B3 Life on Earth by sdfwerte

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									B3 Life on Earth

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      How did life on Earth begin and
                  evolve?         Or did they
 Life on Earth                        come from
 began about                          elsewhere in
 3500 million                         the solar
 years ago.                           system?




                                   The molecules
Simple organisms                   could have been
developed from                     produced by
molecules that                     environmental
could copy                         conditions on
themselves                         Earth at that time
                                                         Evolution
          What is Evolution?                             happens
                                                        by natural
                    Individuals of a species             selection
                    are not identical –their
                    characteristics vary.
The environment changes                Resources become scarce

                             Competition!
   Individuals with certain characteristics have a better chance
   of surviving

                            Next Generation
         More individuals have these useful characteristics


                            Next Generation
        Even more individuals have these useful characteristics
                        Variation
Variation is a name given to differences in a species, e.g. dogs:




Variation is due to each animal having different GENETIC
INFORMATION in their cells. Variation within a species is
due to the ENVIRONMENT and GENES.
        Cells mutate when:
• Mistakes are made when copying
  chromosomes
• Ionizing radiation changes the DNA
• Some chemicals can change DNA
    What if sex cells mutate?
• The mutation may have no effect
• The fertilized egg may not develop
• The offspring may have a better chance of
  surviving and reproducing. Then the
  mutated gene passes on to the next
  generation and becomes more common.
• Over many years and generations, new
  species have evolved.
• This is the result of the effects of
  mutations, environmental change, and
  natural selection.
         How did humans evolve?
 Many different        Those with
hominid species     bigger brains and
 evolved from a    who walked upright
common ancestor    had a better chance
                       of surviving


                      Gradually all
                  hominid species except
                     Homo sapiens
                     became extinct
 How are human communication
      systems organised?
• Multicellular organisms evolved 2
  communication systems:
                Nervous Systems



                 Hormones
                 QUESTIONS
• B3 Life on Earth
1. What makes organisms members of the same species?
2. What are the two different causes of variation in living
   things?
3. What is the evidence for evolution?
4. Describe selective breeding and give an example?
5. Briefly describe Natural selection
6. Sum up the main ideas of Lamark and Darwin.
7. What are the body’s two main communication
   systems?
       The Nervous System
• Uses electrical impulses to transmit
  messages and respond quickly
• Is made of neurones
• Is controlled by the brain and spine (CNS)
                 Hormones
•   Are chemicals that travel in the blood
•   Carry information all over the body
•   Bring about long lasting effects
•   Eg testosterone
        insulin
              Homeostasis
• Homeostasis is keeping a constant
  internal environment.
• If you are too hot the brain detects that the
  blood temperature is too high.
• An electrical impulse makes your sweat
  glands work.
                 Food webs
Food webs contain many interlinking food chains… because
    all living organisms depend on other species and the
                  environment for their needs.
                Breaking the links
Q. What would
happen if an animal
or organism was
“taken out”?

     e.g take out
      the crab:




1) What would happen to the population of flat winkles?
                    They would probably ______ because…
2) What would happen to the population of herring gulls?
                    They would probably ______ because …
  Why do some species become
           extinct?
Sudden changes
in environmental            Other species in the
conditions                  food web become
                            extinct




  New species arriving
  that compete with, eat,
                                      X
  or cause disease of the
  species
 Why is biodiversity important?
• We may develop different medicines from
  species that we do not yet use.
• For new food sources : breeding cultivated
  rice with wild species may produce rice
  that is resistant to disease.
• This allows sustainable development :
  using the environment to meet the needs
  of people today without damaging Earth
  for the people of the future.

								
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