PSLCE Primary Science flashcards

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

Life processes

Seven processes shown by all living things: movement, respiration, sensitivity, growth, reproduction, excretion and nutrition. A non-living object may show one or two but never all seven.

Respiration

A chemical reaction in cells that releases energy from glucose, using oxygen and producing carbon dioxide and water. It happens in plants and animals day and night.

Excretion versus egestion

Excretion removes waste produced by cell reactions, such as carbon dioxide and urine. Egestion removes undigested food from the gut, which was never absorbed into the body.

Sensitivity

The ability to detect and respond to a stimulus such as light, sound or touch. A receptor detects it, a coordinator processes it, and an effector carries out the response.

Xylem and phloem

Two plant transport tissues. Xylem carries water and dissolved minerals upward from roots to leaves. Phloem carries dissolved sugars from leaves to other plant parts in both directions.

Root hair cell

A long thin extension of a root epidermal cell. Its large surface area speeds up absorption of water and mineral salts, and it anchors the plant in soil.

Pollination versus fertilisation

Pollination is the transfer of pollen from anther to stigma. Fertilisation is the later fusion of male and female gametes inside the ovule, forming a seed.

Germination requirements

Most seeds need water, oxygen and a suitable warm temperature to germinate. Light is not needed, because the young plant uses stored food in the seed at first.

Seed dispersal

Movement of seeds away from the parent plant. Wind, water, animals and explosive bursting are agents; dispersal reduces competition for light, water and space.

Villi

Tiny finger-like folds lining the small intestine. They greatly increase surface area for absorbing digested food into the blood, and each has a rich blood supply.

Bile

A green liquid made in the liver and stored in the gall bladder. It emulsifies fats into small droplets, increasing the surface area for digestive enzymes to act on.

Breathing mechanism

The diaphragm and intercostal muscles contract, the rib cage moves up and out, chest volume increases, pressure falls and air flows into the lungs.

Deficiency diseases

Illnesses caused by missing nutrients. Lack of vitamin C causes scurvy, lack of vitamin D or calcium causes rickets, and lack of iron causes anaemia.

Balanced diet

A diet giving all needed nutrients in the right amounts: carbohydrates and fats for energy, proteins for growth and repair, vitamins and minerals, fibre and water.

States of matter

Solids keep shape and volume, liquids keep volume but take container shape, and gases fill any container. Particle spacing and movement explain the differences.

Dissolving

A solute spreads evenly through a solvent to form a solution. It is a physical change, and the solute can be recovered by evaporating the solvent.

Filtration and evaporation

Filtration separates an insoluble solid from a liquid using filter paper. Evaporation removes the liquid from a solution so a dissolved solid is left behind.

Chemical change signs

A new substance forms. Signs include colour change, gas bubbles, heat or light released, a precipitate forming, or a change that is difficult to reverse.

Density rule for floating

Density is mass divided by volume. An object floats in a liquid when its density is lower than the liquid's density, and sinks when its density is higher.

Thermal conductors

Materials that transfer heat quickly, such as metals. Insulators such as wood, plastic, wool and trapped air transfer heat slowly and reduce heat loss.

Weight versus mass

Mass is the amount of matter, measured in kilograms and unchanged by location. Weight is the pull of gravity on that mass, measured in newtons.

Friction

A force between surfaces in contact that opposes motion. It produces heat, can be reduced by lubrication or smoothing, and is increased by rougher surfaces.

Lever

A simple machine with a pivot, an effort and a load. A longer effort arm gives a greater turning effect, allowing a smaller force to move a larger load.

Speed formula

Speed equals distance divided by time. Average speed is total distance divided by total time, so it accounts for both fast and slow parts of a journey.

Water cycle

Evaporation and transpiration add water vapour to air, which condenses into clouds; precipitation returns water, which runs off or infiltrates the ground.

Weather versus climate

Weather is the day-to-day condition of the atmosphere. Climate is the long-term average pattern of a place, so single days do not define it.

Renewable resources

Resources naturally replaced faster than used, such as sunlight, wind, flowing water and biomass. Fossil fuels are non-renewable and release carbon dioxide when burned.

Topsoil

The upper soil layer, dark and rich in humus and plant roots. It holds water and nutrients and supports most plant growth, so erosion of it harms farming.

Food chain arrows

Arrows show the direction of energy flow from producer to consumer. Energy is lost as heat at each stage, so most chains have only four or five links.

Decomposers

Organisms such as bacteria and fungi that break down dead plants and animals. They release nutrients back into the soil for producers to absorb again.

Fair test

An investigation changing only the independent variable, measuring the dependent variable, and keeping all other variables constant so the result is valid.

Reliable measurement

Repeating readings and taking a mean improves reliability. Precision comes from finer-scale instruments, while accuracy means closeness to the true value.

Food preservation

Methods such as drying, salting, freezing, canning and smoking slow microorganism growth. Refrigeration slows growth but does not stop it completely.

Safe water treatment

Steps to make water safe: allow solids to settle, filter remaining particles, then boil or chlorinate to kill pathogens before drinking.