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1、Studying Life,1 Studying Life,1.1 What Is Biology?1.2 How Is All Life on Earth Related?1.3 How Do Biologists Investigate Life?1.4 How Does Biology Influence Public Policy?,1.1 What is Biology?,Biology:the scientific study of living things.Living things:all the organisms descended from a single-celle
2、d ancestor.,1.1 What is Biology?,Characteristics of living organisms:Consist of one or more cells(living cell theory)Contain genetic information(DNA)Use genetic information to reproduce themselves(replicate)Are genetically related and have evolvedCan convert molecules from their environment into new
3、 biological molecules(metabolism)Extract energy from the environment and use it to do biological work(metabolism)Regulate their internal environment(homeostasis),1.1 What is Biology?,Evolution:a central theme of biology(but we wont cover in this class.),but it can be summarize as follow:Living syste
4、ms evolve through differential survival and reproduction.The processes of evolution have generated the enormous diversity of life on Earth.,1.1 What is Biology?Consist of one or more cells(living cell theory),Unicellular organisms:a single cell carries out all the functions of life.Multicellular org
5、anisms:made of many cells that are specialized for different functions.,Biology:the scientific study of living things.Living things:all the organisms descended from a single-celled ancestor.,1.1 What is Biology?Consist of one or more cells(living cell theory),The study of cells was made possible by
6、the invention of microscopes(tomorrow s lab.)Robert Hooke in the 1600s described repeating units of plant material as cells.,1.1 What is Biology?,Cell Theory:(Schleiden and Schwann 1838)Cells are the basic structural and physiological units of all living organisms.Cells are both distinct entities an
7、d building blocks of more complex organisms.All cells come from preexisting cells.All cells are similar in chemical composition.Most of the chemical reactions of life occur within cells.Complete sets of genetic information are replicated and passed on during cell division.,1.1 What is Biology?,Evolu
8、tion:change in the genetic makeup of biological populations through time.Charles Darwin proposed that all living organisms are descended from a common ancestor by the mechanism of natural selection.Humans select for desired traits when breeding animals.Darwin postulated that natural selection could
9、occur through differential survival and reproductive success.Traits that increase the probability that the organism will survive and reproduce will become more common in the population.Natural selection and other evolutionary processes(e.g.,sexual selection and genetic drift)lead to adaptation.,1.1
10、What is Biology?Contain genetic information(DNA),Genome:sum total of all the DNA in a cell.DNA:the information that is passed from parent to daughter cells.All cells in a multicellular organism have the same genome.DNA consists of repeating subunits called nucleotides.Gene:a specific segment of DNA
11、that contains information for making a protein.Mutations are alterations in the nucleotide sequence.,1.1 What is Biology?Metabolism,Organisms acquire nutrients from their environment.Nutrients supply energy and materials for biochemical reactions.Some reactions break nutrient molecules into smaller
12、units,releasing energy for work.Examples of cellular work:Movement of molecules,or the whole organismSynthesis-building new complex molecules from smaller chemical unitsElectrical work of information processing in nervous systems,1.1 What is Biology?Metabolism(single cell),Metabolism,or metabolic ra
13、te:the sum total of all chemical transformations and other work done in all the cells of an organism.The reactions are integrally linked the products of one are the raw materials of the next.,1.1 What is Biology?Metabolism(multicellular),Multicellular organisms have an internal environment that is n
14、ot cellular.Their cells are specialized or differentiated,and organized into tissues;tissues are organized into organs.Organ systems are groups of organs with interrelated functions.,1.1 What is Biology?,Living organisms also interact:Populations are groups of individuals of the same species that in
15、teract with one another.A community consists of populations of all the species that live in the same area and interact.Communities plus their abiotic environment constitute an ecosystem.,Figure 1.6 Biology Is Studied at Many Levels of Organization(Part 1),1.1 What is Biology?,Individuals may compete
16、 with each other for resources;Or they may cooperate,e.g.,in a termite colony.Plants also compete for light and water,and many form complex partnerships with fungi,bacteria,and animals.The interactions of plant and animal species are major evolutionary forces that produce specialized adaptations.Spe
17、cies interactions with one another and with their environment is the subject of ecology.,1.2 How Is All Life on Earth Related?,Life arose from nonlife about 3.8 billion years ago when interacting systems of molecules became enclosed in membranes to form cells,1.2 How Is All Life on Earth Related?,Li
18、fe arose by chemical evolution.Molecules that could reproduce themselves were critical.Biological molecules were then enclosed in membranes,forming cells.For 2 billion years,life consisted of single cells called prokaryotes.These cells were in the oceans,protected from UV radiation.There was little
19、or no oxygen(O2)in the atmosphere,and hence no protective ozone(O3)layer.,1.2 How Is All Life on Earth Related?,Photosynthesis evolved about 2.5 billion years ago.This process transforms sunlight energy into biological energy.Early photosynthetic cells were probably similar to cyanobacteria.,1.2 How
20、 Is All Life on Earth Related?,Consequences of photosynthesis:O2 accumulated in the atmosphereAerobic metabolism began Ozone layer formed,which allowed organisms to live on land,Eukaryotic cells evolved from prokaryotes.These cells have intracellular compartments called organelles with specialized c
21、ellular functions.The nucleus contains the genetic information.,1.2 How Is All Life on Earth Related?,Some organelles probably originated by endosymbiosis:when cells ingested smaller cells.Mitochondria(generate cells energy)and chloroplasts(conduct photosynthesis)could have originated when prokaryot
22、es were ingested by larger eukaryotes.,Multicellular organisms arose about 1 billion years ago.Cellular specialization:Cells became specialized to perform certain functions.,1.3 How Do Biologists Investigate Life?,Biologists use many methods to expand our understanding of life.Observation:improved b
23、y new technologiesExperimentation,1.3 How Do Biologists Investigate Life?,ObservationsQuestionsHypothesesPredictionsTesting,The scientific method(hypothesisprediction(HP)method):,1.3 How Do Biologists Investigate Life?,Distinguishing science and nonscience:Scientific hypotheses must be testable,and
24、have the potential of being rejected.Science depends on evidence that comes from reproducible and quantifiable observations.,1.4 How Does Biology Influence Public Policy?,Biological knowledge allows advances in human pursuits such as medicine and agriculture.These advancements can raise ethical and policy questions.,1.4 How Does Biology Influence Public Policy?,Biological knowledge contributes to our understanding of human influences on our environment.Biologists are called on to advise governments making policy decisions.,
