Campbell Biology: Concepts & Connections, Chapter 1 - Exploring Life

• Red pandas (Ailurus fulgens) are well adapted for life in the mountainous forests of Asia.

  • Their cinnamon red and white coat camouflage them with the red mosses and white lichens of their environment.

  • Their long bushy tail provides warmth during the winter.

  • A bony projection in their wrist helps them grasp one of their favorite foods, bamboo.

• Giant pandas live in similar regions in Asia.

• Are they closely related to red pandas?

• Scientists once thought so but have since reclassified red pandas into their own families.

• Despite their distinct lineages, the red panda and the giant panda do have something in common—they are both at risk of going extinct in the wild.

What is Life?

• Biology is the scientific study of life.

• But what is life? Properties of life include order, reproduction, growth and development, energy processing, regulation, response to the environment, and evolutionary adaptation.

• The cell is the structural and functional unit of life.

1.2 Biologists Arrange the Diversity of Life into Three Domains

• Taxonomists name species and classify them into broader groups.

• Although the debate continues, there is consensus among biologists that life can be organized into three higher levels called domains.

  • Domains Bacteria and Archaea contain organisms with simple cells.

  • Domain Eukarya includes various protists and the kingdoms Fungi, Plantae, and Animalia.

1.3 Visualizing the Concept: In Life’s Hierarchy of Organization, New Properties Emerge at Each Level

• Biologists study life across a very broad range of scales, from the molecules in a cell to the entire living planet.

• They divide this vast scope of biology into a series of structural levels.

Emergent properties result from the specific arrangement and interactions among component parts.

The Process of Science:

• Science is a way of knowing—an approach to understanding the natural world.

  • Science uses an evidence-based process of inquiry to investigate the natural world.

  • The scientific approach involves observations, hypotheses, predictions, tests of hypotheses via experiments or additional observations, and analysis of data.

  • A scientific theory is broad in scope and supported by a large body of evidence.

1.5 Hypotheses Can Be Tested Using Controlled Experiments

• In an experimental test of a hypothesis, researchers often manipulate one component in a system and observe the effects of this change.

  • The factor that is manipulated is called the independent variable.

  • The measure used to judge the outcome of the experiment is called the dependent variable. This variable depends on the manipulated variable.

  • A controlled experiment compares an experimental group with a control group.

    • The use of control and experimental groups can demonstrate the effect of a single variable. For example, researchers found that mice models that did not match their habitat had higher predation rates than camouflaged models.

    • Hypotheses can be tested in humans with clinical trials, as well as retrospective or prospective observational studies.

Table 1.5 Results from Camouflage Experiment

1.6 Scientific Thinking: Hypotheses Can Be Tested Using Observational Data

• Scientists tested hypotheses about the evolutionary relationships of red pandas.

  • Based on observations of physical similarities, scientists initially hypothesized that the red panda was most closely related to raccoons.

  • Other scientists, observing that the diet and habitat of red pandas were similar to those of giant pandas, placed the two pandas together in their own families.

  • But recent studies comparing D N A sequences led scientists to classify red pandas as the only living species of their own family.

1.7 The Process of Science Is Repetitive, Nonlinear, and Collaborative

• Forming and testing hypotheses at the core of science. This endeavor is influenced by three spheres:

  1. exploration and discovery,

  2. analysis and feedback from the scientific community, and

  3. societal benefits and outcomes.

1.8 Connection: Biology, Technology, and Society Are Connected in Important Ways

• The goal of science is to understand natural phenomena.

• In contrast, the goal of technology is to apply scientific knowledge for some specific purpose.

• These two fields, however, are interdependent. Technological advances stem from scientific research and research benefits from new technologies.

Themes of Biology:

1.9 Theme: Evolution Is the Core Theme of Biology 

• Life is distinguished by its unity and its diversity.

• The scientific explanation for this unity and diversity is evolution, the process of change that has transformed life on Earth from its earliest forms to the vast array of organisms living today.

  • Darwin synthesized the theory of evolution by natural selection.

• Each species on Earth today has a family history.

• A species represents one twig on a branching tree of life that extends back in time through ancestral species more and more remote.

1.10 Evolution Connection: Evolution Is Connected to Our Everyday Lives

• Evolutionary theory is useful in medicine, conservation, and agriculture.

• Through the selective breeding of plants and animals, humans also act as agents of evolution.

• As a result of artificial selection, our crops, livestock, and pets bear little resemblance to their wild ancestors.
  

• 1.11 Theme: Life Depends on the Flow of Information

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• The processes of life depend on the transmission and use of information.

  • D N A is responsible for heredity and for programming the activities of a cell by providing the blueprint for proteins.

  • Information from the external and internal environment includes the stimuli, signals, and pathways that regulate body processes and gene expression.

1.12 Theme: Structure and Function Are Related

• The relationship between structure and function can be observed at every level of life.

• At the molecular level, the structure of a protein correlates with its function. For example, hemoglobin molecules transport oxygen in the blood.

• On the cellular level, the long extensions of nerve cells enable them to transmit impulses from your spinal cord to your toes.

1.13 Theme: Life Depends on the Transfer and Transformation of Energy and Matter

• Energy flows through an ecosystem in one direction

  • entering as sunlight,

  • converted to chemical energy by producers,

  • passed on to consumers, and

  • exiting as heat.

• Ecosystems are characterized by the cycling of matter

  • from the atmosphere and soil,

  • through producers, consumers, and decomposers,

  • then back to the environment.

1.14 Theme: Life Depends on Interactions Within and Between Systems

• The study of life extends from the microscopic scale of the molecules and cells that make up an organism to the global scale of the living planet.

• Emergent properties are the result of interactions between the components of a system.

• Using an approach called systems biology, scientists attempt to model the behavior of biological systems by analyzing the interactions among their parts.