Grade 8 Science: Characteristics of Life, Cells, Immune System, and Disease

Vocabulary practice flashcards covering the key terms and concepts from Grade 8 Science: Characteristics of Living Things, Cell Theory and Organelles, Photosynthesis and Cellular Respiration, Microorganisms, the Immune System, and Disease Interventions.

Stimulus

Anything that causes a living thing to react or respond in a certain way.

External Stimuli

Changes that occur outside the body in the surroundings of a living thing, such as sound, light, or heat.

Internal Stimuli

Changes that occur inside the body of a living thing, such as feeling thirsty, hungry, or sleepy.

Cellular Respiration

A chemical reaction in the cells of most organisms that releases energy needed to carry out life processes: $\text{sugar} + \text{oxygen} \rightarrow \text{carbon dioxide} + \text{water} + \text{energy}$.

Consumers

Living organisms that obtain nutrients by consuming other organisms or food.

Producers

Living organisms that make their own food using the Sun's energy and nutrients from their surroundings.

Virus

A small infectious agent consisting of a strand of genetic material surrounded by a protein layer that replicates only inside the living cells of a host organism.

Mimivirus

A virus discovered between 1992 and 2008 containing more genetic material than other known viruses, including genetic material never before seen in viruses.

Megavirus

A virus discovered in 2011 with even more genetic material than Mimivirus, suggesting viruses may have evolved from a common ancestor capable of producing its own proteins.

Spontaneous Generation

The historical idea that living organisms can arise spontaneously from lifeless or non-living matter.

Cell Theory

A fundamental biological theory stating that: 1. All living things are made up of one or more cells; 2. The cell is the basic unit of life; 3. All new cells come from pre-existing cells.

Prokaryotic Cells

Small, simple cells that lack a nucleus and do not have internal structures surrounded by membranes (e.g., bacteria and archaea).

Eukaryotic Cells

Larger, complex cells possessing a nucleus and membrane-bound internal organelles (e.g., plant, animal, and fungal cells).

Organelle

A tiny cellular structure that performs a specific function within a cell.

Cell Membrane

A protective barrier that surrounds the cell and regulates the movement of nutrients, wastes, and other substances into and out of the cell.

Cell Wall

A tough, rigid outer structure found in plant cells that encases the cell membrane and provides structural support and a box-like shape.

Cytoplasm

The thick, jelly-like fluid within a cell in which organelles are suspended.

Nucleus

The cell organelle that contains genetic information ($\text{DNA}$) and directs all cellular life processes.

Nucleolus

A small structure situated inside the nucleus responsible for producing ribosomes.

Endoplasmic Reticulum (ER)

A network of folded membranes continuous with the nuclear membrane that assists in manufacturing proteins; classified as Rough ER (covered in ribosomes) or Smooth ER (lacking ribosomes).

Ribosomes

Cellular structures that synthesize proteins using genetic instructions from $\text{DNA}$, either floating freely in the cytoplasm or bound to the endoplasmic reticulum.

Golgi Body

An organelle that modifies, sorts, and packages proteins so they can be distributed throughout or outside the cell; also known as the Golgi apparatus.

Vesicles

Small membrane-bound sacs that pinch off from the Golgi body to transport proteins around the cell.

Lysosome

An organelle containing digestive enzymes that breaks down cellular waste, foreign bacteria, and viruses so parts can be recycled.

Vacuole

A storage organelle holding water, nutrients, and waste products; plant cells possess a single large central vacuole, whereas animal cells have many smaller vacuoles.

Mitochondria

Organelles containing their own $\text{DNA}$ that generate cellular energy ($\text{ATP}$) through cellular respiration.

Chloroplast

A chlorophyll-containing plant cell organelle that absorbs sunlight to produce glucose through photosynthesis.

Photosynthesis

A chemical reaction carried out in plant chloroplasts that converts solar energy, carbon dioxide, and water into chemical energy in the form of sugar: $\text{carbon dioxide} + \text{water} + \text{energy} \rightarrow \text{sugar} + \text{oxygen}$.

Microorganism (Microbe)

Any microscopic living organism measuring less than $1\,\text{mm}$ that can only be viewed under a microscope, including bacteria, archaea, yeast, and phytoplankton.

Pathogen

A biological agent or microorganism capable of causing disease or illness, such as viruses, bacteria, and fungi.

Immune System

A bodily defense network of cells, tissues, molecules, and organs that detects, attacks, destroys, and remembers disease-causing pathogens.

First Line of Defence

Innate physical and chemical barriers that block pathogens from entering the body, including skin, respiratory cilia, mucus, tears, saliva, and stomach acid.

Second Line of Defence

A rapid, non-specific internal immune response that occurs within minutes to hours of pathogen entry, involving white blood cells, inflammation, and fever.

Phagocytes

A specialized group of white blood cells that engulf and ingest invading pathogens, infected cells, or debris through phagocytosis.

Inflammation

A localized second-line defense response causing increased blood circulation to an affected area, leading to redness, swelling, warmth, and the arrival of white blood cells.

Fever

An intentional rise in core body temperature above $38\,^\circ\text{C}$ that slows or destroys heat-sensitive pathogens and accelerates immune repair processes.

Third Line of Defence (Adaptive Immunity)

A targeted immune response involving specialized lymphocytes that slowly recognizes, attacks, and creates long-term memory against specific pathogens.

B Cell

A specialized white blood cell of the adaptive immune system that synthesizes and secretes pathogen-specific antibodies into the bloodstream.

Antibody

A protein molecule produced by B cells that specifically binds to matching antigens on pathogens, tagging them for elimination by other immune cells.

Antigen

A unique marker molecule found on the surface of a pathogen that elicits an antibody response.

Memory B Cells

Long-lived lymphocytes that retain specific structural information about a pathogen to mount a rapid defense upon future reinfection.

Killer T Cells

Effector cytotoxic T cells ($\text{CD8}$) that identify and destroy infected, damaged, or abnormal body cells.

Helper T Cells

Regulatory T cells that activate B cells to produce antibodies or signal Killer T cells to destroy target cells.

Autoimmune Disease

A condition in which the immune system mistakenly recognizes the body's own healthy tissues as foreign and attacks them (e.g., Type 1 Diabetes, Lupus, Rheumatoid Arthritis, Celiac Disease).

Allergen

An environmental substance that is normally harmless but triggers an exaggerated, overactive immune response (e.g., causing asthma, eczema, or allergic rhinitis).

Traditional Ecological Knowledge (TEK)

Knowledge regarding local ecosystems, plants, animals, and waters acquired and shared by Indigenous peoples across generations through observation, traditions, and oral teachings.

Muskeg

A peat-forming wetland ecosystem characterized by waterlogged ground, acidic conditions, and slow-decaying sphagnum moss, similar to a bog.

Peat

Partially decayed plant and organic matter that accumulates over prolonged periods in waterlogged, oxygen-poor environments.

Antibiotics

Pharmaceutical substances that combat bacterial infections by killing bacteria or stopping their growth and replication; ineffective against viral infections.

Superbugs

Bacterial strains that have developed resistance to multiple classes of antibiotics, such as Methicillin-resistant Staphylococcus aureus ($\text{MRSA}$).

Vaccine

A biological preparation administered orally or via injection that stimulates adaptive immune memory against a specific disease without causing full illness.

Live-Attenuated Vaccine

A vaccine formulated with living microbes that have been weakened so they cannot cause illness, typically establishing long-lasting immunity in $1\text{ to }2$ doses.

mRNA Vaccine

A vaccine containing synthetic messenger RNA that instructs host cells to manufacture a harmless viral fragment (such as a spike protein) to elicit an antibody response.

Inactivated Vaccine

A vaccine containing whole pathogens killed by heat, chemicals, or radiation, inducing a milder immune response that usually requires booster doses.

Toxoid Vaccine

A vaccine utilizing inactivated toxins generated by pathogenic bacteria to prompt targeted toxin-neutralizing immunity (e.g., tetanus and diphtheria).

Subunit Vaccine

A vaccine formulated from specific isolated antigens or pieces of a pathogen rather than the whole microbe, requiring multiple doses to build immunity.

Herd Immunity

Indirect protection from an infectious disease that occurs when a high proportion of a population is immune, limiting transmission and protecting unimmunized individuals.

Outbreak

A sudden and unexpected increase in the incidence of a specific disease within a localized setting.

Epidemic

A widespread and rapid transmission of an infectious disease within a defined geographical area or specific population.

Pandemic

An epidemic of an infectious disease that expands across international boundaries, affecting multiple continents or populations worldwide.