Comprehensive IGCSE Biology Flashcards

A full set of question-and-answer flashcards covering key topics from Biology Units 1, 10, 11, 12, and 13.

How is movement defined as a characteristic of living organisms?

Movement is defined as an action by an organism or part of an organism causing a change of position or place.

What is the definition of respiration in living organisms?

Respiration is defined as the chemical reactions in cells that break down nutrient molecules and release energy for metabolism.

How is sensitivity defined as a characteristic of living organisms?

Sensitivity is defined as the ability to detect or sense stimuli in the internal or external environment and respond to changes in the environment.

What is the definition of growth in living organisms?

Growth is defined as a permanent increase in size and dry mass by an increase in cell number or cell size or both.

What is the definition of a species?

A species is defined as a group of organisms that can reproduce to produce fertile offspring.

Which two parts of the taxonomic hierarchy form the scientific name of an organism in the binomial system?

The scientific name is made up of the genus and species.

Which cellular features are present in the cells of all living organisms?

All living cells contain cytoplasm, cell membrane, DNA as genetic material, ribosomes for protein synthesis, and enzymes involved in respiration.

What are the main features used to place organisms in Kingdom Plantae?

Organisms in Kingdom Plantae are multicellular, autotrophic feeders (have chlorophyll), have cell walls made of cellulose, and possess a complex eukaryotic cell structure with a nucleus.

What are the main features used to place organisms in Kingdom Fungi?

Organisms in Kingdom Fungi are multicellular, have cell walls made of chitin, are saprophytic feeders (cause decomposition), and have eukaryotic cells.

What are the key features of fish among the vertebrate groups?

Fish have loose, wet scales on their skin, use gills to breathe, lay eggs without shells in water, and are exothermic.

What body features distinguish insects from other groups of arthropods?

Insects have $3$ body segments (head, thorax, and abdomen), $3$ pairs of jointed legs, $2$ pairs of wings ($1$ or more might be small and underdeveloped), and $1$ pair of antennae.

How do monocotyledons and dicotyledons differ in terms of cotyledons, leaf veins, petals, and root structure?

Monocotyledons have a single cotyledon, leaves with parallel veins, petals in multiples of $3$, and fibrous roots. Dicotyledons have $2$ embryonic leaves (cotyledons), leaves with branching veins, petals in multiples of $4$ or $5$, and taproots.

What structural features are found in all viruses?

All viruses have a protein coat and genetic material (whether DNA and/or RNA).

What is a pathogen?

A pathogen is a disease-causing organism.

What is a transmissible disease?

A transmissible disease is a disease in which the pathogen can be passed from one host to another.

What mechanical and chemical barriers protect the human body against pathogens?

Mechanical barriers include skin and hairs in the nose. Chemical barriers include mucus and stomach acid ($HCl_{(aq)}$).

How do antibodies defend the body against pathogens?

Antibodies lock on to antigens leading to direct destruction of pathogens, or marking of pathogens for destruction by phagocytes.

What is active immunity and how is it gained?

Active immunity is defence against a pathogen by antibody production in the body. It is gained after an infection by a pathogen or by vaccination.

What are the steps involved in the process of vaccination?

An altered or harmless form of a pathogen (containing antigens) is introduced into the body, triggering an immune response by lymphocytes to produce complementary antibodies and memory cells that provide long-term immunity.

What is passive immunity and why is it important for infants?

Passive immunity is short-term defence against a pathogen by antibodies acquired from another individual (memory cells are not produced). It is important for infants because they cannot produce their own antibodies and rely on antibodies from maternal breast milk.

What characterises Type 1 diabetes as an autoimmune disease?

Type 1 diabetes is a chronic condition where the immune system targets and destroys native insulin-producing body cells, resulting in limited pancreas production of insulin.

How does the bacterium Cholera cause diarrhoea and dehydration?

Cholera produces toxins that initiate secretion of $Cl^-$ into the small intestine, causing osmotic movement of water into the gastrointestinal tract.

What are the four common features of all gas exchange surfaces in humans?

All gas exchange surfaces in humans feature a large surface area, a thin surface, a good blood supply, and good ventilation with air.

What are the percentages of Oxygen ($O_2$) and Carbon dioxide ($CO_2$) in inspired versus expired air?

Inspired air contains $21\%$ Oxygen and $0.04\%$ Carbon dioxide. Expired air contains $16\%$ Oxygen and $4\%$ Carbon dioxide.

What is the function of the cartilage rings in the trachea?

Rings of cartilage support the airways, keep them open during breathing, and prevent inward collapse of the trachea.

How do goblet cells and ciliated cells protect the gas exchange system?

Goblet cells secrete a gelatinous mucosal layer to trap pathogens and particles, while ciliated cells have tiny hairs that push mucus up passages towards the nose and throat for removal.

How does physical activity lead to an increased rate and depth of breathing?

Physical activity increases carbon dioxide production, raising blood $[CO_2]$. This stimulates receptor cells in the brain to send impulses to lung muscles to contract faster and more strongly.

What are the main uses of energy released by respiration in the human body?

Energy is used for muscle contraction, protein synthesis, cell division, active transport, growth, the passage of nerve impulses, and the maintenance of a constant body temperature.

What is the word equation and balanced chemical equation for aerobic respiration?

Word equation: glucose + oxygen \rightarrow carbon dioxide + water. Balanced chemical equation: $C_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O$.

Which enzyme acts as a regulator in glycolysis to break down glucose into pyruvate?

Phosphofructokinase (PFK) acts as a regulator to break down glucose into pyruvate ($C_6H_{12}O_6 \rightarrow CH_3COCOO^-$).

What are the word equations for anaerobic respiration in human muscles during exercise and in yeast?

In muscles during exercise: glucose \rightarrow lactic acid. In yeast: glucose \rightarrow alcohol + carbon dioxide.

What is the balanced chemical equation for anaerobic respiration in yeast?

The balanced chemical equation is $C_6H_{12}O_6 \rightarrow 2C_2H_5OH + 2CO_2$.

How is an oxygen debt removed from the body during recovery after exercise?

A fast heart rate transports lactic acid in blood from muscles to the liver, where continued deep and fast breathing provides oxygen for the aerobic respiration of lactic acid into carbon dioxide and water.

Which waste products are excreted by the lungs and the kidneys?

The lungs excrete carbon dioxide, and the kidneys excrete urea, excess water, and excess ions.

What is deamination and where does it take place?

Deamination is the removal of the nitrogen-containing part of amino acids to form urea (converting excess amino acids to ammonia, then urea), which occurs in liver cells.

What role does the glomerulus play in renal excretion?

The glomerulus filters water, glucose, urea, and ions from the blood under high pressure during ultrafiltration.

Percentage-wise, how much of all recovered nutrients is reabsorbed in the proximal convoluted tubule (PCT)?

The proximal convoluted tubule reabsorbs $60\%$ of all recovered nutrients.

What are the specific reabsorption functions of the descending and ascending limbs of the Loop of Henle?

The descending limb reabsorbs water by osmosis, while the ascending limb reabsorbs ions by active transport.