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Vocabulary flashcards covering key terms and concepts from the C4.1 Communities (SL) lecture, including ecological relationships, statistical tests, population controls, and chemical interactions.
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Community
All interacting populations (plants, animals, fungi, bacteria) living together in a given area.
Population
A group of individuals of the same species living in one area.
Habitat
The abiotic environment in which a community lives.
Ecosystem
A community plus its abiotic habitat and the interactions between them.
Ecological Niche
The role and position a species occupies, including its use of resources and relationships with other species.
Herbivory
A feeding relationship in which an organism consumes only plant matter.
Predation
An interaction where one organism (predator) hunts and feeds on another (prey).
Interspecific Competition
Competition between different species for limited resources.
Symbiosis
A close, long-term interaction between two different species.
Mutualism
A symbiotic relationship in which both species benefit.
Commensalism
A symbiotic relationship in which one species benefits and the other is unaffected.
Parasitism
A symbiotic relationship where one species benefits at the expense of another.
Pathogenicity
The ability of an infectious agent to cause disease in a host.
Root Nodule Mutualism
Association between legume roots (Fabaceae) and nitrogen-fixing Rhizobium bacteria, benefiting both partners.
Mycorrhizae
A filamentous network formed between fungi and orchid roots (Orchidaceae) that increases nutrient uptake for both.
Zooxanthellae
Photosynthetic algae living inside coral polyps, providing nutrients while receiving protection and CO₂.
Endemic Species
A species native to and restricted to a specific geographic region.
Alien Species
A species introduced to an area outside its natural range.
Invasive Species
An alien species that disrupts native ecosystems and harms endemic species.
Fundamental Niche
The full range of environmental conditions a species could occupy in the absence of competition.
Red Fox vs. Quoll
Example of resource competition where introduced red foxes outcompete Australia’s native quolls.
Laboratory Experiment (Competition)
Controlled test measuring species performance when isolated versus together.
Field Manipulation
Research method that removes one species in nature to observe impact on another.
Field Observation
Random sampling (e.g., quadrats) to record species presence or absence in situ.
Contingency Table
A matrix of observed frequencies used to organize presence/absence data for chi-squared tests.
Expected Frequency
Value calculated from row and column totals to predict distribution if no association exists.
Chi-Squared Test
Statistical test comparing observed and expected frequencies to assess species association.
Degrees of Freedom (df)
Value (for two-species association, df = 1) used to locate critical chi-squared values.
p Value
Probability that observed differences are due to chance; p < 0.05 denotes statistical significance.
Null Hypothesis
Statement that there is no association between two species; accepted unless data are significant.
Alternative Hypothesis
Statement that an association exists between two species; accepted when chi-squared is significant.
Top-Down Control
Population regulation by consumers at higher trophic levels affecting lower levels (trophic cascade).
Bottom-Up Control
Population regulation initiated by resource availability at lower trophic levels influencing higher levels.
Keystone Species
Species that exerts disproportionate top-down control, preventing resource monopolization by lower levels.
Secondary Metabolite
A chemical not essential for growth but produced to influence other organisms (e.g., allelopathic compounds).
Allelopathy
Release of chemicals by a plant or organism that affects growth or survival of other species.
Sinigrin
Allelopathic compound from garlic mustard that inhibits germination and root growth of neighboring plants.
Antibiotic
Chemical that inhibits or kills bacteria, often secreted by fungi or other organisms.
Penicillin
Antibiotic produced by Penicillium fungus that targets bacterial cell walls.