Free QCE Biology Flashcard Review

SDI = 1 - Σ(n/N)². Used to quantify species diversity in a community by accounting for both species richness and evenness. Values range 0–1: higher values = greater diversity. Accounts for relative proportions of species, not just abundance counts.

Total (N) = 20. n/N for rabbits = 0.2, deer = 0.3, foxes = 0.5. (n/N)² = 0.04 + 0.09 + 0.25 = 0.38. SDI = 1 − 0.38 = 0.62. Moderate diversity—dominated by foxes but rabbit and deer presence increases diversity.

Richness = total number of different species in a community. Evenness = how equally individuals are distributed among species. A community with 5 species can have high richness; if one species dominates (low evenness), total diversity is lower than if all five have equal abundance.

Percentage of ground area covered by a species (e.g., 40% grass, 25% clover, 35% bare soil in a quadrat). Combines abundance with plant size; useful for sessile organisms. Not the same as species count—one large shrub = high cover; 100 seedlings = low cover.

Kingdom → Phylum → Class → Order → Family → Genus → Species → Subspecies (or form). Mnemonic: 'Keep Pulling Clams Or Forget Getting Sick Stomach.' Each rank is subordinate; species is the fundamental unit of classification.

(1) Two Latin names: genus (capitalized) + specific epithet (lowercase). (2) Italicized or underlined. (3) Genus may be abbreviated after first use (e.g., E. coli). (4) Species name is never used alone; genus + species required. (5) Reflects evolutionary relationships. Example: Homo sapiens.

r-selection: high fecundity, many offspring, minimal parental care, early maturity, short lifespan (rabbits, weeds). K-selection: low fecundity, fewer offspring, high parental investment, late maturity, long lifespan (elephants, humans). K-selected suit stable environments; r-selected suit unpredictable ones.

(1) Large body size. (2) Long generation time and lifespan. (3) Late sexual maturity. (4) Few offspring with high parental care. (5) Stable population near carrying capacity. Examples: primates, large predators, oak trees.

(1) Small body size. (2) Short generation time and lifespan. (3) Early sexual maturity. (4) Many offspring, minimal parental care. (5) Rapid population growth when resources available. Examples: insects, rodents, fast-growing plants.

Trace from tips back to most recent common ancestor. Species that diverge at same node share more recent common ancestor than those diverging earlier. Distance from node to tip (not horizontal position) indicates time. Grouping based on shared derived characters, not overall similarity.

A shared common ancestor and monophyletic relationship. Species that share a more recent node are more closely related. Example: if birds and reptiles branch from same node before mammals branch, birds and reptiles share more recent ancestor than either shares with mammals.

Approximately 10% of energy is transferred from one trophic level to the next; 90% is lost through respiration, heat, waste, and decomposition. Example: if producers capture 10,000 kJ, primary consumers obtain ~1,000 kJ, secondary consumers ~100 kJ, tertiary ~10 kJ.

Energy lost through: (1) Respiration (metabolic heat). (2) Movement and maintenance. (3) Heat loss to environment. (4) Incomplete feeding (uneaten parts). (5) Decomposition of dead organic matter. (6) Faeces and excretion. Only small fraction converted to new biomass.

Photosynthesis removes CO₂ from atmosphere and incorporates carbon into organic compounds (glucose, cellulose). Plants fix inorganic carbon into biomass. This is the main pathway for carbon to enter terrestrial and aquatic food webs, sequestering carbon from atmosphere.

Aerobic respiration by plants, animals, and decomposers breaks down organic compounds and releases CO₂ back to atmosphere: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O. Returns carbon to atmosphere; counterbalances photosynthetic removal. Occurs continuously in all living organisms.

Nitrogen fixation: conversion of atmospheric N₂ to ammonia (NH₃) and nitrate (NO₃⁻) available to plants. Agents: bacteria (Rhizobium in legume nodules, Azotobacter in soil), archaea, and some cyanobacteria. Essential because most organisms cannot use atmospheric N₂.

Nitrification: oxidation of ammonia (NH₃) to nitrite (NO₂⁻) then nitrate (NO₃⁻) in soil. Performed by nitrifying bacteria (Nitrosomonas, Nitrobacter). Makes nitrogen available to plants. Part of nitrogen cycle; aerobic process.

Denitrification: reduction of nitrate (NO₃⁻) to nitrogen gas (N₂) released to atmosphere. Performed by denitrifying bacteria (e.g., Pseudomonas) under anaerobic conditions in waterlogged soils. Closes nitrogen cycle; can reduce soil nitrogen availability.

Ammonification: decomposition of organic nitrogen (proteins, nucleic acids) in dead organisms and faeces to ammonia (NH₃). Performed by decomposer bacteria and fungi. Makes nitrogen available for nitrification. Key step in returning nitrogen from biomass to soil.

The functional role and position of a species within an ecosystem, including: (1) Habitat occupied. (2) Food/resources consumed. (3) Time of activity. (4) Physical conditions tolerated. (5) Interactions with other species. Each species has unique niche; no two species occupy identical niche indefinitely (competitive exclusion).