ORGANISMS AND POPULATIONS

ORGANISMS AND POPULATIONS



Organism and its environment

·       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,


N − Population viscosity at time t

 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.


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