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The Science of Biology

Chapter 1

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Outline

• Properties of Life• Hierarchical Organization• Reasoning• Scientific Theory• Darwin

– Natural Selection– Post Darwin Evidence

• Unifying Themes of Science

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Properties of Life

• Basic characteristics of living organisms– cellular organization– order– sensitivity– growth, development, and reproduction– energy utilization– evolutionary adaptation– homeostasis

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Hierarchical Organization

• Cellular level– molecule

organelles cells

• Organismal level– tissues

organs organ systems

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Hierarchical Organization

• Populational level– population

species biological community

ecosystem– Emergent properties

Novel properties that arise at each higher level

– Biosphere

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The Nature of Science

• Much of the Biological science is descriptive– Biodiversity– Human Genome

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Reasoning

• Inductive reasoning– Use specific observations to construct

general principles (dogs, cats, horses and humans all have mammary glands. Therefore they all are mammals)

• Deductive reasoning– Apply general principles to predict specific

results (if-than reasoning; if whales, dolphins and seals are considered mammals than they must have mammary glands)

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How Science Is Done

• All science begins with an observation.– A hypothesis is a suggested explanation

that accounts for an observation. An experiment is used to test a

hypothesis, and/or eliminate one or more multiple hypotheses.

In a controlled experiment, all variables, but one, are kept constant.

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How Science Is Done

• Predictions should be developed before the experiment is conducted in order to test the validity of the hypothesis.

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Theories

• A theory is:– a proposed explanation for a natural

phenomenon.– the body of interconnected concepts,

supported by scientific reasoning and experimental evidence.

solid ground of science

• A theory is NOT a guess.

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Research

• Basic research is used to extend the boundaries of current knowledge, and provides the scientific foundation used in applied research.

– Results undergo peer review in scientific journals.

Results must be reproducible.

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Scientific Inquiry with Charles Darwin

• Served as naturalist on mapping expedition around coastal South America.

– Argued operation of natural laws produced change over time, evolution.

explained by natural selectionspecies are not immutable

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Charles Darwin

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Darwin’s Evidence

• Fossils of extinct organisms (armadillos) were similar to modern species.

• Characteristics of similar species varied from place to place.

– gradual change of organismal lineages organisms on young volcanic islands

resembled those on mainland coast

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Darwin and Malthus

• Thomas Malthus (Essay on the Principle of Population) pointed out populations of organisms tend to increase geometrically.

– Unchecked populations should lead to population explosions, but most remain fairly constant between years.

Only a limited number of individuals survive.

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Geometric and Arithmetic Progression

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Darwin and Malthus

• Darwin suggested individuals with superior physical or behavioral attributes are more likely to survive and reproduce than those without such attributes.

– Selection artificial - domesticated breeds natural - organisms in the wild

• Alfred Russel Wallace independently and almost simultaneously developed same idea.

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Post-Darwin Evolution Evidence

• Fossil record– Earth is older than previously believed

• Mechanisms of heredity– modern genetics

molecular evidencemolecular clocksphylogenetic trees

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Post-Darwin Evolution 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.

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Homology Among Vertebrate Limbs

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Unifying Themes of Science

• Cell theory– All living organisms are made of cells, and

all living cells come from other living cells.• Molecular basis of inheritance

– DNA encodes genes which make-up and control living organisms.

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Unifying Themes of Science

• Evolutionary change– Life-forms have evolved varying

characteristics to adapt to varied environments.

• Evolutionary conservation– Some characteristics of earlier organisms

are preserved and passed on to future generations.

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Summary

• Properties of Life• Hierarchical Organization• Reasoning• Scientific Theory• Darwin

– Natural Selection– Post Darwin Evidence

• Unifying Themes of Science