Core Theme: Evolu(on accts for unity/diversity of life

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1 Negative feedback A Enzyme 1 B Excess D blocks a step D D D C Enzyme 2 Enzyme 3 D (a) Negative feedback W Enzyme 4 Positive feedback + X Enzyme 5 Excess Z stimulates a step Z Z Z Y Enzyme 6 Z (b) Positive feedback Core Theme: Evolu(on accts for unity/diversity of life Nothing in biology makes sense except in the light of evolu8on Theodosius Dobzhansky Evolu8on Unifies biology at different scales of size throughout the history of life on Earth All biological diversity seen on Earth is due to evolu8onary processes Organizing the Diversity of Life ~1.8 million species iden8fied and named to date Thousands more are iden8fied each year Es8mates of the total number of species Range from 10 million to over 100 million 1

2 Taxonomy Grouping Species: The Basic Idea Branch of biology that names and classifies species Into groups of increasing breadth Linnean Classifica8on System Domain Carl Linnaeus 1700 s Kingdom Phylum Class Order Family Genus Species Ursus americanus (American black bear) Species Genus Family Order Class Phylum Kingdom Domain Ursus Ursidae Carnivora Mammalia Chordata Animalia Eukarya The Three Domains of Life Three domain system is currently used Replaces the old five kingdom system Domain Bacteria and Domain Archaea Comprise the prokaryotes Domain Eukarya Includes all eukaryo8c organisms 2

3 Fig (a) DOMAIN BACTERIA (b) DOMAIN ARCHAEA (c) DOMAIN EUKARYA Protists Kingdom Plantae Kingdom Fungi Kingdom Animalia Three Eukaryo(c Kingdoms Domain Eukarya Includes three mul8cellular kingdoms: Plantae Fungi Animalia Single celled Kingdom Pro8sta Other eukaryo8c organisms were formerly grouped kingdom Pro8sta Now o[en grouped into many separate kingdoms Protists Kingdom Plantae Kingdom Fungi (c) DOMAIN EUKARYA Kingdom Animalia 3

4 Science Two main forms of inquiry in study of nature Derived from La8n and means to know Inquiry Search for informa8on and explana8on Two main types of scien8fic inquiry: Discovery science Describes nature Naturalists Hypothesis based science Explains nature Discovery science Discovery Science Describes natural structures and processes Based on observa8on And the analysis of data Typically large amounts of data Induc(ve reasoning O[en used in discovery science Draws conclusions through the logical process of induc8on Repeat specific observa8ons can lead to important generaliza8ons Of 10,000 organisms observed, all are made of cells, therefore all organisms are made of cells Types of Data Data (plural!) Are recorded observa8ons or items of informa8on Data fall into two categories Qualita+ve Descrip8ons rather than measurements Quan+ta+ve Recorded measurements Which are some8mes organized into tables and graphs 4

5 Observa8ons Lead us to ask ques8ons And propose hypothe8cal explana8ons Hypothesis Called hypotheses Hypothesis Based Science Is a tenta8ve answer to a wellframed ques8on Predicted outcome Scien8fic hypothesis leads to predic8ons Testable by observa8on or experimenta8on Hypothesis Based Science For example, Observa8on: Your flashlight doesn t work Ques8on: Why doesn t your flashlight work? Hypothesis 1: The baderies are dead Hypothesis 2: The bulb is burnt out Both these hypotheses are testable 5

6 Observations Question Hypothesis #1: Dead batteries Hypothesis #2: Burnt-out bulb Prediction: Replacing batteries will fix problem Prediction: Replacing bulb will fix problem Test prediction Test prediction Test falsifies hypothesis Test does not falsify hypothesis Deduc(on: If If Then Logic of Hypothesis Based Science Deduc(ve reasoning Uses general premises to make specific predic8ons Reverse of induc8ve reasoning For example If organisms are made of cells (premise 1) and humans are organisms (premise 2) Then humans are composed of cells (deduc8ve predic8on) A Closer Look at Hypotheses in Scien(fic Inquiry Hypotheses Must be testable and falsifiable Does organism X require oxygen to survive? Does canned dog food make dogs happy? Hypothesis based science O[en makes use of two or more alterna8ve hypotheses Failure to falsify a hypothesis does not prove that hypothesis For example You replace your flashlight bulb, and it now works This supports the hypothesis that your bulb was burnt out But does not prove it Perhaps the first bulb was inserted incorrectly 6

7 The Myth of the Scien(fic Method Steps of Scien8fic Method Ini8al observa8ons/background research Develop testable ques8on Hypothesis Experiment Collect data Conclusions The scien+fic method is an idealized process of inquiry Nonetheless s8ll legi8mate Hypothesis based science Based on the textbook scien8fic method above But rarely follows all the ordered steps Discovery science Has made important contribu8ons with very lidle dependence on the socalled scien8fic method Case Study: Inves(ga(ng Mimicry in Snake Popula(ons Many poisonous species are brightly colored Warns poten8al predators Mimics Harmless species that closely resemble poisonous species Henry Bates Hypothesized that this mimicry evolved in harmless species as an evolu8onary adapta8on That reduces their chances of being eaten Case Study: Inves(ga(ng Mimicry in Snake Popula(ons This hypothesis was tested with the poisonous eastern coral snake And its mimic the nonpoisonous scarlet kingsnake Both species live in the Carolinas But the kingsnake is also found in regions without poisonous coral snakes If predators inherit an avoidance of the coral snake s colora8on, Then the colorful kingsnake will be adacked less o[en in the regions where coral snakes are present 7

8 Case Study: Inves(ga(ng Mimicry in Snake Popula(ons Scarlet kingsnake (nonpoisonous) Key Range of scarlet kingsnake only Overlapping ranges of scarlet kingsnake and eastern coral snake North Carolina Eastern coral snake (poisonous) South Carolina Scarlet kingsnake (nonpoisonous) Field Experiments with Ar(ficial Snakes To test this mimicry hypothesis Researchers made hundreds of ar8ficial snakes: An experimental group resembling kingsnakes A control group resembling plain brown snakes (a) Artificial kingsnake Equal numbers of both types were placed at field sites Including areas without poisonous coral snakes (b) Brown artificial snake that has been attacked Field Experiments with Ar(ficial Snakes Scien8sts retrieved the ar8ficial snakes and counted bite or claw marks The data fit the predic8ons of the mimicry hypothesis: Ringed snakes were adacked less frequently in the geographic region where coral snakes were found RESULTS 100 Percent of total attacks on artificial snakes A[er four weeks % 83 % Artificial kingsnakes Brown artificial snakes % Coral snakes absent 16 % Coral snakes present 8

9 Designing Controlled Experiments Controlled experiment Compares an experimental group (the ar8ficial kingsnakes) With a control group (the ar8ficial brown snakes) Only the variable of interest (the color padern of the ar8ficial snakes) Differs between the control and experimental groups A controlled experiment means that Control groups are used to cancel the effects of unwanted variables A controlled experiment does not mean that All unwanted variables are kept constant Confounding variables Limita(ons of Science In science Observa8ons and experimental results must be repeatable Peer review process is a fundamental part Science cannot support or falsify supernatural explana8ons Which are outside the bounds of science Not testable Theories in Science In the context of science, a theory is: Broader in scope than a hypothesis General, and can lead to new testable hypotheses Supported by a large body of evidence in comparison to a hypothesis Supported repeatedly Only has to be unsupported once Differs from use of theory outside of science Not conjecture 9

10 Model Building in Science Models Representa8ons of natural phenomena and can take the form of: Diagrams Three dimensional objects Computer programs Mathema8cal equa8ons Used to Mimic process too complex or large to control Predict future outcomes May be evaluated for validity by ability to predict outcomes from past From body From lungs Right atrium Left atrium Right ventricle Left ventricle To lungs To body Science, Technology, and Society The goal of science is To understand natural phenomena The goal of technology is To apply scien8fic knowledge for some specific purpose Science and technology are interdependent Biology is marked by discoveries, while technology is marked by inven8ons Radiowaves vs. radios 10

11 Science, Technology, and Society The combina8on of science and technology has drama8c effects on society The discovery of DNA by James Watson and Francis Crick Allowed for advances in DNA technology Such as tes8ng for hereditary diseases Also can create controversy Ethical issues can arise from new technology But have as much to do with poli8cs, economics, and cultural values as with science and technology You should now be able to: 1. Briefly describe the unifying themes that characterize the biological sciences 2. Dis8nguish among the three domains of life, and the eukaryo8c kingdoms 3. Dis8nguish between the following pairs of terms: discovery science and hypothesis based science, quan8ta8ve and qualita8ve data, induc8ve and deduc8ve reasoning, science and technology 11