Slide 1

Animal Kingdom Mammals

Slide 2

Slide 3

Phylum Chordata Evolutionary relationships

Slide 4

Phylum Chordata Review branch points in animal evolution. 1 st = presence of tissues: sponges have none 2 nd = symmetry: none, radial, bilateral 3 rd = type of body cavity a coelom 4 th = embryonic development Protostomes (blastopore becomes stomach): Mollusks & Arthropods. Deuterostomes (blastopore becomes anus): Echino- derms & Chordates. 5 th = notochord, pharyngeal slits, dorsal nerve cord, post-anal tail: Chordates Characteristics of chordates

Slide 5

Subphylum Vertebrata Characteristics of vertebrates (branch points, contd.) 6 th = is backbone present? yes, if vertebrate 7 th = type of egg water-borne (fish, amphibians) water-borne (fish, amphibians) amniotic egg (within a shell, adapted to dry land) 8 th = body covering scales (reptiles) feathers (birds) hair (mammals)

Slide 6

Subphylum Vertebrata Types of vertebrates Cartilaginous fish Jawless fish (eel) Jawless fish (eel) Amphibian Bony fish Birds Reptiles Mammal

Slide 7

Class Mammalia Mammals and reptiles share a common ancestral amniote, which evolved ~340 mya during the Carboniferous Period - something like Solenodonsaurus. Solenodonsaurus

Slide 8

Class Mammalia The common ancestor of reptiles and mammals began to diverge ~324 mya into sauropsids (which became reptiles) and synapsids (which became mammals). Sauropsid Synapsid The world during the Carboniferous Period, 324 mya. Synapsid fos- sils are first found in the area marked in yellow (today N.A. & W. Europe).

Slide 9

Class Mammalia Therapsids developed hair and lactation 275mya. They became the dominant land animal in the middle Permean Period, as Pangaea formed.

Slide 10

Class Mammalia Mammals evolved ~ 220 million years ago from therapsids. Eozostrodon was an early species. It lived during the late Triassic and the early Jurassic, about 210 million years ago. This mammal laid eggs, was warm-blooded.

Slide 11

Class Mammalia Mammals diversified after the Cretaceous extinctions, 65 mya. Up to 70% of terrestrial vertebrate species went extinct. Because so much biodiversity was lost, the recovery of life on Earth took signifi- cantly longer than after any other extinction event.

Slide 12

Class Mammalia Mammals diversified after the Cretaceous extinctions, 65 mya. A layer of rock with the element iridium is evidence for a meteor strike. Iridium is rare on earth but plentiful in meteors.

Slide 13

Class Mammalia Mammals diversified after the Cretaceous extinctions. There are ~ 4,500 living species of mammals. All mammalian mothers nourish their babies with milk, a balanced diet rich in fats, sugars, proteins, minerals, and vitamins, produced in the mammary glands. All mammals also have hair of keratin. Hair and a fat layer under the skin retain metabolic heat, contributing to endothermy in mammals. Most mammals are born rather than hatched. Fertilization is internal; embryo develops in the uterus*. A long period of parental care extends the time for offspring to learn survival skills by observing their parents.

Slide 14

Class Mammalia Evolution of the vertebrate heart Evolution of the vertebrate heart A fish heart has 2 chambers: a ventricle & an atrium Amphibians have 3 chambers: 2 atria & 1 ventricle. Reptiles have a sophisticated 3-chambered heart. Mammals & birds have a 4-chambered heart; the ventricle is divi- ded into separate right and left chambers so O 2 -rich blood is not diluted. Fish Amphibian Reptile Mammal

Slide 15

Class Mammalia Elimination of nitrogen wastes. Fish: release ammonia directly into the water very toxic but very soluble, and the ocean is huge. Reptiles & birds: release uric acid non-toxic paste; no water is wasted. Mammals: release urea less toxic than ammonia, water soluble (some water wasted).

Slide 16

Class Mammalia Modern mammals are split into three groups: Monotremes (egg-laying mammals) Marsupials (mammals with pouches) Eutherians (placental mammals)

Slide 17

Order Monotremata Monotremes once lived throughout Pangaea, which split into Laurasia and Gondwana ~200 mya. The placental animals evolved later, ~160 mya, in Laurasia. However, ~24 mya earlier, Antarctica and Australia had broken away and become isolated. Few placentals arrived there; thus, the old type animals had few competitors in Australia and survived. Earth, 160 mya

Slide 18

Order Monotremata Monotremes (playtpuses and echidnas) are the only living mammals that lay eggs. Monotremes have one hole for anus & reproduction. They have hair, and females produce milk. They are found only in Australia and New Guinea. Platypus Echidna

Slide 19

Order Monotremata Monotremes (playtpuses and echidnas) are the only living mammals that lay eggs. The platypus egg spends 28 days in the uterus then 10 day in the nest before hatching. After hatching, the baby licks milk from the mother's fur because mothers lack nipples.

Slide 20

Order Monotremata Monotremes (playtpuses and echidnas) are the only living mammals that lay eggs. The echidna egg leaves the cloaca* and enters a pouch where it hatches. Babies remain in the nest or ride on their mothers back. *Cloaca: one hole for anus & reproductive systems.

Slide 21

Subclass Marsupialia Marsupials include opossums, kangaroos, bandicoots, koalas. The oldest marsupial fossils date to 125 mya in China. Marsupials diversified during the Tertiary (65 to 2.6 mya) in S. America and Australia, while placental mammals radiated on the northern continents.

Slide 22

Subclass Marsupialia Marsupials include opossums, kangaroos, bandicoots, koalas. In Australia, marsupials have radiated and filled niches occupied by placental mammals elsewhere. Australia's isolation aided diversification and survival. Invasions of placental mammals from N. America began to reduce marsupials of S. America about 12 mya.

Slide 23

Subclass Marsupialia Marsupials include opossums, kangaroos, bandicoots, koalas. Babies are born prematurely, at 4 or 5 weeks. Most complete embryonic development within a pouch, the marsupium, which contains nipples for nursing.

Slide 24

Subclass Marsupialia Australia has the greatest diversity of marsupials, due to its previous isolation from modern animals.

Slide 25

Subclass Marsupialia Most S. American marsupials disappeared due to competition with placental mammals when the isthmus of Panama formed 3 mya (the Great American Interchange of species). Placentals migrated south and took over. The American opossum survived and migrated north.

Slide 26

Subclass Eutheria Genetic evidence places the split between marsupials and eutherians at ~ 125 mya. There are four main groups: Afrotheria (elephants, manatees), Edentata (anteaters, armadillos - all from South America, Bats, the core insectivores (shrews, moles), carnivores, artiodactyls (pigs, cows, camels, hippos), perissodactyls (horses, rhinoceroses), and cetaceans. Lagomorphs (rabbits), rodents, and primates).

Slide 27

Subclass Eutheria Eutherians are placental mammals babies receive nourish- ment full-term via a placenta in the uterus. Placenta: a disk-shaped organ, contains embryonic and maternal blood vessels to exchange food and wastes. (Marsupials do have a type of placenta that de- velops differently from that of eutherians; its a minor structure. There is also an early shell coat around the embryo.)

Slide 28

Order Cetacea Cetaceans evolved from mesonychids (right) a land animal ~50 mya.

Slide 29

Order Primates The earliest primates were probably tree dwellers. Includes monkeys, apes, and humans. Opposable thumb (toe) for hanging on tree branches. The overlapping (binocular) fields of vision of the two eyes enhance depth perception an advantage when jumping from branch to branch.

Slide 30

Order Rodentia Rodere means to gnaw in Latin. ~ 2,270 species largest mammal group; includes rats, mice, squirrels, and beavers. The order is characterized by a single pair of continuous- ly growing incisors in each of the upper and lower jaws which must be kept short by gnawing. Rats mouth. Remem- ber the owl pellet dis- section.

Slide 31

Order Rodentia Dissection of the rat Skin the rat. Note muscle groups. Open abdomen and remove ribcage. Open heart. Remove digestive system and measure.

Slide 32

Order Rodentia Dissection of the rat Observe reproductive system. Male Female