Pathogens and Disease Overview

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Questions and Answers

Explain how the body's first line of defense protects against pathogens.

The body's first line of defense involves mechanical barriers like skin and hairs in the nose, as well as chemical barriers like mucus, stomach acid, and tears. These barriers prevent pathogens from entering the body.

What is the role of antigens in the immune response?

Antigens on a pathogen's surface act as markers that are recognized by white blood cells. These white blood cells then trigger an immune response to eliminate the pathogen.

Describe the process of antibody-antigen complex formation and its significance.

Antibodies, produced by lymphocytes, have specific complementary shapes that bind to antigens on pathogens. This binding forms an antibody-antigen complex, effectively neutralizing the pathogen by clumping them together and making them easier to destroy by phagocytes.

How does active immunity develop after an infection?

<p>After an infection, some lymphocytes become memory cells. These memory cells remember the specific pathogen and can quickly produce antibodies if the same pathogen enters the body again, providing long-term immunity.</p> Signup and view all the answers

What is the purpose of vaccination?

<p>Vaccination introduces a weakened or inactivated version of a pathogen or its antigens into the body, stimulating an immune response without causing the disease. This allows the body to develop memory cells and provide long-term immunity against the specific pathogen.</p> Signup and view all the answers

Explain how hygiene measures help prevent the spread of disease.

<p>Hygiene measures such as proper food preparation, waste treatment, clean water supply, and good personal hygiene limit the spread of pathogens by reducing their transmission through contaminated surfaces, foods, animals, and air.</p> Signup and view all the answers

Describe two ways pathogens can be transmitted from one host to another.

<p>Pathogens can be transmitted through direct contact, involving the transfer of bodily fluids like blood, or indirectly through contaminated surfaces, foods, animals, or air.</p> Signup and view all the answers

Why is it important that each pathogen has a specific antigen?

<p>Each pathogen has a unique antigen, which is essential for the immune system to recognize and target that specific pathogen. The uniqueness of antigens allows for the production of specific antibodies that bind only to that particular pathogen, ensuring effective immune response against it.</p> Signup and view all the answers

Explain how vaccination contributes to herd immunity and why this is important.

<p>Vaccination helps create herd immunity by making a large portion of the population immune to a specific pathogen. This makes it difficult for the disease to spread because there are fewer susceptible individuals for the pathogen to infect. This protects those who cannot be vaccinated, ensuring they remain safe from the disease.</p> Signup and view all the answers

Differentiate between passive and active immunity, providing examples of each.

<p>Active immunity is long-term and acquired through exposure to a pathogen or vaccination. This involves the body producing its own antibodies. Examples include recovering from a disease or getting a vaccine. Passive immunity is short-term and involves receiving antibodies from another source, like a mother's milk or an antibody injection. It provides immediate protection but is not long-lasting.</p> Signup and view all the answers

Explain why antibiotics are ineffective against viral infections.

<p>Viruses lack the cellular structure and replication mechanisms of bacteria. This means antibiotics, which target bacterial cell walls or metabolic processes, have no effect on viruses.</p> Signup and view all the answers

Describe the process of antibiotic resistance development, explaining the role of natural selection.

<p>Antibiotic resistance arises when bacteria develop mutations that make them impervious to a particular antibiotic. When this antibiotic is administered, the resistant bacteria survive and reproduce, passing on the resistance gene to their offspring. This leads to a population dominated by resistant bacteria, challenging the effectiveness of antibiotics.</p> Signup and view all the answers

Explain two ways to help slow the development of antibiotic resistance.

<p>Two key strategies to combat antibiotic resistance include: 1) Limiting antibiotic use to serious infections only. This reduces unnecessary exposure to antibiotics and limits the selective pressure on bacteria to develop resistance. 2) Completing the full course of antibiotics as prescribed. This ensures the eradication of all susceptible bacteria, reducing the risk of surviving bacteria developing and spreading resistance.</p> Signup and view all the answers

Explain the main difference between asexual and sexual reproduction.

<p>Asexual reproduction involves a single parent producing genetically identical offspring, while sexual reproduction requires two parents and produces genetically diverse offspring.</p> Signup and view all the answers

List three advantages of sexual reproduction over asexual reproduction.

<p>Advantages of sexual reproduction include 1) greater genetic diversity, making populations more resilient to disease and environmental challenges. 2) Increased adaptability, as new combinations of genes can arise providing beneficial traits for survival. 3) Reduced risk of extinction, as genetic diversity allows for greater resilience to pathogens and changing environments.</p> Signup and view all the answers

Describe two disadvantages of asexual reproduction.

<p>Asexual reproduction can lead to 1) a lack of diversity, making the population vulnerable to disease outbreaks and environmental changes. 2) Increased risk of extinction, as all individuals are genetically identical, a single disease can wipe out the entire population.</p> Signup and view all the answers

Explain the role of gametes in sexual reproduction.

<p>Gametes are specialized sex cells (sperm and eggs) that contain half the number of chromosomes from each parent. They fuse during fertilization, combining their genetic material to form a zygote, the first cell of a new organism.</p> Signup and view all the answers

Why is fertilization important in sexual reproduction?

<p>Fertilization is the fusion of two haploid gametes, combining their genetic material to produce a diploid zygote, restoring the full set of chromosomes. This process is essential for sexual reproduction, ensuring genetic diversity in offspring.</p> Signup and view all the answers

Describe the arrangement of stigmas and anthers in wind-pollinated flowers, explaining why this arrangement is beneficial.

<p>In wind-pollinated flowers, stigmas extend outside the flower and are feathery to easily catch pollen blown by the wind. Anthers also hang outside the flower allowing pollen to be dispersed by the wind.</p> Signup and view all the answers

Explain the difference between pollination and fertilization.

<p>Pollination is the transfer of pollen grains from an anther to a stigma, while fertilization is the fusion of a male gamete (pollen) with a female gamete (ovule) to form a zygote.</p> Signup and view all the answers

Define cross-pollination and explain why it is beneficial for plant reproduction.

<p>Cross-pollination occurs when pollen grains from one plant are transferred to the stigma of another plant of the same species. This promotes genetic diversity, leading to variations in offspring and increasing their ability to adapt to changing environments.</p> Signup and view all the answers

Describe two ways to increase the chances of cross-pollination in plants.

<p>Two strategies to enhance cross-pollination include: 1) Planting a variety of different plants within the same area to increase the likelihood of pollen transfer. 2) Encouraging insect or wind activity, which can act as pollen carriers and promote cross-pollination.</p> Signup and view all the answers

Explain why it is important for babies to be breastfed.

<p>Breastfeeding provides babies with passive immunity through antibodies transferred from the mother's milk, protecting them from various diseases during their early developmental stages.</p> Signup and view all the answers

What is the advantage of cross-pollination over self-pollination in terms of species adaptation?

<p>Cross-pollination leads to greater genetic diversity, making the species more adaptable and resilient to diseases.</p> Signup and view all the answers

Describe two structural adaptations found in insect-pollinated flowers that aid in attracting pollinators.

<p>Insect-pollinated flowers have large, bright, and scented petals to attract insects. They also produce nectar, a sugary liquid, as a reward for insect pollinators.</p> Signup and view all the answers

What is the main difference in the anther structure of wind-pollinated and insect-pollinated flowers?

<p>In wind-pollinated flowers, the anther is outside the flower and hangs loosely to easily release pollen grains into the wind. Insect-pollinated flowers have anthers inside the flower attached firmly to the petals to brush against insects.</p> Signup and view all the answers

Explain the process of fertilisation in plants, starting with the pollen grain landing on the stigma.

<p>After landing on the stigma, a compatible pollen grain germinates, growing a pollen tube towards the ovule. The pollen nucleus travels down the tube, fusing with the ovule's nucleus in the process of fertilization.</p> Signup and view all the answers

Name two essential factors that contribute to seed germination, and explain their roles.

<p>Water is necessary for seed germination as it causes the seed to swell and allows the embryo to begin growing. Oxygen is needed for respiration, providing energy for the growing embryo.</p> Signup and view all the answers

What is the primary function of the testes in the male reproductive system?

<p>The testes produce sperm cells, the male gametes, as well as testosterone, the primary male sex hormone.</p> Signup and view all the answers

What is the role of the oviducts in the female reproductive system?

<p>Oviducts connect to the ovaries and transport the egg cells through the tubes using cilia. Fertilization also takes place in the oviducts.</p> Signup and view all the answers

Describe the process of fertilisation in humans, including the role of sperm cell adaptations.

<p>Fertilization occurs when a sperm cell fuses with an egg cell. Sperm cells have a tail-like flagellum for motility and numerous mitochondria to provide energy for swimming towards the egg. Enzymes in the acrosome break down the egg's outer layer, allowing the sperm to fuse with the egg nucleus.</p> Signup and view all the answers

What are the major differences in size, motility, and number between sperm cells and egg cells?

<p>Sperm cells are very small, motile with a flagellum, and produced in large numbers. Egg cells are large, immobile, and only one is released each month.</p> Signup and view all the answers

Explain how HIV affects the immune system and leads to AIDS.

<p>HIV infects lymphocytes, which are crucial for immune function. It replicates within these cells, impairing their ability to fight infection. The loss of lymphocytes leads to a weakened immune system, making the individual susceptible to various infections, ultimately resulting in AIDS.</p> Signup and view all the answers

What are three ways to control the spread of STIs?

<p>Abstaining from sexual contact, practicing safe sex by avoiding high-risk practices, and using protection like condoms can effectively reduce the risk of STI transmission.</p> Signup and view all the answers

What is the difference between self-pollination and cross-pollination?

<p>Self-pollination occurs when pollen from the anther of a flower reaches the stigma of the same flower or another flower on the same plant. Cross-pollination involves pollen transfer from the anther of one plant to the stigma of a flower on a different plant.</p> Signup and view all the answers

Why are insect-pollinated flowers more likely to have brightly coloured petals and a strong scent compared to wind-pollinated flowers?

<p>Insect-pollinated flowers rely on attracting insects for pollination, so they have evolved to have bright colours and strong scents to entice insects to visit and transfer pollen.</p> Signup and view all the answers

What is the role of the acrosome in a sperm cell during fertilization?

<p>The acrosome contains enzymes that digest the outer layer of the egg cell, enabling the sperm nucleus to penetrate and fuse with the egg nucleus to complete fertilization.</p> Signup and view all the answers

How does the zygote develop after fertilization?

<p>The zygote undergoes repeated cell division through mitosis, forming a ball of cells known as the embryo. The embryo then implants into the uterine wall where it continues to grow and develop.</p> Signup and view all the answers

What is the function of the jelly coat surrounding the egg cell?

<p>The jelly coat of the egg cell changes after fertilization. This change prevents additional sperm cells from penetrating the egg, ensuring that only one sperm cell fuses with the egg nucleus.</p> Signup and view all the answers

Flashcards

Pathogen

An organism that causes disease, like bacteria or viruses.

Host

An organism that harbors a pathogen.

Transmissible diseases

Diseases that can be spread from host to host.

Direct contact transmission

Spread of pathogens through blood and body fluids.

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Indirect transmission

Spread of pathogens from surfaces, foods, animals, and air.

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Immune response

The body's reaction to kill pathogens after infection.

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Active immunity

Immunity that develops through antibody production by the body after infection or vaccination.

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Memory cells

Lymphocytes that stay in the body to recognize past pathogens for quicker responses.

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Self-pollination

The process where a flower transfers pollen from its anther to its own stigma.

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Cross-pollination

The transfer of pollen from one flower to the stigma of another flower of the same species.

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Genetic diversity

Variation in genetic characteristics within a species.

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Insect-pollinated flowers

Flowers adapted to attract insects, featuring bright petals and nectar.

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Wind-pollinated flowers

Flowers that rely on wind for pollen transfer, often with small, dull petals.

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Fertilisation in plants

The process where pollen nuclei fuse with ovule nuclei to form a zygote.

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Factors for seed germination

Conditions like water, oxygen, and temperature that affect a seed's ability to sprout.

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Male reproductive system

Organ systems including testes, scrotum, and urethra, responsible for sperm production and delivery.

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Female reproductive system

Organ systems including ovaries and uterus, responsible for egg development and embryo growth.

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Zygote

The cell formed when a sperm cell fertilizes an egg cell.

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Sexually transmitted infections (STIs)

Infections transmitted through bodily fluids during sexual activity.

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HIV

A virus causing AIDS, transmitted through bodily fluids and affecting the body's immune system.

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Acrosome

A cap-like structure on sperm that contains enzymes to digest the egg's outer layer.

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Embryo

An early stage of development formed from a zygote, implanted in the uterus.

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Oviducts

Tubes connecting ovaries to the uterus, where fertilization occurs.

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Antigens

Substances that evoke an immune response among lymphocytes.

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Herd Immunity

When a large part of a population is immune, protecting those who are not vaccinated.

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Passive Immunity

Short-term immunity gained by receiving antibodies from another person.

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Antibiotics

Drugs used to treat bacterial infections, either by killing bacteria or inhibiting their growth.

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Antibiotic Resistance

When bacteria evolve to survive antibiotics that once killed them.

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Asexual Reproduction

Reproduction that results in genetically identical offspring from one parent.

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Advantages of Asexual Reproduction

Includes needing only one parent, fast reproduction, and less energy required.

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Disadvantages of Asexual Reproduction

Lack of genetic diversity leading to vulnerability to extinction.

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Sexual Reproduction

Involves two parents and produces genetically diverse offspring through gametes.

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Advantages of Sexual Reproduction

Includes wide diversity and the ability to adapt through natural selection.

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Disadvantages of Sexual Reproduction

Includes needing a mate and producing fewer offspring compared to asexual methods.

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Pollination

The transfer of pollen grains from an anther to a stigma in plants.

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Study Notes

Pathogens and Disease

  • Pathogens are organisms that cause disease. Examples include bacteria and viruses.
  • Hosts are organisms that harbour pathogens.
  • Transmissible diseases are those that can be passed from host to host.
  • Pathogens can be transmitted directly (e.g., blood/body fluids) and indirectly (contaminated surfaces, food, animals, air).

Preventing Disease Transmission

  • Hygiene practices (food preparation, waste management, water supply) are crucial to prevent disease transmission.
  • Maintaining good personal hygiene is essential.

Body's First Line of Defense

  • Mechanical barriers (e.g., nose hairs, skin) prevent pathogen entry.
  • Chemical barriers (e.g., mucus, stomach acid, tears) also defend against pathogens.

Immune Response (Second Line)

  • When pathogens enter, the body mounts an immune response to destroy them.
  • Phagocytosis and antibody production by white blood cells are part of the response.

Antibodies and Antigens

  • White blood cells detect pathogens.
  • Each pathogen has specific antigen proteins on its surface.
  • Lymphocytes produce specific antibodies that bind to these antigens.
  • Antibodies have shapes that only fit specific antigens.
  • The antibody-antigen complex forms, clumping pathogens and either directly killing them or marking them for phagocyte destruction.

Active Immunity

  • Active immunity involves the body producing antibodies in response to a pathogen.
  • It can be acquired through infection or vaccination.
  • Memory cells are created after initial infection to provide long-term immunity.

Vaccination

  • Vaccination introduces a dead or weakened pathogen or its antigens.
  • The antigens stimulate an immune response from lymphocytes.
  • Memory cells are generated, providing long-term immunity.
  • Herd immunity occurs when a large proportion of the population is vaccinated protecting those unable to be vaccinated.

Passive Immunity

  • Passive immunity is short-term immunity acquired from another individual.
  • Antibodies from a mother to her baby via breast milk are one example.
  • It can also be achieved through antibody injections.
  • Passive immunity does not generate memory cells.

Drugs and Antibiotics

  • Drugs affect chemical reactions in the body.
  • Antibiotics treat bacterial infections.
  • Some antibiotics destroy cell walls. Others inhibit bacterial growth.
  • Viruses do not respond to antibiotics because their structure and reproduction are different from bacteria.

Antimicrobial Resistance

  • Some bacteria develop resistance to antibiotics via natural selection.
  • Resistance results in infections like MRSA.
  • Precautions are necessary to control antibiotic resistance development (e.g., appropriate use, completion of courses).

Asexual Reproduction

  • Asexual reproduction creates genetically identical offspring (clones).
  • It involves only one parent.
  • Common in plants but also seen in some animals like starfish.

Advantages and Disadvantages of Asexual Reproduction

  • Advantages: Rapid reproduction, less energy required, suitable for barren environments.
  • Disadvantages: Reduced diversity leading to potential vulnerability to diseases and environmental changes. Overpopulation is a possible result

Sexual Reproduction

  • Sexual reproduction needs two parents.

Sexual Reproduction in Plants

  • Pollination is the transfer of pollen from anther to stigma.
  • Cross-pollination occurs between different plants.
  • Self-pollination involves pollen transfer from one part of a plant to another (on the same plant).

Comparing Cross-Pollination and Self-Pollination

  • Cross-pollination: Increases genetic diversity, resilience to diseases. Requires pollinators.
  • Self-pollination: Less energy, can spread to new areas without pollinators but genetic diversity is limited.

Structural Adaptations for Different Pollination Mechanisms

  • Insect-pollinated flowers: large, brightly colored, scented petals; sticky stigma; nectar production.
  • Wind-pollinated flowers: small, dull petals, feathery stigma; anthers hanging outside to easily release pollen.

Fertilization Process in Plants

  • Pollen lands on stigma, a pollen tube grows.
  • The pollen moves to the ovule, fertilizing it.
  • A zygote is formed, developing into an embryo plant.

Factors Affecting Seed Germination

  • Water: Seed swelling initiates growth.
  • Oxygen: Supports respiration to fuel growth.
  • Temperature: Optimal temperature allows enzymes to support growth.

Male Reproductive System

  • Testes: Produce sperm and testosterone.
  • Scrotum: Houses the testes.
  • Sperm ducts: Transport sperm to the urethra.
  • Prostate gland: Produces semen.
  • Urethra: Excretes urine and semen.
  • Penis: Delivers semen to the vagina during sexual intercourse.

Female Reproductive System

  • Ovaries: Mature egg cells.
  • Oviducts (Fallopian tubes): Transport eggs, fertilization occurs here.
  • Uterus: Houses the developing embryo.
  • Cervix: Separates the uterus from the vagina.
  • Vagina: Receives the penis during intercourse.

Fertilization

  • Fusion of sperm and egg nuclei is fertilization.
  • Sperm - small, mobile, with flagella for movement, lots of mitochondria for energy, enzymes in the acrosome to penetrate the egg.
  • Egg - much larger, immobile.
  • Jelly coat changes after one sperm penetration.
  • The zygote develops into an embryo through mitosis.

Comparing Male and Female Gametes

  • Sperm: small, mobile, many produced daily.
  • Egg: large, immobile, one released per cycle.

Sexually Transmitted Infections (STIs)

  • STIs are transmitted via bodily fluids during sexual contact.
  • Control measures include abstinence, safe practices, and protective measures.

HIV (Human Immunodeficiency Virus)

  • HIV is an STI caused by a pathogen.
  • HIV infects lymphocytes (white blood cells).
  • HIV replication damages lymphocytes, reducing the body's ability to fight infections.
  • HIV leads to AIDS, making the individual susceptible to other pathogens and infections.

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