HSC Biology flashcards

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

Cell theory

All living organisms are made of cells, the cell is the basic structural and functional unit of life, and all cells arise from pre-existing cells.

Fluid mosaic model

Describes the cell membrane as a phospholipid bilayer with proteins and other molecules moving laterally within it, giving a fluid, mosaic-like structure.

Osmosis

The net movement of water across a semipermeable membrane from a region of lower solute concentration to a region of higher solute concentration.

Active transport

Movement of substances across a membrane against a concentration gradient using energy from ATP and carrier proteins.

Enzyme specificity

Each enzyme has an active site shaped to fit only particular substrate molecules, so it catalyses only specific reactions.

Levels of organisation

The hierarchy from smallest to largest is organelle, cell, tissue, organ, organ system and organism.

Xylem function

Transports water and dissolved minerals from roots to leaves through dead, lignified vessels, driven mainly by transpiration pull.

Phloem function

Transports sugars and other organic compounds from photosynthetic sources to sinks such as roots and growing tissues.

Alveoli

Tiny air sacs in the lungs with thin walls and large total surface area where gas exchange between air and blood occurs.

Species definition

A group of organisms that can interbreed in nature to produce fertile offspring, sharing common characteristics.

Binomial nomenclature

A two-part naming system using genus and species names, with the genus capitalised and both words italicised.

Natural selection

Process where individuals with heritable traits suited to their environment survive and reproduce more, increasing those traits in later generations.

Adaptation types

Structural adaptations involve body form, physiological adaptations involve internal processes, and behavioural adaptations involve actions taken by organisms.

Abiotic factors

Non-living components of an ecosystem such as light, temperature, water, soil and salinity that influence organism distribution and abundance.

Trophic level

A feeding position in a food chain, starting with producers and followed by primary, secondary and tertiary consumers.

Keystone species

A species whose removal causes disproportionate change to community structure relative to its abundance.

Ecological succession

The gradual change in species composition of a community over time, beginning with pioneer species and progressing toward a stable climax community.

Nitrogen fixation

Conversion of atmospheric nitrogen gas into ammonia by bacteria such as Rhizobium, making nitrogen available to plants.

DNA base pairing

Adenine pairs with thymine using two hydrogen bonds, and guanine pairs with cytosine using three hydrogen bonds.

Transcription

The process in the nucleus where RNA polymerase builds an mRNA molecule using one strand of DNA as a template.

Translation

The process at ribosomes where mRNA codons are matched with tRNA anticodons to assemble amino acids into a polypeptide chain.

Incomplete dominance

A pattern where heterozygotes show an intermediate phenotype between the two homozygotes, such as pink flowers from red and white parents.

Sex-linked inheritance

Inheritance of genes located on sex chromosomes; X-linked recessive traits appear more often in males because they have only one X chromosome.

Frameshift mutation

Insertion or deletion of nucleotides not in multiples of three, shifting the reading frame and altering all subsequent codons.

Mutagen

An agent such as UV radiation, ionising radiation or certain chemicals that increases the rate of mutation in DNA.

Crossing over

Exchange of genetic material between homologous chromosomes during prophase I of meiosis, producing new allele combinations in gametes.

Transgenic organism

An organism containing genetic material from another species, introduced using vectors such as plasmids.

First line of defence

Physical and chemical barriers such as intact skin, mucus, cilia and stomach acid that prevent pathogens from entering the body.

Adaptive immunity

The specific third line of defence where B cells produce antibodies and T cells destroy infected cells, creating immunological memory.

Vaccination

Introduction of antigens from a pathogen to stimulate an immune response and produce memory cells without causing disease.

Antibiotic resistance

Bacteria surviving antibiotic treatment reproduce and pass on resistance genes, making infections harder to treat over time.

Multifactorial disease

A disorder caused by combined genetic and environmental influences, such as type 2 diabetes or cardiovascular disease.