The document discusses natural selection and evolution through Darwin's theory. It explains that populations vary genetically, individuals better suited to the environment are more likely to survive and reproduce, and over generations this leads to evolution and speciation as traits accumulate. The document provides examples of fossil evidence showing changes over time, such as different horse species, and how bacteria can evolve resistance to antibiotics through natural selection.

1. Natural Selection
10th May 2010

2. Learning Outcome
• I can explain why there are so many
different species of animals and plants
• I can describe how these species have
changed over time

3. Lamarck

4. Lamarckian Evolution

5. Lamarckian Evolution

6. Lamarckian Evolution
• Animals and plants notice that the
environment has changed

7. Lamarckian Evolution
• Animals and plants notice that the
environment has changed
• Animals and plants choose to change to
better fit the environment

8. Lamarckian Evolution
• Animals and plants notice that the
environment has changed
• Animals and plants choose to change to
better fit the environment
• WARNING

9. Lamarckian Evolution
• Animals and plants notice that the
environment has changed
• Animals and plants choose to change to
better fit the environment
• WARNING
• There is no evidence for this or
explanation of how this works

10. Darwin

11. Darwin
• If all offspring
reproduced, the
population would grow

12. Darwin
• If all offspring
reproduced, the
population would grow
• Populations stay almost
constant

13. Darwin
• If all offspring
reproduced, the
population would grow
• Populations stay almost
constant
• Resources such as food,
space and breeding
partners are limited

14. • There is a struggle for survival

16. • Individuals in a population vary significantly
from one another

17. • Individuals in a population vary significantly
from one another
• Most of this variation is inherited

19. • Individuals less suited to the environment
are less likely to survive and less likely to
reproduce;

20. • Individuals less suited to the environment
are less likely to survive and less likely to
reproduce;
• Individuals more suited to the environment
are more likely to survive and more likely
to reproduce and leave their inheritable
traits to future generations

22. • This slow process results in populations
changing to adapt to their environments,
and these variations add up over time to
form new species

23. Fossil Evidence

24. Fossil Evidence
• Fossils are when a dead
animal or plant is buried
in mud and over time
turned into rock

25. Fossil Evidence
• Fossils are when a dead
animal or plant is buried
in mud and over time
turned into rock
• Fossils have been found
of animals and plants
which are extinct

26. Fossil Evidence
• Fossils are when a dead
animal or plant is buried
in mud and over time
turned into rock
• Fossils have been found
of animals and plants
which are extinct
• Fossils give us an idea of
how animals and plants
looked in the past (and
in many cases they are
different now)

27. Horses

28. Horses
• The evolution of the
horse was not in a
“straight line” from
Eohippus to what we
know now

29. Horses
• The evolution of the
horse was not in a
“straight line” from
Eohippus to what we
know now
• There were many
“branches” in the family
tree

30. Horses
• The evolution of the
horse was not in a
“straight line” from
Eohippus to what we
know now
• There were many
“branches” in the family
tree
• The other species were
not adapted to their
environment and so they
became extinct

31. Bacteria

32. Bacteria
• Bacteria reproduce very quickly

33. Bacteria
• Bacteria reproduce very quickly
• Bacteria are killed by antibiotics

34. Bacteria
• Bacteria reproduce very quickly
• Bacteria are killed by antibiotics
• If a bacterium survives then its
offspring will also survive the
same antibiotics

35. Bacteria
• Bacteria reproduce very quickly
• Bacteria are killed by antibiotics
• If a bacterium survives then its
offspring will also survive the
same antibiotics
• The only bacteria left are not
killed by antibiotics

36. Bacteria
• Bacteria reproduce very quickly
• Bacteria are killed by antibiotics
• If a bacterium survives then its
offspring will also survive the
same antibiotics
• The only bacteria left are not
killed by antibiotics
• Bacteria become “resistant” to
antibiotics

37. Questions
• What does “adaptation” mean?
• What does “competition” mean?
• What factors prevent offspring from
surviving to the next generation?
• How do animals and plants “adapt” to their
environment?

38. Homework
• Biology For Mon 17th May
• Write 200 words about how to prevent
bacteria from becoming resistant to
antibiotics
• (Useful Google search terms: MRSA, C
difficile, antibiotic resistance, hospitals)