ECOLOGY_S

ECOLOGY

Introduction

PFAS: Forever Chemicals

• Per- and polyfluoroalkyl substances (PFAS) known as "forever chemicals" due to their persistence in the environment.

• They do not break down and can accumulate in living organisms, leading to various health issues.

Ecological Effects of PFAS

• Biomagnification: Higher concentrations in predators such as otters, killer whales, and polar bears due to lower concentrations in their prey.

• Health Impacts: Weaker immune systems in animals, toxicity in air, water, and soil—from Antarctica to the Arctic.

• Related diseases include high cholesterol, ulcerative colitis, thyroid disease, testicular cancer, kidney cancer, and pregnancy-induced hypertension.

Rachel Carson and Environmental Awareness

• Rachel Carson's influential book "Silent Spring" (1962) warned about pesticide abuse and its global dangers, promoting ecological awareness.

• Highlights the roles of stakeholders in ecology: individuals, consumers, government entities, corporations, and scientists.

ECOLOGICAL LEVELS

Levels of Biological Organization

1. Population Ecology

   • Focuses on groups of organisms of the same species in a specific area.

   • Studies dynamics such as population size and influencing factors.

2. Community Ecology

   • Considers all individuals from different species interacting in a defined area.

   • Examines relationships such as competition, cooperation, and predation.

3. Ecosystem Ecology

   • Investigates communities of organisms interacting with their physical environment.

   • Analyzes energy flow and nutrient cycling within ecosystems.

Biotic and Abiotic Factors

• Biotic Factors: Living components of an environment that affect organisms.

• Abiotic Factors: Non-living environmental factors like temperature, soil composition, and rainfall that shape an organism's habitat.

• Biotope: A specific area with uniform environmental conditions supporting a community.

ABIOTIC FACTORS

• Key Factors: Energy (via photosynthesis), temperature, water, nutrients, and various terrestrial/aquatic conditions (e.g., salinity, tides).

BIOSPHERE

• The biosphere encapsulates all ecosystems on Earth.

• It is characterized by the emergence of new properties at each level of biological organization.

ECOLOGY: Population Dynamics

Population Ecology

• Encompasses study of:

  • Changes in population size, density, and distribution.

  • Factors influencing these variations.

Density and Dispersion

1. Population Density

   • Number of individuals per unit area.

   • Methods of estimation include counting nests or tracking harvests.

2. Population Dispersion

   • Clumped Distribution: Resources are unevenly distributed, leading to groups of individuals.

   • Uniform Distribution: Results from interactions among individuals, such as territorial behavior.

   • Random Distribution: Rare; influenced by habitat conditions.

Life Tables

• Track survivorship, allowing ecologists to identify vulnerable age groups for conservation.

Survivorship Curves

• Graphs plotting alive individuals against age.

  • Type I: High survivorship until later life stages.

  • Type II: Constant mortality rate.

  • Type III: High mortality in the early stages.

EXPONENTIAL GROWTH

• Exponential growth occurs under optimal conditions.

• Given by the formula G = rN, where G is the growth rate, N is the population size, and r is the per capita growth rate.

• Illustrates a J-shaped curve indicating growth acceleration as population increases.

LOGISTIC GROWTH

• Growth is limited by environmental factors leading to stabilization around the carrying capacity (K).

• S-shaped curve reflects the effects of resources and population size on growth rate.

DENSITY-DEPENDENT AND DENSITY-INDEPENDENT FACTORS

• Density-Dependent Factors: Affect population size based on density, such as limited resources leading to lower reproduction and higher mortality.

• Density-Independent Factors: Abiotic factors that impact populations regardless of size (e.g., natural disasters).

Sustainable Resource Management

• Focuses on consistent harvesting that does not deplete populations.

COMMUNITY ECOLOGY

Interspecific Interactions

• Relationships between different species influence community structure and dynamics:

  • Competition: Negative effects on both species competing for limited resources.

  • Mutualism: Beneficial for both species involved.

  • Predation: One species benefits (predator) and the other is harmed (prey).

  • Herbivory: An animal consumes plants, often leading to adaptations in plants, such as chemical defenses.

  • Parasitism: Parasites benefit at the expense of their hosts (e.g., aphids).

Keystone Species

• A species with a disproportionately large impact on its community, essential for maintaining ecological balance.

Food Webs and Trophic Structure

• Illustrates feeding relationships among organisms in different trophic levels, including producers, consumers, and decomposers.

BIODIVERSITY

Importance and Disturbance

• Biodiversity is affected by disturbances which can drastically alter community composition.

• Events like storms, fires, and human activities lead to ecological succession—changing species composition over time.

Nutrient Cycles

• Nitrogen Cycle: Dependent on bacteria for fixation and recycling. Involves various processes that convert nitrogen through different forms from the atmosphere to the soil and back.

• Phosphorus Cycle: Limited by the availability of phosphates, important for organic compounds.

ISSUES RELATING TO NITROGEN

• Excess nitrogen can lead to environmental issues such as acidification, decreased biodiversity, and eutrophication.

ECOLOGICAL LEVELS

Levels of Biological Organization

Population Ecology

• Focuses on groups of organisms of the same species in a specific area, often referred to as a population.

• Studies dynamics such as population size (the total number of individuals in the population), density (the number of individuals per unit area), dispersion (the spread of individuals within the area), and various influencing factors (birth rates, death rates, immigration, emigration).

• Employs methods like demographic studies and modeling to understand population growth trends and species interactions.

Community Ecology

• Considers all individuals from different species interacting in a defined area, forming a biological community.

• Examines relationships that drive community dynamics such as competition (where species vie for the same limited resources), cooperation (mutualistic relationships where species benefit), and predation (where one species preys upon another).

• Investigates phenomena such as community structure, species richness, and the effects of invasive species on native biodiversity.

Ecosystem Ecology

• Investigates how communities of organisms interact with their physical environment, encompassing both biotic (living) and abiotic (non-living) components.

• Analyzes energy flow (the transfer of energy from one organism to another through food webs) and nutrient cycling (the movement and exchange of organic and inorganic matter within ecosystems).

• Emphasizes the importance of ecosystem services, such as pollination, water purification, and carbon storage.

Biotic and Abiotic Factors

• Biotic Factors: Living components of an environment, including plants, animals, microorganisms, and interactions between different species that affect ecological dynamics. These interactions can include competition, predation, mutualism, and parasitism.

• Abiotic Factors: Non-living environmental factors like temperature, soil composition, pH, humidity, water availability, and sunlight that shape and influence an organism's habitat. These factors are crucial in determining which species can survive in different environments.

• Biotope: A specific area with uniform environmental conditions supporting a community, serving as a habitat for organisms adapted to those specific conditions.

ABIOTIC FACTORS

• Key Factors:

  • Energy: Primarily from the sun, captured via photosynthesis by autotrophs, which forms the energy base for ecosystems.

  • Temperature: Influences metabolic rates and biological activity; varies widely across ecosystems.

  • Water: Essential for all living organisms, affecting survival, productivity, and habitat characteristics.

  • Nutrients: Elements like nitrogen and phosphorus that are critical for plant growth and are cycled through ecosystems.

  • Various terrestrial/aquatic conditions: For example, salinity in aquatic ecosystems and tides, which impact species distribution and ecosystem health.

BIOSPHERE

• The biosphere encapsulates all ecosystems on Earth, representing the sum of all living organisms and their interactions with each other and the environment.

• It encompasses land, water, and the atmosphere, and is characterized by the emergence of new properties at each level of biological organization, indicating complex interactions that sustain life worldwide.

ECOLOGY: Population Dynamics

Population Ecology

• Encompasses the comprehensive study of:

  • Changes in population size over time due to birth rates (the rate at which new individuals are added), death rates (the rate at which individuals leave the population), immigration (movement into an area), and emigration (movement out of an area).

  • Influencing factors such as resource availability, environmental conditions, and species interactions that can enhance or limit population growth.

Density and Dispersion

Population Density

• Number of individuals per unit area, which can provide insights into the health of a population and its resource needs.

• Methods of estimation include direct counting (e.g., in small areas), indirect methods such as counting nests or tracking harvests, and mathematical models to project population sizes.

Population Dispersion

• Clumped Distribution: A common distribution where resources such as food or living space are unevenly distributed, leading individuals to group together for better access to these resources.

• Uniform Distribution: Occurs when individuals are evenly spaced, often as a result of territorial behavior or social interactions that minimize overlap.

• Random Distribution: Rare in nature, this occurs when individuals are distributed unpredictably; usually influenced by habitat conditions.

Life Tables

• Track survivorship, which provides critical data allowing ecologists to identify vulnerable age groups within populations for conservation efforts and understand life expectancy patterns.

Survivorship Curves

• Graphs plotting the number of alive individuals against age, showing different patterns of mortality:

  • Type I: High survivorship until later life stages (e.g., humans).

  • Type II: Constant mortality rate throughout life (e.g., some birds).

  • Type III: High mortality in the early stages of life (e.g., many fish).

EXPONENTIAL GROWTH

• Exponential growth occurs under optimal conditions with abundant resources and no significant limitations, following the formula G = rN, where G is the growth rate, N is the population size, and r is the per capita growth rate.

• This model typically results in a J-shaped curve representing rapid growth acceleration as the population increases without limitation.

LOGISTIC GROWTH

• Growth is limited by environmental factors, leading to stabilization around the carrying capacity (K), the maximum population size that an environment can sustain indefinitely.

• This reflects an S-shaped curve, indicating that as resources become scarce, growth slows and population levels off.

DENSITY-DEPENDENT AND DENSITY-INDEPENDENT FACTORS

• Density-Dependent Factors: These are biotic factors that can change in regulatory strength based on population density, such as competition for food, predation pressure, and disease spread.

• Density-Independent Factors: Abiotic factors like natural disasters (floods, earthquakes), weather, and climate changes that impact populations regardless of their density.

Sustainable Resource Management

• Focuses on practices that allow for consistent harvesting of resources without depleting populations or causing long-term degradation of ecosystems.