Biotic factors also regulate the size of populations more intensely. Finally, the influence of biotic interactions can occur at two different levels. Interspecific effects are direct interactions between species, and the intraspecific effects represent interactions of individuals within a single species.

1. JUNIOR

2.  Biological/biotic interactions : effects of one
organism on other organism in a community.
 No organism exists in absolute isolation
 An organism's interactions with its environment are
fundamental to the survival of that organism and
the functioning of the ecosystem as a whole.
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3. Biotic interactions
Interaspecific
interaction
Between individuals of same
spp
Interspecific
interactions
Between individual of different spp
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4.  De Bary (1879): used term symbiosis to
describe interactions among organisms.
Most ecologists include all types of
interactions including parasitism under
symbiosis.
 Clarke (1954) used the term symbiosis for
interactions which are mutually beneficial
and neither is harmed
 McDougall (1918): Grouped all (beneficial
& harmful) interactions under symbiosis.
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5. SYMBIOSIS
DISJUNCTIVE SYMBIOSIS
(where associated organisms are
not in constant contact)
SOCIAL
(no direct
relationshi
p)
NUTRITIVE
(food relationship)
ANTAGONIST
IC
RECIPROC
AL
CONJUNCTIVE SYMBIOSIS
(where dissimilar organisms live in contact with
each other)
SOCIAL
(no direct
relationship)
Lianas,
epihpytes
NUTRITIVE
(No direct relationship)
ANTAGONISTIC
parasites
RECIPROCAL
Lichens,
mycorrhizae,nitro
gen fixing
organisms
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6. Epiphytes Lianas
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7. Parasites
Antagonistic nutritive conjunctive symbiosis
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8. Lichen Mycorrhizea
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9.  Haskell & Burkholder (1952): used 3 symbols
and their possible combinations to describe
interactions among organisms
0 No significant interaction
+ Growth, survival & other population
attributes are benefited
-
Growth, survival & other population
attributes are inhibited
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10. COMBINATIONS INTERACTION TYPE DETAILED EFFECT
0 0 Neutralism
Neither population
affect the other.
_ _
Competition
(Direct interference type)
Direct inhibition of
each spp by the other.
_ _
Competition
(Resource use type)
Indirect inhibition
where common
resources are in short
supply.
- 0 Amensalism
One population is
inhibited, other is not
affected.
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11. COMBINATIONS INTERACTION TYPE DETAILED EFFECT
+ +
Protocooperation
Interaction favorable to
both but not obligatory.
+ +
Mutualism
Interaction favorable to
both and obligatory.
+ 0
Commensalism
One population
(commensal) benefits
while other population
(host)is not affected.
+ -
Parasitism
One is benefited other is
harmed, parasite smaller
than the host
+ -
predation
One is benefited other is
harmed, the predator is
generally larger then the
host.
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12. Odum, (1971): Grouped all types of symbiotic
interactions into two major groups:
1) Positive interactions
2) Negative interactions
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13. Populations help one another in terms of food,
shelter, substratum or transport. Either one or
both the spp are benefitted.
a. Commensalism
b. Mutualism
c. Protocooperation
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14.  It is Interspecific interaction between
members of different spp where one
organism is benefitted but the other is
neutral (there is no harm or benefit).Two or
more population live together without
entering into any kind of physiological
exchange.
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15. Use other plant for support &
not for food or water supply.
Not rooted in soil
Velamen layer over root surface
which take up water rapidly from
atmosphere.
Eg: Orchids, hanging mosses.
Vascular plants rooted in ground.
Maintain erectness of stem by
using tree for support.
No direct nutritional relationship
with tree.
Eg: Bauhinia, Ficus, Tinospora
LIANASEPIPHYTES
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16. It is an Interspecific interaction where both
individuals derive benefit. There is, permanent
& obligatory contact between the two species
i.e. (the association is essential for survival of
both the species).
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17. Examples
i) Pollination by animals: bees, Moths, butterflies
take food from nectar or other plant product and in
turn help the plant in its pollination.
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18. ii) Lichens
Association between algae and fungi. Body of lichens
is made of matrix formed by a fungus within which
alga is embedded. The fungus provides moisture and
minerals and the alga manufacture food. Neither of
the two can grow alone/ independently
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19. JUNIOR

20.  Iv) Symbiotic nitrogen fixers
The bacterium Rhizobium forms nodules in
the roots of leguminous plants and lives
symbiotically with the host. Bacteria obtain
food from the higher plants and in turn fix
gaseous nitrogen making it available to the
plants
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21. v) Mycorrhizae: (fungus in association with
the roots of higher plants).
Plant roots provide the fungus with nutrition
and the plant in turn is benefited by the high
absorption capacity of the mycelium for water
and minerals because of large surface area of
mycelium.
e.g.
Roots of pines, oaks,
beech, orchids etc.
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22.  Coral reefs
 These are the result of
mutualisms between
coral organisms and
various types of algae
that live inside them.
 Most land plants and
land ecosystems rely on
mutualisms between the
plants, which fix CO2
from the air
JUNIOR

23. Mutualism among animals
Termites & protozoan are the oldest example
of Mutualism among animals
Termites feed on wood but can’t digest
cellulose. Protozoan (Trichonympha species)
is present in their gut helps in cellulose
digestion & it obtains food & shelter in return
from termite.
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24.  Also called Non obligatory mutualism.
 Both populations are benefited & are not
obligatory (association is not essential for
survival of either population).
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25.  Sea anemone attached
to the shell of hermit
crab.
 Crab carry sea
anemone to fresh
feeding sites.
 Sea anemone protects
the crab from its
enemies.
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26. Clownfish and sea
anemone
•clownfish feeds on small
invertebrates which harm the
sea anemone. The faecal
matter from the clownfish
provides nutrients to the sea
anemone.
•The stinging cells of sea
anemone's in turn protect the
clown fish from predators
The clownfish is immune to
the stinging cells.
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27.  One or both spp are harmed in any way
during their life period.
1. Exploitation
a. Parasitism
b. Predation
2. Amensalism
a.Antibiosis
b. Allelopathy
3. Competition
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28. One spp harms the other by making its direct or indirect
use for support, shelter or food.
e.g.
 SHELTER:
◦ Parasitic birds e.g. cuckoo & cowbird never build their
own nest. Female lays eggs in the nest established by
birds of another spp (usually smaller spp)
 FOOD: The relationships
w.r.t. food can be
◦ Parasitism
◦ Predation
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29.  Relationship where one
organism is benefited and the
other is harmed, a parasite
lives in/on the body of its host
it drives its food from the host
without killing it.
e.g. parasitic vascular plants:
Cuscuta (total stem parasite)
grow on other plants for
nutrition with the help of
adventitious roots (haustoria)
which penetrate the stem of the
host plant Parasitic vascular plants
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30. JUNIOR

31. Viscum album Loranthus spp
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32. Santalum album
(Partial root parasite)
Orobranche spp
(total root parasite)
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33. Animal parasites: can be
Endoparasite (live within the host's body)
Ectoparasite (live on its surface)
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34.  The larval stages of a parasitoid feed
within the host body and adults are
free living.
 e.g.: Braconid wasps & tomato
hornworms
Insect larvae (parasitoids) eat the
host’s (insect) tissue which die.
Parasitoids are used in biological
control. JUNIOR

35. JUNIOR

36.  Predator is free living organism which catches &
kills another spp for food.
e.g. A larger (stronger) animal eating smaller
animals.
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37.  Browsing & grazing:
herbivores killing plants ,
shrubs for food
 Seed & seedling destruction:
mice, squirrel, rodents use
large amount of seeds as
food
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38.  Carnivorous plants/ Insectivorous plants
consumes insect & other small organisms as
their food by using proteolytic enzyme for
digestion of insects
◦ Nepenthes
◦ Drocera
◦ Utricularia
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39. Utricularia
Napenthes
Drocera
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40. JUNIOR

41.  It is an interaction where one species is affected
and the other interacting species experiences no
effect. One organism exudes a chemical
substance that is detrimental to another
organism.
 a. Antibiosis
 b. Allelopathy
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42.  Complete/ partial inhibition / death of one
organism by other by production of toxic
substance (antibiotics) or environmental
conditions as a result of a metabolic pathway.
It is common among microbes. No organism
derive any benefit.
 Eg: Penicillium secrete penicillin, a chemical
that kills bacteria
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43.  Pond blooms of blue
green algae
(Microcystis sp.)
produce a toxin
Hydroxylamine which
causes death of fish
& cattles.
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44.  It is form of Amensalism in plants in which chemical
substances (allelochemicals) produced by one
species inhibit the growth of another.
e.g. Black walnut secretes a chemical (juglone) from
its roots that harms/kills some species of
neighbouring plants of walnut.
Grevillea: produce soluble substance from its roots
that inhibits the establishment of adjacent seedlings
of the same species.
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45.  Interaction between organism or species, in which the
fitness of one is lowered by the presence of
another.They compete for limited supply of resources
(such as food, water, and territory) which are required
for both species.
 Types of resources competed:
a. Raw material
◦ Autotrophs- light, inorganic nutrient
& water
◦ Heterotrophs- organic food & water
b. Space- to grow, nest, hide from
predators
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46. Competition
Interaspecific
competition
Among members of the
same species
Interspecific
competition
Between individuals of
different species
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47. It is found between the members of the same
species when they compete for the same
resources in an ecosystem.
e.g. trees growing close together compete for
light above ground and water and nutrients
in the soil.
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48. It is found in individuals of two separate species
sharing a limiting resource in the same area.
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49.  Most common type of Interspecific interaction
between two species which do not affect each
other.
e.g. Bactrian Camel and a Longtailed Tadpole
Shrimp, both living in the Gobi desert
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50. As large grazers (animals) move through
the grass, they eat up insects. Cattle
Egrets follow them for insects. The large
grazers are neither helped nor harmed by
the presence of the birds.
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51. JUNIOR