Transcript ECOLOGY SPRING 2009 - Florida International University

Birds (class Aves) are the most diverse of all terrestrial
vertebrates
-28 orders, 166 families, about 8600 species
 Arose about 150 MYA; Archaeopteryx
Birds still retain many reptilian and dinosaur traits
-Amniotic eggs and scales on legs; skeletal
elements, DNA
Two major traits distinguish them, however from
dinosaurs:
1. Feathers
-Provide lift for flight and conserve heat
2. Flight skeleton
-Bones are thin and hollow
-Many are fused (collarbone and
keeled breastbone)
3. Physiological adaptations—efficient respiratory
system.
Most paleontologists agree that birds are the direct
descendants of theropod dinosaurs
Archaeopteryx is the first known bird
-Had skull with teeth
-Feathers on wings and tail
-Forelimbs nearly identical to
those of theropods
The most ancient living birds appear to be the
flightless birds, such as ostrichs
The largest of the bird orders, Passeriformes,
appears to have evolved the latest
Many adaptations enabled birds to cope with the
heavy energy demands of flight
1. Efficient respiration
-Air passes all the way through lungs in a single
direction
2. Efficient circulation
-Muscles receive fully oxygenated blood
-Rapid heartbeat
3. Endothermy
-Body temperature (40-42oC) permits higher
metabolic rate
There are about 4500 species of mammals (class
Mammalia)
-Lowest number among 5 vertebrate classes
Mammals differ from other vertebrates in two
fundamental traits:
1. Hair
-Long, keratin-rich filaments that extend from hair
follicles
-Insulation, camouflage, sensory structure
2. Mammary glands
-Females possess mammary glands that secrete
milk
Other notable features of mammals include:
-Endothermy
-Depends on more efficient:
-Circulation – Four-chambered heart
-Respiration – Diaphragm
-Placenta
-Specialized organ that brings fetal and
maternal blood into close contact
The mammalian lineage
also gave rise to
several adaptations in
some groups:
1. Specialized teeth
-Different types of
teeth are highly
specialized to
match particular eating
habits
2. Digestion of plants
-Herbivorous mammals rely on mutualistic
partnerships with bacteria for cellulose
breakdown
3. Development of hooves and horns
-Hooves are specialized keratin pads
-Horns are bone surrounded by keratin
-Antlers are made of bone, not keratin
4. Flying mammals: Bats
-Bat wing is a leathery membrane of skin and muscle
stretched over 4 finger bones
-Bats navigate in
the dark by
echolocation
Fossil record shows that mammals evolved from
therapsids about 220 MYA
-First mammals were tiny, shrewlike, insect-eating,
tree-dwelling creatures
-May have been nocturnal
Mammals reached their maximum diversity in the
Tertiary period (65-2 MYA)
The last 15 million years saw a decline in the total
number of mammalian species
Prototheria (most primitive)
-Lay shelled eggs, oviparous
-One living group
-Monotremes
Theria
-Viviparous: Young are born alive
-Two living groups
-Marsupials and placental mammals
Only three living monotremes:
-Duck-billed platypus
-Echidna
-Have single opening,
cloaca for digestive and
reproductive tracts
Egg has chorion and amnion, but no shell
Embryo is nourished by abundant yolk
-After birth, it crawls into marsupial pouch
-Latches onto nipple & continues to develop
Examples:
-Kangaroo
-Opossum
Produce a true placenta that nourishes embryo
throughout its development
-Forms from both fetal and maternal tissue
Includes most living mammals
Primates are the mammals that gave rise to our own
species
-They evolved two features that allowed them to
succeed in an arboreal environment
1. Grasping fingers and toes
-First digit is opposable
2. Binocular vision
-Eyes are shifted toward the front of
the face
About 40 MYA, the earliest primates split into two
groups: prosimians and anthropoids
Prosimians
-Most are nocturnal
-Only a few survive:
-Lemurs, lorises and tarsiers
Anthropoids are diurnal
-Include monkeys, apes and humans
Almost 30 MYA, some anthropoids migrated to South
America
-Descendants called New World monkeys
-All are arboreal
-Grasp objects with long, prehensile tails
Anthropoids that remained in Africa gave rise to two lineages
-Old World monkeys
-Ground-dwelling or arboreal
-None have prehensile tails
-Hominoids
-Apes and humans
-Have larger brains than monkeys and lack tails
The taxonomic group “apes” is paraphyletic
-Living apes consist of gibbons, orangutans, gorillas
and chimpanzees
Hominids consist of humans and their direct
ancestors
-Common ancestor was more like a chimpanzee
than a gorilla
The common ancestor of apes and hominids is
thought to have been an arboreal climber
-Hominids became bipedal, walking upright
-Apes evolved knuckle-walking
Differences related to bipedal locomotion
1. Human vertebral column is more curved
2. Humans carry much of the body’s weight on the
lower limbs
3. Spinal cord exits the bottom of the skull.
4. Limbs have changed in proportion.
There are two major groups of hominids
-Genus Australopithecus
-7 species
-Older and smaller-brained
-Genus Homo
-3-7 species (depending how you count them)
Bipedalism seems to have evolved as
australopithecines left forests for grasslands
Did it follow or precede brain enlargement?
-African fossils demonstrate that bipedalism
extended back 4 MYA
-Substantial brain expansion, on the other hand, did
not appear until about 2 MYA
Therefore, upright walking came first
-However, why it evolved is still a matter of
controversy
The first humans (Genus Homo) evolved from
australopithecine ancestors about 2 MYA
-Thought to be Australopithecus afarensis
In the 1960s, hominid bones were found near stone
tools in Africa
-Early human was called Homo habilis
-It closely resembled Australopithecus, but had
larger brains
H. Hablis was replaced by Homo erectus
Homo erectus was a lot larger than H. habilis
-Had larger brain and more rounded jaw
-Able to talk
H. erectus became widespread in Africa
-Then migrated to Asia and Europe
H. erectus survived for over a million years
-Longer than any other human species
Modern humans first appeared in Africa about
600,000 years ago
-Three species are thought to have evolved
-Homo heidelbergensis (oldest)
-Homo neanderthalensis
-Homo sapiens
Some investigators lump all 3 into H. sapiens
H. heidelbergensis
-Coexisted with H. erectus in Africa
-Had larger brain & more advanced anatomy
H. neanderthalensis
-Appeared in Europe 130,000 years ago
-Were short, stocky and powerfully built
-Had massive skulls
Neanderthals made diverse tools
-Took care of sick and buried dead
-First evidence of belief in “life after death”
They abruptly disappeared about 34,000 years ago
-Replaced by fossils of H. sapiens called the CroMagnons
Out of Africa Hypothesis
Recent DNA analysis indicates that Cro-Magnons and
Neanderthals didn’t interbreed
-Neanderthals are our cousins, not our ancestors
Cro-Magnons had a complex social organization
-Thought to have full language capabilities
H. sapiens is the only surviving
hominid
-Best fossils are 90-100,000 years
old
Hallmarks of H. sapiens evolution
-Progressive increase in brain size
-Effective making and use of tools
-Refined and extended conceptual
thought
-Use of symbolic language
-Extensive cultural experience
Human beings differentiated in their traits as they
have spread throughout the world
All humans are capable of mating with one another
and producing fertile offspring
Some contemporary anthropologists divide people
into as many as 30 “races”
-Others only three: Caucasoid, Negroid, and
Oriental
Humans have relied on visual cues – primarily skin color – to
define races
However, groupings based on overall genetic similarity are
different from those based on skin color or other visual
features
Different groups of people have interbred during the
entire course of history
-This constant gene flow prevented the formation of
different human subspecies
Only 8% of genetic differences can be accounted for
by racial differences
-Therefore, human races do not reflect significant
patterns of underlying biological differentiation