Reproduction in Animals and Plants

• Types of Reproduction

  • Asexual reproduction
  • Sexual reproduction
• Types of Asexual Reproduction

  • Binary fission
  • Budding
  • Parthenogenesis
• Types of Sexual Reproduction

  • Internal fertilization
  • External fertilization
• Hermaphroditism


  Organisms that have both male and female reproductive organs, which may be fully or partially functional
• Hermaphroditic organisms

  • Tapeworms
  • Liver flukes
  • Earthworms
• Simultaneous hermaphroditism


  An individual has both functional male and female sex organs at the same time and can produce sperm and eggs concurrently
• Sequential hermaphroditism

  The individual changes sex at some point in its life cycle
• Types of Sequential Hermaphroditism

  • Protandry
  • Protogyny
• Variations of Embryonic Development

  • Oviparity
  • Ovoviviparity
  • Viviparity
• HPO axis

  Hypothalamic-Pituitary-Ovarian Axis, a complex communication system in the female body that regulates the menstrual cycle, ovulation, and other reproductive functions

  
• Hypothalamus


  • Produces gonadotropin-releasing hormone (GnRH), which plays a key role in regulating the HPO axis
• Pituitary gland


  • Receives GnRH signals from the hypothalamus and then releases follicle-stimulating hormone (FSH) and luteinizing hormone (LH)
• Ovaries

  • Produce eggs and sex hormones, including estrogen and progesterone, which regulate the development of the uterine lining and play a role in preparing the body for pregnancy

  
• Regulation of the Female Reproductive System

  1. Hypothalamus releases GnRH

  2. GnRH stimulates pituitary gland to release FSH and LH

  3. FSH stimulates follicle development in ovaries

  4. Follicles produce estrogen

  5. Estrogen triggers LH surge

  6. LH surge triggers ovulation

  7. Corpus luteum produces progesterone

  8. Progesterone prepares uterine lining

  9. Progesterone drop triggers menstruation

  
• Phases of the Uterine/Menstrual Cycle

  • Menstruation
  • Follicular Phase
  • Ovulation
  • Luteal Phase

  
• Menopause


  Occurs due to unresponsiveness of ovarian follicles to FSH, leading to low estrogen levels despite high FSH
• Key Players in Male Reproductive System Regulation

  • Hypothalamus
  • Pituitary Gland
  • Leydig Cells
  • Sertoli Cells
• Regulation of Male Reproductive System

  1. Hypothalamus releases GnRH

  2. GnRH stimulates pituitary to release FSH and LH

  3. FSH stimulates sperm production in Sertoli cells

  4. LH stimulates testosterone production in Leydig cells

  
• Hormones and their Roles

  • GnRH
  • FSH
  • LH
  • Testosterone
• Feedback Loop in Male Reproductive System

  1. Low testosterone levels increase GnRH, FSH, and LH

  2. High testosterone levels inhibit GnRH and pituitary hormones

  3. Inhibin from Sertoli cells also regulates FSH
• The male reproductive system matures during puberty, and testosterone levels typically peak in early adulthood, gradually declining with age
• The Feedback Loop

  1. When testosterone levels are low, the hypothalamus increases GnRH production

  2. Increased GnRH stimulates the pituitary gland to release more FSH and LH

  3. FSH stimulates sperm production, and LH stimulates testosterone production

  4. As testosterone levels rise, they send an inhibitory signal back to the hypothalamus and pituitary gland

  5. This feedback loop ensures that hormone levels are maintained within a healthy range
• Inhibin

  • A hormone produced by the Sertoli cells, also plays a role in regulating FSH production
  • When sperm production is high, inhibin levels rise, providing another layer of control
• Male reproductive system

  • Matures during puberty
  • Testosterone levels typically peak in early adulthood, gradually declining with age
• Fertility requirements for males

  • At least 20 million sperm per mL
  • At least 75% of the sperm must be alive
  • At least 25% of the sperm should be swimming with rapid forward movement
• Sperm Head

  • Oval-shaped front part of the sperm, containing the genetic material
  • Houses the nucleus, which holds tightly packed chromosomes
  • Acrosome: Covering the head like a cap, contains enzymes that help the sperm penetrate the egg's outer layers during fertilization

  
• Sperm Midpiece

  • Connecting the head to the tail, the powerhouse
  • Contains numerous mitochondria that convert oxygen and nutrients into energy (ATP) to fuel the sperm's vigorous swimming movements
• Sperm Tail

  • Also called the flagellum, a long, whip-like structure that propels the sperm forward
  • Undulating movements of the tail allow the sperm to navigate the female reproductive tract
• Contraceptive Methods

  • Combined Oral Contraceptive Pill (the Pill)
  • Progestin-Only Pill (Mini-Pill)
  • IUD (Intrauterine Device)
  • Implant (Birth Control Rod)
  • Patch
  • Vaginal Ring
  • Spermicide
  • Withdrawal (Pulling Out)
  • Barriers/condoms (Male & Female)
  • Diaphragm & Cervical Cap
  • Sterilization (Tubal Ligation or Vasectomy)
• Typical Use Success Rate

  The success rate of a contraceptive method when used typically by the average person
• Perfect Use Success Rate

  The success rate of a contraceptive method when used perfectly according to instructions
• Mammalian Development - The First 4 Stages

  1. Fertilization: Sperm fuses with an egg, creating a single-celled zygote

  2. Cleavage: Zygote undergoes rapid cell division, transforming into a ball of cells called a blastula

  3. Gastrulation: Blastula transforms into a gastrula with three distinct cell layers (ectoderm, mesoderm, endoderm)

  4. Organogenesis: The three germ layers differentiate and specialize to form organs and organ systems

  
• Pregnancy Milestones

  • 8th week - fetal heartbeat can be heard
  • 19th week - the mother can feel the baby's movements
  • 28th week - the lungs, while still immature, can now perform gas exchange
  • 30th week - progressive growth of the fetus and development of its organs

  
• Pregnancy in humans usually lasts for a total of 9 months or 38 to 42 weeks
• Life Cycle of Nonvascular Plants

  1. Gametophyte stage and sporophyte stage alternate to complete the cycle

  2. The female gametophyte produces the egg cell inside the archegonium

  3. Sperm from the antheridium fertilizes the egg, forming a zygote that develops into the sporophyte

  4. Inside the sporophyte's capsule, meiosis occurs to produce spores

  5. The spores germinate into a protonema, which gives rise to the male and female gametophytes
• Life Cycle of a Fern

  1. Spores are found inside the sori on the underside of fronds or in strobili

  2. The sporophytic generation is more dominant in ferns
• Asexual Reproduction in Plants via Vegetative Propagation

  • Stem Cuttings
  • Leaf Cuttings
  • Suckers
  • Tubers
  • Rhizomes
  • Bulbils
• Fragmentation

  A simple method where a piece of the parent plant breaks off and develops into a new individual under suitable conditions
• Stamen

  The male reproductive organ of a flower, consisting of a filament and anther that produces pollen grains containing sperm cells

  
• Pistil

  The female reproductive organ of a flower, composed of the stigma, style, and ovary containing ovules (eggs)