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Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings

Chapter 1

Exploring Life

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What is life???

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Lifes basic characteristic is a high degree of order

Each level of biological organization has emergentproperties

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Concept 1.1: Biologists explore life from the

microscopic to the global scale

The study of life extends from molecules and cells to

the entire living planet

Biological organization is based on a hierarchy

of structural levels

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A Hierarchy of Biological Organization

1. Biosphere: all environments on Earth

2. Ecosystem: all living and nonliving thingsin a particular area

3. Community: all organisms in an ecosystem

4. Population: all individuals of a species in aparticular area

5. Organism: an individual living thing

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A Hierarchy of Biological Organization (continued)

6. Organ and organ systems: specialized bodyparts made up of tissues

7. Tissue: a group of similar cells

8. Cell: lifes fundamental unit of structure andfunction

9. Organelle: a structural component of a cell

10 Molecule: a chemical structure consisting ofatoms

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A Hierarchy of Biological Organization (continued)

11. Atoms

12. Elementary particles

13. Quarks

14. ??

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Two Main Forms of Cells

Characteristics shared by all cells:

Enclosed by a membrane

Use DNA as genetic information

Two main forms of cells:

Eukaryotic: divided into organelles; DNA innucleus

Prokaryotic: lack organelles; DNA notseparated in a nucleus

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MembraneCytoplasm

EUKARYOTIC CELL PROKARYOTIC CELLDNA

(no nucleus)Membrane

1 mOrganellesNucleus (contains DNA)

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The Three Domains of Life

At the highest level, life is classified into three

domains:

Bacteria (prokaryotes)

Archaea (prokaryotes)

Eukarya (eukaryotes)Eukaryotes include protists and the kingdoms

Plantae, Fungi, and Animalia

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Bacteria 4 m 100 m

0.5 m

Kingdom PlantaeProtists

Kingdom AnimaliaKingdom FungiArchaea

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Concept 1.4:

Evolutionaccounts for lifes unity anddiversity

The history of life is a saga of a changing Earthbillions of years old