reproduction

• Types of plant reproduction

  • Sexual
  • Asexual
• Sexual reproduction


  Produces offspring by the fusion of gametes, resulting in offspring genetically different from the parent or parents
• Asexual reproduction


  Produces new individuals without the fusion of gametes, genetically identical to the parent plants and each other, except when mutations occur
• Major groups of plants

  • Nonvascular bryophytes (mosses, hornworts, and liverworts)
  • Vascular tracheophytes
• Vascular plants


  • Seedless lycophytes and ferns (lower vascular plants)
  • Gymnosperms
  • Angiosperms
• Fragmentation followed by regeneration is a common reproductive system in many plant groups
• Desirable garden plant varieties are often propagated through plant fragments or cuttings
• Asexual reproduction practices in horticulture


  • Budding (removing buds from one plant and implanting them on another)
  • Grafting (implanting small branches from one individual onto another)
• Organs of asexual reproduction in plants

  Specially differentiated or modified cells, groups of cells, or organs that enable asexual reproduction without the union of sex cells (gametes)
• Airborne spores are characteristic of nonflowering land plants like mosses, liverworts, and ferns, and can grow directly into new individuals
• Vegetative organs of plants that can be modified to serve as organs of reproduction SRTCB

  • Stolons
  • Rhizomes
  • Tubers
  • Corms
  • Bulbs
• Sexual reproduction at the cellular level

  Involves the union of sex cells and their nuclei, along with the association of their chromosomes containing genes, and the nuclear division known as meiosis
• Sex cells (gametes)


  Typically haploid (having a single set of chromosomes), while zygotes resulting from their union are diploid (having a double set of chromosomes, one from each parent)
• Characteristics of gametes

  • Motility through flagella or amoeboid motion
  • Morphologically indistinguishable (isogamous) or distinguishable only by size (heterogamous), with eggs being nonmotile and sperm being motile
• Oogamy


  The distinction between eggs and sperm, where fertilization occurs through the union of sperm and egg
• Evolutionary series in gametic differences

  • Isogamy
  • Heterogamy
  • Oogamy
• Types of flowers based on the presence of the whorls


  • Complete (built with four parts: sepals, petals, pistils and stamens)
  • Incomplete (missing any of the four parts)
• Types of flowers based on the presence of the reproductive whorls

  • Perfect/Bisexual (both male and female reproductive structures present)
  • Imperfect/Unisexual (does not have both male and female structures)
• Double fertilization is a unique process occurring in flowering plants (angiosperms)
• Double fertilization process

  1. Pollen grain germinates, pollen tube grows down the style toward the ovary

  2. Pollen tube discharges two sperm into the female gametophyte (embryo sac) within an ovule

  3. One sperm fertilizes the egg, forming the zygote. The other sperm combines with the two polar nuclei of the embryo sac's large central cell, forming a triploid cell that develops into the nutritive tissue called endosperm
• Types of seed plants

  • Gymnosperms (produce "naked seeds" where reproductive organs are either male or female, without enclosing structures)
  • Angiosperms (produce seeds enclosed within a carpel (fruit))
• Angiosperm seed types

  • Monocot
  • Dicot
• Monocot seed

  Has a protective seed coat, aleurone layer aids in digestion during germination, endosperm forms separately from the embryo, embryo shielded by the tough scutellum and coleorhiza, single cotyledon (scutellum) absorbs nutrients from the endosperm
• Dicot seed


  Typically has two cotyledons, which may function as leaves or food storage organs, structures include the radicle and plumule, some lack aleurone or coleorhiza, embryo and cotyledons result from the fertilization process
• Seed germination

  1. Breaking dormancy - embryo emits gibberellin hormone, triggers production of digestive enzymes

  2. Early root and emergence - root tip protected by cap of dead cells, zone of division undergoes vigorous mitosis, zone of elongation responsible for lengthwise growth

  3. Primary meristems - give rise to differentiated tissues like phloem and xylem, some tissues remain undifferentiated, forming cambium and pericycle layers

  4. Leaf bud and leaf growth - leaf growth originates from side of meristem, growing upward and enlarging
• Ecology of abscission


  Abscission is process of shedding plant parts, abscission layer allows loss of leaves, creates point of weakness facilitating shedding by wind
• Secondary growth in dicots

  Differentiation occurs behind growing tips of stem and root, provascular cylinder develops into vascular tissues, protoderm becomes epidermis, ground meristem forms cortex and pith
• Secondary growth in monocots

  Secondary growth is rare, trunk diameter remains consistent from base to crown, primary thickening meristem lays down vascular and other differentiated tissues to form stem
• Animal reproduction modes

  • Asexual reproduction (without fusion of egg and sperm)
  • Sexual reproduction (involves fusion of haploid gametes)
• Female gamete (egg/ovum)


  Relatively large and immotile
• Male gamete (sperm)


  Smaller and motile
• Sexual reproduction

  Promotes genetic variability among offspring by combining unique gene combinations from two parents, enhancing adaptability to changing environments
• Asexual reproduction


  Offers advantages such as enabling isolated animals to produce offspring without mates and producing numerous offspring rapidly, facilitating habitat colonization
• Reproductive variations

  • Metagenesis (alternation of asexual and sexual generations) "Transformation development"
  • Parthenogenesis (unfertilized egg develops into adult/ allows reproduction without the mating) "Virgin development"
  • Hermaphroditism (single organism produces both eggs and sperm)
• Human female reproductive organs

  • Ovaries
  • Oviducts and Uterus
  • Vagina and Vulva
  • Mammary glands
• Human male reproductive organs TDGSP

  • Testes
  • Ducts
  • Glands
  • Semen
  • Penis
• Types of physiological reactions in human sexual response

  • Vasocongestion (filling of tissue with blood caused by increased blood flow through the arteries of that tissue
  • Myotonia (increased muscle tension of both skeletal and smooth muscles)
• Early human development

  1. Zygote (fertilized egg with potential to give rise to all cell types)

  2. Cleavage (rapid mitosis process, from one cell to many)

  3. Formation of germ layers (endoderm, mesoderm, ectoderm)
• Testes- Consist of seminiferous tubules where sperm form, surrounded by connective tissue layers
• Leydig cells produce testosterone and other androgens; located outside the abdominal cavity in the scrotum to maintain lower temperatures conducive to sperm production.