ORGANISMS AND POPULATIONS
·
Ecology deals with relations among different
organisms and their terrain.
·
Organisms get acclimated to their terrain for
their survival and reduplication.
·
The gyration of the earth about its axis brings
about changes in the terrain, leading to different seasons. This leads to the
conformation of colorful biomes similar as desert, grassland, etc.
·
Life not only exists in favourable territories,
but also in harsh and extreme conditions.
The environment of an organism can be divided into
1. 1) Abiotic factors
2. 2) Biotic factors
Abiotic
Factors
● Some of the major abiotic factors that
interact with the organisms are
Temperature − It's
the most applicable abiotic factor since all organisms bear an optimum
temperature for their metabolism and other body functions. Depending upon their
capability to tolerate temperature range, organisms are of two
typesstenothermal ( confined to a narrow range of temperature) and eurythermal
(can tolerate a wide range of temperature).
Water − Water also is a major impacting factor. Life on earth
is insolvable without water as it forms the major element of all living cells.
In abysses where volume of water isn't a limitation, the quality of water
becomes bone. Depending upon the capability to tolerate saltness, organisms can
be stenohaline ( confined to narrow range of saltness) and euryhaline (
tolerant to wider range of saltness).
Soil − The
nature and composition of soil differs from one place to another depending upon
the climate, riding process, and soil development system. The characteristic
features similar as soil composition, grain size, percolation, water holding
capacity, etc. determine the native of the organisms it can support.
Light − The
major source of light on earth is the Sun. Light is essential for plants to
perform photosynthesis. Certain plants come acclimated to perform
photosynthesis under veritably low light since they're constantly overshadowed
by altitudinous trees. Numerous plants also depend on light for their flowering
(photoperiodism). The vacuity of light on land is comparatively advanced than
that in water.
Responses to Abiotic Factors
All organisms in order to sustain outside
functionality maintain a constant internal terrain (homeostasis). An organism
may borrow one of the following strategies for homeostasis
Regulate− Certain creatures have the capability to maintain a
constant temperature and a constant osmolarity to keep up their homeostasis.
Mammals have a constant body temperature (37 °C) irrespective of the outside
temperature. In summers, to maintain the temperature, we sweat and in layoffs
we shiver, which produces heat.
Conform − Creatures
and plants except mammals don't have a constant body temperature and their body
temperature changes in agreement with the outside temperature. Similar
organisms are called conformers. Conformers haven't evolved. They've come
controllers since regulation is stoutly more precious.
Migrate − The organism can move
temporarily from stressful territories to further sociable areas and return
once the period changes. Birds can resettle from cold regions to fairly warmer
regions during winter and vice¬versa during summers.
Suspend − Some organisms cease
to be metabolically active during stressful period. They suspend all exertion
and enter a period of dormancy. For example − Spores in bacteria and lower plants
: and hibernation ( winter sleep) and aestivation (summer sleep) in creatures
Also, zooplankton enter diapause, a stage of suspended development during unfavourable
conditions.
Adaptations
Adaptations are certain characteristics that organisms develop in order to survive and reproduce better in their niche.These Adaptations can be physiological, behavioural, or morphological.
Some of the Adaptations are
Desert plants: have thick cuticle on their leaf
surface and stomata arranged in deep recesses to reduce water loss. Their
special photosynthetic pathway CAM enables their stomata to remain unrestricted
during day time. Their leaves are reduced to backbones and photosynthesis is
carried out by smoothed stems.
Animals of colder regions have shorter branches and
cognizance to minimise heat loss (Allen’s rule) and the body is covered by
thick fur to reduce the heat loss. Their body has a thick layer of fat
(blubber) below their skin that acts as an insulator to minimise heat loss.
People living in high altitudes have high RBC product and
increased breathing rates.
Some desert animals are able of burrowing in order to escape the
heat. In addition, some desert creatures similar as kangaroo rat are suitable
to meet their water demand through internal fat oxidation. They also have
capability to concentrate their urine.
Population
It's a group of analogous individualities living in a geographical area, sharing similar resources, and capable of interbreeding.Population has certain attributes, which individual organisms don't retain
○ Birth rate per capita births
○ Death rate per capita deaths
○ Coitus rate − Rate of number of males to
ladies in a population
Age
distribution
A population can be composed
of individualities of different age groups.
Age distribution plot for a
given population is given by the age pyramid.
The structure of the age
aggregate determines the growth status of the population, whether it's growing,
stable, or declining.
Population size, more
technically, is appertained to as population viscosity (N), which indicates the
number of individualities inhabiting a particular niche.
If the population is huge,
also relative viscosity is measured rather of absolute viscosity whose
dimension is time-consuming.
Population Growth
The size of a population is an
ever-changing aspect since it depends upon availability of food, predation,
weather conditions, etc.
This gives us an idea whether
a certain population is growing or declining.
Some of the reasons for the increase or
decrease in population
Natality
(B) − Number of births during a given period in the given population
Mortality
(D) − Number of deaths during a given period in the given population
Immigration
(I) − Number of individualities of the same species who have come into the
niche from away during a given period
Emigration
(E) − Number of individualities of the same species who have left the niche
and gone away during a given period
If N is the population at time t, also its
density at t +1 is
Growth Models
Exponential Growth −
When the resources are unlimited, population tends to grow in an exponential
pattern.
If the population size is N
and the birth and death rates (not per capita) are b and d independently, also
increase or drop in N at t ( time period) is given by,
dN/ dt = (b − d) × N
Still, also
If (b − d) = r.dN/ dt = rN
r is the “ natural rate of
natural increase”.
Or,
Nt = N0 e rt
Where,
Nt − Population viscosity at
time t
N0 − Population viscosity at
time 0
r − Natural rate of natural
increase
e − Base of natural logarithms
(2.71828)
Logistic growth − When
the resources are limited leading to competition between individualities and
survival of the fittest, the population tends to grow in a logistic manner.
In this kind of growth,
there's an original pause phase followed by acceleration or retardation phases
and eventually asymptote, when it reaches its carrying capacity (K).
When N in relation to t is
colluded, it results in a sigmoid wind called the Verhulst −Pearl Logistic
growth given by,
r − Natural rate of natural increase
K − Carrying capacity
Life History Variations
Populations tend to increase their reproductive fitness in order to survive better. This is known as Darwinian fitness ( high r value).Some of the trends they follow by course of achieving this
o
Some organisms breed only formerly in their
continuance. Example ¬ Salmon, Bamboo
o
Some breed numerous times. Example ¬ Birds,
mammals
o Some produce a large number of small-sized offspring. Example ¬ Oyster
Some produce small number of large-sized offspring. Example ¬ , Mammals
Population Relations
A natural niche consists of numerous organisms living together and these organisms communicate and interact with each other. For example, plants depend on insects for pollination.
Interspecific interactions are relations between two different species of organisms. They can be either salutary or dangerous to one or both mates.
Interspecific relations
Predation − It's salutary to the predators while the prey is harmed.
o It acts as a means of transfer of energy to the
coming advanced trophic position and of maintaining balance in the ecosystem.
o
For plants, beasties are predatorss and some plants
produce secondary metabolites, thorns, or poisonous chemicals to ward off
predators.
o Also, creatures also disguise themselves to cover themselves from predators. Some preys are toxic or distasteful (Monarch butterfly is largely distasteful because of a special chemical it acquires during its caterpillar stage by feeding on toxic weeds) so as to avoid predators.
Competition − It occurs only in nearly affiliated species wherein they share the same type of niche and food resources.
o Still, for competition to take place resources
need not be always scarce and competition doesn't inescapably take place
between same species.
o
In competition, the fitness of one species is
significantly lower in presence of another species and survival of fittest
eventually takes place.
o Gause’s Competitive Exclusion Principle states that two nearly affiliated species contending for the same resource can not co-live indefinitely and the competitively inferior will be excluded ultimately.Also, some species may develop mechanisms to grease their co existence
Parasitism −
In this commerce, one of the mates is served because it resides outdoors or
inside the body of the host and gets free accommodation and food while the host
is affected due to loss of nutrients.
o
Spongers in nature have developed a wide
variety of Adaptations similar as hooks and suckers for attachment, loss of
digestive system, high reproducing capacity,etc.
o
Spongers can live either outdoors
(ectoparasites) or outside (endoparasites) the body of the host organisms.
o Brood parasitism is seen in birds in which the parasitic birds lays its egg in the nest of the unpretentious host raspberry, which takes care of them until they door. For example, Koel lays its eggs in the nest of the crow.
Commensalism − In this commerce, one of the mates is served while the other is neither served nor harmed . For example, an orchid growing as an epiphyte on the mango tree The orchid gets support while the mango tree is unaffected.
Mutualism or symbiosis − In this commerce, both the mates are served. For example, lichens, commerce of algae and fungi, where both are served The fungi give support to the algae while the algae prepare the food for the fungi.