cb4 - natural selection and genetic modification

• Natural Selection


  Charles Darwin's theory of natural selection proposed that all species have evolved from simple life forms that first appeared on Earth more than three billion years ago. 
• genetic variation


  different individual animals in a population or species have different combination of genes/ show genetic variation
• survival of the fittest


  individuals that are best adapted to the environment will have a greater chance of survival
• successful breeding 


  individuals with the best chances of survival are the most likely to breed successfully - because they survive
• The best characteristics survive 


  the characteristics responsible for the greater chance of survival are more likely to be passed on to the next generation
• what is the process of natural selection?


  variation

  overpopulation

  survival of the fittest

  adaption

  genes passed on
• Bacteria reproduce rapidly. Mutations occur during reproduction. This means that bacteria can evolve rapidly.
• if a mutated bacterial pathogen is resisted to antibiotics, when a person is treated with antibiotics, the bacteria will survive and go on to reproduce. this bacteria is the original ancestor of a new resistant strain. this bacteria will spread, as there will be no treatment for it, and people are not immune to it - as they were previously treated with antibiotics
• an example of antibiotic resistance bacteria is MRSA
• the development of new antibiotics is a slow and costly process. it struggles to keep up with the emergence of new strains
• measures must be taken to reduce the emergence of new antibiotic resistant strains


  doctors should avoid prescribing antibiotics unnecessarily - for treating non-serious infections.

  patients must finish a course to make sure all bacteria are killed

  the use of antibiotics in agriculture should be restricted - cattle feed
• Evolution is the gradual change of inherited characteristics of biological populations over time. It is usually driven by natural selection. 
• Evolution is 


  the gradual change of inherited characteristics of biological populations over time.
• what drives evolution

  natural selection
• evolution theory has greatly affected modern biology: 


  genetics - discovered how traits are inherited - genes

  evolutionary biology - how species changed over time and how different species are related to eachother
• two main sources of evolution


  fossils

  antibiotic resistant bacteria
• how do fossils provide evidence for evolution


  fossils show the gradual changes in organisms over time
• how do antibiotic resistant bacteria provide evidence for evolution


  show natural selection
• Fossils are the remains or traces of ancient life
• Fossils are found in rocks and have been preserved by natural processes. 
• how are fossils preserved?

  natural processes
• 3 ways of forming fossils

  hardening soft materials

  preservation where decay is not possible

  mineral replacement
• how does hardening soft materials preserve fossils inside rocks


  the hardening of soft materials can produce casts or impressions such as footprints
• how does preservation when decay is not possible preserve fossils inside rocks

  where decomposers cannot act, preservation is possible - decomposers cannot operate in glaciers and peat bags
• where cant decomposers operate with examples

  
  

  glaciers due to extreme low temperatures and peat bogs due to extreme acidity
• how does mineral replacement preserve fossils inside rocks


  hard parts of organisms are gradually replaced by minerals as they decay slowly, creating a rock-like substance. when the surrounding sediment turns to rock, the teeth shaped mineral structure remains distinct
• Why is the fossil record incomplete?

  • A lot of early life forms were soft-bodied. Therefore, they did not leave behind many noteworthy traces.
  • Geological activity has also caused the destruction of many traces of ancient life.
  • Because of this, scientists cannot be certain about the origins of life on Earth.
• Fossils can be dated, so scientists have evidence for what organisms looked like at different periods in time. Comparing the fossils indicates how humans have changed over time.
• human evolution fossils


  ardi

  lucy

  leakey
• ardi

  the oldest fossilised human remains - dating back 4.4 million years
• lucy


  3.2 million years old
• leakey


  1.6 million years old
• Stone tools show how humans have evolved: the more complex the tools used, the more developed the brain of the user. This can be linked with the fossil record.
• how did stone tools look 2.6 million years ago?


  flakes of rock with a sharp edge. - very basic
• what happened to stone tools 1.6 million years ago


  they became more sophisticated and abundant
• why cant you use carbon dating to date a stone tool?


  because carbon dating tells us only when the rock was originally formed
• how to date stone tools


  • determine how deeply it was buried
  • use known dates of other items or fossils found at that level
  • compare the design to other stone tools that are already dated
• what does how deep a stone tool was buried tell us about the tool?


  the deeper, the older it is more likely to be
• classification systems


  traditional - carl linnaeus

  3 domain system - carl woese
• Classification groups organisms by comparing their similarities and differences: