January 2024 Living Environment Regents Written Response

One important vitamin that pregnant women should consume is folic acid. Folic acid is converted to folate in the body. It is well known that women who have a diet rich in folic acid show a decreased risk of having babies with neural tube (central nervous system) defects. Scientists conducted a study to determine the optimal amount of folic acid needed in the mother’s diet to prevent neural tube defects. The results are shown in the graph below.

                               The Effect of Flooding on Crops
Flooding can have a negative effect on certain food crops. Damage occurs because, in flooded soils, the oxygen concentration drops to near zero within 24 hours. This is because the water replaces most of the air in the soil.

                                               Fish Farming

Approximately 44% of the world’s fish produced for human consumption comes from aquaculture, which is the farming of fish and other aquatic organisms. This practice has increased the food supply and has also allowed over-fished wild populations to increase. As a result of genetic modifications, farm-raised fish usually grow faster and are typically larger than those in the wild.

However, there are some negative environmental effects associated with fish farming. Sea lice, a parasite of salmon, have spread quickly through some farms and have also been found in waters around the farms. Farm-raised fish sometimes escape through breaks in the sea cages. There is a concern that these escaped fish could negatively affect ocean ecosystems.

Researchers are studying methods that can be used to reduce the possible negative effects of fish farming. Improvements in engineering could make the sea cages where the farmed fish are raised more secure. Another suggestion involves raising farmed fish that have extra chromosomes. This would prevent them from reproducing with wild fish that have the normal number of chromosomes.

                                    Monarch Butterfly Decline

Monarch butterfly populations have fallen by 90% in less than 20 years. Monarchs west of the Rocky Mountains overwinter on the central coast of California. Their numbers have dropped from 1.2 million to only 200,000. East of the Rocky Mountains, monarchs overwinter in Mexico. In 2002, their numbers were down by about 500 million.

One reason for the decrease in monarch numbers is the increased planting of corn, cotton, and soybeans that are genetically modified (GM) to be resistant to weed killers containing glyphosate. With the increased use of these GM plants, increased amounts of the weed killers are being sprayed on fields where these crops are grown. These weed killers do not kill monarchs and other insects. They kill only plants such as milkweed that do not contain the resistance gene.

Mature adult monarch butterflies lay their eggs on milkweed plants. The larvae (caterpillars) eat only milkweed. Adults seek out flower nectar from a variety of plants. Stages of the monarch life cycle are represented below.

Predators find both the larvae and adult monarchs toxic and bad-tasting due to the presence of stored chemicals larvae ingest from the milkweed plants. 

These chemicals do not affect the monarchs, but do affect the cardiovascular and other systems of their predators.

                      Restoration of the Saratoga Creek Salt Marsh

Since the 1990s, students in coastal Massachusetts have been working with Mass Audubon and scientist Liz Duff, collecting data from the Saratoga Creek salt marsh. They are studying an invasive species of tall grass called Phragmites that is spreading and crowding out native plants and animals.

Salt marshes are shoreline wetland habitats where salt-loving plants experience the highs and lows of the tidal action of seawater. Phragmites prefers water that is low in salt. When the amount of salt in the marsh is low, Phragmites does better than native plants, and when the amount of salt in the marsh water is high, close to the level of seawater, native grasses do better than Phragmites.

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Evidence indicated that the storm drains built along the roads and homes near the shoreline added fresh water to the marsh, making it less salty, and altered sediment levels that reduced the salty ocean water coming into the marsh during high tide. The scientists thought that the presence of extra fresh water and sediments was the reason that Phragmites invaded the marsh.

In 1999, a restoration project to reverse the invasion of Phragmites began by digging a ditch along the road to reduce the freshwater runoff entering the marsh. A layer of sediment was also removed, allowing seawater to once again reach the marsh during high tide.

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Scientists worked with students collecting data along the same sections of the marsh every year. They used the data to calculate the frequency (abundance) and average height of Phragmites plants. The graphs represent the average height and the frequency of the Phragmites in the Saratoga Creek salt marsh.

                              Gulf Coast Suffers from Red Tide

Florida residents have been experiencing the consequences of “red tides,” excessive growth of the algae Karenia brevis (K. brevis). This species of algae is a single-celled organism that releases brevetoxin, a dangerous nerve toxin that can be fatal to animals. Even though shellfish, which can eat K. brevis, are not affected by this algae, many fish and other marine organisms, such as dolphins and manatees, are paralyzed by the toxin. This toxin prevents the organisms from carrying out the process of cellular respiration.

The red tides usually appear in late summer or early fall. Researchers are not sure what causes red tides. A variety of factors seem to be associated with their occurrence. These factors include warmer ocean temperatures, heavy rainfall, and pollution from fertilizers.

                                Northern Quolls vs the Cane Toads

Poisonous South American cane toads were introduced into Australia in 1935 in an attempt to control a beetle that was eating sugar cane crops. However, the toads did not control the beetles and, instead, they caused an environmental disaster. Today, the toad population is estimated to be greater than 200 million.

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As the invasive toads spread westward across northern Australia, many native species were negatively affected. For example, in the years since the toads’ introduction, scientists have observed that the entire population of the northern quoll, a small squirrel-sized carnivore, has declined more than 75%.

The decline is due to the fact that the quolls mistake the poisonous toads for something that they can safely eat. When they eat the toads, they die from the poison that the toads produce. The northern quolls may soon become extinct if something cannot be done to save them.

Recently, some quolls were found to have a genetic trait that makes them uninterested in preying on the toads. Scientists have now discovered that these quolls with “toad-smart genes” can pass them on to their offspring. The scientists plan to release quolls that avoid eating the toads into native populations, hoping that they will breed and produce offspring that also avoid eating the toads, thus saving the species from extinction.

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The existing species of South American bats depend upon a wide variety of food sources, yet they have evolved from a single population of insect eating bats. The diagram below summarizes the feeding habits of some species of South American bats.

Four model cells were prepared by using dialysis tubing and filling each of them with the same solution. Each of the model cells originally weighed 20 grams. Next, each model cell was placed in a beaker. Each of the four beakers contained a different concentration of water. After 24 hours, the mass of each model cell was measured and recorded in the data table below.

The band labeled X on the image of the gel below represents a segment of DNA associated with the production of a unique protein. The protein is being tested to determine if it might be useful in treating a disease found in horses. DNA from one of eight different plants, each thought to be from a different species, was injected into each of eight lanes of the gel. It was then compared to the plant in the first lane, which is known to produce this unique protein.

During exercise pulse rate may change. The pulse rate indicates the rate at which the heart is beating.