Competition occurs between organisms of the same or different species when they require limited shared resources like food, water, space, or nutrients. This can result in reduced growth, reproduction, and survival as the resources become more scarce. There are two main types of competition: intraspecific competition between individuals of the same species, and interspecific competition between different species. Long-term competition can lead to niche differentiation, character displacement, or even the extinction of one species if it is outcompeted for resources.

1. Competition

2. • Interaction that occurs between two or more
organisms when the resources necessary for
them are limited and adversely affect them.
• Usually occurs when resources ( space, light,
nutrients, food and water) are limited.
• Results in growth and seed production of
species reduced

3. Competition occurs not only among individuals
of a given species but also between members of
two or more species.
Populations may compete directly leading to the
extinction or adaptation of one of them.
Many animals establish territories within which
they live and which they will defend against
other of their species that try to intrude.

4. Competition is of two types:-
– Intraspecific competition
– Interspecific competition

6. • Intraspecific competition:
– Competition between individuals of the same
species
– Very severe as all the members of a species have
similar requirements
– Individuals of the same species have similar
adaptations

8. • Interspecific competition:-
– Competition between individuals of different
species.
– May be very severe if animals of different species
depend on one or more of the same necessities.

9. *Studies show that intraspecific competition can regulate
population dynamics. This occurs because individuals become
crowded as a population grows. Since individuals within a
population require the same resources, crowding causes
resources to be more limited. Some individuals eventually do
not acquire enough resources and die or do not reproduce.
This reduces population size and slows population growth.
Species also interact with other species that require the same
resources. Consequently interspecific competition can alter
the sizes of many species’ populations at the same time.
Experiments demonstrate that when species compete for a
limited resource, one species eventually drives the population
of other species extinct because the best competitor will
exude all other competing species.

12. Gause’s Principle
This principle was put forward by Gause in 1934. It states that two species having
similar requirements cannot live at the same place permanently. When two
species of Paramecium (P. caudatum and P. aurelia) are kept together, one is
eliminated. This phenomenon was called ‘principle of competitive exclusion’ by
Hardin
Eg., two finch species, Geospiza fuliginosa and Geospiza fortis, vary in a
key trait: beak size, which determines the size of a seed that a finch can eat:
Individuals with small beaks eat small seeds, individuals with intermediate sized
beaks can eat intermediate size seeds and individuals with large beaks can eat
large seeds. G. fuliginosa and G. fortis do compete for intermediate sized seeds
because each species has some individuals with intermediate sized beaks.
However, G. fuliginosa specializes upon smaller seeds because it has more
individuals with small beaks. Conversely, G. fortis specializes upon larger seeds
because it has more individuals with large beaks. Thus, these species niches differ
slightly because a specific trait, beak size, allows them to specialize upon a
particular seed size

13. Special adaptations may allow the competing
species to coexist in the same area. Fourteen
species of Darwin’s finches live together in the
Galapagos Islands because of different feeding
habits. Many plant species grow together
different levels for absorbing water and
minerals.

14. • Competition is a (+-) negative interaction that
occurs among organisms whenever two or more
organisms require the same limited resource. All
organisms require resources to grow, reproduce
and survive.
– Eg., animals require food and water whereas plants
require soil nutrients, light and water
• Organisms, however, cannot acquire a resource
when other organisms consume or defend that
resource. Therefore, competitors reduce each
other’s growth, reproduction and/or survival

16. Interference and Exploitation
Biologists typically recognize two types of competition:
Interference and exploitative competition.
During interference competition, organisms interact
directly by fighting for scarce resources.
– Eg., large aphids feeding sites on cottonwood leaves by
kicking and shoving smaller aphids from better sites.
In contrast, during exploitative competition, organisms
interact indirectly by consuming scare resources.
– Eg., plants consume nitrogen by absorbing it into their
roots, making nitrogen unavailable to nearby plants.

17. Character Displacement
Competition cause species to evolve differences in traits. This occurs as
individuals of a species with traits similar to competing species always
experience strong interspecific competition. These individuals have
less reproduction and survival than individuals with traits that differ
from their competitors. Consequently, they will not contribute many
offsprings to future generations. Eg., finches of the Galapagos Islands
can be found alone or together on the islands. Both species
populations actually have more individuals with intermediate sized
beaks when they live on islands without the other species present.
However, when both species are present on the same island,
competition is intense between individuals that have intermediate size
beaks of both species because they all require intermediate sized
seeds. Consequently, individuals with small and large beaks have
greater survival and reproduction on these islands than individuals
with intermediate sized beaks.

18. The End