QCAA Senior Biology Units 3 & 4 Key Vocabulary

Vocabulary flashcards covering core concepts, mathematical formulas, and analytical skills for QCAA Senior Biology Units 3 and 4.

Genetic Diversity

Variation in genes/alleles within a population or species.

Species Diversity

The variety of species in an area, including their richness and relative abundance.

Ecosystem Diversity

The variety of ecosystems/habitats within a region.

Biological Species Concept

A concept defining a species as a group of actually or potentially interbreeding natural populations that are reproductively isolated from other such groups.

Linnaean System

A system used for classifying and naming organisms using hierarchical taxonomic groups: domain, kingdom, phylum, class, order, family, genus, species.

Binomial Nomenclature

A two-part scientific naming system using genus and species.

Dichotomous Key

An identification tool that uses a sequence of paired, contrasting choices to identify an organism.

Lincoln Index

A formula $N = \frac{M \times n}{m}$ used to estimate population size, where $M$ is the number marked initially, $n$ is the total caught in the second sample, and $m$ is marked individuals recaptured.

Species Richness

The number of different species present in an area or sample.

Species Evenness

How evenly individuals are distributed among the species present, often expressed using relative species abundance.

Percentage Cover

The proportion/percentage of an area covered by a particular species.

Percentage Frequency

The percentage of samples/quadrats in which a species occurs.

Simpson's Diversity Index

In the QCAA syllabus, a measure of species diversity calculated as $SDI = 1 - \frac{\sum n(n-1)}{N(N-1)}$, where $n$ is the number of individuals of a particular species and $N$ is the total number of individuals of all species.

Random Sampling

Selecting sample locations randomly so each location has an equal or known chance of selection.

Systematic Sampling

Taking samples at regular, predetermined intervals.

Stratified Sampling

Dividing an area into relevant strata and sampling within each stratum.

Quadrat

A sampling tool useful for relatively immobile organisms or organisms whose abundance can be measured within defined areas.

Line Transect

A line along which organisms or their occurrence are recorded to investigate distribution across an environmental gradient.

Belt Transect

A strip of area sampled along a transect, usually using adjoining quadrats.

Capture-Recapture

A method useful for estimating the population size of mobile organisms.

Biotic Factors

Living or biologically derived factors affecting organisms, such as food availability, competition, predation and disease.

Abiotic Factors

Non-living environmental factors such as space, shelter, water, nutrients and environmental conditions.

Microhabitat

A small, specific habitat within a larger habitat with its own local conditions.

Exponential Population Growth

Growth producing a J-shaped curve when resources allow rapid increase and limiting factors are minimal.

Logistic Population Growth

Growth that produces an S-shaped curve as limiting factors increase and population size approaches carrying capacity.

Carrying Capacity

The maximum population size that an ecosystem can sustainably support under particular conditions.

Density-Dependent Factor

A limiting factor whose effect changes with population density, such as competition, predation or disease.

Density-Independent Factor

A limiting factor whose effect is not dependent on population density, such as many climatic events.

r-Selected Species

Species generally associated with rapid reproduction, many offspring and relatively low investment per offspring.

K-Selected Species

Species generally associated with slower reproduction, fewer offspring and relatively greater investment per offspring.

Interspecific Competition

Competition between individuals of different species for shared resources.

Intraspecific Competition

Competition between individuals of the same species.

Competitive Exclusion

The principle that two species with sufficiently overlapping niches cannot indefinitely coexist in the same way when competing for the same limiting resource.

Energy Pyramid

A diagram showing the amount of energy available at successive trophic levels.

Ecological Pyramid of Biomass

A diagram comparing the biomass present at successive trophic levels.

Gross Productivity

The total rate at which producers capture/store energy as chemical energy.

Net Productivity

The energy remaining as new producer biomass after the energy used in respiration is accounted for.

Predation

An interaction in which one organism kills and consumes another.

Competition

An interaction in which organisms use the same limited resource, reducing resource availability to one another.

Mutualism

An interaction in which both interacting species benefit.

Commensalism

An interaction in which one species benefits while the other is not significantly affected.

Parasitism

An interaction in which a parasite benefits while the host is harmed.

Ecological Niche

The role and resource-use position of a species within its ecosystem, including how it interacts with biotic and abiotic conditions.

Keystone Species

A species that has a disproportionately large effect on community structure relative to its abundance or biomass.

Ecological Succession

A directional process involving changes in community composition and ecosystem characteristics over time.

Primary Succession

Succession beginning where there is little or no pre-existing soil or biological community.

Secondary Succession

Succession occurring after disturbance where soil and/or remnants of the previous community remain.

Pioneer Species

Early colonisers that establish in newly available or disturbed environments.

DNA Nucleotide

A molecule consisting of a nitrogenous base, a sugar and a phosphate group.

Gene

A segment of DNA containing information that can contribute to a functional product, such as a polypeptide or functional RNA.

Chromosome

A DNA molecule packaged with associated proteins that carries genetic information.

Introns

Non-coding intervening sequences removed from pre-mRNA during RNA splicing.

Exons

Sequences retained in mature RNA after RNA splicing.

Promoter Region

A DNA region where transcription machinery and regulatory proteins can bind to initiate/regulate transcription.

Homologous Chromosomes

A pair of chromosomes with the same genes at corresponding loci, one inherited from each parent; they may carry different alleles.

Sister Chromatids

The replicated copies of a chromosome joined at the centromere before separation.

Centromere

The chromosome region associated with joining sister chromatids and chromosome movement during cell division.

Telomeres

Protective chromosome-end regions.

Gene Locus

The specific position of a gene on a chromosome.

Allele

An alternative form of a gene at a particular locus.

Histones

Proteins that help package and organise DNA into chromatin.

Plasmids

Small, usually circular DNA molecules separate from the main chromosome, especially in prokaryotes.

Helicase

The enzyme that separates DNA strands during replication.

DNA Polymerase

The enzyme that synthesises a complementary DNA strand using an existing strand as a template.

Okazaki Fragments

Short DNA fragments produced on the lagging strand during DNA replication.

DNA Ligase

An enzyme that joins DNA fragments by forming bonds in the DNA backbone.

Point Mutation

A mutation affecting a single nucleotide/base pair.

Frameshift Mutation

A mutation caused by insertion or deletion of nucleotides that shifts the reading frame of a sequence.

Meiosis

A specialised cell division that produces haploid gametes and contributes to genetic variation.

Spermatogenesis

The process of producing sperm cells.

Oogenesis

The process of producing ova/egg cells.

Aneuploidy

An abnormal chromosome number involving gain or loss of individual chromosomes.

Ploidy

The number of complete sets of chromosomes in a cell.

Karyotype

An organised display of an individual's chromosomes, usually arranged in homologous pairs.

Transcription

The process of producing messenger RNA from a DNA gene template.

Translation

The process of using mRNA information to assemble an amino acid sequence at a ribosome.

Codon

A three-nucleotide sequence on mRNA specifying an amino acid or a stop signal.

Anticodon

A three-nucleotide sequence on tRNA complementary to an mRNA codon.

Heterochromatin

A relatively condensed form of chromatin generally associated with reduced gene transcription.

Euchromatin

A relatively less condensed form of chromatin generally more accessible for transcription.

Transcription Factors

Proteins that bind DNA regulatory regions, including promoter regions, to influence transcription.

HOX Genes

Genes in the HOX transcription-factor family that help regulate body morphology and developmental patterning.

Dominant Inheritance

Inheritance pattern where a phenotype is expressed when an individual has at least one copy of the relevant dominant allele.

Recessive Inheritance

Inheritance pattern where a recessive phenotype is expressed when the individual has the required recessive allele combination, typically two copies for an autosomal trait.

Autosomal Inheritance

Inheritance involving genes located on autosomes rather than sex chromosomes.

Sex-Linked Inheritance

Inheritance involving genes located on sex chromosomes.

Polygenic Inheritance

Inheritance pattern for a trait influenced by multiple genes, often producing continuous variation.

Multiple-Allele Inheritance

Inheritance pattern where a gene has more than two allelic forms in the population, although an individual still carries only the number of alleles allowed by its ploidy.

Recombinant DNA

DNA formed by joining DNA from different sources.

Restriction Enzymes

Enzymes that cut DNA at specific recognition sequences.

PCR (Polymerase Chain Reaction)

A technique used for amplifying a selected DNA sequence so there are many copies available for analysis.

Gel Electrophoresis

A technique used in DNA profiling for separating DNA fragments by size to produce a characteristic banding pattern.

Microevolution

Change in allele frequencies within a population across generations.

Macroevolution

Large-scale evolutionary change, including diversification above the population level, resulting from accumulated evolutionary changes over time.

Genetic Drift

Random change in allele frequencies due to chance, especially influential in small populations.

Bottleneck Effect

A form of genetic drift following a sharp reduction in population size, where survivors represent a random sample of the original population.

Founder Effect

A form of genetic drift that occurs when a new population is established by a small number of individuals.

Natural Selection

A mechanism of evolution in which individuals with heritable phenotypic traits that increase reproductive success contribute more offspring to subsequent generations, changing allele frequencies.

Allele Frequency Relationship

The mathematical equation $p + q = 1$ representing allele frequencies for two alleles in a population.

Stabilising Selection

Selection favouring intermediate phenotypes and selecting against extremes.