Ecology, Population Growth, and Human Demographics: Key Concepts and Structures

What is ecology?

The study of the interactions of organisms with each other and with their environment.

What is the first level of organization above the organism?

Population.

What is the second level of organization above the organism?

Community.

What is the third level of organization above the organism?

Ecosystem.

What is the fourth level of organization above the organism?

Biosphere.

What comes before Community?

Population.

What comes before the Ecosystem?

Community.

What comes before the Biosphere?

Ecosystem.

What comes after Population?

Community.

What comes after Community?

Ecosystem.

What comes after Ecosystem?

Biosphere.

What is a population?

All the members of one species in an area.

What is a community?

All of the different populations interacting with each other.

What is an ecosystem?

The community interacting with the physical environment.

What is a biosphere?

The zone of the Earth (air, water, and land) where life exists.

What was the growth of the human population like before the Industrial Revolution?

Growth was slow.

How often does the human population currently double?

Every 40 years.

What is the current human population?

7.8 billion.

What is the estimated stabilization population by 2100?

11 billion.

How do you calculate growth rate?

Growth rate = (births - deaths) / births.

If there are 1000 births and 900 deaths, what is the growth rate?

10%.

If there are 500 births and 300 deaths, what is the growth rate?

40%.

If there are 300 births and 450 deaths, what is the growth rate?

-50%.

What is biotic potential?

The maximum growth rate for a species given ideal conditions.

What is exponential growth?

Population grows at the fastest rate possible.

What is logistic growth?

Population growth that slows and levels off as it reaches carrying capacity.

What is carrying capacity?

The maximum number of individuals an environment can support without being damaged.

What determines carrying capacity?

Availability of resources such as food, water, space, and shelter.

What happens when a population exceeds carrying capacity?

The population decreases due to lack of resources, increased competition, or higher death rates.

What happens when a population is below carrying capacity?

The population can continue to grow because resources are abundant.

What type of graph represents a population reaching carrying capacity?

An S-shaped curve (logistic growth curve).

What keeps a population at or near carrying capacity?

Limiting factors like food supply, disease, predators, or habitat size.

What is a limiting factor?

Anything that restricts population size (ex: food, water, space).

How does carrying capacity create a stable population?

Populations tend to fluctuate around K but remain relatively stable over time.

What happens to the growth rate at carrying capacity?

The growth rate becomes zero because births ≈ deaths.

How can carrying capacity change over time?

It can increase or decrease based on environmental changes or resource availability.

What does MDC stand for?

More Developed Country.

What does LDC stand for?

Less Developed Country.

Describe the economy of an MDC.

Strong, industrialized economy with high income levels.

Describe the economy of an LDC.

Lower-income economy, often based on agriculture and limited industry.

What is the birth rate like in MDCs?

Low birth rate.

What is the birth rate like in LDCs?

High birth rate.

What is the death rate like in MDCs?

Low death rate due to good healthcare.

What is the death rate like in LDCs?

Higher death rate because of limited healthcare.

Describe life expectancy in MDCs.

Long life expectancy.

Describe life expectancy in LDCs.

Shorter life expectancy.

What does an MDC age structure diagram look like?

Narrow base, even sides — looks like a rectangular or barrel shape.

What does an LDC age structure diagram look like?

Wide base and narrow top — looks like a pyramid shape.

What does a wide base in an age structure diagram indicate?

High birth rates (common in LDCs).

What does a more rectangular age structure indicate?

Stable or slowly growing population (common in MDCs).

Which type of country has rapid population growth?

LDCs.

Which type of country has slow or zero population growth?

MDCs.

Which type of country has better access to healthcare and education?

MDCs.

Which type of country tends to have higher infant mortality?

LDCs.

Which type of country has more elderly people in its population?

MDCs.

Which type of country has a younger population overall?

LDCs.

What is a density-dependent factor?

A factor that affects population growth based on the population density.

What is an example of a density-dependent factor?

Competition, predation, and parasitism.

In LDCs, which age group has the largest proportion of individuals?

Prereproductive group.

What is ecological succession?

The gradual process by which ecosystems change and develop over time.

What is primary succession?

Succession that occurs in an area with no soil and no previous life.

What is secondary succession?

Succession that occurs in an area where a disturbance has happened but soil and some organisms still remain.

What is symbiosis?

A close, long-term relationship between two different species in which at least one species benefits.

What are the three main types of symbiotic relationships?

Mutualism, commensalism, and parasitism.

What is mutualism?

A symbiotic relationship in which both species benefit.

What is commensalism?

A symbiotic relationship in which one species benefits and the other is neither helped nor harmed.

What is parasitism?

A symbiotic relationship in which one species benefits and the other is harmed.

What is the competitive exclusion principle?

No two species can occupy the same niche at the same time.

What is a habitat?

The natural environment where an organism lives and gets the resources it needs to survive.

What are producers?

Photosynthetic organisms that trap the energy of the sun and convert it into organic compounds.

What are consumers?

Organisms that feed on other organisms.

What is a food chain?

A simple, linear sequence showing who eats whom.

What is a food web?

A combination of multiple food chains in an ecosystem.

What is an ecological pyramid?

A graphical representation showing the different trophic levels in an ecosystem.

What is the ultimate source of energy for most ecosystems?

The sun.

Why does energy decrease at each trophic level?

Energy is lost as heat during metabolism.

Why are food chains unrealistic in real ecosystems?

Most organisms have multiple food sources.

Why are food webs more accurate than food chains?

They show many feeding relationships, not just one.

What is a trophic level?

A position or step in a food chain or food web.

What organisms occupy the first trophic level?

Producers.

What are primary consumers?

Herbivores that eat producers.

What are secondary consumers?

Carnivores or omnivores that eat primary consumers.

What are tertiary consumers?

Predators that eat secondary consumers.

What role do decomposers play in energy flow?

They break down dead matter and recycle nutrients.

What does a pyramid of numbers show?

The number of organisms at each trophic level.

Can a pyramid of numbers be inverted?

Yes, especially when one producer supports many consumers.

What does a pyramid of biomass show?

The total mass of organisms at each trophic level.

In what ecosystem is a biomass pyramid often inverted?

Aquatic ecosystems (due to phytoplankton).

What does a pyramid of energy show?

The energy available at each trophic level.

Which ecological pyramid is always upright?

The pyramid of energy.

What is the 10% rule?

Only about 10% of energy is passed to the next trophic level.

Why are top predators fewer in number?

There is less energy available at higher trophic levels.

What is a biogeochemical cycle?

The movement of elements and compounds through living organisms, the atmosphere, water, and soil.

Why are biogeochemical cycles important?

They recycle essential elements, maintaining ecosystem balance and supporting life.

What are the main biogeochemical cycles?

Carbon, nitrogen, phosphorus, water (hydrologic), and sulfur cycles.

What does the carbon cycle involve?

Movement of carbon through the atmosphere, plants, animals, soil, oceans, and fossil fuels.

How do plants contribute to the carbon cycle?

They take in carbon dioxide during photosynthesis and release it during respiration.

What role do animals play in the carbon cycle?

They release carbon dioxide during respiration and contribute to organic matter after death.

What is the nitrogen cycle?

The process by which nitrogen moves between the atmosphere, soil, and living organisms.

How is nitrogen made available to plants?

Through nitrogen fixation by bacteria and lightning, converting N₂ to usable forms (ammonia, nitrates).