Parental Care Parental care encompasses any action by
Parental Care • Parental care encompasses any action by a parent that improves the ability of its offspring to survive. • Among animals, mammals and birds provide the most extensive parental care. – Female mammals also lactate—they produce milk and use it to feed their offspring after birth. • Among large animals, the evolution of extensive parental care is hypothesized to be a major reason for the evolutionary success of mammals and birds. In both lineages, mothers produce relatively small numbers of large, high-quality offspring.
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© 2011 Pearson Education, Inc.
Chordata: Vertebrata – Hagfish and Lampreys • The 110 species in these two aquatic groups may belong to two independent lineages or to a single jawless vertebrate group. • Hagfish and lampreys are the only vertebrates that lack jaws, but they do have crania. • Hagfish lack a vertebral column, but lampreys have small pieces of cartilage along the length of their dorsal hollow nerve cord. • Hagfish are scavengers and predators; lampreys are ectoparasites. • Lampreys go through metamorphosis in their life cycle.
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Chordata: Vertebrata – Chondrichthyes • The 970 species of sharks, rays, and skates in this lineage are distinguished by their cartilaginous skeleton, the presence of jaws, and the existence of paired fins. • Most species are marine, though a few live in freshwater. • Most species are predators, although a few are suspension feeders. • Sharks use internal fertilization, and fertilized eggs may be shed into the water or retained until the young are hatched. Some sharks are viviparous, as are rays. Skates are oviparous.
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Chordata: Vertebrata – Actinopterygii • The 27, 000 species of ray-finned fishes have fins supported by long bony rods arranged in a ray pattern. • The actinopterygians are the most successful vertebrate lineage based on number of species, duration in the fossil record, and extent of habitats occupied. • The most important major lineage of ray-finned fishes, comprising about 96 percent of all living fish species, is the Teleostei.
Chordata: Vertebrata – Actinopterygii • Unlike chondricthyes, actinopterygians avoid sinking in the water with the aid of a gas-filled swim bladder. • Ray-finned fishes are major predators as well as the most important large herbivores in both marine and freshwater environments. • Most species are oviparous and use external fertilization. Some species exhibit parental care.
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Chordata: Vertebrata – Actinistia and Dipnoi • The coelacanths and lungfish are independent lineages but are often grouped together as lobe-finned fishes. • Lobe-finned fishes are common and diverse in the fossil record, but only eight species are alive today. • They represent an important link between the rayfinned fishes and the tetrapods. – Their fleshy lobe-shaped fins are supported by a linear arrangement of bones and muscles similar to those observed in tetrapods.
Chordata: Vertebrata – Actinistia and Dipnoi • Coelacanths live 150– 700 m below the ocean surface; lungfish occupy shallow ponds—if they dry out, lungfish can breathe air and survive until water returns. • Coelacanths prey on fish; lungfish are omnivorous, meaning that they eat algae and plant material as well as animals. • Some lungfish can use their fins to walk along pond bottoms. • Sexual reproduction is the rule, with fertilization internal in coelacanths and external in lungfish. – Coelacanths are ovoviviparous; lungfish lay eggs.
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Chordata: Vertebrata – Amphibia • The 5500 species of amphibians are the most ancient tetrapods. They are found throughout the world in ponds, lakes, or moist land. • Amphibians form three clades: 1. Frogs and toads. 2. Salamanders. 3. Caecilians. • In many species, gas exchange occurs exclusively or in part through their moist, mucus-covered skin.
Chordata: Vertebrata – Amphibia • Adult amphibians are carnivores and find their food on land, but many species must lay their eggs in water. • Most amphibians have four limbs; caecilians lack limbs and eyes. • Reproduction is sexual, breeding occurs in water, and larvae undergo a dramatic metamorphosis into land-dwelling adults. – Frogs are oviparous and have external fertilization. – Salamanders have internal fertilization; most are oviparous. – Caecilians have internal fertilization; many are viviparous.
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© 2011 Pearson Education, Inc.
© 2011 Pearson Education, Inc.
Chordata: Mammalia (Mammals) • Mammals are a monophyletic class with three lineages: Monotremata, Marsupiala, and Eutheria. • Three distinguishing characteristics of mammals are: 1. Insulating hair or fur. 2. Endothermy—they regulate their body temperatures with internally generated heat. 3. Mammary glands for lactation.
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Chordata: Mammalia – Monotremata • Monotremes are the most ancient group of mammals living today; the three living species, the platypus and two species of echidna, are found only in Australia. • They lay eggs and have low metabolic rates. • They have a leathery beak or bill; platypuses feed on small animals in streams and echidnas feed on ants, termites, and earthworms on land. • Platypuses lay their eggs in a burrow, echidnas keep their eggs in a pouch on their belly.
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Chordata: Mammalia – Marsupiala (Marsupials) • The 275 known species of marsupials live in Australia and the Americas. • Marsupial females have a placenta, but the young are born poorly developed after a short embryonic period and continue to develop while attached to their mother’s nipple, where they suck milk. – They stay attached to their mother until they grow large enough to move independently. • In many cases, convergent evolution has resulted in marsupial species that are extremely similar to placental species.
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Chordata: Mammalia – Eutheria • There about 4300 species of eutherians, or placental mammals, distributed worldwide. Eutherians are the most species-rich and morphologically diverse group of mammals. • There are 18 eutherian orders. • The size and structure of the teeth and the digestive tract correlate closely with the diet of placental mammals. • Their young are much better developed at birth than are those of marsupials. • Eutherians have internal fertilization and are viviparous.
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Chordata: Reptilia • The reptiles are a monophyletic group. They are one of the two major living lineages of amniotes, the other lineage consisting of today’s mammals. – The major feature distinguishing the reptilian and mammalian lineages is the number and placement of openings in the side of the skull, through which jaw muscles pass. • Reptiles are well-adapted for terrestrial life because of three distinguishing features: 1. Scales. 2. Well-developed lungs. 3. Amniotic eggs.
Chordata: Reptilia • Reptiles are represented by four major lineages: 1. 2. 3. 4. Lizards and snakes. Turtles. Crocodiles and alligators. Birds. • Except for birds, almost all of the reptiles living today are ectothermic, meaning that individuals do not use internally generated heat to regulate their body temperature. – Reptiles moderate their body temperature behaviorally.
Chordata: Reptilia – Lepidosauria • Most of the 7000 species of lizards and snakes are small reptiles with elongated bodies and scaly skin. • Most lizards have well-developed jointed legs, but snakes are limbless, although some species have vestigial limbs. • Small lizards tend to be predators, while large ones are often herbivorous; snakes are carnivores, some using modified teeth called fangs to inject poison into their prey. • Although most lizards and snakes lay eggs, many are ovoviviparous.
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Chordata: Reptilia – Tetsudinia • The 300 known species of turtles and tortoises inhabit freshwater, marine, and terrestrial environments throughout the world. • Turtles and tortoises (terrestrial turtles) are distinguished by a shell composed of bony plates. • Although they lack teeth, their jawbone and lower skull form a bony beak. • Most marine turtles are carnivorous while most tortoises are herbivorous. • All turtles are oviparous.
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Chordata: Reptilia – Crocodilia • Only 24 species of crocodile and alligator are known; most are tropical and live in freshwater or marine environments. • They have their eyes located on the top of the head and nostrils located at the top of their long snouts, adaptations that allow them to sit semi-submerged for extended periods. • All crocodilians are predators. • Although crocodilians are oviparous, parental care is extensive.
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Chordata: Reptilia – Aves • The fossil record provides conclusive evidence that birds descended from feathered dinosaurs. • All bird species have feathers, and most use them to fly. • The 9100 bird species alive today occupy virtually every habitat, including the open ocean. • Birds are the only endotherms within the Reptilia. • Most birds are omnivores, although many are predators. • Birds are oviparous but provide extensive parental care.
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Key Lineages: The Hominin Radiation • Humans occupy a tiny twig on the tree of life, but their origins have been studied extensively.
The Primates • The primate lineage consists of two main groups: – Prosimians (“before-monkeys”) • Includes lemurs from Madagascar, and tarsiers, pottos, and lorises from Africa and south Asia. • Most prosimians are small-bodied, arboreal, and nocturnal. – Anthropoids ("human-like") • Includes New World monkeys from Central and South America, Old World monkeys from Africa and Asia, gibbons from southeast Asia, and the Hominidae or great apes— orangutans, gorillas, chimpanzees, and humans.
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What Makes a Primate? • Primates have many defining characteristics: – Hands and feet for grasping. – Flattened nails on the fingers and toes instead of claws. – Relatively large brains. – Color vision. – Complex social behavior. – Extensive parental care of offspring. – Forward-facing eyes.
What Makes a Great Ape? • Great apes are also called hominids and are relatively large bodied with long arms, short legs, and no tail. • Hominids have distinct ways of walking: – Orangutans live primarily in the trees, but fist-walk when on the ground. – Gorillas and chimpanzees knuckle-walk. – Humans are the only great ape that is fully bipedal (“twofooted”), walking upright on two legs. Bipedalism is the synapomorphy that defines the hominins, the monophyletic group comprising Homo sapiens and more than a dozen extinct, bipedal relatives.
Fossil Humans • Hominins (humans and their extinct bipedal ancestors) can be organized into four general groups: 1. Australopithecus. 2. Paranthropus. 3. Early Homo. 4. Recent Homo.
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Fossil Humans • Australopithecus is composed of four species of small apes called gracile (“slender”) australopithecines. – Several lines of evidence support the hypothesis that the gracile australopithecines were bipedal. • Paranthropus is composed of bipedal robust australopithecines. – All three species had massive cheek teeth and jaws, very large cheekbones, and a sagittal crest—a flange of bone at the top of the skull. – This lineage is hypothesized to have become extinct during human evolution.
Fossil Humans • Early Homo is composed of the first humans; all species in this genus are called humans. – They have flatter and narrower faces, smaller jaws and teeth, and larger braincases than the earlier hominins do. – Toolmaking was their hallmark. • Recent Homo date from 1. 2 mya to the present. – Includes our species, Homo sapiens, which includes Cro-Magnons, and the Neanderthals. • There is evidence that both populations created art and buried their dead in an organized manner.
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Recent Homo Discovery—Homo floresiensis • H. floresiensis has recently been discovered, and has been found only on the island of Flores in Indonesia, which was also home to a species of dwarfed elephants. • H. floresiensis consisted of individuals that had braincases smaller than those of gracile australopithecines and were about a meter tall. • Fossil finds suggest that the species inhabited the island from about 100, 000 to 12, 000 years before present and that dwarfed elephants were a major source of food.
What Can Be Deduced from the Fossil Record? • The shared, derived character that defines the hominins is bipedalism. • Several species from the lineage were present simultaneously during most of hominin evolution. • The fossil record strongly indicates that different hominin species lived in physical contact. • Compared with the australopithecines and the great apes, species in the genus Homo have extremely large brains relative to their overall body size.
Fossil Humans • Several lines of evidence support the hypothesis that increased tool and language use triggered natural selection for the ability to reason and communicate, which resulted in humans with large brains.
The Out-of-Africa Hypothesis • Fossils of Homo sapiens, Homo erectus, and Homo neanderthalensis are present in different locations during the same period, from about 160, 000 to 100, 000 years ago. • Data suggest that modern humans originated in Africa. – A population that left Africa split into three broad groups that spread throughout the world. • This scenario for the evolution of Homo sapiens is called the out-of-Africa hypothesis.
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