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Reproductive systems and Animal Development

Explore asexual and sexual reproduction in animals, advantages of each, hermaphroditism, fertilization, reproductive organs, and the role of the endocrine system in reproduction. Discover the stages of cellular and tissue development and the human conception process.

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Reproductive systems and Animal Development

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  1. Reproductive systems and Animal Development

  2. Asexual Reproduction • Binary fission • Budding, fragmentation • Sponges, cnidarians, flatworms, annelids, echinoderms • Parthenogenesis – unfertilized egg develops into a complete individual, pg731

  3. Sexual reproduction • Egg of one parent is fertilized by the sperm of another. • Dioecious – 2 sexes • Monoecious – hermaphrodites, few undergo self-fertilization, most cross fertilization • Oviparous – • Ovoviviparous – • Viviparous -

  4. Advantages of Asexual vs Sexual • Asexual • More offspring identical to parent • Sexual • Beneficial gene combinations that arise through recombination that speed up adaptation in a changing environment • Can rid a population of harmful genes more easily.

  5. Hermaphroditism – each individual has both male and female reproductive systems – donates and receives sperm • Example: earthworms, sea slugs • Internal fertilization – sperm deposited in or near female reproductive tract, fewer gametes and zygotes produced • External fertilization – females release eggs into environment, male then fertilizes them, release of gametes by environmental cues, pheromones

  6. Reproductive Organs • Gonads – organs that produce gametes, found in most animals. • Cloaca – structure found in ancestors of vertebrates. Found in non-mammal vertebrates • Digestive, excretory and reproductive opening for wastes.

  7. Gametogenesis - production of gametes • Spermatogenesis – production of sperm • Oogenesis – production of egg

  8. Male Reproductive System • Testes – produce sperm and sex hormones • Epididymis – maturation of sperm • Vas deferens – store sperm • Seminal vesicles – contribute most fluid to sperm • Prostate gland – contribute fluid • Urethra – conduct sperm and urine • Bulbourethral gland – little fluid to sperm • penis

  9. Sperm: hundreds of millions produced each day • 3 parts • Head – nucleus covered by a cap (acrosome) • Middle piece – mitochondria (energy) and microtubules • Tail – microtubules • Takes 7 weeks for 1 sperm to develop • Testosterone – main male sex hormone

  10. Female Reproductive System • Ovaries – produce ovum and hormones • Oviduct (fallopian tubes) – conduct egg, fertilization • Uterus – houses embryo during development • Vagina

  11. Fertilization

  12. Endocrine System Role in Reproduction • Hypothalamus, anterior pituitary and gonads govern hormones in reproduction cycle • Follicle stimulating hormone and luteinizing hormone, tropic hormones • Primary sex hormones: • Androgens: Testosterone • Estrogens: progesterone and estradiol • Males and females produce all hormones but in different concentrations • Adrenal gland also produces sex hormones

  13. Cellular stages of development • Cleavage – cell division without growth • Cells get smaller with each division • Morula – ball of cells (16) • Blastula • forms a hollow ball of cells, fluid filled cavity – blastocoel when sodium leaves morula

  14. Tissue stages of development • Early Gastrula – cells invaginate into the blastocoel forming the blastopore (protostomes – mouth, deuterstomes – anus) • Early gastula has 2 layers of cells, • Ectoderm – outer layer • Endoderm – primitive gut • Late gastrula – mesoderm forms • Gastrulation complete

  15. Embryonic Germ Layers • Ectoderm – nervous system, epidermis of skin • Mesoderm – musculoskeletal system, dermis of skin, cardiovascular system, urinary system, lymphatic system, reproductive system, outer layers of respiratory and digestive systems • Endoderm – lining of digestive tract and resp. tract, glands, thyroid/parathyroid glands

  16. Developmental processes • Development requires • Growth • Cellular differentiate – cells become specialized • Morphogenesis- shape and form of body

  17. Human Conception • AKA Fertilization– sperm fuses with an egg • Gestation– pregnancy – carrying one or more embryos in the uterus • Placenta– disk shaped organ with embryonic and maternal blood vessels, provides nutrients • Organogenesis – development of the body organs, mainly in first trimester • Fetus– embryo at 8 weeks

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