bzyet-143-solved-assignment-2024-ss-020cab3d-1c01-486f-9bdf-7506d86b97ee

1. i) Give two examples of insects for each of the following types of metamorphosis:
   a) No metamorphosis:
   b) Incomplete metamorphosis:
   c) Complete metamorphosis:

• Insects in this category do not undergo significant changes in body form as they develop from nymphs to adults. They simply grow larger.
• Examples:
  1. Silverfish (Lepisma saccharina): These primitive insects have a carrot-shaped body and are commonly found in damp, dark areas.
  2. Bristletails (Order: Archaeognatha): These are small, wingless insects with elongated bodies and three long tail filaments.

• Insects with incomplete metamorphosis undergo three life stages: egg, nymph, and adult. The nymphs resemble the adults but lack fully developed wings and reproductive structures.
• Examples:
  1. Grasshoppers (Order: Orthoptera): Grasshopper nymphs look like miniature adults and gradually develop wings as they molt.
  2. Cockroaches (Order: Blattodea): Cockroach nymphs are wingless and smaller than adults but share a similar body shape.

• Insects with complete metamorphosis undergo four distinct life stages: egg, larva, pupa, and adult. The larval stage looks entirely different from the adult, and the transformation occurs during the pupal stage.
• Examples:
  1. Butterflies (Order: Lepidoptera): Butterfly larvae are caterpillars that feed and grow before entering the pupal stage (chrysalis) and emerging as winged adults.
  2. Beetles (Order: Coleoptera): Beetle larvae, often called grubs, undergo metamorphosis inside a pupal case and emerge as adult beetles with hardened exoskeletons and wings.

• Egg: Silverfish lay eggs in crevices or hidden areas. The eggs are oval-shaped and whitish.
• Nymph (Young): After hatching, silverfish emerge as nymphs, which resemble smaller versions of the adults. They lack scales, which develop as they mature.
• Adult: Nymphs molt several times as they grow, eventually becoming adults with silvery scales and a tapered, carrot-shaped body. Silverfish continue to molt throughout their lives, even after reaching adulthood.

• Egg: Grasshoppers lay eggs in the soil or plant tissue. The eggs are typically laid in clusters called pods.
• Nymph (Young): After hatching, grasshoppers emerge as nymphs, which look like small, wingless versions of the adults. Nymphs go through several instars (developmental stages between molts), during which they grow larger and gradually develop wing buds.
• Adult: After the final molt, the nymphs transform into adults with fully developed wings and reproductive organs. Adult grasshoppers are capable of flight and reproduction.

2. a) Differentiate between:
   i) Propagative Transmission and Cyclopropagative Transmission
   ii) Cyclodevelopmental Transmission and Vertical Transmission

• Propagative Transmission: In this type of transmission, the pathogen multiplies within the vector without undergoing any developmental changes. The vector acquires the pathogen, which then propagates (increases in number) within the vector before being transmitted to the next host. This is common in viral transmissions, such as the transmission of the West Nile virus by mosquitoes.
• Cyclopropagative Transmission: This involves both multiplication and development of the pathogen within the vector. The pathogen undergoes a cycle of changes, including both propagation and morphological or physiological development, before it becomes infective to the next host. An example is the transmission of malaria parasites (Plasmodium spp.) by Anopheles mosquitoes, where the parasites undergo asexual multiplication and sexual development within the mosquito before they can infect humans.

• Cyclodevelopmental Transmission: In this type of transmission, the pathogen undergoes developmental changes within the vector but does not multiply. The pathogen changes its form or undergoes a necessary part of its life cycle within the vector before it can be transmitted to the next host. An example is the transmission of filarial worms (e.g., Wuchereria bancrofti) by mosquitoes, where the larvae develop into infective stages in the mosquito but do not multiply.
• Vertical Transmission: This refers to the transmission of a pathogen from an infected parent directly to its offspring. Vertical transmission can occur through the placenta (transplacental), during childbirth (perinatal), or through breast milk (postnatal). An example is the transmission of HIV from an infected mother to her child during pregnancy, childbirth, or breastfeeding.