experiments with rats show that
individuals whose mothers exhibited high
levels of maternal care during the nursing
period were less likely to exhibit fear in
novel situations when they were adults.
Regulatory genes in stress-response
biochemical and hormonal pathways are
tagged with epigenetic marks in early life
and are maintained throughout life.
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Malnutrition and abandonment in early life
are also known to affect epigenetic
tagging in rats.
Marks from these early experiences persist
into adulthood, altering gene expression
and behavior throughout life.
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Migratory locusts in Africa can cause crop
devastation. An individual locust can
display two different behavioral
phenotypes:
• Avoiding other individuals—the population is
spread out and inconspicuous.
• Highly gregarious—the population forms a
swarm.
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Individuals become a swarm if forced into
close contact, that is, if they are forced to
feed next to each other because of food
shortage.
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Pronghorn running illustrates that an animal’s
behavior often depends on and is integrated
with the animal’s other characteristics.
Pronghorn have the highest speeds known in
running animals.
To behave in this way, they must have muscles
that use aerobic respiration and systems to
deliver O2 to the muscles at high rates, such as
large lungs and muscle cells
packed with mitochondria.
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Toads and frogs evolved different
behaviors that depend on the type of ATP
synthesis:
◦ Western toads hop away from danger at
relatively slow speeds that can be maintained
for many minutes.
◦ Leopard frogs hop away from danger at
lightning speed but are fatigued quickly.
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Toads have high levels of the enzymes
needed for aerobic ATP production, frogs
have high levels of enzymes needed for
anaerobic ATP production.
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Behaviors are often integrated with body
size and growth:
◦ Male elk are reproductively mature at two years of
age, but rarely mate before they are five because
they must also be big enough and experienced
enough to dominate other males.
◦ Young spotted hyenas are limited in their ability
to compete with adults during group feeding
behavior at a kill because their teeth and jaws are
not developed enough to crush bones.
Spotted hyenas of various ages
were given a standardized “bonecrunching test.” The amount of
bone they could consume in 15
minutes increased dramatically as
they aged and their jaws and jaw
muscles became stronger. Young
animals are limited in their ability
to compete with adults during
group feeding behavior at a kill.
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Navigation: the act of moving toward a particular
destination or along a particular course
• Following trails: worker ants that find a food source lay
a pheromone trail to guide other ants to the food.
 Pheromone: chemical compound or mixture that is emitted
into the outside environment that elicits specific behavioral
responses from other members of the species
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Orientation: adopting a position, or a path of
locomotion, relative to an environmental cue such
as the sun
Navigation
Path integration:
Cataglyphis ants live
underground in hot,
dry deserts, but
workers forage above
ground during the
heat of the day.
 They find heatkilled insects
before the bodies
have dried out,
and thus get water
as well as food.
 The workers can
always run straight
back to the nest
using path
integration.
 The worker ant monitors the length and compass direction of
each segment of its outbound path.
 Then it puts together the information on segment lengths and
directions to know where it is relative to its nest.
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Orientation
◦ Homing pigeons can fly back to their home
nests even after having been transported tens of
kilometers away.
◦ One mechanism they use is a sun compass:
 The birds must observe the position of the sun and
also must know the time of day. They adjust their
angle of flight relative to the sun, using their
circadian clock to know time of day.
 If the pigeon’s circadian clock is entrained with
artificial light cycles to be 6 hours off, it will fly in a
direction 90° from the correct direction.
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Redundancy in orientation mechanisms is
also important.
Homing pigeons can also find their way
home on cloudy days. They can detect
Earth’s magnetic field and orient to it.
Homing pigeons also sometimes use
landmarks such as hills to orient, and they
may use odors, low-frequency
environmental sounds, and learning from
other pigeons.
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Many insects and birds can determine
compass directions by detecting patterns
of polarized light in the sky; requires
specialized photoreceptors.
The suns rays are reflected by dust, water
droplets, and ice crystals in the
atmosphere and become polarized, or
aligned parallel to one another.
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The Cataglyphis ants in the desert use
prominent landmarks if they are present
but orient equally well without them using
polarized light.
They also have a sun compass.
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Honey bee workers can communicate the
location of a food source in a specialized
behavior called the waggle dance.
During a foraging flight, a worker
measures distance to the flowers by
visually monitoring the rate at which she
flies past local landmarks.
To measure direction, she monitors the
angle of her flight relative to the compass
position of the sun.
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Some animals make fantastic long-distance
migrations.
Bar-tailed godwits migrate between Alaska and
New Zealand, flying non-stop across the Pacific
Ocean for 6 to 9 days.
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Loggerhead sea turtles hatch out on
beaches, and the young turtles head for
the sea.
Using genetic markers, researches have
found that turtles that hatch in Florida
migrate across the Atlantic to African
waters, then back to Florida.
Ocean currents help them traverse the sea.
The turtles use Earth’s magnetic field to
help them complete their journey.
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Disadvantages of living in groups:
• Groups of animals are more visible than
individuals.
• Diseases can spread more easily within a group.
• A group may rapidly deplete food or other
resources in an area.
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Biologists presume that group living has
evolved only if it provides advantages that
exceed its disadvantages.
Much research today focuses on testing
hypotheses regarding how individuals in a
society benefit from living together in a
group.
For some groups, there are physiological
advantages—penguins that huddle
together to reduce thermoregulatory
costs.
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In some groups, all individuals have equal status.
One advantage is increased awareness of danger.
◦ A group of 50 animals has 100 eyes instead of only 2.
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A goshawk’s success in capturing a pigeon in a flock
decreases as the number of pigeons in the flock
increases.
Belding’s ground squirrels live in large colonies in
open meadows and use alarm calls to reduce
predation risk.
Aerial predators almost never capture a ground
squirrel after the alarm whistles have begun.
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Animals in groups
may find preferred
environments more
easily.
In experiments with
golden shiner fish,
researchers found
that the larger the
school, the more
successful they were
at finding their
preferred low-light
habitat.
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In some societies, individuals have
differing status.
Vervet monkey groups have multiple
subadult and adult males, along with
females and youngsters.
One adult male dominates all other adult
and subadult males in the group and has
the best chances of mating with the adult
females.
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Impala antelopes have two subgroups—
one is all males that do not get to mate
with females.
The other group has one male and many
females.
The dominant male has to expend a lot of
energy to repel other males and keep
females from leaving, which is exhausting;
they tend to retain dominance for only a
few months.
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In the case of dominant males, the benefit
to the group may be that becoming
dominant is a test of a male’s strength,
endurance, and other properties critical for
success.
Females that mate with the dominant male
thereby ensure that their offspring are
genetically well endowed.
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In social insects such as honey bees, a
single female (the queen) is reproductive
and lays eggs.
Occasionally she produces a few male
offspring (drones) that produce sperm.
But most of the thousands of other
individuals in the colony—all of which are
her offspring—are sterile female worker
bees.
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Eusociality is a social structure in which
some members are nonreproductive and
assist the reproduction of fertile members
of the group, typically their mother.
Altruism: any characteristic of an
individual that imposes a cost on that
individual but aids another individual
◦ Workers in eusocial colonies exemplify altruism.
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In ecological communities, the behaviors
of animals often give structure to the use
of time and space and to interrelationships
among species.
◦ Example: Some animals are active only during
daylight hours, and others are active only at
night. These behavioral differences determine
whether two species encounter each other.
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Behaviors can result in reproductive
isolation.
Two species of Peromyscus mice will breed
in captivity and produce fertile offspring.
But hybrids rarely occur in nature because
the two species prefer different types of
woodlands, and thus rarely encounter each
other.
Behavior is thus a key factor in allowing
species to maintain their species
distinctions.
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Several of Darwin’s finch species on the
Galápagos Islands can interbreed, but
behavior ordinarily keeps the species distinct.
Males learn their songs from their fathers, and
a female typically will mate only with males
that sing the correct song for her species.
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Many animals within a population restrict
their movements to limited areas.
Behavior can structure the space available.
The region occupied by an individual is a
territory if the individual actively keeps out
other individuals of the same species.
It is called the home range if other
individuals are not excluded.
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Cost–benefit approach: assumes an animal
has a limited amount of time and energy,
and therefore cannot afford to engage in
behaviors that cost more to perform than
they bring in benefits
A study of bumblebee foraging showed
that the energy costs of flying and keeping
the flight muscles warm while sitting on a
flower is higher in cold air than warm air.
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The amount of energy received in nectar
from rhododendron flowers was also
determined.
In cold air, a bee needed to visit 7 flowers
per minute to equal the foraging cost, but
was able to visit 20 per minute.
Thus foraging on rhododendron in cold
weather has an advantage and the bees
will forage in both cold and warm weather.
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Wild cherry flowers are much smaller and have
less nectar.
The same type of cost–benefit analysis showed
that the bee would have to visit 60 wild cherry
flowers per minute in cold weather to get enough
nectar to equal the foraging cost.
Thus, the bumblebees only forage on cherry
flowers in warm weather.
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In what ways might schooling behavior
and pairing behavior be advantageous for
the individuals involved?
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Schooling behavior can be advantageous
in several ways:
◦ A school has more sense organs than a single
individual and can detect predators sooner and
find resources more rapidly or efficiently.
◦ Pairing behavior could have several
advantages—one being that in male–female
pairs, each individual is assured of a mate.