Ecosystems and Biodiversity Review

Effective Studying Tips

• Use self-tests on Canvas to assess understanding of lecture concepts.

Ecosystems

• Defined as all organisms living in a community (biotic factors) along with abiotic factors they interact with.

• Key processes include energy flow and nutrient cycling.

Biomes

• Regions characterized by distinct abiotic factors and dominant vegetation types.

• Biomes help study larger ecosystem patterns.

Learning Outcomes

• Understand and define ecosystems, biomes, and biodiversity.

• Analyze biodiversity on three levels.

• Recognize endemic species and threats to biodiversity.

• Explain energy and nutrient flow in ecosystems and impacts on biological processes.

• Draw energy, biomass, and number pyramids, and illustrate the nitrogen biogeochemical cycle.

Biodiversity Levels

1. Genetic Diversity: Total genetic information within a species or community.

2. Species Diversity: Number of different species in an area, assessing through species richness and relative abundance.

3. Ecosystem Diversity: Variety including biotic and abiotic components.

Measuring Biodiversity

• Species Richness: Count of different species within a community.

• Species Diversity: Accounts for the count and relative abundance of each species.

  • Example: If a community has 2 species with uneven abundance, diversity is low; 4 species with even abundance indicates high diversity.

Endangered Species Classification

• Endangered Species: In danger of extinction across their range (e.g., orangutan).

• Threatened Species: Likely to become endangered soon (e.g., black rhino).

• Endemic Species: Unique to one location and not found elsewhere (e.g., purple frog).

Biodiversity Threats

• The IUCN's Red-List monitors the health of global biodiversity, noting that some species, especially plants and fungi, are underrepresented.

• Threats include:

  • Habitat Loss: Destruction or degradation of natural habitats.

  • Invasive Species: Non-native species that spread and threaten local ecosystems.

  • Overexploitation: Unsustainable removal of species for human use.

  • Pollution: Chemicals altering ecosystems.

  • Climate Change: Leads to shifting ecosystems and species' extinctions.

Threats Breakdown by Habitat

• Percentage of endangered species affected by habitat loss, invasive species, over-exploitation, pollution, and climate change is notable across terrestrial, freshwater, and marine environments.

Habitat Loss

• Caused by human activities leading to reduced quality of natural habitats.

• Habitat Fragmentation: Smaller habitats that can't support the same biomass as larger, contiguous habitats.

  • Example: Wildlife corridors can reconnect fragmented habitats.

Invasive Species Example

• Kudzu: Introduced for erosion control, now invasive in North America.

• Zebra Mussels: Disrupt local aquatic ecosystems.

Overexploitation

• Dominant threat to marine species; highlights the need for sustainable practices in fishing to protect ecosystems and communities.

Pollution

• Release of chemicals and waste affects both biotic and abiotic aspects of ecosystems. Historic reductions in industrial emissions show successful pollution control.

Energy Flow in Ecosystems

• Energy enters ecosystems primarily through primary producers that convert sunlight into chemical energy.

• Only a fraction of solar energy is captured (Gross Primary Productivity, GPP) and used for biomass (Net Primary Productivity, NPP).

• Energy Transfer Efficiency: Typically only 10% of energy is transferred between trophic levels, creating pyramids of productivity.

  • Example: 300 trout needed to sustain one human, eaten frogs, which consume grasshoppers that feed on grass.

Nutrient Cycling in Ecosystems

• Explained in detailed lectures focusing on how nutrients move and recycle within ecosystems.

Summary of Key Learnings

• Biodiversity encompasses genetic, species, and ecosystem levels.

• Major threats: habitat loss, invasive species, overexploitation, pollution, climate change.

• Energy flow and nutrient cycling are governed by physical laws, with energy transfer between trophic levels showing low efficiency (~10%).

Additional Notes:

• Recognize the importance of studying biodiversity for conservation efforts.

• Analysis of climate change's impact on species extinction risk highlights the urgency of addressing these environmental challenges.

• Gross Primary Productivity (GPP): Refers to the total amount of solar energy captured by primary producers (such as plants) through photosynthesis over a specific period. It quantifies the overall energy converted into organic matter before any energy is used by the producers themselves for respiration or other biological processes. High GPP indicates a robust and productive ecosystem where a substantial amount of energy is being harnessed from the sunlight.

• Net Primary Productivity (NPP): Represents the amount of energy that remains available after the primary producers have utilized some of the captured energy for their metabolic processes. It is calculated by subtracting the energy used by primary producers for respiration from the GPP:
  NPP = GPP - ext{Respiration}
  NPP is crucial as it indicates the energy available to support the next trophic levels, such as herbivores and carnivores, making it a key factor in ecosystem productivity and stability.