evolution -my seminar

7/28/2019 Evolution -My Seminar

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Evolution

By Ranjitha .s

Dept of orthodontics


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Evolution is a process of change over a long

period.

It refers to the formation & development of life

on earth.

The idea that all living things evolved fromsimple organisms & changed through the ages

to produce millions of species.


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Era period Epoch Time First appearance of

Cainozoic

QuaternaryHolocene 1-2 million years ago Man

Pleistocene

Tertiary

Pliocene

70 million years ago

Anthropoid

Apes

primates

Miocene

Oligocene

Eocene

Palaeocene

Mesozoic

Cretaceous 120 million yearsago

200 million years

ago

Modernmammals

Early

mammals

Jurassic

Triassic

palaezoic

Permian

500 million yearsago

Reptiles

Amphibians

Fishes

Carboniferous

Devonian

Silurian

Ordovician


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Charles Darwin

On the Origin o f Species(1859)

First to link biological diversity to evolution

The Descen t o f Man, and Select ion in Relation

to Sex(1871)

Described human evolution

Saw aesthetic factors (looks) as sexual

attractors

Thomas Huxley

Evidence as to Mans Place in Nature(1863)

First book to describe human evolution

These scientists wrote about human evolution

before human fossil evidence was ever discovered


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FOSSIL EVIDENCEFOR EVOLUTION

Paleontology

Study of prehistoric life of all forms, typically using

fossils

Paleoanthropology

Study of prehistoric human life (and human ancestry),

typically using fossils

Mary and Louis Leakey Lifetimes dedicated to finding fossil evidence of human

ancestors in Africa

Olduvai Gorge

The Cradle of Mankind

Great Rift Valley in eastern Africa (Tanzania)

Erosion reveals layers of datable artifacts, bones, and fossils

going back 2,000,000 years


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Lamark

In 1809 Jean-Baptiste Lamarkehypothesized that simple

organisms emerge

spontaneously and evolve to

greater complexity.

Lamarks hypothesis about

acquired characteristics was

disproved by Weisman, who

concluded that changes in an

individual during a lifetime do

not affect its offspring.

3 principles to his theory:1. Organisms constantly strive to

improve themselves.

2. Most used body structures

develop and unused waste

away.3. A structure is modified by use

or disuse, the modification is

inherited to the offspring.

(Inheritance of acquired

characteristics.)


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HOMINID EVOLUTION

Hominids= great apes

Chimpanzees, gorillas, humans, and orangutans

Numerous intermediary fossils have been found

But scientists disagree on which are human ancestors and

which are evolutionary dead ends

Homo erectus

Homo sapiensneanderthalensis

Homo sapiens

Homo habilis


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Homo habi l is

2.4 to 1.4 million years ago

Fossils found in southern and eastern Africa

Used simple bone and stone tools Nicknamed handy man


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Homo erectus

1.8 million years ago to

70,000 years ago

First human ancestor to walk

fully uprightSome made complex stone

tools

ExamplePeking Man

Descendants were humans

and neanderthals


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NEANDERTHALS

Homo sapiens neanderthalensis

400,000 to 30,000 years ago

Lived in Europe and Asia

Archaeogenetics analysis of ancient and modern DNA

Comparison of human and Neanderthal DNA shows that

humans are not descended from Neanderthals Genes reveal that Neanderthals had red hair and fair skin

Fair skin developed to aid in the absorption of Vitamin D

from the sun in areas far north of the equator

Convergent evolution different species (such as humans

and Neanderthals) developing same characteristic(s)


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Homo neanderthalensis

H i


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Homo sapiens Homo (Latin) means

man or human

Sapiens (Latin) meanswise or intelligent

Homo sapiens = wiseman or wise human

Humans andNeanderthals bothconsidered sapiens

Anatomically modernhumans in Africa by

200,000 years ago Middle Paleolithic

period


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Comparative Hominid

Anatomy Anatomically, we are very similar to apes and

even to monkeys

But we are not identical: Humans are fully

bipedal, for example, while chimps are not. We have two arches in our foot; chimps do not.

Therefore we need to compare our ownanatomy with (a) other living primates and (b)fossil hominin forms.


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Skull Morphology: Chimp and Human

Note the following Larger brow ridge (supraorbital torus) of chimp compared to

human

Sloping forehead of chimp compared to human

More prognathous (jutting) jaw of chimp compared to human

Larger canine and gap (diastema) of chimp compared tohuman


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Structure of the Brain:

Diagram Frontal Lobe and Motor

Cortex:

Cognition: Thinking Ability

Motor Abilities

Parietal Lobe: Touch and

Taste

Temporal Lobe: Hearing

Occipital Lobe: Vision

Olfactory Bulb: Smell


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Human and Chimp Skulls Compared:

Brain Structure Compare the following

Chimps brain is muchsmaller (400cc vs. 1400cc)

It has reduced frontal lobe

It has no Brocas or

Wernickes area It does have Brodmanns

area 10, where calls mayoriginatebut no speech

It does have planumtemporale, where calls arereceivedbut not processedas language


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What This All Means

Our brains are larger than the chimps

We have a well-developed frontal lobe

We have well developed language areas:Brocasand Wernickes area

The motor strip is more well developed among

humans than among chimps


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Comparative Primate Anatomy:

Chewing Mechanism The next diagrams compare humandentition (structure

of teeth) with that of the chimps

Our overall dental arcade (arrangement of teeth) ismore rounded (arc-like) than the chimps

Chimpanzee have a more rectangular dental arcade,with the back teeth more parallel

Our teeth are much smaller than the chimps

We have small canines (jagged teeth)

Chimps have large canines, so large that they need agap (diastema) in the opposite jaw for them to fit


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Chimp and Human Dentition

Note the following:

Dental Arcade: Humans are arc-like; apes, parallel back

teeth

Canines and Diastema (gap): Apes have larger caninesand gaps in opposite jaw to fit them; humans do not


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Comparative Primate

Anatomy: Hand Structure Our fingers are straight; that of the chimps and other

apes are curved

We have a much longer thumb than do the apes

Importance: we are capable of a more precise grip thanthe apes

This implies that we can make finer tools than those

apes who can make and use tools


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Power and Precision Grip

Note the Following:

Power grip: Fingers andthumbs wrap around the

object Precision grip:

Forefingers and thumbhold the object

Importance: We can do

finer work compared tononhuman primates


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Bipedalism vs. Quadrupedalism Homo sapiens is the only mammal capable of

bipedalism, or the ability to stand and walk entirely ontwo feet.

Kangaroos stand on two feet, but they hop rather thanwalk and their forepaws are too small for any function.

Chimpanzees can walk on two feet, but not veryefficiently; they are closer to quadrupedalism, or theability to move around on four feet.


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Advantages of Bipedalism

Efficient locomotion

Freeing of hands for many purpouses:

Foraging and hunting/scavenging

Tool making and use

Care and provisioning of offspring

Increased height for viewing across landscape:

Tracking migrating herds

Predator avoidance


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Survival of the Fittest

Individuals that are best suited to anenvironment (adaptations that enable fitness)

survive and reproduce most successfully.

Over time, natural selection results in

changes in the inherited characteristics of a

population. These changes increase a

species fitness in its environment.


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Natural Selection

Natural Selection leads to organisms that are well

suited in particular environments.

It provides a scientific explanation for the historyof life on Earth as depicted in the fossil record and

similarities evident within the diversity of existing

organisms.


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A-- AGNATHA

B-- AUTOSTYLY

C-- AMPHYSTYLY

E,F-- HYOSTYLY

G-- HOLOSTYLY

Evolution of jaws


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Human and Chimpanzee In the next diagrams, the differences are significant to

biological capacity for culture

The area for brain of a chimp is more limited thanhuman brain because of its sloping forehead andtheheavy supraorbital torusthat covers much of the

forehead The chimp jaw has a prognathismabsent in humans

Chimps have largercanineteeth than humans; somuch so that there is a diastema(gap) for the

opposite canine to fit.


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EVOLUTIONIts the inheritance of the

heritable endowmentAlso defined as development of species

from earlier forms

Factors responsible for evolution are:-1. Genetic

2. Environmental


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SIMPLIFIED CLASSIFICATION

OF LIVING VERTEBRAES CLASS EXAMPLES

1. Agnatha Hagfishes,lampreys

2. Chondrichthyes Sharks,rays3. Osteichthyes Bony fishes

4. Amphibia Frogs,toads

5. Reptilia Lizards,crocodiles,snakes

6. Aves Birds

7. mammalia


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MAMMALIA

SUBCLASS

PROTHERIA METATHERIA EUTHERIA

e.g. platypus e.g.red kangaroo e.g,placental mammals

SUBCLASS

PROTHERIA METATHERIA EUTHERIA

e.g. platypus e.g.red kangaroo e.g,placental mammals

HUMAN EVOLUTION


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HUMAN EVOLUTION

Homo habi l is

2.4 to 1.4 million years ago

Fossils found in southern and eastern Africa

Used simple bone and stone tools

Nicknamed handy man

Homo erectus 1.8 million years ago to 70,000 years ago

First human ancestor to walk fully upright

Some made complex stone tools

ExamplePeking Man Descendants were humans and neanderthals


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Development of Conceptof Occlusion


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Development of Concepts of occlusion

It can be divided into

Fictional Period (prior to 1900)

Hypothetical Period (1900 to 1930)

Factual Period (1930 to present)


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Fict ional Period

Fuller Clark & Imrie talked of antagonism,meeting or gliding of teeth.

Talbotsaid its a historical event long since

passed in the decline of species, and possibleonly with an atavism throwback to our primitiveancestors.

The creation of a normal standard of occlusion ,a basis on which to compare departure fromnormal was lacking.


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Hypo thet ical Period

According to

Edward H. Angel

Mathew Cryer and Calvin Case

Lischer and Paul Simon

Milo Hellman

Ed d H A l


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Edward .H. Angle

In 1907Angle put a hypothesis that:

Occlusion is the basis of the science of orthodontia. The shapes of thecusps, crowns and roots , and even the very structural material of the teeth

and attachments are all designed for the purpose of making occlusion the one

grand object. we shall define occlusion as being normal relations of the

occlusal inclined planes of the teeth when the jaws are closed.

He described the illustration Old glory. which according

to him was ideal occlusion.

Angle stated Apollo Belverdos straight profile as ideal

The best eg. of his hypothesis was key of Occlusion

His hypothesis was suggestive of static occlusion


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Old GlorySkull

Apollo Belverdo


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Mathew Cryer and Calvin caseHe opposed Angle

How could one mix prognathic denture and

orthognathic profile?

How bimaxillary protrusion considered normal and

individual variation was not considered?

Then they were proved right by Turners illustrations

Cases concept of occlusion was static

Normal occlusion( it suits Apollos face better)


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Wheelers illustrations for normal

occlusion

PrognathicRetrognathic

Lischer And Paul Simon


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Lischer And Paul Simon

They tried to relate concept of occlusion by

relating teeth with rest of the face andcranium.

Lischer introduced mastication as requisite of

occlusion

Simon outlined the anthropometric approach

Milo HellmanHe showed racial variation in normal

occlusion

His study was also confined to static occlusion


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Factual Period

Dividing line b/w static and dynamic occlusion.

1931 Broadbent introduced Cephalometry.

With this advanced study tech the factual

period become functional period.By now 3 components of occlusion are set up1. Interdigitation of teeth

2. Status of controlling musculature

3. TMJ integrity


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Ardipithecus ramidus


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Australopithecus afarensis


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Australopithecus africanus


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Homo ergaster

Homo ergasteris one of the more problematic of species

designations

Each researcher that sees ergasteras valid sees different

specimens as belonging or not belonging

Most researchers see too little difference between ergaster

and erectus to form the basis of a species As a general rule of thumb, one can consider most

attributed ergasterspecimens to be early erectus

geographically confined to Africa

H t


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Homo ergaster


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Evo lut ion o f den t it ion

E l ti f D titi


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Evolution of Dentition

The mammalian dentition is 100, 000 million yrs old

The theories behind mammalian dentition are

Theory o f Concrescence derived by fusion of 2

or more primitive conical teeth. Theory of tr i tuberculy each tooth derived from

single reptilian tooth by secondary differentiation of

tubercule and root.

Theory o f mu lt i tuberculy derived from reductionand condensation of primitive multituberculate teeth.


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Non mammalian vertebratesPolyphyodonty(many dentitions)

In mammalsDiphyodonty (2 dentitions )

During growthof the animal increase in the

jaw size is associated with tooth size

Evolution of Dentition


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Dentition off ishes( Agnatha)

Eg - Sea lamprey & hag fishes

No true calcified teethArranged circumferentially

Horny teeth are also seen on the tongue

Chondr ichthyes (carrtilagenous fishes)


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Chondr ichthyes(carrtilagenous fishes)

Large no. of teeth are presentHomodont & polyphyodont

Teeth are covered by enameloid

lower jaw of shark


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Osteichthyes

(bony f ishes)

Haplodont conical shape

prehension

Polyphyodont

Teeth- vomer, palatine bones roof of the mouth

& tongue


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Amphib ia

Small, homodont, polyphyodont prehension

In the f rog small teeth on the upper jaw &

no teeth on the lower jaw


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Repti les

Homodont & polyphyodont Tend to be tricuspid or cone shaped

Egg teeth in embryos ofl izards & snakes

- used to break the shell

Dentition of mammals


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Dentition ofmammals

Heterodont ( 4 types )Restricted to 2 rows

Ability to masticate improves digestive

efficiency for high rate of metabolism


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Other features

TMJ articulation

Salivary glands

Prismatic enamel Diphyodonty

Secondary palate

Significant muscle development


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Dentition ofprother ia

Spiny ant eater edentulous

Duck b i l led platypu s 3 functional posterior teeth ineach jaw quadrant

No. of additional teeth develop but do not erupt but

rapidly resorb


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Metatheria

(Marsupials)

Eg. Red Kangroo

Dental formula 3/1, 0/0, 1/1, 4/4 .Feed on various plant.

Anterior teeth allow the food to be firmly grasped.

Marsupials have no. of dental features which

distinguish them from placental animals.


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Eutheria

Eg - hedge hog

Insectivoral

Incisors form a forcep like mechanism to pick preys.

Molars primitive tritubercular with sharp cusps

Suitable for crushing the shells of insects


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Rodent ia

Eg - rat

Heterogenous , Monophyodont

Continuously growing incisors

DF 1/1, 0/0, 0/0, 3/3

Rat & mice are widely used as experimental animals inDental sciences


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Carnivora

Incisors are small and arranged in line.

Enlarged canines offensive weapons

Incisors and canine tearing flesh


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Primates

Classified in to

-Pros imi i or Lemu r type

-Anthropoidea

Mainly herbivorous sometimesinsectivorous


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Pros im ii or Lemur type

DF 2/2, 1/1, 3/3, 3/3

incisors & canines are procumbent and form dental

comb.

mid line diastema .Upper canine is blade like

Upper molar tritubercular


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Anthropoidea(monkey, apes &Man)

Eg -Macaca monkey

DF 2/2, 1/1, 2/2, 3/3

Canines are long & prominent ( esp. in male )

Lateral diastema

Chimpanze


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Chimpanze

Resembles permanent teeth of man

Homosapiens


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Homosapiens

Modern man exis ted 100,000 yr s. ago

evolution -my seminar

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