NCEA Level 2 Biology flashcards

31 cards. Read the term and the definition here. The deck at the top of this page is optional.

Hypothesis in practical investigation

A testable prediction linking an independent variable to a measurable dependent variable, stated before data collection and phrased so that evidence could support or refute it.

Independent variable

The factor deliberately changed or selected by the investigator, such as light intensity or temperature, so that its effect on the measured dependent variable can be observed.

Dependent variable

The variable that is measured or counted as the outcome of the investigation, for example the number of leaves, rate of bubble production, or population count.

Controlled variables

Factors kept constant across trials, such as volume of solution, species, age and time of day, so that observed differences can be attributed to the independent variable alone.

Reliability of data

Consistency of results when a measurement is repeated; improved by replication, repeated sampling and averaging, and indicated by small spread or low variability among repeats.

Validity of an investigation

Whether the method measures what it claims to measure and whether the conclusion follows from the data, requiring control of confounding variables and appropriate measurement technique.

Aseptic technique

Procedures that prevent contamination by unwanted microorganisms, including sterilising equipment, flaming loops, working near a flame, and sealing plates before incubation.

Quadrats and transects

Sampling tools for sessile organisms: quadrats estimate density or cover in randomly placed squares, while line or belt transects record species along a gradient such as a shore.

Mark-recapture estimate

Population size estimated as (number marked in first sample × total in second sample) ÷ number of marked individuals recaptured, assuming marked animals mix and are not affected.

Credibility of a source

Judgement of how trustworthy biological information is, based on author qualifications, peer review, publication date, supporting evidence, and whether other sources agree.

Zonation pattern

A pattern where different species occupy distinct bands along an environmental gradient such as tidal height, explained by differing tolerance to abiotic factors and by competition.

Selection pressure

An environmental factor, such as predation, temperature or food supply, that favours individuals with certain inherited variations, increasing their survival and reproduction.

Structural adaptation example

An inherited physical feature that improves survival in a habitat, such as the waxy cuticle and sunken stomata of plants adapted to dry, windy environments.

Biological issue evaluation

Weighing biological evidence and the perspectives of different groups to reach a justified position on an issue such as vaccination, pest control or biodiversity loss.

Photosynthesis summary

The process in chloroplasts where light energy drives conversion of carbon dioxide and water into glucose and oxygen, storing energy in chemical bonds for use by the organism.

Light reactions location

The stage of photosynthesis occurring on the thylakoid membranes, where light energy is captured and used to produce ATP and reduce NADP for the Calvin cycle.

Calvin cycle

The light-independent stage of photosynthesis in the stroma, where carbon dioxide is fixed and reduced using ATP and NADPH to build glucose and other carbohydrates.

Aerobic respiration site

Glucose breakdown with oxygen, beginning with glycolysis in the cytoplasm and continuing in the mitochondria, releasing carbon dioxide, water and usable energy as ATP.

Anaerobic respiration products

Without oxygen, animal cells convert glucose to lactate, while yeast produces ethanol and carbon dioxide; both release far less ATP per glucose than aerobic respiration.

Enzyme and temperature

Enzyme activity rises with temperature to an optimum, then falls sharply as heat denatures the enzyme by changing the shape of its active site so substrate no longer fits.

Meiosis and variation

Reduction division producing four genetically different haploid gametes; crossing over in prophase I and independent assortment in metaphase I shuffle alleles to generate variation.

Crossing over

Exchange of segments between homologous chromosomes during prophase I of meiosis, producing new combinations of alleles on a chromosome and increasing genetic variation in gametes.

Independent assortment

Random orientation of homologous pairs at metaphase I, so maternal and paternal chromosomes are distributed independently into gametes, creating many allele combinations.

Monohybrid 3:1 ratio

The expected phenotype ratio when two heterozygous individuals are crossed for one gene with complete dominance; the corresponding genotype ratio is 1 homozygous dominant : 2 heterozygous : 1 homozygous recessive.

Test cross purpose

Crossing an individual showing the dominant phenotype with a homozygous recessive individual to determine whether the unknown genotype is homozygous dominant or heterozygous, based on offspring ratios.

Dihybrid 9:3:3:1 ratio

Expected phenotype ratio from crossing two individuals heterozygous for two unlinked genes; deviation from this ratio may indicate linkage or a lethal genotype combination.

Mutation and phenotype

A change in the DNA base sequence that alters the mRNA codon, potentially changing the amino acid sequence and protein shape, which may change the expressed phenotype.

Transcription

The process in the nucleus where a DNA strand acts as a template for RNA polymerase to build messenger RNA carrying the base sequence to the ribosome.

Translation

The process at ribosomes where messenger RNA codons are matched to transfer RNA anticodons, joining amino acids into a polypeptide with a specific sequence and shape.

Genotype versus phenotype

Genotype is the combination of alleles an organism carries; phenotype is the observable characteristic, produced by the genotype interacting with environmental factors during development.

Pedigree analysis rule

In a pedigree, two unaffected parents producing an affected offspring indicates the trait is recessive; the affected individual must be homozygous recessive and parents are carriers.