1. When the egg is large and nonmotile, the sperm is small, motile, and contains
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Question
1. When the egg is large and nonmotile, the sperm is small, motile, and contains only genetic material, this is called _ (blank) _
2. Which seems to be the ancestral form? Why?
3. Is there a correlation between gamete size and quantity produced? Why?
4. Discuss the challenges of aquatic organisms when it comes to sexual reproduction. Why would it be advantageous to retain the ability for asexual propagation?
5. What is parthenogenesis? Explain the pros and cons of this form of asexual reproduction.
6. Compare and contrast the challenges of fertilization in aquatic vs. terrestrial environments.
7. As animals became increasingly complex, embryos required more “help” to support them through development. Explain the roles of the different extraembryonic membranes and why they are necessary to the embryo.
8. Simple animals (jellyfish, planaria, etc) have simple “embryos” that are free-living. How does an aquatic environment meet the needs of these embryos/larvae in place of extraembryonic membranes?
Explanation / Answer
Answer 1. Oogamy
Oogamy is a form of physiological anisogamy, where the female is large and non-motile whereas the male is motile and small in size. It is the most recent form of gamete structure. Human beings also show this phenomena, because ovum is non-motile thus, always sperm has to come close to the it for fertilisation and propagation of the race.
Answer 2. The primitive gametes were isogamous in nature, means both the gametes were similar in size and with flagella. Later, anisogamy and oogamy became more prevalent, because of their benefits. Thus, sperms seems to be more primitive in relation to the ovum. Ovum has developed larger size to acuumulate large amount of cytoplasm, which could be helpful to the growing embryo because it will help in providing nutrition in the early stages.
Answer 3. Yes, there is a correlation between the gamete size and the quantity produced. As sperms are smaller in size, they will acquire small space for themselves, so at a point of time their quantity will be high because if their reduced size. Whereas, the ovum is bigger in size, thus they require more space for themselves and a result their number will be limited in the ovary. Because of smaller size of sperms there number is always more in the testes in comparison to ovum in the ovary.
Answer 4. Sexual reproduction requires the formation of gametes. Aquatic organisms release a number of gametes in the water for external fertilisation. The release of eggs into the water in case of fishes is known as spawning. The probability of fertilisation is quite less because of the number of predators in the water resource. Thus, an aquatic animal has to produce large number of gametes for successful fertilisation.,which is a challenge for aquatic animal. In place of it, asexual reproduction is far more beneficial for the aquatic animals to sustain their race. Clones formed by asexual reproduction have better survival chances and are identical to the parents.
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