REPRODUCTION, DEVELOPMENT, AND NUTRITION

• Pollination

  The transfer of pollen from an anther to a stigma
• Propagules

  Body parts specialized for breakaway and dispersal
• 
  

  In grafting, the plant that is to be asexually propagated is known as the scion; this is attached to the stock, which may be little more than a root. It is important that the two have their cambium layers in contact with each other.
• Fragmentation


  The type of reproduction in which an animal divides into several pieces and then each piece develops into an entire new animal
• Parthenogenesis

  A type of reproduction in which an unfertilized egg develops into a new individual
• Hermaphroditic

  An individual that can produce both eggs and sperm

  
• Gamete; zygote

  A sex cell (either egg or sperm) is properly called a gamete; a fertilized egg is a zygote.

  
• Floral organs

  • Sepals
  • Petals
  • Stamens
  • Carpels (pistils)

  
• Stamen

  Consists of a stalk called the filament and a terminal structure called the anther; within the anther are chambers called pollen sacs, in which pollen is produced.

  
• Carpel

  Has an ovary at its base and a long, slender neck called the style. At the top of the style is the sticky structure called the stigma that serves as a landing platform for pollen. Within the ovary are one or more ovules, with the number depending on the species.

  
• Complete flower

  A plant biology term that is used to describe a flower that is built with four parts which include the sepals, petals, pistils, and stamens.

  
• Incomplete flower


  If any of the sepals, petals, pistils, and stamens, which are integral in forming a flower, is missing, a flower is called an incomplete flower.
• Perfect/Bisexual flower


  A flower in which both male and female reproductive structures are present. Both androecium (whorl of stamens) and gynoecium (whorl of carpels or pistil) are located on the same flower.

  
• Imperfect/Unisexual flower

  A flower that does not have both male and female structures.
• Imperfect/Unisexual flowers

  • Squashes, cucumbers, corn, and grasses
• Double fertilization


  After landing on a receptive stigma, a pollen grain absorbs moisture and germinates; that is, it produces a pollen tube that extends down between the cells of the style toward the ovary.

  
• From ovule to seed


  After double fertilization, each ovule develops into a seed, and the ovary develops into a fruit enclosing the seed(s). As the embryo develops from the zygote, the seed stockpiles proteins, oils, and starch to varying extents, depending on the species. This is why seeds are such major sugar sinks. Initially, these nutrients are stored in the endosperm, but later in seed development in many species, the storage function of the endosperm is more or less taken over by the swelling cotyledons of the embryo.

  
• From ovary to fruit


  While the seeds are developing from ovules, the ovary of the flower is developing into a fruit, which protects the enclosed seeds and, when mature, aids in their dispersal by wind or animals. Fertilization triggers hormonal changes that cause the ovary to begin its transformation into a fruit. If the flower has not been pollinated, fruit usually does not develop, and the entire flower withers and falls away.

  
• Asexual reproduction

  The creation of new individuals whose genes all come from one parent without the fusion of egg and sperm.
• Sexual reproduction

  The creation of offspring by the fusion of haploid gametes to form a zygote (fertilized egg), which is diploid.

  
• Female gamete

  The unfertilized egg (also called an ovum), is a relatively large cell and not motile.

  
• Male gamete


  The sperm, is generally a much smaller, motile cell.
• Advantages of sexual reproduction


  • It increases genetic variability among offspring by generating unique combinations of genes inherited from two parents. This may enhance the reproductive success of parents when environmental factors change relatively rapidly.
• Advantages of asexual reproduction

  • It enables animals living in isolation to produce offspring without locating mates. It can also create numerous offspring in a short amount of time, which is ideal for colonizing a habitat rapidly. It perpetuates successful genotypes precisely in stable, favorable environments.
• Types of asexual reproduction

  • Fission
  • Budding
  • Fragmentation
  • Regeneration
• Internal fertilization

  The male generally delivers sperm cells directly into the body of the female. Her moist tissues provide the watery medium required for movement of sperm.

  
• External fertilization


  Mating partners usually release eggs and sperms into the water simultaneously.

  
• Male reproductive system

  • Male gonad (testis)
  • Sperm duct
  • Penis

  
• Female reproductive system


  • Female gonad (ovary)
  • Oviduct
  • Vagina

  
• Metagenesis


  Also known as 'transformation development', refers to an alternation of asexual and sexual generations.
• Parthenogenesis

  A form of reproduction in which an unfertilized egg develops into an adult animal
• Honeybees


  • The queen honeybee is inseminated by a male during the "nuptial flight". The sperm she receives are stored and she can either fertilize the eggs or lay unfertilized eggs that become males.

  
• Hermaphroditism


  A single organism produces both eggs and sperm

  
• Ovaries

  • Produce both the egg cell and the sex hormones. Enclosed in a tough protective capsule and contains many follicles. Egg cell is expelled from the follicle in the process of ovulation.

  
• The uterus is a thick, muscular organ that can expand during pregnancy to accommodate a 4-kg fetus.
• Vagina is a thin-walled chamber that is the repository for sperm during copulation and that serves as the birth canal through which a baby is born. Vulva is a collective term for the external female genitalia.

  
• Mammary glands


  • Present in both sexes but normally function only in women. They are not part of the reproductive system but are important to mammalian reproduction. Within the glands, small sacs of epithelial tissue secrete milk which drains into a series of ducts opening at the nipple.
• Testes


  • Consist of many highly coiled tubes (seminiferous tubules – where sperm form) surrounded by several layers of connective tissue. The Leydig cells that are scattered between the seminiferous tubules produce testosterone and other androgens. The production of normal sperm cannot occur at the normal body temperatures of most mammals, and the testes of humans and many other mammals are held outside the abdominal cavity in the scrotum.
• Ducts


  • From seminiferous tubules, the sperm pass into the epididymis. During ejaculation, the sperm are propelled from the epididymis through the muscular vas deferens. These two ducts (one from each epididymis) run from the scrotum around and behind the urinary bladder, where each joins a duct from the seminal vesicl, forming a short ejaculatory duct. The ejaculatory ducts open into the urethra, the tube that drains both the excretory system and reproductive system of male. The urethra runs through the penis and opens to the outside at the tip of the penis.
• Glands

  • Three sets of accessory glands – the seminal vesicles, prostate gland, and bulbourethral glands – add secretions to the semen, the fluid that is ejaculated.