BIO124 Exam Review: Human Impacts and Climate Change

What are the three main factors causing environmental problems?

1) Population size, 2) Resource consumption, 3) Human interaction with ecosystems.

What defines a mass extinction?

A mass extinction occurs when over 75% of species die out globally in a geologically short time.

What are the three criteria for identifying a mass extinction?

1) 75% or more species disappear, 2) Extinction occurs worldwide, 3) It happens rapidly in geological time.

How many major mass extinctions have occurred before the current one?

There have been five major mass extinctions caused mainly by abiotic factors.

What distinguishes the sixth mass extinction from previous ones?

The sixth mass extinction is primarily driven by biotic factors, specifically human activities.

What are the two phases of the sixth mass extinction?

Phase 1: Human migration out of Africa; Phase 2: Agriculture and industrialization.

Why was agriculture a significant ecological change?

Agriculture allowed for larger, permanent populations and changed ecosystems to produce food.

What is carrying capacity (K) and what does its growth graph look like?

Carrying capacity (K) is the maximum population an environment can support, represented by a logistic S-shaped curve.

What happens when limits are removed from a population?

The population can exhibit exponential growth, forming a J-shaped curve.

What local carrying capacity did agriculture help humans escape?

Agriculture allowed humans to escape local carrying capacity but not global limits.

What is the current human population and its growth trend?

About 8.3 billion in 2026, with a steep increase after industrialization, particularly post-1950.

What is a greenhouse gas (GHG)? Name two major ones.

A GHG absorbs and re-emits infrared energy; major ones include carbon dioxide (CO₂) and methane (CH₄).

What does energy balance mean in the context of Earth?

Energy balance means the energy absorbed from the Sun equals the energy emitted back to space.

Why must Earth send about 240 W/m² to space?

Earth absorbs about 240 W/m² of solar energy and must emit the same amount to maintain energy balance.

What disrupts Earth's energy balance?

Adding greenhouse gases from burning fossil fuels slows the escape of infrared energy, creating an energy imbalance.

What is the IPCC?

The Intergovernmental Panel on Climate Change, which assesses climate change science.

What are the effects of burning fossil fuels on atmospheric CO₂?

Burning fossil fuels increases atmospheric CO₂ levels, contributing to climate change.

What is the significance of the Vostok ice core data?

It shows historical CO₂ levels ranging from ~180 to 300 ppm, with current levels exceeding 420 ppm.

What role do water vapor and sea-ice feedbacks play in climate change?

They amplify warming effects by enhancing the greenhouse effect.

What is the difference between logistic and exponential growth?

Logistic growth slows near carrying capacity; exponential growth accelerates when limits are removed.

How did human activities contribute to the sixth mass extinction?

Through habitat destruction, overharvesting, pollution, and climate change, increasing extinction risk.

What is the relationship between population growth and resource use?

More people using more resources leads to increased environmental impacts, including pollution and habitat loss.

What is the significance of the 75% extinction rate in mass extinctions?

It indicates a severe loss of biodiversity and ecological stability across the planet.

What are the implications of the current extinction rates?

Current rates are estimated to be 10-1,000 times higher than normal background rates due to human activity.

How did the Industrial Revolution affect human population growth?

It led to significant improvements in sanitation, medicine, and food supply, accelerating population growth.

What is the impact of fossil fuel energy on land use and pollution?

Fossil fuel energy has massively increased land use, resource extraction, and pollution levels.

What is the role of the Intergovernmental Panel on Climate Change?

It reviews and evaluates scientific evidence about climate change, its effects, and ways to reduce and prepare for it.

What are fossil fuels and how do they form?

Fossil fuels are coal, oil, and natural gas formed from ancient organic matter buried and changed by heat and pressure over millions of years.

Has climate changed before human influence?

Yes, Earth's climate has naturally changed many times over its 4.6-billion-year history due to natural forces.

What evidence indicates that humans are increasing CO₂ levels?

The rise in CO₂ began with industrial fossil-fuel burning, with a carbon-isotope fingerprint showing much of the added CO₂ comes from fossil fuels.

What do Vostok ice cores reveal about historical CO₂ levels?

They show that CO₂ levels were roughly 180-300 ppm before industrialization, while current levels are far above that range.

What is the relationship between CO₂ and global temperature?

There is a positive correlation; as CO₂ concentrations increase, global temperatures generally rise.

What is a tipping point in climate systems?

A tipping point is a critical threshold where a small change can trigger a larger change in a system, often difficult to reverse.

How do oceans and sea ice relate to climate change?

Oceans absorb excess heat, while melting sea ice reduces reflectivity, leading to further warming and ice melt.

What is a positive feedback cycle?

A change that causes other changes, amplifying the original change, such as warming leading to more water vapor, which traps more heat.

Explain the water-vapor positive feedback cycle.

Warmer air holds more water vapor, which traps more infrared energy, leading to further warming.

How does warmer air affect extreme and severe weather?

Warmer air increases evaporation, leading to droughts, and can hold more moisture, resulting in heavier rain and stronger storms.

What is sexual dimorphism?

Average physical differences between males and females, which can provide clues about mating systems.

What mating pattern do gorillas exhibit?

Gorillas typically have a polygyny mating pattern with males about 50% bigger than females.

What is the mating pattern of chimpanzees?

Chimpanzees exhibit a multi-male, multi-female mating pattern, with males about 30% bigger than females.

What characterizes human mating systems?

Humans show variable mating systems, with strong pair-bonding being common, but cultural and individual differences exist.

What role does oxytocin play in human behavior?

Oxytocin is involved in bonding and many social processes, but it is not solely responsible for monogamous behavior.

What does the Clark-Hatfield campus proposition study indicate?

It showed that many more men than women agreed to a stranger's sexual invitation, highlighting differences in mating behavior.

What is the Anthropocene?

A term for the era in which humans significantly influence climate and ecosystems, though not an officially adopted geological epoch.

What are the main components of atmospheric composition?

Air is about 78% nitrogen, 21% oxygen, and a small fraction of other gases, with CO₂ currently above 0.04%.

What is the significance of the Paris Agreement?

Countries aim to keep global warming well below 2°C and pursue a target of 1.5°C above preindustrial temperatures.

What are some strategies for emission reductions?

Strategies include cleaner power, reduced fossil-fuel use, improved efficiency, methane cuts, and conservation.

What is the carbon cycle?

The process where atmospheric CO₂ is absorbed by plants during photosynthesis, stored in food chains, and returned to the air through respiration and decomposition.

What happens when fossil fuels are burned?

Burning fossil fuels releases carbon that had been stored underground, contributing to atmospheric CO₂ levels.

What is the significance of the 350 ppm CO₂ target?

It is a climate advocacy target associated with 350.org, not a universally agreed safe boundary.

What study reflects a social setting regarding sexual invitations?

The Clark-Hatfield campus proposition study

What is a caution against broad claims about gender behavior?

Culture, safety, expectations, and individual choices matter.

What are the three roots of environmental issues?

Population size, resource consumption, and our relationship with nature.

How many major mass extinctions occurred before the current one?

Five.

What generally triggered the earlier five mass extinctions?

Mostly physical or abiotic forces.

What is the main cause of today's sixth mass extinction?

Human activities.

What divides phase 2 of the sixth extinction according to your professor?

Agriculture and industrialization.

What change allowed humans to exceed local food limits?

Agriculture.

What does carrying capacity (K) mean?

The maximum sustainable population in a given environment.

Which graph levels off near carrying capacity?

S-shaped logistic curve.

What curve is produced by removing resource limits at first?

J-shaped exponential curve.

What does agriculture help us escape?

Local carrying capacity, but not global carrying capacity.

What is the approximate global population in 2026?

About 8.3 billion.

Which two gases are major human-caused greenhouse gases?

Carbon dioxide and methane.

What does Earth being in energy balance mean?

Incoming absorbed energy equals outgoing energy to space.

Why is Earth currently gaining heat?

Greenhouse gases have increased and slow infrared energy loss.

What does IPCC stand for?

Intergovernmental Panel on Climate Change.

Which are considered fossil fuels?

Coal, oil, and natural gas.

What is correct about climate history?

Climate changed naturally before, but current rapid warming is mainly human-caused.

Which carbon isotope do plants tend to take up more of?

Light carbon-12.

What do Vostok ice cores show about past CO₂ levels?

They were mostly around 180-300 ppm.

As carbon dioxide rises, what generally happens to global temperature?

It rises with a positive correlation.

What is a tipping point?

A threshold where a small extra change can cause a major shift.

Why does melting sea ice lead to more solar energy absorption?

Dark ocean water reflects less sunlight.

What sequence describes water-vapor feedback?

Warming → more water vapor → more greenhouse warming.

What helps explain stronger storms in a warmer climate?

Moist air can release latent heat when vapor condenses.