Extinctions & Age Structured Populations

Extinctions & Age Structured Populations 

Introduction

Population dynamics  

Population dynamics refers to the study of how and why populations change in size and structure over time. Population dynamics are influenced by rates of reproduction, death, and migration. The term population dynamics refers to how a species’ populations vary over time. 

Interdemic extinction 

The death or extinction of a species is referred to as extinction. Extinction happens when a species becomes extinct as a result of environmental influences (habitat fragmentation, global change, natural disaster, overexploitation of animals for human purpose) or evolutionary changes in its members (genetic inbreeding, poor reproduction, decline in population numbers). A dead or nearly extinct species no longer contributes to the evolution of creatures, but it can help us understand the link between extant, or living, animals.  

The decrease of a species to such low abundance that, while it is still present in the community, it no longer interacts meaningfully with other species,” according to the definition of ecological extinction. Ecological extinction stands out because it is the interaction ecology of a species that is vital for conservation activity. Unless the species interact significantly with other species in the community, its extinction may have little to no effect on the abundance and population structure of other species.  

Major element of extinction 

Extinction is a possibility for species as a whole if the lethal stress is so infrequent that it is beyond their experience and hence beyond the grasp of natural selection. The mass extinctions would prepare the way for a significant rebuilding of the biosphere in which a few successful groups would be destroyed, enabling smaller groups to thrive. In a few situations, there is evidence that Darwin selectively argues for extinction. It is now difficult to anticipate which species will be the next to perish in an extinction event.  

Causes of extinction 

Asteroid strikes: 

A meteor impact on Mexico’s Yucatan peninsula caused the extinction of dinosaurs millions of years ago. Most large extinctions, such as the KT-extinction and the Permian-Triassic extinction, were triggered by such occurrences.  

Climate change: 

Climate change is another cause that has the potential to wipe out terrestrial creatures. Most megafauna were unable to adjust to the warm temperatures at the end of the last ice age. 

Disease: 

Various diseases have resulted in the extinction of a vast population of humans and animals on the planet.  

Loss of habitat: 

The destruction of forests, which are home to the majority of animals, has resulted from the growth of human civilization and industrialization. Many species’ populations have been diminished as a result of a lack of space and, eventually, food.  

Lack of genetic diversity: 

As the number of species decreases, so does the gene pool of that species. There will ultimately be a genetic diversity scarcity.  

Pollution: 

Pollution from factories and cars has resulted in a significant decrease in oxygen levels in the atmosphere and water. This has resulted in the extinction of the majority of aquatic and terrestrial species.  

Overhunting: 

The ivory of elephants, the fur and organs of tigers, the delicacy of tuna, and the allegedly curative benefit of shark’s fin are just a few of the reasons mankind have hunted these species to extinction. 

Acid rain: 

When Sulfur dioxide and/or nitrogen oxides are released into the atmosphere, acid rain develops. The chemicals are absorbed by cloud droplets and finally, fall to the earth as acid precipitation. Acid rain raises the acidity of the soil, which has an impact on plant life. It may also wreak havoc on rivers and lakes, perhaps resulting in death. 

Species introduced: 

Humans frequently relocate species, introducing species that are not native to an environment and disturbing the delicate balance that has formed among the species in that ecosystem. Species can be transported in both unintentional and planned ways. Introduced species may compete for food or nesting places with native species, or they may prey on native species. As humans expand into more isolated areas, we enable other animals to do the same by building roadways. Furthermore, we move species via the sea. Ships take on water for ballast in one spot, cruise across the ocean, and then discharge the ballast water, bringing new aquatic life forms to ecosystems already populated by other species. 

Changes in sea levels or currents: 

Changes in sea levels and currents are caused, in part, by melting freshwater. Denser, saltier water sinks and creates the currents on which marine life depends. Sea level is also affected by the spreading and rising of the ocean floor. A minor increase in the ocean floor can cause a large amount of water to be displaced onto already populated land. Volcanic gases may also be absorbed by water, altering its chemical makeup and rendering it unsuitable for some organisms. 

Age structured population 

The age structure of a population is an essential component in population dynamics. The proportions of people of different ages in a population are shown as a bar graph with younger people at the bottom and men and women on either side. The distribution of persons of various ages is the age structure of a population. It is an important tool for social scientists, public health and health care professionals, policy analysts, and policymakers since it depicts demographic patterns such as birth and death rates. 

Age structure and age pyramids can take many different shapes, based on population birth and death rates, as well as a number of other social variables. 

They might be: 

• Stable: Birth and death trends do not change over time. 
• Stationary: Both birth and death rates are low. (they slope gently inward and have a rounded top) 
• Expansive: Slopes sharply inward and upward from the base, suggesting a population with both high birth and mortality rates. 
• Constrictive: Indicating low birth and mortality rates and extending forth from the base before sloping inward to form a rounded peak at the top.  

The fast growth graph narrows to a point, suggesting that the number of people reduces rapidly as they get older. The number of people in the slow growth model drops progressively with age. The top of stable population graphs is rounded, indicating that the number of people in each age group declines gradually and subsequently increases for the elderly population. Stage 4 reflects a declining population.  

Summary

• Extinction is the death or extinction of a species.
• It happens when a species becomes extinct as a result of evolutionary changes in its
  members.
• The decrease of a species to such low abundance that, while it is still present in the community, it no longer interacts meaningfully with other species,” according to the definition of ecological extinction.
• Extinction is a possibility for species as a whole if the lethal stress is so infrequent that it is beyond their experience and hence beyond the grasp of natural selection.
• The age structure of a population is an essential component in population dynamics.
• The proportions of individuals of various ages in a population are depicted as a bar
  graph.
• The distribution of persons of various ages is the age structure of a population. .
• It is an important tool for social scientists, health care professionals, and policymakers
  since it depicts demographic patterns such as birth and death rates.
• Age structure and age pyramids can take many different shapes, based on population birth and death rates.