Mammals

The Tell-Tale Hair

Mammals use hair for protection, concealment, waterproofing,
buoyancy, behavioral signaling, sensory function, and thermal
insulation and to maintain a high, constant body temperature in
all climates

Other Unique Mammalian Traits

middle ear bones
mammary glands
diaphragm
placenta
teeth

Highly Developed Nervous System
Evolution from Synapsids

?

Origin and Evolution of Mammals

Skull structures, especially teeth

Therapsids

upright limbs positioned beneath the body rather
than on the sides as in lizards and
reptiles.
Body changes in the skull and mandibular adductor muscles
allowing a variety of herbivores and carnivores to form

Cynodonts

evolved features that supported an active lifestyle and higher
metabolic rates.
Enhanced jaw musculature
Secondary bony
Important to mammal evolution
because it allows young to breathe
while suckling.

Early Mammals

Diphyodont

Jaw and Ear Bones
Hair and Mammary Glands
Diversification of Mammals
Continued Diversification

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Integument and Its Derivatives

Generally thicker
thin epidermis that is
protected by hair and a thicker
dermis?

Types of Hair

Hair follicle is an epidermal structure,
but lies deep in dermis of skin.

Functions of Hair
Periodic Molting
Horns and Antlers

?

Integumentary Glands

all derived from epidermis.
Sweat glands

Scent Glands

marking territory, warning, and defense signals.

Sebaceous Glands

are usually associated with hair follicles

Mammary Glands

?

DIVERSITY IN FEEDING

heterodont dentition?

Dentition

Mammals have four types of
dentition:
Incisors
Canines
Premolars
Molars

Sets of Teeth

have one deciduous set (temporary)
are Replaced by a permanent set
incisors, canines, and premolars are deciduous compared to molars?

Mammalian Feeding Specializations

Insectivores
short intestinal tract
pointed teeth

Herbivores

Herbivores?
have reduced or absent canines

Ruminants

large four-chambered stomach
and long tract for increased
fermentation and digestion:
rumen
re-chewed
reticulum
omasum
abomasum

Carnivores

High protein diet
cecum may be absent or reduced.

Omnivores

both plants and animals
Many carnivores will switch to fruits, berries, etc. when normal
food sources are scarce.
store food

FLIGHT

Bats are true flyers a niche not occupied by birds.
Gliding and flying may have evolved independently in
many mammalian groups.

Echolocation

ultrasonic frequencies
10 pulses per second, increasing to 200 pulses when prey is detected.

Bats and Their Food
Bat Diversity

?

HUMAN EVOLUTION

The Descent of Man, and Selection in Relation to Sex
few human fossils had been found but recent DNA and abundant fossil evidence has strongly vindicated
Darwin’s beliefs of common ancestry.

Primate Features

grasping fingers, flat fingernails, and forward-pointing eyes
small, nocturnal creatures
First group was the lemurs and lorises, which were traditionally called prosimians.
Second group was the tarsiers and apes, which were also called simians or anthropoids.

Simians

Three major simian groups:
• New World monkeys
• Old World monkeys
• The apes

Old World monkeys differ from New World monkeys in the lack a
grasping tail,

Apes

larger cerebrum, more dorsal scapula and the loss of tail.
Hominids include all apes
hominins are all hominid fossils placed closer to humans than to
chimpanzees.

The First Humans and the Origin of Bipedalism

Human jaws are less robust and have
smaller canines
foramen magnum
Shorter pelvic bones, S-shaped vertebral
column

Sahelanthropus tchadensis

ventral foramen magnum to indicate bipedal human.

Ardipithecus

long limbs, fingers, toes, and bipedal

Australopithecus

slightly larger than a chimpanzee.
sexually dimorphic

Other Australopithecines

?

Australopithecus sediba and Paranthropus robustus

skull crests, heavy jaws, and large back molars.

Genus Homo
Migration and Descendants
Modern Humans

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Homo neanderthalensis

Homo neanderthalensis replaced
H. heidelbergensis in Europe
while Homo sapiens moved into
Africa between 300,000 to
200,000 years ago.

H. neanderthalensis was more robust, with heavy muscles and
adapted to the cold and had similar brain size of modern humans

Homo sapiens

out of Africa about 200,000 years ago
Speech was possible for both H. sapiens and H. neanderthalensis