General Biology Chapter 1: A View of Life.

Chapter 1 Notes: A View of Life

1.1 The Characteristics of Life

• Biology is the scientific study of life.

• Great diversity among living things, but all share basic characteristics.

• Living things are composed of the same chemical elements as nonliving things and obey the same physical and chemical laws that govern the universe.

• Living things are organized at multiple levels from atoms to the biosphere, with the cell as the basic unit of structure and function.

• Emergent properties: as biological complexity increases, each higher level acquires new properties not found at the previous level.

The Organization of Life: Levels of Organization

• Atom → Molecule → Cell → Tissue → Organ → Organ system → Organism → Species

• Population → Community → Ecosystem → Biosphere

• An organism forms when organ systems are joined; organs work together to form organ systems; tissues make up organs; similar cells form tissues; molecules form larger molecules within a cell; atoms combine to form molecules; organization begins with atoms.

The Biosphere and Associated Concepts

• The biosphere: the zone of air, land, and water where organisms exist.

• An ecosystem = a community plus its physical environment.

• A community = interacting populations within the same environment.

• A population = all members of a species within an area.

• A species = a group of similar, interbreeding organisms.

Energy, Metabolism, and Homeostasis (Characteristics of Life)

• Life requires materials and energy; energy is the capacity to do work.

• Energy maintains organization and drives life-sustaining processes (metabolism).

• Metabolism = all chemical reactions in a cell.

• The sun is the ultimate energy source for nearly all life on Earth.

  • Plants, algae, and some organisms capture solar energy and perform photosynthesis.

  • Photosynthesis converts solar energy into chemical energy stored as carbohydrates.

Ecosystems: Chemical Cycling and Energy Flow

• Ecosystems are characterized by chemical cycling and energy flow.

• Chemicals are not used up when organisms die; they cycle from producers to consumers to decomposers and back to plants via dead matter and decomposition.

• Energy from the sun flows through the food chain; solar energy must be continually input.

Homeostasis, Response to Stimuli, and Development

• Homeostasis: maintenance of internal conditions within certain boundaries; requires feedback systems that monitor conditions and adjust as needed.

• Living things respond to stimuli from the environment; response often involves movement.

• Reproduction and development are essential for population maintenance; inheritance via genes.

Reproduction, Development, and Genetics

• All organisms must reproduce to maintain populations.

• Modes of reproduction vary among organisms.

• Offspring inherit genetic information (genes) from parents; genes determine organism characteristics and are composed of DNA (deoxyribonucleic acid).

• Genetic information is passed to the next generation.

Adaptations and Evolution

• An adaptation is a modification that improves an organism’s function in a particular environment.

• Long-term environmental changes drive the development of new adaptations; life’s diversity arises from those adaptations.

• Evolution: change in a population over time to become better suited to the environment.

1.2 Evolution and the Classification of Life

• The theory of evolution explains both the diversity and unity of life; all living things descended from a common ancestor with modification over time (common descent with modification).

Natural Selection (Darwin’s Mechanism)

• Natural selection = environment selects which traits are more likely to be passed on; individuals with favorable traits produce more surviving offspring, increasing the frequency of those traits in the population.

• Mutations provide the variation on which natural selection acts; mutations generate new traits.

Evolutionary Tree of Life

• An evolutionary tree is like a family tree; it traces ancestry of life on Earth back to a common ancestor.

Taxonomy, Classification, and Systematics

• Taxonomy: identifying, naming, and classifying organisms according to rules.

• Systematics: study of evolutionary relationships among organisms.

• Classification categories (from least to most inclusive): species, genus, family, order, class, phylum, kingdom, domain.

• Each higher level includes more types of organisms than the level below.

Levels of Classification: Humans vs. Corn (Examples)

• Domain: Eukarya | Eukarya

• Kingdom: Animalia | Plantae

• Phylum: Chordata | Anthophyta

• Class: Mammalia | Monocotyledones

• Order: Primates | Commelinales

• Family: Hominidae | Poaceae

• Genus: Homo | Zea

• Species: Homo sapiens | Zea mays

• Note: To specify an organism, use the full binomial name (genus + species) in italics: Homo sapiens, Zea mays.

Domains

• Domain Archaea: unicellular prokaryotes; extreme environments; lack a membrane-bound nucleus; unique chemical characteristics; absorb or chemosynthesize food.

• Domain Bacteria: unicellular prokaryotes; diverse shapes; live in all environments including skin, mouth, and gut; absorb, photosynthesize, or chemosynthesize food; unique chemical characteristics.

• Domain Eukarya: unicellular and multicellular eukaryotes; have a membrane-bound nucleus.

Eukaryotic Supergroups and Kingdoms

• Within Domain Eukarya: kingdoms include Protists (composed of several kingdoms), Fungi, Plantae, and Animalia.

• Kingdom designations for Archaea/Bacteria are being determined; new supergroups and classifications continue to evolve.

Scientific Names and Binomial Nomenclature

• Universal Latin-based binomial nomenclature:

  • Two-part name: genus (capitalized) + species designation (lowercase).

  • Both words italicized: Genus species (examples: Homo sapiens, Zea mays)

1.3 The Process of Science

• The scientific method is a standard series of steps for acquiring new knowledge through research; can be divided into five steps: Observation, Hypothesis, Predictions and Experiments, Data Collection with Statistical Analysis, Conclusion.

The Scientific Method (Overview)

• Observation: scientists use senses to gather information about a phenomenon.

• Hypothesis: a tentative explanation; testable; developed through inductive reasoning; example: discovery of penicillin.

• Predictions and Experiments: experiments test hypotheses; deductive reasoning to predict outcomes; experimental design isolates the effect of a specific factor (the independent variable).

• Experimental Design: test and control groups; independent variable is the factor being tested.

• Experiments: a test group is exposed to the independent variable; a control group undergoes all aspects except the independent variable; if both groups show the same results, the hypothesis is not supported.

• Data: observable and objective results; tables and graphs are common formats; data are analyzed using statistics.

• Measures of variation: Standard error (describes how far the sample mean may be from the true population mean).

• Statistical significance: p-value (p); typically p < 0.05 is considered significant; a lower p-value indicates greater confidence that results are not due to chance alone.

• Conclusion: data are interpreted to decide whether the hypothesis is supported or rejected; predictions that hold support the hypothesis.

• Findings are reported in scientific journals and undergo peer review; replication by other scientists is important for validation.

Scientific Publications and Theories vs. Principles

• Scientific Theory: coherent, well-supported concepts that join together multiple well-supported hypotheses; supported by a broad range of observations, experiments, and data.

• Scientific Principle/Law: broadly accepted set of theories; no serious challenges to validity.

Basic Theories of Biology (Summary)

• Theory/Concepts:

  • Cell: All organisms are composed of cells, and new cells come only from preexisting cells.

  • Homeostasis: Internal environment stays relatively constant within life-protective ranges.

  • Evolution: All living organisms share a common ancestor, but are adapted to their environments.

Controlled Study and Experimental Design Example

• Example: Antibiotics A vs B for ulcers; experimental design includes one untreated control group and two test groups (A and B).

• Data collection: endoscopy used to assess ulcers; statistics determine treatment effectiveness; conclusions indicate whether the hypothesis is supported.

1.4 Challenges Facing Science

• Science is a systematic method for acquiring knowledge about the natural world.

• Technology is the application of scientific knowledge to human interests (e.g., cell phones, new drugs).

Biodiversity, Habitat Loss, and Extinction

• Biodiversity = total number and relative abundance of species, genetic variation, and ecosystem variety.

• Estimated global species count up to ~8.7 million, with fewer than 2.3 million named.

• Extinction = death of the last member of a species; hundreds of species are estimated to be lost each year due to human activities.

Biologically Diverse Ecosystems in Danger

• Tropical rain forests and coral reefs harbor many organisms and are threatened by human activity.

• Canopy in tropical forests supports orchids, insects, and monkeys; coral reefs provide habitat for jellyfish, sponges, crabs, lobsters, sea turtles, moray eels, and fishes.

Destruction of Healthy Ecosystems and Unintended Consequences

• Humans depend on healthy ecosystems for food, medicines, and raw materials.

• Examples of consequences:

  • Draining wetlands (Mississippi and Ohio River basins) worsened flooding and damaged farmland.

  • Destruction of South American rain forests led to species loss and reduced lumber availability.

Emerging Diseases

• Recent diseases include: H5N1, H7N9, SARS, MERS, COVID-19.

• Origins of emerging diseases:

  • New or increased exposure to insects or animals

  • Changes in human behavior

  • Use of technology (e.g., Legionnaires’ disease)

  • Globalization

  • Pathogens mutating and changing hosts (e.g., avian influenza)

Climate Change

• Changes in Earth’s climate cycles attributable to human activities.

• Mechanism: more carbon released than removed; fossil fuel burning and deforestation increase atmospheric CO2, driving global warming via the greenhouse effect.

• Consequences: global warming is altering ecosystems and impacts biodiversity and human well-being.

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