28. Reproduction Flashcards
What are the advantages of asexual reproduction?
Reproduce without a partner so no need to use energy or resources to find a mate
What are the disadvantages of asexual reproduction?
No genetic diversity in the population
What is parthenogenesis?
- Development of the egg without fertilisation
- New individual may be haploid or diploid
What species undergo parthenogenesis?
Invertebrates and a few vertebrates
What are the three broad stages of sexual reproduction?
- Gametogenesis (making sex cells)
- Spawning or mating (getting sex cell together)
- Fertilisation (getting sex cells to fuse)
How many nuclear divisions are there in meiosis?
- Meiosis consists of 2 nuclear divisions that decrease the number of chromosomes to the haploid number
- Nucleus divides twice but the DNA is replicated only once
Difference between meiosis and mitosis in terms of homologous pairing?
- Homologous chromosomes pair along their entire length
- No pairing of homologise in mitosis
What are the 4 parts of the sperm?
- Acrosome
- Nucleus
- Midpiece
- Tail
What is the acrosome of the sperm?
Contains enzymes to help penetrate the ovum
What is the midpiece of the sperm?
Contains mitochondria for energy
What is the tail of a sperm?
The flagellum is for movement
What are the cells produced in spermatogenesis?
- Male germ cell (2n)
- Spermatogonium (2n) (stem cells)
- Primary spermatocyte (2n)
First meiosis division
- Secondary spermatocytes (n)
- Spermatids (n)
Spermatozoa
What is the site of spermatogenesis?
Semiferous tubules
How are oocytes formed?
- Oogonia proliferate through mitosis
- But when they enter into primary oocytes they immediately enter prophase of meiosis 1 and stay in this state for years
- Known as Germinal Vesicle (GV) stage
What cells are formed in the female embryo in oogenesis?
Mitosis gives an oogonia
Meiosis 1 is arrested - primary oocytes in GV stage
What divisions to produce the oocytes occur in the adult?
Meiosis 2 gives the secondary oocytes (first polar body) and then meiosis 2 is arrested
What divisions occur during fertilisation to produce the oocyte?
Meiosis is complete when the egg is fertilised and it has the polar bodies
What is the difference in males and females in terms of location of gametogenesis?
- Mitosis ceases in the embryo for males
- Meiosis begins in the embryo and meiosis 1 is arrested around birth for females
What is the difference between males and females in terms of what each gametogenesis gives?
- In males each spermatogonium gives rise to four haploid sperm
- In females each oogonim gives rise to one haploid egg and 2 polar bodies
What is the primordial follicle?
Present in the ovary from birth, located in the stroma of the ovary cortex behind the tunica albuginea
The primordial follicle is the oocyte and the surrounding follicular cells
What is the primordial germ cell?
Oocyte present in the primordial follicle ovary from birth
What is the primary follicle?
Single layer of follicle cells, presence of zona pellucida
What is the secondary follicle?
Two or more layers of follicle cells
What is the antral (graafian) follicle?
Early or late - presence of cavity and multiple layers of cells
