Foundations of General Biology: Properties, Organization, and Scientific Method

Properties of Living Things

Key Characteristics of Life

All living organisms share a set of fundamental properties that distinguish them from non-living matter. Understanding these properties is essential for studying biology.

• Order: Living things exhibit a specific and organized structure, often composed of cells arranged in a particular sequence.

• Energy Processing: Organisms acquire and use energy. Some, like plants, produce their own energy from inorganic sources (photosynthesis), while others consume organic or inorganic sources.

• Growth and Development: All living things grow and develop according to instructions encoded in their DNA. For example, humans develop from babies to adults.

• Response to Environment: Organisms can sense and respond to stimuli. Venus flytraps have trigger hairs that sense prey and cause the trap to close.

• Reproduction: Living things reproduce, either sexually or asexually, to produce new individuals.

• Regulation & Homeostasis: Organisms regulate internal conditions, such as body temperature in humans through sweating.

• Evolutionary Adaptation: Populations of organisms evolve over time, adapting to their environment. Individuals do not evolve, but populations do.

Example:

• Humans maintain a stable body temperature (homeostasis) and reproduce sexually.

• Venus flytrap responds to environmental stimuli by closing its trap when prey touches its hairs.

Unifying Themes of Life

Five Unifying Themes

Biology is organized around several major themes that help explain the diversity and complexity of life.

• Organization: Life is structured in a hierarchical manner, from molecules to the biosphere. Cells are membrane-bound units that form tissues, organs, and organ systems.

• Information: Organisms process hereditary information encoded in genes and respond to information from the environment.

• Energy and Matter: All organisms acquire and use energy and matter to sustain life.

• Interactions: Living things interact with other organisms and their environment, forming complex relationships.

• Evolution: Populations of organisms change over time through evolutionary processes.

Levels of Biological Organization

• The Biosphere: The global ecosystem, including all life on Earth.

• Ecosystems: Communities of living organisms interacting with their physical environment (e.g., grasslands, tundra, rainforests, deserts).

• Communities: Different groups of living organisms in a shared environment.

• Populations: Groups of individuals of the same species.

• Organisms: Individual living things.

• Organs: Structures composed of tissues (e.g., lungs, heart, liver).

• Tissues: Groups of similar cells performing a specific function (e.g., muscle tissue, cardiac tissue).

• Cells: The basic unit of life (e.g., red blood cells, white blood cells).

• Organelles: Specialized structures within cells (e.g., mitochondria, endoplasmic reticulum, ribosomes).

• Molecules: Chemical structures such as water (H2O).

Darwin's Theory of Natural Selection

Development and Principles

Charles Darwin developed the theory of natural selection after observing finches on the Galapagos Islands. He noted differences in beak shapes and sizes, which were adaptations to different food sources.

• Finches on islands with hard seeds had deeper, stronger beaks.

• Finches on islands with softer seeds had shorter, brittle beaks.

• Darwin called this process descent with modification.

Key Points:

• Natural selection explains how populations evolve and adapt to their environment.

• Traits that enhance survival and reproduction become more common in a population over generations.

Classification of Life: Domains and Kingdoms

The Three Domains of Life

All living organisms are classified into three domains based on cellular structure and genetic differences.

• Bacteria: Single-celled organisms such as E. coli.

• Archaea: Single-celled organisms that often live in extreme environments and lack a defined shape.

• Eukarya: Domain containing all eukaryotic organisms, divided into four subgroups: plants, fungi, animals, and protists.

Classification Table

Domain	Cell Type	Examples	Key Features
Bacteria	Prokaryotic	E. coli	Single-celled, no nucleus
Archaea	Prokaryotic	Halophiles, thermophiles	Single-celled, extreme environments
Eukarya	Eukaryotic	Plants, animals, fungi, protists	Cells with nucleus and organelles

The Scientific Method

Steps and Application

The scientific method is a systematic approach to inquiry in science, involving observation, hypothesis formation, experimentation, and conclusion.

1. Ask a question

2. Gather background information

3. Formulate a hypothesis

4. Conduct experiments

5. Analyze data

6. Draw conclusions

7. Repeat and verify results

• Hypothesis: A testable statement that must be falsifiable. Hypotheses can be supported but never proven absolutely.

Example:

• Testing whether fish oil reduces heart attacks: Two groups are compared, one taking fish oil and one not. Data shows fewer heart attacks in the fish oil group, supporting the hypothesis.

Reasoning in Science

Deductive vs. Inductive Reasoning

Scientific reasoning can be deductive or inductive, each with distinct characteristics.

• Deductive Reasoning: Starts from general principles and applies them to specific cases. Conclusions are guaranteed if premises are true.

• Inductive Reasoning: Begins with specific observations and develops general principles. Conclusions are probable, not certain.

Comparison Table

Type	Starting Point	Conclusion Certainty
Deductive	General principles	Certain
Inductive	Specific observations	Probable

Experimental Design

Control and Experimental Groups; Variables

Experiments are designed to test hypotheses by comparing control and experimental groups and analyzing variables.

• Control Group: The baseline group where no experimental treatment is applied.

• Experimental Group: The group receiving the treatment or variable being tested.

• Dependent Variable: The variable being measured (e.g., number of heart attacks).

• Independent Variable: The variable being manipulated (e.g., fish oil intake).

Example:

• In a study on fish oil, the control group does not receive fish oil, while the experimental group does. The dependent variable is the incidence of heart attacks.

Scientific Theory

Definition and Importance

A scientific theory is a comprehensive explanation of natural phenomena, supported by a large body of evidence and capable of generating testable hypotheses.

• Theory vs. Hypothesis: A theory is broader and more general than a hypothesis. It is supported by extensive evidence and can lead to many testable predictions.

Example:

• The theory of evolution explains the diversity of life and is supported by evidence from genetics, fossils, and comparative anatomy.