Question

Reproductive System

1.Name three major forms of asexual reproduction.What are advantages? Disadvantages?

2.What are the advantages of sexual reproduction?

3.Explain why reproduction is an important mechanism of evolution. Describe at least two different reproductive strategies that increase evolutionary fitness in animals.

4.How will reproductive strategies differ in water versus terrestrial environments?

5.What does leopard slug sex have that mammalian sex lacks (aside from twirling mucusy elegance)?

Answer 1

1. The three major forms of asexual reproduction are:

Binary Fission:

• It takes place in Single Celled Organisms.
• Exact copy of DNA.
• The daughter cell produced will be Identical to Parent.

Example: Bacteria

Budding:

• Organism has an offspring grow off of the parent.

Example: Hydra

Fragmentation:

• In this mode the parent breaks into and forms two organisms.

Example: Mold and Yeast.

Some advantages of asexual reproduction are:

• A fast Reproduction,
• Requires no mate,
• Only 1 parent needed

Some disadvantages of asexual reproduction are:

• They can not adapt to change,
• The daughters will have no genetic diversity,
• Daughter's DNA is exactly the same as parent.

2.Sexual reproduction is the mode of reproduction in which two individuals are involved and an offspring is produced through the fusion of a male and female gamete. The advantages of sexual reproduction are as follows:

• There will be Genetic Diversity in the offspring.
• The species will be able to adapt to new environments and change in environmental conditions due to the genetic variation.
• Genes keep on changing each generation.
• A disease is less likely to affect all the individuals in a population.
• They have a survival advantage over asexually reproduced individuals.

3 Reproduction is an important mechanism of evolution because of the following reasons:

A genetic variation is created by sexual means of reproduction. Sexual reproduction combines the genetic material of two individuals. An important source of genetic variation in this means of reproduction is that the egg cell and sperm combined has a genetically unique set of genes because both are formed as a result of meiosis.

Different strategies that increase evolutionary fitness in animals are:

Sexual dimorphism- In this strategy the two sexes seem to show several characters other than just sexual organ differences.Their size,shape,colour,etc could also be different.Humans show about 15% sexual dimorphism between male and female of the species.

External and Internal fertilisation- In this strategy the individuals fertilize their gametes either internally or externally. In internal fertilization, the organism only need to produce less number of gametes for a successful fertilization. But the number of offsprings produced will be less than the externally fertilized. The development of the offspring mostly takes place inside the organism which provides for the higher chances of the survival of the offspring. External fertilization requires more number of gametes and a water body in most cases to allow for the favourable environment. The offsprings produced will have less chances of survival than the internally produced but the number of offspings thus produced will be high. There is no requirement of hormones or mating rituals.

4.The contrasting environmental conditions between aquatic and terrestrial realms may play a major role in the differing reproductive strategies found in them.

Compared to the terrestrial realm, aquatic organisms show prevalence of external fertilisation in the ocean.Both viscosity and nutrient concentration are higher in seawater than in air allowing propagules to remain suspended for long periods of time. But this increases the chances of the propagules to get predated easily and low establishment probability and high early mortality. To make up for these shortfalls aquatic lifeforms have increased number of propagules produced and frequently resulting in highly reproductive life histories. In contrast, most terrestrial animals retain female gametes on or in their bodies, and fertilisation and early development are usually internal resulting in less reproductive strategies.Exceptions are seen such as in some sharks or marine mammals.

A greater diversity of life history strategies were found on land compared to aquatic environments. Adaptations like plant vascularity, and animal terrestrial mobility were key for the proliferation of populations and species diversification.Terrestrial animals compensated environmental uncertainties through the evolution of complex behaviours (e.g. societies, nesting) and physiological adaptations (e.g.thermoregulation, internal fecundation) while the plants show slower strategies than aquatic species.Slow life history strategies can buffer environmental variation compensating the uncertainties of reproductive success through high adult survival.

5. Aside from twirling mucusy elegance which is not found in mammalian sex, the leopard slug sex involves their large penises from openings in their heads.These appendages, which are the length of the slugs’ entire bodies, are often coloured blueish by the slugs’ body fluids. Sexual encounters in the slugs are relatively rare: they can fertilise their own eggs, so some individuals never mate. And those that do need only to mate once in their lives. The slugs are hermaphrodites thus they can partner with any other leopard slug they meet. They are known for their colourful upside-down reproductive acrobatics sex performed mostly after dark.Twisting their slimy bodies together, the large slugs dangle upside down from a glittering rope of mucus, slowly rotating.