University:
Brigham Young University
Course:
PHSCS 137 | Energy, Climate, and the Environment
Academic year:

2023
Views:

473

Pages:

34
Author:

6AstralAdventurer

POPULATION AND ITS CHARACTERISTICS Population- *Total number of indivisual in a particular species which live in a particulan area. OR * A population is a group of interbreeding organisms belonging to the same species. Composition of population- 3 → populations are not composed of series of identical indivisuals. →two majorn variables distinguish indivisuals in a population - sex and age. Attributes of Population- →Population attributes" ane characteristics of a population that characterise its characteristics such as growth pattern, population density, and population regulation →Population has some attribute- 1) population density 2) Natality 3) Mortality 4) Dispersion. carrying capacity :- Maximum number of indivisuals of a population that ecosystem can support is called its carrying capacity. an Population Density :- → population Density can be defined as total number of indivisuals pen unit area on volume of environment at a given time. →Population density may also changes with seasons, weather conditions and food supply and with many other influences. →Population density gives us information about the magnitude of the population but does not provide any information about the distribution pattern of the population within an environment. → on the basis of pattern of distribution density can be two types- meet 1) crude density to 2) Ecological density 1) crude density:- crude density is the population density per unit total space Ex. The number of Rhinoceros living in the Kaziranga National park. 2) Ecological density :- →Ecological density is the population density perr the unit habitatspace. ie available area on volume that can actually by colonized by the population. Population Size- →Population size refers to total number of indivisual of an population -> It is determine by process of birth (B), death (D), immigration (1), emmigration (E). (Ps) 1 = Ps + B +D+I+E Mark Recapturre technique:- → It is used to estimate population size of a species. → It consist of 3 steps -1) Mark 2) Release 3) Recapture. Process- 1) Small random sample of population is captured (sample 1 on Si). 2) Mark and release the sample 1 to disperise within the general population. 3.) Mark indivisuals now mix freely with the unmanik indivisual 14) Population is re-sample (sample 2 onsa) 5) Determine the number of mark and unmank indivisuals in the sample 2.. 103 Population size SXS = 3 Natality:- Natality - Number of birth Natality rate- Number of birth per unit time. → Natality refers to the number of births during a given period in the population Natality is a positive factor that increases population size → Natality is also known as birth rate. - It shows a positive effect on the population density because it results in the addition of number of individuals to a population. components of Natality :- > Fertility 2) Fecundity 1) Fertility- →The organisms capable of breeding. 2) Fecundity- → It is the number of offspring produce by a female during time period. Types of Natality :- a) Maximum Natality b) Ecological on Realized Natality. a) Maximum Natality: → It is also known as absolute ore potential or physiological Natality is not limited by environmental factor but by physiological factor. Theoritical maximum number of offspring produce in the ideal condition. Maximum natality is constant for each species. → -> It is also called fecundity rate. b) Ecological Natality :- (Realized Natality): →Number of birth under existing environmental condition. Ecological Natality is controlled by population size. and enviromental condition. It is also known as fertility rate. It is not constant for a population but may vary with the size and composition of the population and the Physical environmental conditions. Factors affecting Natality:- The age of first reproduction. ) Number of offspring produced per occassion. 2 3) Gap between two reproductive events. ③ Mortality :- dimitts to nod Mortality- Number of death in a population.. Mortality rate - Number of death in a unit time. Mortality refers to the number of death in a population during a given period of time. Types of mortality:- It has a types - 1) Minimum mortality 2) Ecological mondality 1) Minimam mortality:- →unden the ideal condition moritality occurs due to astag old age. May not be constant per a population mate. Population increases. When birth rate is more than death rate. population constant when, birth rate is equal to death rate. Population decreases when binth rate is less than death rate. Types of Lifetable:- Basically, there are two types of life table's :- 1) Horizontal Gohont / Feccundity Lifetable 2) vertical Static life table 1) Cohort/Fecundity Lifetable:- → A group borun at the same time is called " cohort refers to a group of indivisuals, all of whom have same age. a cohort →→Lifetable obtained from collecting data of a cohort is called cohort life table on horizontal life table. It is also called as fecundity lifetable. Cohort lifetable is used to determine age specific survival mortality and reproduction. Static lifedable Static life table is used to determine pattern of survival in a population by recording age of death. of indivisuals →The table is called static because the method involves a snapshot of survival within a population during a short interval of time. Ideally in static life-table, population is neither increasing nom de decreasing. Static tables make two important assumptions:- -The population has a stable age structure, that is, the proportion of indivisuals in each age class does not change from generation to generation The population size is on nearly stationary. Survivorship Curves :- Survivorship cunve is a graphical representation of number of indivisuals alive in a population at various age. When proportion of surviving indivisuals is plotted on y-axis and age class is plotted on x-axis, we get survivorship curve. - It is 3 types! 1) Type. I (convex type) tena 2) Type-1 (ToRagonal). 3) Type-1 (concave type) Type-1 (convex type):- → Mondality rate is low in but high in old age. young and adult indivisuals - They are Iteroparous times. Te they reproduce multiple They have low number of offspring. and high parential care..." per occassion Typer species includes humans and lion (large mammals). Type-2 (Diagonal) → They shows a specific constant mortality rate. →Type- species are binds, reptiles Type-3 (concave type)!- →High mortality, mate in early age later stage. as compare to They are semelpanous ie they produce lange numberr of offspring on a single occassion before they die. As they have large no. of offspring they Show less parential care Ex Type-3 Species are Insects, shell fish, oysten. Age Ratio:- → Age Ratio is the relative aboundance of indivisual of various age in a population.in It is also called age distribution. Age ratio influences natality and montality. → Chances of mortality is high in early and later Stages → Natality restricted to middle age indivisual. Age ratio is directly related to growth rate of population → Indivisuals of population can be categorised into 3 group-1) pre-reproductive-young indivisuals 2) Reproductive Mature adult 3) Post-reproductive - Old age indivisuals. Age Rynamid →Age distribution in a population can be represented in the form of age pyramid. Number of indivisuals on percentage in different age class can be shown by relative width of consecutive horizontal barns. On the basis of age pyramid population can be 3 types: 1) Expanding population 2) Stable population 3) Diminishing population Expanding population :- It is characteristic of populations having high birth rates and exponential growth generation becomes. So that each more and more numerous Age Pyramid is triangular shape with broad base. past reproductive Reproductive -Pre reproductive (Expanding population) 2) Stable population:- →It indicates a moderate population of young to old. In rapidly growing young population, birth rate is slow and stable te pre-reproductive and reproductive ages become more on less equal in size Post reproductive age becomes smallest resulting in a bell-shaped pyramid 3) Diminishing population :- → It indicates a low percentage of young indivisuals te low birth rate. Population is dying off. If the binth mate is drastically reduced, pre-reprodur- tive group dwindles in a population, to the other two groups resulting in an unn shaped pyramid. Age pyramid is urn-shaped. post-reproductive. -Reproductive -pre-reproductive Diminishing populatia Sex ratio- →Proportion of male and female indivisual in a population is called sex ratio م →The sex ratio also changes with the age because of differences in the mortality of the male and female indivisuals The sex riatio can be categorised into two types:- 1) Primary sex ratio (1) this 2) secondary sex ratio (2) 1) primary sex ratio:- →It is the ratio of male and female at the time of conception and it tends to be 1:1 - Sexually reproducing organism in a population. tends towards 1:1 sex natio conception.. before birth So, 1° sex natio is 1:1 2) Secondary sex ratio- → It is the mafio of male and female indivisuals at the time of birth. →This ratio inclined towards males in younger age but in the older age it shifted towards females. Population Dispensat- →Dispersal is an ecological process which affect distribution and genetic make up of a population. →Dispersal is a key feature of all organisms that allow their indivisual to move across the landscape. In plants, In plants seeds are dispensed by air, water or through animals. Larger on heavier seeds are dispensed to a shonter distance where as dispersal of lighter, seeds ar occurs to a larger distance. - In animals, -In animals indivisual moves by active proces -Animals eat fricits from plants and carry the a distance seeds to * population dispersal is the movement of indivisuals on their disseminules on priopagules (seeds, spories, larvae, etc.) into out of the population or population area It is also an important component in gone flow and the process of speciation. Factors affecting dispensal :- → crowding- crowding is the situation in which case, a large number of animals, including in environmental space. man are restricted → Range of temperature → Shortage and quality of food. → Due to climatic condition. Forms of Dispersal:- 1) Immigration- (Movement into a population) → Immigration is one way inwand movement of organisms into a population which is useful for sunvival & reproduction → people may choose to immigrate for a variety of reasons, such as employment opportunities, to escape a violent conflict, environmental factors, educational purposes, on to reunite with family. 2) Emigration- (Movement out of a population) Emigration is outward movement of organisms in one direction from a given population. Emigration occuns due to shortage of various resources like food & shelten and unfavorable environment. • Emigration has an economic impact on the countries involved, including the workforce and consumen spending. Migratio Migration is movement a two way periodic on seasonal of animals occuring between breeding place and feeding place. Migration occurs in mammals, birds, fishes causes of Migration - Now a days, many people have a better life. decide to migrate to Employment opportunities are the most common reason due to which people migrate Positive impact of migration- - unemployment is reduced and people get better job opportunities. - Migration helps in improving the quality of life of people. "Children get bettere opportunities for higher education. It helps to improve social life of people as they learn about new culture, customs, and languages which helps to improve brotherhood among people. Negative impact of migration - - Having large population puts too much pressure on natural resources, amenities and services. -poverty makes them unable to live a- norimal and healthy life - Mignation changes the population of a place, therefore the distribution of the population is uneven in India. 4) Nomadism- It is the random movement of indivisual from one place to another in search of food and shelter. population Dispersion :- →Distribution patterins of indivisuals within a population is called population dispension. It is of 3 types - 1) Random dis pension 2) Uniform dispersion 3) clumped dispersion 1) Random Dispersion - position in random dispersion position of one indivisuals is unrelated to another indivisuals. There is lack of distribution pattern There is lack of strong attraction, on repulsion forice between indivisual of population... Random dispension is very rare because resources in nature ane rarely randomly present - Ex- Rooted plants, penguine