Pathogens and Disease Transmission Quiz

Pathogens and Disease Transmission

• Pathogens are organisms causing diseases, including bacteria and viruses.
• Hosts are organisms harboring these pathogens.
• Transmissible diseases are those spread from host to host.
• Transmission methods include direct contact (blood, body fluids) and indirect contact (contaminated surfaces, food, animals, air).
• Disease prevention requires hygienic food preparation, waste treatment, clean water, and good personal hygiene.

Body's Defenses Against Infection

• The first line of defense prevents pathogen entry:
  • Mechanical barriers: nose hairs, skin.
  • Chemical barriers: mucus, stomach acid, tears.
• Upon infection, an immune response kills pathogens:
  • Phagocytosis (engulfing and destroying pathogens).
  • Antibody production by white blood cells (lymphocytes).

Antibodies and Antigens

• White blood cells detect pathogens and trigger an immune response.
• Each pathogen has unique antigen proteins on its surface.
• Lymphocytes produce specific antibodies that bind to antigens, forming antibody-antigen complexes.
• Antibodies have shapes complementary to specific antigens, thus tailored to each pathogen.
• The antibody-antigen complex clumps the pathogens, making them harmless and enabling phagocyte destruction.

Active Immunity

• Active immunity is antibody production in response to a pathogen.
• It can be acquired through infection or vaccination.
• Memory lymphocytes remain after pathogen destruction.
• Memory cells recognize repeated pathogens, leading to faster antibody production.
• Memory cells provide long-term immunity.

Vaccination

• Vaccination introduces a dead or weakened pathogen or antigen.
• Antigens trigger lymphocyte immune response and antibody production.
• Memory cells are generated, resulting in long-term immunity.
• Herd immunity occurs when a significant portion of the population is vaccinated, protecting the unvaccinated.

Passive Immunity

• Passive immunity is short-term, gained from acquiring antibodies.
• Breastfeeding passes antibodies from mother to baby.
• Antibodies can also be injected from donors or from a pregnant mother to the baby through the placenta.
• Passive immunity lacks memory cells and is therefore short-term.

Antibiotics

• Antibiotic drugs treat bacterial infections.
• Some antibiotics destroy bacterial cell walls, others inhibit bacterial growth.
• Viruses cannot be killed by antibiotics due to their different structure and reproduction mechanism.
• Antibiotic resistance arises via natural selection.
• Resistance occurs when a mutation confers antibiotic resistance.
• Resistant bacteria survive and reproduce, leading to resistant bacterial infections (e.g., MRSA)
• To curb this, use antibiotics only for serious infections, and complete the full course.

Asexual Reproduction

• Asexual reproduction produces genetically identical offspring (clones).
• One parent is required.
• This method is common in plants and some animals (e.g., starfish).
• Advantages include quick reproduction, minimal energy, and adaptability to specific environments.
• Disadvantages include lack of diversity and susceptibility to pathogens and environmental change.
• Overpopulation, resulting in overcrowding, is also a possible outcome.

Sexual Reproduction

• Sexual reproduction requires two parents.
• Gametes (sperm and egg) fuse, forming a zygote with unique genetic makeup.
• Diploid cells have a full set of chromosomes; Haploid cells have half.
• Advantages include genetic diversity, promoting survival and adaptability.
• Disadvantages include requiring two parents, slower reproduction, and higher energy demands.

Sexual Reproduction in Plants

• Pollination (transfer of pollen from anther to stigma) is key for sexual reproduction.
• Cross-pollination (different plants) and self-pollination (same plant) are both forms of sexual reproduction.
• Cross-pollination results in more genetic diversity, thus more resilience to pathogens.
• Self-pollination requires less energy as pollinators are not needed.

Structural Adaptations of Flowers

• Insect-pollinated flowers have large, bright, scented petals and sticky stigmas to attract insects.
• Wind-pollinated flowers have small, dull petals and feathery stigmas for wind dispersal of pollen.

Plant Fertilization

• Pollen lands on the stigma.
• A pollen tube grows.
• Pollen travels through the pollen tube to the ovule.
• Fusion of pollen and ovule nuclei forms zygote, which develops into an embryo.

Seed Germination Factors

• Water is needed for seed swelling and embryo growth.
• Oxygen is required for respiration, producing energy for growth.
• Temperature impacts enzyme activity in the seed and affects germination.

Male Reproductive System

• Testes produce sperm and testosterone.
• Scrotum holds the testes.
• Sperm ducts carry sperm to the urethra.
• Prostate gland produces semen.
• Urethra carries urine and semen.
• Penis delivers semen.

Female Reproductive System

• Ovaries produce egg cells.
• Oviducts transport egg cells toward the uterus.
• Uterus is where the fetus develops.
• Cervix separates the vagina from the uterus.
• Vagina receives sperm during intercourse.

Fertilization

• Sperm (male gamete) and egg (female gamete) fuse nuclei.
• Sperm have tails (flagella) for movement and mitochondria for energy.
• Eggs are large and immobile.
• Enzymes in sperm's acrosome help penetrate the egg's protective coat.
• Fertilization ensures a single sperm enters.
• Zygote development (mitosis) starts from a single-celled zygote to become a multi-cellular embryo.

Comparing Gametes

• Sperm are small and mobile (flagellum).
• Eggs are large and immobile.

Sexually Transmitted Infections (STIs)

• STIs are infections transmitted through bodily fluids during sexual contact.
• Spreading can be controlled by safe sexual practices (e.g., abstinence, protection with condoms).

HIV

• Human Immunodeficiency Virus (HIV) is an STI.
• Transmitted via blood and semen.
• HIV infects and replicates within lymphocytes (white blood cells)
• This reduces the number of functioning lymphocytes.
• Reduces the body's ability to fight disease effectively.
• HIV leads to AIDS (Acquired Immunodeficiency Syndrome).