Stage 5 Science: Living World Yearly Exam Revision

Comprehensive practice flashcards covering Stage 5 NSW Living World Biology, including body systems, nervous and endocrine coordination, disease and immunity, DNA genetics, biotechnology, evolution, and ecology.

What are the complementary roles of the digestive and circulatory systems in supporting cellular respiration?

The digestive system breaks down food and absorbs nutrients such as glucose into the bloodstream, while the circulatory system transports glucose and oxygen to body cells to release usable energy.

What structures comprise the central nervous system (CNS), and what is the function of the peripheral nervous system (PNS)?

The CNS comprises the brain and spinal cord, which process information and coordinate responses; the PNS consists of nerves connecting the CNS to limbs, organs, receptors, and effectors.

In nervous coordination, what is the sequence of impulse flow from the initial stimulus to the final response?

Stimulus $\rightarrow$ Receptors/sensory organs $\rightarrow$ Sensory neurones $\rightarrow$ Relay neurones (in the central nervous system) $\rightarrow$ Motor neurones $\rightarrow$ Effectors (muscles or glands) $\rightarrow$ Response.

What is the direction of signal transmission through a typical neuron?

Signals travel from the dendrites, through the cell body, along the axon, and to the axon terminals.

How is a nerve impulse transmitted chemically across a synapse?

When an electrical impulse reaches an axon terminal, vesicles open and release neurotransmitters into the synaptic cleft; these molecules diffuse across the gap and bind to receptor sites on the dendrites of the receiving neuron.

Which four anatomical lobes of the cerebral cortex are shown in this lateral view?

The frontal lobe, parietal lobe, occipital lobe, and temporal lobe.

Why does a spinal reflex action occur before a person is consciously aware of pain?

The sensory neuron conducts an impulse directly to an interneuron in the spinal cord, which immediately stimulates a motor neuron to contract an effector muscle before the signal is processed by the brain.

How do the nervous system and endocrine system differ in signal type, speed, and duration of effect?

The nervous system uses electrical impulses and neurotransmitters for rapid, brief effects targeting specific cells, whereas the endocrine system uses blood-borne hormones for slower, longer-lasting effects on target cells with matching receptors.

How do insulin and glucagon regulate blood glucose levels after eating and during fasting?

After eating, rising blood glucose stimulates pancreatic beta cells to release insulin, promoting cellular uptake and glycogen storage in the liver; when blood glucose falls, pancreatic alpha cells release glucagon, which stimulates the liver to break down glycogen into glucose.

How does negative feedback control thyroxine concentration in the bloodstream?

The hypothalamus and pituitary release thyroid-stimulating hormone (TSH) to stimulate thyroxine production; elevated thyroxine levels inhibit the release of TSH, reducing further thyroxine synthesis.

How does antidiuretic hormone (ADH) restore water balance in response to dehydration?

High solute concentration stimulates osmoreceptors in the hypothalamus to signal the posterior pituitary to release more ADH, causing the kidneys to reabsorb more water and produce a lower volume of concentrated urine.

What is phototropism in plants, and what is its adaptive advantage?

Phototropism is directional growth in response to light; growing shoots toward light maximizes light absorption for photosynthesis.

What are the four major pathogen groups that cause infectious diseases?

Bacteria (single-celled organisms, some producing toxins), Viruses (genetic material in a protein coat that replicates inside host cells), Fungi (eukaryotes including yeasts and moulds), and Protozoa (single-celled eukaryotes).

Which major morphological shapes of bacteria are shown in this diagram?

Coccus (spherical), Rod (bacillus), Spirillum, Spirochete, Budding and appendaged bacteria (with stalk or hypha), and Filamentous.

What are the three lines of defence against disease in the human body?

First line: non-specific physical and chemical barriers (skin, mucus, cilia, tears, stomach acid); Second line: non-specific innate responses (inflammation, blood clotting, fever, phagocytosis); Third line: specific adaptive responses (B lymphocytes producing antibodies, T lymphocytes, memory cells).

How does active immunity differ from passive immunity?

Active immunity involves the host's own immune system producing specific antibodies and long-lasting memory cells (via infection or vaccination); passive immunity involves receiving preformed antibodies (via placenta, breast milk, or transfer) providing only temporary protection without memory cells.

Why are antibiotics ineffective against viral diseases such as influenza?

Antibiotics inhibit cellular metabolic processes and cellular structures unique to bacteria; viruses lack their own cellular structures and replicate using the host's internal cell machinery.

What three chemical units make up every DNA nucleotide?

A phosphate group ($\text{PO}_4$), a five-carbon deoxyribose sugar, and one nitrogenous base (Adenine, Thymine, Cytosine, or Guanine).

What is the complementary base pairing rule in DNA, and what bonds hold the bases together?

Adenine (A) pairs specifically with Thymine (T), and Cytosine (C) pairs specifically with Guanine (G); they are held together across the two antiparallel strands by hydrogen bonds.

How do mitosis and meiosis differ in terms of nuclear divisions, chromosome numbers produced, and function?

Mitosis involves one division yielding two identical diploid daughter cells ($46$ chromosomes in humans) for growth and repair; meiosis involves two divisions yielding four genetically unique haploid gametes ($23$ chromosomes) for sexual reproduction.

What are the primary roles of transcription and translation during protein synthesis?

Transcription uses a DNA gene template to synthesize an RNA transcript; translation at the ribosome uses mRNA codons to assemble amino acids into a polypeptide chain.

What five types of chromosomal mutations are illustrated in this diagram?

Inversion, Deletion, Duplication, Insertion, and Translocation.

What is the critical distinction between somatic mutations and germline mutations?

Somatic mutations occur in body cells and only affect the individual, whereas germline mutations occur in gametes and can be inherited by subsequent generations.

What phenotypic and genotypic ratios result from crossing two heterozygous purple-flowered pea plants ($Pp \times Pp$)?

Genotypic ratio: $1\,PP : 2\,Pp : 1\,pp$; Phenotypic ratio: $3$ purple : $1$ white ($75\%$ purple, $25\%$ white).

Why are X-linked recessive disorders more frequently expressed in males than in females?

Males have only one X chromosome ($XY$), so a single recessive allele on the X chromosome is directly expressed because there is no homologous gene locus on the Y chromosome.

How are bacterial plasmids and restriction enzymes used to produce recombinant human insulin?

Restriction enzymes cut open the bacterial plasmid vector and isolate the human insulin gene; DNA ligase joins them together into a recombinant plasmid, which transforms $Escherichia\ coli$ bacteria that multiply and synthesize insulin.

In somatic cell nuclear transfer (SCNT) cloning, which donor provides the offspring's nuclear genome?

The nuclear genome comes entirely from the donor of the somatic body cell nucleus, which is inserted into an enucleated egg cell.

What is the role of guide RNA and the Cas9 enzyme in the CRISPR/Cas9 system?

The guide RNA directs the system to a specific target DNA sequence, and the Cas9 nuclease enzyme cleaves the double helix at that precise site to enable gene insertion, deletion, or correction.

What are the five essential steps of natural selection leading to population evolution?

1. Heritable variation exists in the population; 2. Overproduction of offspring leads to competition for limited resources; 3. Selection pressures affect individuals differently; 4. Individuals with advantageous traits experience differential reproductive success; 5. Survivors pass traits to offspring, increasing favorable allele frequencies over generations.

How does antibiotic resistance evolve in a bacterial population under natural selection?

Pre-existing resistant mutant bacteria survive antibiotic treatment while susceptible bacteria die; the surviving resistant bacteria reproduce, shifting the population to become predominantly resistant over generations.

Which shared pentadactyl forelimb structures in these vertebrate limbs demonstrate common ancestry?

Upper arm (humerus), forearm (radius + ulna), wrist (carpal), and hand/foot (metacarpals + phalanges).

What sequence of events leads to allopatric speciation?

A physical geographical barrier isolates populations, preventing gene flow; differing selective pressures, mutations, and genetic drift cause gradual divergence until reproductive isolation prevents successful interbreeding.

How does relative dating of fossils differ from radiometric dating?

Relative dating uses sedimentary stratigraphy to determine whether a fossil is older or younger than surrounding layers (lower layers are older); radiometric dating measures the decay of radioactive isotopes to determine an approximate numerical age in years.

Why does energy follow a one-way path through an ecosystem while matter cycles?

Energy enters as light and flows trophic levels with loss as metabolic heat at each transfer, meaning it cannot be reused; matter (such as carbon and nitrogen) is conserved and continuously recycled through biological, geological, and chemical processes.