Asexual Reproduction

Conjugation

• Conjugation: Bacteria transmit genetic knowledge to become resilient to environmental conditions.
• Asexual reproduction.
• Antibiotic Resistance:
  • Bacteria can learn to survive antibiotics.
  • After antibiotic treatment, surviving bacteria share knowledge via conjugation.
  • Leads to antibiotic-resistant bacteria like MRSA.
  • Overuse/improper use of antibiotics is a major factor.
  • Complete antibiotic courses to eliminate all bacteria and prevent knowledge sharing of resistance.
• Conjugation meaning: opposing reactions happening at the same time.

Vectors

• Vector: Anything that can be transmitted.
• Examples:
  • Mosquitoes for malaria: They carry and transmit malaria.
  • Rats for the plague: They carry fleas.

Budding

• Budding: Asexual reproduction where a mini version grows out of the parent's body.
• Offshoot stays attached for a period of time.
• Brewer's Yeast (Saccharomyces cerevisiae):
  • One yeast grows an offshoot.
  • Offshoot stays attached and uses parent's resources.
• Hydra (jellyfish phylum):
  • Offspring grows attached to the parent.
  • New offshoots can grow from the offspring.
  • Weight eventually causes the offshoot to tear off from the parent.
  • The parent can heal itself.
  • Hydra grows out of the parent, gets big enough, and tears off.
  • It can cause damage to the parent during the process.
• Hydra example has a budding stage called a polyp.
• Mitosis: Asexual.

Vegetative Reproduction

• Similar to budding because offspring grows out of the parent and stays attached.
• Roots or shoots can grow new, genetically identical plants.
• Mitosis: Genetically identical.
• Tubers (e.g., potatoes):
  • Plant "seed potatoes."
  • Tubers grow underground, connected to the parent plant.
  • Mounding soil helps tuber growth.
• Suckers (e.g., roses, elms, maple trees):
  • Grow out from the parent, emerging from the ground.
  • Cut suckers from trees. Lilacs, roses, etc. create them.
  • Beneficial for gardeners; one plant results in offshoots, creating a rose hedge.
• Raspberry Canes:
  • Canes sucker, with new ones popping up each year.
  • Raspberries spread through the ground and through seed dispersal by birds.
  • Birds eat berries, seeds go through their digestive system, and are deposited elsewhere.
  • Scarification: Seeds require going through a bird's digestive system.
• Runners:
  • Plant produces offspring above ground.
  • Offshoot moves along the ground and sets roots down when far enough from the parent.
  • Fleece flower as an example.
  • Creates a mat of vegetative stems.
• Suckers vs. Runners:
  • Suckers: Offspring comes up out of the ground.
  • Runners: Grow above ground and then set roots down.
  • Most plants grow by suckering.
• Strawberry Plants:
  • Tendrils with strawberries (suckers) hang down from baskets.
• Banyan Trees:
  • Vegetative growth through runners.
  • They're vegetative growth and they are runners.

Fragmentation

• Unlike budding/vegetative reproduction, a section of the parent is cut off and becomes a new organism.
• Flatworms and starfish can do this.
• Gardeners use it with yarrow plants.
• A section of the parent is moved elsewhere and completes the process through mitosis, eventually becoming a new organism.
• Differs from budding because there is no attachment.
• Totipotent Cells:
  • Unspecialized, undifferentiated cells that can build an entire new organism.
  • Fragmentation, budding, and vegetative reproduction rely on totipotent cells.
  • Example: cutting up flatworms or earthworms.
  • Earthworms: Head gets middle and tail, tail gets head and middle, middle gets both.
  • Totipotent cells are a type of stem cell with the ability to grow into whole new organisms.

Parthenogenesis

• Asexual reproduction where an unfertilized egg develops into an adult.
• Does not happen in the human body.
• Seen naturally in some plants and invertebrate species.
• Honeybees:
  • Unfertilized egg (haploid) becomes a male bee (drone).
  • Fertilized egg (diploid) becomes a female bee (queen or worker).
• New Mexico Whiptail Lizard:
  • Hybridization produces only females.
  • Eggs have biochemical mechanisms that prevent male formation.
• Process: *Model depicting parthenogenesis:
  • Female with the chromosomes ZW for snakes.
  • Egg (ZW) goes through meiosis.
  • Splits into one cell that turns into an egg which gets the Z chromosome and the other cell divides further.
  • During the second round of division, Z become two Zs and W become two Ws.
  • Polar bodies, Z cells self fertilize and ends up being a zygote and embryo that is ZZ which means that all the offspring are males.
  • Humans would be XX. The X polar body self fertilizes and leads the offspring to ONLY be chromosomally female.
  • It can happen randomly and lead to immaculate conception.
• The offspring is not genetically identical to the mother.
• Meiosis, but with independent assortment crossing over and genetic recombination, occurs. Parthenogenesis gives us biodiversity.
• Give freedom from the perspective if you can fertilize yourself, then you don't need to have a partner.
• Stingray fish can undergo parthenogenesis.
• Discovered two years ago. The first time in The United States.
• Limits the gender.

Alternation of Generation

• Alternating between being in a diploid and being in a haploid form.
• Not sex vs asex, not mitosis vs meiosis, but haploid vs diploid.
• Spores: Plants and fungi (e.g., dandelions).
  • Spores are very fast spreading, they spread with wind and they just move exactly.
  • Spores in themselves are haploid and unicellular.
• Alternation between two forms: diploid (sporophyte - 2n) and haploid (gametophyte - n).
• Two gametophytes fuse to make a sporophyte.
• Life Cycle Diagram: *The steps to identify in the diagram are fertilization, the haploid,the diploid structures, where is mitosis and where is meiosis.
  • Find the zygote first.
  • The process just before the zygote is always fertilization.
  • Fertilization means two gametes are coming together.
  • Gametes are haploid.
  • Haploid means originally we had to go through meiosis.
  • Zygote grows and undergoes Mitosis, with each of its cells being diploid.
  • Everything over here is diploid.
  • Sporophyte is diploid, gametophyte is haploid.
  • Sporophyte goes through meiosis and produces spores.
  • Spores automatically are haploid.
  • Spores mature into a gametophyte which then leads to the zygote.
  • Maturing means that we have to go through mitosis, not meiosis.
• Plants are weird. So let's think about this. If you're haploid, can you undergo reductive division? No.
  Not always. It had to undergo mitosis.