Lecture 2
Life Science
Interconnected concepts, not unconnected facts
Developed over time
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
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
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
The Nature of Biology
How does evolution work?
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
Repeat
Evolution
Most important unifying concept
Explains diversity
Explains fossil record
Evolution
Defining theory of modern life science
Theodor Dobzhansky—”Nothing in biology makes sense, except in the light of evolution”
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 Selectionexplained 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 Selectionexplained 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
Natural Selection
2 step process
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
The Nature of Evolution
How does evolution work?
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
Repeat