Lecture 2
Life Science
 Interconnected concepts, not unconnected facts
 Developed over time
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 Evolution: living things change with time
 Inheritance: living things store and use information
Life Science
 Evolution: living things change with time
 Inheritance: living things store and use energy
 DNA
 RNA
 Cells: basic unit of life
Key Interconnected Concepts
 Raw Materials and Energy: living things are made up of the same stuff, get energy from an
external source
 Thermodynamics: living things obey the same physical laws as everything else in the universe
Key Interconnected Concepts
 Diversity: life exists in different forms, based on some basic patterns
 Interaction and Dependence: constant interaction between organisms and their
environment—life doesn’t occur in a vacuum
Two Basic Theories
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Cell Theory
Evolution Theory
Backed by several lines of evidence
Backed by different types of evidence
Cell Theory
 All living things are made of cells
 Cells are the smallest unit of life capable of all life processes
 New cells come into existence only from division of preexisting cells
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Cell Theory
Basic rules
Allow for much variation or diversity in shapes, functions, environments
Sizes
Numbers
Arrangement
Cell Theory
Cells: unicellular or multicellular organism
Tissues: cells of similar structure and function
Organs: different tissues working together
Organ systems
Multicellular organisms
 How does evolution work?
The Nature of Biology
 Individuals who, through chance, have more of a striped appearance are more likely to
survive
 These individuals, on average, leave more offspring
 This increases the frequency of this characteristic in the population
 R e pe a t
Evolution
 Most important unifying concept
 Explains diversity
 Explains fossil record
 Defining theory of modern life science
Evolution
 Theodor Dobzhansky—”Nothing in biology makes sense, except in the light of evolution”
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Darwin and Evolution
1-nonconstancy of species
2-common descent
3-gradualness of evolution
4-multiplication of species (diversity)
5-natural selection
Natural Selection
Part of theory of evolution
Most commonly encountered aspect
Survival of the fittest
Process of elimination
Darwin’s Natural Selection
explained by Ernst Mayr
Fact 1—every population has such high fertility that its size would increase exponentially if not
constrained
 Fact 2—population sizes, except for temporary fluctuations remain stable over time
Darwin’s Natural Selection
explained by Ernst Mayr
 Fact 3: There are limited resources available
Natural Selection
 Fact 4—no two individuals are exactly the same
 Inference—Individuals differ from each other in the probability of survival
Natural Selection
 Fact 5—many of the differences are heritable
 Inference—over many generations, natural selection results in evolution
 2 step process
Natural Selection
 Step 1—production of variation: meiosis, random events of mate choice and fertilization
 Step 2—nonrandom aspects of survival and reproduction: survival selection and sexual
selection
Key Concepts
 Large amounts of time
 Natural selection
 Environment
 Restrains populations
 Site of competition
 How does evolution work?
The Nature of Evolution
 Individuals who, through chance, have more of a striped appearance are more likely to
survive
 These individuals, on average, leave more offspring
 This increases the frequency of this characteristic in the population
 R e pe a t