Reproduction Flashcards
(26 cards)
What are the types of asexual reproduction?
- budding
- parthenogenesis
- regeneration
What is regeneration
- Repair of damage to body
- a form of reproduction in some species
- involves mitosis and differentiation
What is budding?
- similar process to regeneration
- occurs without damage
- may give rise to individuals or colonies
What is parthenogenesis?
- development of egg without fertilisation
- new individual may be haploid or diploid
- invertebrates and few vertebrates
What does sexual reproduction involve?
- Gametogenesis - making sex cells/gametes
- spawning or mating
- fertilisation - getting sex cells to fuse
What is gametogenesis?
• germ cells need to proliferate (
finite time for females, indefinite time for males)
• germ cells need to undergo meiosis in order to exchange genetic material and to half their chromosome complement
What are the different stages of a sperm cell during spermatogenesis?
• spermatogonium divides mitotically
• MEIOSIS - prophase; primary spermatocyte
• after 1st division - primary spermatocyte
• secondary spermatocyte
DIFFERENTIATION
• spermatid
• spermatozoa
What is the site of spermatogenesis?
Seminiferous tubules in the testis
Describe the development of oocyets
- oogonia proliferate through mitosis
- but when they enter into primary oocytes they immediately enter prophase 1 of meiosis
- the primary oocyte stays in this phase until the female animal becomes sexually mature
- second meiotic division only occurs after fertilisation
What is the difference between oogonia and oocytes?
Primordial germ cells migrate to the forming gonad and becomes oogonia.
After a period of mitotic proliferation oogonia differentiate into primary oocytes.
What happens in the first division of meiosis?
In the first division, the homologous chromosomes separate into 2 daughter nuclei.
• cytoplasm divides asymmetrically - one is a small polar body and the other is large cell (containing all developmental potential)
What happens in the second division of meiosis?
Two sister chromatids of each chromosome separate to form 2 haploid cells
• once again, the cytoplasm divides asymmetrically to form another small polar body and the mature ovum.
Summarise gametogenesis in males
- each spermatogonium gives rise to four haploid sperm
- mitosis ceases in the embryo
- meiosis begins at puberty through to end of life
Summarise gametogenesis in females
- each oogonium undergoes mitosis forming primary oocytes
- meiosis begins in the embryo but stays in prophase 1 until puberty
- oocyte remains at metaphase 2 until fertilisation occurs where second division occurs
- otherwise ovulation occurs
What does internal and external fertilisation require?
External - aquatic habitat
Internal - mating
What are the 2 categories of animals with internal fertilisation?
Oviparous - egg bearing
viviparous - live bearing
What is oviparous?
- Egg bearing
* development occurs outside the mother’s body
What is viviparous?
- live bearing
* development occurs inside the mother’s body
What specific organelles does the mother and father provide?
- Sperm provides the centriole
* All of the mitochondria provided by the mother
What is an acrosome?
- cap at the front of the sperm that stores protein
* this is the part that first contacts the egg
What is the zona pellucida?
- the thick outer coating covering the egg
* it is a layer of carbohydrate-covered proteins that surrounds the plasma membrane
What is the function of the zona pellucida?
- protects the egg
* responsible for mediating the initial meeting of the sperm and the egg
Where are cortical granules found and what is their function?
- cortical granules are filled with enzyme and line the inside of the cell membrane
- help make sure that only one sperm can fertilise the egg
What are the differences between the egg and the sperm right before fertilisation?
• sperm has completed meiosis
• egg has not completed meiosis - the chromatids are still attached
- once fertilisation has occurred
• size: sperm is 10,000 times bigger than the sperm
