living in trees?
Give examples of three different adaptations of limbs for locomotion in mammals, naming a mammal species, a structure and how it is adapted.
Instead of beaks, as in birds, mammals have different kinds of teeth. Incisors are specialized for cutting and nipping, premolars for shearing and grinding, and canines for piercing. Based on what you know of diets in mammals, name two mammal species, the kind of diet they eat, and one type of specialized teeth that would be best adapted for the diet.
In order to maintain a high constant body temperature, mammals need a nutritious and plentiful diet. What are some ways that mammals have adapted to meet their dietary requirements? How might size determine diet type, and why?
Further Reading / Supplemental Links
Unabridged Dictionary, Second Edition. Random House, New York, 1998.
http://en.wikipedia.org
http://kids.nationalgeographic.com/Animals
http://kids.yahoo.com/animals/mammals
http://nationalzoo.si.edu/Animals/SmallMammals/ForKids
http://www.ucmp.berkeley.edu/mammal/mammal.html
http://www.americazoo.com/goto/index/mammals/classification.htm
Vocabulary
estrus
A period of time when the female has maximum sexual receptivity.
harem
A group of females followed or accompanied by a fertile male; this male excludes other males access to the group.
mammary glands
Specialized sweat glands that produce milk.
marsupial
A type of mammal where the female has an abdominal pouch or skin fold within which are mammary glands and a place for raising the young.
monotremes
A group of mammals that lays eggs and feeds their young by “sweating” milk from patches on their bellies.
neocortex
Site of the cerebral cortex where most of higher brain functions occur.
placental
A type of mammal that has a placenta that nourishes the fetus and removes waste products.
vivipary
A reproductive system in most mammals and some reptiles and fish, in which living young are produced rather than eggs laid.
Points to Consider
Rats are considered to be highly intelligent as they can learn and perform new tasks, an ability that may be important when they first colonize a fresh habitat. Think about what kind of increased learning takes place with an increased brain size, as we will see in primates.
Think of some significant similarities between the mammals you read about in this lesson with those in the next lesson, particularly human beings.
What are some significant adaptations in the evolution of primates?
Lesson 14.3: Primates and Humans
Lesson Objectives
List and describe general traits of primates.
Summarize mating systems of primates.
Review the types of habitats primates can be found in.
Describe the three main groupings of primates.
List the traits of the hominids, their diet, reproduction and social system.
Check Your Understanding
What are general traits of mammals?
Describe the mating systems in mammals.
Introduction
If primates are mammals, what makes them seem so different? Primates, including humans, have several unique features only belonging to this group of mammals. Some of these adaptations are obvious, others not so obvious. Some of these features give primates advantages such that allow them to live in certain habitats, such as arboreal habitats (i.e. in trees). Other features have allowed them to adapt to complex and new social and cultural situations.
What are Primates?
The biological order Primates, mostly omnivorous (eating both plant and animal material) mammals, contains all the species commonly related to the lemurs (Figure below), monkeys (Figure below) and apes ((Figure below), the latter including humans ((Figure below). All primates have five fingers (pentadactyl), a generalized dental pattern, a primitive (nonspecialized) body plan and certain eye orbit characteristics, such as a postorbital bar (a bone, which runs around the eye socket). While an opposable thumb (the only digit on the hand able to turn back against the other four fingers, thereby refining the grip in order to hold objects) are a characteristic feature of this group, other orders, such as opossums, also have this feature.
Figure 14.21
A ring tailed lemur and twins. Lemurs belong to the prosimian group of primates.
Figure 14.22
One of the New World monkeys, a squirrel monkey.
Figure 14.23
Chimpanzees, pictured here, belong to the great apes, one of the groups of primates.
Figure 14.24
Reconstruction of a Neanderthal man, belonging to an extinct subspecies of , humans, who are part of the great apes. This subspecies lived in Europe and western and central Asia from about 100,000 40,000 B.C.
In intelligent mammals, such as primates, the cerebrum is larger relative to the rest of the brain. Indications of intelligence in primates include the ability to learn and complex behavioral flexibility, involving much social interaction, such as fighting and play.
Old World species (apes and some monkeys as seen in Figure below) tend to have significant sexual dimorphism, characterized mostly as size differences, with males being slightly more than twice as heavy as females. This dimorphism may be a result of a polygamous mating system where males attract and defend multiple females. New World species (including tamarins((Figure below) and marmosets(Figure below)) form pair bonds, which is a partnership between a mating pair that lasts at least one season. The pair cooperatively raise the young, and thus generally do not show significant size difference between the sexes.
Figure 14.25
An Old World monkey, a species of macaque, in Malaysia.
Figure 14.26
A New World species of monkey, a tamarin.
Figure 14.27
Another New World species of monkey, the common marmoset.
Non-human primates occur mostly in Central and South America, Africa and South Asia. Since primates evolved from arboreal animals, many modern species live mostly in trees. Other species are partially terrestrial, such as baboons (Figure below) and the Patas monkey. Only a few species are fully terrestrial, for example, the gelada and humans.
Figure 14.28
Baboons are partially terrestrial. Pictured here is a mother baboon and her young, in Tanzania.
Primates live in a diverse number of forested habitats, including rain forests, mangrove forests and mountain forests to altitudes of over 9,800 ft (3,000 m). The combination of opposable thumbs, short fingernails and long, inward-closing fingers has, in part, allowed some species to develop brachiation, locomotion of swinging by arms from one branch to another (Figure below). Another feature for climbing – expanded digits – as in tarsiers improves grasping (Figure below).
Figure 14.29
A gibbon shows how its limbs are modified for hanging from trees.
Figure 14.30
A species of tarsier, with expanded digits used for grasping branches.
A few species, such as the proboscis monkey, De Brazza’s monkey and Allen’s swamp monkey, the latter having small webbing between its fingers, are fine swimmers and occur in swamps and other aquatic habitats. Some species, such as the rhesus macaque and the Hanuman langur, can exploit human-altered environments and even live in cities.
Primate Classification
The primate order is divided informally into three main groupings: Prosimians, New and Old World Monkeys, and Apes. The prosimians constitute species whose bodies most closely resemble that of the early proto-primates, the earliest examples of primates (Figure below). Prosimians include the lemurs, located in Madagascar and to a lesser extent on the Comoro Islands, a group of islands in the Indian Ocean.
Figure 14.31
&nbs
p; One of the prosimians, a greater bush baby, Kenya.
The New World monkeys include the capuchin, howler and squirrel monkeys, who live exclusively in the Americas. The Old World monkeys and the apes (all except for humans, who inhabit the entire earth) inhabit Africa and southern and central Asia.
A few new species of primates are discovered each year and the evaluation of current populations varies as to the number of species; estimates over the last several years range from 350 to 405 species. In New World monkeys alone there are thought to be 128 species; of Old World monkeys, 135 species; of gibbons or “lesser apes,” 13 species and of humans and other great apes, seven species. But there is only one species of humans, which will be discussed below.
The Human Family
The great apes are the members of the biological family Hominidae, which includes seven species: humans, plus two species each of chimpanzees, gorillas and orangutans. Hominids are large, tailless primates, ranging in size from the pygmy chimpanzee, at 66-88 lbs (30-40 kg) in weight, to the gorilla, at 309-397 lbs (140-180 kg) (Figure below). In all species, the males are, on average, larger and stronger than the females, although the degree of sexual dimorphism varies greatly. Most living species are predominantly quadrupedal (four-footed), but all are able to use their hands for gathering food or nesting materials, and in some cases, for using tools, such as gorillas using sticks to gauge the depth of water and chimpanzees sharpening sticks to use as spears in hunting and using sticks to gather food and to “fish” for termites (Figure below).
Figure 14.32
A gorilla mother and baby, members of the great apes, at Volcans National Park, Rwanda. The gorilla is the largest of the hominids, weighing up to 309-397 lbs.
Figure 14.33
Tool using in a primate. A chimpanzee uses a stick to fish for termites, and then, pictured here, extracts the insects.
Most species are omnivorous (eat both plants and meat), but fruit is the preferred food among all but humans. In contrast, humans consume a large proportion of highly processed, low fiber foods, unusual proportions of grains and vertebrate meat, as well as a wide variety of other foodstuffs. Human teeth and jaws are markedly smaller for our size than those of other apes, perhaps as adaptations to eating cooked food. Humans may have been eating cooked food for a million years or more.
Gestation lasts 8-9 months and usually results in the birth of a single offspring. The young are born helpless, and thus they need parental care for long periods of time. Compared with most other mammals, great apes have a long adolescence and arenot fully mature until 8-13 years of age in most species (longer in humans). Females typically give birth only once every few years.
Gorillas and chimpanzees live in family groups of approximately five to ten individuals, although larger groups are sometimes observed. The groups include at least one dominant male, and females leave the group at maturity. Orangutans, however, are generally solitary. Human social structure is complex and highly variable. Can you think of any that are similar to those of other great apes?
Gorillas, chimpanzees and humans are classified together in the subfamily, the Hominidae, because they have more than 97% of their DNA in common, and exhibit a capacity for language or for simple culture beyond the family or band (a group of animals functioning together). Empathy is a controversial criterion that distinguishes the adult human from other hominids. Can you think of other human attributes that are unique to humans?
Lesson Summary
Primates are characterized by pentadactyly, a generalized dental pattern, a nonspecialized body plan and certain eye orbit features. Primates also have opposable thumbs and a large cerebrum relative to the rest of the brain.
Old World species tend to have significant sexual dimorphism, whereas New World species generally do not show significant sexual differences.
Many primates live in a variety of forested habitats, whereas others are partially terrestrial, and some, like the gelada and humans, are fully terrestrial. A few species are adapted for living in aquatic habitats.
There are three subgroups within the primates order: prosimians, including the lemurs; New World monkeys, and the Old World monkeys and the apes. There are estimated to be somewhere between 350 to 405 species of primates.
The great apes, consisting of seven species, are large, tailless primates, with sexual dimorphism. Most species are quadrupedal, but all are able to use their hands.
Most great apes are omnivorous, but fruit is the preferred food among all species but humans.
The great apes have unique reproductive and parental care features, especially when compared with most other mammals. There is a variety of social structure among the great apes.
Gorillas, chimpanzees and humans share some common characteristics.
Review Questions
What characteristics distinguish the biological order Primates?
What theory might explain why human teeth and jaws are markedly smaller for our size than those of other apes?
Opposable thumbs are a characteristic primate feature. List two ways in which non-human primates might use opposable thumbs.
Various hybrid monkeys are produced in captivity when different species or subspecies are housed together. In what situation in the wild would hybrids be produced?
Primates are thought to have developed several of their traits and habits initially while living in trees. What primate features might be an advantage in an arboreal habitat?
Gorillas and chimpanzees live in family groups of around five to 10 individuals. What are two possible strategies for feeding, when fruit is hard to find?
Further Reading / Supplemental Links
Unabridged Dictionary, Second Edition. Random House, New York, 1998.
http://kids.nationalgeographic.com/Animals
http://nationalzoo.si.edu/Animals/Primates
http://www.ucmp.berkeley.edu/mammal/eutheria/primates.html
http://pslc.ws/macrog/paul/lemurs.htm
http://www.wikipedia.org
Vocabulary
hybrid
The offspring of different species, genera, varieties or breeds.
omnivorous
Eating both plant and animal material.
pentadactyl
Having five fingers or toes.
quadrupedal
Four-footed
sexual dimorphism
A condition in which the males and females of a species are different in form and structure.
Points to Consider
Forward-facing color binocular vision was useful for human ancestors who swung by their arms from one branch to another. Recent studies suggest this type of vision was more useful in courtship. In what other groups of animals might vision also be important in courtship?
Thousands of primates are used every year around the world in scientific experiments because of their psychological and physiological similarity to humans. What kinds of behavioral experiments do you think might be conducted in primates?
Chapter 15: Behavior of Animals
Lesson 15.1: Understanding Animal Behavior
Lesson Objectives
Give examples of animal behavior.
Explain why animal behavior is important.
Describe innate behavior and how it evolves.
List ways that behavior can be learned.
Check Your Understanding
What is an animal?
Give examples of a wide variety of animals.
Do you have a dog or a cat? If you don’t, you probably know someone that does. Think about how these animals act. Does the dog bark when it’s excited? Does the cat purr when it’s happy? Do they both play with toys?
Examples of Animal Behavior
Barking, purring, and playing are just some of the ways that dogs and cats behave. These are examples of animal behavior. Animal behavior is any way that animals act, either alone or with other animals. Can you think of other examples of animal behavior? What about insects and birds? How do they b
ehave? The pictures in Figures below show some of the ways that these and other animals act. Look at the pictures and read about the behaviors.
All of the animals pictured in the Figures here are busy doing something important. Read about what each animal is doing. Think about why the animal is behaving that way. These are just a few of the many ways that animals behave.
Figure 15.1
This cat is stalking a mouse. It is a hunter by nature.
Figure 15.2
This spider is busy spinning a web. If you have ever walked into a spider web, you know how sticky a spider web can be. Why do spiders spin webs?
Figure 15.3
This mother dog is nursing her puppies. In what other ways do mother dogs care for their puppies?
Figure 15.4
This bird is using its beak to add more grass to its nest. What will the bird use its nest for?
Figure 15.5
This wasp is starting to build a nest. Have you seen nests like this on buildings where you live? Why do wasps build nests?
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