7.28 Introductory Ecology & Population Ecology Lecture

Question-and-answer flashcards that review definitions, processes, examples, and models discussed in the Introductory Ecology and Population Ecology lecture.

What is ecology?

The study of how organisms interact with each other (biotic factors) and with their physical environment (abiotic factors).

How does environmental science differ from ecology?

Environmental science applies ecological knowledge to solve real-world problems and often involves advocacy, whereas ecology focuses on understanding interactions in nature.

Which book by Rachel Carson led to the U.S. ban on DDT?

Silent Spring.

Define biotic factors.

Living components of an environment, such as competitors, predators, parasites, and mutualists.

Define abiotic factors.

Non-living environmental components, such as temperature, water availability, light, pH, soil nutrients, fire, and salinity.

What is studied at the organismal level of ecology?

Individual behavior, physiology, or pathology of a single organism.

Define a population in ecological terms.

A group of interbreeding individuals of the same species living in the same area.

What does community ecology examine?

All the populations (different species) that live and interact in a given area, including species richness and interactions.

What is an ecosystem?

A biological community plus the abiotic factors with which it interacts, emphasizing energy flow and nutrient cycling.

What does landscape ecology investigate?

How spatial arrangement and habitat fragmentation across large areas affect ecological processes.

What is the biosphere?

All of Earth’s ecosystems considered together; the global ecological system.

Which field method uses a square frame to estimate plant abundance and diversity?

Quadrat sampling.

Describe the mark–recapture formula for population size.

N ≈ (number originally marked × total caught in second sample) ÷ marked recaptures.

Name the three common dispersion patterns.

Clumped, uniform, and random.

Differentiate population size from population density.

Size (N) is the total number of individuals; density is individuals per unit area or volume.

What does demography study?

Birth rates, death rates, immigration, emigration, and age structure of populations.

What characterizes a Type I survivorship curve?

High survivorship until late life; most mortality occurs in old age (e.g., humans).

Describe a Type II survivorship curve.

Constant death rate at all ages (e.g., many birds).

Describe a Type III survivorship curve.

High early mortality with few individuals surviving to adulthood (e.g., many insects, some annual plants).

Define semelparity.

A life-history strategy in which an organism reproduces once, produces many offspring, then dies (e.g., Pacific salmon, agave).

Define iteroparity.

A strategy in which an organism reproduces multiple times during its life, either seasonally or continuously (e.g., most mammals, perennial plants).

What shape is an exponential growth curve and under what conditions does it occur?

A J-shaped curve produced when a population grows at its intrinsic rate (r) with no limiting resources.

What shape is a logistic growth curve?

An S-shaped (sigmoidal) curve that levels off at the carrying capacity (K) as resources become limiting.

What is carrying capacity (K)?

The maximum population size an environment can sustain indefinitely.

What does the intrinsic rate of increase (r) represent?

The maximum per-capita growth rate of a population under ideal conditions.

Give examples of density-dependent factors.

Competition, predation, parasitism, and disease.

Give examples of density-independent factors.

Weather extremes, drought, floods, fires, hurricanes, or other abiotic disturbances.

List key traits of r-selected species.

Short life span, early maturity, many small offspring, little or no parental care, boom-and-bust population cycles.

List key traits of K-selected species.

Long life span, late maturity, few large offspring, extensive parental care, populations stabilize near carrying capacity.

What role do Hadley cells play in global climate?

They lift warm, moist air at the equator causing heavy rainfall there, then drop dry air around 30° N & S, creating deserts.

Explain the rain-shadow effect.

Moist air rises on a mountain’s windward side, cools and releases precipitation; dry air descends on the leeward side, producing arid conditions.

How can temperature limit species distribution?

Physiological stress from excessive heat or cold restricts where species such as kangaroos or cacti can survive.

Why is soil pH important for plants?

Extreme acidity or alkalinity can make essential nutrients unavailable, restricting plant distribution.

Give an example of fire-dependent reproduction.

Giant sequoias (and longleaf pines) require periodic fire to open cones and reduce competition.

Distinguish climate from weather.

Weather is day-to-day atmospheric conditions; climate is long-term average patterns of temperature and precipitation.

Describe the greenhouse effect.

Greenhouse gases (e.g., CO₂, CH₄) trap reradiated heat in the atmosphere, raising Earth’s surface temperature.

Which anthropogenic gas is chiefly responsible for recent warming trends?

Carbon dioxide (CO₂) from fossil-fuel combustion and deforestation.

Which country currently emits the most total CO₂?

China, followed by the United States.

What information does an age-structure diagram provide?

Proportions of a population in pre-reproductive, reproductive, and post-reproductive age classes, indicating potential growth trends.

What is a transect in field sampling?

A straight line along which systematic samples or quadrats are taken to estimate population parameters.

Why are many of Earth’s deserts found at roughly 30° latitude?

Dry descending air from Hadley cells removes moisture, creating arid subtropical zones at those latitudes.