Classification of Primates Flashcards
1
Q
Classification
A
- All organisms are classified (grouped according to their similar features)
- The classification is a hierarchical system with organisms initially being divided into a few groups, with each of these groups being further subdivided.
- The groups that organisms are placed into are called taxa (singular: taxon)
- As we move dow the hierarchy, the taxa become smaller and more specialised with all organisms within in being more similar in their characteristics
- The 7 main taxanomic levels are: Kingdom, Phylum, Class, Order, Family, Genus, Species
2
Q
The classification of humans
A
- Kingdom: Anamalia
- Phylum: Chordata - hollow dorsal nerve cord, pharyngeal slits
- Subphylym: Vertebrata - notochord replaced by a backbone, hollow dorsal nerve enlarged to become a brain, postanal tail
- Class: Mammalia - body covered in hair, homeothermic, 4 chambered heart, development of young in a uterus, mammary glands
- Order: Primates - locomotion and posture, prehensile hands and feet, long developmental period
- Superfamily: Homininoidea = Hominoids including apes and humans (lesser apes, greater apes, humans)
- Family: Hominidae = Hominids include all modern and extinct orangutans, gorillas, chimpanzees and humans
- Sub Family: Homininae = hominines include all modern human and extinct chimpanzees and humans
- Tribe: Hominini = include all extinct human ancestors and modern humans
- Genus: Homo = some extinct ancestors fof humans and modern humans
- Species: sapiens = modern humans
3
Q
Binomial Nomenclature
A
- Its the scientific name for an organism
- It uses the generic name (the genus) and the specific name (species)
- Capital letter for the first letter of the genus and italics for the species
- For humans we are classified as Homo sapiens
4
Q
The Primate Order
A
The primate order can be further split into the:
- Prosimians - lemur, loris, bush baby
- Tarsiers
- Simiiformes (Anthropoids):
- New World Monkeys
- Old World Monkeys
- Hominoids:
- Lesser apes
- Greater apes
- Humans
- The prosimians are considered the least evolved and humans are the most evolved of the primate order
5
Q
Characteristics shared by all Primates 1
A
- Unspecialised Body
- Generalised and not suited for a specialised environment
- Unspecialised, Pentadactly limbs with opposable digits
- The non-specialised limbs
- 5 digid prehensile limbs with opposable first digit and friction
- Nails instead of claws
- Ensures digits can grip
- Protects sensitive skin
- 4 incisors
- Also have canines, premolars and molar teeth
6
Q
Characteristics shared by all Primates 2
A
- Forward facing eyes
- Allows 3 dimensional/stereoscopic vision
- Vision form each eye overlaps
- To compensate for reduced peripheral vision, we have highly moblie necks
- Rods and cones in our eyes. Enlarged visual centre of brain
- Poor sense of smell
- To allow improved stereoscopic vision, our snout is flatter and sense of smell is reduced
- Large Brain
- Well developed cerebral cortex involved with the higher functions including vision, memory, reasoning and manipulative abilities
- Allows primates to cope with a changing environment
- Complex reproductive system and behaviours
- These is a rhythmical sexual cycle, not restricted to seasons
- Usually single offspring at a time
- Long period of growth and maturation
- Increased parental care
7
Q
Evolutionary Trends in Primates -
A
- The characteristics that were previously described vary within the primate order
- Characteristics change from the less highly evolved species (loris) to the most highly developed species (humans)
- The features that demonstraet such an evolutionary trend within the order include:
- Digits
- Olfactory/Optical shift
- Gestation and parental care
- Brain size
- Dentition
8
Q
Digits
A
- The degree of opposability of the first digit increases across the primate order with humans having the most opposable thumbs
- This is aided by a lengthening of the thumb compared to the other digits and the presence of a saddle joint
- This increased opposability helps to improve the contact between the thumb and index finger which permits the use of the precision grip allowing increased object manipulation e.g. moving pencil when writing
- The opposability of the big toe in humans has been lost as an adaption to bipedalism. The other primates have it for climbing trees.*
- -* All primates are capable of the power grip (prehensile digits)
- This involves the use of large muscles located in the forearm that are joined by the fingers by tendons stretching over the wrist
- Another trend is the increased mobility of the digits and the ability to move each digit independently of each other
- More highly evolved primate species have nails instead of claws
- This increases the ability to grasp as claws prevent digits from touching effectively
- The more primitive primates (some lemurs and aye-ayes) still retain claws on some digits
9
Q
Olfactory Shift
A
- There is a decreased dependence on the reliance of smell as we move across the primate order
- The prosimians have a greater dependence on olfaction and will mark territory using urine and scent glands
- These primates have a result, a larger snout and a larger olfactory region in the brain
- As we move along the order there is less reliance on smell and a greater reliance on vision
- This results in a reduced snout size and a flattening of the face
10
Q
Optical Shift
A
- With the change in the face shape we see the eye sockets/eyes becoming more forward facing
- This allows greater stereoscopic vision (more overlap between the two eyes) which enables a greater perception of depth and distance. An essential trait for survival in an arboreal lifestlye needing to judge distance between trees.
- With the greater dependence on vision there is a larger optic region in the occipital lobe of the brain to interpret this input
- Another change that develops is a more mobile beck to allow the head to turn easily to compensate for the decreased field of view that occurs with the increase in stereoscopic vision
- The Lesser primates (loris, tarsier and some lemurs) are nocturnal
- Their eyes are adapted to this by containing rods only in the retina (detect low levels of light)
- As we move through the order, primates become diurnal (awake during the day)
- Their eyes now contain cones as well as rods which allows for colour vision
11
Q
Brain size and Development
A
- Primate brains are very large for their body size
- As we move across the primate order the brain becomes bigger with a more devloped cerebral cortex (more convolutions/greater surface area)
- As the brain size has increased this has resulted in a larger cranium
- The more developed cerebral cortex is reflected in the increasing levels of complexity in behaviours, social interactions, memory, planning and reasoning seen across the primate order. It also has a large area dedicated to controlling the muscles required for object manipulation and the processing of visual input
12
Q
Gestation
A
- As we move across the primate order there is an increase in the length of gestation and parental care
- Gestation = time between fertilization and birth
- The increased gestation is a result of a more developed and efficient placenta which allows nutrients to be delivered to the fetus
- The longer gestation allows more time for the brain to develop
13
Q
Parental Care/Dependence
A
- Primate babies are born relatively helpless compared to other animals and are reliant on their parents for care and protection
- Across the order we seen an increasing length of time in each of the stages of development (infant, juvenile, adult)
- This allows time for the young to learn the skills necessary to survive as well as the more complex social behaviours and techniques for obtaining food
- While the lesser primates will give birth to 2-3 offspring at a time, the more advances primates give birth to one offspring. They also have shorter reproductive periods in their life as sexual maturity is reached later
- There is often a large gap between offpspring as the more advanced primates spend more time nurturing their offspring
- This combined with the shorter reproductive period and single births limit the total number of offspring produced
- This increases the importance of the survival of the offspring to ensure the survival of the species, which is made possible by the increased parental care
14
Q
Dentition
A
- The trend is a decrease in the number of teeth as the species become more evolved
- Primitive mammals have 44 teeth wih a dental formula of 3.1.4.3
- Prosimians have 36 teeth with a dental formula of 2.1.3.3.
- Prosimians can also have a dental comb (in loris and lemur) for grooming
- Tarsiers and some new world monkeys have 34 teeth with their lower jaw containing only 2 incisors
- Most new world monkeys have the same dentition as the prosimians but the third molar is often small or absent
- Old world monkeys, apes and humans all have 32 teeth with a dental formula 2.1.2.3.
- Present in OWM and Apes are large pointed canines developed for displays to frighten predators and develop the social hierarchy. To accomodate the canines, they have spaces between the second incisor and canine of the upper jaw called a diastema
- The number of cusps on the molars increases across the primate order from 3-4 in prosimians, 4 in OWM and 5 in humans and apes
- Most primates have a U shaped dental arcade but humans have a parabolic or V shaped dental arcade
