Notes pertaining to the first exam have been archived. The notes that follow were written in a previous semester. As we cover material, the material and lecture dates will be updated.
Monday, Feb. 10
We
went over the first exam today. Make
sure you know the answer to questions that you missed. Some of these questions may be asked on the
next exam or on the final.
We started Chapt.
6 today, "An Overview of the Living Primates".
(Note that we are skipping chapter 5). The lecture dealt with the second
part of the chapter, primate taxonomy and a survey of living primates. We
will discuss primate characteristics next time. The taxonomic order, Primates,
contains two suborders: Prosimii and Anthropoidea. Members of the Prosimii
(prosimians) include lemurs (on the
Anthropoids have a number of characteristics which separate
them from the prosimians. These characteristics
were discussed in lecture and are in your text. In general, anthropoids
are smarter and rely less on smell than do prosimians.
The Anthropoidea include 3 superfamilies,
the New World Monkeys, the Old World Monkeys, and the Hominoidea.
Don't worry about formal taxonomy of the monkeys. We looked at slides of
New World Monkeys (some with prehensile tails). Many New World Monkeys
that live in the tropical rain forest are losing their natural habitat.
Old World Monkeys that we saw include the baboon and the Japanese snow monkey
(a macaque).
The superfamily Hominoidea includes three families: 1) Hylobatidae
(the lesser apes, including the gibbon and siamang)
2) Pongidae (the great apes including the orangutan
(genus Pongo), the gorilla, and the chimpanzee (genus
Pan). The genus Pan is today represented by two species, the common chimp
and the bonobo. Gorillas and chimps are African great
apes.
3) Hominidae (one living representative: us - Homo
sapiens).
Modern human taxonomy is as follows: Class: Mammalia
Order: Primates
Suborder: Anthropoidea (we are anthropoids)
Superfamily: Hominoidea
(we are hominoids)
Family: Hominidae
(we are hominids)
Genus: Homo
Species: sapiens
I started class by showing two adult gorilla skulls, a male and female. The male skull is much larger. This is an illustration of sexual dimorphism. In this case, males are larger than females. This is generally true for ground dwelling primates.
We then saw a brief CNN video dealing with "bush
meat". Chimp and gorilla meat was being sold to loggers. This
is a problem in central
The majority of today's lecture dealt with primate physical
characteristics. These are also extensively covered in Chapter 6 in your
text and will not be listed here. You should know that we share the same
dental pattern (incisors, canines, etc.) with all Old World anthropoids.
Many primate characteristics (flexible limb structure, grasping hands and feet,
good depth perception) serve to adapt primates to life in the trees.
Primates are largely arboreal (tree dwellers). Primates are slow to
mature, and they learn a lot while they grow up.
Finally, we started a video on a group of macaques (
We took up Chapt. 7 today. This chapter deals with primate behavior. One can study primate behavior in the lab, in the field, or in an enclosure situation. All these strategies have their advantages and disadvantages, but to gain an understanding of the "natural" behavior of a primate species, it is best to study these animals under natural conditions. A common approach of many field studies is to look for correlations between social structure and the habitat. For example, the large troop size of baboons can be explained by the abundance of resources and the need for protection.
Your text discusses the possible role of natural selection
in understanding primate behavior. Behavioral ecology tends to focus on
selection and ecological factors. Sociobiology also studies the possible
relationship between behavior and selection, but does not emphasize ecological
factors the way behavioral ecology does. At present, the role of
both genetics and environmental factors in primate behavior is not well
understood. It is clear though, that primate behavior is characterized by
more plasticity than the behavior of species governed largely by instinct.
Behavior common to primates includes the presence of
dominance hierarchies, various communication modes (autonomic responses,
gestures, facial expressions, vocalizations, postures, displays, and touch),
and aggressive behaviors. Primate groups typically have a home range and
a core area. Territories are defended areas, and they may be either the
same as a group's home range or core area. Affiliative behaviors are defined as friendly associations
between individuals. Non human primate affiliative
behaviors include hugging, kissing, sex, alliances, altruism, compassion,
grooming, and play.
We saw the
first part of a video which dealt with the behavior of chimpanzees in the
. Non human primate females (along with other mammals) have a period of estrus or sexual receptivity which is correlated with ovulation. Modern human females do not have this, but as a consequence modern humans have a greater potential for frequent sexual activity. Primates are K-selected, meaning that they have few offspring and give these lots of care. The opposite is to be r-selected, having lots of offspring but providing little care. From our point of view, clams are not good mothers (r-selected). Sexual selection is the result of competition for mates, and can lead to sexual dimorphism (in some primates like gorillas and baboons, males are larger than females). Interpreting this size difference (dimorphism) in terms of sexual selection, we are saying that large male gorillas have a higher fitness than smaller male gorillas.
Primatologists find that some
behaviors in non human primate species are learned and vary from group to
group. In chapter 7, these behaviors are termed cultural. Examples of
such learned behavior among chimpanzees include using sticks to fish for
termites, using leaves as sponges, using tooth picks, using stones as weapons,
and cracking nuts. Not all chimp groups perform these behaviors. That is,
there appear to be cultural differences between chimp groups. The video
we saw elaborated on some of these behaviors. It also showed chimps
hunting, killing, and eating a colobus monkey.
An homology is a shared trait inherited from a common
ancestor. Some behaviors seen in apes are also seen in humans and may be
interpreted as behavioral homologies. That means these behaviors may have
been present in a distant common ancestor. Examples of such behaviors
include tool use, communication ability, hunting/meat eating,
murder/cannibalism, and play with objects.
We discussed primate communication systems. A call
system is a closed system, meaning it is characterized by a limited
number of distinctive vocalizations, each one meaning a specific thing.
Many primates have call systems. Human language is an open system,
meaning that new or imaginary information can be transmitted. Apes do not
appear to use language in the wild. In the lab apes cannot be taught to
speak, but they can be taught sign language. Thus, apes have the
potential for language under natural conditions. One assumes that the
common ancestor of apes and humans had this potential as well. In
general, the differences between humans and other primates appears to be more a
matter of degree than of kind. This is what is meant when we say
that humans are part of an evolutionary continuum.
Monday, Feb. 24
We
started class
with a video “The Urban Gorilla” which included segments on
orphaned baby gorillas in
Chapter 8 begins with a discussion of biological classification, and we discussed a number of terms. Similarities between organisms are either homologies (based on descent from a common ancestor) or analogies (independently derived - generally based on function). Homoplasy is the name of the process leading to the development of analogies. The term "primitive", when applied to biological traits, means ancestral traits. The term "derived" (modified) refers to characters that have changed from the ancestral (primitive) condition. Cladistics is an approach to classification based on derived characteristics. This approach emphasizes closeness of the evolutionary relationship between two forms. A diagram showing these relationships is a cladogram. A phylogenic tree also shows evolutionary relationships, but includes ancestors and a time dimension.
Wednesday,
Feb. 26
We continued with Chapter 8, this time looking at evolution of mammals and then primates. Two concepts which are important in understanding macroevolution (long term evolution) are ecological niche and adaptive radiation. Mammals are characterized by larger brains than reptiles, giving birth to live young (viviparous), heterodont dentition, and they maintain a constant body temperature (endothermic). Major mamalian groups consist of the monotremes (egg laying mammals), the marsupials (pouched mammals), and the placental mammals. Along with many other forms, primates are placental mammals. Mammals underwent an adaptive radiation some 65 million years ago with the extinction of the dinosaurs. The mass extinctions at this time opened up many ecological niches.
Primates adapted to an arboreal niche. Little is know about Paleocene primates, but by the Eocene primates that bear some resemblance to prosimians appear in the fossil record. During the early Eocene, North America, Europe, and Asia were all connected, so some of the same species are distributed in these areas. Toward the end of the Eocene, some 40 million years ago, we see the emergence of early anthropoids. Two famous Oligocene anthropoids are Apidium and Aegyptopithecus. The latter has 32 teeth like all later Old World anthropoids. During the Miocene (22.5 - 5 million) the superfamily Hominoidea undergoes an adaptive radiation. Apes are widespread in the jungles stretching from Africa through the Middle East into Southeast Asia. Forms with names like Proconsul in Africa, Drypoithecus in Europe, and Sivapithecus in Asia abound. Sivapithecus is probably ancestral to the modern orangutans.
Friday,
Feb 28
We continued chapter 8 with a discussion of two models of evolutionary change, gradualism and punctuated equilibrium. Punctuated equilibrium argues that the evolutionary record is marked by long periods of stasis (stability) and then periods of rapid change, while gradualism argues that evolutionary change proceeds slowly and constantly. Your instructor sees either model as potentially appropriate depending on the specific case. Paleospecies are species defined from the fossil record. Often it is difficult to know whether two fossils should be classified as belonging to the same species. Are the differences observed intraspecific (that is, differnces based on individual variation, age, or sex) or are they interspecific, that is the result of differences between species.
Chapter 9 deals with paleoanthropology. The text focuses on Olduvai Gorge in East Africa as an important early hominid locality and uses Olduvai to illustrate some of the methods used by paleoanthropologists. Dating of material is accomplished in a number of ways. Stratigraphy is a relative dating technique used by geologists. Rock layers (once sediment) that are lower down were laid down earlier than rock strata higher up in an exposure. Potasium-argon is used at Olduvai and other East Africa sites to date volcanic ash. The amount of argon gas trapped in the rock (as a result of the decay of a radioactive isotope of potassium) is measured to give a date. Finally, biostratigraphy is a dating method which paleontologists use. The same type of fossil in strata at two different localities suggests that these strata are roughly contemporary. Fossils of animals that have undergone lots of evolutionary change are used in this method. We began a Nova video, In Search of Human Origins.
Monday,
March 3,
In studying a fossil locality, it is
necessary not only to date it, but to reconstruct the ecology. Reconstruction
of the former ecology (the paleoecology) necessitates
using information from paleontology (the study of fossils), palynology
(the study of pollen), geomorphology (geological history) and taphonomy. Taphonomists
study bones and how they came to be deposited at a particular place. In
addition to dating a fossil locality and reconstructing the paleoecology,
paleoanthropologists also study archaeological
sites. At Olduvai, butchering localities,
quarry localities, and localities used for multiple purposes have all been indentified by archaeologists. However, these are
dated long after the intitial appearance of
hominids. Early hominids appear as early as 4.5 million years ago, while
the earliest stone tools are only about 2.5 million years ago. We saw more of In Search of Human Origins.
Wednesday, March 5
In the latter part of the Miocene geological epoch ( c. 12 - 5 million years ago), the climate in
Friday,
March 7
Review class for exam 2 on Monday (chapters 6-9).