Act 21: Invertebrates Reproduction and Development

• asexual reproduction - A mode that eliminates the need for the fusion of gametes.
• Budding is characterized by a new organism developing from an outgrowth on the parental body.
• fragmentation through the splitting into fragments of the parental organism.
• Parthenogenesis - when an egg can develop into an embryo in the absence of fertilization.
• Parthenogenesis is typified in insects like aphids.
• sexual reproduction relies on the fusion of gametes or sex cells.
• fusion of gametes or fertilization
• two types of fertilization: external and internal
• external fertilization, the egg and the sperm are shed freely and fuse outside the animals’ body
• internal fertilization is achieved through the transfer of the sperm from the male into the female reproductive tract.
• gametogenesis - formation of sperm and egg
• 3 stages of development: pre-embryonic, embryonic, and post embryonic
• pre-embryonic stage: gametogenesis and fertilization
• embryonic stage - wherein growth, morphogenesis and differentiation

  happens.
• post-embryonic development - insects undergo a sequence of morphological changes, that extend from egg to adult stage.
• metamorphosis - succession of morphological changes is
• two types of metamorphosis: complete (holometabolous) and incomplete (hemimetabolous).
• Complete metamorphosis consists of four stages: egg, larva, pupa, and adult
• incomplete metamorphosis consists of three stages: egg, nymph, and

  adult.
• Both females and males possess a pair of sensory organs called cerci.
• Styli are for male cockroach, it is smaller and more delicate than cerci.
• These ovaries are held into place anteriorly by slender thread-like structures called the terminal filament.
• Each ovary is composed of eight elongated ovarioles in which eggs develop.
• The ovarioles are connected by short tubes to the oviduct.
• The testes are well developed and elaborate structures that contain sperms.
• Arising from each testis is a thin thread-like, white vas deferens.
• The ejaculatory duct is wide extended median duct along the abdomen and opening out at the male gonopore just ventral to the anus.
• mushroom gland of Huxley is a prominent structure is composed of dense, white to yellowish bundles in which the spermatophore is formed.
• Insects that show complete metamorphosis are known to comprise Endopterygota.
• Exopterygota refers to groups of insects whose development of the wings are outside the body.