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During early vertebrate development, cells on the dorsal side of the embryo begin to fold inward to form the neural tube, which later develops into the brain and spinal cord. Which developmental process is occurring?
A. Neurulation
B. Cleavage
C. Gastrulation
D. Organogenesis
A. Neurulation
During neurulation, the neural plate folds inward to form the neural tube, which eventually becomes the central nervous system. If neurulation fails properly, defects such as spina bifida may occur.
Other stages of development include:
Cleavage – early rapid cell division
Gastrulation – formation of germ layers
Organogenesis – development of organs from germ layers
A physician examining a patient explains that the chamber of the heart responsible for pumping oxygenated blood to the entire body through the aorta must be functioning properly to maintain adequate circulation. Which chamber of the heart performs this function?
A. Right atrium
B. Right ventricle
C. Left atrium
D. Left ventricle
D. Left ventricle
The Left ventricle is responsible for pumping oxygenated blood into the systemic circulation through the aorta. Because it must send blood throughout the entire body, it has the thickest muscular wall of all heart chambers.
The four chambers of the Heart each have specific roles:
Right Atrium
Receives deoxygenated blood from the body via the superior and inferior vena cava
Right Ventricle
Pumps deoxygenated blood to the lungs through the pulmonary artery
Left Atrium
Receives oxygenated blood from the lungs through the pulmonary veins
Left Ventricle
Pumps oxygenated blood through the aorta to supply the entire body
Body → Right Atrium → Right Ventricle → Lungs → Left Atrium → Left Ventricle → Body
A parasite transmitted through mosquito bites infects red blood cells and causes cycles of fever and chills. Which organism is responsible?
A. Trypanosoma
B. Plasmodium
C. Giardia
D. Entamoeba
B. Plasmodium
The parasite Plasmodium causes malaria. It is transmitted by female Anopheles mosquitoes.
The parasite infects:
Liver cells initially
Red blood cells later
The periodic rupture of infected RBCs causes cyclic fever.
A predator species declines drastically in an ecosystem, causing prey populations to increase dramatically. This situation demonstrates:
A. Mutualism
B. Predator-prey imbalance
C. Symbiosis
D. Photosynthesis
B. Predator-prey imbalance
Predators regulate prey populations. If predators decline, prey populations may grow excessively, leading to ecosystem imbalance.
Animals that maintain constant internal body temperature are called:
A. Ectotherms
B. Endotherms
C. Poikilotherms
D. Invertebrates
B. Endotherms
Animals that maintain a relatively constant internal body temperature regardless of environmental conditions are called Endothermy animals or endotherms.
Examples include:
mammals
birds
These animals produce heat internally through metabolic processes, allowing them to remain active in both warm and cold environments.
A. Ectotherms
Animals whose body temperature depends largely on the external environment. Examples include reptiles, amphibians, and many fish.
C. Poikilotherms
Organisms whose body temperature varies significantly with environmental temperature. Many ectothermic animals are also poikilothermic.
D. Invertebrates
Animals without a backbone, such as insects, worms, and mollusks. This classification refers to body structure, not temperature regulation.
A scientist observes that cells from the ectoderm layer differentiate into nerve tissue. Which structure is most likely derived from the ectoderm?
A. Liver
B. Skin epidermis and nervous system
C. Heart muscle
D. Digestive tract lining
B. Skin epidermis and nervous system
The ectoderm forms structures related to the body's outer surface and nervous system.
Major germ layer derivatives include:
Ectoderm
Skin epidermis
Nervous system
Hair and nails
Mesoderm
Muscles
Bones
Circulatory system
Endoderm
Digestive tract
Respiratory organs
Liver and pancreas
A patient with diabetes is diagnosed with insufficient production of the hormone insulin, which regulates blood glucose levels. Which organ of the endocrine system primarily produces this hormone?
A. Thyroid gland
B. Pancreas
C. Adrenal glands
D. Pituitary gland
B. Pancreas
The pancreas has both digestive and endocrine functions. Its endocrine portion contains clusters of cells called the islets of Langerhans, which secrete hormones into the bloodstream.
Important pancreatic hormones include:
Insulin
Produced by beta cells
Lowers blood glucose by promoting uptake of glucose into cells and storage as glycogen
Glucagon
Produced by alpha cells
Raises blood glucose by stimulating glycogen breakdown in the liver
Other endocrine glands include:
Pituitary gland
Often called the “master gland” because it regulates other endocrine glands
Thyroid gland
Regulates metabolism through hormones such as thyroxine
Adrenal gland
Produces adrenaline and cortisol, which are important in stress responses
The endocrine system works together to maintain homeostasis, regulating processes such as metabolism, growth, reproduction, and blood glucose levels.
A human becomes infected with a parasitic worm after consuming undercooked pork. Which parasite is most likely responsible?
A. Taenia solium
B. Ascaris lumbricoides
C. Schistosoma japonicum
D. Enterobius vermicularis
A. Taenia solium
Taenia solium infects humans through undercooked pork containing larval cysts.
It can cause:
Intestinal infection
Cysticercosis, if larvae infect tissues
Tapeworms belong to the flatworm class Cestoda.
Scientists track the movement patterns of animals using satellite collars. This method helps study:
A. Animal migration
B. Mass extinction
C. Evolution
D. Mutation
A. Animal migration
Satellite tracking allows researchers to study animal migration routes, habitat use, and seasonal movements. This information is critical for wildlife conservation planning.
A parasite that lives inside the body of its host is called:
A. Endoparasite
B. Ectoparasite
C. Mutualist
D. Commensal
A. Endoparasite
An Endoparasite is a parasite that lives inside the host’s body, often within organs, tissues, or blood.
Examples include:
Taenia solium
Plasmodium falciparum
Ascaris lumbricoides
These parasites obtain nutrients from the host and may cause disease.
A. Ectoparasite
Parasites that live on the surface of the host, such as lice or ticks.
C. Mutualist
An organism engaged in mutualism, where both species benefit.
D. Commensal
In commensalism, one organism benefits while the other is neither helped nor harmed.
In some animals, embryonic cells can develop into any type of cell in the body, including extraembryonic tissues. What is this property called?
A. Multipotency
B. Pluripotency
C. Totipotency
D. Differentiation
C. Totipotency
Totipotent cells can form all cell types, including the entire organism and supporting tissues.
Levels of stem cell potential include:
Totipotent – can form entire organism
Pluripotent – can form most body cell types
Multipotent – limited to certain tissues
Early embryonic cells in animals are typically totipotent.
An animal with radial symmetry, tentacles, and stinging cells called nematocysts is most likely a member of which phylum?
A. Mollusca
B. Arthropoda
C. Cnidaria
D. Annelida
C. Cnidaria
Members of the phylum Cnidaria include:
Jellyfish
Sea anemones
Corals
They possess nematocysts, specialized stinging structures used for capturing prey and defense.
Which parasitic protozoan causes amoebic dysentery?
A. Entamoeba histolytica
B. Giardia lamblia
C. Trypanosoma cruzi
D. Plasmodium falciparum
A. Entamoeba histolytica
Entamoeba histolytica is the causative agent of amoebiasis or amoebic dysentery.
Key features:
Transmitted through fecal-oral contamination (contaminated food or water)
Infective stage: cyst
Causes bloody diarrhea, abdominal cramps, and intestinal ulcerations
The parasite can invade the intestinal wall and sometimes spread to the liver, causing amoebic liver abscess
A distinguishing feature is the parasite's ability to destroy intestinal tissue, which leads to blood and mucus in stool.
- Giardia lamblia causes giardiasis, a common waterborne parasitic infection.
Key characteristics:
Transmitted through contaminated water, often from streams or poorly treated drinking water
Infective stage: cyst
Parasite attaches to the small intestinal lining but does not invade tissues
Symptoms include:
Watery diarrhea
Foul-smelling, greasy stool
Bloating and gas
Malabsorption
- Trypanosoma cruzi is the causative agent of Chagas disease.
Transmission:
Spread by triatomine bugs (“kissing bugs”)
Disease characteristics:
Acute phase may include fever and swelling near the bite site
Chronic infection can damage the heart and digestive system
Major complications:
Cardiomyopathy
Enlarged esophagus (megaesophagus)
Enlarged colon (megacolon)
-Plasmodium falciparum is one of the species that cause malaria, the most severe form of the disease.
Transmission:
Spread through the bite of infected Anopheles mosquitoes
Disease mechanism:
The parasite infects liver cells first, then red blood cells
Symptoms include:
Cyclic fever and chills
Severe anemia
Organ complications such as cerebral malaria
An ecosystem supports a maximum number of individuals of a species without degrading resources. This limit is called:
A. Population density
B. Carrying capacity
C. Ecological niche
D. Food chain
B. Carrying capacity
Carrying capacity is the maximum population size that an environment can sustain with available resources.
Factors influencing carrying capacity include:
Food availability
Water supply
Habitat space
Predation
The largest group of animals in terms of species diversity belongs to which phylum?
A. Mollusca
B. Arthropoda
C. Annelida
D. Echinodermata
B. Arthropoda
The phylum Arthropoda is the largest and most diverse group of animals on Earth, containing over one million described species, with many more yet to be discovered.
Key characteristics of arthropods include:
Jointed appendages
Segmented body
Chitinous exoskeleton
Growth through molting (ecdysis)
Examples include:
insects (beetles, butterflies, ants)
arachnids (spiders, scorpions)
crustaceans (crabs, shrimp)
myriapods (centipedes, millipedes
A patient suffers damage to the alveoli in the lungs. Which physiological process would be directly affected?
A. Blood circulation
B. Gas exchange
C. Food digestion
D. Hormone secretion
B. Gas exchange
Alveoli are tiny air sacs in the lungs where gas exchange occurs. Oxygen diffuses into the bloodstream while carbon dioxide diffuses out.
This process relies on:
Thin alveolar membranes
Large surface area
Rich capillary network
Damage to alveoli can impair respiratory efficiency.
An invertebrate animal has a segmented body, jointed appendages, and an exoskeleton made of chitin. Which phylum does it belong to?
A. Mollusca
B. Arthropoda
C. Echinodermata
D. Platyhelminthes
B. Arthropoda
The phylum Arthropoda includes:
Insects
Crustaceans
Arachnids
Their defining features include:
Jointed appendages
Segmented bodies
Chitinous exoskeleton
Arthropods are the most diverse group of animals.
A conservation biologist studies how deforestation affects the population size of a forest mammal. Which ecological concept is being investigated?
A. Mutation
B. Evolution
C. Co-evolution
D. Population dynamics
D. Population dynamics
Population dynamics examines changes in population size due to:
Birth rate
Death rate
Immigration
Emigration
Habitat destruction can dramatically alter wildlife populations.
A scientist studies how wolves regulate deer populations in a forest. This relationship is an example of:
A. Predation
B. Mutualism
C. Commensalism
D. Competition
A. Predation
Which parasite is transmitted through contaminated water and penetrates human skin during contact with infected water?
A. Schistosoma
B. Taenia
C. Ascaris
D. Giardia
A. Schistosoma
Schistosoma is a parasitic flatworm (trematode) that causes schistosomiasis, a disease commonly found in tropical and subtropical regions.
Transmission occurs when:
Larvae called cercariae are released from infected freshwater snails.
When humans swim, bathe, or wade in contaminated water, the larvae penetrate the skin directly.
The parasites then enter the bloodstream and mature in blood vessels.
Common symptoms include:
skin irritation
fever
liver and intestinal damage
enlarged spleen or liver in severe infections
Taenia (tapeworms) infect humans through consumption of undercooked meat, particularly pork or beef containing larval cysts.
Example:
Taenia solium – pork tapeworm
Taenia saginata – beef tapeworm
Ascaris lumbricoides infects humans through ingestion of eggs in contaminated food, water, or soil.
After ingestion:
larvae hatch in the intestine
migrate through lungs
return to the intestine to mature
Giardia lamblia causes giardiasis, a diarrheal disease transmitted through drinking contaminated water.
Symptoms include:
diarrhea
bloating
malabsorption
greasy stools
The nephron is the functional unit of which organ?
A. Liver
B. Heart
C. Lung
D. Kidney
D. Kidney
The Nephron is responsible for filtering blood and producing urine.
Key nephron functions include:
Filtration in the glomerulus
Reabsorption in the tubules
Secretion of waste substances
Millions of nephrons work together to regulate water balance and waste removal.
A marine animal with spiny skin, radial symmetry, and a water vascular system belongs to which phylum?
A. Echinodermata
B. Annelida
C. Mollusca
D. Porifera
A. Echinodermata
Members of Echinodermata include:
Starfish
Sea urchins
Sea cucumbers
They possess a water vascular system used for locomotion and feeding.
An endangered species has a very small population and low genetic diversity. Which risk does this situation increase?
A. Photosynthesis failure
B. Inbreeding depression
C. Rapid evolution
D. Increased mutation rate
B. Inbreeding depression
Small populations often suffer from inbreeding, which increases the likelihood that harmful recessive genes will be expressed.
Which animal group is considered an important indicator of ecosystem health due to its sensitivity to environmental changes?
A. Amphibians
B. Mammals
C. Birds
D. Reptiles
A. Amphibians
Amphibians are highly sensitive to environmental conditions because of:
Permeable skin
Aquatic and terrestrial life stages
Their population declines often signal environmental problems.
The Philippine eagle is one of the most iconic endangered species in the Philippines. Its population has declined mainly due to deforestation and hunting. Which of the following best describes the primary conservation strategy used to protect this species?
A. Establishing marine protected areas
B. Captive breeding and forest habitat protection
C. Increasing agricultural land use
D. Introducing non-native predators to control prey
B. Captive breeding and forest habitat protection