Study Guide: Introduction to Biology – The Study of Scientific Life

Introduction to Biology

Definition and Scope of Biology

Biology is the scientific study of life. The term comes from the Greek words bios (life) and logos (study). Biology encompasses the study of all living organisms, from microscopic bacteria to large multicellular organisms like plants and animals.

• Biology: The study of living things and their vital processes.

• Organism: Any individual form of life, such as a plant, animal, bacterium, protist, or fungus.

• "-ology": A suffix meaning "the study of."

Example: Zoology is the study of animals; Botany is the study of plants.

Characteristics of Life

What Makes Something Alive?

All living organisms share certain characteristics that distinguish them from nonliving things.

• Order: Living things are highly organized, coordinated structures.

• Reproduction: Ability to produce offspring.

• Growth and Development: Organisms grow and develop according to specific instructions coded for by their genes.

• Energy Processing: Use of energy to power activities and chemical reactions.

• Response to Environment: Ability to respond to environmental stimuli.

• Regulation (Homeostasis): Maintenance of a stable internal environment.

• Evolutionary Adaptation: Populations evolve over generations.

Note: Viruses are not considered alive because they do not meet all these criteria.

Life's Organizational Hierarchy

Levels of Biological Organization

Life consists of multiple parts organized in a hierarchical pattern, from the smallest to the largest scale.

Level	Description
Atom	Smallest particle of an element
Organelle	Membrane-bound structure with a specific function
Cell	Basic unit of life
Tissue	Group of similar cells performing a function
Organ	Structure composed of tissues working together
Organ System	Group of organs working together
Organism	Individual living thing
Population	Group of organisms of the same species in an area
Community	All populations in a given area
Ecosystem	Community plus the nonliving environment
Biosphere	All environments on Earth that support life

Emergent Properties: New properties that arise with each step upward in the hierarchy of life, due to the arrangement and interactions of parts as complexity increases.

Example: Life emerges at the level of the cell, not at the level of molecules or organelles.

Natural Selection & Evolution

Adaptation and Fitness

Living organisms are well-suited to their environments due to adaptation, which improves fitness (the ability to survive and reproduce).

• Natural Selection: The process by which organisms with traits best suited to their environment are more likely to survive and reproduce. Described by Charles Darwin.

• Evolution: Change in the genetic composition of a population over generations.

Example: Giraffes with longer necks can reach more food and are more likely to survive and reproduce.

Introduction to Taxonomy

Classification of Life

Taxonomy is the branch of science that classifies, identifies, and names organisms. Organisms are classified into hierarchical categories:

Domain	Kingdom	Phylum	Class	Order	Family	Genus	Species
Eukarya	Animalia	Chordata	Mammalia	Primates	Hominidae	Homo	sapiens

Three Domains of Life:

• Bacteria: Prokaryotic, unicellular organisms

• Archaea: Prokaryotic, often found in extreme environments

• Eukarya: Eukaryotic, includes protists, fungi, plants, and animals

Kingdoms of Eukarya: Plantae, Fungi, Animalia, Protista

Energy Acquisition and Flow

Autotrophs vs. Heterotrophs

Organisms can be classified by how they acquire energy:

• Autotrophs: Produce their own food (e.g., plants via photosynthesis)

• Heterotrophs: Obtain energy by consuming other organisms (e.g., animals, fungi)

Energy flows from the sun to producers (autotrophs) and then to consumers (heterotrophs). With every transfer, some energy is lost as heat.

The Scientific Method

Steps in Scientific Investigation

The scientific method is a systematic approach to answering questions and testing hypotheses.

1. Pose a Question or Problem

2. Make an Observation

3. Form a Hypothesis

4. Design and Conduct an Experiment

5. Collect and Analyze Data

6. Draw Conclusions

7. Peer Review and Publish

Definitions:

• Prediction: Expected outcome if a hypothesis is correct.

• Hypothesis: A testable explanation for an observation.

• Theory: A broad explanation supported by a large body of evidence.

Experimental Design

Variables and Controls

Experiments test hypotheses by manipulating variables:

Variable Type	Definition	Example
Independent Variable	Factor changed by the experimenter	Amount of water given to plants
Dependent Variable	Factor measured in response	Growth of plants
Controlled Variable	Factors kept constant	Type of plant, soil, light

Controls:

• Negative Control: Group where no effect is expected

• Positive Control: Group where an effect is expected

Example: In a drug trial, a placebo group is a negative control; a group receiving a known effective drug is a positive control.

Basic Theories of Biology

Major Unifying Concepts

• All organisms are made of cells, and all cells come from preexisting cells. (Cell Theory)

• All organisms maintain a relatively constant internal environment. (Homeostasis)

• All organisms evolved from a single common ancestor. (Evolution)