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What is Life?

– Living organisms:– are composed of cells– are complex and ordered– respond to their environment– can grow and reproduce– obtain and use energy– maintain internal balance– allow for evolutionary adaptation

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Fig. 1.1

mitochondria

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Fig. 1.1(continued)

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The Nature of Science

Science aims to understand the natural world through observation and reasoning.

Science begins with observations, therefore, much of science is purely descriptive.

Science uses both deductive and inductive reasoning.

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The Nature of Science

Deductive reasoning uses general principles to make specific predictions.

Inductive reasoning uses specific observations to develop general conclusions.

Theory(Hypotheses)

Experiments

Observations,Previous Research

HypothesesDeduction(general to specific)

Induction(specific to general)

The Scientific Way of Knowing:Inductive and Deductive approaches define the Scientific Method

Often, scientific investigations starts with Induction and moves to Deduction

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A scientific theory

- is a body of interconnected concepts

- is supported by a large fundament of evidence and scientific reasoning (usually the testing of numerous hypotheses)

- expresses ideas of which we are most certain

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Charles Darwin

evolution: modification of a species over generations

-“descent with modification”

natural selection: individuals with superior physical or behavioral characteristics are more likely to survive and reproduce than those without such characteristics

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One Piece of Darwin’s Induction

Similarity of related species

- Darwin noticed variations in related species living in different locations

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Another piece of Darwin’s Induction

Population growth vs. availability of resources

-population growth

is geometric

-increase in food

supply is arithmetic

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Evolutionary Deductive Evidence

Fossil record

- New fossils are found all the time

- Earth is older than previously believed

Mechanisms of heredity

- Early criticism of Darwin’s ideas were resolved by Mendel’s theories for genetic inheritance.

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• Mutations and their various combinations (hence new varieties) do not arise because they are needed -- they arise by chance.

• Mutations merely furnish random raw material for evolution, and rarely, if ever determine the course of the process.

• Natural selection is the differential reproduction of genotypes (genes). Cumulative selection is a powerfully constructive force, caught in action many times by evolutionary biologists.

• Evolution is, quite simply, the change in the genetic composition of a population over time.

An Evolution by Natural Selection Primer

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More Evolutionary Deductive Evidence

Comparative anatomy

- Homologous structures have same evolutionary origin, but different structure and function.

- Analogous structures have similar structure and function, but different evolutionary origin.

Homologies of Religions and Languages

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Homologous Structures

Homology vs. Analogy

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Homology vs. Analogy

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Pterosaur

Bat

Bird

Figure from the National Center for Science Education

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More Evolutionary Deductive Evidence

Molecular Evidence

- Our increased understanding of DNA and protein structures has led to the development of more accurate phylogenetic trees.

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The Homeodomain, a protein structure found in a large family ofTranscription Factors, and responsible for binding DNA and regulating target genes

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Fig. 1.14

The 3 Domains of Life on Earth

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Z-X Luo et al. Nature 476, 442-445 (2011) doi:10.1038/nature10291

Holotype specimen of Juramaia sinensis, Beijing Museum ofNatural History (BMNH) PM1343B.

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Unifying Themes in Biology

Cell theory

- All living organisms are made of cells, and all living cells come from preexisting cells.

Molecular basis of inheritance

- Genes, which control living organisms and are passed from one generation to the next, are found in DNA.

DeoxyriboNucleicAcid

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Unifying Themes in BiologyCells - information processing systems- Cells process information stored in DNA as well as information received

from the environment.

Emergent properties- New properties are present at one level of organization that are not

seen in the previous level.

Evolutionary change

- Living organisms have evolved from the same origin event. The diversity of life is the result of evolutionary change.

Evolutionary conservation

- Critical characteristics of early organisms are preserved and passed on to future generations.

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Unifying Themes in Biology

Structure and Function

-The function of a molecule is dependent on its structure.

-The structure of a molecule can often tell us about its function.

The DNA Polymerase IIIBeta Subunit (E. coli) with bound DNA

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