Medical Academy named after S.I. Georgivsky

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REPRESENTED BY:
DHRUV MANGAL
195 B
SUPERVISOR:
ANNA ZHUKOVA

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The fauna and f lora of estuaries are typically capable of
tolerating the above- mentioned changes. A comparison of an
estuarine f lora and fauna with that of a neighboring marine
reef will show that there are many species, both plant and
animal, which are either excluded by these changing
conditions or avoid estuaries. Those that can tolerate the
estuarine environment are often very successful and
abundant in their chosen environment, e.g. sand prawns
Callianassa kraussi and mudprawns Upogebia africana,
mullet and fish that feed on the bottom or eat plankton.

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a) Microbes in Buccal Cavity: The population of the
microorganisms present in the buccalcavity
(or oral cavity) distinctly differs from that of the
gastrointestinal tract (GIT).(
b) Marine Microorganisms: Invariably the microorganisms
located specifically in the marineenvironments
differ predominantly from those found in the fresh
water and terrestrial environments.(
c) Distribution in Nature: Quite often one may observe
that certain microorganisms are abundantlyand widely
distributed in nature, whereas others, may be significantly
restricted to a
specific environment.

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Population Size is represented by the letter N, and it equals
the total number of individuals in a population. The larger a
population is, the greater its generic variation and therefore
its potential for long-term survival. Increased population size
can, however, lead to other issues, such as overuse of
resources leading to a population crash.
Population Density refers to the number of individuals in a
particular area. A low-density area would have more
organisms spread out. High-density areas would have more
individuals living closer together, leading to greater resource
competition.

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Population Dispersion: Yields helpful information about how
species interact with each other. Researchers can learn more about
populations by studying they way they are distributed or dispersed.
Population distribution describes how individuals of a species are
spread out, whether they live in close proximity to each other or far
apart, or clustered into groups.
Uniform dispersion refers to organisms that live in a specific
territory. One example would be penguins. Penguins live in
territories, and within those territories the birds space themselves
out relatively uniformly.
Random dispersion refers to the spread of individuals such as winddispersed seeds, which fall randomly after traveling.
Clustered or clumped dispersion refers to a straight drop of seeds to
the ground, rather than being carried, or to groups of animals living
together, such as herds or schools. Schools of fish exhibit this
manner of dispersion.

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Quadrat method: Ideally, population size could be determined by
counting every individual in a habitat. This is highly impractical in
many cases, if not impossible, so ecologists often have to Mark
and recapture: Obviously a quadrat would not work for animals
that move a round a great deal. So to determine the population
size of more mobile organisms, scientists use a method
called mark and recapture.extrapolate such information.

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population growth ref lects the change in the number of
individuals over a period of time. Population growth rate is
affected by birth and death rates, which in turn are related to
resources in their environment or outside factors such as
climate and disasters. Decreased resources will lead to a
decreased population growth. Logistic growth refers to
population growth when resources are limited.

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There are five main characteristics of a population and
these include population size, population density,
population distribution, age structure and reproductive
base. These characteristics of a population can be found in
population ecology, which is a combination of the study of
how organisms interact with each other and their
environment focusing on the group of individuals of the
same species, most often humans in population ecology, who
live in a given area.
The population size is the number of individuals in the gene
pool. The population density is the number of individuals
living in a given area. The population distribution is the
pattern of distribution.

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Two major themes govern the growth of populations over time:
1. The resources of an environment control the growth and continued existence of
populations
2. The resources of an environment are limited
Few populations can live up to their biotic potential = where conditions are
ideal, every member has food, shelter, no predators or pathogens in the
environment, maximum reproduction
Limiting factors in the environment: limits on food, water, minerals, predators,
shelter, buildup of waste materials usually prevent organisms from reaching their
biotic potential
Carrying capacity: maximum number of individuals an environment's resources
can sustain
Typically, after a period of exponential growth, growth levels off or even stops
when the carrying capacity is reached

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Competition between species for food may serve as a densitydependent limiting factor when at least one of two
populations reaches a density where the two populations
combined overwhelm the food supply. For example, when
rainbow smelt were introduced into Lake Winnipeg, they put
a strain on the f lourishing population of emerald shiners
because both species eat the same food. This competition
likely explains the resulting decrease in emerald shiners.
Also, competition isn't limited to animals. Eurasian water
milfoil is a freshwater aquatic plant that grows and spreads
rapidly in ponds and lakes. It can use up much of the
dissolved oxygen that other plants and fish need to survive.