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 things, from microscopic organisms to large multicellular organisms.

• It includes the investigation of structure, function, growth, origin, evolution, and distribution of living organisms.

Examples of Biological Study

• Biologists may study animals, plants, fungi, protists, and bacteria.

• Applications include medicine, environmental science, genetics, and biotechnology.

Characteristics of Life

Defining Features of Living Organisms

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

• Order: Living things are organized and structured.

• Reproduction: Ability to produce offspring.

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

• Energy Processing: Living things obtain and use energy.

• Response to Environment: Ability to respond to stimuli.

• Regulation (Homeostasis): Maintain stable internal conditions.

• Evolutionary Adaptation: Populations evolve over generations.

Note:

• Viruses are not considered alive because they lack many of these characteristics.

Life's Organizational Hierarchy

Levels of Biological Organization

• Life consists of multiple parts organized in a hierarchical pattern, from smallest to largest:

• Emergent Properties: New properties arise at each level of the hierarchy that are not present at the preceding level.

Unicellular vs. Multicellular Organisms

• Unicellular organisms consist of a single cell (e.g., bacteria, some protists).

• Multicellular organisms are composed of many cells (e.g., animals, plants, fungi).

Natural Selection & Evolution

Adaptation and Fitness

• Adaptation is a process that enables organisms to survive and reproduce in their environments.

• Fitness refers to an organism's ability to survive and reproduce.

Natural Selection

• Described by Charles Darwin as the process by which organisms with advantageous traits survive and reproduce more successfully.

• Natural selection requires:

  • Variation in traits within a population

  • Selection for heritable traits affecting fitness

  • Inheritance of traits

• Over generations, natural selection can lead to evolution of populations.

Introduction to Taxonomy

Classification of Life

• Taxonomy is the branch of science that classifies, identifies, and names organisms.

• Organisms are classified into hierarchical categories:

• The three domains of life are Bacteria, Archaea, and Eukarya.

• Domain Eukarya includes kingdoms: Animalia, Plantae, Fungi, and Protista.

Categorizing Life Based on Energy Acquisition

• 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) to consumers (heterotrophs).

The Scientific Method

Steps of the Scientific Method

• Observation: Noticing a phenomenon or problem.

• Question: Asking about the observation.

• Hypothesis: Proposing a testable explanation.

• Prediction: Making a specific statement about what will happen if the hypothesis is correct.

• Experiment: Testing the prediction.

• Analysis: Interpreting the results.

• Conclusion: Drawing conclusions and sharing results.

Predictions, Hypotheses, and Theories

• Hypothesis: A tentative explanation that can be tested.

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

Experimental Design

Variables

Controls in Experiments

• Negative Control: Group where no response is expected.

• Positive Control: Group where a known response is expected.

Basic Theories of Biology

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

• Homeostasis: All organisms maintain a relatively stable internal environment.

• Evolution: All organisms evolved from a single common ancestor.