biology reproduction

• Asexual Reproduction


  The process resulting in the production of genetically identical offspring from one parent
• Bacterial Reproduction


  1. Binary fission

  2. Each bacterium divides into two

  3. Generation time is the time taken for a cell to divide into 2
• Advantages of Asexual Reproduction

  • Fast: no need to find a mate, fertilise, etc.
  • Good characteristics are kept
  • Do not need to carry offspring
• Disadvantages of Asexual Reproduction

  • No variation/biodiversity
  • Harmful genes transferred
  • Overcrowding- fighting for food
  • Prone to extinction
• You must be able to identify examples of asexual reproduction in diagrams, images and information provided
• Sexual Reproduction


  A process involving the fusion of the nuclei of two gametes (sex cells) to form a zygote and the production of offspring that are genetically different from each other
• Fertilisation


  The fusion of gamete nuclei
• Diploid


  Full Set of Chromosomes
• Haploid


  Half Set of Chromosomes
• Advantages of Sexual Reproduction

  • Produces genetically different offspring
  • Reduced risk of extinction
• Disadvantages of Sexual Reproduction

  • It takes lots of time and energy
  • Mate required
  • Energy on improving appearances or pollen volume for pollination (plants)
• Parts of an Insect-Pollinated Flower

  • Sepals
  • Petals
  • Stamens
  • Filaments
  • Anthers
  • Carpels
  • Style
  • Stigma
  • Ovary
  • Ovules
• Pollination


  Transfer of pollen grains from the male part of the plant (anther of stamen) to the female part of the plant (stigma)
• Agents of Pollination


  • Insects
  • Birds
  • Mammals
  • Water
  • Wind
• Fertilisation (in plants)


  Occurs when a pollen nucleus fuses with a nucleus in an ovule
• Characteristics of Insect-Pollinated Flowers

  • Bright, colourful petals – attract
  • Sweetly scented
  • Contains nectar
  • A moderate amount of pollen
  • Pollen is spiky/sticky
  • Anther & stigma inside the flower
  • Sticky stigma
• Characteristics of Wind-Pollinated Flowers

  • Dull petals
  • No scent
  • No nectaries
  • Huge amount of pollen
  • Pollen round and smooth
  • Anther and Stigma hang out
  • Feathery stigma
• Pollen Tube Formation


  Pollen grain lands on the stigma and creates a tunnel down the style, through the micropyle, to the ovules
• Self-Pollination


  The transfer of pollen grains from the anther of a flower to the stigma of the same flower or a different flower on the same plant
• Advantages of Self-Pollination


  • Genetically identical
  • High chance of successful pollination
  • Fast and saves time
• Disadvantages of Self-Pollination


  • Lack of genetic variation
  • Increases competition between plants
  • Susceptible to the same disease
• Cross-Pollination


  The transfer of pollen grains from the anther of a flower to the stigma of a flower on a different plant of the same species
• Advantages of Cross-Pollination


  • Increases variation
  • Quick to adapt to surroundings
  • Less susceptible to diseases
• Disadvantages of Cross-Pollination


  • Reliance on pollinators
  • Wastage of pollen
  • More energy required
• Germination


  1. Water activates enzymes to turn insoluble food stores into soluble substances, and makes tissues swell so that the testa splits

  2. Oxygen enters through the gaps in the testa (along with water), and is used in aerobic respiration

  3. Temperature must be suitable for enzymes to work (at optimum temperature)
• Male Reproductive System


  • Testes
  • Scrotum
  • Sperm duct
  • Prostate gland
  • Urethra
  • Penis
• Female Reproductive System


  • Ovary
  • Oviduct (fallopian tube)
  • Uterus (womb)
  • Cervix
  • Vagina
• Fertilisation and Early Development

  1. One sperm penetrates

  2. The ovum membrane alters to form a barrier against sperm

  3. The head of the sperm (male nucleus) approaches and then fuses with the nucleus of the ovum

  4. The zygote divides over and over to make a ball of cells called an embryo

  5. It implants itself in the uterus (implantation) wall, followed by conception
• Development of Fetus


  1. The zygote is changed through growth (mitosis) and development (organisation of cells into tissues and organs)

  2. Umbilical cord contains the umbilical artery, which carries deoxygenated blood and waste products from the fetus to the placenta and the umbilical vein, which carries oxygenated blood and soluble food from the placenta to the fetus

  3. Placenta is the organ for exchange of soluble materials such as foods, wastes and oxygen between mother and fetus; physical attachment between uterus and fetus

  4. Amniotic Sac is the membrane which encloses amniotic fluid, broken at birth

  5. Amniotic Fluid protects the fetus against mechanical shock, drying out and temperature fluctuations
• Some pathogens and toxins can pass across the placenta and affect the fetus
• Sperm (Male Gamete)


  • Small in size
  • Elongated and streamlined with energy storage
  • Millions in numbers containing 23 chromosomes
• Egg Cell (Female Gamete)


  • Larger in size
  • Spherical protein/fat in the cytoplasm
  • Moved with the help of Cillia
  • Released once per month containing 23 chromosomes
• Primary Sexual Characteristics


  Present during development in the uterus and are the differences in reproductive organs etc., between males and females
• Secondary Sexual Characteristics


  The changes that occur during puberty as children become adolescents
• Menstrual Cycle


  1. Day 1 to 5: FSH secreted by the Pituitary Gland to stimulate the maturation of ONE follicle in the ovary, endometrium breaks down; menstruation

  2. Day 5 to 12: The follicle keeps maturing, oestrogen is secreted by follicle and the ovarian tissues to prepare the endometrium

  3. Day 13/14/15: LH is also secreted by the Pituitary Gland to trigger the release of the egg from the follicle into the fallopian tube. Ovulation happens on Day 14

  4. Day 15 to 28: LH triggers the formation of Corpus Luteum, progesterone is secreted by Corpus Luteum to keep endometrium thick, waiting for possible embryo implants

  5. Day 28 - Scenario 1: No implantation takes place, and the Corpus Luteum degenerates, causing a lack of progesterone, endometrium is no longer thick, back to Day 1

  6. Day 28 - Scenario 2: Implantation occurs, hormones keep the Corpus Luteum maintained, progesterone is high, endometrium thick for pregnancy
• Hormones in Menstrual Cycle

  • Oestrogen
  • Progesterone
  • Follicle-stimulating hormone (FSH)
  • Luteinizing hormone (LH)
• Human Immunodeficiency Virus (HIV)


  A sexually transmitted infection that infects and destroys lymphocytes, decreasing the efficiency of the immune system, making the body liable to infection by other pathogens, which may lead to AIDS and death from infection
• HIV is transmitted through intercourse, blood transfusion, organ transplant or sharing a needle with an infected person
•  and ResponseMammalian Nervous System

  • The mammalian nervous system consists of two parts:
  • Central Nervous System (CNS) consists of the brain and spinal cord, which are the areas of coordination.
  • Peripheral Nervous System (PNS) comprises nerves and neurones, which coordinate and regulate body functions.
  • Electrical impulses travel through the neurones.
  • The nervous system helps with the coordination and regulation of body functions.

  Types of Neurones

  Nerve Impulse: an electrical signal that passes along the nerve cells called neurones