Unit 3 & Unit 2 Biology Review: Ecosystem Dynamics & Species Interactions

Comprehensive vocabulary flashcard deck covering Unit 3 and Unit 2 Senior Biology lecture notes on ecological classification, population dynamics, energy transfer, biotic interactions, and ecological succession.

Biological Species Concept

A biological definition of a species as a group of organisms capable of interbreeding naturally to produce fertile, viable offspring, and which are reproductively isolated from other such groups.

Limits of the Biological Species Concept

Three main limitations: it cannot be applied to asexual organisms, it is not useful for extinct species or fossils, and it is impractical for geographically isolated populations.

Linnaean Classification System

A hierarchical system used to organize organisms based on shared fundamental characteristics and relatedness rather than physical appearance, progressing from domain/kingdom down to species.

Binomial Nomenclature

A two-part scientific naming convention derived from Linnaean classification, consisting of a capitalized genus name followed by a lowercase species name.

Lincoln Index

A quantitative method used to estimate population size in the wild using a mark-recapture sampling procedure.

Lincoln Index Formula

The mathematical formula $\text{N} = \frac{n_1 \times n_2}{n_{12}}$, where $\text{N}$ is total population estimate, $n_1$ is initial marked sample, $n_2$ is second captured sample, and $n_{12}$ is marked individuals recaptured.

Assumptions of the Lincoln Index

Three core assumptions: marks are not lost or removed, the population is closed (no births, deaths, immigration, or emigration), and every individual has an equal chance of being recaptured.

Species Abundance

The total number of individual organisms belonging to a specific species within a given area.

Species Richness

The total number of different species present in a specific ecosystem or defined geographical area.

Simpson's Diversity Index

A measure of biodiversity accounting for both species richness and species abundance, calculating the probability that two randomly selected individuals belong to the same species.

Specht's Classification System

A classification system used to categorize vegetation structural types based on the dominant plant type, plant height, and percentage of foliage cover.

Holdridge Life Zone System

A system that classifies ecosystems based on bioclimatic factors, including mean annual temperature, annual precipitation, humidity, and potential evapotranspiration ratio.

Potential Evapotranspiration

The total combined loss of water transferred to the atmosphere through soil/surface evaporation and plant transpiration.

J-Curve Population Growth

Exponential, unrestricted population growth occurring when an organism experiences ideal conditions with unlimited resources.

S-Curve Population Growth

Logistic population growth that accelerates initially but slows down and levels off at environmental carrying capacity due to limiting factors.

Carrying Capacity

The maximum population size of a species that a specific environment can sustainably support indefinitely without degrading the habitat.

r-Strategists

Species characterized by high exponential growth rates, short lifespans, quick maturation, production of numerous small offspring, and fluctuating population sizes (e.g., bacteria, insects, rats).

K-Strategists

Species characterized by slow growth rates, long lifespans, late maturity, production of few large offspring, and stable populations close to carrying capacity (e.g., humans, elephants, kangaroos).

Phototroph

An organism that utilizes sunlight energy to fuel its metabolic synthesis.

Chemotroph

An organism that derives its energy from the oxidation of chemical compounds.

Autotroph

An organism that synthesizes organic nutrients from inorganic molecules such as carbon dioxide ($CO_2$).

Heterotroph

An organism that must consume organic molecules produced by other organisms to obtain energy.

Biomass

The total mass of organic material and stored chemical energy present at a given trophic level in an ecosystem.

Trophic Level

A distinct step or position occupied by an organism within an ecological food chain or biomass pyramid.

Trophic Efficiency

The percentage of net energy passed from one trophic level to the next, calculated by dividing current trophic level net productivity by previous level net productivity.

Inverted Biomass Pyramid

A biomass pyramid common in aquatic ecosystems where producer biomass (phytoplankton) is smaller than consumer biomass (zooplankton) due to rapid reproduction and consumption rates.

Energy Loss Mechanisms in Ecosystems

Three physical pathways through which organisms lose energy besides respiration: radiation (heat dissipation), reflection (reflected light frequencies affecting coloration), and absorption (maintaining body temperature).

10% Rule in Trophic Transfer

The ecological principle that only approximately 10\times 10^{-1}\text{ (or }10\text{\top})—roughly $10\text{\%}$—of usable energy transfers to the next trophic level, limiting food chains to 4 or 5 levels.

Energy Flow Diagram

A schematic chart illustrating the directional transfer of energy from solar input through producers, consumers, and decomposers, tracking thermal energy loss at every stage.

Food Web

An interconnected system of multiple overlapping food chains reflecting the complex, multi-level feeding relationships within an ecosystem.

Photosynthesis

The biochemical process by which autotrophic producers convert solar light energy, water, and carbon dioxide into glucose and oxygen.

Photosynthesis Chemical Equation

The balanced biochemical equation for photosynthesis: $6CO_2 + 6H_2O \rightarrow C_6H_{12}O_6 + 6O_2$.

Cellular Respiration Chemical Equation

The balanced biochemical equation for cellular respiration: $C_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O + \text{ATP}$.

Nitrogen-Fixing Bacteria

Soil microorganisms that convert unreactive atmospheric nitrogen gas ($N_2$) into bioavailable compounds such as ammonia ($NH_3$).

Predation

An interspecific interaction ($+/-$) where one organism (predator) captures, kills, and feeds upon another organism (prey).

Competition

An ecological interaction ($-/-$) where individuals or species compete for identical limited resources, negatively impacting survival, growth, and reproduction of participants.

Interspecific Competition

Competition occurring between individuals belonging to different species competing for limited resources.

Intraspecific Competition

Competition occurring between individuals belonging to the same species competing for limited resources or mates.

Obligate Mutualism

A symbiotic mutualistic relationship ($+/+$) where both species rely entirely on one another for survival and cannot live independently (e.g., termites and gut microbes).

Facultative Mutualism

A mutualistic relationship ($+/\text{+})$ where both species gain survival advantages but can exist independently without relying on the interaction (e.g., clownfish and sea anemones).

Commensalism

A symbiotic interaction ($+/0$) in which one species derives benefits (such as shelter or transportation) while the host species remains unaffected.

Parasitism

A symbiotic interaction ($+/-$) where a parasite lives on or inside a host organism, deriving nutrients and harming the host without typically killing it immediately.

Ecological Niche

The functional role and spatial position that an organism occupies within an ecosystem, encompassing all its interactions with abiotic and biotic environmental factors.

Competitive Exclusion Principle

The ecological principle stating that two species competing for the exact same limited resources within an identical niche cannot stably coexist indefinitely.

Resource Partitioning

The evolutionary division of limited spatial or dietary resources into sub-niches, enabling competing species to coexist (e.g., shorebirds feeding at different water depths).

Keystone Species

A plant or animal playing a unique and crucial role in maintaining ecosystem structure and stability, whose removal leads to ecosystem collapse (e.g., Yellowstone wolves, southern cassowary).

Bioaccumulation

The progressive accumulation of non-degradable pollutants or toxins (such as mercury) within living tissues across successive levels of a food chain.

Primary Succession

Ecological succession initiating on entirely bare substrate lacking pre-existing soil (such as volcanic rock or sand dunes).

Secondary Succession

Ecological succession taking place in a previously inhabited ecosystem that was disturbed, but where intact soil already remains (such as repopulation after a light forest fire).

Pioneer Species

The initial organisms (e.g., lichens, mosses) to colonize bare or disturbed habitats, characterized by high dispersal ability, rapid growth, extreme stress tolerance, and soil-forming capability.