Chapter 1 Invitation to Biology Hsueh-Fen Juan 阮雪芬 Sep. 11, 2012

1.1 Life’s Levels of Organization  We understand life by thinking about nature at different levels of organization  Nature’s organization begins at the level of atoms, and extends through the biosphere  The quality of life emerges at the level of the cell

Making Sense of the World  Nature is everything in the universe except what humans have manufactured

A Pattern in Life’s Organization  Atoms Fundamental building blocks of all substances  Molecules Consisting of two or more atoms  Cell The smallest unit of life  Organism An individual consisting of one or more cells

A Pattern in Life’s Organization  Population Individuals of the same species in the same area  Community Populations of all species in the same area  Ecosystem A community and its environment  Biosphere All regions of the Earth where organisms live

Levels of Organization in Nature

Emergent Properties  Each level of organization in nature has emergent properties – a characteristic of a system that does not appear in any of its component parts

1.1 Key Concepts: Levels of Organization  We study the world of life at different levels of organization, which extend from atoms and molecules to the biosphere  The quality of “life” emerges at the level of cells

1.2 Overview of Life’s Unity  All living things have similar characteristics Continual inputs of energy and the cycling of materials maintain life’s complex organization Organisms sense and respond to change DNA inherited from parents is the basis of growth and reproduction in all organisms

Energy and Life’s Organization  Energy The capacity to do work  Nutrients Atoms or molecules essential in growth and survival that an organism cannot make for itself

Producers and Consumers  Producers Acquire energy and raw materials from the environment Make their own food (photosynthesis)  Consumers Cannot make their own food Get energy by eating producers and other organisms

Organisms Sense and Respond to Change  Organisms sense and respond to change both inside and outside the body by way of receptors  Receptor A molecule or cellular structure that responds to a specific form of stimulation

Homeostasis  Homeostasis Organisms use receptors to help keep conditions in their internal environment within ranges that their cells can tolerate

Organisms Grow and Reproduce  Organisms grow, develop, and reproduce using information in their DNA, a nucleic acid inherited from parents  Information encoded in DNA is the source of an individual’s distinct features (traits)

Same Materials, Many Products  20 amino acids are the building blocks used to build a great variety of proteins

1.2 Key Concepts: Life’s Underlying Unity  All organisms consist of one or more cells, which stay alive through ongoing inputs of energy and raw materials  All sense and respond to change; all inherited DNA, a type of molecule that encodes information necessary for growth, development, and reproduction

1.3 Overview of Life’s Diversity  Of an estimated 100 billion kinds of organisms that have ever lived on Earth, as many as 100 million are with us today

Scientific Naming  Each type of organism is given a two-part name that includes genus and species names  Genus A group of species that share unique features  Species Individuals that share one or more heritable traits and can interbreed (if sexually reproducing)

Classification Systems  Classification systems group species by their shared, heritable traits  All organisms are classified into three domains Bacteria, archaea, and eukaryotes Eukaryotes include plants, animals, protists and fungi

Comparison of Life’s Three Domains

1.3 Key Concepts: Life’s Diversity  Many millions of kinds of organisms, or species, have appeared and disappeared over time  Each kind is unique in some aspects of its body form or behavior

One-Way Flow of Energy and Cycling of Materials through an Ecosystem

1.4 An Evolutionary View of Diversity  A theory of evolution by natural selection is an explanation of life’s diversity

Variation and Mutation  Information encoded in DNA is the basis of traits an organism shares with others of its species  Mutations are the original source of variation in traits

Adaptation  Some forms of traits are more adaptive than others, so their bearers are more likely to survive and reproduce  Over generations, adaptive traits tend to become more common in a population; less adaptive forms of traits become less common or are lost

Evolution and Natural Selection  Evolution is change in a line of descent Traits that characterize a species can change over generations in evolving populations  Natural selection is an evolutionary process Differential survival and reproduction among individuals that vary in the details of their shared, heritable traits

1.4 Key Concepts: Explaining Unity in Diversity  Theories of evolution, especially a theory of evolution by natural selection, help explain why life shows both unity and diversity  Evolutionary theories guide research in all fields of biology

1.5 Critical Thinking and Science  Critical thinking is judging the quality of information  Science is limited to that which is observed Helps minimize bias in judgments by focusing on testable ideas about observable aspects of nature

A Guide to Critical Thinking

1.6 How Science Works  Scientists make and test potentially falsifiable predictions about how the natural world works

Observations, Hypotheses, and Tests  Researchers make observations, form hypotheses (testable assumptions), and make predictions about what might occur if the hypothesis is correct

A Scientific Approach

Research in Laboratory and Field

Systems Biology 牛頓 2003 年 11 月 2003 年 11 月 Prof. Kitano