Introduction to Biology

Overview

This study guide covers foundational concepts in biology, including definitions of key terms, properties of life, the hierarchy of biological organization, ecosystem dynamics, cell types, domains of life, evolution, natural and artificial selection, and the scientific method. These topics form the basis for understanding modern biology.

Key Biological Terms

Definitions

• Biology: The scientific study of life and living organisms.

• Life: The condition that distinguishes living organisms from inanimate matter, marked by growth, reproduction, functional activity, and continual change preceding death.

• Emergent Property: A characteristic of a system that does not appear in any of its component parts but arises from their interactions (e.g., consciousness in the brain).

• Biosphere: The global sum of all ecosystems; the regions of the surface, atmosphere, and hydrosphere of the Earth occupied by living organisms.

• Ecosystem: A community of living organisms and their physical environment interacting as a system.

• Cell: The basic structural, functional, and biological unit of all living organisms.

• Prokaryotic: Cells that lack a nucleus and membrane-bound organelles (e.g., bacteria and archaea).

• Eukaryotic: Cells that contain a nucleus and membrane-bound organelles (e.g., plants, animals, fungi, protists).

• DNA (Deoxyribonucleic Acid): The molecule that carries genetic instructions for the development, functioning, growth, and reproduction of all known organisms.

• Gene: A segment of DNA that codes for a specific protein or function.

• Genome: The complete set of genes or genetic material present in a cell or organism.

• Taxonomy: The science of classifying organisms into groups based on similarities and differences.

• Domain: The highest taxonomic rank in the classification of organisms, above kingdom.

• Kingdom: The second highest taxonomic rank, grouping together all forms of life having certain fundamental characteristics in common.

• Protist: A diverse group of mostly unicellular eukaryotic organisms.

• Evolution: The process by which different kinds of living organisms have developed and diversified from earlier forms during the history of the Earth.

• Natural Selection: The process by which organisms better adapted to their environment tend to survive and produce more offspring.

• Artificial Selection: The intentional breeding of plants or animals by humans to produce desired traits.

• Science: The systematic study of the structure and behavior of the physical and natural world through observation and experiment.

• Discovery Science: The process of scientific inquiry that focuses on describing nature through observation and analysis of data.

• Hypothesis-Driven Science: The process of scientific inquiry that uses the scientific method to test hypotheses.

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

• Hypothesis: A testable explanation for an observation or scientific problem.

• Controlled Experiment: An experiment in which only one variable is changed at a time, while all others are kept constant.

• Theory: A well-substantiated explanation of some aspect of the natural world, based on a body of evidence and repeatedly confirmed through observation and experimentation.

• Technology: The application of scientific knowledge for practical purposes.

Properties and Processes of Life

Seven Properties of Life

• Order: Living things exhibit complex but ordered organization.

• Regulation: Organisms can regulate their internal environment (homeostasis).

• Growth and Development: Organisms grow and develop according to specific instructions coded in their DNA.

• Energy Processing: Organisms take in energy and use it to power all their activities.

• Response to Environment: Organisms respond to environmental stimuli.

• Reproduction: Organisms reproduce their own kind.

• Evolutionary Adaptation: Populations evolve over generations as individuals with traits best suited to their environments have greater reproductive success.

Hierarchy of Life

Ten Levels of Biological Organization

1. Biosphere: All life on Earth and all the places where life exists.

2. Ecosystem: All living things in a particular area, along with the nonliving components.

3. Community: All the organisms inhabiting a particular ecosystem.

4. Population: All individuals of a species living within the bounds of a specified area.

5. Organism: An individual living thing.

6. Organ System: A group of organs that work together to perform a specific function.

7. Organ: A body part that carries out a particular function in the body.

8. Tissue: A group of similar cells that perform a specific function.

9. Cell: The fundamental unit of life.

10. Organelle: A membrane-enclosed structure with a specialized function within a cell.

11. Molecule: A chemical structure consisting of two or more atoms.

Additional info: Some textbooks may combine or split certain levels; the above list follows a common structure.

Ecosystem Roles and Processes

Roles of Producers, Consumers, and Decomposers

• Producers: Organisms (usually plants and algae) that produce organic compounds from sunlight via photosynthesis.

• Consumers: Organisms that obtain energy by eating other organisms (animals, humans).

• Decomposers: Organisms (such as bacteria and fungi) that break down dead organic material, recycling nutrients back into the ecosystem.

Major Ecosystem Processes

• Nutrient Cycling: The transfer of nutrients through the biotic and abiotic components of an ecosystem.

• Energy Flow: The movement of energy through an ecosystem, typically entering as sunlight and exiting as heat.

Organisms play roles in these processes by producing, consuming, and decomposing organic matter, thus maintaining ecosystem stability.

Cell Types

Prokaryotic vs. Eukaryotic Cells

Domains of Life

The Three Domains

Evolution and Natural Selection

Descent with Modification

• Darwin described evolution as "descent with modification," meaning that species change over time, giving rise to new species, and share a common ancestor.

Observations Leading to Natural Selection

1. Variation: Individuals in a population vary in their traits, many of which are heritable.

2. Overproduction: More offspring are produced than can survive, leading to competition for resources.

Differential (Unequal) Reproductive Success: Individuals with traits better suited to the environment are more likely to survive and reproduce, passing those traits to the next generation.

Natural vs. Artificial Selection

The Scientific Method

Steps in the Scientific Method

1. Observation: Noticing and describing phenomena in a careful, orderly way.

2. Question: Formulating a question based on observations.

3. Hypothesis: Proposing a testable explanation for the observation.

4. Prediction: Making a logical prediction based on the hypothesis.

5. Experiment: Testing the hypothesis through controlled experiments.

6. Results: Collecting and analyzing data.

7. Conclusion: Drawing conclusions and communicating results.

Additional info: The process is iterative; hypotheses may be revised based on results.

Scientific Theory vs. Hypothesis

Everyday vs. Scientific Use of "Theory"

• In everyday language, a "theory" may mean a guess or speculation.

• In science, a theory is a comprehensive, well-supported explanation for a broad set of observations.

• A hypothesis is a specific, testable statement that can be supported or refuted through experimentation.

• Theories are broader in scope than hypotheses and are supported by a large body of evidence.

Relationship: Hypotheses are tested and, if repeatedly supported, may contribute to the development of a scientific theory.