Ecology Unit Notes 2025-2026

Ecology Unit Notes 2025-2026

Introduction to Chemistry

• Atom: The fundamental building blocks of matter.

• Proton: A positively charged particle that determines the identity of an atom.

• Element: Different types of atoms that cannot be broken down into simpler substances.

• Compound: Composed of 2 or more different atoms that are chemically bonded together.

• Molecule: Composed of 2 or more atoms, which can be the same or different, that are bonded.

• Reactants: Substances that go into a chemical reaction.

• Products: Substances that come out of a chemical reaction.

Elements in the Human Body

• Elements in order of abundance in the human body:

  • O = Oxygen

  • C = Carbon

  • H = Hydrogen

  • N = Nitrogen

  • Ca = Calcium

  • P = Phosphorus

Abiotic vs. Biotic Factors

• Biotic: Referring to living components of an ecosystem.

  • Examples: Animals, plants, fungi, and bacteria.

• Abiotic: Referring to non-living components of an ecosystem.

  • Examples: Air, water, soil, rocks, temperature.

• Element Cycling: Elements cycle between biotic and abiotic systems across ecosystems.

Carbon Cycle

• Definition: The circulation of carbon in various forms throughout nature.

• Importance: Carbon forms a part of all organic compounds, many of which are essential for life on Earth.

Water Cycle

• Definition: The continuous process by which water is circulated throughout the Earth and atmosphere.

• Processes Involved:

  • Evaporation

  • Condensation

  • Precipitation

  • Transpiration (by plants and animals).

Nitrogen Cycle

• Definition: A process that transforms inert atmospheric nitrogen into a usable form for plants, animals, and other organisms.

  • Inert: Chemically unreactive substances.

Nitrogen Fixation

• Process: Converting atmospheric nitrogen ($N<em>2$) into usable forms like ammonium ($NH</em>4^+$) and nitrates ($NO_3^-$).

Denitrification

• Definition: The conversion of usable nitrogen (nitrates, $NO<em>3^-$) back into atmospheric nitrogen ($N</em>2$).

  • Conditions: Commonly occurs in hydric or wet soils rich in organic matter.

Trophic Levels

• Definition: A hierarchical structure that groups organisms based on how they obtain energy within a food web.

• Trophic Levels:

  • Primary Producers: Make food for themselves and others through photosynthesis.

  • Examples: Wheat grass, aspen.

  • Primary Consumers (Herbivores): Obtain energy by eating producers.

  • Examples: Pronghorn, beaver, elk.

  • Secondary Consumers (Carnivores and Omnivores): Obtain energy by consuming primary consumers or when consuming both producers and consumers.

  • Examples: Coyote, brown bear.

  • Carnivores: Organisms that feed primarily on other consumers.

  • Example: Grey wolf.

  • Apex Predators: Organisms that have no known natural predators.

  • Example: Grey wolf.

Energy Flow and the 10% Rule

• 10% Rule: Approximately 10% of energy at one trophic level is available to the next level.

• Energy Usage: 90% of an organism's energy is utilized for:

  • Movement

  • Maintenance

  • Growth/Production

  • Lost as heat.

Population Dynamics

• Population: A group of organisms of the same species that breed with each other and inhabit the same area at the same time.

Quadrat Sampling

• Definition: A method used to measure the distribution and abundance of organisms, particularly in slow-moving or non-moving populations.

• Purpose: To estimate population sizes without counting every individual, relying on sampled quadrats to extrapolate to the whole population.

Mark Recapture Method

• Purpose: To estimate population sizes of faster-moving organisms.

• Process:

  • Capture a small number of individuals, mark them safely, and release.

  • Later, capture another sample, record how many are marked.

  • Utilize the formula:
    $rac{ ext{Number marked in recapture} }{ ext{Total captured in recapture} } = rac{ ext{Number marked in original capture} }{ ext{Total estimated population} }$

  • Example: If 10 turtles are marked and then 5 of those are recaptured, the population size can be estimated:

  • 
    $5 = rac{10}{x} <br>ightarrow 5x = 10 <br>ightarrow x = 20$

Carrying Capacity

• Definition: The maximum number of organisms that an environment can consistently support over time.

• Logistic Growth Model: Describes the growth of populations as they reach carrying capacity (K).

  • Stages:

  • Exponential growth phase

  • Lag phase

  • Deceleration phase

  • Stable equilibrium phase.

Limiting Factors

• Definition: Any factors that limit a population's size and restrict its growth, such as food, water, and space.

Density Dependence vs. Density Independence

• Density Dependent Factors: Factors that have effects on population based on its density, such as disease, competition, and predation.

• Density Independent Factors: Factors that affect population sizes regardless of population density, such as natural disasters (e.g., floods, wildfires).

Ecological Roles & Interactions

• Ecological Niche: The role an organism plays in its habitat or ecosystem.

• Examples of Organismal Niches:

  • Goldfinch and its feeding behavior in various tree branches.

  • Flamingos feeding on small invertebrates and algae.

  • Dabbling Ducks that tip to reach aquatic plants and insects.

  • Avocets feeding through sweeping motions in shallow water.

  • Oystercatchers prying open bivalve shells to find food.

  • Plovers hunting randomly on beaches and grasslands.

Biomes and Biodiversity

• Biome: Large areas characterized by their vegetation, soil, climate, and wildlife.

  • Types of biomes include aquatic, grassland, forest, desert, and tundra.

• Biodiversity: The variety of life within a specific environment.

  • Importance: Higher biodiversity increases ecosystem resilience against environmental changes.

Ecosystem Services

• Definition: All positive benefits that wildlife or ecosystems provide to people.

• Types of Ecosystem Services:

  • Supporting Services: Necessary for the production of other services (e.g., soil formation, nutrient cycling).

  • Provisioning Services: Benefits extracted from nature (e.g., food, water, pharmaceuticals).

  • Regulating Services: Vital for human life (e.g., water filtration, climate regulation).

  • Cultural Services: Non-material benefits contributing to culture (e.g., spiritual uplift, recreation).

Species Interactions

• Native Species: Species that naturally live and thrive in a specific ecosystem.

• Invasive Species: Introduced organisms that proliferate and negatively alter their new environments.

• Types of Interactions:

  • Predation: A (+/-) interaction where the predator kills and consumes the prey.

  • Intraspecific Competition: A (-/-) competition among members of the same species for resources (e.g., deer for mates).

  • Interspecific Competition: A (-/-) competition between different species for resources (e.g., lions and cheetahs competing for prey).

Symbiosis

• Definition: An ecological relationship between two species living in close proximity.

• Types:

  • Mutualism (+/+): Both species benefit (e.g., pollinators and plants).

  • Parasitism (+/-): One species benefits (the parasite), while the other is harmed (the host) but not killed.

  • Commensalism (+/0): One species benefits while the other is unaffected.