Biosphere, Population Ecology, and Ecosystem Dynamics: Study Guide (Chapters 34 & 36)

Study Guide - Smart Notes

Tailored notes based on your materials, expanded with key definitions, examples, and context.

Biosphere, Population Ecology, and Ecosystem Dynamics

Key Vocabulary and Concepts

This section covers essential terms and foundational concepts in ecology, population biology, and the biosphere. Understanding these terms is crucial for interpreting ecological patterns and processes.

Age Structure: The distribution of individuals among different ages in a population. It influences population growth and decline.
Atmosphere: The layer of gases surrounding Earth, essential for climate regulation and supporting life.
Biosphere: The global sum of all ecosystems; the zone of life on Earth, including land, water, and the atmosphere.
Climate: The long-term patterns of temperature, humidity, wind, and precipitation in a region.
Carrying Capacity (K): The maximum population size that an environment can sustain indefinitely.
Camouflage: Adaptations that allow organisms to blend into their environment to avoid predation.
Community: All the populations of different species living and interacting in a particular area.
Conservation Biology: The scientific study of protecting biodiversity and restoring ecosystems.
Consumer: An organism that obtains energy by feeding on other organisms (heterotroph).
Demographic Transition: The shift from high birth and death rates to lower birth and death rates as a country develops.
Density-Dependent Factors: Factors whose effects on population size increase or decrease depending on population density (e.g., competition, predation, disease).
Density-Independent Factors: Factors that affect population size regardless of density (e.g., natural disasters, climate).
Dispersion: The pattern of spacing among individuals within a population (clumped, uniform, random).
Ecosystem: A community of organisms and their physical environment interacting as a system.
Food Chain/Food Web: The sequence of energy transfer from producers to consumers; a food web is a complex network of interconnected food chains.
Greenhouse Gases: Gases such as CO2 and methane that trap heat in the atmosphere, contributing to global warming.
Herbivory: The consumption of plant material by animals.
Invasive Species: Non-native species that spread rapidly and disrupt local ecosystems.
K-Selected Species: Species with traits favoring survival in stable environments (few offspring, high parental care).
Keystone Species: A species with a disproportionately large effect on its ecosystem relative to its abundance.
Landscape: A mosaic of connected ecosystems in a region.
Parasites: Organisms that live on or in a host, deriving nutrients at the host's expense.
Pathogens: Disease-causing organisms such as bacteria, viruses, or fungi.
Population: A group of individuals of the same species living in the same area.
Population Density: The number of individuals per unit area or volume.
Predation: An interaction where one organism (predator) kills and eats another (prey).
Producer: An organism that makes its own food through photosynthesis or chemosynthesis (autotroph).
R-Selected Species: Species with traits favoring rapid reproduction in unstable environments (many offspring, low parental care).
Species: A group of organisms capable of interbreeding and producing fertile offspring.
Weather: The short-term state of the atmosphere at a specific time and place.

Major Concepts and Applications

Arctic Tundra Biome: Characteristic Features

Extremely cold, dry climate with short growing seasons.
Permafrost (permanently frozen subsoil) limits plant growth.
Vegetation includes mosses, lichens, grasses, and dwarf shrubs.
Low biodiversity and simple food webs.
Animals adapted for cold (e.g., thick fur, fat layers).

Dispersion Patterns in Populations

Clumped: Individuals are grouped in patches; common where resources are unevenly distributed (e.g., schools of fish).
Uniform: Individuals are evenly spaced, often due to territorial behavior (e.g., nesting birds).
Random: Individuals are spaced unpredictably; rare in nature (e.g., wind-dispersed plants).
Example: Clumped - elephants around water holes; Uniform - penguins nesting; Random - dandelions in a field.
Additional info: Images typically show dots representing individuals in each pattern.

Survivorship Curves

Graphs showing the number or proportion of individuals surviving at each age.
X-axis: Age or time; Y-axis: Number or proportion of survivors (log scale often used).
Type I: High survivorship until old age (e.g., humans).
Type II: Constant death rate at all ages (e.g., birds).
Type III: High mortality early in life, few survivors live long (e.g., oysters, many plants).

Density-Dependent Factors Regulating Population Growth

Competition for resources (food, space, mates).
Predation and herbivory.
Disease and parasitism.
Accumulation of waste products.

Calculating Rate of Population Increase

Population growth rate is determined by birth and death rates.
Equation:

Where r is the per capita rate of increase, b is the birth rate, and d is the death rate.
Population size change:

Where N is the population size.

R-Selected vs. K-Selected Species

Trait	R-Selected Species	K-Selected Species
Body Size	Small	Large
Time to Sexual Maturity	Short	Long
Number of Offspring	Many	Few
Parental Care	Low	High
Type of Habitat	Unstable	Stable

Logistic vs. Exponential Growth

Exponential Growth: Population increases rapidly under ideal conditions; J-shaped curve.
Equation:

Logistic Growth: Population growth slows as it approaches carrying capacity; S-shaped curve.
Equation:

Where K is carrying capacity.

Ecosystem Influence on Evolution

Environmental pressures (e.g., predation, competition, climate) drive natural selection.
Examples: Camouflage in prey species, antibiotic resistance in bacteria, beak shape in Darwin's finches.

Interspecific Interactions

Competition: Both species are harmed by shared resource use.
Predation: One species benefits, the other is harmed.
Herbivory: Animal eats plant; plant may evolve defenses.
Parasitism: Parasite benefits, host is harmed.
Mutualism: Both species benefit (e.g., bees and flowers).
Commensalism: One benefits, the other is unaffected (e.g., barnacles on whales).
Adaptations: Thorns, toxins, mimicry, warning coloration.

Ecological Niches and Overlap

When two species have overlapping niches, competition occurs.
May result in competitive exclusion or resource partitioning.

Energy Transfer in Trophic Levels

Only about 10% of energy is transferred from one trophic level to the next.
Energy decreases at each successive level (producers → primary consumers → secondary consumers, etc.).
Example: If producers have 10,000 kcal, primary consumers get ~1,000 kcal, secondary consumers get ~100 kcal.

The Carbon Cycle

Carbon moves between atmosphere, biosphere, hydrosphere, and geosphere.
Key processes: photosynthesis, respiration, decomposition, combustion.
Plants absorb CO2; animals release CO2 via respiration.

The Global Water Cycle

Water circulates through evaporation, condensation, precipitation, and runoff.
Oceans are the main reservoir; transpiration from plants returns water vapor to the atmosphere.

Ecosystem Services

Benefits provided by ecosystems to humans, including:
- Provisioning (food, water, raw materials)
- Regulating (climate, disease, water purification)
- Supporting (nutrient cycling, soil formation)
- Cultural (recreation, spiritual value)