IB Biology Evolution - Earland

2,436 views
2,145 views

Published on

Published in: Education, Technology
0 Comments
2 Likes
Statistics
Notes
  • Be the first to comment

No Downloads
Views
Total views
2,436
On SlideShare
0
From Embeds
0
Number of Embeds
8
Actions
Shares
0
Downloads
118
Comments
0
Likes
2
Embeds 0
No embeds

No notes for slide

IB Biology Evolution - Earland

  1. 1. Evolution IB Biology Topic 5.4
  2. 11. Analogous Structures are features of different species that are similar in function but not necessarily in structure and which do not derive from a common ancestral feature (compare to homologous structures) and which evolved in response to a similar environmental challenge. Example: Insects and birds both have wings to fly, although their wing structure is very different this is an example of an analogous structure. The fat-insulated, streamlines shapes of seals (mammals) and of penguins (birds) is another example.
  3. 13. 5.4.4 Population size and survival <ul><li>  It should be noted that the 'struggle for survival' in this model is a consequence of over-population . </li></ul><ul><li>The struggle takes the form of individuals in the population being 'selected for ' or 'selected against ' . </li></ul><ul><li>Survivors form the new breeding population . </li></ul><ul><li>The frequency of advantageous alleles has increased. </li></ul><ul><li>The change in the heritable characteristics is by definition evolution .   </li></ul>
  4. 14. 5.4.5 Variation in a species. <ul><li>Individuals in a species are not all identical, but show variations in their characteristics </li></ul>
  5. 15. 5.4.6 Sexual reproduction and variation <ul><li>The sources of genetic variation in a populations : </li></ul><ul><ul><li>Meiosis and the independent assortment of chromosomes creates 2 n new combinations of chromosome in the next generation n = haploid number of chromosomes </li></ul></ul><ul><ul><li>Random fertilisation increases the variation in the population to 2 2n again where n = haploid number of chromosomes </li></ul></ul><ul><ul><li>The number of different genetic variations is increased further by cross-over in meiosis by an estimated 2 3 in addition to the two above. </li></ul></ul>

×