Chapter 17 Lecture Notes PDF

Lecture Outline I. Biology and Society: Evolving Adaptability **1.** What makes humans such successful animals? **a.** Much of our success is due to brain power. **b.** The ratio of brain volume to body mass in humans is roughly 2.5 times the brain volume to body mass ratio in chimpanzees, our...

Lecture Outline I. Biology and Society: Evolving Adaptability **1.** What makes humans such successful animals? **a.** Much of our success is due to brain power. **b.** The ratio of brain volume to body mass in humans is roughly 2.5 times the brain volume to body mass ratio in chimpanzees, our closest primate relatives. **c.** The part of our brain that deals with problem solving, language, logic, and understanding other people is particularly well-developed. **d.** Although body size has remained roughly the same for about the last 1.5 million years of human evolution, brain size has increased by about 40%. **e.** Other species can fly, breathe underwater, or produce millions of offspring in their lifetimes, but none can match our ability to learn and change our behavior. **2.** Humans are just one of the 1.3 million species of animals named and described by biologists. **3.** This amazing diversity arose through hundreds of millions of years of evolution as natural selection shaped animal adaptations to Earth's many environments. II. The Origins of Animal Diversity: What Is an Animal? **1.** Animal life began in Precambrian seas with the evolution of multicellular creatures that ate other organisms. **2. Animals** are eukaryotic, multicellular, heterotrophic organisms that obtain nutrients by eating and, are able to digest food within their bodies. **a.** Animal cells lack the cell walls that provide strong support in the bodies of plants and fungi. **b.** Most animals have muscle cells for movement and nerve cells that control the muscles. **a.** are diploid, **b.** reproduce sexually, and **c.** proceed through basic stages found in most animal life cycles. **a.** Scientists have proposed several hypotheses, including increasingly complex predator-prey relationships and an increase in atmospheric oxygen. **b.** But whatever the cause of the rapid diversification, it is likely that the set of "master control" genes---the genetic framework of information flow for building complex bodies---was already in place. III. Identifying Major Themes **1.** It is likely that the set of "master control" genes that allow building complex bodies was in place before rapid diversification. **2.** *Which major theme is illustrated by this action?* **a.** The relationship of structure to function **b.** Information flow **c.** Pathways that transform energy and matter **d.** Interactions within biological systems **e.** Evolution **3.** The head of a tapeworm is equipped with suckers and hooks that lock the worm to the intestinal lining of the host. **4.** *Which major theme is illustrated by this action?* **a.** The relationship of structure to function **b.** Information flow **c.** Pathways that transform energy and matter **d.** Interactions within biological systems **e.** Evolution **5.** Bees and flies pollinate our crops and orchards. Other insects are carriers of the microbes that cause many human diseases. Insects also compete with people for food by eating our crops. **6.** *Which major theme is illustrated by this action?* **a.** The relationship of structure to function **b.** Information flow **c.** Pathways that transform energy and matter **e.** Evolution **1.** Historically, biologists have categorized animals by "body plan," general features of body structure. **a.** Distinctions between body plans were used to construct phylogenetic trees showing the evolutionary relationships among animal groups. **b.** More recently, a wealth of genetic data has allowed evolutionary biologists to modify and refine groups. **c.** A major branch point in animal evolution distinguishes sponges from all other animals based on structural complexity. Unlike more complex animals, sponges lack tissues, groups of similar cells that perform a function. **Checkpoint:** In the phylogeny shown to the right, chordates are most closely related to which other animal phylum? **2.** A second major evolutionary split is based on body symmetry. **a. Radial symmetry** refers to animals that are identical all around a central axis. **b. Bilateral symmetry** exists where there is only one way to split the animal into equal halves. **3.** The evolution of body cavities also helped lead to more complex animals. A\ **body cavity** is a fluid-filled space separating the digestive tract from the outer\ body wall. IV. Major Invertebrate Phyla: Sponges **1. Invertebrates** are animals without backbones and represent 95% of the animal kingdom. **2. Sponges** (phylum Porifera) **a.** are stationary animals, **b.** lack true tissues, and **c.** probably evolved very early from colonial protists. **d.** The body of a sponge resembles a sac perforated with holes. Choanocyte cells move water through the pores into a central cavity and then out of the sponge through a larger opening. **Checkpoint:** In what fundamental way does the structure of a sponge differ from that of all other animals? **A.** Cnidarians **1. Cnidarians** (phylum Cnidaria) are characterized by **a.** the presence of body tissues, **b.** radial symmetry, and **c.** tentacles with stinging cells. **d.** The basic body plan of a cnidarian is a sac with a central digestive compartment, the **gastrovascular** **cavity**. **e.** The body plan has two variations: i. the stationary **polyp** and ii. the floating **medusa**. **Checkpoint:** In what fundamental way does the body plan of a cnidarian differ from that of other animals? **2.** Cnidarians (phylum Cnidaria) are carnivores that use tentacles, arranged in a ring around the mouth, to capture prey and push the food into the gastrovascular cavity, where digestion begins. **3.** The tentacles are armed with cnidocytes ("stinging cells") that function in **1. Molluscs** (phylum Mollusca) are **a.** soft-bodied animals and **b.** usually protected by a hard shell. **2.** Many molluscs feed by extending a file-like organ called a **radula** to scrape up food. **3.** There are 100,000 known species of molluscs, with most being marine animals. **4.** All molluscs have a similar body plan with three main parts: **a.** a muscular foot usually used for movement, **b.** a visceral mass containing most of the internal organs, and **c.** a **mantle**, a fold of tissue that secretes the shell if present. **5.** There are three major groups of molluscs. **a. Gastropods** include snails, which are protected by a single, spiraled shell into which the animal can retreat when threatened, or have no shell at all, as with slugs and sea slugs. **b. Bivalves** include clams, oysters, mussels, and scallops; they have a shell divided into two halves hinged together. **c. Cephalopods** include squids and octopus, are all marine, have fast and agile bodies, have large brains, and include a few species with large, heavy shells, but in most it is small and internal. **1. Flatworms** (phylum Platyhelminthes) **a.** Flatworms are the simplest animals with bilateral symmetry and are ribbonlike, ranging from about 1 mm to about 20 m (about 65 ft) in length. **b.** Most flatworms have a highly branched gastrovascular cavity with a single opening. **c.** There are about 20,000 species of flatworms living in marine, freshwater, and damp terrestrial habitats. **d.** Flatworms include forms that are parasites or free-living in marine, freshwater, or damp habitats. Blood flukes and tapeworms parasitize many vertebrates. **Checkpoint:** Flatworms are the simplest animals to display a body plan that is \_\_\_\_\_\_\_\_. **1. Annelids** (phylum Annelida) **a.** Annelids have **body segmentation**, which is the subdivision of the body along its length into a series of repeated parts called segments. **b.** There are about 16,500 annelid species, ranging in length from less than 1 mm to the giant Australian earthworm, which can grow up to 3 m long. **c.** Annelids live in damp soil, the sea, and most freshwater habitats. **d.** Annelids exhibit two characteristics shared by all other bilateral animals except flatworms: i. ii. **Checkpoint:** The body plan of an annelid displays \_\_\_\_\_\_\_\_, meaning that the body is divided into a series of repeated regions. **2.** Recent molecular evidence has identified two major groups of annelids. **a.** Errantia - Most **errantians** are marine and many have active, mobile ways of life. Some errantians, such as a ragworm, crawl or burrow in the sediments; others are free-swimming. **b.** Sedentaria - **Sedentarians**, which include earthworms, many tube-dwellers, and leeches, tend to be less mobile than errantians. Tube-dwellers build tubes by secreting calcium carbonate or by mixing mucus with bits of sand and broken shells. **1. Roundworms** (also called **nematodes**, phylum Nematoda) get their common name from their cylindrical body, which is usually tapered at both ends. **a.** Nematodes are important decomposers and parasites in plants and animals. **b.** Roundworms are among the most numerous and widespread of all animals. About 25,000 species of roundworms are known, and perhaps ten times that number actually exist. **c.** Roundworms range in length from 1 mm to 1 m. **1. Arthropods** (phylum Arthropoda) are named for their jointed appendages. **2.** General **Characteristics** of Arthropods i. ii. **3.** Arachnids **a. Arachnids** i. iii. iv. **4.** Crustaceans **a. Crustaceans** i. iii. have multiple pairs of specialized appendages, and ii. iv. One group of crustaceans, the isopods, is represented on land by pill bug. v. All of these animals exhibit the arthropod characteristic of multiple pairs of specialized appendages. **5.** Millipedes and Centipedes **a.** Millipedes and centipedes are terrestrial arthropods that have similar segments over most of the body. **b. Millipedes** i. vi. have two pairs of short legs per body segment. i. vii. have one pair of legs per body segment. **6.** Insect Anatomy and Insect Diversity **a. Insects** typically have a three-part body consisting of a head, a thorax, and an abdomen. i. viii. The mouthparts are adapted for particular kinds of eating. ix. Flight is one key to the great success of insects. x. Insects outnumber all other forms of life combined. xi. Insects live in almost every terrestrial habitat, fresh water, and the air but are rare in the seas, where crustaceans are the dominant arthropods. **7.** Insect Diversity **a.** Animals so numerous, diverse, and widespread as insects affect the lives of all other terrestrial organisms, including people, in many ways. i. xii. Other interactions are harmful to people. For example, insects are carriers of the microbes that cause many human diseases, such as malaria. Insects also eat our field crops. xiii. Thus, insects provide many examples of interactions within biological systems. **b.** Many insects undergo **metamorphosis** in their development. i. xiv. In other cases, insects have distinctive larval stages specialized for eating and growing that look entirely different from the adult stage, which is specialized for dispersal and reproduction. Metamorphosis from the larva to the adult occurs during a pupal stage. **G.** Echinoderms **1. Echinoderms** (**phylum** Echinodermata) are named for their spiny surfaces. They **a.** lack body segments, **b.** usually have radial symmetry as adults, but the larval stage is bilaterally symmetrical, **c.** have an **endoskeleton** (interior skeleton) made of hard plates just beneath the\ skin, and **d.** are all marine and have a **water vascular system**, a network of water-filled canals that circulate water throughout the echinoderm's body, facilitating gas exchange and waste disposal. **2.** Echinoderms share an evolutionary branch with chordates, the phylum that includes vertebrates. **3.** Analysis of embryonic development can differentiate the echinoderms and chordates from the evolutionary branch that includes molluscs, flatworms, annelids, roundworms, and arthropods. **Checkpoint:** Contrast the skeleton of an echinoderm with that of an arthropod. V. Vertebrate Evolution and Diversity **1.** Vertebrates are the group that includes humans and our closest relatives. **a.** All vertebrates have endoskeletons, a characteristic shared with most echinoderms. **b.** However, vertebrate endoskeletons are unique in having a skull and a backbone, a series of bones called vertebrae (singular, vertebra), for which the group is named. **1. Chordates** (phylum Chordata) share four key features that appear in the embryo and sometimes in the adult. **a.** a **dorsal, hollow nerve cord**, **b.** a **notochord**, **c. pharyngeal slits**, and **d.** a **post-anal tail**. **2.** Chordates also have body segmentation, apparent in the backbone of vertebrates and segmental muscles of all chordates. **3.** Two groups of chordates, **tunicates** and **lancelets**, are invertebrates (**Figure 17.29**). **4.** All other chordates are **vertebrates**, which retain the basic chordate characteristics but have additional features that are unique, including the backbone. **5. Figure 17.30** is an overview of chordate and vertebrate evolution. **1.** The first vertebrates were aquatic and probably evolved during the early Cambrian period, about 542 million years ago. **a.** They lacked jaws and are represented today by hagfishes and lampreys. i. xv. Most species of lampreys are parasites that use their jawless mouths as suckers to attach to the sides of large fish. **2.** The two major groups of living fishes are the **a. cartilaginous fishes** (sharks and rays), with a flexible skeleton made of cartilage, and **b. bony fishes**, with a skeleton reinforced by hard calcium. **3.** Bony fishes include **a. ray-finned fishes** such as tuna and trout and **b. lobe-finned fishes** such as lungfishes and the coelacanth, a deep-sea dweller once thought to be extinct. **4.** Cartilaginous and bony fishes have a **lateral line** **system** that detects minor vibrations in the water. **5.** Bony fish have **a.** a protective flap called the **operculum** that covers a chamber housing the gills and **b.** a **swim bladder**, a gas-filled sac that helps them be buoyant. **1. Amphibians** **a.** exhibit a mixture of aquatic and terrestrial adaptations, **b.** are tied to water because their eggs, lacking shells, dry out quickly in the air, and **c.** typically undergo metamorphosis from an aquatic larva to a terrestrial adult. **2.** Amphibians were the first vertebrates to colonize land. **a.** They descended from fishes that had lungs and fins with muscles and skeletal supports strong enough to enable some movement, however clumsy, on land. **b.** Terrestrial vertebrates---amphibians, reptiles, and mammals--- are collectively called **tetrapods**, which means "four feet." **c.** The fossil record chronicles the evolution of four-limbed amphibians from fishlike ancestors. **1. Reptiles** include snakes, lizards, turtles, crocodiles, alligators, and birds and a number of extinct groups, including most of the dinosaurs. **2.** Reptiles display two adaptations to living on land. **a.** Scaled waterproof skin prevents dehydration. **b.** Reptiles (including birds) and mammals are **amniotes**, which produce **amniotic eggs**, which are fluid-filled, have waterproof shells, and enclose the developing embryo. The amniotic egg functions as a self-contained "pond" that enables amniotes to complete their life cycle on land. **3.** Nonbird Reptiles **a.** Nonbird reptiles are often called "cold-blooded" animals because they do not use their metabolism extensively to control body temperature. i. xvi. By heating directly with solar energy rather than through the metabolic breakdown of food, a nonbird reptile can survive on less than 10% of the calories required by a mammal of equivalent size. **b.** Reptiles were far more widespread, numerous, and diverse during the Mesozoic era. i. xvii. The age of reptiles began to fade about 70 million years ago. Around that time, the global climate became cooler and more variable. xviii. This was a period of mass extinctions that claimed all the dinosaurs by about 66 million years ago, except for one lineage, known today as birds. **4.** Birds **a.** Genetic and fossil evidence shows that **birds** are indeed reptiles, having evolved from a lineage of small, two-legged dinosaurs called theropods. **b.** Birds have many adaptations that enhance flight including honeycombed bones, only one ovary instead of a pair, and lack of teeth. **c.** Unlike other reptiles, birds are **endotherms**, meaning they use their own metabolic heat to maintain a warm, constant body temperature. **d.** Bird wings are airfoils that illustrate the same principles of aerodynamics as airplane wings. i. xix. Feathers are made of the same protein that forms the scales of reptiles. xx. Feathers may have functioned first as insulation, helping birds retain body heat, or for courtship displays. xxi. Only later were they adapted as flight gear. **1.** There are two major lineages of amniotes: one that led to the reptiles and one that produced mammals. **2.** The first mammals arose about 200 million years ago and were small, nocturnal insect eaters. Mammals became much more diverse after the downfall of the dinosaurs. **3.** Mammals have two unique characteristics: **a.** Mammary glands (which produce milk, a nutrient-rich substance to feed the young) and **b.** Hair, which insulates the body. **4.** There are three major groups of mammals. **a. Monotremes** are egg-laying mammals. **b. Marsupials** are pouched mammals with a **placenta.** The placenta consists of embryonic and maternal tissues. It joins the embryo to the mother within the uterus. In the placenta, the embryo receives oxygen and nutrients from maternal blood that flows near the embryonic blood system. **c. Eutherians** are also called **placental mammals** because their placentas provide a more intimate and longer-lasting association between the mother and her developing young. VI. The Human Ancestry: The Evolution of Primates **1. Primates** is the mammalian group that includes *Homo sapiens* and our closest kin. **a.** Primates evolved from insect-eating mammals in the late Cretaceous, about 65 million years ago. **b.** Those early primates were small, arboreal (tree-dwelling) mammals. Thus, primates were first distinguished by characteristics that were shaped, through natural selection, by the demands of living in the trees. **1.** The arboreal primate traits include **a.** limber shoulder joints, which make it possible to swing from branch to branch, **b.** eyes that are close together on the front of the face, creating overlapping fields of vision that enhance depth perception, **c.** excellent eye-hand coordination, and **d.** extensive parental care. Mammals devote more energy to caring for their young than most other vertebrates, and primates are among the most attentive parents of all mammals. **2.** Taxonomists divide the **primates** into three main groups. **a.** The first group of primates lives in Madagascar, southern Asia, and Africa and\ includes lemurs, lorises, and bush babies. **b.** Tarsiers, small nocturnal tree-dwellers found only in Southeast Asia, form the\ second group of primates. **c.** The third group, **anthropoids**, includes monkeys and apes. Anthropoids also have a fully opposable thumb; that is, they can touch the tips of all four fingers with their thumb. **a.** Although all apes are capable of living in trees, only gibbons and orangutans are primarily arboreal. **b.** Gorillas and chimpanzees are highly social. **c.** Apes have larger brains proportionate to body size than monkeys, and more\ adaptable behavior. **d.** Apes include humans. **1.** The fossil record and molecular systematics indicate that humans and chimpanzees have shared a common African ancestry for all but the last 6--7 million years. **2.** Misconceptions about human evolution persist. One of these myths is the question "If chimpanzees were our ancestors, then why do they still exist?" **a.** Scientists do not think that humans evolved from chimpanzees. Present-day humans and chimpanzees diverged from a common ancestor several million years ago. **3.** Some Common Misconceptions **a.** Another myth envisions human evolution as a ladder with a series of steps leading directly from an ancestral anthropoid to *Homo sapiens*, often illustrated as a parade of fossil **hominins** (members of the human family) becoming progressively more modern. i. xxii. Instead, human evolution is more like a multibranched bush than a ladder. **4.** Australopithecus and the Antiquity of Bipedalism i. xxiii. That hypothesis was overturned when a team of researchers in Ethiopia unearthed a stunning 3.24-million-year-old female hominin that had a small brain and walked on two legs. xxiv. Officially named *Australopithecus afarensis*, but nicknamed Lucy by her discoverers, the 3.24 million year old individual was only about 3 feet tall with a head about the size of a softball. xxv. Corroborating evidence of early bipedalism was found soon after---the footprints of two upright-walking hominins preserved in a 3.6-million-year-old layer of volcanic ash. xxvi. Since these initial discoveries, many more *Australopithecus afarensis* fossils have been found, including most of the skeleton of a three-year-old member of the species and other species of *Australopithecus*. **5.** *Homo habilis* and the Evolution of Inventive Minds **a.** Enlargement of the human brain is first evident in fossils from East Africa dating to about 2.4 million years ago. Thus, the fundamental human trait of an enlarged brain evolved a few million years after bipedalism. **b.** Anthropologists have found skulls with brain capacities intermediate in size between those of the latest *Australopithecus* species and those of **Homo sapiens**. **c.** Simple handmade stone tools are sometimes found with the larger-brained fossils, which have been dubbed *Homo habilis* ("handy man"). **6.** *Homo erectus* and the Global Dispersal of Humanity i. xxvii. was taller and had a larger brain capacity than *H.* *habilis*, and xxviii. migrated to populate many regions of Asia and Europe, moving as far as Indonesia. xxix. Intelligence enabled this species to continue succeeding in Africa and also to survive in the colder climates of the north. **7.** *Homo neanderthalensis* **a.** *Homo neanderthalensis*, commonly called Neanderthals, had a large brain, hunted big game with tools made from stone and wood, and lived in Europe as much as 350,000 years ago. They spread to the Near East, central Asia, and southern Siberia, but by 28,000 years ago were extinct. **b.** Analysis of DNA extracted from Neanderthal fossils showed that humans are not the descendants of Neanderthals but indicated that humans and Neanderthals shared a common ancestor, with their lineages diverging about 400,000 years ago. **c.** Sequencing of Neanderthal genomes suggests that interbreeding between Neanderthals and some populations of *Homo sapiens* left a genetic legacy in our species. i. xxx. Africans are the exception, as their DNA carries no detectable trace of Neanderthal ancestry. xxxi. Scientists also learned that at least some Neanderthals had pale skin and red hair. **8.** The Origin and Dispersal *of* *Homo sapiens* **a.** The oldest known fossils of our own species, *Homo* *sapiens*, i. xxxii. date from 160,000 to 195,000 years ago. xxxiii. DNA studies strongly suggest that all living humans can trace their ancestry back to a single African *Homo sapiens* lineage that began 160,000 to 200,000 years ago. **b.** The oldest known fossils of *Homo sapiens* were discovered in Ethiopia and date from 160,000 to 195,000 years ago i. xxxiv. The date of the first arrival of humans in the New World is uncertain, although generally accepted evidence suggests a minimum of 15,000 years ago. **Checkpoint:** When would a *Homo sapiens* individual have had an opportunity to meet a Neanderthal? **c.** Certain uniquely human traits have allowed for the development of human societies. i. xxxv. The period of growth is longest for humans, lengthening the time for parents to care for their offspring and pass along culture, the social transmission of accumulated knowledge, customs, beliefs, and art over generations. The major means of this transmission is language, spoken and written. xxxvi. Humans have evolved culturally as well as biologically. i. xxxvii. We do not have to wait to adapt to an environment through natural selection; we simply change the environment to meet our needs. VII. The Process of Science: What Can Lice Tell Us about Ancient Humans?"  **1. Background**: When did humans first start wearing clothes? Archeological evidence provides a very rough time frame. **a.** To find a narrower time range for the origin of clothing, researchers turned to lice, tiny blood-sucking parasites. Our distant ancestors, which were fur-covered like present-day primates, were parasitized by one species of louse. **b.** By about 1.2 million years ago, hominins had lost most of their body hair, stranding lice on our scalps. **c.** Researchers hypothesized that analyzing the evolutionary divergence of lice into two distinct types would allow them to estimate when our ancestors first wore clothes. **2. Method**: The number of genetic differences between populations can be used to estimate how long the populations have been separated, a method known as a molecular clock. To construct a molecular clock for the divergence of head lice and clothing lice, researchers compared four DNA sequences for which the mutation rate---the average number of changes---was known. **3. Results**: The molecular clock shows that clothing offered a new habitat for the lice between 83,000 and 170,000 years ago, when populations of head lice and clothing lice began to diverge. **a.** Thus, modern humans originated the use of clothing, probably in Africa. **b.** Humans spreading north would have encountered the exceptionally cold climate that resulted from a series of ice ages, making clothing particularly useful. VIII. Evolution Connection: Are We Still Evolving? **1.** The human body has not changed much in the past 100,000 years. **2.** But as humans wandered far from their site of origin and settled in diverse environments, populations encountered different selective forces. **a.** The high frequency of sickle hemoglobin in certain populations is an adaptation that protects against the deadly disease malaria. **b.** Populations that kept dairy herds evolved the ability to digest lactose as adults. **3.** One of the most striking differences among people is skin color. **a.** The loss of skin pigmentation in humans who migrated north from Africa is thought to be an adaptation to low levels of ultraviolet (UV) radiation in northern latitudes. **b.** Dark pigment blocks the UV radiation necessary for synthesizing vitamin D, essential for proper bone development, in the skin. **4.** Recent research has turned up numerous other examples of adaptations that enabled us to colonize Earth's varied environments. **a.** For instance, indigenous people in the Andes Mountains in South America live at altitudes up to 12,000 feet (2.3 miles), where the air has 40% less oxygen than at sea level. **b.** Researchers have identified genes that have undergone evolutionary changes in response to this challenging environment.