KM

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.