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BIRDS & MAMMALS. The platypus is a mosaic of mammalian, avian and reptilian traits. BIRDS & MAMMALS .

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birds mammals

BIRDS & MAMMALS

The platypus is a mosaic of mammalian, avian and reptilian traits.

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BIRDS & MAMMALS
  • EX: The duck-billed platypus has a flat, fury tail that resembles a mammal, the beaver; resembles turtles & birds in that it has a cloaca, an enlarged duct through which faeces, excretions from the kidneys & gametes pass.
  • Female platypus has mammary glands but lays shelled eggs (Monotreme-an egg laying mammal), as turtles and birds do.
  • Normally found in lagoons in Australia and Tasmania.
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BIRDS & MAMMALS

BIRDS

The ability to fly evolved in four groups,

Insects, pterosaurs (extinct), birds and bats

  • Birds apparently evolved from reptiles during the Jurassic.

1. The oldest known bird (Archaeopteryx) resembled reptiles in limb bones and other features. (avian traits, including feathers).

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BIRDS AND MAMMALS

Archaeopteryx

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2. Birds still resemble reptiles:

horny beaks, scaly legs, and

egg-laying.

3. There are greater than 9,000

named species of birds. The

smallest known birds weigh

2.25 gm (0.08 ounces), while

the largest bird, the ostrich, weighs

about 330 lbs.

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BIRDS & MAMMALS

4. The first birds evolved from reptiles during the Mesozoic era. The feathers were a highly

modified reptilian scale.

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BIRDS & MAMMALS
  • The body plan of birds is unique.

1. The body is covered with feathers –

helpful in flight and insulation.

Elastic sacs connected to the

lungs help dissipate excess heat

as they force warmed air out of

the body.

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BIRDS & MAMMALS

2. Construction meets the requirements

of flight: low weight and high power.

a. The bones are lightweight because

of air cavities within them. There is a

honey combed structure and an efficient

mode of respiration and circulation.

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BIRDS & MAMMALS

b. Powerful muscles are attached

at strategic places on the bones

for maximum leverage.

c. The heart is four-chambered,

and the lungs are highly

efficient because of their “flow-

through” design.

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BIRDS & MAMMALS

AVIAN

HEART

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BIRDS & MAMMALS

3. Flight in general and migratory

movements in particular are

amazing feats that birds seem to

accomplish with ease.

FLIGHT: PG 459 gives some explanation of the mechanics. Birds that are migratory move frequently from region to region in response to environmental rhythms. Seasonal change in day length is a cue, that influences internal timing mechanisms and biological clocks. Consequently, causes physiological and behavioral changes which induce birds to make round trips to different regions in different climates.

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BIRDS & MAMMALS

The Rise of Mammals

Range from: Kitti’s hog-nose bat 1.5 gm to 100 ton

whales

  • Mammalian Traits

1. Brain capacity is increased, allowing

more capacity for memory, learning, and

conscious thought.

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BIRDS & MAMMALS

2. Milk-secreting glands nourish the young.

3. Hair covers at least part of the

body (whales are an exception).

4. Dentition is extensive and special-

ized to meet dietary habits.

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Other amniotes typically swallow their prey whole, but most mammals secure, cut and sometimes chew their food before swallowing it. Four distinctive types of upper and lower teeth serve this purpose – incisors, canines, premolars, and molars.

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BIRDS & MAMMALS

The amniotes are a microphylum of tetrapod vertebrates that include the Synapsida (mammals) and Reptilia (reptiles and dinosaurs, including birds).

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BIRDS & MAMMALS

B. Mammalian Origins and Radiations

1. During the Triassic, divergence

from the small, hairless reptiles

called synapsids gave rise to the

therapsids. The early ancestors

of mammals.

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BIRDS & MAMMALS

2. By Jurassic times, mouse-sized

therians with jaws and hair had

evolved. This was a diverse group

of plant and meat eating mammals

that co-existed with the dinosaurs.

They began to flourish as the

dinosaurs began to vanish.

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BIRDS & MAMMALS

3. They (therians) had major changes

in the jaws, teeth and body form.

Their four limbs were positioned

upright under the body’s trunk.

It made it easier to walk upright.

Stability however had not yet

arrived. The cerebellum, the

region of the brain, concerned with

balance and spatial positioning

was only beginning to expand.

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BIRDS & MAMMALS

4. With the demise of the dinosaurs,

diverse adaptive zones opened up

for monotremes (egg-laying

mammals), marsupials (pouched

mammals), and eutherians

(placental mammals).

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BIRDS & MAMMALS

Monotremes – “Spiny Anteaters” (egg-laying)

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BIRDS & MAMMALS

Monotremes – Duck-billed Platypus

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Marsupials - kangaroos, koalas, wallabies, wombats, bandicoots, and opossums

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BIRDS & MAMMALS

Eutherians – placental mammals

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5. Egg laying mammals – Platypus/Spiny Anteater

Compared with the monotremes and marsupials – placental mammals had a competitive edge (i.e., higher metabolic rates, more precise regulation of body temperature, and a new way of nourishing their developing embryos).

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BIRDS & MAMMALS

Existing Mammals

Evolutionary distant, geographically isolated lineages often evolved in similar ways and in similar habitats and came to resemble each other in form and function.

  • The lineages of mammals are examples

of convergent evolution.

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BIRDS & MAMMALS

1. The platypus and spiny anteater,

which survive today in Australia,

differ from other mammals in

these ways:

a. They are practically toothless

b. Metabolic rates are lower

c. They lay eggs but suckle their

young.

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BIRDS & MAMMALS

2. The marsupials found in Australia

and in North America are distinc-

tive in that the young are born

tiny, blind, and hairless but find

their way to the mother’s pouch

where they are suckled and

finish their development. 260

species of marsupials are native

to Australia. The Tasmanian devil

the largest carnivorous marsupial.

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BIRDS & MAMMALS

3. The descendants of therians, placental mammals are found in virtually every aquatic and terrestrial environment.

a. The young are nourished within the mother’s uterus by the placenta – a composite of maternal and fetal tissue.

b. It is the organ of exchange of oxygen, nutrients

and wastes between the maternal blood and

the fetal blood.

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BIRDS & MAMMALS

We have journeyed about 570 million years, starting from tiny bag like animals to craniates, from jawless and jawed fishes having a backbone. Arriving at the end of the Devonian era we saw the emergence of tetrapods, that possessed skull bones, jaws, a back bone, lungs, walking on four limbs that evolved from fleshy lobed fins, to amniotes – reptiles and mammals to primates and then to humans.

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BIRDS & MAMMALS

Trends in Primate Evolution

A. Primates include a wide variety of

animals:

1. Prosimians (literally: before apes)

are small tree dwellers (arboreal)

that use their large eyes to advant-

age during night hunting.

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BIRDS & MAMMALS

Prosimians – Mongoose Lemur

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BIRDS & MAMMALS

2. Tarsiers (tarsioids) are small

primates with features inter-

mediate between prosimians and

anthropoids.

3. Anthropoids include monkeys, apes

and humans. Hominoids include apes and humans, where Hominid refers to human lineages only.

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BIRDS & MAMMALS

Tarsiers – Spectral Tarsier (S.E. Asia)

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BIRDS & MAMMALS

Anatomically and biochemically apes are closer to humans than monkeys, but chimps are most closely related.

GA Tech conducted a genetic analysis of approximately 63 million base pairs of DNA – 99.4%

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BIRDS & MAMMALS

Ape and Man – 98 -99% genetic similarity

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  • Primate evolution displays key trends:

Five features set primates apart from other mammals:

1. Less reliance on sense of smell and

more on enhanced daytime vision:

a. Early primates had an eye on each

side of the head.

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b. Later ones had forward-directed eyes resulting in better depth perception and increased ability to discern shape, movement in three

dimensions, color, and light intensity.

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BIRDS & MAMMALS
  • Apes - Forward-facing eyes for binocular vision (allowing depth perception) reliance on vision: reduced noses, (smaller, flattened), color vision
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2. Skeletal modification promoted

Bipedalism – upright walking

a. Bipedalism is possible because of

of skeletal reorganization in primates ancestral to humans. This freed the bonds for novel tasks.

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BIRDS & MAMMALS

b. A monkey skeleton is suitable for

a life of climbing, leaping, and

running along tree branches with

palms down.

c. An ape skeleton is suitable for

climbing and using the arms for

carrying some body weight; the

shoulder blades allow the arms to

swivel overhead.

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BIRDS & MAMMALS

d. Compared to the ape, humans

have a shorter, S-shaped and

somewhat flexible backbone.

Skeletal change favoring

bipedalism was a key innovation

that evolved in ancestors of

hominids.

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BIRDS & MAMMALS

3. Bone and muscle changed led to

refinements in hand movements.

4. Power grip and precision grip:

Early mammals spread their toes apart to support the body. Primates still spread fingers and toes. Tree-dwelling primates had modifications to handbones which allowed them to wrap their fingers around object.

Prehensile Movement

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BIRDS & MAMMALS

a. Opposable thumb and fingers

allowed more refined use of

the hand.

b. The precision and power grip

movements of the human hand

allowed for toolmaking.

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BIRDS & MAMMALS

4. Teeth became less specialized.

Jaws and teeth in early mammals

suitable for eating insects and fruits

and leaves later evolved long\ canines, in monkeys and apes and

humans to rip flesh.

5. changes in the brain became inter-

locked with changes in behavior and the

evolution of culture.

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BIRDS & MAMMALS

6. Brain, behavior, and culture:

is the sum of behavior patterns of

a social group, passed on to

generations through learning and

symbolic behavior.

a. Brain expansion and elaboration

produced a brain of increased mass

complexity, especially for thought,

language, and conscious movements.

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BIRDS & MAMMALS

b. Human brain development promo-

tion of new neural connections,

led to patterns of human behavior

known collectively as culture.

Maternal core became intense

and offspring started to acquire

longer periods of dependency and

learning.

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BIRDS & MAMMALS

From Early Primates to Hominids

A. Origins and Early divergences

1. The first primates that evolved

from mammals about 60 million

years ago (Paleocene) resembled

small rodents or tree shrews; they had

long snouts and were good foragers

on the forest floor.

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BIRDS & MAMMALS

2. By the Eocene, their descendants

were living in trees, had larger

brains, were active in the daytime,

and possessed better grasping

movements. Trees offered a

larger quantity of food and safety

from ground-dwelling predators.

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BIRDS & MAMMALS

3. By the time of the Oligocene,

tree-dwelling ancestors of monkeys

and apes, such as the anthropoid

Catopithecus, had emerged.

4. The first hominoids ape-like forms

appeared between 23 and 5 million

years ago (Miocene)

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BIRDS & MAMMALS

They evolved and spread through Asia, Africa and Europe. During this time too, shifts in land masses and ocean circulation caused long-terms change climate.

  • The First Hominids

1. Most of the earliest known

hominids lived in the East African

Rift Valley.

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BIRDS & MAMMALS

a. Cooler and drier weather in this

region of the world encouraged

the transition of hominids to

mixed woodlands and grasslands.

Food eventually became more

scarce. Hominoids had two choices,

move to adaptive zones or die.

Those who moved survived those

who did not more became extinct. The

lineage of the former became the first

hominids while the latter game rise to the

great apes.

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BIRDS & MAMMALS

b. The plasticity of early hominids

was the result of the capacity to

learn to adapt.

2. The first known hominids are designated australopiths (southern

apes).

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BIRDS & MAMMALS

a. The oldest has been designated

Australopithecus anamenis; other forms have been designated Australopithecus afarensis and A. africanus.

b. More robust muscular & heavily built

were A. boisei and A. robustus.

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BIRDS & MAMMALS

c. Relationship of these species is uncertain, but all shared several characteristics; improved dentition for grinding harder foods, upright walking, bipedalism (leaving footprints), and increased manual dexterity.

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Ape vs. Human Fossils

Ape-like featureHominid feature

Jaw shape rectangular dentation U-shaped dentation

Spine shape straight S-shaped

Posture knuckle-walked erect posture, bipedal

Pelvis elongated short

Supraorbital pronounced ridges not pronounced

Plane of face projected forward flat faced

Teeth larger, large canines smaller, smaller canines

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Emergence of Early Humans

Modern humans emerged from the traits seen in our tree-dwelling ancestors, relying more on the acute daytime vision than sense of smell. Manipulative skills increased. Bipedalism, omnivorous eating habits and increased brain complexity and behavior.

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A. Which traits characterized humans?

1. “Human” is mostly defined by the increased brain capacity which allows

analytical skills, complex social behavior, and technological innovation. These set us apart from apes.

2. The earliest human is designated Homo habilis, signifying “handy man”

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B. Homo habilis is associated with the first stone tools.

1. hominids began to use stone tools about 2.5 million years ago to get marrow out of bone & to scrape flesh from bones

2. “Manufactured” tools have been found at Olduvai Gorge.

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Emergence of Modern Humans

A. How did Homo erectus become Homo sapiens?

1. H. erectus migrated out of Africa into Europe and Asia.

2. Selection pressures triggered adaptive radiations resulting in physical changes as well as cultural shifts.

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Comparison between:

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a. Homo erectus had a longer, chinless face, thick-walled skull, heavy browridge but narrow- hipped and long-legged.

b. Homo erectus made advanced stone tools and used fired as they migrated out of Africa into Asia and Europe.

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B. By about 100,000 years ago, Homo sapiens had evolved from Homo erectus

1.Early H. sapiens had smaller teeth, a chin, thinner facial bones, larger brain, and rounder, higher skull.

2. Neanderthals were similar to modern humans but disappeared about 35,000 years ago.

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3. From about 40,000 years ago to today, human evolution has been cultural, not biological.

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