General Biology: Foundations, Scientific Method, and Chemistry of Life

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Characteristics and Organization of Life

What is Life?

Life is defined by a set of properties that distinguish living things from non-living matter. These properties are essential for the survival and reproduction of organisms.

Order: Organized structures such as cells, tissues, and organs.
Reproduction: Ability to produce offspring.
Growth & Development: Increase in size and changes guided by genetic instructions.
Energy Processing: Use and transformation of energy (e.g., cellular respiration, photosynthesis).
Regulation (Homeostasis): Maintaining stable internal conditions.
Response to the Environment: Reacting to stimuli (e.g., plants turning toward light).
Evolutionary Adaptation: Populations evolve traits that enhance survival and reproduction.

Domains of Life

What are the 3 Domains of Life?

All living organisms are classified into three domains based on cellular structure and genetics:

Bacteria: Prokaryotic, unicellular organisms, cell walls with peptidoglycan.
Archaea: Prokaryotic, unicellular, many are extremophiles (live in extreme conditions), no peptidoglycan.
Eukarya: Eukaryotic cells with nucleus and organelles; includes protists, fungi, plants, and animals.

Types of Organisms in Each Domain

Bacteria: E. coli, Streptococcus, cyanobacteria.
Archaea: Methanogens (produce methane), thermophiles (heat-loving), halophiles (salt-loving).
Eukarya:
- Protists: Amoeba, paramecium.
- Fungi: Yeast, mushrooms.
- Plants: Mosses, ferns, flowering plants.
- Animals: Insects, humans, mammals.

Shared Characteristics Within Each Domain

Bacteria & Archaea: Both are prokaryotic (no nucleus, no membrane-bound organelles, mostly unicellular).
Archaea: Distinct membrane lipids, some genes more similar to eukaryotes.
Eukarya: All have membrane-bound nucleus, organelles, and linear chromosomes.

Differences Between the Domains

Bacteria vs. Archaea: Different cell wall composition (peptidoglycan vs. none), different membrane lipids, genetic differences.
Prokaryotes (Bacteria/Archaea) vs. Eukaryotes: Eukaryotes have nucleus, organelles, larger cell size, multicellularity possible.

Biological Hierarchy and Emergent Properties

How is Life Organized as a Hierarchy?

Biological hierarchy shows how living systems are structured from simple to complex:

Atom → Molecule → Organelle → Cell → Tissue → Organ → Organ system → Organism → Population → Community → Ecosystem → Biosphere

Why is this Hierarchy Important?

Complexity builds from simple to advanced structures.
Each level has emergent properties (new functions not seen at lower levels).

What are Emergent Properties?

Emergent properties arise at higher levels of organization and are not present at lower levels.

Example: Individual heart cells can't pump blood, but the whole heart can.
Example: Consciousness arises from billions of connected neurons.

Examples of Emergent Properties

Chlorophyll molecules absorb light, but a leaf can perform photosynthesis.
Individual ants can't form colonies, but ant societies show division of labor.
Water molecules have polarity, but in bulk, water shows cohesion and surface tension.

Unifying Themes in Biology

What are the 5 Unifying Themes in Biology?

Evolution: Explains unity and diversity of life.
Information: DNA encodes life's instructions, central dogma.
Structure & Function: Biological form fits function (enzymes, lungs, wings).
Energy & Matter: Flow of energy through ecosystems (sunlight → food → heat).
Interactions: Organisms interact with each other and environment (symbiosis, competition, food webs).

These themes unify biology into a coherent field of study.

Evolution: Descent with Modification and Selection

Descent with Modification

Darwin's phrase meaning species today came from ancestral species, gradually changing over generations, with modifications that improve survival and reproduction.

Natural Selection

Mechanism of evolution where organisms with traits better suited to environment survive and reproduce more successfully, passing on beneficial traits.

Examples of Natural Selection

Peppered moths during the Industrial Revolution (dark-colored moths survived better on soot-covered trees).
Darwin's finches in the Galápagos (different beak shapes adapted to different food sources).
Antibiotic resistance in bacteria (resistant bacteria survive drug treatment and spread).

Artificial Selection

Process where humans select which individuals reproduce based on desirable traits.

Examples of Artificial Selection

Dog breeding (bulldogs, retrievers, etc.).
Crops (corn bred for size, wheat for yield).
Domestic animals (cows bred for milk/meat production).

Information Flow in Cells

How Does Information Flow in a Cell?

Information is stored in DNA as genes.
Central Dogma: DNA → RNA → Protein.
DNA is transcribed into messenger RNA (mRNA).
mRNA is translated into proteins at ribosomes.
Proteins carry out cellular functions (enzymes, structure, transport).

What Influences This Process?

Environmental signals (temperature, stress, nutrients).
Regulatory proteins and transcription factors.
Mutations in DNA can alter expression or function of proteins.
Epigenetic modifications (like methyl groups) can turn genes on/off.

Structure and Function in Biology

Form Fits Function

In biology, the shape/structure of a molecule or organ enables its role.

Examples of Structure-Function Relationship

Enzyme active sites specifically fit substrates.
Red blood cells are disk-shaped to maximize oxygen transport.
Bird wings are shaped for flight.
DNA's double helix allows replication.

Importance of Structure-Function Relationship

A molecule, cell, or organ can only function correctly if its structure is intact.
If structure is altered (ex: sickle-cell hemoglobin), function is impaired.

Energy and Matter in Ecosystems

Transmission of Energy and Matter

Energy flow: Sunlight → producers (plants) → consumers (animals) → decomposers → heat loss.
Matter cycle: Nutrients (C, N, P, etc.) cycle between organisms and environment.

Importance of Energy and Matter Flow

Energy flow supports life processes.
Matter recycling maintains available nutrients for organisms.

Organisms Involved in Energy and Matter Flow

Producers: Plants, algae, some bacteria.
Consumers: Herbivores, carnivores, omnivores.
Decomposers: Fungi, bacteria.

Interactions in Biological Systems

Importance of Interactions

Interactions create feedback loops that regulate populations, nutrient cycles, and ecosystem stability.
Without interactions, ecosystems collapse (ex: removing predators causes prey overpopulation).

Examples of Biological Interactions

Predator-prey relationships (wolves and deer).
Pollination (bees and flowers).
Symbiosis (gut bacteria in humans).
Competition (plants competing for sunlight).

The Scientific Method

How Does the Scientific Method Work?

Observation
Question
Hypothesis (testable explanation)
Prediction
Experiment
Analysis
Conclusion
Communication/repetition

Why is the Scientific Method Important?

Provides a systematic way to test ideas.
Reduces bias.
Ensures results are repeatable and reliable.

What is a Hypothesis?

A testable, falsifiable explanation for an observation.

What Isn't a Hypothesis?

NOT a guess or opinion.
NOT untestable.
NOT as broad as a theory.

How Can We Test Hypotheses?

Through controlled experiments (manipulating one variable at a time).
By gathering data and seeing if results support or refute it.

Independent vs. Dependent Variable

Independent variable: What the scientist changes (ex: amount of sunlight).
Dependent variable: What is measured (ex: plant growth).

What is a Theory?

A broad, well-supported explanation of natural phenomena, supported by evidence.
Example: Theory of Evolution, Germ Theory of Disease.

How Does a Theory Differ from a Hypothesis?

A hypothesis is a narrow, testable statement.
A theory is broad, supported by many experiments and observations.

Science as Repetitive, Non-linear, and Collaborative

Repetitive: Experiments repeated many times (ex: testing vaccines in multiple trials).
Non-linear: Scientists may revisit old hypotheses or change direction.
Collaborative: Teams of scientists share data (ex: Human Genome Project).

Connection to Technology and Society

Microscopes (technology) → cell discoveries.
DNA sequencing → medicine, ancestry testing.
Climate science → influences policy and sustainability.

Elements, Atoms, and Compounds

What are Elements?

Pure substances that cannot be broken down by chemical means.
Example: Hydrogen (H), Oxygen (O), Carbon (C).

Main Elements in Humans

96% of body mass: Carbon (C), Hydrogen (H), Oxygen (O), Nitrogen (N).
Remaining ~4%: Calcium (Ca), Phosphorus (P), Potassium (K), Sulfur (S), Sodium (Na), Chlorine (Cl), Magnesium (Mg).

Why These Elements?

They form stable covalent bonds.
Carbon is versatile (forms 4 bonds).
Oxygen & hydrogen are critical for water.
Nitrogen is needed for proteins and nucleic acids.