3.1.1 The physical structure of the earth

Weathering describes the breaking down or dissolving of rocks and minerals on the surface of the Earth. Water, ice, acids, salts, plants, animals, and changes in temperature are all agents of weathering. Once a rock has been broken down, a process called erosion transports the bits of rock and mineral away. No rock on Earth is hard enough to resist the forces of weathering and erosion. Together, these processes carved landmarks such as the Grand Canyon, in the U.S. state of Arizona. This massive canyon is 446 kilometers (277 miles) long, as much as 29 kilometers (18 miles) wide, and 1,600 meters (1 mile) deep. Weathering and erosion constantly change the rocky landscape of Earth. Weathering wears away exposed surfaces over time. The length of exposure often contributes to how vulnerable a rock is to weathering. Rocks, such as lavas, that are quickly buried beneath other rocks are less vulnerable to weathering and erosion than rocks that are exposed to agents such as wind and water, As it smoothes rough, sharp rock surfaces, weathering is often the first step in the production of soils. Tiny bits of weathered minerals mix with plants, animal remains, fungi, bacteria, and other organisms. A single type of weathered rock often produces infertile soil, while weathered materials from a collection of rocks is richer in mineral diversity and contributes to more fertile soil. Soils types associated with a mixture of weathered rock include glacial till, loess, and alluvial sediments. Weathering is often divided into the processes of mechanical weathering and chemical weathering. Biological weathering, in whichliving or once-living organisms contribute to weathering, can be a part of both processes. Mechanical Weathering Mechanical weathering, also called physical weathering and disaggregation, causes rocks to crumble. Water, in either liquid or solid form, is often a key agent of mechanical weathering. For instance, liquid water can seep into cracks and crevices in rock. If temperatures drop low enough, the water will freeze. When water freezes, it expands. The ice then works as a wedge. It slowly widens the cracks and splits the rock. When ice melts, liquid water performs the act of erosion by carrying away the tiny rock fragments lost in the split. This specific process (the freeze-thaw cycle) is called frost weathering or cryofracturing. Figure 4.3 Frost Wedging Temperature changes can also contribute to mechanical weathering in a process called thermal stress. Changes in temperature cause rock to expand (with heat) and contract (with cold). As this happens over and over again. the structure of the rock weakens. Over time, it crumbles. Rocky desert landscapes are particularly vulnerable to thermal stress. The outer layer of desert rocks undergo repeated stress as the temperature changes from day Eventually, Lo outer night. layersflake off in thin sheets, a process called exfoliation. Exfoliation contributes to the formation of bornhardts, one of the most dramatic features in landscapes formed by weathering and erosion. Bornhardts are tall, domed, isolated rocks often found areas. in tropical Sugarloaf Mountain, an iconic landmark in Rio de Janeiro, Brazil, is bornhardt. a Salt also works to weather rock in a process called haloclasty. Saltwater sometimes gets into the cracks and pores of rock. If the saltwater evaporates, salt crystals are left behind. As the crystals grow, they put pressure on the rock, slowly breaking it apart. Plants and animals can be agents of mechanical weathering. The seed of a tree may sprout in soil that has collected in a cracked rock. As the roots grow, they widen the cracks, eventually breaking the rock into pieces. Over time, trees can break apart even large rocks. Even small plants, such as mosses, can enlarge tiny cracks as they grow. Animals that tunnel underground, such as moles and prairie dogs, also work to break apart rock and soil. Other animals dig and trample rock aboveground, causing rock to slowly crumble. Chemical Weathering Chemical weathering changes the molecular structure of rocks and soil.For instance, carbon dioxide from the air or soil sometimes combines with water in a process called carbonation. This produces a weak acid, called carbonic acid, that can dissolve rock. Carbonic acid is especially effective at dissolving limestone. When carbonic acid seeps through limestone underground, it can open up huge cracks or hollow out vast networks of caves. Carlsbad Caverns National Park, in the U.S. state of New Mexico, includes more than 119 limestone caves created by weathering and erosion. The largest is called the Big Room.. With an area of about 33,210 square meters (357,469 square feet), the Big Room is the size of six football fields. Another type of chemical weathering works on rocks that contain iron. These rocks turn to rust in a process called oxidation. Rust is a compound created by the interaction of oxygen and iron in the presence of water. As rust expands, it weakens rock and helps break it apart. Another familiar form of chemical weathering is hydrolysis. In the process of hydrolysis, a new solution (a mixture of two or more substances) is formed as chemicals in rock interact with water. In many rocks, for example, sodium minerals interact with water to form a saltwater solution. Hydration and hydrolysis contribute to flared slopes, another dramatic example of a landscape formed by weathering and erosion. Flared slopes are sometimes nicknamed "wave rocks." Their c-shape is largely concave rock formations a result of subsurface weathering, in which hydration and hydrolysis wear away rocks beneath the landscape's surfaceWeathering and People Weathering is a natural process, but human activities can speed it up. For example, certain kinds of air pollution increase the rate of weathering Burning coal, natural and petroleum releases chemicals such as nitrogen oxide and gas, sulfur dioxide into the atmosphere. When these chemicals combine with sunlight and moisture, they change into acids. They then fall back to Earth as acid rain. Acid rain rapidly weathers limestone, marble, and other kinds of stone. The effects of acid rain can often be seen on gravestones, making names and other inscriptions impossible to read. Acid rain has also damaged many historic buildings and monuments. For example, at 71 meters (233 feet) tall, the Leshan Giant Buddha at Mount Emei, China is the world's largest statue of the Buddha. It was carved 1,300 years ago and sat unharmed for centuries. An innovative drainage system mitigates the natural process of erosion But in recent years, acid rain has turned the statue's nose black and made some of its hair crumble and fall.

CHARACTERISTICS OF LIFE The world is filled with familiar objects, such as tables, rocks, plants, pets, and automobiles. Which of these objects are living or were once living? What are the criteria for assigning something to the living world or the nonliving world? Biologists have established that living things share seven characteristics of life. These characteristics are organization and the presence of one or more cells, response to a stimulus (plural, stimuli), homeostasis, metabolism, growth and development, reproduction, and change through time. Organization and Cells Organization is the high degree of order within an organism’s internal and external parts and in its interactions with the living world. For example, compare an owl to a rock. The rock has a spe- cific shape, but that shape is usually irregular. Furthermore, differ- ent rocks, even rocks of the same type, are likely to have different shapes and sizes. In contrast, the owl is an amazingly organized individual, as shown in Figure 1-2. Owls of the same species have the same body parts arranged in nearly the same way and interact with the environment in the same way. Copyright © by Holt, Rinehart and Winston. All rights reserved. ORGANISM (Barn Owl) ORGAN (Owl’s Ear) TISSUE (Nervous Tissue Within the Ear) CELL (Nerve Cell) Every living organism has a level of organization. The different levels of organization for a complex multicellular organism, such as an owl, are shown in the figure below. FIGURE 1-2 THE SCIENCE OF LIFE 7 All living organisms, whether made up of one cell or many cells, have some degree of organization. A cell is the smallest unit that can perform all life’s processes. Some organisms, such as bacteria, are made up of one cell and are called unicellular (YOON-uh-SEL-yoo-luhr) organisms. Other organisms, such as humans or trees, are made up of multiple cells and are called multicellular (MUHL-ti-SEL-yoo-luhr) organisms. Complex multicellular organisms have the level of orga- nization shown in Figure 1-2. In the highest level, the organism is made up of organ systems, or groups of specialized parts that carry out a certain function in the organism. For example, an owl’s ner- vous system is made up of a brain, sense organs, nerve cells, and other parts that sense and respond to the owl’s surroundings. Organ systems are made up of organs. Organs are structures that carry out specialized jobs within an organ system. An owl’s ear is an organ that allows the owl to hear. All organs are made up of tissues. Tissues are groups of cells that have similar abilities and that allow the organ to function. For example, nervous tissue in the ear allows the ear to detect sound. Tissues are made up of cells. A cell must be covered by a membrane, contain all genetic information necessary for replication, and be able to carry out all cell functions. Within each cell are organelles. Organelles are tiny structures that carry out functions necessary for the cell to stay alive. Organelles contain biological molecules, the chemical compounds that provide physical structure and that bring about movement, energy use, and other cellular functions. All biological molecules are made up of atoms. Atoms are the simplest particle of an ele- ment that retains all the properties of a certain element. Response to Stimuli Another characteristic of life is that an organism can respond to a stimulus—a physical or chemical change in the internal or external environment. For example, an owl dilates its pupils to keep the level of light entering the eye constant. Organisms must be able to respond and react to changes in their environment to stay alive. ORGANELLE (Mitochondrion) BIOLOGICAL MOLECULE (Phospholipid) ATOM (Oxygen) cell from the Latin, cella meaning “small room,” or “hut” Word Roots and Origins www.scilinks.org Topic: Characteristics of Life Keyword: HM60257 mb06se_bios01.qxd 5/18/07 10:37 AM Page 7 8 CHAPTER 1 Homeostasis All living things, from single cells to entire organisms, have mecha- nisms that allow them to maintain stable internal conditions. Without these mechanisms, organisms can die. For example, a cell’s water content is closely controlled by the taking in or releas- ing of water. A cell that takes in too much water will rupture and die. A cell that doesn’t get enough water will also shrivel and die. Homeostasis (HOH-mee-OH-STAY-sis) is the maintenance of a stable level of internal conditions even though environmental conditions are constantly changing. Organisms have regulatory systems that maintain internal conditions, such as temperature, water content, and uptake of nutrients by the cell. In fact, multi- cellular organisms usually have more than one way of maintain- ing important aspects of their internal environment. For example, an owl’s temperature is maintained at about 40°C (104°F). To keep a constant temperature, an owl’s cells burn fuel to produce body heat. In addition, an owl’s feathers can fluff up in cold weather. In this way, they trap an insulating layer of air next to the bird’s body to maintain its body temperature. Metabolism Living organisms use energy to power all the life processes, such as repair, movement, and growth. This energy use depends on metabolism (muh-TAB-uh-LIZ-uhm). Metabolism is the sum of all the chemical reactions that take in and transform energy and materials from the environment. For example, plants, algae, and some bacteria use the sun’s energy to generate sugar molecules during a process called photosynthesis. Some organisms depend on obtaining food energy from other organisms. For instance, an owl’s metabolism allows the owl to extract and modify the chemi- cals trapped in its nightly prey and use them as energy to fuel activities and growth. Growth and Development All living things grow and increase in size. Some nonliving things, such as crystals or icicles, grow by accumulating more of the same material of which they are made. In contrast, the growth of living things results from the division and enlargement of cells. Cell division is the formation of two new cells from an existing cell, as shown in Figure 1-3. In unicellular organisms, the primary change that occurs following cell division is cell enlargement. In multi- cellular life, however, organisms mature through cell division, cell enlargement, and development. Development is the process by which an organism becomes a mature adult. Development involves cell division and cell differen- tiation, or specialization. As a result of development, an adult organism is composed of many cells specialized for different func- tions, such as carrying oxygen in the blood or hearing. In fact, the human body is composed of trillions of specialized cells, all of which originated from a single cell, the fertilized egg. This unicellular organism, Escherichia coli, inhabits the human intestines. E. coli reproduces by means of cell division, during which the original cell splits into two identical offspring cells. FIGURE 1-3 Observing Homeostasis Materials 500 mL beakers (3), wax pen, tap water, thermometer, ice, hot water, goldfish, small dip net, watch or clock with a second hand Procedure 1. Use a wax pen to label three 500 mL beakers as follows: 27°C (80°F), 20°C (68°F), 10°C (50°F). Put 250 mL of tap water in each beaker. Use hot water or ice to adjust the tem- perature of the water in each beaker to match the temperature on the label. 2. Put the goldfish in the beaker of 27°C water. Record the number of times the gills move in 1 minute. 3. Move the goldfish to the beaker of 20°C water. Repeat observations. Move the goldfish to the beaker of 10°C. Repeat observations. Analysis What happens to the rate at which gills move when the temp- erature changes? Why? How do gills help fish maintain homeostasis? Quick Lab mb06se_bios01.qxd 5/18/07 10:37 AM Page 8 THE SCIENCE OF LIFE 9 Reproduction All organisms produce new organisms like themselves in a process called reproduction. Reproduction, unlike other characteristics, is not essential to the survival of an individual organism. However, because no organism lives forever, reproduction is essential for the continuation of a species. Glass frogs, as shown in Figure 1-4, lay many eggs in their lifetime. However, only a few of the frogs’ off- spring reach adulthood and successfully reproduce. During reproduction, organisms transmit hereditary informa- tion to their offspring. Hereditary information is encoded in a large molecule called deoxyribonucleic acid, or DNA. A short segment of DNA that contains the instructions for a single trait of an organism is called a gene. DNA is like a large library. It contains all the books—genes—that the cell will ever need for making all the struc- tures and chemicals necessary for life. Hereditary information is transferred to offspring during two kinds of reproduction. In sexual reproduction, hereditary information recombines from two organisms of the same species. The resulting offspring are similar but not identical to their parents. For example, a male frog’s sperm can fertilize a female’s egg and form a single fer- tilized egg cell. The fertilized egg then develops into a new frog. In asexual reproduction, hereditary information from different organisms is not combined; thus the original organism and the new organism are genetically the same. A bacterium, for example, reproduces asexually when it splits into two identical cells. Change Through Time Although individual organisms experience many changes during their lifetime, their basic genetic characteristics do not change. However, populations of living organisms evolve or change through time. The ability of populations of organisms to change over time is important for survival in a changing world. This factor is also impor- tant in explaining the diversity of life-forms we see on Earth today.

LESSON 3 Characteristics of Living Things Learning Objectives • Describe each characteristic of life • Relate each characteristic of life with how first forms of life evolved What sets living things apart from nonliving things? Organisms are equipped with different characteristics that allow them to grow, adapt, survive, and perpetuate. These include the ability to metabolize, respond to stimuli, interact, and reproduce, among others What are the characteristics of life? Try to look at your surroundings and identify the living things that you see. You have probably identified a lot. Many scientists believe that there are more than 10 million kinds of living things that exist on Earth today. But the question is, how can something be considered living? There are certain characteristics that all living things exhibit: the characteristics of life. Living things are made up of cells. They metabolize, grow and develop, respond to stimulus, adapt to their environment, and reproduce. Living Things Are Made up of Cells All living things are made up of cells. Cells are the basic building blocks of all living things. Each cell contains materials that carry out basic life processes such as respiration. In the 1600s, an argument against the theory of spontaneous generation was made. Italian physician and biologist Francesco Redi disproved the theory that all living things come from nonliving things. Cells have different properties and characteristics. The cell theory describes the properties of all cells. There are three tenets of the cell theory: 1. The cell is the basic unit of life. 2. All living things are composed of one or more cells. 3. All cells arise from preexisting cells. The discovery of the cell is largely attributed to Robert Hooke. Upon examining a piece of cork using a microscope that he built, Hooke observed tiny compartments that he called "cells" (from the Latin word cella, meaning "little room"). Matthias Schleiden suggested that all structural parts of plants are made up of cells. In 1839, Theodore Schwann stated that along with plants, all animals were composed of cells. From these conclusions about plants and animals, advancement on the study of animal parts and functions began. In 1855, Rudolf Virchow included the idea that all cells came from preexisting cells. Some living things are made up of only single cells. Single-celled or unicellular organisms include bacteria, some protists, and some fungi. Even though composed of single cells, these organisms carry out all the functions necessary for life. Most living things such as animals and plants, are multicellular organisms. They are composed of many cells, which are grouped together and perform specific tasks in the body. In different organisms, cells also vary in sizes, shapes, parts, and functions. There are two kinds of organisms according to their cell structure, the prokaryotes and eukaryotes (figure 5-3). Prokaryotes are single-celled organisms that lack a membrane-bound nucleus, mitochondria, and all other organelles. Its name comes from the Greek words pro, which means "before," and karyon, which means "nut or kernel." Eukaryotes are organisms with cells that contain membrane-bound nucleus and other membrane-bound organelles. The nucleus of a eukaryotic cell contains the genetic material (DNA), enclosed by a nuclear envelope. Other membrane-bound organelles are mitochondria, Golgi apparatus, and chloroplast found in photosynthetic organisms such as algae and plants. There are also unicellular eukaryotes known as protozoa. All other eukaryotes are multicellular organisms, such as plants, animals, and fungi. Living Things Metabolize Essential chemical reactions in life can be best described as building up (anabolism) and breaking down (catabolism) processes. In anabolism, the substances needed by organisms to grow, store energy, and repair tissues are synthesized. In contrast in catabolism, some complex substances are broken down, releasing the energy stored in their molecules. This happens in food digestion. This chemical building up and breaking down processes are collectively called metabolism. Metabolism, from the Greek word metabole meaning "change," is the sum total of all the life-sustaining chemical reactions in living things. It allows living things to grow, maintain their structures and functions, and respond to stimuli. Living Things Grow and Develop Growth and development are not new concepts to many. In all living things, growth involves the increase in one's size or height. However, growth is not just an increase in physical structure. It also involves complex changes in an organism. Growth and development occur rapidly from younger stages of life to maturity. In humans, animals, and plants, distinct changes brought by growth and development can be dearly identified. Microorganisms such as bacteria also undergo growth and development until they reach their maximum size and maturity. A life span is the average length of time a aving thing can live. Living things have different life spans. Humans have average life spectancy of 60 to 70 years, while some plants, such as the narra trees, can live for more than 100. Living Things Respond to Stimuli All living things respond to stimuli the environment. This responsiveness Increases survivability. Stimulus (plural: uli) is any signal or change in he environment of an organism that produces a response or reaction from that organism. Responses to stimuli depend on an organism's need. Responding to stimuli also maintains homeostasis in living things. Homeostasis is the internal balance of a body system. This balance is needed for the proper function and regulation of the living thing's body. For example, when a person is in a warmer environment, the body sweats, keeping the body maintain a temperature suited for the normal function of the body. Living Things Interact No living thing can live alone. Interaction among organisms is simultaneously happening on Earth. From the smallest microorganisms to the biggest organism, and from the North Pole to the South Pole of Earth, all are connected in one living system. An ecosystem is formed when a community of organisms interacts with another community and with their environment. Many processes and interactions, such as in a feeding relationship, life cycle, and the exchange of gases between plants and animals, occur in the ecosystem. These are some of the important processes needed to maintain life on Earth. Living Things Reproduce The ability of living things to produce offspring of their kind is called reproduction. Reproduction is not an individual organism's need, rather, it is for the species' perpetuation. In some cases, animals become extinct because of their inability to reproduce their kind. Higher forms of plants and animals reproduce through sexual reproduction. Sexual reproduction involves the union of sex cells or gametes-the egg cell from a female organism and the sperm cell from a male organism. This union gives rise to a new individual with characteristics or traits from both parents. Other simple organisms, such as bacteria and plants, can reproduce asexually. These organisms give rise to a new individual from their body. A bacterial cell divided in two through asexual reproduction gives rise to new bacteria, as shown in figure 5-5. A yeast can form buds that later on become separate individual. Plants grow new plants using their stem, leaf, and roots. Both sexual and asexual reproductions have important functions. In both cases, the genetic material (DNA) is passed on from one generation to the next, ensuring the survival of the species on Earth. 1. Bacteria copy their DNA by starting at any point on the circular chromosomes. 2. The two copies of DNA attach to the inside wall of the bacterial cell. 3. The cell starts to divide, forming a new membrane and cell wall. 4. The bacterial cell splits into two separate cells, each with their own DNA. Living Things Adapt and Evolve All living things can adapt to their environment. This adaptation is necessary for rvival. Adaptation depends on the need of an individual. A polar bear, for example, would not be able to survive in an extremely cold environment without its capacity adapt. Adaptation is any response or reaction toward a stimulus that helps in the survival of an organism. A seed-eating bird will eventually eat a worm when there are seeds to be found. This change in food choice is therefore its adapting mechanism. Prolonged adaptation to certain environments may lead to the gradual evolution of the succeeding generations. Evolution is the gradual change in organisms over a long period in response to changing environment. Living Things Are Organized Life on Earth exhibits organization. The atom is the smallest unit of matter, lowed by molecules, which are combinations of atoms. When these molecules are grouped together, they form a cell. The cell is the basic unit of life. In multicellular organisms, such as plants and animals, cells are grouped as tissues to perform specific Functions. Different tissues can be grouped further and form organs. Organs in animals include the heart, brain, and lungs, among others. The organs form organ systems that makes the function of the body more complex and efficient. Organ systems form the whole organism. All living things exhibit organization, whether they are unicellular or multicellular organisms..

Southeast Asia, vast region of Asia situated east of the Indian subcontinent and south of China. It consists of two dissimilar portions: a continental projection (commonly called mainland Southeast Asia) and a string of archipelagoes to the south and east of the mainland (insular Southeast Asia). Extending some 700 miles (1,100 km) southward from the mainland into insular Southeast Asia is the Malay Peninsula; this peninsula structurally is part of the mainland, but it also shares many ecological and cultural affinities with the surrounding islands and thus functions as a bridge between the two regions. Mainland Southeast Asia is divided into the countries of Cambodia, Laos, Myanmar (Burma), Thailand, Vietnam, and the small city-state of Singapore at the southern tip of the Malay Peninsula; Cambodia, Laos, and Vietnam, which occupy the eastern portion of the mainland, often are collectively called the Indochinese Peninsula. Malaysia is both mainland and insular, with a western portion on the Malay Peninsula and an eastern part on the island of Borneo. Except for the small sultanate of Brunei (also on Borneo), the remainder of insular Southeast Asia consists of the archipelagic nations of Indonesia and the Philippines. Southeast Asia stretches some 4,000 miles at its greatest extent (roughly from northwest to southeast) and encompasses some 5,000,000 square miles (13,000,000 square km) of land and sea, of which about 1,736,000 square miles is land. Mount Hkakabo in northern Myanmar on the border with China, at 19,295 feet (5,881 meters), is the highest peak of mainland Southeast Asia. Although the modern nations of the region are sometimes thought of as being small, they are—with the exceptions of Singapore and Brunei—comparatively large. Indonesia, for example, is more than 3,000 miles from west to east (exceeding the west-east extent of the continental United States) and more than 1,000 miles from north to south; the area of Laos is only slightly smaller than that of the United Kingdom; and Myanmar is considerably larger than France. All of Southeast Asia falls within the tropical and subtropical climatic zones, and much of it receives considerable annual precipitation. It is subject to an extensive and regular monsoonal weather system (i.e., one in which the prevailing winds reverse direction every six months) that produces marked wet and dry periods in most of the region. Southeast Asia’s landscape is characterized by three intermingled physical elements: mountain ranges, plains and plateaus, and water in the form of both shallow seas and extensive drainage systems. Of these, the rivers probably have been of the greatest historical and cultural significance, for waterways have decisively shaped forms of settlement and agriculture, determined fundamental political and economic patterns, and helped define the nature of Southeast Asians’ worldview and distinctive cultural syncretism. It also has been of great importance that Southeast Asia, which is the most easily accessible tropical region in the world, lies strategically astride the sea passage between East Asia and the Middle Eastern–Mediterranean world. Within this broad outline, Southeast Asia is perhaps the most diverse region on Earth. The number of large and small ecological niches is more than matched by a staggering variety of economic, social, and cultural niches Southeast Asians have developed for themselves; hundreds of ethnic groups and languages have been identified. Under these circumstances, it often is difficult to keep in mind the region’s underlying unity, and it is understandable that Southeast Asia should so often be treated as a miscellaneous collection of cultures that simply do not quite fit anywhere else. Roofs of the Forbidden City, Beijing, China Britannica Quiz All About Asia Yet from ancient times Southeast Asia has been considered by its neighbors to be a region in its own right and not merely an extension of their own lands. The Chinese called it Nanyang and the Japanese Nan’yō, both names meaning “South Seas,” and South Asians used such terms as Suvarnabhūmi (Sanskrit: “Land of Gold”) to describe the area. Modern scholarship increasingly has yielded evidence of broad commonalities uniting the peoples of the region across time. Studies in historical linguistics, for example, have suggested that the vast majority of Southeast Asian languages—even many of those previously considered to have separate origins—either sprang from common roots or have been long and inseparably intertwined. Despite inevitable variation among societies, common views of gender, family structure, and social hierarchy and mobility may be discerned throughout mainland and insular Southeast Asia, and a broadly common commercial and cultural inheritance has continued to affect the entire region for several millennia. These and other commonalities have yet to produce a conscious or precise Southeast Asian identity, but they have given substance to the idea of Southeast Asia as a definable world region and have provided a framework for the comparative study of its components.

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