Post on 30-Dec-2015
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 mitosis
Does 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 parentYeast 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