Organismal BiologyReproduction

Reproduction

• Sexual and asexual

Sexual vs. Asexual Reproduction

• Asexual Reproduction: Define• Types: Binary Fission and Budding (mostly

unicellular organisms)• Regeneration and Parthenogenesis

(multicellular animals)• Advantage: Good for widely dispersed

animals (no need to find a mate)Allows for rapid growth in favorable

conditions• Requires much less energy than sexual

reproduction

Sexual vs. Asexual Reproduction

• Sexual Reproduction: Define• Performed by most multicellular

plants and animals• Ensures genetic diversity and

variability through recombination of alleles• Allows species to survive better in a

changing environment

Prokaryote vs. Eukaryotes

Prokaryotes: Binary fission without mitosisDoes cytokinesis still occur?

Prokaryote vs. Eukaryotes

• Besides binary fission, bacteria can also reproduce by transformation (taking in naked, foreign DNA), transduction (new DNA added by a virus), conjugation (exchange of genetic material between bacteria).

Transduction

Conjugation

Prokaryote vs. Eukaryotes

• Eukaryotes: Mitosis occurs with cytokinesis

Asexual Reproduction: Binary Fission

• Parent divides into two equal parts

• The 2 daughter cells are equal in size and grow to normal size

• Ex: ameba and paramecium

Asexual Reproduction: Budding

• The parent cell divides into 2 unequal parts• Yeast (unicellular) - 2 daughter cells are produced - 1 is larger than the other• Hydra (multicellular) - the daughter is a multicellular outgrowth of the parent

An important thing to remember is that there is still an equal division of nuclear material in budding even though the cytoplasm is unequally divided

Yeast and Hydra Budding

This small hydra bud will eventually separate from the parent

Yeast bud

Asexual Reproduction:• Parthenogenesis: Development of an

unfertilized egg

4. Regeneration• The ability of an animal to regrow lost

body parts• Simple organisms: hydra, planaria, earthworm, and

lobster

Regeneration in Planaria

Sexual Reproduction

• Meiosis produces gametes (sperm and egg). Reduces chromosome number by half. Fertilization restores the diploid chromosome number. It allows for recombination of alleles creating more variability and diversity among the offspring.

Hermaphrodites• Organisms that contain both male and female

reproductive organs• Each earthworm below is placing sperm inside

the other

Why is this type of existence beneficial for an organism with a lifestyle like the earthworm?

Earthworms spend most of their time under the ground and are slow moving. This double fertilization ensures enough offspring

Human Reproduction