Biology – Lecture 57

1. Biology – Lecture 57 Intro to Evolution - Selective Breeding

2. Desirable Traits • In various environments, certain traits help keep organisms alive. • Those desirable traits are passed on to the next generation to help with survival rates of a species.

3. Example – Darwin’s Finches • Darwin's finches are a group of about 15 species of birds. • They were collected by Charles Darwin on the Galápagos Islands.

4. What about the Finches? • The differences between species are in the size and shape of their beaks • Both sizes of beaks are highly adapted to different food sources.

5. Darwin’s Theory • These birds played an important part in the inception of Darwin's theory of evolution by natural selection. • Darwin’s idea was to reject the idea of transmutation of species and focus on "centres of creation".

6. Darwin’s Finches from the Galapagos Islands • His finches were so specific in size and beak shape that they formed an entirely new group of finches consisting of 12 species.

7. Darwin’s Finches • His finches had specific adaptations based on the island that he found them on.

8. Specific Example of Finches • These birds, like all well-studied groups,show various kinds of morphism • Males are dimorphic in beak type, some are short and some are long. This is a clear difference. • With different beaks males are able to feed differently on their favorite cactus, the prickly pear Opuntia. • Those with long beaks are able to punch holes in the cactus fruit and eat the fleshy aril pulp which surrounds the seeds, whereas those with shorter beaks tear apart the cactus base and eat the pulp and any insect larvae and pupae. • This dimorphism maximises their feeding opportunities during the non-breeding season when food is scarce. • The selection maintaining the polymorphism maximises the species' niche by expanding its feeding opportunity.

9. Genetics of Darwin’s Finches • Darwin’s Finches underwent “selective breeding” to produce a highly sought characteristic that allowed for survival of the species.

10. Selective Breeding • Selective breeding is the process used by domestic breeders to improve the characteristics of their population.

11. How Does Selective Breeding Work? • A good breeder will only allow specimens with the most desirable outward characteristics to reproduce.

12. Why Use Selective Breeding? • The favorable characteristics are preserved and the less favorable characteristics become less prominent in the population.

13. Selective Breeding • Selective breeding provides evidence of genetic inheritance between parent and offspring. • Darwin knew nothing of genetics; he just watched the patterns of the offspring.

14. Changing the Species • Selective Breeding over a long period, when breeding out undesirable characteristics, it is possible to change the species entirely.

15. Breeding Out • Breeding Out a gene means not allowing any of those species that exhibit characteristics of the gene to reproduce.

16. Example of Selective Breeding • Using the Punnett Square to look at genetics: • Breed a generation of only tall plants.

17. Example 2 – Selective Breeding • Breed only birds with long beaks. Long beaks are recessive. Start with one of each (homozygous).

18. Example 3 – Selective Breeding • Breed out hemophilia. (Remember hemophilia is an x-linked recessive gene). Start with a man with hemophilia and a woman without it.

19. Practice 1 – Selective Breeding • Breed only dogs with straight hair (wavy hair is co-dominant with straight hair). Start with straight and wavy haired dogs.

20. Practice 2 – Selective Breeding • Breed out bow legged dogs. Normal legged dogs is dominant. Start with one of each (homozygous).