Biology Notes

Soil and Plants

• Decomposed plant tissue enriches the soil, improving its water and nutrient retention, which boosts fertility.
• Plant roots bind the soil, which protects against erosion from wind and water.

Plants and Atmosphere

• Plants play a crucial role in maintaining the atmosphere.
• Photosynthesis in plants produces oxygen as a byproduct, which continually replenishes atmospheric oxygen.

Food Webs

• Food webs illustrate the interactions between different organisms across trophic levels.
• Arrows in a food web indicate the flow of energy from a consumed organism to its consumer.
• All producers and consumers in an ecosystem eventually decompose, providing nourishment for decomposers like fungi and microbes.

Vaccination

• Immunization is a procedure used to induce immunity.
• Active immunization involves vaccines containing antigens, which elicit a primary immune response and provide lasting protection.
• Passive immunization involves administering antibodies purified from the blood of other individuals, offering immediate but temporary protection.

HIV and AIDS

• The HIV virus targets and destroys the immune system by infecting macrophages, dendritic cells, and helper T cells.
• AIDS (Acquired Immune Deficiency Syndrome) is a collection of diseases that emerge as HIV weakens the immune system.
• Antiretroviral drugs can slow the progression of HIV by targeting processes essential for viral replication.

Global HIV/AIDS Statistics (2017)

• Southern Africa: 19,600,000 people living with HIV/AIDS.
• Eastern Africa: 6,100,000 people living with HIV/AIDS.
• Western and Central Europe and North America: 2,200,000 people living with HIV/AIDS.
• Latin America: 1,800,000 people living with HIV/AIDS.
• Eastern Europe and Central Asia: 1,400,000 people living with HIV/AIDS.
• Caribbean: 310,000 people living with HIV/AIDS.
• Middle East and North Africa: 220,000 people living with HIV/AIDS.
• Worldwide Total: 38,000,000 people living with HIV/AIDS and 940,000 AIDS-related deaths.
• Source: Joint United Nations Programme on HIV/AIDS (UNAIDS) 2017 report.

Immunodeficiency

• Immunodeficiency refers to insufficient immune function, which makes individuals susceptible to opportunistic infections.
• Primary immune deficiencies (e.g., SCIDs) are congenital.
• Secondary immune deficiencies result from exposure to agents like the HIV virus.

Plant Reproduction

• Monoecious plants have both male and female reproductive structures on the same flower or plant.
• Dioecious plants have male and female reproductive structures on separate plants.

Double Fertilization

• Double fertilization is unique to angiosperms.

Flower Structure

• Perfect flowers have both male and female floral organs.

Immune System Malfunctions

• Even minor immune system failures can significantly impact health, leading to allergies, overly vigorous immune responses, autoimmune disorders, and immunodeficiency.

Overly Vigorous Immune Responses

• Asthma and septic shock: Conditions where excessive neutrophil degranulation or cytokine release leads to widespread inflammation and potential organ failure.
• Autoimmune response: An immune response that targets the body's own tissues, (e.g., multiple sclerosis, where T cells attack nerves).

Allergies

• Allergen: A normally harmless substance that triggers an immune response.
• Allergy: Can be an antibody-mediated response (respiratory allergies) or a cell-mediated response (contact allergies).
• Anaphylactic shock: A severe, life-threatening, whole-body reaction to allergens, causing excessive fluid leakage into tissues, a drop in blood pressure, and tissue swelling.

Adaptive Immunity Characteristics

• Self/Nonself Recognition: T cell receptors recognize MHC molecules and antigens to distinguish between self and nonself.
• Specificity: Adaptive immune responses target specific antigens.
• Diversity: Lymphocytes possess a wide variety of antigen receptors.
• Memory: The immune system can "remember" antigens through memory cells.

Short-Term and Long-Term Immune Responses

• Effector cells: Act immediately in a primary immune response.
• Memory cells: Long-lived lymphocytes reserved for future encounters with the same threat; they can persist for decades after a primary response.

Adaptive Immune Responses

• Antibody-mediated immune response: Antibodies are produced in response to an antigen.
• Cell-mediated immune response: Cytotoxic T cells and NK cells destroy infected or cancerous body cells.

Antigen Processing

• T cell receptors recognize antigen presented by antigen-presenting cells (APCs) like macrophages, B cells, or dendritic cells.
• A T cell with matching receptors binds to the antigen-MHC complex on the APC.
• This binding triggers the secretion of cytokines, which signal all B and T cells with matching receptors to divide and produce effector and memory cells.

Antigen Receptor Diversity

• Humans can produce billions of unique B and T cell receptors.
• Genes encoding these receptors are composed of several segments that are spliced together during B and T cell differentiation.
• B and T lymphocytes, like all blood cells, form in bone marrow.

Immune Cell Receptors and Self Markers

• B cell receptors: Antibodies that remain attached to the B cell's plasma membrane.
• T cell receptor (TCR): Antigen-binding receptor on the surface of T cells.
• MHC markers: Self-recognition proteins on the surface of body cells that trigger an adaptive immune response when bound to antigen fragments.

Antigen Receptors

• Antigen receptors recognize specific antigens.
• PAMPS
• Antibodies.

Antibody

• Antibody: Y-shaped antigen receptor protein produced by B cells.
• Binds to antigens with complementary shape and charge.
• Activates complement and facilitates phagocytosis.

Angiosperm Defenses

• Angiosperms employ various defense mechanisms:
  • Physical defenses such as thorns, spines, and resins.
  • Chemical defenses in the form of poisonous or distasteful plant tissues.

Seed Dispersal

• Seeds are dispersed through various methods:
  • Some seeds can pass through the digestive tract unharmed.
  • Burrs cling to animal fur.
  • Winged fruits are carried by air.

Seed Development

• The fertilized ovule develops into a seed.
• The seed is dispersed and germinates to form a sporophyte plant.

Plant Benefit from Animals

• Animals benefited by eating some of the protein-rich pollen
• Plants benefited by using animals as pollinators

Innate Immunity

*What happens when the surface defenses are down or not working properly?

• Innate immunity can stop or slow pathogens.

Physical Barriers

• Muted by cells of nasal epithelium

Gymnosperms

*Cells within each ovule undergo meiosis to
produce haploid female gametophytes

• The female gametophytes produce egg cells
  *They produce pollen (the male gametophytes) by
  meiosis
  *The pollen is dispersed by the wind
  *The pollen grain germinates and forms a pollen tube
  it lands near a female gametophyte
  The pollen tube slowly burrows into the female gametophyte (a process that may take 14 months)

Plant Adaptations

• Retention of green leaves throughout the year (evergreens).
• Thin, needle-like leaves covered with waterproofing material to reduce evaporation.
• An "antifreeze" in their sap, enabling them to continue transporting nutrients in below-freezing temperatures.

Welwitschia

• Welwitschia has a deep taproot that can extend as far as 100 feet down into the soil.
• Above ground, it has only a stem and two leaves, which remain on the plant for its entire life and may last for 2,000 years.
• The strap-like leaves continue to grow for that entire period, spreading over the ground.

Ephedra

• Leaves of the Ephedra species contain alkaloid compounds used as stimulants and appetite suppressants.

Innate vs. Adaptive Immunity

Seed Structure

• Seeds have three components: an embryonic sporophyte plant, a food supply for the embryo, and a protective outer coat.

Seed plant advantage

• They eliminate the need for sperm to swim to the egg

Seed Dispersal

*The seeds are dispersed by the wind
*Fertilization occurs and the seed develops
*Seeds are released when the cone is mature
After landing in a suitable place, the spore
germinates and develops into a gametophyte
The spores are dispersed by the wind
structures called sporangia

Cervical Cancer and HPV

• Healthy cervical cells can be transformed into cancerous ones by human papillomavirus (HPV).
• Vaccines like Gardasil protect against infection by types of genital HPV commonly associated with cervical cancer.
• Early detection through annual exams and Pap smears is crucial in preventing cervical cancer.

Spleen Function

• The spleen functions to immunologically filter the blood and allow for communication between cells corresponding to the innate and adaptive immune responses.

Inflammatory Response

*White blood cells (leukocytes) release chemicals to stimulate the inflammatory response following a cut in the skin.

Immune system

*There are two main parts to the vertebrate immune system. The innate immune system, which is made up of physical barriers and internal defenses, responds to all pathogens. The adaptive immune system is highly specific.
Viruses are the cause of dozens of ailments in humans, ranging from mild illnesses to serious diseases.