Asexual vs. Sexual Reproduction

Two basic reproductive modes• Asexual reproduction - Requires only one parent - Offspring are genetically identical to parent and each other due to mitosis.• Sexual reproduction - Requires meiotic cell division in two parents. - Produces genetically variable offspring

with different combinations of parental genes

.

Asexual reproduction is the primary form of reproduction for single-celled organisms such as archaea, bacteria, and protists.

Many plants and fungi reproduce asexually as well.

Types of asexual reproduction • Binary fission• Budding • Vegetative reproduction• Regeneration • Parthenogenesis

Budding

• Miniature animal begins as a bud on the

adult and becomes independent.

Binary fission

• Cell splits and replicated DNA goes with each part

• Prokaryotes and Bacteria

• + Fast and easy• - Everybody has

the same DNA

Asexual reproduction by regeneration in flatworms

Parthenogenesis

• In some insects, fish, amphibians and reptiles the eggs produced by females develop directly into adults without being fertilized by sperm.

Asexual Reproduction - Advantages

• Rapid population growth• Requires less energy to reproduce• All organisms are able to reproduce

as opposed to just a female population• Only one organism may begin an

entire population• Less likely to become extinct• An exact replica of the parent

Cloning in large numbers

In Asexual reproduction, offspring are typically genetically similar to their parent.

• The lack of genetic recombination results in fewer genetic alternatives than with sexual reproduction.

• Many forms of asexual reproduction, for example budding or fragmentation, produce an exact replica of the parent.

Asexual reproduction disadvantages

• Asexual reproduction is inferior because it stifles the potential for change.

• There is also a significantly reduced chance of mutation or other complications that can result from the mixing of genes .

Sexual reproduction in animals

• Requires the production of gametes (egg and sperm), which are haploid cells .

• Gametes are produced from diploid cells by meiosis.

• Fusion of egg and sperm (fertilization) produces a diploid zygote, which divides into new diploid animal.

Sexual reproduction requires fusion of sperm & egg

Fusion of gametes in plants

Sexual Reproduction Advantages

• Allows for more diversity among a species

• Higher probability of mutation and survival

in periods of change

Advantages of sexual reproduction

• Offers the opportunity to produce different combinations that can make the population better able to keep up with changes in the environment.

• Species with recombination can bunch harmful mutations together and eliminate several in a single "genetic death.“

Sexual reproduction disadvantages

•Two parents are required•Increased likely hood of something going wrong•A much more complicated and lengthy process.

A lineage that reproduces sexually has a higher probability of having more members survive due to the genetic recombination that produces a novel genotype through adaptations.

Interesting examples Anemone fishes are characterized by being protandrous hermaphrodites which means that all fish develop into males first and then potentially into females later. More than one anemone fish may reside in the same anemone, however if the female were to be removed from the group or die, the largest male would then become female. Females control males through aggressive dominance, thereby controlling the formation of other females.

• Some species alternate between sexual and asexual reproduction, an ability known as heterogamy, depending on conditions.

• Examples- Freshwater crustacean Daphnia reproduces by parthenogenesis in the spring to rapidly populate ponds, then switches to sexual reproduction as the intensity of competition increases.

• Many protists and fungi also alternate between sexual and asexual reproduction.