1. Asexual vs. Sexual Reproduction Disadvantages, Advantages and Types

2. Asexual Reproduction What is it?  production of individuals without gametes  fission or splitting of cell

3. Asexual Advantages Why asexual reproduction? Need one individual to reproduce; can conserve energy No genetic change “good” if environment is stable All individuals are producing offspring More efficient passing genes, “faster”

4. Asexual Disadvantages Why not asexual reproduction? No recombination of genes An asexual population tends to be genetically static  Mutant alleles  Beneficial alleles

5. Types of Asexual Reproduction Unicellular: Fission-splitting into two organisms from one

6. Types of Asexual Reproduction Multicellular organisms: Budding- Offspring develop as a growth on the body of the parent. Ex: hydra, parasites some break away, some form colonies

7. Types of Asexual Reproduction Multicellular organisms continued: Fragmentation- body of the parent breaks into distinct pieces; pieces can produce an offspring. ex) planarians

8. Types of Asexual Reproduction Multicellular organisms continued: Parthenogenesis- ("virgin birth"), the females produce eggs, young develop without being fertilized. Parthenogenesis occurs in some fishes, several kinds of insects, and a few species of frogs and lizards. (not mammals because imprinted genes.)

9. Types of Asexual Reproduction Multicellular organisms continued: Parthenogenesis cont’d- In a few nonmammalian species it is the only method of reproduction. Some animals turn to parthenogenesis only at certain times. APHIDS

10. Sexual Reproduction What is it?  Production of individuals with gametes  Believed it evolved as early as 2.5 to 3.5 billion years ago

11. Advantages of Sexual Reproduction Why sexual reproduction? 1. Offspring are genetically unique from: A. Crossing over B. Independent assortment C. Random fusion of gametes 2. Favorable when the environment is not stable

12. Advantages of Sexual Reproduction Why sexual reproduction? 3. Slower rate of reproduction but faster evolution 4. Lower extinction rates

13. Advantages of Sexual Reproduction Why sexual reproduction continued? 5. Fast removal of bad mutations or can put two beneficial mutations together 6. Better adaptation to host-parasite arms race. 7. Offspring are dispersed widely to end up in different places from their parents

14. Disadvantages of Sexual Reproduction Why not sexual reproduction? 1. Need two parents “must expend energy” to find, identify (court) mate 2. Genetic recombination is counter productive if conditions are stable

15. Disadvantages of Sexual Reproduction 3. Only half the individuals are producing offspring-(Males are an energy issue) 4. Less efficient at passing on genes

16. Disadvantages of Sexual Reproduction 5. “Cost of recombination”-a favorable combination of genes can be broken