Web of Life

Amphibians

  • “Biological indicators” of environmental problems

  • Skin is permeable; pollutant molecules can pass through easily

  • Eggs have no protective shell

  • Spend part of their life on land and part in water

    • exposed to pollutants and UV in both environments

  • Remain close to birthplace - local conditions


Experiments

  • Controlled Experiment: Experimental groups are compared with a control group that lacks the factor being tested

  • Laboratory Experiments

    • Pros: limit/exclude variables not being tested (confounding factors)

    • Cons: artificial conditions (will the results hold true under “natural” conditions?)


Experimental Design:

  • Control: the group that is not treated

  • Replicate: perform each treatment once

  • Assign treatments at random

  • Statistical analysis: provides standardized way of assessing significance


Key Concepts

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

  • Approaches:

    • Descriptive science

    • Hypothesis-based science

  • Events in the natural world are interconnected

  • Even species that don’t interact directly can be connected by shared environmental features

  • Ecologists ask questions about the natural world in order to understand these connections

  • Ecology: the scientific study of how organisms affect and are affected by other organisms and their environment


Early Ecological Views

  • There is a “balance of nature” in which natural systems are stable and tend to return to an original state after disturbance

  • Each species has a distinct role to play in maintaining that balance


Change

  • Natural systems are dynamic and prone to change

  • They do not necessarily return to their original state after a disturbance