Poikilotherm

Some animals change with the air.

Their bodies get warm or cold. This happens when the weather changes. They do not stay the same heat.

These animals can be many things. Some are fish or snakes. Some are frogs. Even a sloth is one.

Changing heat helps them save food. They do not need much energy. They often sit and wait for food. This is a smart way to live.

Some animals do not keep the same body heat. We call these animals poikilotherms. Their body temperature changes with the world around them.

Most poikilotherms are fish, reptiles, or amphibians. Some rare mammals like sloths are also poikilotherms. These animals do not use much power to stay alive. In fact, they only need about 5 to 10% of the energy that other animals need. Because they save so much energy, they often sit and wait for food.

To work well, these animals use special tools. They might use behaviors to stay warm. For example, lizards bask in the sun. Some bees stay warm by shivering their muscles. Other animals, like tuna, use a special part called the rete mirabile. This part helps them keep heat inside their bodies. Some animals also grow very large to stay warm. This is called gigantothermy. Large bodies lose heat more slowly than small bodies. Because they use less food, many poikilotherms can live in large groups.

A poikilotherm is an animal with a changing body temperature. The name comes from Greek words meaning "varied" and "heat."

These animals do not keep their internal heat the same. Instead, their temperature changes with the world around them. Most of these changes happen because the environment changes. This can be a hard job for the animal. High heat can even change how their tiny body parts work. They must find ways to survive these shifts.

To stay alive, poikilotherms use many clever ways to work. Chemical reactions in their bodies change speed when it gets hot or cold. To fix this, they may have several enzyme systems. Enzymes are tools that help chemical reactions happen. They might have four to ten different systems to work at different temperatures. This often means they have larger and more complex genomes. A genome is the set of instructions for a living thing. This helps them function even when the weather shifts.

Many different creatures are poikilotherms. You can find them among fish, amphibians, and reptiles. Many invertebrates also belong to this group. There are even a few rare mammals that fit this description. The naked mole-rat and the sloth are two examples.

Some animals use behavior to manage their heat. Lizards and snakes might bask in the sun to get warm. They may seek shade at noon to stay cool. Yellow-faced bumblebees use a different trick. They shiver their flight muscles to keep their eggs warm.

Poikilotherms are very good at saving energy. They do not use their own bodies to heat or cool themselves. Because of this, they only need 5 to 10% of the energy that homeotherms need. A homeotherm is an animal that keeps a steady temperature. This low energy need means they often use a sit-and-wait strategy for food. They do not chase prey like a cat might. This allows many poikilotherms to live in one area. A single food source can support many more of them.

Some animals have even more special ways to handle heat. Tuna use a mechanism called the rete mirabile. This helps them keep heat inside their bodies. They also keep their swimming muscles near their center. This helps them avoid losing heat through their skin. Other animals use gigantothermy to stay warm. This means they grow to a very large size. Large bodies lose heat more slowly than small bodies. This is seen in sea turtles and some animals from the ice ages.

A poikilotherm is an animal whose internal body temperature varies considerably. The term comes from the Greek words "poikilos," meaning varied or dappled, and "therme," meaning heat.

This is the opposite of a homeotherm. A homeotherm is an animal that maintains thermal homeostasis, or a steady internal temperature. Most poikilotherms experience temperature fluctuations because of changes in their ambient environment. These animals must adapt to significant environmental stress. For example, high temperatures can cause protein denaturation, which is when proteins unfold and lose their shape. Heat can also alter the order of lipids in cell membranes. Because of these risks, poikilotherms must be able to function across a much wider range of temperatures than homeotherms.

To manage these shifts, poikilotherms use complex internal mechanisms. The speed of chemical reactions in a body changes based on the temperature. To keep working, a poikilotherm may possess four to ten different enzyme systems. These systems allow important chemical reactions to occur at different temperatures. Because of this need for multiple systems, poikilotherms often have larger and more complex genomes. A genome is the complete set of genetic instructions for an organism. Frogs are a notable example of animals with large genomes. Their complexity is partly due to their development and their need for these varied enzyme systems.

Poikilotherms belong to many different groups of life. You can find them among many invertebrate animals. They are also common among vertebrates, specifically certain fish, amphibians, and reptiles. While most mammals are homeotherms, there are rare exceptions. The naked mole-rat and the sloth are both mammals that function as poikilotherms.

Some ectotherms, which are animals that rely on external heat, may actually act as practical homeotherms. This happens if they seek out environments that stay at a constant temperature. This distinction makes the term "poikilotherm" more useful than the common phrase "cold-blooded."

Many poikilotherms use behavioral adaptations to manage their heat. Lizards and snakes often bask in the sun during the early morning and late evening. They may seek shelter around noon to avoid the hottest part of the day. Invertebrates use behavior too. Yellow-faced bumblebee queens and workers protect their eggs through incubation. They warm the brood by touching their abdomens to the eggs. They generate this heat by shivering their flight muscles without actually flying. Termites also use structural behavior. Termite mounds are often oriented north-to-south. This helps them absorb maximum heat at dawn and dusk while minimizing heat at noon.

Some animals have developed highly specialized biological structures for heat management. Tuna use a heat exchange mechanism called the rete mirabile. This system helps them keep heat inside their bodies and minimizes heat loss through their gills. They also place their swimming muscles near the center of their bodies to reduce surface heat loss. Other animals use a strategy called gigantothermy. This involves growing to a very large size to reduce heat loss. As body volume increases, it grows faster than body surface area. This means large animals, like sea turtles or ice-age megafauna, have less surface area per unit of volume to lose heat.

One of the greatest advantages of being a poikilotherm is energy efficiency. Because they do not use metabolism to heat or cool themselves, their total energy requirement is very low. For the same body weight, a poikilotherm needs only 5% to 10% of the energy required by a homeotherm. This low energy cost influences how they hunt. Many poikilotherms use a "sit-and-wait" strategy rather than chasing prey. This efficiency also affects ecology. A single food source can support a much higher density of poikilothermic animals than homeothermic ones. Consequently, poikilotherms often have much shorter generations, sometimes lasting weeks rather than years.

In the study of ecology, the relationship between predators and prey is often different for these animals. The predator-prey ratio is usually higher in poikilothermic fauna. However, homeotherms can sometimes outcompete them. If they occupy the same niche, a homeotherm might drive a poikilotherm to extinction. This is because homeotherms can gather food more effectively throughout the day. For example, a chimpanzee can actively seek out army ants with sticks, while a poikilotherm might simply wait. Finally, poikilothermia is a term used in medicine. It describes a loss of normal temperature regulation. This can occur during REM sleep in humans or due to certain medical conditions like acute limb ischemia.