Biology

• Topics covered


  • Modes of sexual and asexual reproduction
  • Processes in human and animal development
  • Human reproductive organ system
  • Stages of human fertilization
  • Phases of female menstrual cycle
  • Potential and common STIs/STDs and its treatment
• The major function of the reproductive system is to ensure survival of the species
• Other systems in the body, such as the endocrine and urinary systems, work continuously to maintain homeostasis for survival of the individual
• An individual may live a long, healthy, and happy life without producing offspring, but if the species is to continue, at least some individuals must produce offspring
• Asexual reproduction


  The mode of reproduction that does not involve the use of gametes or sex cells
• Sexual reproduction


  The mode of reproduction that involves the use of gametes or sex cells
• Fission


  A type of asexual reproduction involving the division of body into two or more equal parts

  
• Fragmentation


  A type of asexual reproduction where the body breaks into two or more parts, with each fragment capable of becoming a complete individual; in animals, fragmentation is usually followed by regeneration where the missing parts are produced
• Budding


  A type of asexual reproduction where a new individual arises as an outgrowth (bud) from its parent, develops organs like those of the parent, and then detaches itself
• Sporulation


  A type of asexual reproduction where a new individual forms from an aggregation of cells surrounded by a resistant capsule or spore, which later on germinates

  
• Isogamy


  Fusion of similar gametes which are usually motile
• Heterogamy


  Fusion of dissimilar gametes. In oogamy, a large immotile gamete, the egg is fertilized by a small motile gamete, the sperm
• Bisexual reproduction


  Type of sexual reproduction involving the union of gametes from two genetically different parents
• Hermaphrodite

  An individual with both male and female reproductive tissues. In animals "self fertilization" is not common. In worms, a hermaphrodite needs a male to donate sperms in order to fertilize the oocytes in its body
• Human reproductive system is the organ system by which humans reproduce and bear live offspring
• Development


  Involves formation of sex cells, zygote formation, subsequent stages in one's life span. Development is terminated by death
• Growth


  Stage of development characterized by an increase in size of an individual
• Gametogenesis


  Stage of development that yields haploid gametes
• Haploid (n) condition


  When a cell has only half the chromosome number or only one set of chromosomes
• Diploid (2n) condition


  When a cell has the full chromosome number or two sets of chromosomes
• Fertilization


  Occurs when sperm and oocyte combine and their nuclei fuse. Two haploid cells combine to form one diploid cell. The single cell called zygote contains all genetic material needed to form human

  
• Implantation


  Process where the blastocyst implants itself in the endometrium; this signals the start of pregnancy
• Cleavage


  Stage of development involving a series of mitotic divisions to produce a multicellular blastula from a unicellular zygote

  
• Morula


  A human blastula made up of a solid ball of cells
• Blastocyst


  A human blastula composed of the inner cell mass, which becomes the embryo, and the trophoectoderm, which becomes the placenta
• Gestation


  Carrying of the embryo inside the female reproductive tract, specifically the uterus; can last up to 9 months in humans
• Gastrulation


  Stage of development involving morphogenetic movements of the cells to produce a gastrula with distinct germ cell layers; in vertebrates, this will result in three layers: the outermost ectoderm; the inner endoderm, and the middle layer, the mesoderm
• Organogenesis


  Stage of development where the different germ layers differentiate into specific organ systems
• Human embryo


  Corresponds to the first two months of gestation
• Human fetus


  Corresponds to the months 3-9 of human gestation
• Monozygotic twins


  Also known as identical twins; result from the union of a sperm and egg to form a single zygote that splits up during the first cleavage stage
• Dizygotic twins


  Also known as fraternal twins; results from the development of two or more separate fertilization events where the resulting zygotes develop almost simultaneously
• Testis


  Where sperms are produced
• Epididymis


  Where sperms are temporarily stored

  
• Scrotal sac/scrotum


  Supports the testis and epididymis
• Vas deferens


  Where the sperm passes through from the testis before it joins the urethra
• Urethra


  Connected to the urethra and the urinary bladder; serves as passageway of both sperm and urine and terminates in the external urinary meatus of the penis
• Seminal vesicle


  Secretes fluid that forms part of the semen; secretion gives the semen its alkaline characteristic to counteract the acidity of the vaginal tract and therefore protect the sperm; the fluid also contains sugars like fructose
• Prostate gland


  Secretes fluid that also provides alkalinity to the semen; it also contains proteolytic enzymes, citric acid, phosphatases, and lipids
• Bulbourethral glands


  Paired glands that produce clear, viscous secretion known as pre-ejaculate that helps to lubricate the urethra for sperm to pass through, neutralizing traces of acidic urine in the urethra, and helps flush out any residual urine or foreign matter