Population Characteristics in brief.pptx

The document explains the population characteristics like natality, mortality, age structure, growth curves etc in brief

1. Population Characteristics

2. A population refers to a group of organisms of the same species that live and interact within a specific geographic area.

3. Defining a Population in Ecology 1 Geographical Boundary A population is defined by the geographical area it occupies, which can range from a small local community to a large regional or global scale. 2 Reproductive Interactions Members of a population are able to interbreed and produce fertile offspring, maintaining the genetic continuity of the group. 3 Shared Resources Individuals within a population share and compete for the same essential resources, such as food, water, and shelter, within their defined habitat.

4. Factors Affecting Population Size Biotic Factors These include the availability of food, the presence of predators, the prevalence of diseases, and the level of competition within the population. Abiotic Factors Environmental conditions such as temperature, rainfall, sunlight, and soil quality can significantly impact the size and health of a population. Human Influence Human activities, such as habitat destruction, pollution, and overexploitation, can dramatically alter population sizes, sometimes leading to the decline or extinction of species.

5. Natality 1 Natality Rate of reproduction or birth per unit time Natality= Number of birth per unit time Average population Maximum number of birth produced by individual under ideal condition – Potential natality/Reproductive potential/biotic potential Actual no. of births occurring under existing conditions- realized/ecological natality It is not constant in the population If natality is low then the population density is also low

6. Mortality 2 Mortality Rate of deaths per unit time Mortality= Number of deaths Time Minimum number of loss of individuals under ideal condition – Potential mortality/Minimum mortality/specific mortality Actual no. of births occurring under existing conditions- Realized/ecological mortality It is affected by density, competition, disease, predation and environment Net Population Change The difference between natality and mortality rates determines the net population change, which can be positive (growth), negative (decline), or zero (stagnation).

7. Population size and Density 3 Population Size Population size refers to the total number of individuals within a defined geographical area. 4 Population Density Population density is the number of individuals per unit of area or volume, providing a more standardized measure of population size. Affected by environmental factors, geographical factors, natality, mortality, emigration and immigration Measurement Techniques Ecologists use various methods, such as direct counts, mark-recapture studies, and sample quadrats, to estimate population size and density.

8. Emigration and Immigration Emigration Emigration refers to the movement of individuals out of a population, either permanently or temporarily. Factors like resource scarcity, conflict, or the pursuit of better opportunities can drive emigration. Immigration Immigration is the movement of individuals into a population from elsewhere. Immigration can have significant impacts on the size, composition, and dynamics of a population. Net Migration The balance between emigration and immigration, known as net migration, can be a critical factor in determining the overall population change within a defined geographical area.

9. Age Structure and Pyramids

10. Age structure Pre-reproductive Reproductive Post-reproductive - A/c to Bodenheimer Depending on the proportion of the individuals in each group, we can say about the reproductive status of the population Age Pyramids Pyramidal models or graphs represent the age structure of the population

11. Young population- Positive Growth Populations with a large proportion of young individuals, such as those found in developing countries, tend to have high birth rates and rapid population growth. Stationary /Zero growth Populations with a stable age distribution, where the proportions of young, middle-aged, and elderly individuals are relatively equal, typically exhibit slow or stagnant growth. Aging Populations- Negative Growth Populations with a high proportion of elderly individuals, such as those found in developed countries, often experience declining birth rates and slower population growth or even population decline.

12. Population flutuations The size and density of natural population showing a changing pattern over period of time. The variation in the population change are: Non-Fluctuating - Population remain static over years Cyclic- The seasonal or annual changes occur in population and the addition to the population at the time of maximum reproduction and losses under adverse climatic conditions. Irruptive - Change in the population density does not occur at regular intervals or in response to any obvious environmental factor

13. Survivorship curve

14. Population Growth Patterns Exponential Growth In the absence of limiting factors, populations can exhibit exponential growth, with the population size increasing at a constant rate over time. Logistic Growth In the presence of limiting factors, such as resource availability or environmental constraints, populations often exhibit a logistic growth pattern, with a gradual slowing of the growth rate as the population approaches the carrying capacity.

15. Carrying Capacity and Population Regulation Carrying Capacity The carrying capacity of an environment refers to the maximum population size that can be sustained within that environment, based on the available resources and environmental conditions. Density-Dependent Factors As a population approaches its carrying capacity, density-dependent factors, such as competition for resources and increased predation, can act as negative feedback mechanisms to regulate population growth. Density-Independent Factors Density-independent factors, such as natural disasters, climate change, and disease outbreaks, can also significantly impact population size and growth, regardless of the population's proximity to the carrying capacity.

16. Applications of Population Ecology Principles Conservation Understanding population characteristics is crucial for developing effective conservation strategies to protect endangered species and maintain biodiversity. Resource Management Knowledge of population dynamics can inform sustainable management of natural resources, such as fisheries and forestry, to ensure long-term availability. Urban Planning Population ecology principles can guide urban planning and development to accommodate growing human populations while minimizing environmental impacts. Disease Control Analyzing population characteristics can help predict and mitigate the spread of infectious diseases, contributing to public health efforts.