Free NGSA Practice Test

Phenomenon: A 5th-grade science class investigates forest decomposition. They place 100 grams of dry fallen leaves into two identical glass terrariums kept under the same moisture and temperature conditions: • Terrarium A (Sterilized Soil): After 60 days, 95 grams of leaf matter remains mostly unchanged. • Terrarium B (Forest Soil with Earthworms and Fungi): After 60 days, only 15 grams of leaf fragments remain, replaced by dark, nutrient-rich soil (humus). Based on this data, which conclusion best explains the essential function of decomposers in an ecosystem?

Investigation: A 5th-grade student builds an electrical test circuit containing a 1.5V battery, insulated copper wires, and a small incandescent bulb with an open gap. The student tests four different everyday objects across the gap to see if the bulb lights up: • Object 1 (Steel Paperclip): Bulb shines brightly • Object 2 (Plastic Ruler): Bulb stays off • Object 3 (Copper Penny): Bulb shines brightly • Object 4 (Wooden Toothpick): Bulb stays off Which general pattern about electric circuits and materials is directly supported by this evidence?

Geological Data: Marine geologists mapping the Pacific "Ring of Fire" record deep-ocean bathymetry and seismic activity along the boundary where the dense oceanic Pacific Plate collides with the lighter continental North American Plate. Their instruments reveal: 1. A deep oceanic trench forming along the subduction zone boundary. 2. Deep earthquake hypocenters that get progressively deeper inland underneath the continent. 3. A continuous chain of active stratovolcanoes situated parallel to the coastline 150 km inland. Which plate tectonic model correctly accounts for the formation of the volcanic mountain chain?

Experiment: An 8th-grade science team places several sprigs of the aquatic plant Elodea into test tubes filled with water containing bromothymol blue (BTB) indicator, which turns yellow in the presence of dissolved carbon dioxide (acidic) and turns blue when carbon dioxide is absent: • Tube 1 (Elodea in bright sunlight for 24 hours): BTB solution turns from yellow to bright blue. • Tube 2 (Elodea in total darkness for 24 hours): BTB solution turns from blue to bright yellow. • Tube 3 (Control tube with no plant in sunlight for 24 hours): BTB solution remains unchanged. Which biological explanation best explains the contrasting color changes in Tubes 1 and 2?

Population Genetics: A biology laboratory cultures a population of 10,000,000 Staphylococcus aureus bacteria in a nutrient broth containing low concentrations of the antibiotic methicillin. Initially, 99.99% of the bacteria are killed. However, 12 surviving bacterial cells possess a spontaneous mutation in the mecA gene, which alters a penicillin-binding protein and prevents the antibiotic from binding. After 72 hours (approx. 140 bacterial generations) in the same antibiotic-treated environment, the population reaches 10,000,000 cells again, and all tested cells express the mutated mecA gene. Which evolutionary mechanism is demonstrated by this data?

Environmental Data Analysis: Marine scientists studying Narragansett Bay analyze seasonal water quality data collected across four monitoring stations over a 12-month period. They observe the following sequence of events: • May–June: Heavy spring rains wash agricultural fertilizer runoff (high in dissolved nitrates and phosphates) down the Blackstone and Providence Rivers into the upper bay. • July: Surface phytoplankton populations explode in a massive algal bloom, creating high surface dissolved oxygen (12 mg/L). • August: The algal bloom dies and sinks to the bottom; benthic bacterial populations multiply exponentially as they decompose the dead algae, causing bottom-water dissolved oxygen levels to plummet below 1.5 mg/L (hypoxia). • Late August: Massive die-offs of benthic flounder, quahogs, and crabs are recorded on the bay floor. Which intervention would most effectively address the root cause of this annual estuarine hypoxia cycle?