Grade 8 Mid Term - I Biology Review

Vocabulary practice flashcards covering plant biology, leaf adaptations, cell structures, the carbon cycle, and environmental changes from the Grade 8 Biology curriculum.

Photosynthesis

The chemical process, meaning 'making with light', by which green plants use carbon dioxide and water, powered by sunlight energy trapped by chlorophyll, to produce glucose and oxygen.

Word equation for photosynthesis

$$\text{carbon dioxide} + \text{water} \rightarrow \text{glucose} + \text{oxygen}$$

Chlorophyll

The green pigment located inside plant cells that absorbs and captures energy from sunlight for photosynthesis.

Magnesium

An essential mineral required by plant cells to synthesize the green pigment chlorophyll.

Nitrogen

An essential element provided by nitrates that plants require to convert carbohydrates into proteins for growth.

Starch

The insoluble carbohydrate stored in plant cells and chloroplasts when plants make more carbohydrate than needed immediately on warm, sunny days.

Palisade layer

The specialized tissue layer inside a leaf packed with chloroplasts that performs the vast majority of photosynthesis.

Spongy layer

A layer of cells inside a leaf containing numerous air spaces that carries out a small amount of photosynthesis.

Stomata

Tiny pores primarily found in the lower epidermis of a leaf through which carbon dioxide and other gases diffuse in and out.

Waxy layer

A protective covering on the leaf surface that prevents leaf cells from drying out.

Leaf veins

Vascular structures responsible for transporting water directly to the cells situated inside a plant leaf.

Boiling a leaf in water (Starch test)

The initial procedure in the starch test experiment used to break down plant cell membranes so iodine solution can penetrate the cells.

Iodine solution

A chemical indicator that turns blue-black in the presence of starch.

Hydrogen carbonate indicator

A testing solution that changes color to yellow when exposed to an increased concentration of carbon dioxide.

Plant respiration

A continuous metabolic process occurring day and night in which plants take in oxygen and release carbon dioxide to release energy from glucose.

Word equation for respiration

$$\text{glucose} + \text{oxygen} \rightarrow \text{carbon dioxide} + \text{water} + \text{energy}$$

Decomposers

Organisms that break down waste and dead organic matter to obtain carbon and return carbon dioxide to the atmosphere via respiration.

Combustion

The process of burning fossil fuels where carbon combines with oxygen from the air to form and release carbon dioxide.

Fossil fuels

Carbon-rich fuels, including coal, oil, and natural gas, formed from the deep burial and high pressure of dead organic matter over millions of years.

Greenhouse gases

Atmospheric gases, such as carbon dioxide and methane, that trap heat energy close to Earth's surface to keep the planet warm.

Fertilisers

Mineral-rich substances applied to soil by farmers to promote larger crop growth and generate higher agricultural yields.

Thermal expansion of water

The physical expansion of water as its temperature rises, directly contributing to sea level rise when global temperatures increase.

Meteoroids

Objects in space that are smaller than asteroids.

Mass extinction

A catastrophic event where a vast portion of Earth's biodiversity is eliminated, such as the estimated $75\%$ of all species that went extinct following an asteroid collision.

Chloroplast

An organelle found inside green plant cells that contains chlorophyll and serves as the site for photosynthesis.

Cell wall

The outermost rigid layer that provides structural support and protection around a plant cell.

Vacuole

A large central membrane-bound compartment in a plant cell that stores water, nutrients, and cell sap.