Chapter 1Invitation 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

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