Introduction to Ecology

What is Ecology

• Definition: Ecology is the scientific study of interactions between organisms and their environment.

• Connections: Events in the natural world are interconnected.

  • Learning Objective: Explain how interactions between organisms and their environment can affect other organisms and potentially lead to unexpected consequences.

Amphibian Deformities Case Study

• Case Study Origin: High incidence of deformities observed in amphibians, specifically in a pond in Minnesota, 1995.

  • Elementary students: Out of 22 leopard frogs, 11 had missing or extra limbs.

  • Deformity rate of 30-40% seen within one pond, with occurrences in 46 states, up to 90% affected.

  • Targeted species: 60 types of frogs, salamanders, and toads.

  • Research Outcome: This incident sparked a broader scientific interest and led to further studies.

Key Concepts in Ecology

Initial Perspectives on Ecology

• Early Ecological Views:

  • Concept of a "balance of nature" where natural systems are treated as stable and revert after disturbances.

  • Role of species: Each species has a distinct role that contributes to maintaining this equilibrium.

• Modern Views:

  • Disruptions are seen as leading to new states in nature, emphasizing that species functions are often redundant.

  • Recognition that events in nature are interconnected.

Scientific Process in Ecology

1. Ecologists evaluate competing hypotheses about natural systems with observations, experiments, and models.

   • Learning Objectives:

     • Compare advantages and disadvantages of field observations, field experiments, and lab experiments in testing ecological hypotheses.

     • Understand the importance of hypotheses, controls, replication, and data analysis.

Observations and Experiments in Ecology

• Field Observations: Utilize real-world scenarios to collect data.

• Field Experiments: Implement tests in natural settings, providing real-time interactions.

• Lab Experiments: Isolation and control of variables due to predictable conditions.

• Factors include:

  • Hypothesis formulation

  • Control mechanisms

  • Replication of tests to ensure data reliability

Amphibian Deformities: The Case of Ribeiroia

• Ribeiroia trematode flatworms:

  • Connection made by Ruth and Sessions (1986) with deformed Pacific tree frogs and long-toed salamanders. All infections were associated with Ribeiroia.

  • Johnson et al. surveyed 35 ponds in California; four identified ponds had frogs with deformities linked to snails that acted as intermediate hosts for Ribeiroia.

Life Cycle of Ribeiroia

• Stages of Ribeiroia Lifecycle:

  1. Eggs hatch into Miracidia.

  2. Infected snails host Cercariae.

  3. Frogs infected with Metacercaria (cysts).

• Proxy interrelation of the Ribeiroia with amphibians establishes a cause-effect scenario where tadpoles develop deformities.

Experimental Designs and Mean Outcomes

• Controlled experiments verify assumptions like the relationship between deformities and parasite infection rates.

  • Groups treated with parasites vs. control groups show 0% deformation with no parasites, while others exhibit significant deformation as parasite numbers increase.

• Statistical Analysis: Mean +/- standard deviation encapsulates outcomes of experiments, narrating the connection between parasite loads and survival rates of tadpoles.

Impact of Environmental Factors

• Other Factors Contributing to Decline:

  • Stuart et al. (2004) discussed habitat loss as a primary cause for 183 species.

  • Overexploitation contributed to declines in 50 species with poor understanding of decline reasons for 207 species.

  • Skerrat et al. (2007) introduced pathogenic challenges through chytrid fungus, leading to lethal skin diseases.

Interactions Between Ecological Factors

• Combined effects of environmental changes impacting amphibian resilience:

  • Pollutants (fertilizers, pesticides) lead to eutrophication that increases snail hosts, thereby perpetuating Ribeiroia infections.

  • Climate change effects such as increased exposure to UV light affecting frog immunity.

Levels of Biological Organization

• Ecosystems and Organisms:

  • Levels include:

    • Individual: Single organism.

    • Population: All individuals of a species in a specific area.

    • Community: Interactions among different species in an area.

    • Ecosystem: Community + physical environment.

    • Landscape: Multiple interconnected ecosystems.

    • Biosphere: Global sum of all ecosystems.

Evolution and Natural Selection

• Adaptation: A characteristic that enhances survival or reproduction.

  • Natural Selection: Mechanism by which organisms with favorable traits exhibit higher survival and reproductive rates, leading to evolutionary changes.

  • Example: Antibiotic resistance in bacteria as adaptation influenced by selective pressures.

Energy and Nutrient Cycling in Ecosystems

• Energy Movements: Energy flows through ecosystems unidirectionally, unable to be recycled.

• Nutrient Cycling: Nutrients are continuously cycled between organisms and their physical environment, supporting ecosystem sustainability.

  • Producers: Capture solar energy and convert it into food; critical for ecological support.

  • Consumers: Feed on other organisms, assimilating energy and nutrients.

  • Decomposers: Breakdown organic material, returning nutrients back to the physical environment to maintain the nutrient cycle.