Biology 1/17

Bio notes

ECOLOGY

Difference Between Population and Community

• Population: A group of individuals of the same species living in a specific area at the same time.
  Example: A group of deer in a forest.

• Community: All the populations of different species living and interacting in the same area.
  Example: Deer, trees, birds, and insects living in the same forest.

2. Biotic and Abiotic Factors

• Biotic Factors: All living organisms in an ecosystem.
  Examples: Plants, animals, fungi, bacteria, etc.

• Abiotic Factors: Non-living physical and chemical elements in an ecosystem.
  Examples: Sunlight, temperature, soil, water, air, minerals.

3. Order Based on Size

• Population < Community < Ecosystem

  • Population: Single species.

  • Community: Multiple populations of different species.

  • Ecosystem: Includes communities and their interactions with abiotic factors.

FOOD WEBS

Identifying Niches Based on How Organisms Get Energy

• Producer (Autotroph): Organisms that make their own food using sunlight (photosynthesis) or chemical energy (chemosynthesis).
  Examples: Plants, algae, cyanobacteria.

• Consumer (Heterotroph): Organisms that get energy by eating other organisms.

  • Herbivore: Eats only plants (Example: Deer, rabbits).

  • Carnivore: Eats only animals (Example: Lions, hawks).

  • Omnivore: Eats both plants and animals (Example: Bears, humans).

• Decomposer: Breaks down dead organisms and returns nutrients to the soil.
  Examples: Fungi, bacteria, worms.

2. Feeding Relationships Between Organisms

• Predator-Prey: One organism (predator) hunts and eats another (prey).
  Example: A lion (predator) hunts a zebra (prey).

• Producer-Consumer: Consumers rely on producers for energy.
  Example: A rabbit eats grass.

3. Interpreting Food Webs

• Food Web: A complex network showing how energy flows through an ecosystem with multiple feeding relationships.

  • Producers form the base.

  • Consumers (herbivores, carnivores, omnivores) and decomposers interact at different levels.

4. Predicting Changes in Food Webs

• Example Scenarios:

  • If producers decline (e.g., due to drought), all other levels are impacted because energy input decreases.

  • If predators are removed, prey populations may grow uncontrollably, leading to overgrazing and ecosystem imbalance.

  • If decomposers are lost, nutrient recycling slows, affecting plant growth.

ENERGY PYRAMIDS

Levels of an Energy Pyramid

1. Producers (Bottom level):

   • Autotrophs like plants, algae, and phytoplankton.

   • They harness energy from the sun through photosynthesis.

2. Primary Consumers (Second level):

   • Herbivores that eat producers.

   • Examples: Grasshoppers, rabbits, zooplankton.

3. Secondary Consumers (Third level):

   • Carnivores or omnivores that eat primary consumers.

   • Examples: Frogs, small fish, snakes.

4. Tertiary Consumers (Top level):

   • Carnivores that eat secondary consumers.

   • Examples: Hawks, wolves, sharks.

10% Rule in Energy Transfer

• Only 10% of energy from one trophic level is transferred to the next.

• The remaining 90% is lost as heat, used for metabolism, or left in waste.
  Example Calculation:

  • Producers start with 10,000 kcal of energy.

    • Primary Consumers receive 1,000 kcal.

    • Secondary Consumers receive 100 kcal.

    • Tertiary Consumers receive 10 kcal.

Key Takeaways

• Energy pyramids emphasize why there are fewer organisms at higher trophic levels (less energy available).

• Top predators rely on energy that has passed through multiple levels, making them more vulnerable to ecosystem disruptions.

NUTRIENT CYCLEs

1. The Carbon Cycle

The carbon cycle describes how carbon moves through the biosphere, atmosphere, hydrosphere, and geosphere.

Key Processes:

• Photosynthesis: Plants, algae, and cyanobacteria take in carbon dioxide (CO₂) from the atmosphere and convert it into glucose (C₆H₁₂O₆) using sunlight.
  Equation: CO₂ + H₂O + sunlight → C₆H₁₂O₆ + O₂

• Respiration: Organisms break down glucose for energy, releasing CO₂ back into the atmosphere.
  Equation: C₆H₁₂O₆ + O₂ → CO₂ + H₂O + energy

• Fossil Fuels & Combustion: Burning fossil fuels (coal, oil, gas) releases stored carbon as CO₂.

• Decomposition: Dead organisms and waste are broken down by decomposers, releasing carbon into the soil or atmosphere.

• Carbon Storage: Carbon can be stored long-term in oceans, soil, and fossil fuels.

2. The Water Cycle

The water cycle describes how water moves through Earth's systems (atmosphere, land, and oceans).

Key Processes:

• Evaporation: Water from lakes, rivers, and oceans turns into vapor due to heat from the sun.

• Condensation: Water vapor cools and forms clouds.

• Precipitation: Water falls to Earth as rain, snow, sleet, or hail.

• Transpiration: Plants release water vapor into the atmosphere from their leaves.

• Runoff: Water flows over the surface of the land, returning to rivers, lakes, and oceans.

Matter Changes in the Water Cycle

• Physical Changes:

  • Liquid → Gas (Evaporation).

  • Gas → Liquid (Condensation).

  • Liquid → Solid (Freezing in certain regions).

• No new matter is created or destroyed, only transformed.

Key Relationships Between Cycles

• The carbon and water cycles intersect through photosynthesis (water and CO₂ are used by plants) and respiration (water and CO₂ are released).

• Combustion and deforestation disrupt both cycles, increasing CO₂ levels and altering water flow patterns.

Global climate change

Global Climate Change Overview

1. Examples of Greenhouse Gases (GHGs)

Greenhouse gases trap heat in the Earth’s atmosphere and contribute to the greenhouse effect. Examples include:

• Carbon Dioxide (CO₂): Released from fossil fuel combustion, deforestation, and industrial processes.

• Methane (CH₄): Emitted from livestock digestion, rice paddies, and landfills.

• Nitrous Oxide (N₂O): Produced by agricultural practices and industrial activities.

• Water Vapor (H₂O): The most abundant GHG, but it is naturally regulated by the water cycle.

• Fluorinated Gases: Synthetic gases (e.g., chlorofluorocarbons or CFCs) from refrigerants and industrial use.

2. The Greenhouse Effect

• Definition: The greenhouse effect is the natural process by which GHGs trap heat in Earth’s atmosphere, keeping the planet warm enough to support life.

• How It Works:

  1. Sunlight reaches Earth’s surface and is absorbed.

  2. The surface radiates heat as infrared energy.

  3. GHGs absorb this heat and re-radiate it, warming the atmosphere.

• Enhanced Greenhouse Effect: Human activities (e.g., burning fossil fuels, deforestation) increase GHG levels, trapping more heat and causing global warming.

3. How Combustion of Fossil Fuels Increases Global Warming

• Fossil Fuels (coal, oil, natural gas) contain carbon stored for millions of years.

• Combustion releases this carbon as CO₂, increasing atmospheric levels.
  Example: Transportation, power plants, and industries contribute large amounts of CO₂.

• Impact: More CO₂ in the atmosphere intensifies the greenhouse effect, leading to higher global temperatures.

4. How Deforestation Increases Global Warming

• Role of Forests: Trees absorb CO₂ during photosynthesis, acting as carbon sinks.

• Deforestation (cutting or burning forests) has two effects:

  1. Fewer Trees: Less CO₂ is absorbed from the atmosphere.

  2. CO₂ Release: Burning or decomposing trees releases stored carbon.

• Impact: Accelerates the buildup of CO₂, exacerbating global warming.

Key Takeaways

• Greenhouse gases, especially CO₂ and CH₄, are major contributors to global warming.

• Combustion of fossil fuels and deforestation disrupt natural carbon cycles, increasing heat trapped in the atmosphere.

• Solutions include reducing emissions, shifting to renewable energy, and reforestation efforts.