Reproduction; CBA1

• Natural selection is process in which organisms with favourable traits are selected to survive and pass their traits to offspring
• Evolution is gradual change in inheritable characteristics of population over time
• 1. In the population of ..., there exists individuals with .., .. and ..
  2. Individuals with .. are less easily detected by predators, compared to ..
  3. They are more likely to survive and reproduce, thereby passing on the trait for .. to their offspring.
  4. Over many generations, the population will contain more .. individuals.
• Mutation

  1. Use of .. has led to evolution of P.
  2. Genetic variations occur in P because of M. P with M which .. will survive, while those without M will die.
  3. Those that survive will pass their M trait to their offspring.
  4. Over many generations, the proportion of P with the M increased and proportion of P evolved and survived the ..
• Artificial selection is caused by selective breeding, ≠ genetic modification.
• Artificial Selection

  1. P with desired characteristics, .. were chosen as the parents to produce many offspring
  2. Offspring with the desired .. traits in the first generation were selected.
  3. Selected offspring were used as parents for breeding the next generation and the process was repeated over many generations to produce the .. breed, while offsprings without .. traits killed.
• natural selection forces (env. factors)

  1. Competition
  2. predation
  3. human destruction
• examples of artificial selection

  1. selective breeding pigeons
  2. domestication of wild animals
  3. improvement of crops (wheat, rice maize)
• asexual reproduction is process that results in production of genetically identical offspring from 1 parent, without fusion of gametes.
• sexual reproduction is process involving fusion of 2 gametes to form a zygote. produces genetically dissimilar offspring.
• advantages of asexual reproduction

  1. 1 parent required
  2. fusion of gamete not required
  3. all beneficial qualities passed down to offspring
  4. faster than sexual reproduction
• disadvantages of asexual reproduction

  1. no genetic variation in offspring - species not well adapted to changes in environment
• advantages of sexual reproduction

  1. may inherit beneficial qualities
  2. genetic variation in offspring
• disadvantages of sexual reproduction

  1. fusion of gametes needed
  2. slower
• main functions of male reproduction system

  1. store, produce, transport sperm and protective & nutritious fluid (semen)
  2. discharge sperm within female reproductive tract
  3. to produce and secrete male sex hormones (testosterone)
• unlike female system, male and urinary system have direct connection
• prostate gland:

  1. produce fluid that nourishes sperm and provide protection from natural acidity of vagina
• penis:

  1. contain erectile tissue filled with blood and cause erection during sexual arousal
  2. deliver sperm to vagina
• testes (singular: testis)

  1. make testosterone, produce sperm
  2. male gonads, located outside abdominal cavity in scrotum
• scrotum

  1. keeps sperm-forming cells about 2ºC cooler to function normally (not best at body temp)
  2. special muscles in walls that contract and relax
• sperm duct: delivers sperm to urethra during ejaculation (caused by contraction of muscle along sperm ducts, release semen)
• urethra:

  1. conveys sperm and urine out of body through penis
  2. penis erects, semen ejaculated by urethra (flow of urine blocked)
• main functions of female reproductive cell:

  1. produce egg cells (ovum, plural: ova) for reproduction
  2. transport ova to site of fertilisation (oviduct)
  3. produce safe and favourable environment for foetus to develop (uterus)
  4. produce female sex hormones
• vagina:

  1. opens to outside, behind opening of urethra
  2. repository for sperm
• ovaries:

  1. site of gamete production
  2. bumpy surface (follicles), each consist 1 ovum surrounded by cells that nourish and protect it -> if no fertilisation, egg is shed during menstruation and new follicle matures next cycle
• oviduct: site of fertilisation
• uterus:

  1. site of pregnancy
  2. endometrium: thick muscular wall lined with blood-rich layer of tissue
• cervix: opens up into vagina, allowing flow of menstrual blood into vagina, direct sperm to uterus
• infertility: condition where couples who want children unable to conceive, even after 12 months of unprotected intercourse
• reasons for infertility:

  male:

  1. low sperm count
  2. erectile dysfunction

  female:

  1. blocked fallopian tubes
  2. inability to support growing embryo
  3. lack eggs, cannot ovulate
• in-vitro fertilisation (IVF):

  1. hormonal stimulation -> eggs surgically removed from ovaries
  2. mixed with sperm in culture dish
  3. incubated for several days to allow fertilised eggs to develop
  4. 1-2 embryos inserted into uterus
• sexually-transmitted diseases: bacterial or viral disease transmitted through sex
• human immunodeficiency virus (HIV):

  1. semen from infected male
  2. vaginal fluid from infected female
  3. blood from infected person

  transmitted:

  1. sex
  2. share hypothermic needles
  3. blood transfusion
  4. pregnancy
• AIDS (acquired immune deficiency syndrome): advanced stage of HIV infection
• AIDS symptoms:

  1. pneumonia
  2. brain infection
  3. chronic/persistent fever
  4. widespread tubercolosis
  5. severe diahorrea (months)
  6. kaposi's sarcoma; cancer of bloodcells
• fertilisation is process nucleus of male gamete fuses with nucleus of female gamete to produce zygote
• conception is process starts with fertilisation and ends with implantation of embryo