Mammals

1
Mammals
2

• Like birds, mammals produce body heat internally
  through metabolism.
• Mammals keep their body temperature high and
  nearly constant by controlling their metabolism
  and regulating the loss of heat through the body
  surface.
• Endothermy determines many of the capabilities of
  mammals
• Mammals can live in cold climates and be active.
• The rapid metabolism provides mammals with the
  energy to perform strenuous activities for long
  periods of time.

3
Completely Divided Heart

• Like birds, mammals have a 4 chambered heart with
  2 completely separated ventricles.
• Separate ventricles keep deoxygenated blood from
  diluting oxygenated blood and allow more
  efficient pumping of blood through both circuits
  of the circulatory system.

4

• The structure of a mammalian heart helps to
  ensure the efficient flow of blood throughout the
  body.
• The heart has 2 atria and 2 completely separated
  ventricles.

5

• Oxygenated blood and deoxygenated blood never
  mix.
• Recall that the heart of an amphibian or a
  reptile have only 1 ventricle.
• Mammals have such a high demand for oxygen that
  they cannot tolerate the dilution of oxygenated
  blood by deoxygenated blood.

6
Respiratory System

• The respiratory system of a mammal is adapted for
  efficient gas exchange.
• The lungs are large and contain millions of
  aveoli, the small chambers in which gas exchange
  occurs.

7

• Compared with the lung of a reptile, the lung of
  a mammal has a much larger surface area available
  for gas exchange.
• Another adaptation that contributes to the
  efficiency of respiration is the diaphragm, a
  sheet of muscle below the rib cage.
• Contraction of the diaphragm during
  inhalation helps draw air into the
  lungs.

8
Nervous system

• The brain of a mammal is about 15 times heavier
  than the brain of a similarly sized fish,
  amphibian, or reptile.
• Enlargement of the cerebrum accounts for the most
  of this size increase because it is the largest
  part of the brain.

9

• Most species are viviparous, in which females
  carry their young until full development
• Female secrete milk from mammary glands to feed
  newborn young.

10
Sexual Reproduction in Mammals
testis
ovary
meiosis
meiosis
sperms
eggs (ova)
fertilization
zygote
embryo
foetus
baby
11
Hair

• All mammals have hair.
• The main function of hair is to insulate the body
  against heat loss.
• Most mammals (except humans and whales) are
  covered with a thick coat of hair.
• Hair color also serves to camouflage a mammal
  from predators or a predator from being seen by
  its prey.

12

• Mammals have diverse, specialized teeth
• Molars
• Incisors
• Premolars
• canine

• Mammals have single lower jaw.
• Most species have 4 different types of teeth.

13

• There are 19 orders of mammals in the class
  Mammalia, in which 17 nourish unborn young in the
  placenta, egg laying mammals and marsupials.

14

• Oviparous or egg laying mammals
• Only 3 in existence
• Duck-billed platypus and two species of spiny
  anteaters called echidna.
• Not completely endothermic (their body
  temperature is lower and
  fluctuates more than other
  mammals).

Monotremata
15
Marsupials

• Include wombats, kangaroos, wallaroos, koalas,
  and opossums.
• Are born days or weeks after fertilization and
  fully develop in a pouch.
• They attach themselves to milk- secreting nipples
  nursing until they are mature enough to
  survive outside the pouch.

16
250 species of marsupial species exist in
Australia, New Guinea, Tasmania, And the Americas
Opossum
Tasmanian Devil
17

• 60 hundred million years ago, no placental
  mammals inhabited the continent
• Lacking in competition Australian marsupials
  underwent adapted radiation and eventually became
  adapted to all environments.

18
Placental Mammals

• Placental mammals carry unborn young in the
  uterus until young can survive in the wild.
• Oxygen and nutrients are transferred from
  mothers blood to babys blood.

• Placenta - allows diffusion of nutrients and
  oxygen into the fetus.
• Gestation Period - time when fetus is developing.

19
In placental mammals, offspring are born as
juveniles complete animals with the sex organs
present although not reproductively functional.
After several months or years, the sex organs
develop further to maturity and the animal
becomes sexually mature. Most female mammals are
only fertile during certain periods during their
estrous cycle, at which point they are ready to
mate. Individual male and female mammals meet and
carry out copulation. For most mammals, males and
females exchange sexual partners throughout their
adult lives.
20
The Placenta
oxygenated blood from mothers artery
deoxygenated blood to mothers vein
villus
umbilical vein
umbilical artery
21
Insectivora

• Consists of 400 species
• Includes shrews and moles

Shrew
Mole

• Small animals with high metabolic rate and found
  in North America, Europe, and Asia.
• Most have long pointed noses that enable them to
  grub for insects, worms, and invertebrates.
• Live on ground, trees, in water, and underground.

22
Rodentia

• Largest mammalian order having over 2,400
  species.
• 40 of placentals are rodents.
• Teeth grow continually and are used for gnawing.
• On every continent except for Antarctica.
• Includes squirrels, marmots, chipmunks, gophers,
  muskrats, mice, rats, and porcupines.

Chipmunk
23
Marmot
Porcupine
Squirrel
24
Rodents only have two incisors in each jaw that
grow as long as rodent lives and are used for
gnawing.
25
Lagomorpha

• Includes rabbits, hares, and small mountain
  mammals called pikas.
• Found worldwide.

Hare
Pika
26
Lagomorpha have a double row of incisors with
large front teeth backed with two smaller ones.
This is an adaptation for a herbivorous diet.
27
Edentata

• Made up of 30 living species including anteaters,
  armadillos, and sloths.
• The name edentate means without teeth.

28
Anteater
Sloths
29
Edentates have adaptations for insectivorous
diets, including a long, sticky tongue and clawed
front paws.
Anteater feeding at a termite mound. ?
30

• Sloths, on the other hand have continuously
  growing teeth as an adaptation for grinding
  plants.

31
Chiroptera

• Made up of over 900 species of bats.
• Live throughout the world except in polar
  environments.

32

• A bats wing is modified front limb which skin
  membrane between extremely long finger bones.
• Bats use thumbs for climbing, walking, or
  grasping.

33

• Most bats are active at night and have a special
  way to navigate using echolocation (bouncing off
  high-frequency sound waves).
• Frequency of returning sound waves with the size,
  distance, and rate of movement of different
  objects.

34

• Bats that use echolocation have small eyes and
  large ears.
• Feed on insects and have teeth specialized for
  such diets.

35

• Some feed on fruit and flower nectar and do not
  use echolocation.
• These bats are sometimes called flying foxes,
  have large eyes and keen sense of smell.

36
Cetacea and Sirenia

• 90 species of whales, dolphins, and porpoises are
  distributed worldwide.
• Cetaceans have fishlike bodies with forelimbs
  modified as flippers.

37

• Cetaceans divided into two groups which are
  toothed whales and baleen whales.
• Toothed whales include beaked whales, sperm
  whales, beluga whales, narwhals, killer whales,
  dolphins and porpoises.

38

• Cetaceans have over 100 teeth and prey on fish,
  squid, seals and whales

39

• Baleen whales lack teeth.
• Baleen-thin plates of finger-like material.
• Shrimp and other small invertebrates are the prey
  of the baleen whales.

40
The Order Sirenia is made up of four species of
manatees and dugongs.
41

• Front limbs are flippers for swimming.
• Sirenians lack hind legs but have flattened
  tails.

42
Carnivora

• 250 living species in carnivoria are distributed
  worldwide
• Most of the species mainly eat meat, which
  explains the name.
• About 34 species.

43

• Some members of this order such as bears feed
  extensively on plant material as well as meat, so
  they are called omnivores.
• Carnivores generally have long canine teeth,
  strong jaws, clawed toes.

44
Pinnipedia

• Pinnipedia are water dwelling carnivores and have
  streamlined bodies.

45
Artiodactyla and Perissodactyla

• Ungulates-hoofed mammals, classified into two
  orders Artiodactyla and Perissodactyla
• These two classes are herbivores.
• They have a storage chamber in their stomach
  called the rumen, undergoes double digestion.

46

• Ungulates with an even amount of toes make up the
  class Artiodactyla.
• Have a rumen and chew cud.
• Includes pigs, giraffes, sheep, cattle.

47

• Ungulates with an odd number of toes make up the
  class Perissodactyla.
• Includes horses, zebras, and rhinoceros.

48
Proboscidea

• Characterized by a boneless nose or proboscis.
• Elephants are the largest land dwellers alive
  today, weighing more than 6 tons.

49
It has modified incisors, called tusks, for
digging up roots and stripping bark from branches.
50
Primates

• 200 living species of primates classified as
  prosimians.
• Including lemurs, tarsiers, and lorises, or
  anthropods.

51

• A complex brain has enabled anthropoids to
  develop complex behaviors and to live in highly
  organized social groups.

52
Origin
Fossil skeletons show that early mammals had
large eye sockets, which may have meant that they
were active at night. Mammals did not compete
with dinosaurs for food, for they would feed on
insects.
53
Origin
Mammals were not abundant during the Mesozoic
era. Fossils of the first mammals are scarce thus
indicating that they were not as abundant. The
Cenozoic era is named the age of mammals, for
this is the time which mammals rapidly started to
increase.
54
Evolution

• Animals evolved from the group of reptiles
  called Therapids.
• Therapids have both reptilian and mammalian
  characteristics.
• Therapids have a jaw bone composed of 5 bones
  rather than a simple jaw bone.
• .

55
Evolution
Like mammals, Therapids have specialized teeth
adapted for specialized functions. The earliest
mammalian fossil found is from the early Mesozoic
era, 200 million years ago