Reproduction and Food Production Notes

Reproduction

Sexual vs. Asexual Reproduction (3.1)

  • Sexual Reproduction: Involves two parents and the fusion of gametes (sex cells) leading to genetic variation in offspring.
  • Asexual Reproduction: Involves one parent and does not involve the fusion of gametes, producing genetically identical offspring (clones).

Fertilisation and Embryo Development (3.2)

  • Fertilisation: The fusion of a male gamete (e.g., sperm or pollen) and a female gamete (e.g., egg or ovule).
  • Zygote: The diploid cell formed from the fusion of gametes during fertilisation.
  • Embryo: The early stage of development of an organism, formed from the zygote through cell division (mitosis).

Flowering Plants

Flower Structure and Pollination (3.3)

  • Pollination: The transfer of pollen from the stamen (male part) to the pistil (female part) of a flower.
  • Insect-Pollinated Flowers:
    • Characteristics: Brightly colored petals, scented, produce nectar, sticky pollen.
    • Adaptations: These features attract insects, facilitating pollen transfer as insects visit flowers for nectar.
  • Wind-Pollinated Flowers:
    • Characteristics: Small, inconspicuous petals, no scent or nectar, produce large quantities of lightweight pollen.
    • Adaptations: The lightweight pollen is easily carried by the wind to other flowers.

Pollen Tube Growth, Seed, and Fruit Formation (3.4)

  • Pollen Tube: A tube that grows from a pollen grain down the style to the ovary after pollination.
  • Fertilisation in Plants: Occurs when the male gamete from the pollen grain fuses with the ovule inside the ovary.
  • Seed Formation: The ovule develops into a seed after fertilisation.
  • Fruit Formation: The ovary develops into a fruit, which encloses and protects the seed(s).

Seed Germination (3.5)

  • Seed Germination: The process by which a seed develops into a seedling.
  • Conditions Needed: Water, oxygen, and a suitable temperature are essential for seed germination.

Food Reserves in Germinating Seeds (3.6)

  • Food Reserves: Seeds contain stored food (e.g., starch) that provides energy for the developing seedling.
  • Photosynthesis: Once the seedling develops leaves, it can carry out photosynthesis to produce its own food.

Asexual Reproduction in Plants (3.7)

  • Natural Methods:
    • Runners: Stems that grow horizontally along the ground, producing new plants at nodes (e.g., strawberries).
  • Artificial Methods:
    • Cuttings: Pieces of stem or leaf that are cut from a plant and placed in water or soil to develop into new plants.

Humans

Male and Female Reproductive Systems (3.8)

  • Male Reproductive System: Includes testes (produce sperm), vas deferens (transports sperm), seminal vesicles and prostate gland (produce seminal fluid), and penis (for delivering sperm).
    • Adaptations: Testes are located outside the body in the scrotum to maintain a lower temperature for sperm production; penis is adapted for delivering sperm into the female reproductive tract.
  • Female Reproductive System: Includes ovaries (produce eggs), fallopian tubes (where fertilisation occurs), uterus (where the embryo develops), and vagina (receives sperm).
    • Adaptations: Ovaries release eggs into the fallopian tubes; the uterus has a thick lining (endometrium) to support embryo implantation and development.

Oestrogen and Progesterone in the Menstrual Cycle (3.9)

  • Menstrual Cycle: A monthly cycle of hormonal changes in females that prepares the body for pregnancy.
  • Oestrogen:
    • Produced by the ovaries.
    • Causes the thickening of the uterine lining (endometrium).
  • Progesterone:
    • Produced by the ovaries (specifically, the corpus luteum).
    • Maintains the uterine lining and prevents it from breaking down.

FSH and LH in the Menstrual Cycle (3.10B)

  • FSH (Follicle-Stimulating Hormone):
    • Produced by the pituitary gland.
    • Stimulates the development of follicles in the ovaries.
  • LH (Luteinizing Hormone):
    • Produced by the pituitary gland.
    • Triggers ovulation (release of an egg from the ovary) and the formation of the corpus luteum.

Placenta and Nutrition of the Developing Embryo (3.11)

  • Placenta: An organ that develops in the uterus during pregnancy, providing nutrients and oxygen to the developing embryo and removing waste products.
    • It allows the exchange of substances between the mother and fetus's bloodstreams without direct mixing.

Amniotic Fluid and Protection of the Developing Embryo (3.12)

  • Amniotic Fluid: A fluid that surrounds the developing embryo in the amniotic sac.
  • Functions:
    • Protects the embryo from mechanical shock and injury.
    • Maintains a constant temperature.
    • Allows the embryo to move freely.

Oestrogen, Testosterone, and Secondary Sexual Characteristics (3.13)

  • Secondary Sexual Characteristics: Physical traits that develop during puberty and distinguish males from females.
  • Oestrogen (Females):
    • Causes breast development, widening of the hips, and changes in body fat distribution.
  • Testosterone (Males):
    • Causes growth of facial and body hair, deepening of the voice, and increased muscle mass.

Food Production

Glasshouses and Polythene Tunnels (5.1)

  • Glasshouses and Polythene Tunnels: Structures used to control the growing environment for crops.
  • Benefits:
    • Protect crops from adverse weather conditions.
    • Extend the growing season.
    • Increase crop yield.

Effects of Increased Carbon Dioxide and Temperature (5.2)

  • Increased Carbon Dioxide: Enhances photosynthesis, leading to faster growth and increased crop yield.
  • Increased Temperature: Speeds up metabolic processes, promoting growth and development, but must be carefully controlled to avoid heat stress.

Fertiliser Use (5.3)

  • Fertilisers: Substances containing essential nutrients (e.g., nitrogen, phosphorus, potassium) for plant growth.
  • Benefits: Increase crop yield by providing plants with the nutrients they need.

Pest Control (5.4)

  • Reasons for Pest Control: To protect crops from damage and reduce yield losses caused by pests (e.g., insects, weeds, diseases).
  • Pesticides: Chemicals used to kill pests.
    • Advantages: Effective at controlling pests quickly.
    • Disadvantages: Can be harmful to non-target organisms, lead to pesticide resistance, and cause environmental pollution.
  • Biological Control: Using natural enemies (e.g., predators, parasites) to control pests.
    • Advantages: More sustainable and environmentally friendly than pesticides.
    • Disadvantages: May not be as effective as pesticides and can be difficult to implement.

Micro-organisms

Yeast in Food Production (5.5)

  • Yeast (Saccharomyces cerevisiae): A fungus used in the production of bread and other foods.
  • Role in Bread Making: Yeast carries out anaerobic respiration (fermentation), producing carbon dioxide that causes the bread to rise and ethanol.

Anaerobic Respiration by Yeast (5.6)

  • Anaerobic Respiration (in Yeast): The breakdown of glucose in the absence of oxygen, producing ethanol and carbon dioxide.
    • C<em>6H</em>12O<em>6→2C</em>2H<em>5OH+2CO</em>2C<em>6H</em>{12}O<em>6 \rightarrow 2C</em>2H<em>5OH + 2CO</em>2
    • (Glucose → Ethanol + Carbon Dioxide)

Bacteria (Lactobacillus) in Yoghurt Production (5.7)

  • Lactobacillus: Bacteria used to produce yoghurt from milk.
  • Process: Lactobacillus ferments lactose (milk sugar), producing lactic acid, which coagulates the milk proteins and gives yoghurt its characteristic texture and flavour.

Industrial Fermenter (5.8)

  • Industrial Fermenter: A large vessel used to grow microorganisms on a large scale for industrial purposes.
  • Suitable Conditions:
    • Aseptic Precautions: To prevent contamination by unwanted microorganisms.
    • Nutrients: To provide a source of energy and building blocks for growth.
    • Optimum Temperature and pH: For optimal enzyme activity and growth.
    • Oxygenation: To provide oxygen for aerobic respiration (if needed).
    • Agitation: To mix the contents and ensure uniform distribution of nutrients and oxygen.

Fish Farming (5.9B)

  • Fish Farming (Aquaculture): The farming of fish in controlled environments to provide a source of protein.
  • Methods Used:
    • Maintaining Water Quality: Ensuring clean and oxygenated water.
    • Controlling Intraspecific and Interspecific Predation: Preventing fish from preying on each other or other species.
    • Controlling Disease: Preventing and treating diseases to maintain healthy fish populations.
    • Removing Waste Products: Removing uneaten food and faeces to prevent pollution.
    • Controlling the Quality and Frequency of Feeding: Providing a balanced diet at regular intervals.
    • Selective Breeding: Selecting fish with desirable traits (e.g., fast growth, disease resistance) for breeding.

Selective Breeding

Selective Breeding in Plants (5.10)

  • Selective Breeding: The process of selecting plants with desired characteristics (e.g., high yield, disease resistance) and breeding them together to produce offspring with those traits.
  • Process:
    1. Choose parents with desired characteristics.
    2. Breed them together.
    3. Select the best offspring and breed them together.
    4. Repeat the process over several generations.

Selective Breeding in Animals (5.11)

  • Selective Breeding: The process of selecting animals with desired characteristics (e.g., high milk production, fast growth) and breeding them together to produce offspring with those traits.
  • Process: Similar to selective breeding in plants, involving selecting parents with desired traits and breeding them over generations.