Food is chemical energy stored in organic molecules. Food provides both the energy to do work and the carbon to build bodies. Because most autotrophs transform sunlight to make food, we call the process they use photosynthesis. Only three groups of organisms - plants, algae, and some bacteria - are capable of this life-giving energy transformation. Autotrophs make food for their own use, but they make enough to support other life as well.
Almost all other organisms depend absolutely on these three groups for the food they produce. The producers , as autotrophs are also known, begin food chains which feed all life. Food chains will be discussed in the " Food Chains and Food Webs " concept.
Heterotrophs cannot make their own food, so they must eat or absorb it. For this reason, heterotrophs are also known as consumers. Consumers include all animals and fungi and many protists and bacteria. They may consume autotrophs or other heterotrophs or organic molecules from other organisms. Heterotrophs show great diversity and may appear far more fascinating than producers.
But heterotrophs are limited by our utter dependence on those autotrophs that originally made our food. If plants, algae, and autotrophic bacteria vanished from earth, animals, fungi, and other heterotrophs would soon disappear as well. All life requires a constant input of energy. Only autotrophs can transform that ultimate, solar source into the chemical energy in food that powers life, as shown in Figure below.
Photosynthetic autotrophs, which make food using the energy in sunlight, include a plants, b algae, and c certain bacteria. Photosynthesis provides over 99 percent of the energy for life on earth. A much smaller group of autotrophs - mostly bacteria in dark or low-oxygen environments - produce food using the chemical energy stored in inorganic molecules such as hydrogen sulfide, ammonia, or methane. While photosynthesis transforms light energy to chemical energy, this alternate method of making food transfers chemical energy from inorganic to organic molecules.
It is therefore called chemosynthesis , and is characteristic of the tubeworms shown in Figure below. Some scientists think that chemosynthesis may support life below the surface of Mars, Jupiter's moon, Europa, and other planets as well.
Ecosystems based on chemosynthesis may seem rare and exotic, but they too illustrate the absolute dependence of heterotrophs on autotrophs for food.
A food chain shows how energy and matter flow from producers to consumers. Orcas are a top predator in the ocean, and they can eat sharks as well as fish. An eagle or a hawk are examples of top predators in the bird world. A Crown-of-Thorn sea star is a top predator on a coral reef. Humans are top predators as well. Some heterotrophs are omnivores and eat both primary producers and other heterotrophs like themselves. A re all animals heterotrophs? We can say that all animals are heterotrophs but the type varies depending on what they preferably eat.
Most herbivores only eat plants and other photosynthetic autotrophs and never eat other animals. Some can be both primary consumers or secondary consumers. Think of a bear, for example. Bears can eat fruits and vegetables, but can also eat other animals. Humans are the same. Are humans heterotrophs? Humans are heterotrophs and many of us are omnivores.
We eat a variety of plants and animals. By eating other organisms in the food chain, heterotrophs recycle nutrients and organic chemicals and put them to good use in their body, or defecate and, therefore, help seeds of a variety of plants germinate and spread to other areas of an ecosystem.
Some plant seeds need to pass through the digestive system of a heterotroph, or consumer, to germinate this process is called scarification , and it is the process that weakens the coat of seed so that the plant embryo can emerge. Consumers or predators are very important ecologically because they keep the populations of their prey within reasonable numbers. For example, a review of research studies by Ballard et al. A classic thirty-year study in Isle Royale, Michigan Page clearly showed how predators wolves in this case and prey moose interact.
The size of a wolf pack is determined by how many moose are available in a particular area. If the moose population increases, then the size of the wolf pack can increase and vice-versa. Also, predators tend to eat older and weaker individuals or the ones that are less able to survive and, by doing so, keep the population of their prey healthier.
In many places where predators have been hunted and eliminated, ecosystems are unhealthy. For example, in the United States, deer populations have exploded in many areas because wolves, coyotes, and other natural predators have disappeared. This causes overpopulation, which results in overgrazing i. Too many individuals in a population are more prone to spread diseases as unhealthy individuals are not eliminated by a predator.
What is an example of a heterotroph? And which kind of organism is a heterotroph? All non-autotrophic are heterotrophs. They are exemplified by animals, fungi, various protists, and some bacteria. Therefore, heterotrophs can be multicellular i. We already cited various animals that play a role as heterotrophs in an ecosystem. Refer to the previous section for specific examples of animals as heterotrophs: The Role of Heterotrophs in the Ecosystem. Are fungi autotrophs or heterotrophs?
Fungi are heterotrophic. These organisms are plant-like in having cell walls but they lack chlorophyll green pigment essential in photosynthesis. Protists Kingdom Protista that are heterotrophs include protozoans , certain nonphotosynthetic algae, water molds, and slime molds. There is such a variety of these Protists that entire books have been dedicated to describing them and many existing species have probably not yet been discovered Ref.
Ameoba is just one of them. Watch the video below to see how an amoeba catches and eats its prey, paramecia a ciliate protozoan. Many bacteria are heterotrophs. Examples are Escherichia coli , commonly found in feces, and many bacteria on our skin, in water bodies, and in a variety of other habitats.
An interesting group of bacteria is the microbe-eating microbes. These bacteria eat other bacteria. Below is a video of a bacterium Bdellovibrio that attacks and feeds on another bacterium E. They may be consuming organisms for nutrition but they are still capable of photosynthesis. Thus, we can say that they are facultatively heterotrophic, meaning they are not wholly heterotrophic and may still survive through a photosynthetic mode of life and grow, albeit relatively slower when not resorting to heterotrophy.
Try to answer the quiz below to check what you have learned so far about heterotrophs. Sutton, J. A heterotroph is a living organism that has to consume organic molecules in order to survive. They get these molecules by eating other living things. Herbivores eat plants. Scavengers eat things left behind by carnivores and herbivores. Scavengers can also be omnivores. Decomposers break down dead plant or animal matter into soil. Detritivores eat soil and other very small bits of organic matter.
In order for an organism to be considered alive , it must be able to obtain materials from the environment and use those materials to produce energy in order to carry out cellular functions.
Autotrophs make their own food. They use energy from the sun to make complex organic compounds. They often use photosynthesis to turn sunlight, water , and carbon dioxide into glucose and oxygen.
Heterotrophs obtain their energy by using other organisms as their food source. They use cellular respiration to turn the food they eat into usable energy. Metabolism : Using chemical reactions to harvest energy for biological functions. Did you know that not all heterotrophs are the same? This video explains how these organisms fit into the energy exchange in an ecosystem. You'll also learn how they get energy and nutrients from what they eat, and what the different types of heterotrophs like to eat.
Autotrophs , on the other hand, produce their own energy from sunlight. They make organic substances that the heterotrophs later eat. Basically, if it needs to eat, it's a heterotroph. Explanations 4.
Hannah Bonville.
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