ecology

Levels of Organization

• Organism: An individual living thing.

• Population: A group of individuals of the same species living together.

• Community: A group consisting of different species living in a particular area.

• Ecosystem: Comprises all biotic (living) and abiotic (nonliving) factors in a specific area.

• Biome: A major regional or global community characterized by climate conditions and plant communities.

• Biosphere: All the ecosystems on Earth; the global sum of all ecosystems.

Biotic vs. Abiotic Factors

• Biotic Factor: Living things that play important roles in an ecosystem, such as plants, animals, fungi, and bacteria.

• Abiotic Factor: Nonliving things that impact the survival and reproduction of organisms in an environment, such as temperature, water, soil, and sunlight.

Habitat vs. Niche

• Habitat: Describes the biotic and abiotic factors of the area where an organism lives.   - Example Question: What would the habitat of a polar bear be?

• Niche: Refers to all the factors that an organism needs to survive, essentially describing how it lives.   - Example Question: What would the niche of a polar bear be?

Keystone Species

• A keystone species is crucial in maintaining the structure of an ecological community.   - Analogy: Similar to the keystone that holds up an arch, the keystone species can sustain an entire ecosystem.   - Ripple Effect: If a keystone species is impacted, it usually results in consequences that can alter the entire ecosystem.

Energy in Ecosystems

• All ecosystems fundamentally depend on autotrophs because they provide the energy necessary for survival.   - Most autotrophs are photosynthetic (requiring sunlight).   - Chemosynthetic organisms produce food from inorganic compounds (e.g., found near deep-sea vents).

Food Chains and Food Webs

• A food chain is a straightforward representation of energy flow in an ecosystem, represented through feeding relationships.   - Trophic Levels: Levels of nourishment in a food chain where energy moves from lower trophic levels (producers) to higher levels (consumers).

• A food web illustrates complex networks of feeding relationships across an ecosystem.   - Constituted by multiple interconnected food chains.

Feeding Strategies and Trophic Levels

• Trophic Levels explained:   - 1st Trophic Level: Producers - (e.g., plants)   - 2nd Trophic Level: Primary Consumers (1°) - Herbivores (e.g., rabbits, squirrels)   - 3rd Trophic Level: Secondary Consumers (2°) - Carnivores (e.g., foxes)   - 4th Trophic Level: Tertiary Consumers (3°) - Top predators (e.g., hawks, owls)

Energy Pyramid

• Energy in ecosystems is lost as it is transferred between trophic levels; generally:   - 90% of energy is lost as heat.   - 10% is available for the next trophic level.

• Energy pyramids compare energy utilized by producers with energy consumed by primary, secondary, and tertiary consumers.

• Correlation between energy pyramids, biomass pyramids, and pyramids of numbers should be understood.

Generalized Energy Pyramid

• An ecological example with four trophic levels showcasing energy use per level.   - First Order Carnivores: 10 units   - Second Order Carnivores: 1 unit   - Deposit Feeders: 100 units   - Phytoplankton: 1000 units

• Assumes an ecological efficiency of 10% at each level.

Pyramid of Numbers

• Distribution of organisms shows:   - 1 Osprey   - 10 Northern Pike   - 100 Perch   - 1000 Bleak   - 10,000 Freshwater Shrimp

Biomass Pyramid

• Example of a hypothetical biomass pyramid for aquatic ecosystems:   - Top Carnivore (Shark): 100 kg   - Mid-level Carnivores (Large Fish): 1,000 kg   - Herbivores (Zooplankton): 100,000 kg   - Primary Producers (Phytoplankton): 1,000,000 kg

Biomagnification

• Definition: The increase in concentration of substances (like pollutants) in the bodies of organisms at successively higher levels of the food chain.

• Process: E.g., Phytoplankton absorb PCBs, which are then concentrated by zooplankton, leading to higher concentrations in fish and, eventually, large mammals and humans.   - Diagram representing this process indicates risks of mercury and DDT concentrations at various trophic levels.   - Example: Bald Eagles and DDT accumulation.

Biogeochemical Cycling

• Nutrients circulate within the ecosystem through biogeochemical cycles involving   - Producers: Convert inorganic nutrients to organic materials.   - Consumers: Utilize organic materials.   - Decomposers: Breakdown organic materials back into inorganic forms.

Cycles of Matter

• Define Earth as a closed system.   - Water Cycle: Involves evaporation, condensation, transpiration, and precipitation.   - Carbon Cycle: Carbon circulates between the environment and organisms, critical for building organic matter.   - Nitrogen Cycle: Converts nitrogen into usable forms like ammonia or nitrate through nitrogen fixation.   - Phosphorus Cycle: Essential for organisms; phosphorus is a key component of ATP, DNA, and lipids, affecting crop yield when insufficient.

Survivorship Curves

• Graphical representation of the number of survivors from a birth cohort over time; aids in understanding reproductive strategies.

• Type 1: High survival until old age (e.g., large mammals).

• Type 2: Constant rate of survival (e.g., birds, small mammals).

• Type 3: High mortality early in life but high number of offspring later (e.g., fish, amphibians).

Reproductive Strategies

• Two primary scenarios based on environmental stability and resource availability:   - Unstable Environment:   - Usually features small organisms with high offspring production and fast maturation.   - Typically corresponds with Type III survivorship curves.   - Stable Environment:   - Generally features larger organisms, few offspring, and longer life expectancy.   - Usually corresponds with Type I or II survivorship curves with significant parental care.

Population Dynamics: Factors Affecting Population Size

• Changes in population size are influenced by various factors including:   - Immigration: Influx of individuals increases population size.   - Births: New individuals increase population size.   - Emigration: Outflux of individuals decreases population size.   - Deaths: Loss of individuals decreases population size.   - Formula:   $ΔSize = (Births + Immigration) - (Deaths + Emigration)$

Growth Rate Formulas

• Understand key population growth metrics and their calculations:   - Birth Rate per capita (b): $b = rac{B}{N},$ where B is total births, N is population size.   - Death Rate per capita (m): $m = rac{D}{N},$ where D is total deaths.   - Growth Rate: $ext{Growth Rate} = (B + I) - (D + E)$.   - Growth Rate per capita (r): $r = b - m$.   - Population Density: $ext{Density} = rac{N}{ ext{Area}}$.

Age Structure Diagrams

• Important for interpreting population data and understanding demographic transition models.

Demographic Transition Model

• Reflects the transition from high birth and death rates to low rates as a country develops from pre-industrial to industrialized economic systems.

Symbiotic Relationships

• Symbiosis: Close ecological relationships between organisms from different species, dividing into three main types:   - Mutualism (+/+): Benefit to both organisms.   - Commensalism (+/0): Benefit to one organism while the other is unaffected.   - Parasitism (+/-): Benefit to one organism at the expense of the other (host).

Competition in Ecosystems

• Occurs when organisms compete for the same limited resources (food, space, mates).   - Intraspecific Competition: Competition within the same species.   - Interspecific Competition: Competition between different species.

Competitive Exclusion Principle

• States that if two species compete for the same resources, one will outcompete the other, leading to one species being pushed to extinction or a different niche.   - Outcomes include Niche Partitioning (utilizing different resource types) and Divergent Evolution (leading to different species traits).

Succession in Ecosystems

• Succession involves biotic changes that repair or establish ecosystems:   - Primary Succession: Development of a community in an uninhabited area starting from bare rock (pioneered by species like lichens).   - Secondary Succession: Restoration of a community after a disturbance, where soil is intact.

Pollution**

• Defined as any undesirable substance in air, water, or soil termed pollutants that adversely affect the quality of those resources.   - Air Pollution: From emissions leading to issues like smog and acid rain.   - Water Pollution: Threats from chemicals and waste products affecting aquatic ecosystems.

Biodiversity Crisis

• The decline in biodiversity levels can be categorized into three main areas:   - Ecosystem Diversity: Different ecosystems (e.g., rainforests).   - Species Variety: Amount of biodiversity within communities.   - Genetic Variation: Within populations leading to reduced numbers and genetic diversity.   - Possible emergence of a 7th Mass Extinction driven by human activities.

Threats to Biodiversity (H.I.P.P.O.C)

• H: Habitat Loss/Destruction - Loss of natural habitats (deforestation, fragmentation).

• I: Invasive/Introduced Species - Non-native species disrupt ecosystem balance.

• P: Population Growth (Human) - Intensifying human pressures on resources.

• P: Pollution - Chemical and waste-related ecosystem impacts.

• O: Overexploitation - Harvesting species beyond their recovery rates (e.g., overfishing).

• C: Climate Change - Ongoing climate alterations affecting habitability of various ecosystems.

Human Impact on Populations

• Examination of human consumption of nonrenewable resources and impacts on biodiversity and ecosystem health.   - Explanation of renewable resources and sustainable practices to promote ecological health .

Biodiversity Importance and Conservation

• Highlights the significance of biodiversity for ecosystem functioning, potential medicine and food sources, and the overall stability of ecosystems.

• Legislation aimed at protecting biodiversity mentioned (e.g., Endangered Species Act, Clean Water Act, etc.). Previous strategies include sustainable development and restoration projects.