22Mammalia

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INTRODUCTION
▢ Study: Study of mammals is called Mammology.
▢ Origin: Mammals originated from the reptiles in the Triassic period of Mesozoic era.
▢ Dominance: Mammals are the dominated animals of Coenozoic, so this era is known as 'age of mammals'.
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GENERAL CHARACTERS
▢ Body Covering: Mammals are hair-clad, mostly terrestrial tetrapod vertebrates.
▢ Hair Composition: Hairs of mammals are made up of α-keratin.
▢ Mammary Glands: Most important character of mammals is the presence of Mammary glands (Modified sweat glands).
▢ Diaphragm: Presence of a muscular diaphragm separating thoracic cavity from abdominal cavity.
▢ Body Division:
❖ Parts:
  1. Head
  2. Neck
  3. Trunk
  4. Tail
▢ Limbs:
❖ Number: 2 pairs
❖ Structure: Pentadactyl each with five or few digits.
❖ Adaptation: Limbs adapted for walking, running, climbing, burrowing, swimming or flying.
❖ Exception: Hindlimbs are absent in aquatic Cetaceans and Sirenians.
▢ Exoskeleton:
❖ Components:
  1. Hairs
  2. Spines
  3. Scales
  4. Claws
  5. Nails
  6. Hooves
  7. Horns
  8. Bony dermal plates
▢ Skull: Dicondylic with two occipital condyles (also in Amphibia).
▢ Lower Jaw: Each half with a single dentary bone.
▢ Vertebra: Flat centrum called amphiplatyan or acoelous.
▢ Cervical Vertebrae: Presence of seven cervical vertebrae.
▢ Pectoral Girdle: Coracoid is vestigial.
▢ Ribs: 12 pairs of ribs (also 12 pairs of cranial nerves).
▢ Cloaca: Absent (except in Monotremes).
▢ Skin Glands:
❖ Types:
  1. Sweat gland
  2. Sebaceous glands
▢ Digestive System:
❖ Teeth: Heterodont, thecodont and diphyodont.
▢ Respiration System:
❖ Lungs: Respiration by lungs (pulmonary), glottis protected by a fleshy and cartilaginous epiglottis.
❖ Larynx: With vocal cords.
▢ Circulation System:
❖ Heart: Completely 4-chambered (also in birds and crocodiles).
❖ Sinus Venosus: Absent.
❖ Aortic Arch: Only left aortic (systemic) arch persists in adult.
❖ Renal Portal System: Absent.
❖ Erythrocytes:
  1. Small
  2. Circular
  3. Non-nucleated
▢ Excretion System:
❖ Kidneys: Metanephric.
❖ Ureters: Open into a muscular urinary bladder.
❖ Excretion Type: Ureotelic.
▢ Nervous System:
❖ Brain: Highly developed with corpus callosum connecting cerebral hemispheres.
❖ Cranial Nerves: 12 pairs.
▢ Ear:
❖ External Ear: With ear pinna.
❖ Middle Ear: With three ear ossicles: Malleus, Incus, and Stapes.
▢ Reproduction:
❖ Sexes: Separate
❖ Testes: Mostly in scrotal sacs for sperm development.
❖ Ovary: Contains Graafian follicles.
❖ Eggs:
  1. Small
  2. Microlecithal
  3. Homolecithal
  4. Acleidoic
❖ Reproductive Type: Viviparous, except egg-laying monotremes.
❖ Foetal Nourishment: Through placenta
❖ Extraembryonic Membranes: Amnion, chorion and allantois present (amniota).
❖ Parental Care: Greatly developed.
❖ Placenta Formation: By chorio-allantois.
▢ Intelligence: Mammals are the most intelligent animals among vertebrates.
▢ Body Temperature: Constant, warm-blooded (homoiothermous), average temperature 38°C.
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CLASSIFICATION
▢ Sub-class: Protheria:
❖ Characteristics:
  1. Primitive mammals
  2. Egg-laying mammals (Oviparous)
  3. Reptile-like mammals (Cloaca present)
  4. Confined to Australian region
  5. Young fed on milk from mammary glands without nipples
  6. Body temperature low (25-28°C)
  7. Connecting link between reptiles and mammals
❖ Order: Monotremata:
◉ Features:
  1. Mammals with single opening or Cloaca
  2. No external ear pinna
  3. Testes abdominal
  4. Penis conducts only sperms
  5. Uterus and Vagina absent
◉ Examples:
◈ Echidna (Tachyglossus)/ Spiny anteater:
◈ Ornithorhynchus / Duckbilled platypus:
■ Habitat: Aquatic, found in rivers.
■ Mammary Glands: Functional in both male and female.
■ Poisonous: Only poisonous mammal.
▢ Sub-class: Theria:
❖ Infra-class: Metatheria (Pouched mammals):
◉ Characteristics:
  1. Young born in very immature state
  2. Complete development in abdominal pouch or marsupium
  3. Corpus callosum absent
  4. Epipubic bone present
  5. No allantoic placenta
  6. Teeth one set, monophyodont
  7. Most primitive placental mammal is Shrew
◉ Order: Marsupials:
◈ Examples:
■ Macropus (Kangaroo):
● Locomotion: Saltatorial
■ Didelphis (Opossum):
● Habitat: Tree-dwelling
❖ Infra-class: Eutheria:
◉ Orders:
    ■ Order: Insectivora: Smallest and most primitive eutherians.
    ■ Order: Dermaptera: Gliding mammals with patagium.
    ■ Order: Chiroptera/ Bats:
    1. Nocturnal
    2. True flying mammals
    3. Capable of Echolocation, a type of radar system
    ■ Order: Edentata: Teeth absent or reduced to molars, without enamel.
    ■ Order: Pholidota:
    1. Body covered with large overlapping horny scales
    2. No teeth
    3. Tongue: Long and Protusible
    4. Eats ants
    ■ Order: Rodentia:
    1. Largest order of mammals in number of species
    2. Small gnawing mammals
    3. Each jaw with one pair of long rootless chisel-like incisors growing throughout life
    4. No canines
    ■ Order: Lagomorpha:
    1. Herbivorous with a second pair of upper incisors
    2. No canines
    3. Rabbit eats its own faeces
    ■ Order: Carnivora:
    ● Fissipedia (Terrestrial carnivores):
    1. Predatory flesh-eating mammals
    2. Examples: Dog, Cat, Lion, Tiger, Cheetah, Otter, Mongoose, Bear
    ● Pinnipedia (Marine carnivores):
    1. Stream-lined body
    2. Reduced tail
    3. Limbs modified into flippers
    4. Examples: Walrus, Seal, Sea-lion
    ■ Order: Cetacea:
    ● Characteristics:
    1. Aquatic mammals
    2. Breathe by Lungs
    3. Blubber or Subcutaneous fat present for heat conservation
    4. Skin glands absent
    5. Forelimbs modified into paddle-like flippers
    6. No hindlimbs
    7. No external ears
    8. Testes abdominal
    9. Hairs only on snout
    10. Nostrils on the top of the head
    11. Teeth often lost
    12. Eyes very small
    13. Bones spongy
    14. Mostly gregarious and Carnivorous
    ● Examples:
    ⟣ Balaenoptera musculus (Blue Whale):
    1. Largest animal ever lived
    2. Length: 35 metres
    3. Weight: 150 ton
    4. Feeds on plankton in arctic and antarctic waters
    5. Milk squirted to baby by muscular contractions
    ⟣ Others:
    1. Orcinus (Killer whale)
    2. Physeter (Sperm Whale)
    3. Delphinus (Common Dolphin)
    4. Platanista (Ganges Dolphin)
    5. Phocaena (Porpoise)
    ■ Order: Sirenia:
    ● Characteristics:
    1. Herbivorous aquatic mammals
    2. Paddle-like forelimbs
    3. No hindlimbs
    4. No external ears, no pinna
    5. Blubber present
    6. Testes abdominal
    ● Examples:
    1. Rhytina - Sea cow
    2. Trichechus - Manatee
    3. Halicore - Dugong
    4. Manatus australis - Sea cow (has six cervical vertebrae)
    ■ Order: Tubulidentata:
    ● Characteristics:
    1. Tubular mouth
    2. Tongue slender protusible
    3. No incisor or canines
    4. Limbs clawed for digging ant and termite nests
    ● Example: Orycteropus (Aardvark or Cape anteater of South Africa)
    ■ Order: Proboscidea:
    ● Characteristics:
    1. Largest land living animals
    2. Hairless skin (pachyderm)
    3. Nose and upper lip modified into proboscis
    4. Two upper incisors modified as tusks (Ivory obtained from tusks)
    5. Hairless skin is an adaptation for hot climate
    6. Mammoths and Mastodons were extinct elephants
    ■ Order: Hyracoidea:
    ● Characteristics:
    1. Small, guinea-pig like mammals distantly related to elephants
    2. Snout, ears and legs short
    3. 4 toes on front foot, 3 on hindfoot
    4. Commonly called 'African conies'
    ■ Order: Perissodactyla:
    ● Characteristics:
    1. Odd-toed hoofed animals, incisors present in both jaws
    2. Stomach simple
    3. Mule: Hybrid between male ass (jack) and female horse (mare)
    4. Hinny: Hybrid between male horse (stallion) and female ass
    ■ Order: Artiodactyla:
    ● Characteristics:
    1. Even-toed hoofed animals, incisors and canines in upper jaw usually absent
    2. Stomach 4-chambered
    3. All except pig ruminate or chew their cud
    4. Many with antlers or horns
    5. Term 'bovine' associated with Artiodactyla
    6. Hippopotamus: 'Horse of the river'
    7. Camels: 'Ships of the desert'
    ■ Order: Primates:
    ● Characteristics:
    1. Highest development of brain, most intelligent mammals
    2. Mostly arboreal
    3. First digit usually opposable for grasping
    4. Eyes typically large and turned forward
    5. Includes: Lemurs, Loris, Tarsiers, Monkeys, Apes, and Man
❖ Feet of Mammals:
◉ Plantigrade:
◈ Description: With five digits (toes), entire sole rests on the ground.
◈ Example: Man
◉ Digitigrade:
◈ Description: With four digits, heel raised, walks on digits.
◈ Example: Cat
◉ Unguligrade:
◈ Description: Most specialized, with only one digit (third), walks on the hoof (homologous to toe nails).
◈ Example: Horse
Q1.
The study of mammals is called
Q2.
Mammals originated from reptiles during
Q3.
Cenozoic era is known as the
Q4.
The most important character of mammals is the presence of
Q5.
Hairs of mammals are made up of
Q6.
Mammary glands are modified
Q7.
The skin of mammals is rich in
Q8.
Epiglottis in mammals protects
Q9.
The muscular diaphragm in mammals separates
Q10.
Mammalian skull is
Q11.
Mammalian vertebrae are generally
Q12.
The usual number of cervical vertebrae in mammals is
Q13.
Which mammal has six cervical vertebrae?
Q14.
Ant bear has how many cervical vertebrae?
Q15.
Three-toed sloth has how many cervical vertebrae?
Q16.
Mammals usually have how many pairs of ribs?
Q17.
Cloaca is absent in mammals except
Q18.
Teeth of mammals are generally
Q19.
Respiration in mammals is
Q20.
The glottis of mammals is protected by
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Mammalian heart is
Q22.
In adult mammals, the aortic arch that persists is
Q23.
Renal portal system in mammals is
Q24.
Mammalian RBCs are generally
Q25.
Mammalian RBCs are nucleated in
Q26.
Kidneys of mammals are
Q27.
Mammals are generally
Q28.
The structure connecting the two cerebral hemispheres in mammals is
Q29.
External ear with ear pinna is found in
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Middle ear of mammals contains
Q31.
The three ear ossicles of mammals are
Q32.
Mammalian eggs are generally
Q33.
All mammals are viviparous except
Q34.
Fertilization in viviparous mammals is
Q35.
Foetus in mammals receives nourishment through
Q36.
Placenta in mammals is formed by
Q37.
The ovary of mammals contains
Q38.
Mammals are homeothermic animals with average body temperature about
Q39.
Mammals are classified into two subclasses
Q40.
Theria is further divided into
Q41.
Prototherians are
Q42.
Example of Prototheria is
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Metatherians are commonly called
Q44.
Example of Metatheria is
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The most distinguishing feature of eutherian mammals is
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The most primitive placental mammal is
Q47.
Chiroptera includes
Q48.
Bats are nocturnal true flying mammals capable of
Q49.
Desmodus is a
Q50.
The largest order of mammals in number of species is
Q51.
Rodents are characterized by
Q52.
Lagomorpha includes
Q53.
Aquatic mammals that breathe by lungs belong to
Q54.
Blubber in cetaceans helps mainly in
Q55.
The largest animal ever lived is
Q56.
Proboscidea includes
Q57.
Ivory is obtained from
Q58.
Primates include
Q59.
The characteristic feature of primates is