Biology: How Life Works Unit 2: Ecology

Biology: How Life Works Unit 2: Ecology

Introduction

• Modified by KSU EEOB Biogeochemical cycle Week 6
• Contributors: Morris, Hartl, Knoll, Lue, Michael Heitz, Hens, Lozovsky, Merrill, Phillis, Pires, Liu
• Copyright

© Macmillan Learning

Nutritional Modes in Ecosystems

• Producers & Consumers: Classified by energy and carbon source.
• Organisms use aerobic and anaerobic processes for energy/carbon fixation.
• Energy and carbon intertwining: Close relationship between energy and carbon cycling.

Interactive Question

• iClicker Example: New bacteria using $NH<em>3$ (energy) and $CO</em>2$ (carbon) are Chemoautotrophs.

Importance of Bacteria and Archaea

• Essential for ecosystems (including human body) due to:
  • Diverse nutritional modes (Photoheterotrophy, Chemoautotrophy).
  • Ability to perform anaerobic processes (fermentation, anoxygenic photosynthesis).
  • Roles as primary producers/consumers in extreme environments.

Types of Metabolic Pathways in Bacteria and Archaea

• In microbial mats, pathways include:
  • Oxygenic Photosynthesis: Light + $O_2$
  • Anoxygenic Photosynthesis: Light, no $O_2$
  • Anaerobic Respiration: No light, no $O_2$

Extremophiles

• Bacteria and Archaea living in extreme conditions:
  • Extreme Halophiles: Thrive in high salinity (Mono Lake, Pink Lake).
  • Extreme Acidophiles: Survive in low pH.

Biogeochemical Cycles

• Connect living (biotic) and non-living (abiotic) ecosystem components.
• Chemical Cycling Overview: Nature

’s recycling for essential elements.

Reservoirs

• Types of Reservoirs:
  • Short-term (available) vs. Long-term (unavailable)
  • Organic (living biomass) vs. Inorganic (non-living)

Bacteria and Their Role in Biogeochemical Cycles

• Bacteria and archaea transform chemicals into biologically usable forms, exemplified through the nitrogen cycle.
• Key Processes in the Nitrogen Cycle:
  • Nitrogen Fixation: $N_2$ to ammonia by bacteria.
  • Nitrification: Ammonia to nitrite ($NO<em>2$) then nitrate ($NO</em>3$).
  • Assimilation: Plants absorb nitrate/ammonia.
  • Denitrification: Nitrate back to $N_2$ gas.

Symbiotic Relationships

• Legumes: Host nitrogen-fixing bacteria in roots for nitrogen access.

iClicker Questions on Nitrogen Cycle

• Scenarios testing bacterial roles (e.g., nitrogen fixation, decomposition).
• Removal of denitrifying bacteria leads to soil nitrate accumulation.

Carbon Cycle and Its Dynamics

• Short-term Carbon Cycle: Biotic interactions drive $CO_2$ removal (photosynthesis) and return (respiration).
• Bacteria/archaea roles in carbon dynamics.

Pathways in the Carbon Cycle

• Photosynthesis: $6CO<em>2 + 6H</em>2O \rightarrow C<em>6H</em>{12}O<em>6 + 6O</em>2$
  • Autotrophs convert $CO<em>2$ into organic compounds using light; releases $O</em>2$.
• Respiration: $C<em>6H</em>{12}O<em>6 + 6O</em>2 \rightarrow 6CO<em>2 + 6H</em>2O$
  • Organisms break down organic material, releasing $CO<em>2$ and $H</em>2O$.
• Bacterial degradation of organic matter contributes to $CO_2$ release.

Bacterial Importance Across Environments

• Significant roles in carbon cycling in diverse environments: Chattahoochee River, KSU Campus Green, coastal/deep ocean, montane forest.

Food Webs and Trophic Levels

• Food Web Significance: Understanding chemical and energy exchanges.
• Trophic Level Definition: Position in food web based on energy input proximity.

Trophic Pyramids

• Illustrate energy flow: Only ~10% energy/mass transfers to the next level due to heat, work, waste losses.

Human Impact on Ecological Cycles

• Humans are principal agents in carbon, nitrogen, phosphorus cycles.
• Consequences: global climate change, ocean chemistry alterations, ecological function disruptions.