Evolution. Concept for struggle for existence

1.

MEDICAL ACADEMY NAMED AFTER
S.I. GEORGIEVSKY
OF VERNADSKY CFU
EVOLUTION
BY
SIVAKUMAR KALAIVANNANILAVAN
194-B

2.

CONCEPT FOR STRUGGLE FOR EXISTENCE
• The concept of the struggle for existence concerns the competition or battle
for resources needed to live. It can refer to human society, or to organisms in
nature. The concept is ancient, and the term struggle for existence was in use
by the end of the 18th century. From the 17th century onwards the concept
was associated with a population exceeding resources, an issue shown starkly
in Thomas Robert Malthus’ An Essay on the Principle of Population which drew
on Benjamin Franklin's Observations Concerning the Increase of Mankind,
Peopling of Countries, etc

3.

• Charles Darwin used the phrase "struggle for existence" in a broader sense,
and chose the term as the title to the third chapter of On the Origin of
Species published in 1859. Using Malthus’s idea of the struggle for existence,
Darwin was able to develop his view of adaptation, which was highly
influential in the formulation of the theory of natural selection. In addition,
Alfred Wallace independently used the concept of the struggle for existence
to help come to the same theory of evolution. Later, T.H. Huxley further
developed the idea of the struggle for existence.

4.

• Huxley did not fully agree with Darwin on natural selection, but he did agree
that there was a struggle for existence in nature. Huxley also recognized that
a struggle for existence existed between competing ideas within the minds of
people engaged in intellectual discussion.
• This view is an early example of what was later described as meme theory.

5.

• While the idea of the struggle for existence was developing in the western
world, there were other interpretations of the struggle for existence,
especially by Peter Kropotkin in Russia. Also, the struggle for existence was
questioned in the United States in the 1930s, as the idea of cooperation
among organisms became popular. More recently, it has been argued that the
struggle for existence is not as important on macroevolutionary time scales.

6.

FORMS FOR STRUGGLE FOR EXISTENCE
• The struggle for existence leads to the interactions between the organisms
which is called as the competition
Competition is an interaction between organisms or species in which both the
organisms or species are harmed. Limited supply of at least one resource
(such as food, water, and territory) used by both can be a factor.

7.

Competition both within and between species is an important topic in ecology,
especially community ecology. Competition is one of many interacting biotic and
abiotic factors that affect community structure.
There are two types of completion in the nature they are:
• Interspecific competiton
• Intraspecific competition

8.

INTRASPECIFIC COMPETITION
• Intraspecific competition is an interaction in population ecology, whereby
members of the same species compete for limited resources. This leads to a
reduction in fitness for both individuals, but the most fit individual survives and
is able to reproduce. By contrast, interspecific competition occurs when
members of different species compete for a shared resource. Members of the
same species have rather similar requirements for resources, whereas different
species have a smaller contested resource overlap, resulting in intraspecific
competition generally being a stronger force than interspecific competition.

9.

• Individuals can compete for food, water, space, light, mates or any other
resource which is required for survival or reproduction. The resource must be
limited for competition to occur; if every member of the species can obtain a
sufficient amount of every resource then individuals do not compete and the
population grows exponentially. Prolonged exponential growth is rare in
nature because resources are finite and so not every individual in a
population can survive, leading to intraspecific competition for the scarce
resources.

10.

• When resources are limited, an increase in population size reduces the quantity of resources
available for each individual, reducing the per capita fitness in the population. As a result, the
growth rate of a population slows as intraspecific competition becomes more intense, making it
a negatively density dependent process. The falling population growth rate as population
increases can be modelled effectively with the logistic growth model
• Intraspecific competition does not just involve direct interactions between members of the same
species (such as male deer locking horns when competing for mates) but can also include
indirect interactions where an individual depletes a shared resource (such as a grizzly bear
catching a salmon that can then no longer be eaten by bears at different points along a
river).

11.

INTERSPECIFIC COMPETITION
• Interspecific competition, in ecology, is a form of competition in which
individuals of different species compete for the same resources in an
ecosystem (e.g. food or living space). This can be contrasted with mutualism, a
type of symbiosis. Competition between members of the same species is
called intraspecific competition.

12.

Exploitative competition, also referred to as resource competition, is a form of competition in which
one species consumes and either reduces or more efficiently uses a shared limiting resource and
therefore depletes the availability of the resource for the other species. Thus, it is an indirect
interaction because the competing species interact via a shared resource.
Interference competition is a form of competition in which individuals of one species interacts
directly with individuals of another species via antagonistic displays or more aggressive behavior
In a review and synthesis of experimental evidence regarding interspecific competition, Schoener
described six specific types of mechanisms by which competition occurs, including consumptive,
preemptive, overgrowth, chemical, territorial, and encounter. Consumption competition is always
resource competition, but the others are cannot always be regarded as exclusively exploitative or
interference.

13.

• This type of competition can also be observed in forests where large trees
dominate the canopy and thus allow little light to reach smaller competitors
living below. These interactions have important implications for the population
dynamics and distribution of both species.

14.

ELIMINATION
It is also known as Competitive Exclusion or Gauses Law.
Which arose from mathematical analysis and simple competition models states that
two species that use the same limiting resource in the same way in the same space
and time cannot coexist and must diverge from each other over time in order for the
two species to coexist. One species will often exhibit an advantage in resource use.
This superior competitor will out-compete the other with more efficient use of the
limiting resource. As a result, the inferior competitor will suffer a decline in population
over time. It will be excluded from the area and replaced by the superior competitor

15.

GENERAL ELIMINATION
• Although local extinction of one or more competitors has been less
documented than niche separation or competitive exclusion, it does occur. In an
experiment involving zooplankton in artificial rock pools, local extinction rates
were significantly higher in areas of interspecific competition. In these cases,
therefore, the negative effects are not only at the population level but also
species richness of communities.

16.

IMPACT ON COMMUNITIES
• As mentioned previously, interspecific competition has great impact on community composition
and structure. Niche separation of species, local extinction and competitive exclusion are only
some of the possible effects. In addition to these, interspecific competition can be the source of
a cascade of effects that build on each other. An example of such an effect is the introduction
of an invasive species to the United States, purple-loosestrife. This plant when introduced to
wetland communities often outcompetes much of the native flora and decreases species
richness, food and shelter to many other species at higher trophic levels. In this way, one
species can influence the populations of many other species as well as through a myriad of
other interactions. Because of the complicated web of interactions that make up every
ecosystem and habitat, the results of interspecific competition are complex and site-specific.

17.

Understanding functional diversity and redundancy, and the roles each play in conservation efforts is
often hard to accomplish because the tools with which we measure diversity and redundancy cannot be
used interchangeably. Due to this, recent empirical work most often analyzes the effects of either
functional diversity or functional redundancy, but not both. This does not create a complete picture of the
factors influencing ecosystem production. In ecosystems with similar and diverse vegetation, functional
diversity is more important for overall ecosystem stability and productivity. Yet, in contrast, functional
diversity of native bee species in highly managed landscapes provided evidence for higher functional
redundancy leading to higher fruit production, something humans rely heavily on for food consumption.
A recent paper has stated that until a more accurate measuring technique is universally used, it is too
early to determine which species, or functional groups, are most vulnerable and susceptible to extinction.
Overall, understanding how extinction affects ecosystems, and which traits are most vulnerable can
protect ecosystems as a whole

18.

KEY SPECIES
A functional group is merely a set of species, or collection of organisms, that share
alike characteristics within a community. Ideally, the lifeforms would perform
equivalent tasks based on domain forces, rather than a common ancestor or
evolutionary relationship. This could potentially lead to analogous structures that
overrule the possibility of homology. More specifically, these beings produce
resembling effects to external factors of an inhabiting system. Due to the fact that a
majority of these creatures share an ecological niche, it is practical to assume they
require similar structures in order to achieve the greatest amount of fitness. This
refers to such as the ability to successfully reproduce to create offspring, and
furthermore sustain life by avoiding alike predators and sharing meals.

19.

INTENSITY OF ELIMINAITON
• Functional redundancy refers to the phenomenon that species in the same
ecosystem fill similar roles, which results in a sort of "insurance" in the
ecosystem. Redundant species can easily do the job of a similar species from
the same functional niche. This is possible because similar species have
adapted to fill the same niche overtime. Functional redundancy varies across
ecosystems and can vary from year to year depending on multiple factors
including habitat availability, overall species diversity, competition among
species for resources, and anthropogenic influence.

20.

This variation can lead to a fluctuation in overall ecosystem production. It is not
always known how many species occupy a functional niche, and how much, if any,
redundancy is occurring in each niche in an ecosystem. It is hypothesized that each
important functional niche is filled by multiple species. Similar to functional diversity,
there is no one clear method for calculating functional redundancy accurately, which
can be problematic. One method is to account for the number of species occupying a
functional niche, as well as the abundance of each species. This can indicate how
many total individuals in an ecosystem are performing one function.

21.

EFFECTS ON CONSERVATION
• Studies relating to functional diversity and redundancy occur in a large proportion of
conservation and ecological research. As the human population increases, the need for
ecosystem function subsequently increases. In addition, habitat destruction and modification
continue to increase, and suitable habitat for many species continues to decrease, this research
becomes more important. As the human population continues to expand, and urbanization is
on the rise, native and natural landscapes are disappearing, being replaced with modified
and managed land for human consumption. Alterations to landscapes are often accompanied
with negative side effects including fragmentation, species losses, and nutrient runoff, which
can effect the stability of an ecosystem, productivity of an ecosystem, and the functional
diversity and functional redundancy by decreasing species diversity.

22.

It has been shown that intense land use affects both the species diversity, and
functional overlap, leaving the ecosystem and organisms in it vulnerable. Specifically,
bee species, which we rely on for pollination services, have both lower functional
diversity and species diversity in managed landscapes when compared to natural
habitats, indicating that anthropogenic change can be detrimental for organismal
functional diversity, and therefore overall ecosystem functional diversity. Additional
research demonstrated that the functional redundancy of herbaceous insects in
streams varies due to stream velocity, demonstrating that environmental factors can
alter functional overlap.

23.

When conservation efforts begin, it is still up for debate whether preserving specific
species, or functional traits is a more beneficial approach for the preservation of
ecosystem function. Higher species, diversity can lead to an increase in overall
ecosystem productivity, but does not necessarily insure the security of functional
overlap. In ecosystems with high redundancy, losing a species (which lowers overall
functional diversity) will not always lower overall ecosystem function due to high
functional overlap, and thus in this instance it is most important to conserve a group,
rather than an individual. In ecosystems with dominant species, which contribute to a
majority of the biomass output, it may be more beneficial to conserve this single
species, rather than a functional group.