Ns

• Scientific Method


  A series of steps used to investigate natural occurrences
• Variables


  • Able to change
  • Any factor, trait or condition that can exist in varying amounts or types and can change over time
• Independent variable


  The one you are going to change or manipulate
• Dependent variable


  The one(s) you are going to measure or observe
• Fixed/controlled variables


  All those that you keep the same to make the test fair
• Experiment


  1. Questions the relationship between two variables - cause and effect

  2. Driven by hypothesis

  3. Follows the traditional scientific method
• Investigation


  • Draws an investigative question
  • Not always involves variables
  • Hypothesis not required
• Experimental control


  The control acts as a comparison to the experiment
• Experimental control


  • Allows researchers to be sure that any differences between the results is due to the independent variable
  • The independent variable is different from the control
• Experimental control is not the same as the controlled variables
• How to improve experiments


  1. Ensure validity/fairness by keeping all the fixed variables the same

  2. Improve reliability by repeating the experiment

  3. Increase the sample size
• Ways to improve measurement

  • Measuring with precision
  • Knowing how to use the apparatus
  • Ensuring the apparatus works properly
• Cell


  Basic structural and functional unit of all living organisms
• Microscopic organisms


  • Have 1 cell = unicellular e.g. bacteria
• Macroscopic organisms


  • Many cells = multicellular e.g. plants
• Cells


  • Different shapes for different functions
• Organelles


  Tiny cellular structures that perform specific functions within a cell
• Cell wall


  • Found in plant cells only
  • Provides shape and support
• Cell membrane


  • Encloses the cell
  • Allows substances into and out of the cell
  • Selectively permeable
• Cytoplasm


  Liquid in which chemical processes take place and in which organelles are found
• Mitochondria


  • Responsible for cellular respiration
  • Uses oxygen and glucose to produce energy
• Chloroplast


  • Responsible for photosynthesis
• Organelles are found in the cytoplasm
• Phosphate backbone


  Part of the DNA structure
• Vacuoles


  Storage of water, larger in plant cells, smaller in animal cells
• Ribosomes


  Responsible for protein synthesis
• Nucleus


  • Surrounded by nuclear membrane
  • Contains DNA (hereditary information)
  • Controls the cell's functions
• DNA


  Deoxyribonucleic acid
• Nitrogen bases


  • Adenine (A)
  • Thymine (T)
  • Cytosine (C)
  • Guanine (G)
  • Phosphate backbone
• Uses of DNA


  • DNA extraction can be used to gather evidence in criminal investigations
  • DNA extraction can be used to modify / change / improve plants and animals (genetic engineering)
  • DNA is also used to verify people's identity
  • DNA can also be used to make vaccines and create hormones like insulin
• Differences between plant and animal cells

  • Animal cells are smaller
  • Animal cells have no cell wall
  • Animal cells have a nucleus in the center
  • Animal cells have many vacuoles
  • Animal cells cannot synthesize nutrients
  • Animal cells have no plasmodesmata
  • Animal cells have no chloroplasts

  Plant cells are larger

  • Plant cells have a cell wall (cellulose)
  • Plant cells have a nucleus
  • Plant cells have a large vacuole (central vacuole)
  • Plant cells synthesize nutrients
  • Plant cells have plasmodesmata
  • Plant cells have chloroplasts
• Specialized cells


  • Cells have many specific functions, shapes and structures to perform specific functions
• Stem cells


  Unspecialised cells that have the ability to divide and develop into different types of cells
• DNA


  Deoxyribonucleic acid
• DNA


  • Found on our chromosomes in the nucleus of our cells
  • Made up of two twisted strands called a double helix
  • The two strands are made up of millions of nitrogen bases that have a unique code
• Every person has about 6 trillion bases making up their DNA
• Animal cells

  -Smaller

  -no cell wall

  -nucleus in center

  -one small vacoule

  -cannot synthesise nutrients

  -no plasmodesmat

  -no chloroplasts
• Plant cells

  -larger

  -cell wall ( cellulose)

  -nucleus on the side

  -large vacoule(Tonoplast)

  -synthesises nutrients

  -has plasmodesmata

  -have chloroplasts
• Organisation levels

  Cells: basic unit of life

  ⬇️

  tissues: made up of similar cells grouped together

  ⬇️

  organs: made up of many different layers of tissues

  ⬇️

  system: made up of organs
• Example of organisation levels 


  Muscle cell

  ⬇️

  Cardiac muscle

  ⬇️

  heart

  ⬇️

  cardiovascular system