Lecture 5 Notes – Principles of Ecology

Energy is fundamental to all biological processes and ecological interactions, driving growth, reproduction, and movement.
It flows through ecosystems in a unidirectional manner, starting from producers, who convert solar energy into chemical energy through photosynthesis, and then transferring to consumers and decomposers.
Understanding energy dynamics is crucial for grasping ecosystem health, stability, and sustainability.

Barry Commoner (founder of modern ecology; wrote The Closing Circle, early 1970s).
He summarized ecology into four laws:

All things are interconnected in obvious and complex ways.
Analogies: the body is an interconnected system; the Earth is similarly networked.
Implications: actions in one area can profoundly affect distant parts (e.g., what happens in the oceans can affect other regions).
Recall: biogeochemical cycles link living and nonliving components across the planet.

Waste has to go somewhere; nature recycles and decomposes, but humans often create non-biodegradable waste.
The question, “Where does your garbage go?” prompts consideration of downstream effects and the fate of waste.
Natural systems decompose and break down matter into smaller components to support life, but many human-made items resist this process.

Billions of years of ecosystem development have created complex, reliable services and systems that support life.
Ecosystem services are categorized as:
- PROVISIONING SERVICES: tangible goods such as water, food, wood, and other resources provided at no direct monetary cost.
- REGULATING SERVICES: maintenance of water, air, and soil quality; flood and disease control; pollination; many are invisible and thus underappreciated until damaged.
- CULTURAL SERVICES: recreation, mental and physical health benefits, aesthetics, inspiration for culture/art/design, spiritual experience, sense of place.
While technology can improve aspects of nature, Commoner warned that significant changes to natural systems are likely detrimental.

Nothing comes from nothing; everything we do has costs.
Examples of hidden costs: trash disposal, groundwater contamination, disruption of ecological self-maintenance.
Benefits must be weighed against environmental costs and long-term sustainability.

Ecology provides a scientific context for evaluating environmental issues.
Clear distinctions:
- ECOLOGY: the scientific study of the distribution and abundance of organisms.
- ENVIRONMENTALISM: advocacy for the protection or preservation of the natural environment.
Ecologists ask questions about factors affecting distribution and abundance and study how interactions between organisms and the environment influence species distribution, nutrient cycling, and population growth.

ABIOTIC COMPONENTS: nonliving chemical and physical factors (e.g., temperature, light, water, nutrients).
BIOTIC COMPONENTS: all living organisms in the environment (plants, animals, microbes).

Focus: behavioral, physiological, and morphological ways individuals interact with their environment.
Example: Karner blue butterfly (an endemic species) – lives only in open habitats with few trees/shrubs (pine barrens and oak savannas) and can lay eggs only on host plant Lupine.

POPULATION: a group of individuals of the same species living in a specific geographic area.
POPULATION ECOLOGY examines factors affecting population size and composition.
Example: Karner blue butterfly population monitoring due to its federally endangered status.

COMMUNITY: all the organisms of all species in a particular area.
Examines interactions between species and effects of predation, competition, disease, and disturbance on community structure.
Example: Karner blue butterfly larvae form mutualistic relationships with ants; ants gain carbohydrate-rich secretions from larvae, increasing larval survival.

ECOSYSTEM: all biotic components in an area plus the abiotic components (living and nonliving).
Studies energy flow and cycling of chemicals among biotic and abiotic components.
Research questions focus on resource limitation and movement of resources (nutrients) through the system.
Example context: oak-pine barren habitat characterized by natural disturbance and nutrient-poor, nitrogen-low soils; nutrient availability affects plant distribution.

Habitat: open oak-pine barren with low nitrogen and nutrient-poor soils.
Mutualism: Karner blue larvae form mutualistic relationships with ants; ants receive carbohydrate-rich secretions, increasing larval survival.
Host plant: Wild lupine is the host plant for the Karner blue butterfly.
Distribution and abundance are shaped by habitat availability, plant-nutrient status, and interspecific interactions.

Definition: study of past and present distributions of species and ecosystems in geographic space and through geological time.
Organisms and communities often vary along geographic gradients of latitude, elevation, isolation, and habitat area.
Biogeography helps understand how animals and plants have altered landscapes over time.
Factors limiting distribution include:
- Behavior and habitat selection (habitat choice influences where species occur).

Biotic factors:
- Negative interactions such as predation, parasitism, disease, and competition can limit survival and reproduction.
- Predator removal experiments can reveal how predators influence prey distribution.
- Absence of other species (e.g., specific pollinators or prey) can limit distribution.
Abiotic factors:
- Temperature, water availability, and sunlight broadly shape global distributions.

Akre B, Brainard J, Goose H, Rogers-Estable, and Stewart R (2011). Introduction to Environmental Science, FlexBook Platform, USA.
Allaby M. (1996). Basics of Environmental Science, 2nd edn. Routledge, London.
Saravanan K, Ramachandran S, and Baskar R (2005). Principles of Environmental Science & Technology, New Age International (P) Ltd., Publishers, New Delhi.
Singh Y.K (2006). Environmental Science, New Age International (P) Ltd., Publishers, New Delhi.