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9.8 Option - The Human Story: 1. Classification

Syllabus reference (October 2002 version)
1.Humans have characteristics that can be used to classify them with other organisms	Students learn to: outline the general classification hierarchy from phylum to species   define the term species and outline criteria used to identify a species   outline features that classify humans as: mammal primate hominid hominin discuss the use of the terms hominin and hominid in terms of the arbitrary nature of classification systems   describe primate characteristics, including: hand/foot structure and function, including opposable thumb or toe skull shape and function brain size relative to body size arrangement of the vertebral column to the degree of upright stance vision, including degree of stereoscopic vision, colour vision reproductive features, including single live young and relatively long gestation parenting and group bonding describe primate characteristics in: prosimians new and old world monkeys apes humans	Students: identify data sources, gather, process and analyse information from secondary sources to illustrate the classification process by identifying features of humans that classifies them as: Animal Chordate Mammal Primate Hominid Homo Homo sapiens process information to summarise and analyse the similarities and differences between prosimians, monkeys, apes and humans   analyse information and use available evidence to identify technological advances and resulting new information that have changed scientists’ opinions about the classification of primates

Extract from Biology Stage 6 Syllabus (Amended October 2002). © Board of Studies, NSW

Prior learning: HSC module 9.3 (subsection 5).

Science Stages 4–5 syllabus: Outcomes 4.8 (content 4.8.2 a), Outcome 5.8 (content 5.8.3 a, b).

Background: Humans are primates. Humans therefore share many features with the other members of this group.

outline the general classification hierarchy from phylum to species

• The general classification hierarchy is phylum, class, order, family, genus and species. Within this hierarchy, phylum is the most general category, species is the most specific category.

define the term species and outline criteria used to identify a species

• A species can be defined as a group of actually or potentially interbreeding natural populations that is reproductively isolated from other groups.
   
• Because the system of classification is arbitrary and devised by humans there are exceptions. These exceptions are hybrids produced between species. Most hybrids are sterile and cannot reproduce, for example, a mule can only be produced by breeding a female horse with a male donkey. Others are produced by unnatural close associations between animals that would not normally occur, for example, zoo hybrids between lions and tigers. The third exception is the production of fertile hybrids that occurs between species, such as the crop, Triticale, which was formed by breeding wheat and rye.
   
• In general the criteria used to identify a species is if two organisms can breed together and form fertile offspring and they share a common gene pool, then they are considered to be the same species.

identify data sources, gather, process and analyse information from secondary sources to illustrate the classification process by identifying features of humans that classifies them as:

• Animal
• Chordate
• Mammal
• Primate
• Hominid
• Homo
• Homo sapiens

• Identify data sources i.e. more than one, such as a book, an article, an encyclopaedia or an Internet site.
   
• Gather a list of features of humans that classifies them for each of the named categories. Confirm and build your list by referring to more than one source.
   
• Process the information you gather by organising your information, such as in a table as shown in the incompleted table below, and looking for trends and patterns.
   
• Analyse the information, making generalisations

outline features that classify humans as:

• mammal
• primate
• hominid
• hominin

• The mammalian features of humans are: hair, mammary glands, three separate bones in the inner ear, four-chambered heart and a lower jaw consisting of one bone.
   
• The primate features of humans include: fingernails and toe-nails, an opposable thumb, stereoscopic (binocular) vision, a relatively large brain, a flattened face with a reduced sense of smell and forward facing eyes, ridged finger pads, two nipples and a prolonged period of care for the young.
   
• The hominid features of humans are: relatively large brain size and the lack of a tail.
   
• The hominin features of humans are: bipedal upright gait, arms shorter than legs, and a larger brain size relative to body size.

discuss the use of the terms hominin and hominid in terms of the arbitrary nature of classification systems

• Classification systems are designed to help sort out the millions of living organisms. They are designed for convenience and this leads to the arbitrary or subjective nature of classification systems. The use of the groups hominid and hominin is undergoing change, as new evidence becomes available from biochemical and genetic sources. Hominids used to be a group containing modern humans (Homo sapiens) and their close relatives such as other members of the Homo genus (eg. Homo neanderthalensis and Homo erectus) and members of the genera Paranthropus and Australopithecus. Recent evidence has shown that African apes including bonobos, chimpanzees and gorillas are genetically very similar to Homo sapiens and should be grouped with them as Hominids. To distinguish the group of animals that were once in the group hominids, the tribe grouping of hominin is now used to distinguish the African apes from the genera Homo, Paranthropus and Australopithecus.

An article dealing with hominin/hominid debate:

National Geographic Viewpoint: Is It Time to Revise the System of Scientific Naming? Lee R. Berger, National Geographic News, December 2001

describe primate characteristics including:

• hand/foot structure and function, including opposable thumb or toe
• skull shape and function
• brain size relative to body size
• arrangement of the vertebral column to the degree of upright stance
• vision, including degree of stereoscopic vision, colour vision
• reproductive features, including single live young and relatively long gestation
• parenting and group bonding

The features of primates are more like a collection of similarities including the following.

• Hand/foot structure: Primates have five flexible digits (pentadactyl limb). The toe and thumb are opposable. These enable objects to be grasped and manipulated. Primates have two different types of grip called the power grip and the precision grip. The power grip is used to grasp objects like branches while the precision grip is used for manipulation of fine objects and is best seen in humans. Most primates have nails instead of claws and have sensitive pads on the end of the fingers.
   
• Skull shape and function: Primates have an enlarged skull to protect the relatively large brain. Most primates have a flatter face with a shortened nose, this leads to better depth perception but poorer sense of smell.
   
• Brain size relative to body size: Primates have well developed brains and when compared to other animals of equal size have a larger relative brain size to body size.
   
• Arrangement of the vertebral column: Primates trend towards an upright stance, have an S-shaped spine and the foramen magnum is centred under the skull.
   
• Vision: Primates have large forward facing eyes. This gives a good view of overlap and stereoscopic vision is an important feature if you are jumping from branch to branch in a tree. Primates also have good colour vision, once again an important adaptation to finding fruit in trees, especially if you have a reduced sense of smell.
   
• Reproductive features: Primates have a long gestation period (length of pregnancy) and produce usually a single baby. Most primates have a restricted breeding period and two nipples.
   
• Parenting and group bonding: Primates are dependant for a long period of time. This allows a long learning time for the young to develop social skills that enable group living. Living in groups is a form of protection against predators and increases the chances of finding food. Many primate groups are well organised with a clear hierarchy of position.

Primates Overview Behavioral Sciences Department, Palomar College, San Marcos, California

process information to summarise and analyse the similarities and differences between prosimians, monkeys, apes and humans

• This is best done as an excursion to the zoo where you can examine members of the above groups. If you are unable to visit a zoo then use the Internet sites given below to process information.

  Chimpanzee Wikipedia. Scoll down to learn about up to date information on chimpanzee features.

  Gorillas, Physical Characteristics Busch Entertainment Corporation. Animals, SeaWorld/Busch Gardens . USA.

  Orangutans: Just Hangin' On , Nature, PBS

   

• Choose two members from each group. Process information by developing a table to summarise your observations in relation to the following information:
  • the shape of the face (elongated/rounded/flat)
  • position of the eyes (forward facing/ side facing)
  • description of fingers (claws, nails, opposable thumb/toe)
  • body stance (body erect/ body bent)
  • tail (present/absent/prehensile)
  • walk on four or two limbs
  • hindlimbs shorter/hindlimbs longer
  • nostrils facing down/facing forward
  • body covering.

  Remember to look for similarities and differences.

describe primate characteristics in

• prosimians
• new and old world monkeys
• apes
• humans

• Prosimians (before apes). Prosimians are a group of lower primates including lemurs, tarsiers, lorises and bushbabies. Their faces are often pointed and they have grasping hands and feet. They occur in small isolated groups and are generally endangered. They are small usually nocturnal, arboreal (active at night, live in trees) animals with forward facing eyes. Prosimians have a wet nose, called a rhinarium, which is an adaptation for the sense of smell.
   
  Summary of prosimian features:
  • small nocturnal arboreal primates
  • at least one digit with a claw instead of a nail
  • less opposable thumb than other primates
  • grooming claw as well as nails
  • more acute sense of smell than other primates
  • long snout with a rhinarium
  • eyes more on the side of the head than other primates
  • seasonal breeding.
     
  Prosimians have many characteristics that differ from other primates. The primate characteristics of this group include:
  • arboreal
  • presence of nails on at least one digit
  • opposable thumb but less than other primates
  • forward facing eyes but less than other primates
  
   
• New and old world monkeys. Monkeys are divided into new and old world monkeys. New world monkeys live in the Americas and old world monkeys come from Asia and Africa. They are usually larger than prosimians and are diurnal (active during the day). They are generally tree dwellers have a larger brain than prosimians and have full binocular vision. They do not have a rhinarium. Differences between new and old world monkeys are summarised in the table below:
   
  

  Feature	Old world monkey	New world monkey
  prehensile tail (able to grasp objects)	absent	present
  nostrils	pointing forward, shaped like tear drops, close together	pointing sideways, nostrils round and wide apart
  nose partition	narrow	wide
  cheek pouches	present	absent
  callosities (coloured area on the rump)	common	absent

  
   
  Examples of New World monkeys include tamarins, squirrel monkeys, spider monkeys, capuchins and howler monkeys. Examples of old world monkeys include baboons, macaques, mandrills and proboscis monkeys.
   
• Apes. Apes have no tails. Most are larger than monkeys and they have a larger brain relative to their body size. They rely on sight rather than smell and live in organised social groups. Apes include gibbons, orangutans, gorillas and chimpanzees.
   
  Summary of ape features:
  • forward facing eyes
  • more opposable digits
  • nails
  • good colour and stereoscopic vision
  • menstrual cycle
  • no tail
  • shoulders adapted for brachiation (swinging arm over arm)
  • large size.
  
   
• Humans. Humans are the only living members of the hominin group. They are large primates with an upright stance and bipedal locomotion. The big toe is not opposable and the knees are locking. The pelvis of humans is broad and barrel-shaped. The legs are longer than the arms and the thighbone angles inwards. Human feet are flat and humans live on the ground. The dental arch in gorillas is U-shaped while in humans it is parabolic.

analyse information and use available evidence to identify technological advances and resulting new information that have changed scientists’ opinions about the classification of primates

• Use available evidence on the classification of the apes and humans as a starting point in your study. Tarsiers also have had an interesting history of classification changes. Tree shrews were once included in the primate family but have now been removed.
   
• Analyse the information by identifying trends, patterns and relationships as well as contradictions in the information.

Some useful websites:

Methods of classifying Taxonomy: Classifying Life Dr John Kimbell, Massachusetts, USA.
Primate taxonomy Dr Bill Sellers, Faculty of Biological Sciences, University of Leeds, UK