생명체의 특성 What is life ? 생물학개론 2주차 강의 It is difficult to come up with a single definition of life.

생명체란 무엇인가? 협동적으로 작용하고 여러 특성 (5가지)을 나타내는 구조들의 집합체 All living things exhibit five characteristics in combination. 1. 구성 (Organization) 2. 에너지 사용과 대사 (Energy Use & Metabolism) 3. 항상성 유지 (Maintenance of Homeostasis) 4. 생식, 생장과 발생 (Reproduction, Growth & Development) 5. 자극감수와 적응 (Irritability & Adaptation) We currently distinguish living from nonliving based upon five characteristics. Living organisms must possess all five characteristics. Inanimate objects may possess one or more of these characteristics but not all.

생명체의 특성 1. Organization (구성) Chemical (atom -> molecule -> macromolecule) Organelle (세포소기관) Cell (세포); 생명체의 기본단위 Tissue (조직); 협동적으로 작용하는 특정세포의 집합 Organ (기관); 기능을 수행하는 조직의 집합체 Organ system (기관계); 함께 작용하고 물리적 화 학적으로 연결된 기관 Multicellular organism (다세포 생물) All living things exhibit organization: Chemical level - atoms combine to make molecules; molecules combine to make macromolecules. Organelle (a membrane bound structure within a complex cell) level. * Cellular level - smallest level of organization that exhibits all characteristics of life. This is the highest level of organization exhibited by some organisms (Ameba, Paramecium, Euglena, bacteria, algae). Tissue level - a collection of cells that perform a common function. Organ level - a collection of tissues that perform a common function. Organ system level - a collection of organs that perform a common function. Multicellular organism - a living individual composed of many organ systems.

Organization (구성) Biological organization beyond individual organisms Population (개체군): 같은 시간과 장소에 서식하는 둘 이상의 같은 종 two or more members of the same species living in the same place at the same time Community (군집): 특정 지역에 서식하는 다른 종의 집단 Populations of different species in a particular area Ecosystem (생태계): 한 지역의 생물과 무생물 The living and nonliving components of an area Biosphere (생물권): 생명을 지탱하는 지구의 일부와 그 속의 모든 생명체 The parts of the planet that can sustain life and the organisms that live there Organization also exists beyond the level of the individual organism. Population: two or more members of the same species living in the same place at the same time Community: Populations of different species in a particular area Ecosystem: The living and nonliving components of an area Biosphere: the parts of the planet that can sustain life and the organisms that live there

Organization (구성) 기관계 > 기관 > 조직 > 세포 > 소포체 (세포내 소기관) 구조와 기능은 밀접한 상관관계 구조가 파괴되면 기능 상실 (물리적 충격에 의한 수정란의 파괴) 기능이 파괴되면 구조 분해 (근육의 소실) Each level of biological organization exhibits emergent properties (출현형질) – 각 구성 단계에 따라 나타나는 기능과 작용 Emergent property - property not present at lower levels. Endothelial cells must aggregate in a specific way for them to transport blood. Ex. 모세혈관은 혈액을 운반 (각 내피세포는 이러한 기능이 없다)

에너지 사용과 대사 2. Energy Use & Metabolism Metabolism (대사) - 생명을 유지하는 세포 내 화학반응 biochemical reactions that acquire & use energy. Why do organisms need energy? to combat entropy (the tendency towards disorder) 무질서화 되는 엔트로피에 대항 to build new structures 새로운 구조 만듬 to repair/break down old structures 낡은 구 조를 수선 또는 분해 to reproduce 생식하는데 Organisms take in energy and transform it (by metabolism) to do many kinds of work Entropy = the natural tendency of matter to be disorganized.

에너지 사용과 대사 How do organisms obtain energy? By extracting energy from the environment Producers (생산자): 무생물에서 에너지 획 득 get energy from non-living sources Consumers (소비자): 다른 생명체에 의해 만들어진 영양분 섭취 get nutrients made by other organisms Decomposers (분해자): 죽은 생명체로부 터 영양분 섭취 get nutrients from dead organisms Organisms have several choices concerning how they obtain their energy from the environment. Producers get energy from non-living sources. An example would be plants that perform photosynthesis. Consumers (such as animals) obtain their nutrients from other organisms. Decomposers get their nutrients from dead organisms.

에너지 사용과 대사 대사 (metabolism) : 생명체를 유지하는 세포 내 화학반응. 엔트로피의 법칙 : 동화 : 합성 (Synthesize) 이화 : 분해 (Degrade) 엔트로피의 법칙 : 일정한 형태의 조직이나 질서를 유지하려면 에너지가 필요하다 Organisms obtain energy: * from the nonliving environment (sunlight or chemicals) - these organisms are called producers or autotrophs. * by eating other organisms - these organisms are called consumers or heterotrophs. * by eating dead organisms or their products [feces] - these organisms are called decomposers.

항상성 유지 3. Maintenance of Homeostasis Homeostasis (항상성) - 외부 환경은 급격하 게 변해도 세포 내 환경을 이루는 화학물질은 어 떤 일정한 범위 내에서 유지하려는 성질 the ability of an organism to maintain its internal environment despite conditions in the external environment. 항상성이 유지되지 않으면 죽음을 포함한 심각한 상 황을 초래한다. Ex. 사람의 체온은 항상 ~37ºC를 유지 체온이 오르면 땀을 흘린다. 체온이낮으면 오들오들 떤다 Inability to maintain homeostasis leads to illness or death of the organism. Ex. High body temperatures inactivate enzymes, so chemical reactions vital for life cannot occur.

생식, 성장과 발생 4. Reproduction, Growth & Development 생식: 자기와 동일한 개체를 만드는 것 Asexual reproduction (무성생식) - involves a single parent; progeny are genetically identical to the parent (한 부모, 자손은 유전적으로 어버이와 동일). Often used in unicellular organisms 단세포 생물에서 흔히 나타남 Sexual reproduction (유성생식) - involves 2 parents; progeny are genetically diverse (두 부모, 자손은 유전적 다양성을 가짐). Asexual reproduction is used by many unicellular organisms as well as some multicellular organisms such as plants which can also perform sexual reproduction.

생식, 성장과 발생 단세포생물: 무성생식 다세포생물: 무성생식, 유성생식 Is it essential for an individual to reproduce? 생식은 각 생명체에 필수적인가 Not necessarily . . . The population needs to be maintained 개체군 유지에는 필요 Organisms that successfully reproduce over several generations compose a species 몇 세대에 거쳐 성공적으로 생식하는 개체는 종을 이 룬다. No, but it is essential if a population is to survive for more than one generation.

자극에 대한 반응과 적응 5. Irritability & Adaptation Irritability (자극감응성) - immediate response to a stimulus. 자극에 대한 즉각적인 반응 생물체는 외부환경의 자극을 감지하고 적절한 대응을 한다. 자극에 대한 반응 즉각대응(Irritability) 적응(Adaptation): 오랜 시간에 걸쳐 나타나는 반응현상. 주어진 환경에서 성공적으로 생식하도록 자연선택(Natural selection): 향상된 생식력과 적응력 Irritability can be essential for survival (Venus flytrap captures a meal).

자극에 대한 반응과 적응 Adaptation (적응) - 생물이 주어진 환경에서 생존과 생식을 가능케 하는 유전적 행동이나 특징 an inherited behavior or characteristic that enables an organism to survive & reproduce. Over time, adaptations are modified by natural selection. 오랜 시간 동안 자연선택에 의해 적응은 변한다 Natural Selection (자연선택) - 물려받은 유전적 특징을 토대로 하고 있는 어떤 개체의 향상된 생식력과 적응력 the enhanced survival & reproductive success of individuals whose inherited traits better adapt them to a particular environment. Adaptations develop over time. Examples: Camouflage is an adaptation to acquire food or escape predation. Picture of Adder snake. Leaf curling is an adaptation to minimize wind damage.

생명의 진화와 다양성 A. 진화 (Evolution) Genetic change within a population 개체군 내에서의 유전적 변화 Natural selection is one of the driving forces 자연선택이 주요 요인 Mutations in DNA provide genetic variation upon which natural selection acts 돌연변이는 자연선택이 작용하는 유전적 변이를 제공 An ongoing process 생명은 항상 변한다 Evolution is a continual process that relies on a variety of forces including natural selection.

생명의 진화와 다양성 B. Biodiversity (생물다양성) Life on earth is diverse, yet similar. Taxonomists place organisms into groups based upon evolutionary relationships. 진화관계에 따라 생명체를 분류 Broadest, most inclusive group (taxon) is the domain. 가장 큰 분류는 역 Domain역  Kingdom계  Phylum or Division문  Class강  Order목  Family과  Genus속  Species종 Genus & species refer to the organism’s binomial (name). 생명체의 이름은 종과 속, 2개의 용어로 Biodiversity - the different types of organisms on earth. Similarity of life - all are composed of cells & have DNA as their genetic material. This suggests that all life evolved from a common ancestor.

생명의 진화와 다양성 The Three Domains: Bacteria 세균 - unicellular prokaryotes Archaea 고세균 - unicellular prokaryotes Eukarya 진핵생물- eukaryotes Kingdom Protista 원생생물 Kingdom Plantae 식물 Kingdom Fungi 균류 Kingdom Animalia 동물 Bacteria & Archaea: Prokaryotes lack nuclei & membrane-bound organelles. Some bacteria & archaea are autotrophic, while others are heterotrophic; have distinctive cell walls. Bacteria & Archaea differ from each other at the molecular level. Eukarya: Eukaryotes possess nuclei & membrane-bound organelles. Most are multicellular. Kingdom Protista - most are unicellular; some have cell walls; some are autotrophic, while others are heterotrophic. Kingdom Plantae - multicellular; have cell walls of cellulose; usually autotrophic; have complex organ systems. Kingdom Fungi - most multicellular; have cell walls of chitin; are heterotrophic (by absorption); have tissues. Kingdom Animalia - multicellular; no cell walls; are heterotrophic (by ingestion); have complex organ systems.

생명의 진화와 다양성 Human classification scheme: Domain Eukarya 진핵생물 Kingdom Animalia 동물계 – 오징어, 파리 Phylum Chordata 척삭동물문 Class Mammalia 포유강 – 쥐, 돼지 Order Primates영장목 – 오랑우탄, 침팬지 Family Hominidae 사람과 Genus & species Homo sapiens 사람

생명체의 연구 Scientists study life by using the scientific method. 과학적 방법으로 생명체를 연구 Hypothesis 가설 - 추리, 실험결과를 설명하는 잠정적인 설명 “an educated guess”; a tentative explanation of phenomena which is experimentally tested. Theory 이론, 학설 - 널리 받아들여지는 자연현상에 대한 설명 (아인슈타인 상대성 이론, 다윈의 진화론) a widely accepted explanation of natural phenomena; has stood up to thorough & continual testing. Law 법칙 - 어떤 조건에서 항상 일어나는 설명 (멘델의 분리 및 독립의 법칙) a statement of what always occurs under certain conditions. Theory - Einstein’s theory of relativity; Darwin’s theory of evolution. Laws - Mendle’s laws of independent assortment & segretation.

생명체의 연구 Validity can be influenced by 타당성 검증 : 표본수가 많을 수록 Sample size 실험대조의 고안 The appropriate use of controls 대조군은 검증하고자 하는 하나의 변이를 제외한 실험군처럼 취급 A control group is treated like the experimental group except for the one variable being tested 위약은 실험대조의 한 형태 Placebos are a form of control 이중맹검법 Use of double blind studies Well designed experiments compare an experimental group to a control group. Both groups are treated identically with exception of a single factor, or variable. Note: a large sample size helps ensure meaningful results. Interpretation of data has pitfalls. Experimental evidence may lead to multiple interpretations or misinterpretations.