Year 9 Science Semester 2 Exam Revision Guide

Big Bang Theory

Universe originated from a singularity explosion.

Steady State Theory

Universe continuously creates matter, maintaining density.

Cosmological Theory

Widely accepted theory explaining universe's origin.

Evidence for Big Bang

Cosmic Microwave Background Radiation supports the theory.

Speed of Light

Approximately 3 × 10^8 metres per second.

Light Travel Time

Light takes about 500 seconds to reach Earth.

Doppler Effect

Change in frequency due to relative motion.

Redshift

Light shifts to longer wavelengths from moving objects.

Electromagnetic Radiation

Energy waves across a spectrum, varying in frequency.

Radio Waves

Used in communication technologies like broadcasting.

Microwaves

Used in cooking and satellite communications.

Infrared Radiation

Used in thermal imaging and remote controls.

Visible Light

The spectrum of light visible to the human eye.

Ultraviolet Light

Used in sterilization and detecting counterfeit money.

X-rays

Used in medical imaging to view internal structures.

Gamma Rays

Used in cancer treatment and sterilizing medical equipment.

Infectious Disease

Caused by pathogens, spreads between individuals.

Non-infectious Disease

Caused by lifestyle or genetic factors, not pathogens.

Infection

Pathogen entry and multiplication in the body.

Antibodies

Proteins that neutralize pathogens in the immune response.

Active Immunity

Immunity developed after exposure to a pathogen.

Passive Immunity

Immunity acquired through antibodies from another source.

First Line of Defence

Physical and chemical barriers preventing pathogen entry.

Second Line of Defence

General immune response against all pathogens.

Third Line of Defence

Specific immune response targeting particular pathogens.

Decomposers

Organisms that break down dead material, recycling nutrients.

Keystone Species

Species that significantly impacts ecosystem structure.

Invasive Species

Non-native species disrupting local ecosystems.

Carbon Cycle

Process of carbon exchange among Earth's systems.

Biotic Factors

Living components of an ecosystem, like plants and animals.

Abiotic Factors

Non-living components, such as water and soil.

Trophic Levels

Feeding positions in a food chain or web.

Energy Transfer Efficiency

Typically, only 10% energy is passed to next level.

Energy Transfer

Movement of energy from one trophic level to another.

Food Web

Complex network of feeding relationships among organisms.

Ecosystem Resilience

Ability of an ecosystem to recover from disturbances.

Deforestation

Clearing of forests impacting carbon storage and emissions.

Land Use Changes

Alterations in land for urbanization or agriculture affecting ecosystems.

Physical Change

Change affecting form but not chemical composition.

Chemical Change

Change resulting in new substances with different properties.

Exothermic Reaction

Reaction releasing energy, usually as heat.

Endothermic Reaction

Reaction absorbing energy from surroundings.

pH Scale

Measurement of acidity or alkalinity of a solution.

Photosynthesis

Process by which plants convert sunlight into energy.

Chlorophyll

Green pigment in plants essential for photosynthesis.

Chloroplast

Organelles in plant cells where photosynthesis occurs.

Respiration

Process of converting glucose into energy in cells.

Cellular Respiration

Metabolic process converting biochemical energy from nutrients.

Anaerobic Respiration

Energy production without oxygen, yielding less energy.

Neutralization

Reaction between an acid and a base producing salt and water.

Ocean Acidification

Decrease in ocean pH due to increased CO2 absorption.

Ion Concentrations

Levels of charged particles in a solution affecting pH.

Symbiotic Relationship

Interaction between two different organisms living together.

Variables in Experiments

Factors that can change and affect experimental outcomes.

Controlled Variables

Factors kept constant to ensure valid test results.

Independent Variable

Factor manipulated to observe its effect on the dependent variable.

Dependent Variable

Factor measured in response to changes in the independent variable.

Word Equation

Descriptive representation of a chemical reaction using words.

Symbol Equation

Chemical representation of a reaction using chemical symbols.

Graphs in Biology

Visual representations of data to analyze trends and relationships.