Foundations of General Biology: Life, Evolution, and Scientific Inquiry

1. The Boundaries and Characteristics of Life

1.1 What is Life?

Biology seeks to define life by identifying the essential characteristics that distinguish living organisms from non-living matter. The study of life involves understanding how organisms maintain homeostasis, respond to stimuli, grow, and reproduce.

• Definition of Life: An organism that contains cells, can maintain homeostasis, can sense and respond to stimuli, grow, and reproduce.

• Key Points:

  • Cells: All living things are composed of cells, which are the basic units of life.

  • Homeostasis: The ability to maintain stable internal conditions.

  • Response to Stimuli: Organisms detect and respond to changes in their environment.

  • Growth and Reproduction: All organisms grow and reproduce, passing on genetic material to offspring.

• Example: Viruses challenge the definition of life because they share some characteristics with living organisms but lack cellular structure and independent metabolism.

Cell Types: Eukaryotic vs. Prokaryotic

Cells are classified into two main types based on their structure and organization.

• Eukaryotic Cells:

  • Contain organelles, including a nucleus that houses DNA.

  • May be unicellular or multicellular.

• Prokaryotic Cells:

  • Lack organelles and a defined nucleus.

  • All prokaryotic organisms are unicellular.

• Example: Bacteria are prokaryotic, while plants and animals are eukaryotic.

Organization and Energy Use

Living organisms acquire and use energy to maintain their internal organization and support life processes.

• Photosynthesis: Plants and some other organisms use sunlight to convert carbon dioxide and water into glucose and oxygen.

• Consumption: Animals and other heterotrophs obtain energy by consuming other organisms.

• Material Acquisition: Organisms require water, minerals, and other building blocks from their environment.

• Example: The flow of energy through ecosystems begins with photosynthetic organisms and continues through consumers and decomposers.

2. Evolution: The Unity and Diversity of Life

2.1 What is Evolution?

Evolution is the process by which populations of organisms change over time through descent with modification. It explains both the unity and diversity of life on Earth.

• Common Ancestry: All living organisms share a common ancestor.

• Natural Selection: Proposed by Charles Darwin and Alfred Russel Wallace, natural selection is the process by which traits that enhance survival and reproduction become more common in a population.

• Adaptation: Traits that improve an organism's ability to survive and reproduce in its environment.

• Extinction: Occurs when species fail to adapt to changing environments.

• Example: Dinosaurs were unable to adapt to environmental changes and became extinct.

Levels of Biological Organization

Biologists study life at multiple levels, from atoms to the biosphere.

• Atoms and Molecules: Atoms combine to form molecules, which are the building blocks of cells.

• Cells: The basic unit of life.

• Tissues and Organs: Groups of cells form tissues, which combine to make organs.

• Organ Systems: Organs work together in organ systems.

• Organisms: Individual living beings.

• Populations: Groups of organisms of the same species.

• Communities: Populations of different species living together.

• Ecosystems: Communities and their physical environment.

• Biosphere: All ecosystems on Earth.

Classification of Life

Biologists classify organisms into three major domains based on evolutionary relationships:

• Bacteria

• Archaea

• Eukarya

3. Scientific Inquiry and the Nature of Science

3.1 What is Science?

Science is a systematic approach to understanding the natural world through observation, experimentation, and reasoning.

• Physical Laws: Science is governed by natural laws that do not change over time or distance.

• Value Neutrality: Scientific findings are independent of personal beliefs.

• Scientific Method: A structured process for investigating phenomena.

Steps of the Scientific Method

• Observation: Gathering information about a phenomenon.

• Question: Formulating a question based on observations.

• Hypothesis: Proposing a testable explanation.

• Prediction: Making predictions based on the hypothesis.

• Experiment: Testing the hypothesis through controlled experiments.

• Conclusion: Analyzing results to support or refute the hypothesis.

Experimental Controls and Variables

• Control Group: Used for comparison to ensure that experimental results are due to the variable being tested.

• Variable: The factor that is changed or manipulated in an experiment.

• Repetition: Experiments are repeated to ensure reliability.

Scientific Theory

A scientific theory is a well-substantiated explanation of natural phenomena, supported by extensive evidence and repeated testing.

• Example: The theory of evolution explains the diversity of life through descent with modification.

4. HTML Table: Comparison of Cell Types

Feature	Eukaryotic Cells	Prokaryotic Cells
Organelles	Present (e.g., nucleus, mitochondria)	Absent
Nucleus	Present	Absent
Cell Type	Unicellular or Multicellular	Unicellular
Examples	Plants, Animals, Fungi	Bacteria, Archaea

5. Key Equations and Terms

• Photosynthesis Equation:

$6CO_2 + 6H_2O + \text{light energy} \rightarrow C_6H_{12}O_6 + 6O_2$

• Homeostasis: The process by which organisms maintain a stable internal environment.

• Evolution: The change in the heritable characteristics of biological populations over successive generations.

• Scientific Method: A systematic approach to research involving observation, hypothesis, experimentation, and conclusion.

Additional info: Some explanations and examples have been expanded for clarity and completeness.