Table Of Contents Chapter: Life's Structure And Classification

TableTable ofof ContentsContentsChapter: Life's Structure andClassificationSection 1: Living ThingsSection 2: How are livingthings classified?Section 3: Cell StructureSection 4: Viruses

LivingLiving ThingsThings1What are living things like? Any living thing is called an organism. Organisms vary in size—from the microscopicbacteria in mud puddles to gigantic oak trees—and are found justabout everywhere.

LivingLiving ThingsThings1What are living things like? They have different behaviors and foodrequirements. In spite of these differences, all organismshave similar traits. These traits determine what it means tobe alive.

LivingLiving ThingsThings1Living Things Are Organized A cell is the smallest unit of an organismthat carries on the functions of life. Some organisms are composed of just one cellwhile others arecomposed of manycells.

LivingLiving ThingsThings1Living Things Are Organized Each cell has an orderly structure andcontains the instructions for cellularorganization and function in its hereditarymaterial. All the things an organism can do arepossible because of what their cells can do.

LivingLiving ThingsThings1Living Things Grow and Develop Growth of a many-celled organism is mostlydue to an increase in the number of cells. In one-cell organisms, growth is due to anincrease in the size of cell.

LivingLiving ThingsThings1Living Things Grow and Develop Organisms change as they grow. All of the changes that take place during thelife of an organism is called development.

LivingLiving ThingsThings1Living Things Grow and Develop The length of time an organism is expectedto live is its life span. Some organisms have a short life span. Others have a much longer life span. Some bristlecone pine trees have been alivefor more than 4,600 years!

LivingLiving ThingsThings1Living Things Respond Living things must interact with theirsurroundings. Anything that causes some change in anorganism is a stimulus. The reaction to a stimulus is a response.

LivingLiving ThingsThings1Living Things Respond The regulation of an organism's internal,life-maintaining condition despite changesin its environment is called homeostasis. Homeostasis is a trait of all living things.

LivingLiving ThingsThings1Living Things Use Energy The energy used by most organisms comeseither directly or indirectly from the Sun. Plants and some other organisms use theSun’s energy, carbon dioxide, and water tomake food.

LivingLiving ThingsThings1Living Things Use Energy Organisms that do notget energy directlyfrom the Sun musttake in oxygen inorder to release theenergy in foods.

LivingLiving ThingsThings1Living Things Use Energy Some bacteria can’t use the Sun’s energy toproduce food; instead, the bacteria useenergy stored in some chemical compoundsand carbon dioxide to make food.

LivingLiving ThingsThings1Living Things Reproduce All living things eventually reproduce, tomake more of their own kind. Some bacteria reproduce every 20 minutes,while it might take a pine tree two years toproduce seeds. Withoutreproduction, livingthings would notexist to replace thoseindividuals that die.

LivingLiving ThingsThings1What do living things need? All living things need a place to live,water, and food source to survive.

LivingLiving ThingsThings1A Place to Live All organisms need aplace to live that is suitedto their unique needs. Could a cactus survivein Antarctica, or apenguin in the Sahara? A place to live alsoprovides enough spacefor the organism.

LivingLiving ThingsThings1Water All organisms musttake in water fromtheir surroundings. Organisms take inand give off largeamounts of watereach day.

LivingLiving ThingsThings1Water Homeostasis balances the amount ofwater exchanged. Water performs many functions, suchas transporting materials within a cellbetween cells.

LivingLiving ThingsThings1Food Sources Living things are made up of substancessuch as proteins, fat, and sugars. Animals take in these substances as partof the foods that they eat. Plants and some bacteria make theirown food.

LivingLiving ThingsThings1Food Sources When organisms die, substances in theirbodies are broken down and released intothe soil or air. The substances can then be used again byother living organisms.

SectionSection CheckCheck1Question 1A is the smallest unit of an organismthat carries on the functions of life.AnswerThe answer is cell. All the things an organismcan do are possible because of what their cellscan do.

SectionSection CheckCheck1Question 2Any living thing is called a(n) .AnswerThe answer is organism. All organisms havesimilar traits which determine what it means tobe alive.

SectionSection CheckCheck1Question 3Which is the smallest unit of an organism thatcan carry on life functions?A. cellB. organC. organ systemD. tissue

SectionSection CheckCheck1AnswerThe correct answer is A. The human body isorganized into many different types of cells.

HowHow areare livingliving thingsthings classified?classified?2Classification Carolus Linnaeus, a Swedish naturalist,developed a new system of groupingorganisms that was accepted and used bymost scientists. His classification system was based onlooking for organisms with similar structures. Linnaeus also developed a scientific namingsystem that is still used today.

HowHow areare livingliving thingsthings classified?classified?2Binomial Nomenclature The two-word naming system that Linnaeusused to name various organisms is calledbinomial nomenclature (bi NOH mee ul ·NOH mun klay chur). This two-word name is an organism’s species.

HowHow areare livingliving thingsthings classified?classified?2Binomial Nomenclature The first word of the twoword name identifies thegenus of the organism.Ambystomagenus A genus is a group of similar species. The second word of the nameusually describes a feature.tigrinumfeature

HowHow areare livingliving thingsthings classified?classified?2Uses of Scientific Names Scientific names are used for four reasons. First, they help avoid mistakes. Often, common names for two differentorganisms are the same. Scientific names help distinguish betweenthose organisms.

HowHow areare livingliving thingsthings classified?classified?2Uses of Scientific Names Second, organisms with similar evolutionaryhistories are classified together. Third, scientific names give descriptiveinformation about the species.

HowHow areare livingliving thingsthings classified?classified?2Uses of Scientific Names Fourth, scientific names allow informationabout organisms to be organized easily andefficiently. Theclassificationof the bottlenosed dolphinshows that itis in the orderCetacea.

HowHow areare livingliving thingsthings classified?classified?2Modern Classification Like Linnaeus, modern scientists usesimilarities in structure to classify organisms. They also study fossils, hereditaryinformation, and early stages of development.

HowHow areare livingliving thingsthings classified?classified?2Modern Classification Phylogeny (fi LAH juh nee) is theevolutionary history of an organism, that is,how the organism has changed over time. Today, it is the basis for the classification ofmany organisms.

HowHow areare livingliving thingsthings classified?classified?2Modern Classification In the classification system used today, thesmallest group is a species. There arebroadergroupsprecedingspecies, thelargest ofwhich is akingdom.

HowHow areare livingliving thingsthings classified?classified?2Modern Classification Some scientists have proposed that beforeorganisms are grouped into kingdoms,they should be placed in larger groupscalled domains. One proposed system groups all organismsinto three domains.

HowHow areare livingliving thingsthings classified?classified?2Tools for Identifying Organisms Scientists use field guides and dichotomous(di KAH tuh mus) keys to identify organisms.

HowHow areare livingliving thingsthings classified?classified?2Tools for Identifying Organisms A dichotomous key is a detailed list ofidentifying characteristics that includesscientific names.

SectionSection CheckCheck2Question 1is the two word naming system usedto name various organisms.AnswerThe answer is binomial nomenclature. Thistwo-word name is an organism’s species.

SectionSection CheckCheck2Question 2is the evolutionary history of anorganism.AnswerThe answer is phylogeny. Scientists studyfossils, heredity information, and early stagesof development to determine an organism’sphylogeny.

SectionSection CheckCheck2Question 3What is this table an example of?

SectionSection CheckCheck2AnswerThe answer is dichotomous key. A dichotomouskey is a detailed list of identifying characteristicsthat include scientific names.

CellCell StructureStructure3Viewing Cells The first microscope was made by a Dutchoptometrist. He put two magnifying glasses togetherin a tube and got an image that was largerthan the image that was made by eitherlens alone.

CellCell StructureStructure3Viewing Cells In the mid 1600s, Antonie van Leeuwenhoek,a Dutch fabric merchant, made a simplemicroscope with a tiny glass bead for a lens. These crude early microscopes eventuallyled to the types of microscopes thatscientists use today.

CellCell StructureStructure3Development of the Cell Theory In 1665, Robert Hooke cut a thin slice ofcork and looked at it under his microscope. To Hooke, the cork seemed to be made upof empty little boxes, which he named cells.

CellCell StructureStructure3Development of the Cell Theory In the 1830s, Matthias Schleiden used amicroscope to study plant parts. He concluded that all plants are madeof cells. Theodor Schwann, after observing manydifferent animal cells, concluded that allanimals also are made up of cells.

CellCell StructureStructure3Development of the Cell Theory Several years later, Rudolf Virchowhypothesized that cells divide to formnew cells. Virchow proposed that every cell camefrom a cell that already existed.

CellCell StructureStructure3Development of the Cell Theory His observations and conclusions andthose of others are summarized in thecell theory.

CellCell StructureStructure3Cellular Organization Scientists have found that cells can beseparated into two groups. Cells withoutmembrane-boundstructures arecalledprokaryotic (prohkayr ee AH tihk)cells.

CellCell StructureStructure3Cellular Organization Cells with membrane-bound structures arecalled eukaryotic (yew kayr ee AH tihk) cells. All cells mustconstantly take innutrients, store,produce, andbreakdownsubstances, and takein and use energy.

CellCell StructureStructure3Cell Wall The cells of plants, algae, fungi, and mostbacteria are enclosed in a cell wall. Cell walls are tough, rigid outer coveringsthat protect cells and give them shape. A plant cell wall ismostly made up ofa carbohydratecalled cellulose.

CellCell StructureStructure3Cell Wall Cell walls also may contain pectin and lignin. Pectin aids in cell growth, development,defense, and strength. Lignin is a compound that makes cellwalls rigid.

CellCell StructureStructure3Cell Membrane The protective layer surrounding every cellis the cell membrane. The cell membrane regulates interactionsbetween the cell and its environment. The cell membraneallows nutrients tomove into the cell,while wasteproducts leave.

CellCell StructureStructure3Cytoplasm Cells are filled with a gelatinlike substancecalled cytoplasm (SI toh pla zuhm) thatconstantly flows inside the cell membrane. Most of a cell’s life processes occur in thecytoplasm.

CellCell StructureStructure3Cytoplasm Throughout the cytoplasm is a frameworkcalled the cytoskeleton, which helps the cellmaintain or change its shape and enablessome cells to move. The cytoskeleton is made up of thin, hollowtubes of protein and thin, solid protein fibers.

CellCell StructureStructure3Manufacturing Proteins One substance that takes part in nearly everycell activity is protein. Proteins are part of cell membranes and areneeded for chemical reactions that take placein the cytoplasm.