science

• what is refraction?

  Bending of light.
• two expamples of when refraction takes place in real life

  twinkling of stars in clear sky

  
  

  glasses
• what is a convex lens
• Natural selection is known as ‘the survival of the fittest’
• The best adapted organisms are able to survive
• The most desirable characteristics get passed down from parents to their offspring
• Scientists have used fossils to look at how organisms have evolved over time
• Natural selection is a process by which a species changes over time in response to changes in the environment or competition between organisms
• Species change in order to survive
• The members of the species with the most desirable characteristics are able to produce the best-adapted offspring
• If a species is unable to adapt, it is at risk of becoming extinct
• Evolution is a slow process that can take many thousands, even millions, of years to happen
• Charles Darwin’s theory of evolution suggests that different species have evolved from simpler life forms
• Organisms that survive are those that have adapted best to their environment
• Scientists have used fossil evidence to study how organisms have adapted over millions of years
• If a species is unable to adapt quickly enough to its environment, it is at risk of becoming extinct due to reasons like new predators, diseases, destruction of habitats, changes to the environment, and increased competition for resources
• The skeleton allows movement, provides support and protection for vital organs and makes blood cells
• Skeletal muscles move the bones in the body
• The skeletal system is made from bones and joints
• The femur bone in the thigh is the longest and strongest bone in the body
• The smallest bones in the body are called the ossicles in the ear
• Bone is a living tissue with a blood supply
• Bones are constantly being dissolved and formed and can repair themselves if broken
• Calcium is important for bone repair
• Bones work with muscles and tendons to allow the body to move
• The spinal cord is surrounded by vertebrae which protect it
• Most people are born with 33 vertebrae but adults usually have 24 due to some joining together naturally as the body grows
• The major bones in the legs are the femur, fibula, and tibia which allow a person to stand upright
• The bones protect vital organs such as the brain, spinal cord, heart, lungs, and liver
• Some bones in the skeleton are joined rigidly together and cannot move against each other, like the bones in the skull
• Other bones are joined by flexible joints, such as the shoulders, elbows, and knees
• Muscles are attached to bones by tendons and contract and relax to move bones
• Blood cells, including red and white blood cells, are made in the bone marrow
• Microorganisms and plants have evolved to produce substances that can be used as medicines or modified in a lab for medicinal purposes
• Examples of drugs developed from natural sources include:

  • Aspirin: developed from a chemical found in the bark of willow trees, used as a painkiller and to lower fevers
  • Digitalis: used to treat heart problems, originally developed from a chemical found in foxgloves
  • Penicillin: discovered by Alexander Fleming from a fungus that produced a substance called penicillin, the first widely used antibiotic
• When testing a new drug, three main factors are considered:

  • Efficacy: how well the drug works in producing the desired effect
  • Toxicity: how harmful the drug is and if it has any side effects
  • Dosage: determining the appropriate amount or concentration of the drug to be given
• There are three main stages of drug testing:

  • Pre-clinical testing on human cells and tissues in a laboratory
  • Testing on live animals to assess efficacy and toxicity
  • Clinical testing on humans, starting with healthy volunteers and then individuals with the specific illness targeted by the drug
• Clinical trials should be blind and use placebos to avoid unconscious bias:

  • Placebos are substances that look like the real drug but have no therapeutic effect
  • Double-blind trials involve neither the doctors nor the volunteers knowing who received the real drug until after the study is completed
• After drug testing is complete, the results are written up and peer-reviewed by other scientists to ensure the validity of the tests and prevent false claims or results from being published
• The human body's defense system is split between physical and chemical barriers and the immune system