Vasodilation allows more heat to escape via the blood vessels. Thus, in a cold environment, this would be counterproductive. Vasoconstriction shrinks the blood vessels so that less heat escape. Shivering thermogenesis produces heat by converting ATP to kinetic energy. Thermoregulation is the term describing organisms maintaining their internal body temperature.

An ectotherm relies on external sources to regulate its body temperature. The snake lies on the dark rock to absorb heat energy from the sun, to warm its body during the cool day. Animals that hibernate, such as bears, cannot be ectotherms. Hibernating animals downregulate their body’s metabolism and thus body temperature; ectotherms cannot control their body temperature. Humans are endotherms, and like other endotherms, shiver when cold to increase their body temperature through expending energy (“shivering thermogenesis”). Dogs are endotherms, and pant when hot to cool their body temperature by expelling heat.

Endotherms maintain a relatively constant body temperature, independent of their external environment. They can shiver when cold to increase their body temperature through expending energy (“shivering thermogenesis”).

An ectotherm relies on external sources to regulate its body temperature. Endotherms maintain a relatively constant body temperature, independent of their external environment. To regulate their body temperature, endotherms have a higher

Producers are always the lowest level of a trophic hierarchy, and consist of the autotrophs in the system. Organisms that feed off of producers are considered primary consumers.

In this example, the grasses are the producers. Both the rabbits and the turtles will be primary consumers.

An organism that feeds on primary consumers is considered a secondary consumer.

Autotrophs are organisms that are capable of generating biological energy from inorganic sources, such as sunlight in the case of photoautotrophs. Cyanobacteria are thought to be the prokaryotic precursor to chloroplasts through the endosymbiotic theory because they are able to perform photosynthesis. Cyanobacteria are, thus, photoautotrophs. Green algae are another type of photoautotroph.

Heterotrophs use organic materials from the environment to general energy. Animals are heterotrophs, including cows.

Saprotrophs, many of which are fungi, gain nutrients from decaying organic material. Mushrooms are saprotrophs.

Ecology is essentially the study of all the living things on the planet and their relationships with each other. Ecology can be organized into levels: population, community, ecosystem, and biosphere. A population is a group of organisms that belong to the same species, share an area, and can reproduce with each other. A community is composed of the different species that can be found in a geographical location. An ecosystem encompasses all abiotic and biotic factors in an area. The biosphere refers to those parts of the earth that are able to support and sustain life.

Within ecosystems, there is always a transfer of energy, usually from one organism to another. There is also energy transfer between abiotic and biotic factors. The caterpillar and lion are examples of consumers because they are unable to make their own food and must rely on other living organisms for energy. Consumers are subdivided into herbivores, omnivores, and carnivores. Producers are those living things in the ecosystem that generally produce energy using photosynthesis or light. Organisms that break down dead or decaying matter for energy are called decomposers. These are most likely bacteria, fungi (such as mushrooms), and some worms.

A flower in this example is a producer, which means it will make its own energy through photosynthesis. As a result, the flower must be the first element of our chain; food chains will always start with a producer. The caterpillar, frog, and snake are consumers, meaning they will need other organisms for energy.

A producer is an organism that makes its own food from the energy of the sun via photosynthesis. Green algae is a producer; it has chlorophyll pigments and can make glucose via photosynthesis. A frog is a consumer; a worm is a decomposer; a fungus is a saprophyte; a bear is a consumer.