Biology: History of Earth & Human Society

Modified by KSU EEOB: Morris, Hartl, Knoll, Lue, Michael Heitz, Hens, Lozovsky, Merrill, Phillis, Pires, Liu
Copyright © Macmillan Learning

Compare mass extinction events throughout the history of Earth with the current rate of biodiversity loss.
Identify the major threats to biodiversity caused by human activity.
Describe trends in climate and atmospheric conditions over the course of geological history.
Explain how changes in environmental conditions have influenced biota and how biological organisms have influenced Earth’s environments.
Explain how biotic and abiotic interactions influence organismal diversification and extinction.
Define the Anthropocene.
Discuss ecological conditions during Homo sapiens evolution and traits leading to evolutionary success.
Identify major population and dispersal trends in Homo sapiens throughout history.
Evaluate humans as ecosystem engineers.
Analyze human impacts on the carbon cycle and feedback between the carbon cycle and global climate.
Evaluate impacts on nitrogen and phosphorus cycles.
Describe feedback mechanisms between biogeochemical cycles and the global climate.
Relate species loss and ecosystem disruption to ecological, evolutionary, and societal consequences.
Compare conservation biology strategies to mitigate habitat degradation, loss, and biodiversity loss.
Describe methods for countering climate change.
Examine living sustainably as humans.

Definition: A graph depicting the measured concentration of CO₂ in the atmosphere over time.
Key Patterns:
- Seasonal:
- Spring/Summer: Plants absorb CO₂ through photosynthesis; levels drop.
- Fall/Winter: Decaying plant matter releases CO₂; levels rise.
- Long-term:
- Each subsequent year ends with a higher CO₂ level than the previous year.
Cause: Linked to human activities, particularly fossil fuel combustion and deforestation.

CO₂ Levels & Temperature:
- Over the past 400,000 years, Earth has seen cyclic patterns of temperature and CO₂ levels, alternating between glacial (cold) and interglacial (warm) periods.
- The historical carbon cycle plays a significant role in stabilizing Earth's climate via balancing CO₂ input and removal.
- Climate can change independently of human input for extended periods.

Definition: Gases that trap heat in the Earth’s atmosphere, allowing life by preventing freezing.
Key Greenhouse Gases:
- Carbon dioxide (CO₂)
- Methane (CH₄)
- Water vapor (H₂O)
Effects of Increased Greenhouse Gases:
- Amplified Greenhouse Effect: Leads to global warming.
Human Activities Contributing to Increase:
- CO₂: Burning fossil fuels and deforestation
- Methane: Agriculture (cattle digestion), rice cultivation, and thawing permafrost.

As atmospheric CO₂ levels rise, so do the mean surface temperatures.
Climate models accounting for only natural factors (solar and volcanic) fail to match the observed rise in temperatures.
When human emissions are considered, models align closely with observed temperature increases.

The Deadly Trio: Effects of rising CO₂ on oceans:
1. Increase in Ocean Temperature: Caused by more greenhouse gases.
2. Decrease in pH of Seawater (Acidification): Due to increased dissolved CO₂.
3. Decrease in Oxygen in Seawater (Deoxygenation): Linked to higher temperatures affecting oxygen storage capacity.

Positive Feedbacks:
- Soil respiration: Warming leads to increased soil respiration, causing more CO₂ to be released.
- Permafrost thawing: Warming causes melting of permafrost, releasing both methane and CO₂.
Negative Feedbacks:
- CO₂ Fertilization: Increased atmospheric CO₂ can enhance plant growth, leading to higher carbon sequestration.
- Effects vary by species with potential increased crop output but decreased nutrient quality.

Mean annual temperature has increased by approximately 2.5°C.
Species are flowering earlier (approximately 1 week sooner).
Climate change exerts selection pressure on all biological levels, influencing populations to migrate, adapt, or face extinction.
Potential lack of time for populations to evolve and adapt, leading to significant ecological shifts.

Role in Ecosystems: Nitrogen (N) and phosphorous (P) control carbon and energy flow, acting as limiting nutrients influencing primary production rates.
Human Alteration of Nitrogen Cycle:
- Increased nitrogen availability leads to:
- Higher nitrogen oxides (NOx) emissions
- Acid rain formation
- Eutrophication
- Feedback effects with climate change impacting plant growth and biodiversity.
Eutrophication: Results from excess nutrients, causing algal blooms, subsequent oxygen depletion, and creating dead zones in aquatic habitats.

Process:
- Nutrient-rich runoff from agriculture enters water bodies, causing algal blooms.
- Decomposition of dead algae by bacteria consumes oxygen, resulting in low oxygen areas unsuitable for aquatic life.
- Human activities impacting cycles include:
- Use of nitrogen-based fertilizers
- Fossil fuel combustion.

Warming alters nutrient cycling, which then influences climate.
Positive Feedbacks: Accelerate warming (e.g., permafrost melting).
Negative Feedbacks: Stabilize climate (e.g., carbon uptake by vegetation).
Eutrophication Feedback:
- Algal biomass leads to anaerobic conditions, releasing more phosphorus from sediments, causing increased algal growth and higher productivity.

A representation of the 13.8 billion-year history of the universe scaled into a single calendar year.
Key Milestones:
- January: Big Bang
- May: Formation of solar system and origin of life
- October/November: Evolution of significant biological forms - multicellular organisms, the advent of land plants, and various fauna.
- December: Evolution of homo sapiens and notable historical events (e.g., first agricultural settlements, industrial revolution).
Illustrative perspective on human history as a minimal fraction of cosmic time - human life equivalent to only 0.23 cosmic seconds compared to the universe's timeline.

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