ASP136 Flashcards
Define asexual reproduction
The copying and proliferation of an organisms own genetic material. This DOESN’T involve the fusion of gametes.
Suggest advantages of asexual reproduction.
- It is simple and fast, because it only involves the participation of one organism; the parent organism.
- It involves less wastage of genetic material. As many sperm are lost during sexual reproduction as only one is required to fertilize the egg.
- Reproduction is always guaranteed.
What is Successful Fertilization?
When an intact single parental genome is passed on to the progeny.
Name 3 organisms which reproduce asexually.
- Sponges
- Cnidaria
- Plathyhelminthes
How are males produced from asexual reproduction?
One chromosome is randomly inactivated (XX = Females) (XO = Males)
Name two ways an organism reproduces asexually
Fragmentation/Regeneration and Budding.
What factor limits whether an organism is generated through fragmentation?
The size of the fragment which was cut off the parent organism.
What is Binary Fission and in what organisms does it occur?
When an individual organism duplicates its genetic material and splits into two, generating two daughter organisms of the same size. This commonly occurs in Prokaryotes and some single celled Eukaryotes.
Describe the process of fragmentation/regeneration
Fragmentation is the process by which a body part of the parent organism is removed. Each individual fragment then has the potential to generate an adult however this is limited by the size of the fragement initially cut off. Regeneration follows fragmentation as the body part removed from the parent grows back.
Describe the process of budding.
Budding is the process by which and organism grows out of the body of the parent. This occurs as a specialized mass of cells develops on the parent organism forming the bud, the offspring then develops from the bud eventually detaching or remaining attached to form aggregates.
What is Parthenogenesis and how does it occur?
The process of reproduction which doesn’t involve fertilization. This occurs as the females have unfertilized eggs that are not haploid thus generate offspring. This occurs as the females DNA is Diploidised (Duplicated) producing a diploid egg.
Why doesn’t Pathenogenesis occur in humans?
Humans have imprinted genes. This follows that humand inherit two copies of a gene (one maternal and one paternal chromosome) and only one is expressed (the working gene). If humans were to reproduce via parthenogensis then we would inherit either two maternal genes or two paternal genes. These may then not be expressed or they may both be expressed, thus causing problems.
What two factors of sexual reproduction allow variation?
Recombination and Segregation.
Gametes are produced by what type of cellular division?
Meiosis.
What 3 phenomena are key for Sexual Reproduction?
Gametogenesis
Mating
Fertilization.
What is more efficient, Internal or External reproduction and why?
Internal reproduction. External reproduction requires the gametes to be transported in a liquid medium, usually water. This gives rise to a variety of transportation difficulties influenced by factors such as Wave motion, Wave speed, predation (as eggs are rich in protein) ect.
What is the difference between indirect and direct internal fertilization?
Indirect fertilization involves the male depositing a sperm packet, called a spermatophore, on the ground for the female to ‘pick up’.
Direct fertilization involves the copulation of the male and female allowing the direct transfer of sperm to the egg, either freely or in a spermatophore.
What is Haemocoelic penetration/Traumatic insemination.
The process by which sperm is injected into the femal abdominal cavity (Haemocoel) to then travel to the reproductive system.
How do octopuses reproduce?
Direct reproduction. The third arm of the octopus is inserted into the female. Sperm then travels along the arm to the tip. The tip breaks off inside the female once the sperm has travelled to the then. The male often cannot survive losing the arm and if it does it is often killed by the female.
How does the Lucerne flea (Sminthorius Viridis) reproduce?
Indirect reproduction. The male deposits a spermatophore on the ground. The spermatophore is a stalk with a liquid packet on the top containing the sperm and some nutritional fluid to prevent desication (drying up). The males then direct the females towards the spermatophore. She then moves back onto it to achieve fertilization.
How do Hermaphrodites reproduce? Specifically Leopard Slugs.
Hermaphrodites are often not self fertilizing, they often exchange sperm with a mate as eggs are too expensive (require a lot of energy to make). They then use the sperm from the mate to fertilize their own eggs.
Why would you see black spots in the reproductive tract of a female Bean Weevil?
The male Bean Weevils have spikes on their penises, as a result the female becomes incredibly damaged during copulation. The black spots are sites of Melanin as insects use melanin to repair wounds. Virgin females dont have these spots.
What is sexually antagonistic co-evolution? Give an example where this is seen.
It is an ‘arms race’ as such between the sexes to ensure maximum frequency of fertilization. It is seen in Bean Weevils as the males damage the female reproductive tract during copulation due to spikes on the penis. This means the female is less likes to reproduce again, therefore the female only uses that one males sperm to fertilize her eggs before she dies. This is described as being sexually antagonistic co-evolution as mating behaviour is detremental to the females fitness, as male fitness increases, female fitness decreases.
What is paternal monopulization and how could it be prevented? give an example.
The black widow spider. After copulation the female black widow spider eats the male (cannibalism). This could be for nourishment to ensure the maximum survival rate for the female and the offspring or it could be to prevent paternal monopulization. This is the process by which many females are injected with the same males sperm thus cannibalism ensures genetic variability in the entire population.
What is sexual reproduction hijacking? give an example where this occurs.
When the sexual reproduction of one species is prevented (hijacked) by that of another. This occurs as a result of the bacterium Wolbacha. Wolbacha kill the males in an infected species or they induce parthenogenisis allowing them to become present in the progeny. These can be treated suing antibiotics as they’re bacteria.
Where does spermatogenesis take place?
Seminiferous tubules
Describe spermatogenesis
Primordial germ cells migrate into the gonad during Embryogenesis. They then differentiate into Spermatogonia. Spermatogonia proliferate by mitosis next to the basement membrane of the stratified epithelium lining the seminiferous tubules. Spermatogonia undergo meiosis 1. In the prophase of meiosis 1, Primary Spermatocytes are produced, here crossing over occurs. Upon completion of meiosis 1 secondary spermatocytes are produced containing a haploid number of duplicated chromosomes. Meiosis 2 then occurs producing early spermatids containing a haploid number of unduplicated chromosomes. These differentiate by Spermiogenesis into mature sperm cells.
What is Spermiogensis
This is the differentiation of the early spermatid into a sperm cell. Here, there is a reduction in the quantity of cytoplasm in the early spermatid and and elongation of the head to form the flagella. The sperm are then released into the lumen where they travel up the Vas deferens into the widened ampulla. The sperm then travel to the seminal vesicles where they’re stored.
