Question

Which of the following is correct about reproduction in Arthropods? (a) Usually dioecious, mostly oviparous (b) Internal fertilization (c) Some exhibit parthenogenesis (d) All of these

Short answer

The correct answer is (d) All of these. All the given statements are true about reproduction in Arthropods.

Step-by-step solution

Understand Key Terms

Firstly, let's define some terms. 1. Dioecious: In dioecious species, an individual is either male or female. 2. Oviparous: Oviparous animals are those that lay eggs, with little or no other embryonic development within the mother. 3. Internal fertilization: This is the union of an egg and sperm during sexual reproduction, inside the female body. 4. Parthenogenesis: This is a form of asexual reproduction. In this the females produce offspring from unfertilized eggs.

Analyze Each Statement

Now, we review each option. 1. Option (a): 'Usually dioecious, mostly oviparous'. This is true for Arthropods. Most arthropods have separate sexes (dioecious) and many reproduce by laying eggs (oviparous). 2. Option (b): 'Internal fertilization'. This is also true for many Arthropods. For instance, in insects, which are a type of arthropod, the sperm is transferred to the female during mating, fertilizing her eggs inside her body. 3. Option (c): 'Some exhibit parthenogenesis'. True again. Some arthropods, such as certain species of bees and aphids, can reproduce asexually via parthenogenesis.

Make a Conclusion

Given the fact that all three statements are correct about reproduction in arthropods, we can arrive at the conclusion that the fourth option (d) 'All of these' is correct.

Key concepts

Dioecious Species

The term 'dioecious' comes from the Greek words 'di', meaning two, and 'oikos', meaning house. In biology, this term refers to a species where individuals are distinctly male or female. Each sex has its own reproductive organs and performs a separate role in the process of producing new life.

For example, male arthropods typically produce sperm while female arthropods produce eggs. In these species, sexual reproduction requires a male and female to mate. This ensures genetic diversity through the combination of genetic material from two different individuals. This separation of sexes is widespread among various groups of arthropods, including insects, crustaceans, and arachnids.

Understanding the concept of dioecious species is crucial because it emphasizes the need for males and females to come together for successful reproduction, ensuring the continuation of the species.

Oviparous Animals

Oviparity is one of the methods by which animals bring new life into the world. Oviparous animals lay eggs that hatch outside of the mother's body. The term originates from the Latin 'ovi' for egg and 'parere', to bring forth.

This approach to reproduction is common among arthropods. After internal or external fertilization, the female lays the eggs in a suitable environment where embryonic development will take place. The eggs may be laid in water, buried in soil, attached to plants, or in other secure locations that provide protection and the required conditions for the embryos to develop.

In some cases, arthropod mothers may provide care for the eggs by guarding them or ensuring they are in a temperature-controlled environment. This protective behavior maximizes the chances of survival for the offspring.

Internal Fertilization

Internal fertilization is characterized by the union of sperm and egg within the female's body. It's an intimate process that ensures the gametes meet in a protected environment, thus enhancing the likelihood of successful fertilization and subsequent development of the embryo.

In many arthropods, this method of fertilization is adapted to their terrestrial lifestyles, which makes the unprotected aquatic stages of their life cycles less feasible. As a result, arthropods have evolved specialized reproductive structures, such as spermatophores in many arachnids or the spermatheca in insects, to store and protect sperm until the eggs are ready to be fertilized.

When the conditions are right, the previously stored sperm can fertilize the egg. This adaptation also allows for sexual reproduction to occur at a time that is most favorable for the survival of the offspring.

Parthenogenesis

Parthenogenesis is a fascinating form of asexual reproduction where females produce offspring without the need for fertilization by a male. The word comes from Greek, with 'parthenos' meaning virgin and 'genesis' meaning creation.

In arthropods, parthenogenesis can be an adaptive response to certain environmental pressures. For instance, when males are scarce or conditions do not favor sexual reproduction, females of some species may reproduce parthenogenetically. This form of reproduction ensures that a species can continue to survive and propagate even in the absence of males.

Some species of bees, wasps, and aphids are known to use this reproductive strategy regularly. In these cases, the offspring are typically genetically identical to the mother, leading to a clone-like reproduction which, while lacking genetic diversity, provides a rapid way to increase population size in stable environmental conditions.