Download 13/SCI03/001

AKUBOH OLIVIA
13/SCI03/001
BCH 413
Explain the following terms:
1. Autotrophs: Autotrophs are self-feeders, and they get their energy from non-living
sources such as the sun and carbon dioxide. Autotrophs can provide energy sources for
themselves as well as for other living organisms that can't produce it on their own.
Autotrophs are called producers because they provide energy and food sources for all
heterotrophic organisms.
There are two types of autotrophs: photoautotrophs and chemoautotrophs. Photoautotrophs get
their energy from sunlight and convert it into usable energy (sugar). This process is called
photosynthesis. During the process of photosynthesis, not only is sunlight turned into energy, but
carbon dioxide is taken from the air and oxygen is released in its place. Chemoautotrophs get
their energy from chemicals, mainly inorganic substances such as hydrogen sulfide and
ammonia. Inorganic substances are those that are not from biological sources, and they do not
contain carbon as a main element. Chemoautotrophs are able to survive in very harsh
environmental conditions because the only source of carbon they need is carbon dioxide.
The only known autotrophs are plants and some types of algae. Most plants are autotrophs, but
all autotrophic plants are photoautotrophs. Plants have structures called chloroplasts that allow
them to capture the sunlight used for photosynthesis. Plants also get nutrition from water, various
minerals in the soil, such as nitrogen and phosphorous, and carbon dioxide in the air.
2. Saprotrophs: they are also called saprophytes, saprobes, or detritivores. They are
organisms that feed on non-living organic matter known as detritus. Saprotrophic
organisms are considered critical to decomposition and nutrient cycling and include
fungi, certain bacteria, and fungus-like organisms known as water molds. Saprotrophs
interact with their environment at the microscopic level. They feed by a process known as
absorptive nutrition, in which the nutritional substrate (e.g., dead organism or other
nonliving organic matter) is directly digested by a variety of enzymes that are excreted by
the saprotroph. The enzymes convert the detritus into simpler molecules, which are then
absorbed by the cells to feed the organism.
Fungi are among the most efficient at decomposing complex organic molecules and recycling
those nutrients back into the ecosystem. Fungi are some of the most-significant decomposers of
plant matter, which makes up the vast majority of detritus in terrestrial environments.
3. Heterotrophs: these are also called 'other feeders,' and because they need to consume
energy to sustain themselves, they are also known as 'consumers.'
A few plants are actually heterotrophic. The European mistletoe is a parasitic plant, surviving off
of a host plant. Other plants, such as pitcher plants, are carnivorous and feed on other organisms
like insects. Other examples of heterotrophs are man, dog, cat, bird, fish, etc. because they all
depend on other organisms as an energy source. Bacteria are also heterotrophs, as well as fungi.
Fungi break down dead and decaying organisms; they serve an important role in helping to
recycle plant and animal material that is no longer living and return those nutrients to the
ecosystem.