Principles of Ecology Study Notes

Principles of Ecology

I. Ecologists Study Relationships

• Ecologists study environments at different levels of organization.

  • Ecology: The study of the interactions among living things and their surroundings.

  • The term comes from the Greek word "oikos" meaning "house".

1. Levels of Organization

• Biologists study nature at various scales ranging from local to global.

• Organism: An individual living thing.

• Population: A group of individuals of the same species that lives in one area.

• Community: A group of different species that live together in one area.

• Ecosystem: Comprises all organisms along with climate, soil, water, rocks, and other non-living components in a specific area.

• Biome: A major regional or global community of organisms characterized by climate conditions and the plant communities that thrive there.

• Biosphere: The global sum of all ecosystems.

II. Ecological Research Methods

• Various methods are utilized in ecological research including observations, experimentation, and modeling.

1. Observation

• The act of carefully watching something over time.

  • Can be either long-term or short-term studies.

  • Surveys are employed to monitor and observe populations.

2. Experimentation

• Experiments can occur in lab settings or in the field.

  • Lab Experiments: Offer more control but may not accurately reflect the complex interactions that occur in nature.

  • Field Experiments: Provide more accurate depictions but are challenging due to numerous variables influencing results.

3. Modeling

• Utilizing computer or mathematical models to depict and simulate nature based on real data.

  • Can determine how one variable impacts another.

  • Allows creation of virtual ecosystems.

III. Biotic and Abiotic Factors

A. Ecosystem Components

• An ecosystem consists of both biotic (living) and abiotic (non-living) factors.

  • Biotic Factors: Includes all living things within the ecosystem.

  • Abiotic Factors: Comprises nonliving elements such as moisture, temperature, wind, sunlight, and soil.

B. Ecological Impact

• Altering one factor in an ecosystem can influence many other factors.

1. Biodiversity

• Definition: The assortment or variety of living things within an ecosystem.

  • The overall amount of biodiversity is dependent on many factors.

  • Tropical rainforests exhibit particularly large biodiversity levels.

2. Keystone Species

• A species possessing an unusually large impact on its ecosystem.

  • Loss of a keystone species can cause ripple effects impacting the entire ecosystem.

  • Example: Beaver alters its habitat for many other species by creating ponds, resulting in increased waterfowl populations, heightened fish populations, and the formation of wetland ecosystems.

IV. Energy in Ecosystems

A. Producers and Consumers

• Producers serve as energy sources for other organisms in an ecosystem.

  • Producers (Autotrophs): Organisms that get their energy from nonliving resources and produce their own food.

  • Consumers (Heterotrophs): Organisms that acquire their energy by consuming other living things, including plants and animals.

B. Photosynthesis

• Nearly all producers acquire energy through sunlight.

  • Process of Photosynthesis: Converts light energy from sunlight into chemical energy stored in carbohydrates.

  • Chemical Equation: $ext{Carbon Dioxide} + ext{Water} + ext{Light} <br>ightarrow ext{Oxygen} + ext{Carbohydrates}$

C. Chemosynthesis

• Definition: Organisms synthesize carbohydrates using chemicals instead of sunlight.

  • Typically occurs in environments such as deep-sea hydrothermal vents and sulfur-rich marsh flats.

  • Can support thriving ecosystems independently of sunlight.

V. Food Chains and Food Webs

A. Food Chain

• A food chain is a sequence linking species through their feeding relationships, representing a flow of energy.

  • Follows connections from one producer to a single chain of consumers.

  • Simplest model for examining energy flow within an ecosystem.

B. Types of Consumers

1. Herbivores: Organisms that consume only plants.

2. Carnivores: Organisms that consume only animals.

3. Omnivores: Organisms that consume both plants and animals.

4. Detritivores: Organisms that feed on detritus (dead organic matter).

5. Decomposers: Organisms that break down organic matter into simpler substances.

   • Examples include fungi and bacteria.

   • Crucial for ecosystem stability by recycling nutrients back into the environment.

6. Dietary Specialization: Organisms may either be specialists, focusing on a single type of food source, or generalists, having a diverse diet.

C. Trophic Levels

• Trophic levels indicate positions in a food chain.

  1. Producers: Always occupy the first level.

  2. Primary Consumers: Next level (herbivores).

  3. Secondary Consumers: Eat primary consumers (carnivores).

  4. Tertiary Consumers: Carnivores that eat secondary consumers.

D. Food Web

• A food web illustrates a complex network of feeding relationships.

  • Each organism may engage in multiple feeding relationships.

  • The stability of a food web is dependent on the presence of producers, which constitute the base of the food web.

VI. Cycling of Matter

A. Water Cycle

• The hydrologic cycle (water cycle) is a circular pathway that water follows on Earth.

  • Water flows from the atmosphere to the surface, below ground, and back, impacting humans and other organisms.

B. Biogeochemical Cycles

• Essential elements for life cycle through ecosystems.

  • Biogeochemical Cycles: Movement of specific chemicals through biological and geological components of an ecosystem.

  • Oxygen Cycle: Involves the interplay between photosynthesis and cellular respiration.

  • Carbon Cycle: The flow of carbon throughout the environment, essential for organic compounds (carbohydrates, proteins, fats, etc.).

    • Major processes include:

      • Cellular respiration releases $CO_2$ into the atmosphere.

      • Photosynthesis utilizes $CO_2$ from the atmosphere.

      • Burning fossil fuels and wood also releases $CO_2$ into the atmosphere.

  • Nitrogen Cycle: Involves converting nitrogen gas in the atmosphere into compounds usable by living organisms.

    1. Nitrogen Fixation: Converting nitrogen gas ($N_2$) into nitrogen compounds such as ammonia ($NH_4$), nitrites ($NO_2$), and nitrates ($NO_3$).

    2. Denitrifying Bacteria: Converts nitrogen compounds back into nitrogen gas ($N_2$).

  • Phosphorus Cycle: Returns phosphorus to the environment; phosphorus serves as a limiting factor for plant growth.

    • Processes include:

      • Weathering of phosphate from rocks, leading to leaching into the soil, where it becomes available to plants.

VII. Pyramid Models

A. Energy Pyramid

• Displays the distribution of energy among the various trophic levels within an ecosystem.

  • Energy flows from sunlight to producers and subsequently to each succeeding trophic level.

  • Some energy is inevitably lost along the way, primarily as heat.

B. Energy Loss

• Energy is used for several biological processes, including movement and growth.

  • Organisms possess inefficiencies in converting food into usable energy.

  • Unused materials are excreted as waste.

C. Biomass

• Biomass refers to the total dry mass of organisms inhabiting a given area.

  • A significant amount of energy is lost when consumers eat producers due to heat and waste.

  • Typically, only $10\%$ of energy is transferred at each trophic level.

D. Other Pyramid Models

• Energy Pyramid: Compares the energy utilized by each trophic level, with the base consisting of producers.

• Biomass Pyramid: Diagram comparing biomass (living tissues) at various trophic levels.

• Pyramid of Numbers: Undertakes to display the number of individual organisms.

• Both biomass and numbers pyramids can appear inverted (e.g., a pyramid of numbers based on a single tree).