ENS Central Questions

What 3 natural processes allow life on Earth to persist over long period of time?

Solar energy, biodiversity, and chemical cycling

Why do human societies ultimately depend on natural capital?

they rely on natural capital to support their economies

Why are shared resources often overused?

How can a country have a large population but not have the largest per capita ecological footprint?

Per capita footprint measures resource consumption per person. Even with a high total population, lower average resource consumption, reduced industrial activity, or lower energy use per individual keeps the per capita footprint smaller.

Why can higher standards of living increase environment impact?

Higher standards of living usually involve greater per capita consumption of energy, meat, goods, and raw materials, generating more waste and greenhouse gas emissions per person.

How can environmental worldviews influence environmental decision making?

How does each level of ecological organization build upon the previous level?

Each level adds more organisms and interactions from one organism to the entire biosphere

How is an organism’s niche different from its habitat?

A habitat is the physical address or environment where an organism lives, while a niche is its functional role or "job" within the ecosystem (e.g., what it eats, how it reproduces, and its interactions).

Why is biodiversity important to ecosystem stability?

Higher biodiversity provides greater functional redundancy and genetic variation, making ecosystems more resilient and able to recover from environmental disturbances or diseases

Why are specialist species often more vulnerable to environmental change?

Picky animals can only survive in narrow environment

Why do some non-native species become invasive

They compete with and reduce an ecosystems native species

How can certain species provide information about ecosystem health?

They are early biological warning signs

Why can’t populations continue growing exponentially forever?

Resources like food, water, light, and space are finite, which introduces environmental resistance (carrying capacity, $K$) as population size increases

How do limiting factors influence population size?

They restrict population growth by increasing mortality or decreasing birth rates, keeping the population stabilized near its environment's carrying capacity

Why does population density influence parasite transmission?

High population density increases contact rates between individuals, allowing density-dependent factors like parasites and pathogens to spread much more easily

What happens when populations exceed carrying capacity?

The population experiences an overshoot, which leads to resource depletion, environmental degradation, and a subsequent die-back or population crash (increased mortality)

How do demographers determine whether a population is growing or shrinking?

By comparing growth factors (birth rate and immigration) against reduction factors (death rate and emigration), often calculated as the Natural Increase Rate (NIR) or total population growth rate

Why is total fertility rate an important demographic measure?

It measures the average number of children born to a woman during her childbearing years, serving as a key indicator of population growth potential, replacement-level fertility, and social/economic development

How can age structure help predict future population growth?

By showing the proportion of individuals across pre-reproductive, reproductive, and post-reproductive age cohorts; a wide base indicates high population momentum and rapid future growth

Why does population growth accelerate during one stage and slow during another?

During the demographic transition, death rates fall first due to improved healthcare and sanitation while birth rates stay high (causing rapid acceleration); growth then slows as economic development and education cause birth rates to decline to match low death rates.

How can societies reduce population growth without increasing death rates?

By expanding access to family planning and contraception, improving education and social opportunities for women, and lowering infant mortality so families naturally choose to have fewer children

How do producers, decomposers, and detritivores work together to maintain ecosystem function?

Producers synthesize organic matter from sunlight and inorganic nutrients; detritivores physically break down dead organic waste into smaller particles; and decomposers chemically break down that waste, recycling nutrients back into the soil and water for producers to reuse

What would happen if decomposers disappeared from an ecosystem

Dead organic matter and waste would continuously accumulate, trapping essential nutrients and preventing them from recycling. This would starve producers, ultimately causing the collapse of the entire food web