and just what is science? how about this biology stuff?

Transcription

1 Welcome to Life on Earth! Rob Lewis The Science of Biology Themes and just what is science? how about this biology stuff? 2 1

2 The Process Of Science No absolute truths in science Our understanding about nature comes from ability to observe. Science has levels of confidence in explanations for natural phenomena Assumes a rational universe 3 The Process Of Science 0 Scientists use two main approaches to learn about nature Discovery Science observe and describe, then use inductive reasoning to draw general conclusions Hypothesis-Based Science - attempt to explain observations by forming and testing hypotheses 4 2

3 Characteristics: Scientific Theory Broad in scope, generate hypotheses Supported by massive body of evidence Constantly challenged through testing of the specific, falsifiable hypotheses they generate. Examples: Einstein s Theory of General Relativity Darwin s Theory of Evolution Lemaître s Big Bang Theory of the Universe 5 Hypothesis-based Science 0 Hypothesis-based science involves: Observations, questions, hypotheses as tentative answers to questions Deductions leading to predictions, and then tests of predictions to determine if a hypothesis is falsifiable 6 3

4 What is a hypothesis? A a tentative or educated guess at an answer to a problem or question being asked. A good hypothesis makes predictions that can be tested. Hypothesis-based science uses deductive reasoning that flows from a general premise to a specific premise. Important point (aspect) of this process is the deduction can be tested One experiment can t prove or disprove! 7 Hypothesis-based Science Two important qualities: A hypothesis must be testable. A hypothesis must be falsifiable If a hypothesis is correct, and we test it, then a particular outcome is expected 8 4

5 Scientific Method key steps: Make observations Ask questions about the observations: How? Why? When? Generate hypotheses; explanations of the phenomena, phrased to be testable. Derive predictions; logical, testable outcomes of the hypotheses use deductive reasoning Predictions take the form of: If X is true, then Y Test the predictions; determine if the predictions are supported (fail to falsify) or falsified A hypothesis becomes credible when repeated attempts to disprove it fail 9 Flow Diagram of the Scientific Method 10 5

6 Biology- What is it? 11 Biology: Scientific Study Of Life 0 Lump of coal Yeast Is it alive? How do we know? E. coli bacterium Ebola virus 12 6

7 Biology Nature is not neatly packaged Organisms (and their environments): natural systems chemistry and physics apply Biology: multidisciplinary science draws on the insights from other sciences. 13 What is Life? no simple, one-sentence definition recognize life by what living things do living organisms share common features or properties 14 7

8 Properties of Life 0 Complex levels of organization, ordered structures Regulate internal conditions Harvest and use energy Reproduce and evolve Grow and develop Respond to environmental stimuli 15 Organizational Hierarchy Life - a hierarchy of structural levels Successive levels show additional emergent properties 16 8

9 The hierarchy of Life 0 Organ systems complexity Organs Tissues Cells Organelles Molecules 17 Emergent Properties Life s basic characteristic = a high degree of order fight entropy Biological organization - based on structural level hierarchies, each builds on the level below Each step upward novel properties emerge Emergent properties come from component interactions Emergent properties reflect importance of structural arrangement and organization 18 9

10 Reductionism Complex organization of life presents a dilemma: cannot fully explain a higher level of organization by breaking into parts (stops functioning!) cannot analyze complex system (organism or cell) without taking apart Reductionism Reducing complex systems to simpler components Balanced by objective of understanding emergent properties. 19 size Unity and Diversity Biology think of it as having two dimensions: Vertical - covers the size scale from atoms to the biosphere Horizontal - encompasses the diversity of life (includes organisms throughout history of life - 4 billion years!) Life diversity progress 20 10

11 Life Diversity Currently -- ~ 1.5 million species over 280,000 plants 50,000 vertebrates over 750,000 insects. Thousands added each year Total life diversity estimates --5 million to over 30 million species 21 Unity Underlying the diversity of life is a striking unity, especially at the lower levels of organization. universal genetic DNA language unites organisms unity is evident in many details of eukaryotic cell structure Fig

12 Unity and Diversity Evolution -- key to understanding biological diversity The evolutionary connections explain unity and diversity of life Descent with modification accounts for both the unity and diversity of life. In many cases, features shared by two species are due to their descent from a common ancestor. Differences are due to modifications by natural selection modifying the ancestral equipment in different environments. Evolution -- core theme of biology - a unifying thread 23 Taxonomy A system for organizing, classifying & naming living things. Primary concerns of taxonomy are classification, nomenclature, and identification. A way to communicate 24 12

13 Old School: Five Kingdoms Monera ( alone ) Bacteria Fungi Archaea Protista ( first ) Plantae Animalia 25 The five-kingdom system became the standard until molecular biology techniques were used to develop the Domain system. Fig Traditional Whittaker system of classification 26 13

14 Classification- some notes Prokaryote vs Eukaryote Linnaean classification Kingdom phylum class order family genus species (King Phillip Came Over For Good Spaghetti) Taxonomy: Old school five kingdoms New and improved three domains 27 Levels of Classification Domain Phylum or Division Class Order Family Genus species 28 14

15 Domains a new Idea! Developed after the five-kingdom system Eubacteria -true bacteria, peptidoglycan Archaea odd bacteria that live in extreme environments, high salt, heat, etc Eukarya- have a nucleus, & organelles 29 Example Classification (Notice a kingdom is inclusive, and genus and species are less inclusive...) 30 15

16 New School: Three Domains Bacteria Monera Archaea Monera Eukarya (eukaryotes) Plantae Animalia Fungi Protista The Domains Bacteria & Archaea = prokaryotes 31 The Domain system was developed by Dr. Woese. The basis of the Domain system is the rrna sequence information

17 Nomenclature Binomial (scientific) nomenclature Genus Bacillus, always capitalized species - subtilis, lowercase Both italicized or underlined Bacillus subtilis (B. subtilis) 33 Identification The process of discovering and recording the traits (physical, biochemical, genetic) of organisms, thereby, placing them in a taxonomic scheme

18 Evolution- what about it? 0 Charles Darwin - theory of evolution by natural selection, his book presented two important concepts: Species evolved from ancestors, and there was modification in the process or, as Darwin stated, descent with modification. Natural selection occurs as heritable variations are exposed to environmental factors that favor the reproductive success of some individuals over others