Science of Biology and Themes in Biology

Characteristics of Life

Biology is the study of living organisms, which share several fundamental characteristics. Understanding these traits helps distinguish living things from non-living matter.

• Order: Living things exhibit organized structure, from cells to tissues to organs.

• Regulation: Organisms maintain internal conditions (homeostasis).

• Growth and Development: Organisms grow and develop according to genetic instructions.

• Energy Processing: Living things acquire and use energy (e.g., photosynthesis, cellular respiration).

• Response to Environment: Organisms respond to stimuli.

• Reproduction: All living things reproduce, passing genetic material to offspring.

• Evolutionary Adaptation: Populations evolve over generations, adapting to their environment.

Characteristics of Science

Science is a systematic approach to understanding the natural world through observation and experimentation.

• Empirical: Based on observable evidence.

• Testable: Hypotheses and theories must be testable.

• Repeatable: Experiments can be repeated for verification.

• Objective: Minimizes bias through peer review and standardized methods.

What Makes a Good Hypothesis

A hypothesis is a proposed explanation for an observation, which must be testable and falsifiable.

• Testable: Can be evaluated through experiments or observations.

• Falsifiable: Can be proven false if evidence contradicts it.

• Specific: Clearly defines variables and expected outcomes.

• Example: "If plants are given more sunlight, then they will grow faster."

Theories, Hypotheses, Laws

Scientific explanations are organized hierarchically:

• Hypothesis: A tentative explanation for a phenomenon.

• Theory: A well-supported, broad explanation for a range of phenomena (e.g., theory of evolution).

• Law: A statement describing consistent natural phenomena (e.g., Mendel's laws of inheritance).

How Can Things Be Proven in the Sciences

Scientific knowledge is provisional; hypotheses and theories are supported by evidence but not absolutely proven. Science relies on repeated testing and peer review.

• Evidence: Accumulation of supporting data increases confidence.

• Falsification: Theories can be revised or rejected if new evidence arises.

Emergent Properties and Levels of Biology

Emergent properties arise when components interact at higher levels of organization, producing new characteristics.

• Levels: Molecules → Cells → Tissues → Organs → Organisms → Populations → Communities → Ecosystems → Biosphere

• Emergent Properties: Properties not present in individual parts but arise from their interactions (e.g., consciousness in the brain).

Introduction to Ecology and Biomes

What is Ecology?

Ecology is the scientific study of interactions between organisms and their environment, including both biotic and abiotic factors.

• Biotic: Living components (plants, animals, microbes).

• Abiotic: Non-living components (temperature, water, sunlight).

Ecology Relationship to Environmental Science, Environmentalism, and Natural History

• Environmental Science: Integrates ecology with other sciences to address environmental issues.

• Environmentalism: Social movement focused on protecting the environment.

• Natural History: Observational study of organisms in their environment.

Levels of Ecology

Ecology is studied at multiple levels:

• Organismal Ecology: Individual organisms' adaptations.

• Population Ecology: Groups of individuals of the same species.

• Community Ecology: Interactions among species.

• Ecosystem Ecology: Energy and nutrient flow between biotic and abiotic components.

• Landscape Ecology: Interactions across multiple ecosystems.

• Global Ecology: Biosphere-wide processes.

How the Climate is Controlled

Climate is determined by global patterns of temperature, precipitation, and atmospheric circulation.

• Solar Radiation: Drives temperature and weather patterns.

• Atmospheric Circulation: Movement of air masses creates climate zones.

• Ocean Currents: Redistribute heat and moisture.

Where We Expect Dry Areas and Wet Areas and Why

Global climate patterns create predictable dry and wet regions.

• Wet Areas: Near the equator (tropical rainforests) due to rising, moist air.

• Dry Areas: Around 30° N/S latitude (deserts) due to descending, dry air.

Rain Shadows

Rain shadows occur when mountains block moist air, causing dry conditions on the leeward side.

• Process: Moist air rises, cools, and releases precipitation on windward side; dry air descends on leeward side.

• Example: Eastern side of Sierra Nevada is dry due to rain shadow.

Directions of Weather and Why

Weather patterns are influenced by Earth's rotation and atmospheric circulation.

• Coriolis Effect: Causes winds to curve, creating prevailing wind patterns (e.g., trade winds, westerlies).

Characteristics and Distribution of Terrestrial Biomes

Biomes are major ecological communities defined by climate and vegetation.

• Tropical Rainforest: High rainfall, high biodiversity.

• Desert: Low rainfall, adapted plants and animals.

• Temperate Grassland: Moderate rainfall, grasses dominate.

• Temperate Forest: Moderate rainfall, deciduous trees.

• Tundra: Low temperature, low biodiversity.

Factors Controlling Aquatic Biomes

Aquatic biomes are influenced by physical and chemical factors.

• Salinity: Freshwater vs. marine environments.

• Depth: Light penetration affects photosynthesis.

• Flow: Rivers vs. lakes vs. oceans.

• Nutrients: Availability affects productivity.

Population Ecology

How Do Populations Grow?

Population growth is determined by birth rates, death rates, immigration, and emigration.

• Exponential Growth: Population increases rapidly under ideal conditions.

• Logistic Growth: Population growth slows as it approaches carrying capacity.

Exponential Growth Equation

The exponential growth of a population can be described by:

• Where N is population size, r is intrinsic growth rate.

Logistic Growth Equation

Logistic growth incorporates carrying capacity:

• Where K is carrying capacity.

What Happens as Population Approaches and Exceeds Carrying Capacity

As population size nears carrying capacity, resources become limited, slowing growth. If population exceeds carrying capacity, increased mortality and decreased birth rates occur.

• Carrying Capacity (K): Maximum population size environment can sustain.

• Overshoot: Population exceeds K, leading to resource depletion and population decline.

Density-Dependent and Density-Independent Factors

Population growth is regulated by factors that may depend on population density.

• Density-Dependent: Effects increase with population size (e.g., competition, predation, disease).

• Density-Independent: Effects are unrelated to population size (e.g., weather, natural disasters).

Intrinsic Growth Rate

The intrinsic growth rate (r) is the maximum rate at which a population can grow under ideal conditions.

• Determined by: Birth rate minus death rate.

Carrying Capacity and Its Determinants

Carrying capacity (K) is set by resource availability, environmental conditions, and competition.

• Food, water, space, and shelter are common limiting factors.

Three Longevity Curves

Survivorship curves illustrate patterns of mortality in populations.

• Type I: High survival in early/mid life, increased mortality in old age (e.g., humans).

• Type II: Constant mortality rate throughout life (e.g., birds).

• Type III: High mortality in early life, survivors live long (e.g., oysters).

K-selected, r-selected, Semelparous, and Iteroparous Life Histories

Life history strategies describe reproductive patterns and survival.

• K-selected: Few offspring, high parental care, stable environments.

• r-selected: Many offspring, low parental care, unstable environments.

• Semelparous: Single reproductive event (e.g., salmon).

• Iteroparous: Multiple reproductive events (e.g., humans).

Demographic Transitions

Demographic transition describes changes in birth and death rates as societies develop.

• Stage 1: High birth and death rates.

• Stage 2: Death rates decline, population grows.

• Stage 3: Birth rates decline, growth slows.

• Stage 4: Low birth and death rates, stable population.

Age Structure and Population Growth

Age structure diagrams show the distribution of individuals across age groups, predicting future growth.

• Expanding Population: Broad base, many young.

• Stable Population: Even distribution.

• Declining Population: Narrow base, fewer young.

What Controls Population Growth?

Population growth is controlled by resource availability, environmental conditions, and interactions with other species.

• Limiting Factors: Food, water, space, predation, disease.

• Regulation: Density-dependent and density-independent mechanisms.

Summary Table: Population Growth Models

Additional info: These notes cover material from Chapters 1, 52, and 53, which include foundational concepts in biology, ecology, and population dynamics. For exam preparation, review textbook readings and lecture materials for further examples and applications.