Asexual vs. Sexual Reproduction

Asexual vs. Sexual Reproduction

Disadvantages, Advantages

and Types

Asexual ReproductionAsexual Reproduction

• What is it?production of individuals without

gametes

fission or splitting of cell

Asexual AdvantagesAsexual 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”

 

Asexual DisadvantagesAsexual Disadvantages

• Why not asexual reproduction?

• No recombination of genes 

• An asexual population tends to be genetically static

Mutant allelesBeneficial alleles

Types of Asexual ReproductionTypes of Asexual Reproduction

• Unicellular:

 Fission-splitting into two organisms from one

Types of Asexual ReproductionTypes 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

   

Types of Asexual ReproductionTypes of Asexual Reproduction

• Multicellular organisms continued:

Fragmentation- body of the parent breaks into distinct pieces; pieces can

produce an offspring.

ex) planarians

Types of Asexual ReproductionTypes 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.)

Types of Asexual ReproductionTypes 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

Sexual ReproductionSexual Reproduction

• What is it?Production of individuals with gametes

Believed it evolved as early as 2.5 to 3.5 billion years ago

Advantages of Sexual Reproduction

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 

Advantages of Sexual Reproduction

Advantages of Sexual Reproduction

• Why sexual reproduction?

• 3. Slower rate of reproduction but faster evolution

4. Lower extinction rates

Advantages of Sexual Reproduction

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  

Disadvantages of Sexual Reproduction

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   

Disadvantages of Sexual Reproduction

Disadvantages of Sexual Reproduction

 3. Only half the individuals are producing offspring-(Males are an energy issue)

    

4. Less efficient at passing on genes  

Disadvantages of Sexual Reproduction

Disadvantages of Sexual Reproduction

 5. “Cost of recombination”-a favorable combination of genes can be broken