Lecture 8 Insect ecology and balance of life
Ecology:
The term ecology is derived from the Greek term “oikos” meaning “house”
combined with “logy” meaning “the science of” or “the study of”. Thus literally
ecology is the study of earth’s household comprising of the plants, animals,
microorganisms and people that live together as interdependent components. The term
ecology was coined by a German biologist Ernst Haekel (1869).
Definition of Ecology
Ecology can be defined as the science of plants and animals in relation to their
environment.
Webster’s dictionary defines ecology as “totality of pattern of relation between
organisms and their environment.”
Eugene P. Odum defined ecology as “the study of organisms at home”
Insect Ecology may be defined as the understanding of physiology and
behaviour of insects as affected by their environment.
Ecology related terminology
i. Habitat is the place where the organism lives.
ii. Population denotes groups of individuals of any kind of organism. Insect
populations are groups of individuals set in a frame that is limited in time and
space.
iii. Community in the ecological sense includes all the populations of a given
area. Community can also be defined as interacting ‘web’ of populations
where individuals in a population feed upon and in turn are fed upon by
individuals of other populations (Fig. 1)
iv. Ecosystem
Ecosystem or ecological system is the functioning together of community and
the nonliving environment where continuous exchange of matter and energy
takes place.
In other words ecosystem is the assemblage of elements, communities and
physical environment.
Ecosystem is the ultimate unit for study in ecology as they are composed of
living organisms and the nonliving environment.
, Examples of natural ecosystem: Ponds, lakes and forests ecosystem (Fig.2)
v. Biosphere is the term used for all of the earth’s ecosystems functioning
together on the global scale.
Living Genes Cells Organs Organisms Populations Communities
components
+
Nonliving
components Matter Energy
Biosphere
= Biosystems
Gene Cell Organ Organism Population Ecosystem
System system system system system system
Figure 3. Flow of matter and energy in an ecosystem
Agroecosystem is largely created and maintained to satisfy human wants or
needs. It is not a natural ecosystem but is man made. Agroecosystem is the basic unit
of pest management - a branch of applied ecology.
A typical agroecosysyetm (Fig. 4) is composed of
i. more or less uniform crop-plant population
ii. weed communities
iii. animal communities (including insects)
iv. microbiotic communities
v. and the physical environment the react with.
Unique features of Agroecosystem
Dominated by plants selected by man
No species diversity and no intraspecific diversity. Genetically uniform
Phenological events like germination, flowering occur simultaneously
Lack of temporal continuity - due to various agricultural operations carried out
by man like ploughing, weeding, pesticide application etc.
Plants contain imported genetic material
Nutrients are added
Outbreak of pests, weeds and diseases occur frequently
Ecology:
The term ecology is derived from the Greek term “oikos” meaning “house”
combined with “logy” meaning “the science of” or “the study of”. Thus literally
ecology is the study of earth’s household comprising of the plants, animals,
microorganisms and people that live together as interdependent components. The term
ecology was coined by a German biologist Ernst Haekel (1869).
Definition of Ecology
Ecology can be defined as the science of plants and animals in relation to their
environment.
Webster’s dictionary defines ecology as “totality of pattern of relation between
organisms and their environment.”
Eugene P. Odum defined ecology as “the study of organisms at home”
Insect Ecology may be defined as the understanding of physiology and
behaviour of insects as affected by their environment.
Ecology related terminology
i. Habitat is the place where the organism lives.
ii. Population denotes groups of individuals of any kind of organism. Insect
populations are groups of individuals set in a frame that is limited in time and
space.
iii. Community in the ecological sense includes all the populations of a given
area. Community can also be defined as interacting ‘web’ of populations
where individuals in a population feed upon and in turn are fed upon by
individuals of other populations (Fig. 1)
iv. Ecosystem
Ecosystem or ecological system is the functioning together of community and
the nonliving environment where continuous exchange of matter and energy
takes place.
In other words ecosystem is the assemblage of elements, communities and
physical environment.
Ecosystem is the ultimate unit for study in ecology as they are composed of
living organisms and the nonliving environment.
, Examples of natural ecosystem: Ponds, lakes and forests ecosystem (Fig.2)
v. Biosphere is the term used for all of the earth’s ecosystems functioning
together on the global scale.
Living Genes Cells Organs Organisms Populations Communities
components
+
Nonliving
components Matter Energy
Biosphere
= Biosystems
Gene Cell Organ Organism Population Ecosystem
System system system system system system
Figure 3. Flow of matter and energy in an ecosystem
Agroecosystem is largely created and maintained to satisfy human wants or
needs. It is not a natural ecosystem but is man made. Agroecosystem is the basic unit
of pest management - a branch of applied ecology.
A typical agroecosysyetm (Fig. 4) is composed of
i. more or less uniform crop-plant population
ii. weed communities
iii. animal communities (including insects)
iv. microbiotic communities
v. and the physical environment the react with.
Unique features of Agroecosystem
Dominated by plants selected by man
No species diversity and no intraspecific diversity. Genetically uniform
Phenological events like germination, flowering occur simultaneously
Lack of temporal continuity - due to various agricultural operations carried out
by man like ploughing, weeding, pesticide application etc.
Plants contain imported genetic material
Nutrients are added
Outbreak of pests, weeds and diseases occur frequently
