Zoology Past Paper PDF

Ecology and population Thursday, November 21, 2024 6:09 PM Recap questions: 1- What is ecology? a. It is the interaction of organisms with their environment and with other organisms 2- List and define the different organization scales in ecology a. Organism: Adaptations to t...

Ecology and population Thursday, November 21, 2024 6:09 PM Recap questions: 1- What is ecology? a. It is the interaction of organisms with their environment and with other organisms 2- List and define the different organization scales in ecology a. Organism: Adaptations to the environment, including morphological, behavioral, physiological b. Population: Factors that shape distributions, density, dynamics c. Community: Interactions among species including predation and parasitism, facilitation, etc. d. Ecosystem: Interactions of populations and communities with their abiotic environment e. Landscape: As above but across ecosystems f. Global: As above but across biomes 3- List some examples of how ecology may be important to human health a. Disease Ecology: Understanding how diseases spread through interactions between hosts, vectors, and the environment, such as malaria or Lyme disease b. Food security: Studying ecological relationships to improve sustainable agriculture and ensure access to nutritious food c. Pollution Impact: Examining how pollutants affect ecosystems and human health, such as water contamination leading to diseases d. Climate change: Investigating ecological shifts due to climate change and their effects on health, like heat stress or vector-borne diseases. e. Biodiversity and Medicine: Exploring how biodiversity contributes to discovering medical compounds and maintaining ecosystem services vital for health f. Natural Disasters: Studying ecosystems to understand and reduce the health impacts of disasters such as floods or wildfires. 4- What typically causes population distributions to be clustered/clumped? Uniform? Randomly Scattered? a. Clumped: aggregate in patches, tends to result from an attractant, such as a suitable habitat patch, a resource, social interactions, aggregating for safety. b. Uniform: evenly spaced, tends to raise from antagonistic interactions among individual organisms, such as territoriality or a chemical inhibiting plant germination (animals defending their territory or plants releasing chemicals that prevent other plants from growing nearby) c. Random: position is independent of the others, tends to arise as a 'random' trajectory in absence of a strong attractions or repulsions. 5- What is life-history 'trade-off'? a. It refers to the balance organisms must strike between competing demands for limited resources, which influence their growth reproduction, and survival. b. Since resources like energy and time are finite, investing in one aspect of life, such as producing many offspring, often comes at the expense of another, like individual growth or long-term survival c. For example: i. Reproduction vs. Survival: an animal that reproduces early and frequently may have less energy to invest in its own survival. ii. Quantity vs. Quality of offspring: Producing many offspring might mean each receives fewer resources, while having fewer offspring allows more investment in each one. 6- Exponential vs logistic population growth. Carrying capacity. a. Exponential population growth: i. Population increases rapidly without any constraints, as if resources are unlimited ii. Shape of growth curve: J-shaped curve iii. Key Feature: Growth accelerates over time because of the constant reproduction rate and compounding effect. Zoology Page 1  compounding effect. iv. Example: Bacteria in a petri dish, reproducing under ideal conditions without resource limitations. b. Logistic Population growth: i. Population growth slows and stabilizes as it approaches the carrying capacity due to resource limitations ii. Shape of growth curve: S-shaped (sigmoid curve) iii. Key feature: Growth rate is initially exponential but decreases as the population nears carrying capacity iv. Example: A deer population in a forest, where food and space are limited c. Carrying Capacity: i. The maximum number of individuals an environment can sustainably support based on resources like food, water, and habitat. ii. Impacts: if it exceeds, it many face resource shortages, leading to a population decline. Population stabilizes around carrying capacity in logistic growth. d. Key difference: exponential growth assumes unlimited resources, while logistic growth incorporates real-world resource limits and carrying capacity. 7- Density-dependent vs density independent controls of population sizes. What are 'negative feedback'? a. Density-dependent: i. Factors that regulate population size based on density ii. Examples: Competition for resources, predation, and disease, which intensify as density increases b. Density-independent: i. Factors that impact population size regardless of density ii. Example: Weather events, natural disasters, or environmental changes c. Negative Feedbacks: i. Processes that stabilize population size by slowing growth as it increases ii. Example: Overcrowding reduces resources, or high predator numbers lower prey populations, balancing ecosystems. Zoology Page 2 The human population Sunday, November 24, 2024 11:33 AM 1- Human population density, past dynamics, distribution: a. Human population density: i. The number of people per unit area, often measured as individuals per square kilometer or mile. ii. Current trends: Unevenly distributed, with higher densities in urban areas like cities and lower densities in rural or extreme environments (deserts, tundra) b. Past dynamics: i. Historical growth: 1) Slow growth for most of human history due to limited resources, high mortality, and diseases. 2) Rapid growth began during the industrial revolution due to technological advancements, improved medicine, and agriculture. ii. Population Milestones: 1) 1800: 1 billion 2) 1900: 1.6 billion 3) 2024: 8 billion iii. Demographic Transitions: 1) Shifts from high birth and death rates to low birth and death rates as societies develop c. Global Distribution: i. Concentration: 1) Most people live in Asia, particularly in countries like China and India 2) Other densely populated regions include Europe and parts of Africa ii. Sparsely Populated Areas: 1) Deserts, mountains, and polar regions iii. Urbanization: 1) Increasing numbers of people live in cities, with over half of the global population residing in urban areas. d. Human population density and distribution are shaped by factors like geography, resources, economy, and technology, leading to clustering in fertile, accessible regions. 2- Future projections: how long is human population growth expected to continue? Aging population. a. Future projections for population growth i. Growth trend: Human population growth is slowing and is expected to reach a steady level by the late 21st century. ii. Peak population: Projections suggest around 10.4 billion people by the 2080s, followed by stabilization or slight decline. iii. Reasons for slowing growth: 1) Declining fertility rates in many regions 2) Urbanization and improved access to education and healthcare, especially for women. 3) Economic development reducing the need for large families b. Aging population: i. A demographic shift where the proportion of older individuals(60+) increases compared to younger age groups ii. Causes: 1) Lower birth rates 2) Increases life expectancy due to advancement in healthcare and living conditions Zoology Page 3  conditions iii. Global Impact: 1) Strain on healthcare and pension systems 2) Workforce shortages in some countries 3) Changing societal structures, with more focus on elder care c. Regional variation: i. Aging populations are more pronounced in developed countries (Japan, Europe), while younger populations remain common in parts of Africa and South Asia 3- Carrying Capacity and ecological footprint, planetary boundaries a. Carrying capacity: i. The maximum number of individuals an environment can support sustainably, given available resources like food, water, and space. ii. Relevance: Populations exceeding carrying capacity can degrade resources, leading to environmental stress and population decline. iii. Human context: Technology and trade can temporarily increase carrying capacity, but overuse of resources may reduce it over time b. Ecological footprint: i. A measure of how much land, water, and resources are required to support an individual, population, or activity, including waste absorption. ii. Key idea: compares human demand to Earth's capacity to regenerate resources iii. Overshoot (living beyond the Earth's ecological "budget"): When humanity's ecological footprint exceeds Earth's biocapacity, leading to resource depletion (deforestation, eater scarcity) c. Planetary Boundaries: i. A framework identifying none critical Earth system processes that regulate the planet's stability and resilience. Staying within these boundaries ensures a "safe operating space" for humanity. ii. Key boundaries: 1) Climate change 2) Biodiversity loss 3) Land-use change 4) Freshwater use 5) Ocean acidification iii. Current Status: Several boundaries, such as climate change and biodiversity, have already been breached, risking global ecological instability. d. Connection: the ecological footprint measures humanity's demand on resources, while carrying capacity reflects Earth's supply. Exceeding planetary boundaries indicates we are surpassing Earth's carrying capacity, threatening long-term sustainability. 4- Socio-economic and health implications: a. Socio-economic implications: i. Carrying capacity: Overpopulation strains resources, causing higher costs, economic instability, migration, and conflicts. ii. Ecological Footprint: Overconsumption worsens global inequalities, pollutes ecosystems, and disrupts trade iii. Planetary Boundaries: Breaching limits harms industries (agriculture), disrupts livelihoods, and risks ecosystem collapse b. Health implications: i. Carrying capacity: Resource shortages leas to hunger, malnutrition, waterborne diseases, and poor sanitation. ii. Ecological Footprint: Pollution causes respiratory and cardiovascular diseases; urban crowding spreads infections. iii. Planetary Boundaries: Climate change intensifies heatwaves, storms, and disease patterns, while resource insecurity impacts mental health. Zoology Page 4 Zoology Page 5 Protists Sunday, November 24, 2024 4:25 PM Lecture notes: Three domains of life 1- Bacteria 2-Archea ]- Prokaryotes 3- Eukarya Eukarya: organisms with a nucleus surrounded by a nuclear envelope and has membrane- enclosed organelles (mitochondria, plastids, Golgi, etc.) What are protists? Eukaryotes that are neither plants, fungi, or animals. They lack highly specialized tissues. Most groups are single-celled. Eukarya 4 supergroups: 1- Excavata: 'Excavated' groove on one side in some a. Diplomonads: Modifies mitochondria, 2 equal sized nuclei. i. Giardia b. Parabasalids: Modified mitochondria, undulating membrane i. Trichomonas c. Euglenozoans: Spiral or crystalline rod inside flagella i. Kinetoplastids: Trypanosoma, Leishmania 2- SAR: Three large diverse clades with DNA Similarities [Stamenoplia, Alveolata, Rhizaria] a. Dinoflagellates, Apicomplexans, Ciliates: Membrane-enclosed sacs beneath plasma membrane (alveoli) i. Apicomplexans: Plasmodium, Cryptosporidium 3- Archaeplastida: Red and Green algae. Arose through primary endosymbiosis. Closely related to plants 4- Unikonta: Have a single emergent flagellum, or are amoebas with no flagella. Closely related to fungi and animals. a. Tubulinids, Slime molds, Entamoebas: Amoebas with lobe-shaped or tube-shaped pseudopodia i. Entamoebas: Entamoeba, Naegleria The protists (Enigmatic (hard to understand) eukaryotes): They are extremely diverse, paraphyletic (Descended from a common evolutionary ancestor or ancestral group, but not including all the descendent groups) assortment of eukaryotes. They are autotrophic, heterotrophic (Relying on energy captured into organic form by autotrophs), or mixotrophic Heterotrophic groups (AKA 'protozoa' are what we are focusing on, all protozoa are unicellular) Protozoa: heterotrophic protists, they are all single-celled. Excavata: Diplomonads and Parabasalids - common features: Mitochondria are highly reduced - they lack DNA, the electron transport chain and enzymes of the citric acid cycle, making it adapted for anerobic metabolism. Most are found in anaerobic environments (lack oxygen) Diplomonads: Small cells with characteristic doubled organization, including two nuclei (= 'eyes') multiple flagella. Many are parasitic Giardia duodenalis (syn. G. intestinalis, G. lamblia): Life cycle stages: Mechanism of infection: ○ Trophozoite: absorbs nutrients from the host (tropho: feeding + Zoite: animal-like) Route: fecal-oral route through ingestion of contaminated water, food, or contact with infected individuals or ○ Cyst: stage with a protective membrane or thickened wall animals. ○ Cyst -> Trophozoites Vector organism: none involved Common intestinal parasite (Giardiasis) Mechanism of the Disease: Coat the intestinal wall, feeding on mucous secretions - affects absorption of fatty acids Part of body affected: small intestine. Giardia attaches to the intestinal lining causing damage to the epithelial cells Causes diarrhea, dehydration, and intestinal pain How it Affects: Leads to malabsorption of nutrients and disruption of the epithelial barrier, resulting in diarrhea, Trophozoites (active feeding stage) and cysts are passed on stool but only cysts are abdominal cramps, and fatigue infective - the trophozoites do no survive in the environments, cysts can remain viable for Diagnosis/Detection: week to months. Cysts are resistant to chlorination and ozonolysis Methods: Diagnosis is by identification of cysts or trophozoites in the feces ○ Stool examination for cysts or trophozoites using microscopy Contamination of water, food, or hands/fomites with infective cysts. ○ Antigen detection assays or molecular tests (e.g., PCR) Infective and Diagnostic Life stages: Infective stage: Cysts (resistant to environmental conditions) Parabasalids: Diagnostic Stage: Trophozoites and cysts in stool samples Undulating membrane used in locomotion (the ability to move) Fibrous 'roots' of flagella (the parabasal fibre) Anaerobic: hydrogenosomes developed from reduces mitochondria All are endosymbionts (live within animals?) of animals Trichomonas vaginalis Life cycle stages: Mechanism of Infection: ○ Trophozoite is the only life-stage form, it cannot encyst (poor survival outside the Route: Direct sexual transmission through contact with infected genital secretions host) Vector organism: none involved ○ Trophozoite (in vaginal and prostatic secretions and urine) Mechanism of the Disease: ○ Multiples by longitudinal binary fission Part of the body affected: Urogenital tract (Vagina, Urethra, Prostate) ○ Trophozoite in vagina or orifice of urethra How it affects: Causes inflammation of the mucosa, leading to symptoms like vaginal discharge, Cosmopolitan parasite, inhabiting the reproductive and urinary tract of men and itching, dysuria, and discomfort women; >160 million people are infected annually worldwide Diagnosis/Detection: Causes infection when acidity of the vagina is disturbed (trichomoniasis): capillary Methods: ○ Microscopic examination of wet mounts to observe motile trophozoites. Zoology Page 6  ○ Multiples by longitudinal binary fission Part of the body affected: Urogenital tract (Vagina, Urethra, Prostate) ○ Trophozoite in vagina or orifice of urethra How it affects: Causes inflammation of the mucosa, leading to symptoms like vaginal discharge, Cosmopolitan parasite, inhabiting the reproductive and urinary tract of men and itching, dysuria, and discomfort women; >160 million people are infected annually worldwide Diagnosis/Detection: Causes infection when acidity of the vagina is disturbed (trichomoniasis): capillary Methods: hemorrhage, burning/itching when urinating. ○ Microscopic examination of wet mounts to observe motile trophozoites. Usually asymptomatic in males ○ Culture or nucleic acid amplification tests (NAATs) for conformation Most common nonviral sexually transmitted infection globally Infective and Diagnostic life stages: Diagnosed from a cervical smear Infective stage: Trophozoite (no cyst stage) Diagnostic stage: Trophozoites in vaginal or urethral secretions Euglenozoans - common features: The flagella contains a spiral or crystalline rod of unknown function (links kinetoplastids and euglenids in this clade) Kinetoplastids: They have a single, large mitochondrion with an organized mass of DNA called a kinetoplast Includes free-living heterotrophs in freshwater, marine, and terrestrial habitats, as well as parasites of animals, plants, and other protists. Trypanosoma are parasites of vertebrate blood that cause trypanosomiasis South America: Africa: Parasite: T. cruzi (you go in a cruise in America) Parasite: T. spp. Disease: Chaga's disease (chaga is so tired Disease: Sleeping sickness from mining) Vector: tsetse flies (Glossina Morsitans) Vector: Triatomine bugs (Rhodnius prolixus) Trypanosoma: Sleeping Sickness: Mechanism of infection: Life cycle stages: (Mastigote: bearing flagella) Route: Bite of an infected tsetse fly (Glossina species) Epimastigote: (and trypomastigote) Are replicative stages in the invertebrate and the Vector: Tsetse fly mammalian hosts, respectively Mechanism of the disease: Trypomastigote: main infective stage (cuz you go on a trip) Part of body affected: Blood, lymph, and central nervous system Metacyclic: infective stage outside the host body How it affects: Trypanosomes multiply in blood and lymph, eventually crossing the blood -brain barriers to cause neurological symptoms like confusion, sleep disturbances, and lethargy Complex developmental cycle, involves several morphological changes Diagnosis/Detection: Methods: Symptoms depend on the species of Trypanosome - in humans, a vascular and lymphatic ○ Microscopic identification of trypomastigotes in blood, lymph node aspirates, or infection is followed by an invasion of the central nervous system that gives rise to 'sleeping' cerebrospinal fluid (CSF) symptoms, followed by death Infective and Diagnostic life stages: Infective stage: Metacyclic trypomastigotes (introduced by tsetse fly) The number of people being affected by the disease has declined and may be eradicated in this Diagnostic stage: Trypomastigotes in blood, lymph, or CSF decade Diagnosed microscopically in blood and some other body fluids Mechanism of infection: Route: Feces of infected triatomine bugs ("kissing bugs") entering through mucosal surfaces or Chaga's disease: broken skin Life cycle stages: Vector organism: Triatomine bugs Epimastigote and Amastigote (not bearing flagella): Are the replicative stages in the Mechanism of the Disease: invertebrate and the mammalian hosts respectively Part of the body affected: Heart, GI tract, and other organs Trypomastigote: The main infective stage How it affects: Acute stage involves fever and swelling at the infection site. Chronic infection may Metacyclic: Infective stage outside the host body lead to cardiomyopathy, megaesophagus, or megacolon due to damage to nerves and muscle tissue 6-7 million people infected worldwide, mostly in Latin America. It can be life-threatening in its Diagnosis/Detection: chronic phase (through heart complications) Methods ○ Microscopy to detect trypomastigotes in blood during acute phase Diagnosed microscopically in blood ○ Serological tests or PCR for chronic phase detection Infective and Diagnostic life stages: Infective stage: Metacyclic trypomastigotes (from bug feces) Diagnostic stage: Trypomastigotes in blood (acute phase); amastigotes in tissue biopsies (choronic phase) Leishmania spp. Mechanism of infection: Life cycle: Route: Bite of an infected female sandfly (Phlebotomus or Lutzomyia species) They are dimorphic Vector organism: Sandfly Live and replicate in the gut of sandflies as flagellated forms (PROMASTIGOTE) Mechanism of disease: As non-flagellated forms (AMASTIGOTES) in mammalian cells. Part of body affected: Causes a variety of ailments collectively called leishmaniasis ○ Cutaneous Leishmaniasis: Skin and subcutaneous tissues, causing ulcers or nodules at the bite site Visceral infection that affects the spleen; almost always fatal without treatment (e.g. kala-azar) ○ Mucocutaneous Leishmaniasis: Mucous membranes of the nose, throat, and mouth, causing tissue destruction Cutaneous: skin boils (e.g. oriental sore) ○ Visceral Leishmaniasis (kala-azar): Internal organs, particularly the spleen, liver, and bone marrow, leading to systemic symptoms Mucocutaneous: ulcers or sores in your nose, mouth, or throat How it affects: The parasite invades macrophages, where it multiplies, causing tissue damage and immune response dysregulation Diagnosed by examination of affected tissue Diagnosis/Detection Methods: ○ Cutaneous/Mucocutaneous: Microscopy or culture or mucosal lesions. Molecular techniques (PCR) or serology may also be used ○ Visceral: Bone marrow, splenic aspirates, or lymph node biopsy for microscopy or culture; SAR: serological tests; PCR for confirmation Alveolata: Infective and Diagnostic life stages: The dinoflagellates, apicomplexans (plasmodium), and ciliates have an alveolar membrane Infective stage: Promastigotes (introduced into the host by the sandfly) Zoology Page 7  ○ Cutaneous/Mucocutaneous: Microscopy or culture or mucosal lesions. Molecular techniques (PCR) or serology may also be used ○ Visceral: Bone marrow, splenic aspirates, or lymph node biopsy for microscopy or culture; SAR: serological tests; PCR for confirmation Alveolata: Infective and Diagnostic life stages: The dinoflagellates, apicomplexans (plasmodium), and ciliates have an alveolar membrane Infective stage: Promastigotes (introduced into the host by the sandfly) system- flattened membrane-bound sacs just beneath the outer cell membrane that forms a Diagnostic stage: Amastigotes (intracellular form within macrophages, detectable in tissue pellicle to provide rigidity and cell shape. This feature links them in the clade Alveolata samples or aspirates). Apicomplexans: All apicomplexans are parasites of animals They have a unique system of organelles, the apical complex, in the anterior region of the cell specialized for penetration of host cells and tissues They spread through the host as sporozoites, and undergo complex sexual and asexual life cycles involving two or more host species. They include many important parasites of livestock and humans, including coccidiosis, toxoplasmosis, tick-borne fevers (piroplasm) and haemosporidians. Plasmodium spp. Are blood parasites and the causative agent of malaria. Cryptosporidiosis (Crypto) Mechanism of Infection: Drinking water and recreational water are the most common ways of infection Route: Fecal-oral transmission through ingestion of oocysts in contaminated water, food, or via Anyone can get sick with Crypto, but people with weakened immune systems are more contact with infected individuals or animals likely to have severe and potentially life-threatening symptoms. It is one of the leading Vector organism: None involved causes of parasitic deaths Mechanism of the disease: Symptoms: Part of body affected: GI tract, particularly the epithelial lining of the small intestine ○ Diarrhea How it affects: Sporozoites released from ingested oocysts invade the intestinal epithelial cells, ○ Stomach cramps/pain disrupting normal function and causing diarrhea, abdominal cramps, nausea, and dehydration. Im ○ Nausea immunocompromised individuals, the disease can be severe and chronic ○ Vomiting Diagnosis/Detection: ○ Fever Methods: They usually last about 1-2 weeks, but can come and go for up to 30 days ○ Microscopic examination of stool using modified acid-fast staining to detect oocysts Diagnosed from feces ○ Antigen detection assays (e.g., enzyme immunoassay) ○ Molecular methods such as PCR for species-specific identification Infective and Diagnostic life stages: Unikonta: Infective stage: thick-walled oocysts (ingested via contaminated sources) Amoebas: Diagnostic stage: Oocysts shed in the feces, detectable in stool samples They are not monophyletic Found in many distantly related eukaryotic taxa Pseudopodia can be finger-like (in Amoebozoa) or needle-like (in Rhizariana) Some have a rigid shell, or 'test' Amoebozoa: Lobe-shaped pseudopodia ('false-feet') - temporary extensions of the cytoplasm used in locomotion and feeding Ubiquitous occurrence, in any moist or aquatic habitat Many species are ectocommensals, some are endosymbiotic (several species are found naturally in the human gut, the first described was from human teeth) Entamoebas: Symbiotic in all vertebrate classes and some invertebrates: parasitic or commensal Humans are hosts to 6 species, but only one is notoriously pathogeniic: Entamoeba histolytica Entamoeba histolytica, the causative agent of amoebic dysentery Third most common cause of parasitic death in the world (after malaria and schistosomiasis) It is a highly evolved parasite of the human gut: ○ It has incorporated bacterial genes into its DNA that help it to feed on a wide range of different sugars and energy sources ○ Much of its genome is dedicated to producing surface coat proteins that change in response to the host immune response Mechanism of infection Amoebic dysentery (Entamoeba histolytica): Route: Fecal-oral transmission via ingestion of cysts in contaminated water, food, or through contact with contaminated surfaces Vector organism: none involved Mechanism of disease: Amoebic dysentery is spread by fecal contamination of food and water and is most Part of body affected: large intestine, liver (in extraintestinal cases) How it affects: common where sanitation is poor ○ Intestinal: trophozoites invade the colonic mucosa, causing ulcers and inflammation, leading to bloody diarrhea (dysentery), Amoeba invade the intestine but may spread to the liver, lungs, and other tissues abdominal pain, and cramping Infection is caused by the ingestion of cysts in contaminated food or water ○ Extraintestinal: Trophozoites can migrate via the bloodstream to the liver, forming abscesses and causing fever, right upper quadrant pain, and hepatomegaly Cysts develop into pathogenic trophozoite forms Diagnosis/Detection Life-cycle: Methods: ○ Mature cysts are ingested ○ Microscopic examination of stool samples to detect cysts or trophozoites (may require multiple samples) ○ Antigen detection assays or PCR for more sensitive detection ○ They then turn into trophozoites ○ Imaging (e.g., ultrasound, CT) for hepatic abscesses ○ Then it either multiplicities as cysts or trophozoite ○ Serological tests for extraintestinal infections Infective and Diagnostic life stages: ○ Which then become the diagnostic parasite form Infective stage: Cysts (ingested via contaminated sources) Diagnostic stage: ○ Intestinal: trophozoite and cysts in stool samples ○ Extraintestinal: Trophozoite in abscess aspirates or tissue samples Mechanism of infection: Naegleria fowleri (aka the brain-eating amoeba): Route: Inhalation of water contaminated with N. fowleri through the nose (e.g., during swimming or diving in warm fresh water) Vector organism: None involved. The amoeba is free-living in the environment Free living amoeba common in warm fresh water Mechanism of disease: Part of body affected: CNS, primarily the brain and spinal cord Infects humans by entering nose during water-related activities How it affect Travels to the brain causing Primary Amoebic Meningoencephalitis (PAM) ○ Amoebas enter the nasal passages, migrate through the olfactory nerves, and invade the brain via the cribriform plate Very rare, but usually fatal ○ Causes severe inflammation and necrosis of brain tissue, leading to symptoms like headache, fever, nausea, seizures, confusion, and rapid progression to coma and death Diagnosed from cerebrospinal fluid (spinal tap) or tissue using PCR or microscopy Diagnosis/Detection: Life cycle: Methods: ○ Cyst ○ Microscopic examination of cerebrospinal fluid (CSF) to detect trophozoites ○ Culture of CSF or tissue samples ○ Trophozoite (infective stage) ○ Molecular methods, such as PCR, for species confirmation ○ Flagellated form (diagnostic stage) ○ Imaging (MRI or CT) may show brain inflammation but is not specific to N. fowleri Infective and Diagnostic Life stages: Infective stage: Trophozoites (the actively feeding and invading form) Diagnostic stage: Trophozoite in CSF or brain tissue; flagellated forms may also be observed in environmental samples under c ertain Zoology Page 8  Diagnostic stage: Trophozoite in CSF or brain tissue; flagellated forms may also be observed in environmental samples under c ertain conditions Note: N. fowleri is a rare but highly fetal disease, with a very rapid course of progression. Early diagnosis and treatment are critical but challenging. Recap questions: 1) What sets eukaryotes apart from prokaryotes? a. They have membrane bound organelles and a nucleus surrounded by a nuclear envelope 2) What are protists? Are they a monophyletic group? Explain a. Protists are a diverse group of mostly unicellular eukaryotic organisms that are not plant, animals, or fungi. They include protozoa, algae, and slime molds b. No, protists are not a monophyletic group. They are paraphyletic, meaning they do not include all descendants of a common ancestor. For example, some protists are more closely related to plants, animals, or fungi than to other protists. 3) What are protozoans? What sets them apart from other protists? How are they different form metazoans? a. Protozoans are single-celled, animal-like protists that are heterotrophic and often motile b. Protozoans are heterotrophic, unlike photosynthetic algae. They are animal-like and often motile, while other protists may not move or feed similarly c. Protozoans are unicellular, while metazoans (animals) are multicellular. They also handle all life functions withing one cell, unlike the specialized tissues of metazoans 4) Name the four eukaryote 'supergroups' a. Excavata b. SAR c. Unikonta d. Archaeplastida 5) Can you name representative members of the protist clade: a. Excavata i. Trypanosoma brucei (causes sleeping sickness) ii. Giardia lamblia (causes giardiasis) iii. Trichomonas vaginalis b. Alveolata i. Plasmodium falciparum (causes malaria) ii. Cryptosporidium iii. Dinoflagellates c. Amoebozoa i. Entamoeba histolytica ii. Naegleria fowleri Zoology Page 9 Bats Monday, November 25, 2024 9:11 AM Bats Audio recording started: 9:11 AM Monday, November 25, 2024 Bats have evolved ways to slow down the effects of aging They are resistant to infectious diseases To study the bats: 1) Uncover its genome (need exquisite genomes) Zoology Page 10 Metazoa Saturday, November 30, 2024 1:23 PM They are part of the Unikonta supergroup (Animals) Animals are multicellular, heterotrophic eukaryotes with tissues that develop from embryonic layers Tissues are collections of specialized cells separated by layers of membranes Key features of animal Bauplan: 1) Body symmetry 2) The number of tissues 3) Body cavities in triploblastic animals (no longer used for classification) 4) Protostome vs deuterostome development Classification: 1- Body plans (symmetry and body axes): a. It is important as it gives information about orientation in the environment and specialization of the body regions b. Types of plans: i. Radial symmetry ii. Asymmetrical (sponges (Porifera)) iii. Bilateral symmetry 2- The number of tissues: a. Tissues are collections of specialized cells separated by layers of membranes. b. The concentric layers (called germ layers) form through gastrulation of the embryo c. Types of tissues: i. Ectoderm - outer layer, forms outer surface and sometimes CNS ii. Endoderm - innermost layer becomes lining of the digestive tube and organs derived from it, such as liver and lungs in vertebrates iii. Mesoderm - a third germ layer that forms the muscles and most other organs between the digestive tract and outer surface d. Diploblastic organisms only have the ectoderm and endoderm. Whereas the triploblastic have all germ layers e. However, sponges (Porifera), have one germ layer and lack true tissues f. It is important as it shows the complexity of body structure (tissues, organs) 3- Body cavities in triploblastic animals: a. !! No longer considered a classification characteristics b. Fluid or air-filled: i. A body cavity or 'coelom' separated the digestive tract from the outer wall. It is derived from mesoderm ii. Some animals have a cavity formed from the blastocoel, called the hemocoel ('pseudocoelom') iii. Others lack a cavity altogether and are known as acoelomates c. It is important as it shows the improved internal transport of fluids and gasses, cushioning organs, hydrostatic skeleton. 4- Protostome or deuterostome development in triploblastic animals a. Protostome: i. Cleavage: 8-cell stage, spiral and determinate ii. Coelom formation: Solid masses of mesoderm split and form coelom iii. Fate of blastopore: Mouth develops from blastopore b. Deuterostome: i. Cleavage: 8-cell stage, radial an indeterminate (=identical twins and stem cells) ii. Coelom formation: Folds of archenteron form coelom iii. Fate of blastopore: Anus develops from blastopore Zoology Page 11  iii. Fate of blastopore: Anus develops from blastopore c. It is important as indetermined cleavage allows developmental flexibility and repair Recap: 1- Name three main characteristics of animal body plan (‘bauplan’). Which of them are used for taxonomic classification? a. Symmetry b. Body Cavity c. Protostomes vs deuterostomes (embryonic development) 2- What functions does coelom play? Do humans have one a. Provides space for organ development, acts as shock absorber, and facilitates movements b. Yes, humans are coelomates 3- Are humans diploblastic or triploblastic? What does it mean? a. They are triploblastic, meaning that they have 3 germ layers: ectoderm, endoderm, mesoderm) 4- What advantages are conferred by bilaterally symmetrical body plan? What other body plans are there in the animal world a. Allows for better movement, sensory input, and coordination b. Radial symmetry (starfish) and asymmetry (sponges) 5- Which animal phyla are of particular interest for medicine a. Nematoda b. Arthropoda c. Platyhelminthes 6- What’s special about deuterostome development? How is it different from protostome a. Deuterostomes: The anus forms first, then the mouth (humans) b. Protostomes: The mouth forms first, then the anus (arthropods) Zoology Page 12 Worms: flatworms and roundworms Saturday, November 30, 2024 2:22 PM what is a worm? ○ Soft-bodied, legless animal whose length exceeds it width ○ At least 16 phyla that could be called worm-like ○ Platyhelminthes and Nematoda include many human parasites Helminths ○ Any of the parasitic worms of the groups: ▪ Tapeworms (cestodes; phylum Platyhelminthes) ▪ Flukes (trematodes; phylum Platyhelminthes) ▪ Roundworms (phylum Nematoda) Platyhelminthes - flatworms: ○ Free-living (freshwater, marine, terrestrial) or parasitic (flukes and tapeworms) ○ Triploblastic, bilaterally symmetrical, protostome, acoelomates (no fluid-filled cavity) ○ Unsegmented ○ Cephalised, with centralized nervous system (CNS) (has a head where most of its nervous system and senses (like eyes) are concentrated) ○ No circulatory or respiratory system - gas exchange through body surface (hence flat body form) ○ Incomplete gut (single opening), but highly branched to distribute nutrition to cells; absent in cestodes (tapeworms)! ○ Most Platyhelminths are hermaphrodites - each has both male and female reproductive organs, elaborate reproductive system allows for internal fertilization The parasitic way of life - flukes and tapeworms ○ Parasitic flukes and tapeworms have characteristic modifications (variably among groups): ▪ Reduced cephalization (in tapeworms producing a 'head' bearing hooks and suckers to attach to the host) ▪ Extensive development of the reproductive system with reduction of other systems (gut lost in tapeworms) ▪ Lack of a well-developed nervous and gastrovascular system (they live in a stable environment and the host has already digested their food) ▪ Development of a tegument that protects them from host digestive fluids ○ Both flukes and tapeworms use secondary or (intermediate) hosts to transport the species to the primary (final) host. The primary host is infected with the sexually mature adult while the secondary host contains the larval stage(s) ○ This leads to complicated life cycles Parasitic Platyhelminthes: ○ Trematoda (flukes): ▪ Most are endoparasitic (they are primarily internal parasites, living inside the host's body) ▪ Most have 2 or 3 hosts in life cycle, including a mollusc (snail) (they typically require multiple hosts during their life cycles. The first is usually a mollusc (like a snail), followed by one or more vertebrates or other animals) ▪ With one or more suckers, but lacking prohaptor or opisthaptor (they typically have suckers for attachment to their host, but unlike other parasitic flatworms, they do not need prohaptor (front attachment organ) or opisthaptor (rear attachment organ) ○ Cestoda (tapeworms) ▪ Exclusively endoparasitic ▪ Digestive tract absent ▪ Most have anterior scolex (attachment organ), neck and strobila composed of proglottids (segments containing the reproductive organs) Life Cycle of a Trematode (Fluke) Parasite: ○ Eggs are released into the environment: The parasite starts its life as an egg. The egg can either be eaten by another animal (called the intermediate host) or hatch into something called a miracidium. ○ Miracidium swims and enters the intermediate host: The miracidium actively swims around until it finds and enters the intermediate host (like a snail). Inside the intermediate host, the parasite starts to grow and multiply. ○ A lot of baby parasites are made: Inside the intermediate host, the parasite goes through several stages where it makes more and more babies. These stages are called sporocyst and redia. ○ Cercaria leaves the intermediate host: The parasite finally produces a new form called cercaria, which looks like a little swimmer with a tail. The cercaria leaves the intermediate host and swims around in the water. ○ Cercaria finds a second host or the final host: The cercaria either: ▪ Encysts (wraps itself up) in a second animal (called the second intermediate host) and waits to be eaten by the final host, or ▪ Penetrates directly into the final host (like a human) if there's no second host. ○ Cercaria turns into an adult: Once the cercaria gets into the final host, it "hatches" out of its protective covering (called excysting) and grows into the adult parasite, ready to make eggs and start the cycle over again Trematoda: Fasciola hepatica (the liver fluke) ○ Fascioliasis (fasciolosis) occurs worldwide ○ Human infections with F. hepatica are found in areas where sheep and cattle are raised, and where humans consume raw watercress ( ), including Europe, the Middle East, and Asia ○ Infections with F. gigantica have been reported, more rarely, in Asia, Africa, and Hawaii Fascioliasis: Life cycle: Zoology Page 13  ○ Life cycle: ▪ Eggs passed in feces, develop in contact with water, miracidia hatch and infect aquatic snails ▪ Cercariae are released from snail and encyst in water plants (e.g., watercress), to be ingested by primary host ▪ Metacercariae excyst in the duodenum and migrate through intestinal wall, peritoneal cavity and the liver into the bile ducts, where they develop into adults (3-4 months) and produce eggs ○ Symptoms include nausea, vomiting, and abdominal pain/tenderness. Fever, rash, and difficulty breathing may occur. Later also inflammation of the gallbladder and pancreas ○ Fascioliasis is treatable and preventable ○ Diagnosis by microscopic examination of eggs in feces Trematoda: Schistosoma spp. (blood flukes) ○ Intermediate hosts are freshwater snails ○ Cercariae emerge from the snail into the water ○ Human infection can occur through skin contact in contaminated water ○ Most human infections are caused by schistosoma mansoni, S. haematobium, or S. japonicum ○ Rather uniquely among Platyhelminthes, adult schistosoma spp. Are dioecious: separate male and female individuals Schistosomiasis or bilharzia Mechanism of infection ○ Within days of infection, rash or itchy skin may occur. Fever, chills, cough , and muscle aches can begin Route: skin penetration by free swimming schistosoma cercariae in contaminated within 1-2 months of infection. Most people have no symptoms at this phase though freshwater ○ Egg laying induces more severe symptoms - mainly by the body's reaction to the worms' eggs, rather Vector organism: freshwater snails act as the intermediate host, releasing cercariae than by the parasite itself Mechanism of the disease: ○ Egg travels to the intestine, liver or bladder, causing inflammation or scarring. Prolonged infection may Parts affected: damage the liver, intestine, lungs, and bladder. Adult worms live in blood vessels of the intestines or bladder. ○ Rarely, eggs are found in the brain or spinal cord and can cause seizures, paralysis, or spinal cord Eggs can cause inflammation and tissue damage in the liver, intestines, bladder, and inflammation other organs ○ Second only to malaria as the most devastating tropical parasitic disease How it affects: ○ Mostly affect poor and rural communities, particularly agricultural and fishing populations. The immune system reacts to eggs lodged in tissues, leading to fibrosis, organ damage, and chronic inflammation Diagnostic/Detection: Detects eggs in stool or urine using microscopy Blood tests for antibodies or antigens Cestoda: Imaging (e.g., ultrasound) to assess organ damage Cestodes live in the guts of vertebrates Infective and Diagnostic life stages: Highly modified as an adaptation to their parasitic way of life - three distinct body region: Infective stage: cercariae (penetrate human skin) ○ Scolex: the attachment organ Diagnostic stage: eggs in stool or urine ○ neck ○ Strobila: an elongated segmented trunk or consisting of individual proglottids. Very different to the segmentation of earthworms and insects. Each proglottid contains an independent reproductive tract and 'flame cells' (protonephridia) for excretion Taeniasis: the beef tapeworm Taenia Saginata and the pork tapeworm T. solium Oncosphere - develops in the intermediate host after ingestion of eggs Cysticerci - encysts in the tissue of the intermediate host, where they can survive for several years Mechanism of infection: Cysticercosis: The pork tapeworm Taenia Solium Roue: Fecal-oral transmission of Taenia Solium eggs from contaminated food, water, or poor hygiene It results from Taenia Solium infection with eggs through fecal-oral route (as opposed to by ingesting Eggs hatch in the digestive tract, and larvae (oncospheres) penetrate the intestinal wall and migrate through the Cysticerci encysted in pork in Taeniasis ) bloodstream to various tissues Mechanism of Disease: Cysticerci develop in human tissue (as opposed to pigs) in any organ, including eyes and brain. Parts affected: A common cause of seizures worldwide Muscles: from cysts, often asymptomatic Brain (neurocysticercosis): causes seizures, headaches, and neurological symptoms Eyes: can impair vision How it affects: Cysts cause inflammation and pressure on surrounding tissues, especially in the CNS, leading to severe complications Diagnosis/Detection: Imaging (CT or MRI) to detect cysts in the brain or other tissues Serological tests to detect antibodies against T. Solium Biopsy (rare) to confirm cysts in accessible tissues Infective and Diagnostic life stages: Infective stage: eggs of T. Solium Diagnostic stage: Cysts (Cysticerci) in tissues Parasites can modify host behaviour ○ Some parasites evolved to modify host behaviour in a way that increases the chance of transmission Nematoda: Characteristic features: ○ Triploblastic, bilateral, blastocoelic (pseudocoelomate), some species are acoelomates Vermiform ("worm-like" appearance), unsegmented, round in cross-section Zoology Page 14  ○ Vermiform ("worm-like" appearance), unsegmented, round in cross-section ○ Covered by a layered cuticle, growth by ecdysis (shedding an outer layer) ○ Inly longitudinal muscles (no circular muscles) - contraction produces a thrashing motion ○ Gut complete, but reduced in parasitic species ○ Both free-living (marine, freshwater, terrestrial) and endoparasitic in animals and plants ○ One of the biggest groups of organisms Classification: ○ High degree of morphological uniformity makes classification very tricky - identification is difficult ○ Parasitism has evolved several times independently (unlike in Platyhelminthes) ○ Used to be divided into two classes based on morphology: ▪ Adenophorea (aphasmida) ▪ Secernentea (Phasmida) ○ Now it is classified into three classes based on molecular evidence: ▪ Chromadorea (including many human parasites) ▪ Enoplia ▪ Dorylaimia Humans host at least 50 nematode species Key pathogens are: ○ Ascaris lumbricoides ▪ The largest nematode parasitizing the human intestine ○ Trichinella Spiralis ○ Enterobius Vermincularis (the human pinworm) ▪ Very common with a worldwide distribution ○ Wuchereia bancrofti, Brugia malayi, B. timori (the causes of lymphatic filariasis) ○ Onchocerca volvulus (the cause of river blindness) Ascaris Lumbricoides (Ascariasis): Mechanism of infection: Route: fecal-oral transmission. Ingesting eggs from contaminated food, water, or soil. ○ Infection occurs when a human swallows water or food contaminated with embryonated eggs Vector organism: None. The parasite is transmitted directly through the environment ○ The larvae hatch in the intestine and burrow through ( to the circulatory system and are Mechanism of disease: Parts affected: carried to the lungs ○ Intestines: adult worms live in the small intestine, causing malnutrition, intestinal blockage, or ○ They reside in the lungs for two week then penetrate through to the bronchial passage and ascend to abdominal pain ○ Lungs: larvae migrate to the lungs during development, causing respiratory symptoms like coughing the throat where they are swallowed and develop to adults in the small intestine and wheezing ○ Adults live in lumen of small intestine. Eggs are passed with feces and are infective after several weeks How it affects: ○ Larvae migrate through the bloodstream, lungs, and throat before returning to the intestines. This ○ Minor parasite burden may be asymptomatic, heavier burdens lead to variety of inflammatory systems migration can cause tissue damage and inflammation Diagnosis/Detection: and malnutrition Stool examination for eggs under a microscope Imaging (x-ray or ultrasound) for large worm burdens Blood tests showing increased eosinophils (a type of WBC) Infective and Diagnostic life stages: Infective stage: fertilized eggs in contaminated food, water, or soil Diagnostic stage: Eggs in stool Trichinella spiralis (trichina worm; Trichinellosis/trichinosis) ○ Humans acquire Trichinella spiralis by eating undercooked infected pork or other meat with larvae Mechanism of disease: encysted in the muscle tissue Route: ingesting undercooked or raw meat (especially pork or wild game) Vector organism: none, transmission occurs directly through infected meat ○ In the intestine, they mature and reproduce and the females embed themselves in the gut wall, Mechanism of disease: releasing more larvae Parts affected: ○ Muscles: the larvae encyst in muscle tissue, causing pain, swelling, and muscle weakness ○ These burrow through the body or travel in the lymphatic system to other organs and muscle where ○ Intestines: adult worms live in the small intestine, where they mate and produce larvae the encyst How it affects: ○ Larvae enter the bloodstream from the intestines and migrate to muscles, where they form cyst. This ○ Humans are a dead end for this parasite (unless eaten) leads to muscle inflammation and can cause severe symptoms like fever, muscle pain, and swelling ▪ Humans are not part of the normal life cycle of the parasite. It is only transmitted between Diagnosis/Detection: Muscle biopsy to detect cysts animals. Humans become infected when they ingest undercooked mean, but they cannot Blood tests (serology) to detect antibodies against Trichinella Imaging techniques may sometimes be used for muscle involvement transmit the parasite to other hosts. Infective and diagnostic life stages: ○ Diagnosed by detection of antibodies to excretory/secretory Trichinella antigen Infective stage: encysted larvae in undercooked or raw meat Diagnostic stage: encysted larvae in muscle tissue ○ The encysted larvae trigger inflammatory response (swelling and fever). The disease can be very serious if larvae migrate to the heart or brain Enterobius vermicularis (the human pinworm; Enterobiasis) Mechanism of infection: ○ Humans are considered to be the only hosts of E. vermicularis Route: fecal-oral transmission. Infection occurs when microscopic eggs are ingested, typically via contaminated hands, food, or surfaces 1. Females deposit eggs on perianal area Vector organism: none; humans are the only host 2. Infection occurs via self-inoculation after scratching the perianal area, or through exposure to eggs in Mechanism of the disease: Parts affected: the environment ○ Adult worms inhabit the lower intestine and rectum 3. Following ingestion, the larvae hatch in the small intestine ○ Female worms migrate to the perianal area at night to lay eggs, causing itching How it affects: 4. And the adults establish themselves in the colon ○ The primary symptom is intense itching around the anus, which can lead to sleep disturbances. 5. Gravid females migrate nocturnally outside the anus and oviposit Scratching can result in secondary bacterial infections Diagnosis/Detection: ○ The larvae inside the eggs develop and become infective in 4 to 6 hours under optimal conditions The "tape-test": a piece of adhesive tape is pressed to the perianal area in the morning and examined under a ○ The perianal activity of the gravid female worms causes itching, leading to reinfection microscope for eggs Direct observation of worms in the perianal region or stool ○ Diagnosis by microscopic identification of eggs collected in the perianal area Infective and Diagnostic life stages: Infective stage: eggs ingested from contaminated surfaces or hands ○ Worldwide distribution, all socio-economic backgrounds. Particularly prevalent in children Diagnostic stage: eggs or adult worms found in the perianal area or on tape samples Filarial worms: Nematode parasites that require an intermediate arthropod host, typically a blood sucking insect The characteristic microfilariae stage of the worm life cycle is transmitted to the insect with a bloodmeal, where it develops into a larvae Lymphatic filariasis (elephantiasis): ○ Caused mainly by Wuchereria bancrofti (90%), also by Brugia malayi and B. timori ○ Transmitted by mosquitoes (Ades, Anopheles, Culex, Mansonia) Onchocerciasis (river blindness): ○ Caused by Onchocerca Volvulus Transmitted by blackflies (Simulium) Zoology Page 15  ○ Transmitted by blackflies (Simulium) Lymphatic filariasis (Elephantiasis): ○ Also called bancroftian or brugian filariasis - depending on the nematode species responsible. ○ Wuchereria bancrofti (sub-Saharan Africa) and Brugia malayi (Far East) ○ Typical mosquito vectors vary by region ▪ Anopheles (Africa) ▪ Culex quinquefasciatus (the Americas) ▪ Aedes and Mansonia (the Pacific and Asia) ○ Wuchereria bancrofti (bancroftian filariasis): Mechanism of infection: i. During a blood meal, larvae are introduced onto human skin, and penetrate into the bite wound Route: transmitted via the bite of infected mosquitos (vector species include: Culex, Aedes, and Anopheles) Vector organism: Mosquitos, which carry infective larval stages (L3 Larvae) ii. They develop in adults that commonly reside in the lymphatics Mechanism of disease: iii. Adults produce microfilariae that usually have nocturnal periodicity. The microfilariae migrate Parts affected: ○ Adult worms in the lymphatic system, causing blockages and inflammation actively through lymph and blood channels ○ Chronic infections can lead to lymphatic dysfunction, swelling, and enlargement of limbs or genitals (elephantiasis) iv. A mosquito ingests the microfilariae during a blood meal How it affects: ○ The worms disrupt the normal flow of lymph, leading to fluid accumulation (lymphedema) and thickening of the skin v. Inside the mosquito, the microfilariae undergo 3 stages of larval development (L1-L3). and underlaying tissues ○ Acute symptoms include fever, lymphadenitis, and lymphangitis vi. The L3 larvae migrate to the mosquito's proboscis, and can infect a human when the fly takes a Diagnosis/Detection: blood meal (goes back to the first point) Microscopy to detect microfilariae in blood smear (best collected at night when microfilariae circulate) Antigen detection tests (ELISA) for Wuchereria bancrofti ▪ Highly disfiguring and disabling disease. Ultrasound to visualize adult worms in the lymphatic system ▪ The most prominent clinical feature is severe lymphedema of the limbs ("elephantiasis") and Infective and Diagnostic life stages: Infective stage: L3 larvae injected into humans by mosquito bites occasionally genitalia due to dysfunction of lymphatic vessels Diagnostic stage: Microfilariae in the blood ▪ Affected limbs become grossly swollen; the skin may become thick and pitted, and secondary infection are frequent due to lymphatic dysfunction Onchocerciasis: ○ It is not a killer disease, but it is extremely debilitating. ○ Juveniles of the filarial pathogen, Onchocerca volvulus, invade the eye and die, causing blindness ○ The name 'river blindness' refers to the impact of the disease on people living alongside rivers in West Africa and South America where insect vector Simulium spp. (blackflies, Diptera: Simulidae) live in flowing waters ○ Onchocerca volvulus (Onchocerciasis / river blindness) Mechanism of infection: i. During a blood meal, larvae are introduced onto human skin, and penetrate into the bite wound Route: transmitted through the bite of infected blackflies (Simulium spp.) ii. In subcutaneous tissues, the larvae develop into adults, where they can live for 15 years Vector organism: Blackflies, which carry infective L3 larvae Mechanism of disease: iii. Adults produce microfilariae that can last for up to 2 years Parts affected iv. Microfilariae are typically found in the skin and in the lymphatics of connective tissues, but ○ Skin: Microfilariae migrate through the skin, causing intense itching, dermatitis, and nodules ○ Eyes: Microfilariae that die in the eyes cause inflammation, scarring, and eventually blindness occasionally in peripheral blood, urine, and sputum How it affects: v. Microfilariae are ingested by a blackfly during a blood meal ○ Chronic inflammation due to dying microfilariae leads to skin damage, disfigurement, and vision loss ○ Subcutaneous nodules from around adult worms vi. Inside the blackfly they undergo 3 stages of larval development (L1-L3). Diagnosis/Detection: vii. The L3 larvae migrate to the blackfly's proboscis and can infect a human when the fly takes a Skin snip biopsy to detect microfilariae Serological tests for antibodies blood meal (1) Examination of nodules for adult worms ▪ Symptoms include severe itching, bumps under the skin, and blindness; the second-most Slit-lamp examination for microfilariae in the eyes Infective and Diagnostic life stages: common cause of blindness due to infection, after trachoma (bacterial infection) Infective stage: L3 larvae transmitted to humans by blackfly bites Diagnostic stage: microfilariae in the skin or eyes; adult worms in subcutaneous nodules ○ The role of endosymbiotic Wolbachia bacteria in the pathogenesis of river blindness ▪ Bacterium-free worm extract doesn’t cause severe disease in mice, Wolbachia-laden worms do ▪ There is a molecular receptor in the eye that is particularly sensitive to Wolbachia. This receptor is crucial to eliciting an inflammatory immune response ▪ Antibiotic elimination of the endosymbiotic Wolbachia bacteria weakens the Onchocerca worm - doxycycline has been shown to significantly lower microfilarial loads in the host, and may kill the adult worms, due to the symbiotic relationship between Wolbachia and the worm 'live worm found in Australian woman's rain in world first' ○ Nematode worm: Ophidascaris robertsi (Acsarididae) - common in carpet pythons ○ The patient had for months suffered stomach pain, a cough and night sweats, which evolved into forgetfulness and depression ○ Thought to be an "accidental host", likely after foraging wild plants contaminated by python feces and parasite eggs ○ Human encroachment on wildlife habitats brings a risk of novel zoonotic disease A success story: Drancunculus medinensis - Guinea worm (dracunculiasis) ○ The worm's larvae are carried by copepods (tiny aquatic crustaceans) found in lakes, ponds, and opoen wells. Humans become infected by ingesting infected copepods while drinking unfiltered water ○ Larvae mature in human abdominal cavity migrate to subcutaneous tissue, generally on the lower extremities, where they burst the skin to release larvae on contact with water ○ There is no drug treatment or vaccine. The adult worm has to be mechanically removed by winding up over several days - slow enough to prevent breaking the worm ○ Infection can be prevented by filtering water before drinking to prevent ingestion of the infected copepods - stop the disease transmission vector The number of cases has been reduced significantly! Zoology Page 16  ○ The number of cases has been reduced significantly! ○ Life Cycle in Humans: ▪ After being ingested, the larvae mature in the abdominal cavity. ▪ Adult worms then migrate to the skin, usually in the lower legs or feet. ▪ To reproduce, the female worm bursts through the skin when exposed to water, releasing larvae into the water to continue the cycle. 2015 Nobel Laureates in medicine for discovering Avermectins (including ivermectin) ○ William Campbell: Irish biologist and parasitologist ○ Satoshi Omura ○ Avermectins/Ivermectin ▪ Derived from Streptomyces avermitilis, a bacterium species discovered during this research ▪ Example of why preserving biodiversity is important: new species can provide critical medical discoveries ○ Mode of action ▪ Interferes with the nerve and muscle functions of helminths (parasitic worms) and insects ○ Diseases treated: ▪ Effective against: □ River blindness □ Lymphatic filariasis (elephantiasis) ▪ Also works on ectoparasitic arthropods (like mites and lice) Zoology Page 17 Arthropods Monday, December 2, 2024 2:12 PM The most species-rich animal phylum ○ Extremely diverse: 82% of all known species ▪ All environments (sea, freshwater, land, air) ▪ Every ecological niche ○ Very abundant Classified next to nematodes, under Ecdysozoa (exoskeleton shed periodically to allow growth (ecdysis) Phylum: Arthropoda ○ Invertebrates with jointed/articulated legs ○ Triploblastic, bilaterally symmetrical, coelomate, protostome ▪ Exoskeleton shed periodically to allow growth (ecdysis; unites all Ecdysozoa) ▪ Body divided into discrete segments, groups of segments specialized as tagmata (head, thorax, etc.) ▪ Hard, rigid exoskeleton: constructed from chitin, reinforced with CaCO3 in Crustacea Arthropod nuisance and phobia ○ High densities of particular species, e.g. ants, silverfish ○ Filth-frequenting insects, e.g. cockroaches, bluebottles, blowflies, etc. ○ Biters and stingers, e.g. ants, bees, wasps ○ Phobia: an anxiety disorder, irrational fear or aversion ▪ Entomophobia: to insects ▪ Arachnophobia: to spiders Stinging insects - venoms: ○ Insects of the taxonomic order Hymenoptera include bees, wasps, and ants. They can inflict a sting, usually in defense of the nest, sometimes for predation ○ Social insects co-operate to sting an intruder en masse - escalates the impact of an individual attack and deters even large vertebrates ○ the sting is a modified ovipositor(special organ that some female insects and other animals use to lay eggs) (worker bees and wasps are sterile females) ○ The honey-bee sting has backwardly directed barbs and cannot be retracted - it is single use only, and the bee dies when the sting and venom sac are ripped out Zoology Page 18  only, and the bee dies when the sting and venom sac are ripped out ○ Wasp and ant stings are unbarbed, can be retracted and are capable of repeated use ○ Hymenoptera venom constituents that contribute to the toxic effect include low molecular weight substances ▪ Such as biogenic amines, phospholipids, amino acids, and carbohydrates, and peptides such as melittin, ,apamin, or kinins ○ Formicine ants have lost the stinger and spray formic acid into a wound caused by the mandibles ○ Normal local reaction to a Hymenoptera sting consists of a painful, sometimes itchy, local wheal and flare reaction, followed by a swelling of up to 5-10 cm in diameter. Symptoms usually resolve withing a few hours ○ Systemic toxic reaction may occur after multiple stings; 200-1000 stings may be lethal in adults, 50 may be lethal in children Stinging insects - allergens ○ Hymenopteran allergens (mostly glycoproteins) are one of the most important causes of allergic and anaphylactic reaction ○ Usually in reaction to bee or wasp venoms, rarely ants ○ Allergic disease ○ Exposure to arthropod allergen (usually a low molecular weight protein) can trigger excessive immunological reactions ○ Common in people with occupational exposure to insects, particularly mealworms (Tenebrio larvae), bloodworms (Chironomid larvae), locusts and blowflies ○ Venomous and urticating insects cause the greatest danger when sensitized (previously exposed and allergy-sensitive) individuals are affected again, with the possibility of anaphylactic shock and death ○ The most significant arthropod-mediated allergy arises from the fecal material of house-dust mites (Dermatophagoides pteronyssinus) ○ Bed bugs (Cimex lectularius) can cause an allergic reaction or a severe skin reaction Insects inducing blisters and Urtica (itch) ○ Cause injury to humans as a defense mechanism, even though toxins aren's inoculated through a sting ○ Meloidae beetles - cantharidin ▪ Cause blistering of the skin - 'blister beetles') ○ Staphylinid beetles of the genus Paederus - pederine ▪ Causes severe blistering and long-term ulceration; produced by endosymbiotic bacteria ○ Lepidopteran caterpillars are a frequent cause of skin irritation or urtication ▪ Hollow spined or setae containing toxins which are released on contact or by breaking Zoology Page 19  ▪ Hollow spined or setae containing toxins which are released on contact or by breaking the hairs Invasive species: oak processionary moth (Thaumetopoea processionea) ○ Hair present on the larger larvae contain an urticating defensive toxin, thaumetopoein. ○ Larvae can cause skin and eye irritations, rashes, sore throats, and breathing difficulties. Flightless blood-suckers ○ Cimex lectularius and C. hemipterus - bed bugs ▪ Belong to the insect order Hemiptera, 1-7 mm in size ▪ Spend much of their time in dark, hidden location like mattress seams, or cracks in a wall. Not linked to hygiene, but rather high population density ▪ Come out to feed at night. Cause lesions and itch, secondary infection may result from scratching ▪ Can go without feeding for 100s of days, so difficult to get rid of ○ Fleas ▪ Belong to the insect order Siphonaptera, larvae -> larvae form pupae -> Adults hatch from Pupae ○ Human lice - 'vagabond's disease' (pediculosis) ▪ Infestation of the hairy parts of the body or clothing with eggs, larvae or adults of lice. The crawling stages of this insect feed on human blood, which can result in severe itching ▪ Belong to the insect order Psocodea, 1st nymph -> 2nd nymph -> 3rd nymph -> Adult ○ Scabies/itch mite (Sarcoptes scabiei) ▪ Belong to the arachnid family Sarcoptiformes, Morula -> Blastula -> Gastrula -> 'Neurula' -> Pharyngula Cleavage: ○ The process of synchronous cell division in a fertilized zygote, where the embryo undergoes a series of mitotic divisions without growth in size. This results in the formation of smaller cells called blastomeres ○ The process of cell division that occurs immediately after fertilization. The zygote (fertilized egg) undergoes rapid divisions to form smaller cells called blastomeres without an increase in the overall size of the embryo. This stage is critical for establishing the early structure of the developing organism ○ Up to 16-cell stage (at least in humans) ○ Radial cleavage (in Deuterostomes): ▪ The daughter cells are aligned with the parent cells, forming a radial pattern. This means the cell divide symmetrically, and the resulting layers are organized concentrically around the embryo's axis ▪ After this stage cell division is stochastic, and size increases. ▪ This is the morula stage Blastulation: (4 days post-conception) ○ The stage where the morula forms a hollow structure known as the blastula cavity ○ The morula hollows out throw further cell division, leaving a fluid-filled space. This is the blastocoel. The cells around the outside are the blastoderm ○ The embryo is now referred to as a 'blastula' ○ Several important event occur in this stage, including germ layer specification (at least at a very high level) and basic axis polarity formation ○ The outer layer of cells surrounding the blastocoel is called the blastoderm ○ In many vertebrates (like frogs), there is an important differentiation of the blastoderm into an animal pole (the side with more active division, typically forming the embryo) and a vegetal pole (the side with more yolk, often involved in forming structures like the gut). However, these terms are somewhat outdated, and many people now use 'embryonic' and 'abembryonic'. ○ In mammals (e.g., humans), the blastoderm forms a blastocyst rather than a typical blastula. The blastocyst consists of the trophoblast (which will contribute to placental tissue) and the inner cell mass (which will form the embryo). [we do not have yolk masses. Rather the outer blastoderm differentiates into a trophoblast and an 'inner cell mass' or embryoblast. In mammals this is often called a 'blastocyst'. The trophoblast will go on to form much of the tissue in the placenta] ○ Placenta Accreta: ▪ A disturbingly common condition (almost 1 in 300) ▪ This condition arises when the trophoblast implants too deeply into the uterine wall. Normally, the placenta attaches to the uterine lining but doesn't invade the muscle layer. In placenta accreta, however, the placental tissue adheres to the uterine muscle and may penetrate it, making it difficult for the placenta to detach after childbirth. This can lead to serious complications during delivery Zoology Page 46  penetrate it, making it difficult for the placenta to detach after childbirth. This can lead to serious complications during delivery ▪ This is often associated with heavy hemorrhaging during delivery and need for caesarean intervention. In extreme cases (with penetration into the muscle wall of the uterus), a hysterectomy can be required to control potentially fatal bleeding Gastrulation ○ It is the phase where the blastula (a hollow sphere of cells) recognizes into a gastrula, which has three germ layers: ectoderm, mesoderm, and endoderm. These layers will later differentiate into all the organs and tissues of the body ○ Protostomes: mouth forms from blastopore ○ Deuterostomes: Anus forms from blastopore ○ Formation of the three germ layers: ▪ Ectoderm (outer layer): forms the skin, nervous system, and other structures such as the neural crest ▪ Mesoderm (middle layer): forms muscles, skeleton, circulatory system, kidneys, and other organs ▪ Endoderm (inner layer): forms the gut, lungs, liver, and other internal organs ○ Cellular movements: gastrulation involves several critical cellular movements that help shape the embryo: ▪ Invagination: the folding of the cell layer inward, creating a pocket-like structure. This is typical in protostomes ▪ Involution: the inward rolling or turning of a cell sheet to form new layers. It's common in deuterostomes ▪ Epiboly: the expansion of the cell sheet, which thins and spreads over the surface ▪ Convergence and extension: the narrowing of the cell sheet along one axis ( Zoology Page 47