Transcript Organismal Biology: Reproduction

Organismal Biology
Reproduction
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
Yeast bud
This small hydra bud will
eventually separate from
the parent
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