Bio Anthro 2

Front 1

Studies of several different species of primates show that the infants of these species need to have
a lot of contact with an adult, particularly their mother, in order to develop normal social behavior.
The researchers suggest that since humans are also primates and we share most of our genetic code
with other primates, we should expect human infants to have the same developmental need.
They are making an argument by, or based on

Back 1

homology

Front 2

Studies of numerous species of primates find that species in which individuals have many different
mates tend to have males that are significantly larger than females, while those that form
permanent mating pairs tend to have males and females of roughly the same size. Both
arrangements occur in several different branches of the primate phylogeny. Compared to the
differences seen in other primates, human males and females are similar in size. Researchers say
that this suggests that during the recent evolution of humans, our ancestors tended to form longterm
mating pairs.
They are making an argument by, or based on

Back 2

analogy

Front 3

Primates have some characteristics due to having descended from the common ancestors of all
mammals. List some of these characteristics of all mammals, which primates share: 6

Back 3

a. __lactation / mammary glands / nurse young
b. __live birth / viviparity
c. __long gestation
d. __hair
e. __warm bloodedness / homeothermy
f. __large brains for body size; flexible behavior

Front 4

List some characteristics related to manual dexterity that distinguish primates from other
mammals. 3

Back 4

a. __prehensile (grasping) hands and feet
b. __opposable big toe / thumb
c. __flat nails in place of claws; finger pads with fingerprints

Front 5

List some characteristics related to senses that distinguish primates from other mammals. 5

Back 5

a. __reduced sense of smell in diurnal species
b. __developed vision; large eyes
c. __eyes in front for binocular vision
d. __optic nerves split to both sides of brain for stereo vision
e. __trichromatic color vision in diurnal species

Front 6

List some characteristics related to behavior that distinguish primates from other mammals. 4

Back 6

a. __complex, flexible behavior
b. __brain relatively larger for body size
c. __long gestation; small litters; long juvenile dependency
d. __most live in social groups

Front 7

List some characteristics of strepsirrhines that distinguish them from most other primates? 5

Back 7

a. __many are nocturnal; greater emphasis on smell
b. __larger eyes; independently mobile ears; no postorbital plate
c. __sensory whiskers; less complex behavior
d. __digits act together; grooming claw; dental comb
e. __vertical clinging and leaping; smaller brain for body size

Front 8

You are watching a documentary in which primates in the wild are hanging from branches by their
tails. What word describes these tails, and what part of the world does the documentary depict?

Back 8

Prehensile tail
New World, or more specifically, Central and/or South America

Front 9

A documentary shows primates in the wild with very long arms and hook-like hands rapidly
moving through the jungle by swinging alternately by one arm, then the other. What is this form of
locomotion called? What part of the world does the documentary depict?

Back 9

Brachiation; Southeast Asia

Front 10

Baboons are a kind of ___________,
which is a kind of_________________,
which is a kind of_________________,
which is a kind of primate.

Back 10

_________cercopithecine__________________,
___________catarrhine_____________________,
____________haplorrhine__________________,

Front 11

What characteristics distinguish hominoids from other primates? 5

Back 11

a. __large size; no tail
b. _ large brain for body size
c. __Y-5 molars
d. arboreal adaptations: wide chest, scapulae on back, more mobile shoulders, elbows, wrists
e. __(from book: broader noses, broader palates)

Front 12

What is a human? List three main features that distinguish humans from other hominoids. 3

Back 12

a. __bipedal
b. __reduced canines
c. __big brain for body size; very complex behavior

Front 13

(1) Foods vary in how many calories they provide per pound or per unit of volume. What kind of
foods, in these terms, do smaller animals generally need, compared to larger animals? Give two
general kinds of such foods.

Back 13

smaller animals need food with more calories per pound or unit of volume (“high quality” foods)
examples of high-quality foods: insects, gum, flower nectar

Front 14

List two things that increase an animal’s caloric needs that affect males and females approximately
equally.

Back 14

activity and growing

Front 15

List two things that increase the caloric needs of females only.

Back 15

gestation and lactation (also carrying the young around)

Front 16

List the four general categories of primates based on their diets, and indicate what the major food
source is for each

Back 16

insectivores – insects
gummivores – plant gum
folivores – leaves, etc.
frugivores – fruit

Front 17

At the zoo, you see a relatively large haplorrhine primate with big, wide incisors. What do you
suspect is a major food for this primate?

Back 17

fruit

Front 18

Which kind of primate is likely to have a larger home range in the wild, a folivore or a frugivore?
Why?

Back 18

frugivores tend to need larger home ranges than folivores, because fruit tends to be dispersed in
patches that are widely separated in space, in a pattern that changes with the seasons, while edible
leaves are plentiful within a smaller area

Front 19

What is the difference between a home range and a territory?

Back 19

a territory is defended (it is exclusive; animals try to keep others of the same species out), while a
home range is not

Front 20

What are the two main benefits that territoriality might have?

Back 20

resource defense (better access to resources like food) or mate defense (better access to mates,
specifically excluding “foreign” males from mating with a female in the territory)

Front 21

What evidence suggests that mating might be a factor in territoriality?

Back 21

males are usually more territorial than females; a male’s reproductive success depends on mating
more than does a female’s. Since territoriality is often a specifically male behavior, it presumably
evolved in response to selection pressures that primarily affect males

Front 22

What are the two main categories of benefits of being with more other individuals?

Back 22

resource defense (better access to food by keeping foreign competitors of the same species away) and
protection from predation

Front 23

What are two costs of being with more other individuals?

Back 23

increased competition for food from group members, increased exposure to parasites and infectious
disease; risk to offspring from infanticidal males (which are more likely to be nearby if the species
lives in groups)

Front 24

Hamadryas baboons are diurnal, and are among the most terrestrial of primates.
a. What size of group, if any, would you expect them to generally live in? Why?
b. If you observe a female hamadryas baboon in the wild, how many males do you expect to be
nearby: none, one, several? Why?

Back 24

a. Large group; because diurnal, terrestrial primates are most at risk of predation, and large group size
tends to reduce that risk.
b. Several males; because large groups usually include multiple males, since a single male cannot keep
other males away from all of a large group. The better strategy is for several males to exclude all
others.

Front 25

Why does natural selection affect traits and behaviors related to getting food more in females that
in males?

Back 25

Females gestate, lactate, and for that reason, care for young by carrying them. This requires more
energy, hence more food, so access to food has a direct, strong affect on their reproductive success.
Males do not have these additional caloric needs, and may father many offspring even if they are not
well nourished, so getting food is less tightly tied to males’ reproductive success.

Front 26

Name and explain the two main kinds of competition for resources.

Back 26

contest competition: direct competition between individuals, in which one wins and the other loses
scramble competition: competition in which individuals perform independently, as in searching for
dispersed resources.

Front 27

Douc langurs are folivorous, but contrary to the predictions of the resource-defense theory of
sociality (which suggests that folivores would have little need to live in groups because they would
not gain from defending their food because it is so plentiful), they live in groups usually of 4-15,
with some groups up to 50 individuals.
a. What kind of competition would you expect to be common among these langurs? Why?

Back 27

a. scramble competition; because leaves are widely available, not concentrated in small patches, so
there is no need for contest competition to get leaves.

Front 28

b. Would you expect the females to have a clear dominance hierarchy? Why?

Back 28

b. No; because there would not be much contest competition for food, which is what leads to dominance
hierarchies among females.

Front 29

(1) List four ways in which having offspring is energetically costly for female primates.

Back 29

pregnancy, lactation, additional travel, carrying the infant, exposure to predation due to carrying and
watching the infant…

Front 30

Because of the issues listed above, what appears to be the most important limiting factor that
affects a female primate’s reproductive success, in contrast to a male’s?

Back 30

access to food (survival of offspring is also has a greater relative impact on females’ reproductive
success than on males’, but in practice, this seems to be a smaller factor than access to food)

Front 31

What is the biggest factor that affects a male primate’s reproductive success, in contrast to a
female’s?

Back 31

success in mating

Front 32

Why would natural selection favor females who were able to act submissive, that is, to lose out in
a confrontation with another female?

Back 32

It reduces a female’s chance of getting injured in a dominance fight

Front 33

Explain why there is an inherent conflict between the behavioral strategy of a primate mother and
the behavioral strategy of her infant.

Back 33

mother: strategy is to care for her infant just enough, then stop and have another, to maximize the
number of offspring she has
offspring: strategy is to maximize care from mother, without limit
So the mother will try to wean the infant, carry it less, etc. as it gets older, while the infant will insist
on nursing, make plaintive cries, etc. to keep the mother investing in it as long as possible

Front 34

What is sexual selection?

Back 34

Selection that favors physical or behavioral traits that increase male success in mating. These traits
are typically features of males, but they may also be behavioral traits in females, such as female
preferences for males with certain characteristics.

Front 35

What is intrasexual selection?

Back 35

Selection due to differences in success at mating due to interactions of individuals of the same sex

Front 36

Name and briefly explain a typical form of intrasexual selection.

Back 36

Male-male competition. Males compete directly (contest competition) for mating access to females

Front 37

Name and briefly explain a typical form of intersexual selection and its result. Give an example.

Back 37

Female choice. Females prefer to mate with males with some given trait, so that trait becomes
exaggerated in males, but not in females, because it would just waste already limited energy for them.
Examples: male peacock tails, male mandrills’s faces, male proboscis monkeys’s noses, etc.

Front 38

Explain why male baboons have larger canines and larger bodies, and females have smaller
canines and bodies.

Back 38

Large bodies and canines improve success in direct, contest competition with other males for access to
females (male-male competition). Since a male’s success at mating has a large effect on his
reproductive success, natural selection favors these features in males. They provide little benefit to
females, and require energy to grow and maintain. So selection tends to weed them out from females.

Front 39

Explain why monogamous (pair-bonded) primates such as gibbons and siamangs show little sexual
dimorphism.

Back 39

Since each male in pair-bonded species has relatively unimpeded access to one female and little
access to others, there is little male-male contest competition for mating, and all the males have
roughly the same success at mating. So there is little selection favoring larger males.

Front 40

Compared to other primates, how much sexual dimorphism is there in humans?

Back 40

Relatively little

Front 41

What does the previous answer suggest about human social organization in the past?

Back 41

Humans and our ancestors have probably been mostly monogamous for much of our recent evolution

Front 42

Explain how natural selection has apparently favored infanticide among some primates.

Back 42

In primates with single-male, multi-female groups, or multi-male, multi-female groups (in which there
are generally many fewer males than females)…
when a new male takes over the group,
or rises significantly in the dominance hierarchy from a lower rank where he could not mate much to
a higher rank where he can mate often…
he can increase his mating success by killing nursing infants.
Since lactation suppresses fertility, the mother of a killed infant goes into estrus,
and the new male can mate sooner than he would otherwise, increasing his reproductive successs.
There is little r.s. cost to the killer, because the infants are offspring of other males who mated with the
female before the infanticidal male arrived or approached the top of the dominance hierarchy.

Front 43

What is altruistic behavior (in the context of primate behavior)?

Back 43

behavior that has a cost to the actor and a benefit to another individual

Front 44

What fraction of their alleles are shared through descent by
a. a mother and her offspring?
b. two full siblings?
c. an individual and her full sibling’s offspring?

Back 44

a. 0.5
b. 0.5
c. 0.25

Front 45

What is inclusive fitness?

Back 45

The total number of copies of an individual’s alleles in the next generation, both directly (through
offspring), and indirectly (through relatives’ offspring) [technically expressed as the number of
“equivalent offspring”. For example, having one offspring and one sister who has one offspring
results in inclusive fitness of 1+0.5=1.5, since the sister’s offspring is equivalent to 0.5 of your own.]

Front 46

Explain how natural selection could lead to altruistic behavior, using the concepts of kin selection,
inclusive fitness, and Hamiliton’s rule.

Back 46

Altruistic behavior can be favored if the recipient is a relative of the actor, and the cost to the actor is
less than the benefit to the recipient, discounted by the fraction of alleles that they share by descent. In
that case, the behavior causes more of the actor’s alleles to get into the next generation, through the
additional offspring that the related recipient has due to the altruistic action… so the alleles that
encourage the altruistic behavior become more common.
written as Hamilton’s rule: rb > c (when this is true for some behavior, selection will favor it)
where r=coefficient of relatedness (or average of the coefficients if there are multiple recipients)
b=benefit to the recipient’s reproductive success (additional offspring as a result of the action)
c=cost to the actor’s reproductive success (lost offspring as a result of the action)