43.1 Reproduction Methods

43.1 Reproduction Methods

  • By the end of this section, you will be able to discuss advantages and disadvantages of asexual and sexual reproduction.
    • There are advantages and disadvantages to both methods.
    • Large numbers of offspring can be produced quickly and a single individual can produce offspring asexually.
    • Asexual reproduction is an effective means of reproduction in a stable environment because all the offspring will be adapted to that environment.
    • All the offspring are genetically identical and may not have the genetic variation to survive in new or different environments.
    • The rapid rates of asexual reproduction may allow for a quick response to environmental changes.
    • When an individual does not need a mate to reproduce, colonization of new habitats may be easier.
  • The genetic diversity of sexually produced offspring is thought to give species a better chance of surviving in an unpredictable or changing environment.
    • The ability to colonize new habitats can be limited by the fact that both sexes must be present, as species that reproduce sexually must maintain two different types of individuals.
  • Asexual reproduction can occur in some single-celled and multi-celled organisms.
    • There are many ways in which animals reproduce.
  • An organisms splits into two separate organisms after a period of growth.
    • Some unicellular organisms go through a process called mitosis.
    • A second individual is formed in other organisms.
    • In many asteroid echinoderms, this process occurs when the central disk is split.
    • The sea anemones and coral polyps reproduce through fission.
  • Coral polyps reproduce asexually.
  • Some animals that experience Budding are corals and hydras.
  • There is a video of a hydra budding.
  • A separate individual will regrowth if the animal is capable of being splintered.
  • In many sea stars, asexual reproduction is accomplished by fragmenting.
    • Sea stars can be killed by cutting them in half and throwing them back into the ocean.
    • The workers will be preyed upon by twice as many sea stars as the oysters and clams because the two parts can each regenerate a new half.
  • Turbellarians, annelid worms, and poriferans all suffer from degradation.
  • Sea stars can reproduce.
    • A fragment from a sea star is developing into a new person.
  • There is a noticeable difference in the size of the individuals in both fragmentation and fission.
  • Depending on the process and the species, the resulting offspring can be either haploid or diploid.
    • Water fleas, rotifers, aphids, stick insects, some ants, and bees are parthenogenesis.
    • haploid males are produced by bees using parthenogenesis.
    • If eggs are fertilized and fed a special diet, diploid females will develop and a queen will be produced.
  • Some animals reproduce through parthenogenesis.
    • Parthenogenesis has been observed in animal species that were separated by sex in zoos.
    • Two female Komodo dragons, a hammerhead shark, and a blacktop shark have produced parthenogenic young when the females have been isolated from males.
  • Sexual reproduction is the combination of haploid reproductive cells from two individuals to form a third child.
    • The offspring of sexual reproduction have novel combinations of genes.
    • In unpredictable environments, this can be an advantage.
    • As humans, we are used to thinking of animals as having two genders--male and female.
    • There are many variations on this theme in the animal kingdom.
  • They can self-fertilize or mate with another species and produce offspring.
    • Barnacles and clams are examples of animals that have self fertilization.
  • Many animals are hermaphrodites.
    • Up to one hundred eggs can be produced when two individuals mate.
    • Sex determination is determined by the presence of X and Y chromosomes.
    • There are two types of individuals who are male and female.
    • The Y chromosomes cause the development of male and female characteristics.
    • Some insects and plants have the XY system.
  • The presence of Z and W chromosomes can affect the sex determination of a bird.
    • In mammals, the W is important in determining the sex of the individual.
    • This system is used by fish, crustaceans, insects, and reptiles.
  • The sex of some species is determined by the environment.
    • Sex determination in some crocodiles and turtles is dependent on the temperature during critical periods of egg development.
    • This is referred to as temperature dependent sex determination.
    • Males and females can be produced in turtles by cooler temperatures and warm temperatures.
    • Moderate temperatures produce males and both warm and cool temperatures produce females in crocodiles.