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Reproductive systems and Animal Development

Reproductive systems and Animal Development. Asexual Reproduction. Binary fission Budding, fragmentation Sponges, cnidarians, flatworms, annelids, echinoderms Parthenogenesis – unfertilized egg develops into a complete individual, pg731. Sexual reproduction.

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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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