Natural Sciences Grade VIII - Summary Notes (Chapters 1-6)

60 practice flashcards derived from the lecture notes on cells, body systems, energy, waves, elements, mixtures, and Earth science.

What does the cell theory state?

All living things are composed of cells; all cells come from preexisting cells; and a microscope is a tool used to magnify small objects.

Who invented the microscope and in which year?

Robert Hooke, 1663.

Name the two main types of microscopes used to view cells.

Light microscope and Electron microscope.

What is the basic structural and functional unit of life?

The cell.

Which organelle produces energy through cellular respiration?

Mitochondria.

What is the function of the cell membrane?

Controls entry and exit of materials into and out of the cell.

What is the outermost part of a plant cell that protects it?

The cell wall.

What process involves stomata taking in CO2 and releasing O2?

Gas exchange via stomata (stomata open to allow CO2 in and O2 out).

What cells regulate the opening and closing of stomata to reduce water loss?

Guard cells.

Which plant cell specialization increases water absorption by increasing surface area?

Root hair cells.

Which organelle carries out photosynthesis?

Chloroplasts.

What is the jelly-like fluid inside cells where chemical reactions occur?

Cytoplasm.

What are the three main statements of cell theory?

All living things are made of cells; all cells come from preexisting cells; a microscope is a tool used to magnify small objects.

What are the two major types of digestion?

Mechanical digestion and chemical digestion.

What is digestion?

The process of breaking down food into small nutrients.

Which nutrient is the primary energy source in foods?

Carbohydrates.

Which nutrient provides a concentrated energy reserve in the body?

Fats.

Which nutrient is mainly used to build and repair body tissues?

Proteins.

Which nutrients are needed in small amounts for normal body function?

Vitamins and minerals.

What is the role of water in nutrition?

Water helps remove metabolic waste and supports proper body function.

Which blood cells transport oxygen using hemoglobin?

Red blood cells.

What is the function of the cell nucleus?

To organize the cell’s activities and contain genetic material.

What are two key differences between plant and animal cells?

Plant cells have cell walls and chloroplasts; animal cells do not.

What is the difference between a closed and an open circulatory system?

Closed: blood always flows in vessels; Open: blood flows freely in body cavities.

Which blood vessels carry blood away from the heart?

Arteries.

Which blood vessels carry blood back to the heart?

Veins.

What are capillaries?

Small vessels where oxygen and carbon dioxide are exchanged between blood and body tissues.

How many chambers does the heart have and what are they called?

Four chambers: right atrium, left atrium, right ventricle, left ventricle.

What is the main function of the digestive system?

To break down food into nutrients that the body can use.

Where does most nutrient absorption occur in the digestive tract?

Small intestine (duodenum, jejunum, ileum).

What is the primary function of the large intestine?

Absorbs water and forms feces.

What part of the respiratory system helps clear particles with cilia?

Trachea.

What waste products are excreted by the lungs?

Carbon dioxide (CO2) and water vapor.

Name key organs of the excretory system.

Kidneys, skin, lungs, liver (and other detoxification organs).

What is the formula for work in physics?

W = Force × Distance (W = F × s).

What is the unit of work?

Joules.

What is power in physics?

Power is the rate at which work is done; P = W/t.

What is kinetic energy?

Energy due to an object's motion.

What is potential energy?

Energy due to position; Ep = mgh.

Name a simple machine commonly used to move loads more easily.

Pulley.

What is the function of a pulley?

To change the direction of force and reduce the effort needed to move a load.

What is an inclined plane?

A flat surface set at an angle to reduce the effort required to raise a load.

What is a lever?

A rigid bar that pivots about a fulcrum to lift or move loads.

What are the three classes of levers?

Type 1: fulcrum between load and effort; Type 2: load between fulcrum and effort; Type 3: effort between fulcrum and load.

What is crystallization?

Precipitating a dissolved substance by heating.

What is distillation?

Separating liquids based on differences in boiling points.

What is a compound?

A substance formed from two or more elements chemically bonded.

What is a mixture?

A combination of two or more substances that retain their original properties.

What is a solution?

A homogeneous mixture where solute dissolves in solvent.

What is a colloid?

A mixture where dissolved particles remain suspended and do not settle.

What is a suspension?

A heterogeneous mixture in which particles are not fully dissolved.

What is filtration?

Separating smaller particles using a filter.

What is centrifugation?

Separating mixtures by rapid rotation to separate liquids and solids.

What is evaporation?

Removing solvent to leave behind the dissolved substance as a solid.

What is chromatography?

Separating components using a moving medium and a stationary medium.

What is decantation?

Separating liquids from solids by pouring off the liquid.

What is magnetic separation?

Separating magnetic materials from non-magnetic materials.

What did Wegener propose about Earth's history?

Continental drift—the idea that continents were once a single landmass (Pangaea).

What were the names of the two large landmasses that split from Pangaea?

Gondwana and Laurasia.

What are the three types of plate movement?

Divergent (plates move apart), Transform (plates slide past each other), Convergent (plates collide).