Download 1- Autotrophs

Ecology\ Third stage
Lec. 2
Department of biology
Dr. Kawther M. Ali
Biotic Components
It comprises the living part of the environment, which includes the
association of a number of interrelated populations belonging to different
species inhabiting a common environment. The populations are those of
animal community, plant community and microbial community.
Biotic community is distinguished into autotrophs, heterotrophs and
saprotrophs.
1- Autotrophs (Greek: auto - self, trophos - feeder) are also called
producers, convertors or transducers. These are photosynthetic plants,
generally chlorophyll bearing, which synthesize high-energy complex
organic compounds (or food) from the inorganic raw materials with the
help of sunlight, and this process is referred as photosynthesis.
Autortophs form the core of all biotic system.
In terrestrial ecosystems, the autotrophs are mainly the rooted plants.
In aquatic ecosystems, the floating plants called phytoplankton and the
shallow water rooted plants called macrophytes are the dominant
producers.
Ecology\ Third stage
Lec. 2
Department of biology
Dr. Kawther M. Ali
2- Heterotrophs (Greek: heteros - other; trophs - feeder) are called
consumers, which are generally animals feeding on other organisms.
Consumer's also referred as phagotrophs (phago - to ingest or swallow) or
macroconsumers are mainly herbivores and carnivores and other group is
called omnivores.
- Herbivores are referred to first order consumers or primary
consumers, they feed directly on green plants. For example,
Terrestrial ecosystem consumers like cattle, deer, rabbit, grass
hopper, etc. While Aquatic ecosystem consumers like protozoans,
crustaceans, etc.
- Carnivores are animals which called primary carnivores or second
order consumers, they feed or prey upon other animals
(herbivorous animals). For example, fox, frog, predatory birds,
smaller fishes, snakes, etc.
Secondary carnivores or third order consumers include the animals,
which feed on the primary carnivores. For example, wolf, peacock, owl,
etc.
Some larger carnivores preyed on secondary carnivores. Which are called
Tertiary carnivores or Quaternary consumers include the animals, which
feed on the secondary carnivores. For example , lion, tiger, etc. These are
not eaten by any other animals. The larger carnivores, which cannot be
preyed upon further are called top carnivores.
Ecology\ Third stage
Lec. 2
Department of biology
Dr. Kawther M. Ali
3- Saprotrophs (Greek: sapros - rotten; trophos - feeder) are also called
decomposers or reducers for example, fungi and bacteria. They break
down the complex organic compounds in dead matter (plants and
animals) into simpler form which can be reused. Decomposers do not
ingest their food. Instead they secrete digestive enzymes into the dead,
decaying plant and animal remains to digest the organic material.
Enzymes act on the complex organic compounds in the dead matter.
Decomposers absorb a part of the decomposition products to provide
themselves with nourishment. The remaining substances are added as
minerals in the process of mineralisation to the substratum (soil).
Released minerals are reused or utilised as nutrients by the plants
(producers).
All species are influenced by biotic factors in one way or another. For
example, If the number of predators will increase, the whole food web
Ecology\ Third stage
Lec. 2
Department of biology
Dr. Kawther M. Ali
will be affected (the population number of organisms that are lower in the
food web will decrease). Similarly, when organisms have more food to
eat, they will grow quicker and will be more likely to reproduce, so the
population size will obviously increase. Pathogens and disease outbreaks,
however, are most likely to cause a decrease in population size. Humans
make the most sudden changes in an environment (e.g. building cities and
factories, disposing of waste into the water). These changes are most
likely to cause a decrease in the population of any species, due to the
sudden appearance of pollutants.