Mr. Dan Kuiper, science teacher in Covenant Christian High School and member of Hope PRC in Walker, Michigan

Belgic Confession, Article 2 teaches that the creation is an elegant book that leads us to contemplate the wondrous works of God. This is a reflection of the truth taught in Job 12:7-9: “But ask now the beasts, and they shall teach thee; and the fowls of the air, and they shall tell thee: Or speak to the earth, and it shall teach thee: and the fishes of the sea shall declare unto thee. Who knoweth not in all these that the hand of the Lord hath wrought this?” Since God is pleased to reveal Himself in the creation, and the whole earth declares God’s glory, it is good for the child of God to ponder and marvel at the things that the Lord has made.

In particular, God’s tender mercies and sovereign care are displayed in the creation. These attributes are especially evident as we consider how God upholds animals through even the harshest weather. During the winter, temperatures plummet well below freezing in the northern half of the United States. In such cases, we can be thankful for the homes God has given and for means to heat our homes. But what about animals that must remain outdoors? How do they survive the plummeting temperatures? We can be sure that God, “after He created all things, did not forsake them, or give them up to fortune or chance, but that He rules and governs them according to His holy will” (BC, Art. 13). God, in many marvelous ways, provides for the safety and survival of even the smallest of animals through the winter months.

Spring peepers

One of the most fascinating examples of this is the spring peeper. Spring peepers are delicate, one-inch long frogs that belong to a group known as “chorus frogs.” These frogs live in the eastern United States and are best known for their near-deafening calls. Travel to the forests of northern Michigan in the spring and throughout the night your ears will be filled with the calls of these tiny frogs. During the winter, spring peepers burrow into soft mud near ponds or settle under logs and leaf litter on the forest floor, then enter a state of inactivity.

During this stage of inactivity, spring peepers freeze nearly solid. Like all frogs, spring peepers are ectotherms. Ectotherms are organisms that depend on the external environment to maintain body temperature. Their body temperature, therefore, can vary significantly depending on the outside temperature. As temperatures plummet, so will their body temperature. Up to two-thirds of the water in their bodies can freeze, sometimes for days at a time. The drop in their body temperature also causes their hearts to completely stop beating. Yet, they are alive. When warmth returns in the spring, these frogs will come out of this dormant state and once again form a powerful chorus that fills the night with songs of praise to the Creator.

One important factor that allows these frogs to survive the freezing of water in their bodies is the ability to prevent this freezing from taking place inside their cells. Cells contain important organelles needed for proper cell function. Such organelles include the nucleus and mitochondria. The nucleus contains the DNA that gives instructions for all the activities of the cell while the mitochondria produce the energy needed for cell function. If ice forms within cells, the jagged edge of ice crystals will damage these organelles and result in cell death. When many cells within an organ die, the organ fails and ultimately the organism itself dies. Thus, it is important that any freezing that occurs be limited to the fluids outside of cells (known as the extracellular fluid).

Freezing point depression

The spring peeper must increase the concentration of dissolved substances inside its cells to prevent freezing from taking place there. In its liquid phase, water molecules move rapidly and randomly past one another. When water transitions to its solid phase (ice), its molecules take on a very ordered, crystal lattice structure. Pure water makes this transition at 32oF (0oC), which is its freezing point. However, when a substance is dissolved in water (for example, salt), the freezing point will decrease since the dissolved particles interfere with the ability of water to form this crystal lattice structure. The decrease in freezing point caused by dissolving a substance in water is referred to as freezing point depression. This concept is commonly used to melt ice from the roadway in the winter. The salt spread onto the road dissolves into the thin layer of water at the surface of ice, decreasing its freezing point. This saltwater mixture will remain liquid at a lower temperature, and ice is eliminated from the road surface.

A couple things about freezing point depression are worth noting. First, salt is not the only substance that can dissolve in water and lower its freezing point. Any substance that dissolves in water will do the trick. An example of one such substance is sugar. Second, the degree to which freezing point decreases depends on the amount of substance dissolved. Add a small amount of salt (or sugar) to water and its freezing point will decrease only a little below 32oF. Add more salt to water and its freezing point decreases further, though there is a limit, which explains why in some cases it can become too cold for salt to be effective at melting ice.

The property of freezing point depression is one of the means used by God to preserve the life of spring peepers through the winter. The inside of a spring peeper’s cells contain dissolved sugars and electrolytes (salts). Most of the year the concentration of these dissolved substances is not very high. Therefore, the freezing point of water inside the spring peeper’s cells is “naturally” around 31oF (just one degree below water’s freezing point). The mud and leaf litter (along with fallen snow) that spring peepers inhabit in the winter help insulate their bodies so they do not face the full force of the winter cold. However, these locations can still experience temperatures as low as 21oF, well below the temperature at which the water inside their cells would normally freeze and damage the organelles. Therefore, spring peepers must have a means to further decrease the freezing point of water in their cells.

The decrease in freezing point is accomplished by flooding the organs with a sugar called glucose. The liver of a spring peeper is filled with glycogen, which is a molecule made of long chains of glucose. These frogs build up large quantities of this molecule throughout the year. When their body temperature drops in the winter, spring peepers break glycogen into its individual glucose molecules and disperse them to organs throughout the body. The glucose functions in two ways to increase concentration of dissolved particles within the cells. First, a large amount of this glucose enters the extracellular space outside the cells. The high concentration of sugar outside the cells draws water out of the cells in a process called osmosis. Much of this water is converted to ice crystals by special proteins in the extracellular space. Interestingly, the ice in the extracellular fluid plays a role in insulating the cells. Second, some of the glucose released by the liver is pumped into the cells. The combination of water leaving the cells and extra dissolved sugars being pumped into the cells results in a decrease in freezing point sufficient to allow spring peepers to endure temperatures of 21oF (and sometimes lower) without the water inside their cells freezing. This is vital to their survival.

God’s tender mercies

The cold of winter is a bitter and deadly force. It seems impossible that such a tiny, fragile frog is able to survive such conditions. In Psalm 147:17, the psalmist asks the rhetorical question, “Who can stand before [God’s] cold?” The clear answer is that none are able to stand according to their own strength. Left to themselves, all creatures would perish in the face of such powerful cold. And yet, year after year, spring peepers, along with many other creatures, survive the dreaded winter. The only explanation for their survival is that God is able to provide spring peepers what they are not able to provide for themselves. In His wisdom and by His power, God has ordained and maintains the property of freezing point depression for the protection of this small frog. At God’s voice, glucose molecules are released from the frog’s liver. Not a single ice crystal forms apart from His command. These frogs remain in a near lifeless state through the winter. They toil not! Yet God, by His power, cares for them and preserves their lives.

As the spring peeper depends upon God to supply what it needs for the preservation of its life, so must the child of God. This is true of our physical needs. All that we need for the body comes from God. When these needs are supplied, we must give thanks to God alone for His provision. In a greater sense, this is true of our spiritual needs. We are sinners, dead in sin by nature. As God’s children, we acknowledge that our best works are as filthy rags before the holiness of God and we confess we have no power to deliver ourselves from the misery of our sin. Therefore, we rejoice in the knowledge that God’s mercy is towards us, His dear children. He has provided for us through Jesus Christ. The blood of our Savior has been shed to cover our sins. Our souls have been redeemed! We were dead in sins, “but God, who is rich in mercy, for his great love wherewith he loved us, even when we were dead in sins, hath quickened us together with Christ” (Eph. 2:4-5). Oh, what a Savior! On account of His suffering and death, we are not consumed.

God, who has saved us, is faithful. His mercies are new every morning (Lam. 3:23), they endure forever (Ps. 136), and “his tender mercies are over all his works” (Ps. 145:9). He who is able to provide for the spring peeper in the harshest of conditions is able to preserve His people through the greatest of afflictions. He sees, hears, and knows all things. In His mercy, God directs every detail of the creation for the salvation and preservation of His people. Nothing can separate us from His love.

As we ponder these things, may we give thanks for the mercy of our God by which He upholds the creatures of the earth and preserves us, body and soul. “My mouth shall speak the praise of the Lord; and let all flesh bless his holy name for ever and ever” (Ps. 145:21). If we should fail to praise Him for His sovereign care, all of creation, even the smallest of beasts, will still praise Him. Glory be to God!