Reproduction D3.1.1- D3.1.4

• What is reproduction? Reproduction is a function of life. It is the process by which organisms replicate themselves. It may either be asexual or sexual.
• What is asexual reproduction? - Only one parent

  - Produces genetically identical offspring

  - Offspring adapted to a predictable environment

  - Less genetic diversity (only variation stems from mutation)

  - Binary fission- single parent cell divides into two cells

  - Mitosis- parent cell produces genetically identical offspring

  - Budding- in yeast, unequal cytokinesis
• What is sexual reproduction? - Two parents- the fusion of haploid sex cells

  - Produces genetically unique offspring

  - Increases genetic variation due to independent assortment and crossing over in meiosis, and random union of gametes during fertilisation

  - Increased genetic variation increases the chance that some offspring will survive in an unpredictable environment.
• What is the life cycle of a sexually reproducing organism? - A life cycle is the series of stages of the life of an organism.

  - The life cycle of a sexually reproducing organism begins with a diploid zygote which performs mitosis to grow into an adult organism.

  - The adult organism performs meiosis to form haploid gametes.

  - The haploid gametes from two organisms fuse at fertilisation, to create a new organism.
• What is the role of meiosis in the life cycle of a sexually reproducing organism? Meiosis is a reduction division. It halves the number of chromosomes in the daughter cell- from diploid to haploid.

  This maintains the correct number of chromosomes in each generation.
• What is the role of fertilisation in the life cycle of a sexually reproducing organism? At fertilisation, two haploid gametes fuse to form a diploid zygote. In fusing two haploids with half the total number of chromosomes, the chromosome number is maintained (diploid).
• How does sexual reproduction result in variation, and what are the implications? Sexual reproduction results in genetic variation between parents and offspring. Variation is a defining feature of life.

  Variation is created through crossing over in meiosis I (prophase), random assortment in meiosis I (metaphase) and random fusion of gametes during fertilisation
• What are gametes? Gametes are cells formed in meiosis that contain a haploid nucleus that is used to pass genetic information from parents to offspring. All plants and animals are anisogamous, meaning that they have different male and female gametes.

  - Males produce sperm (spermatozoa)

  - Females produce eggs (oocytes)
• What are some features of male gametes? - Possess motility

  - Long cells with small volume

  - Small food reserves- only enough for the gamete

  - Large numbers produced- to increase chances of fertilisation
• What are some features of female gametes? - No motility

  - Large spherical cells

  - Large food reserves- store all the materials and nutritional reserves needed for initial embryo development

  - Few numbers produced (often only one)- to support embryo development
• What does the male reproductive system include? - Testis

  - epididymis

  - scrotum

  - Vas deferens

  - Seminal vesicles

  - Prostate gland

  - Penis

  - Urethra
• What is the function of the testes? Produce sperm and testosterone
• What is the function of the scrotum? Holds testes at lower than body core temperature
• What is the function of the epididymis? Store and mature sperm
• What is the function of the vas deferens? Transports sperm from epididymis to urethra during ejaculation
• What is the function of the seminal vesicles? Produce seminal fluid (nutrients for sperm containing fructose)
• What is the function of the prostate gland? Adds alkali fluids to semen to help sperm motility
• What is the function of the urethra? Conducts semen and urine out of the body
• What is the function of the penis? Organ for delivering sperm into female reproductive tract