gen bio

• Alternation of generations


  Key derived traits of Angiosperm: "three Fs"—flowers, double fertilization, and fruits

  
• Flower Structure and Function


  • Floral organs—sepals, petals, stamens, and carpels—are attached to a part of the stem called the receptacle
  • STAMEN: Filament & Anther – microsporangia (pollen sac that produce pollen)
  • CARPEL: Style, Stigma & Ovary (ovules)
  • PISTIL: the term sometimes used to refer to a single carpel or two or more fused carpels

  
• Flower


  • Complete flowers have all four basic floral organs
  • Incomplete flowers - lacking sepals, petals, stamens, or carpels
  • Inflorescences – showy clusters of flowers
• Development of Male Gametophytes in Pollen Grains

  1. Development of Female Gametophytes (Embryo Sacs)

  2. Pollination: the transfer of pollen from an anther to a stigma

  3. Coevolution of Flower and Pollinator

  
• Double Fertilization

  Seed Development, Form, and Function

  
• Endosperm Development


  Endosperm usually develops before the embryo does
• Embryo Development


  Terminal cell gives rise to most of the embryo

  
• Structure of the Mature Seed


  The embryo, which is surrounded by a food supply (cotyledons, endosperm, or both), enters dormancy
• Seed Dormancy


  An Adaptation for Tough Times: Environmental conditions required to break seed dormancy vary among species
• Seed Germination and Seedling Development


  Imbibition - the uptake of water due to the low water potential of the dry seed
• Fruit Form and Function

  Fruit - protects the enclosed seeds and, when mature, aids in their dispersal by wind or animals
• Asexual Reproduction


  When offspring are derived from a single parent without fusion of egg and sperm
• Mechanisms of Asexual Reproduction

  • Fragmentation - the separation of a parent plant into parts that develop into whole plants
  • Apomixis - asexual production of seeds
• Advantages and Disadvantages of Asexual Versus Sexual Reproduction

  • There is no need for a pollinator
  • Allows the plant to pass on all of its genetic legacy intact to its progeny
  • Can potentially clone many copies of itself
  • In stable environment: progeny produced by asexual reproduction are stronger than seedlings produced by sexual reproduction
  • Offspring usually arise from mature vegetative fragments from the parent plant (vegetative reproduction)

  
• Mechanisms That Prevent Self-Fertilization

  • Dioecious species - plants cannot self-fertilize because different individuals have either staminate flowers (lacking carpels) or carpellate flowers (lacking stamens)
  • Plants that have flowers with functional stamens and carpels that mature at different times or are structurally arranged in such a way that it is unlikely that an animal pollinator could transfer pollen from anther to a stigma of the same flower
  • Self-incompatibility - the ability of a plant to reject its own pollen and sometimes the pollen of closely related individuals
  • S-genes

  
• Vegetative Propagation and Agriculture

  • Clones from Cuttings
  • Grafting (Stock & Scion)
  • Test-Tube Cloning and Related Techniques – in vitro methods
• Sexual Reproduction


  The fusion of haploid gametes forms a diploid cell, the zygote

  
• Asexual Reproduction


  The generation of new individuals without the fusion of egg and sperm
• Mechanisms of Asexual Reproduction

  • Fission - the separation of a parent organism into two individuals of approximately equal size
  • Budding - new individuals arise from outgrowths of existing ones
  • Fragmentation -- the breaking of the body into several pieces, followed by regeneration -- the regrowth of lost body parts
  • Parthenogenesis is asexual reproduction in which an egg develops without being fertilized

  
• Sexual Reproduction: An Evolutionary Enigma


  Reproductive Cycles: Ovulation - the release of mature eggs, occurs at the midpoint of each cycle. Reproductive cycles are controlled by hormones, which in turn are regulated by environmental cues.
• Variation in Patterns of Sexual Reproduction

  • Hermaphroditism -- in which each individual has both male and female reproductive systems
  • Sex reversal – change in sex
• Fertilization


  • External fertilization - the female releases eggs into the environment, where the male then fertilizes them. Internal fertilization: Sperm are deposited in or near the female reproductive tract, and fertilization occurs within the tract.

  
• Ensuring the Survival of Offspring

  Internal fertilization is typically associated with the production of fewer gametes but the survival of a higher fraction of zygotes. Internal fertilization is also more often associated with mechanisms that provide greater protection of the embryos and parental care of the young.
• Courtship behavior


  It allows mate choice and, by triggering the release of both sperm and eggs, increases the probability of successful fertilization.
• Pheromones


  Chemicals released by one organism that can influence the physiology and behavior of other individuals of the same species.
• Gamete Production and Delivery


  • Sexual reproduction in animals relies on sets of cells that are precursors for eggs and sperm. Gonads - the organs that produce gametes in most animals. Sets of accessory tubes and glands that carry, nourish, and protect the gametes and sometimes the developing embryos. Spermathecae - sacs in which sperm may be stored for extended periods, a year or more in some species.

  
• Cloaca


  Common opening of digestive, excretory, and reproductive system.
• Monogamy, the sustained sexual partnership of two individuals, is relatively rare among animals, including most mammals.
• Reproductive Organs


  • Produce and transport gametes

  
• Female Reproductive Anatomy

  • External and Internal reproductive structures
• External Reproductive Structures

  • Vulva- outside opening. Labia majora, Labia minora, Hymen, Clitoris (glans & prepuce)
• Internal Reproductive Structures

  • Ovaries, Oviducts and Uterus, Vagina, Mammary Glands
• Male Reproductive Anatomy

  • External and Internal reproductive structures
• External Reproductive Structure

  • Penis
• Internal Reproductive Structure

  • Testes, Ducts, Accessory Glands
• Gametogenesis


  Spermatogenesis, the formation and development of sperm, is continuous and prolific in adult males. Oogenesis, the development of mature oocytes (eggs), is a prolonged process in the human female.

  
• Regulation of Mammalian Reproduction


  Interplay of tropic and sex hormones
• Hormonal Control of Female Reproductive Cycles

  • Menstrual cycle or uterine cycle (average 28 days), Ovarian cycle
• The Ovarian Cycle

  • Proliferative Phase, Secretory Phase, Menstrual Flow Phase
• Endometriosis


  A disorder in which some cells of the uterine lining migrate to an abdominal location that is abnormal