EmSAT Achieve (UAE) · Biology

Organisms, Evolution and Ecosystems

26 practice questions, each with the answer and an explanation.

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Random questions from this topic, one at a time. You see the answer and the explanation straight after each one.

All 26 questions

  1. In humans, hemophilia A is an X-linked recessive disorder. A carrier woman (XᴴXʰ) and an unaffected man (XᴴY) have children. What is the probability that their son will have hemophilia?
  2. In a population in Hardy-Weinberg equilibrium, the frequency of a recessive allele (q) is 0.20. What percentage of the population is expected to be heterozygous carriers (2pq)?
  3. Which part of the human nephron is primarily responsible for establishing a high hypertonic osmotic gradient in the renal medulla via a countercurrent multiplier mechanism?
  4. According to Lindeman's efficiency rule in ecosystem ecology, approximately what fraction of energy is transferred from one trophic level to the next higher level?
  5. What type of natural selection favors individuals with intermediate phenotypes while acting against extreme phenotypic variants at both ends of the spectrum?
  6. Which chamber of the human heart pumps oxygen-rich blood into the systemic aorta under high systolic pressure?
  7. What hormone is secreted by the beta cells of the pancreatic islets of Langerhans in response to elevated blood glucose levels?
  8. In a dihybrid cross between two heterozygous pea plants (AaBb × AaBb) exhibiting complete dominance and independent assortment, what phenotypic ratio is expected among the progeny?
  9. What anatomical structures provide evidence of common ancestry because they share a fundamental skeletal layout despite serving divergent functional adaptations?
  10. During a neural action potential, what event is directly responsible for the rapid repolarization phase of the axonal membrane?
  11. What form of ecological succession takes place on newly formed barren volcanic basalt rock where no pre-existing soil or organic matter exists?
  12. Which class of immunoglobulin antibodies is predominantly found in external bodily secretions such as saliva, tears, colostrum, and mucus?
  13. In population dynamics, what term represents the maximum population size of a species that a particular environment can sustainably support without habitat degradation?
  14. Which type of speciation occurs when a physical geographic barrier (such as a mountain range or canyon) splits a biological population into two isolated gene pools?
  15. Which specialized immune cells mature in the thymus gland and orchestrate cell-mediated immune responses against intracellular pathogens?
  16. In the human respiratory system, what is the primary driving mechanism responsible for normal quiet exhalation at rest?
  17. Which biogeochemical cycle does not include a significant free gaseous reservoir in the Earth's atmosphere?
  18. What is the genetic relationship between alleles when a heterozygous individual exhibits a distinct intermediate phenotype between both homozygous parents (such as pink snapdragon flowers from red and…
  19. Which part of the human autonomic nervous system triggers the 'fight-or-flight' stress response by elevating heart rate, dilating bronchioles, and inhibiting digestion?
  20. In the human female menstrual cycle, what hormonal surge directly triggers ovulation around day 14 of an average 28-day cycle?
  21. What symbiotic ecological relationship occurs when one organism benefits while the other is neither helped nor harmed?
  22. Which nitrogenous waste product requires the least amount of water for excretion and is predominantly excreted by birds, reptiles, and desert insects?
  23. In a cross between a mother with blood type O (genotype ii) and a father with blood type AB (genotype I^A I^B), what are the possible blood types of their biological children?
  24. What vascular plant tissue conducts water and dissolved mineral ions upward from the root system to the leaves through dead, lignified tracheary elements?
  25. Which type of ecological pyramid is occasionally inverted (smaller at the base than at upper trophic levels) in marine open-ocean ecosystems?
  26. What evolutionary mechanism is primarily responsible for random changes in allele frequencies within small, isolated populations due strictly to chance events rather than natural selection?

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