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Biology  
 
•   Stem  Cells    
-­   Do  not  have  a  specific  function    
-­   Cells  that  have  not  yet  differentiated  and  therefore  they  can  develop  into  any  type  of  
body  cell  
-­   Do  not  have  a  Hayflick  limit  (continue  to  divide)  
-­   You  can  find  these  in  the  embryo,  umbilical  cord  and  bone  marrow  
 
•   Mitosis    
-­   Produces  two  daughter  cells    
-­   Can  be  used  for  all  body  cells  except  for  growth  and  repair    
-­   The  daughter  cells  are  genetically  identical  
-­   Diploid    
-­   One  cell  division  
 
•   Meiosis    
-­   Produces  four  cells  that  are  haploid  and  not  genetically  identical    
-­   Produces  sex  cells  (gametes)  
-­   Haploid    
-­   Two  cell  divisions  
 
•   The  Hayflick  limit  -­  The  Hayflick  limit  is  the  number  of  times  a  normal  human  cell  
population  will  divide  until  cell  division  stops
...
 Transformed  cells  (tumor  cells)  are  an  exception  
 
•   Evolution  by  Natural  Selection    
- Variation  in  the  species  (mutation?)    
-­   There  is  a  selection  pressure  (change  in  the  environment)  
-­   Organisms  not  suited  die  and  over  time  they  become  extinct  
-­   Organisms  suited  survive,  mate  and  pass  on  their  genes  
-­   Future  generations  are  well  adapted  
-­   This  process  is  very  gradual  
 
•   Cloning    
-­   A  clone  is  an  organism  that  is  genetically  identical  to  his  parent  
-­   Cloning  can  happen  through  asexual  reproduction,  embryo  cloning,  tissue  cloning  or  
taking  ‘cuttings’
...
 This  is  performed  in  a  carefully  
controlled  environment  
 
•   DNA    
-­   Short  for  ‘deoxyribonucleic  acid’  
-­   They  carry  the  genetic  code  that  determines  the  characteristics  of  a  living  thing
...
 

-­   Found  in  the  nucleus  of  a  cell,  in  the  chromosomes  
-­   Except  for  identical  twins,  each  person’s  DNA  is  unique
...
 
 
 
•   Gene  
-­   A  small  section  of  DNA  that  determines  a  particular  feature
...
 It  can  happen  in  individual  
genes  of  in  whole  chromosomes
...
 These  genes  may  have  different  forms
...
 
-­   Alleles  are  dominant  or  recessive:  
-­   The  characteristic  controlled  by  a  dominant  allele  develops  if  the  allele  is  present  on  one  
or  both  chromosomes  in  a  pair  
-­   The  characteristic  controlled  by  a  recessive  allele  develops  only  if  the  allele  is  present  
on  both  chromosomes  in  a  pair  
 
•   Continuous  Variation    
-­   Human  height  is  an  example  of  continuous  variation
...
 
Any  height  is  possible  between  these  values
...
 
-­   For  any  species  a  characteristic  that  changes  gradually  over  a  range  of  values  shows  
continuous  variation
...
 
 
•   Discontinuous  Variation  
-­   Human  blood  group  is  an  example  of  discontinuous  variation
...
   
-­   There  are  no  other  possibilities  and  there  are  no  values  in  between
...
 
-­   A  characteristic  of  any  species  with  only  a  limited  number  of  possible  values  shows  
discontinuous  variation
...
 
 
 
   
•   8  life  processes  which  are  common  to  most  living  things
...
  Require  nutrition  –  either  they  make  their  own  food,  as  in  plants,  or  eat  other  organisms  
as  animals  do  
2
...
  Move  –  by  the  action  of  muscles  in  animals  and  slow  growth  movements  in  plants  
4
...
  Respire  –  get  energy  from  their  food  

6
...
  Reproduce  –  produce  offspring  
8
...
 
-­   Proteins  –  need  it  for  growth  and  repair  of  tissues,  enzymes  are  made  of  protein  
-­   Minerals  –  healthy  for  your  teeth  and  bones  
-­   Vitamins    
-­   water  
 
 



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