Download - Chapter 20
![Page 1: Chapter 20](https://reader036.vdocuments.site/reader036/viewer/2022070319/55825fddd8b42a09258b5422/html5/thumbnails/1.jpg)
Chapter 20
Populations
![Page 2: Chapter 20](https://reader036.vdocuments.site/reader036/viewer/2022070319/55825fddd8b42a09258b5422/html5/thumbnails/2.jpg)
3 Properties of Populations
Population Size
Population Density
Population Dispersion
![Page 3: Chapter 20](https://reader036.vdocuments.site/reader036/viewer/2022070319/55825fddd8b42a09258b5422/html5/thumbnails/3.jpg)
Population Size
Population-groups of organisms that belong to the same species and live in a particular area at one time
Population size-number of individuals a population has
Sometimes there are too many to count so a sampling is used.
Scientists count a number of organisms in a certain area and multiply the area.
![Page 4: Chapter 20](https://reader036.vdocuments.site/reader036/viewer/2022070319/55825fddd8b42a09258b5422/html5/thumbnails/4.jpg)
Population Density
Population density-measures how crowded a population is
The number is always expressed as the number of individuals per unit of area or volume
Some areas are densely populated and others are sparsely populated
![Page 5: Chapter 20](https://reader036.vdocuments.site/reader036/viewer/2022070319/55825fddd8b42a09258b5422/html5/thumbnails/5.jpg)
Population DispersionDispersion is the spatial distribution of individuals within a population.There are three types of dispersion.Clumped dispersion occurs because resources and living space is clumped or because of behavior, herdingEven dispersion is the result of social behavior and organisms stay as far away from each other as possibleRandom dispersion results from wind distribution of seeds so plants usually have a random dispersal
![Page 6: Chapter 20](https://reader036.vdocuments.site/reader036/viewer/2022070319/55825fddd8b42a09258b5422/html5/thumbnails/6.jpg)
Types of Dispersion
![Page 7: Chapter 20](https://reader036.vdocuments.site/reader036/viewer/2022070319/55825fddd8b42a09258b5422/html5/thumbnails/7.jpg)
Population Dynamics
All populations are dynamic, meaning they change in size and composition over time.
Birth rate-number of births over time
Death rate (mortality rate)-number of deaths over time
Life expectancy- how long on average an individual is expected to live
![Page 8: Chapter 20](https://reader036.vdocuments.site/reader036/viewer/2022070319/55825fddd8b42a09258b5422/html5/thumbnails/8.jpg)
Stopassignments: Lesson of the Kaibabhomework: Population Growth Graph
![Page 9: Chapter 20](https://reader036.vdocuments.site/reader036/viewer/2022070319/55825fddd8b42a09258b5422/html5/thumbnails/9.jpg)
Age Structure
Age structure-distribution of individuals among different ages in a population
Different countries have different age structures.
We can use graphs to compare age structure.
![Page 10: Chapter 20](https://reader036.vdocuments.site/reader036/viewer/2022070319/55825fddd8b42a09258b5422/html5/thumbnails/10.jpg)
![Page 11: Chapter 20](https://reader036.vdocuments.site/reader036/viewer/2022070319/55825fddd8b42a09258b5422/html5/thumbnails/11.jpg)
![Page 12: Chapter 20](https://reader036.vdocuments.site/reader036/viewer/2022070319/55825fddd8b42a09258b5422/html5/thumbnails/12.jpg)
![Page 13: Chapter 20](https://reader036.vdocuments.site/reader036/viewer/2022070319/55825fddd8b42a09258b5422/html5/thumbnails/13.jpg)
![Page 14: Chapter 20](https://reader036.vdocuments.site/reader036/viewer/2022070319/55825fddd8b42a09258b5422/html5/thumbnails/14.jpg)
![Page 15: Chapter 20](https://reader036.vdocuments.site/reader036/viewer/2022070319/55825fddd8b42a09258b5422/html5/thumbnails/15.jpg)
Survivorship Curves
The mortality rate data of different species tend to conform to one of three curves on a graph.Type I organisms are more likely to die later in life. (humans and elephants) k-selectedType II organisms have a linear look because the probability of dying does not change. (birds)Type III organisms are more likely to die earlier in life. (oysters, salmon, insects) r-selected
![Page 16: Chapter 20](https://reader036.vdocuments.site/reader036/viewer/2022070319/55825fddd8b42a09258b5422/html5/thumbnails/16.jpg)
Survivorship Curves
![Page 17: Chapter 20](https://reader036.vdocuments.site/reader036/viewer/2022070319/55825fddd8b42a09258b5422/html5/thumbnails/17.jpg)
More Curves
![Page 18: Chapter 20](https://reader036.vdocuments.site/reader036/viewer/2022070319/55825fddd8b42a09258b5422/html5/thumbnails/18.jpg)
Population Growth Rate
Growth rate- the amount by which a population’s size changes over time
Immigration-individuals moving into a population
Emigration-individuals moving out of a population
![Page 19: Chapter 20](https://reader036.vdocuments.site/reader036/viewer/2022070319/55825fddd8b42a09258b5422/html5/thumbnails/19.jpg)
STOP
Assignments: Human Population Growth graph
Homework: w.s 20-1
![Page 20: Chapter 20](https://reader036.vdocuments.site/reader036/viewer/2022070319/55825fddd8b42a09258b5422/html5/thumbnails/20.jpg)
Exponential Growth Model
Exponential Model- population increases rapidly after only a few generations; the larger the population gets, the faster it growsLimiting factor-a factor that restrains or stops the growth of a populationLimiting factors are available resources, space, waste accumulation, population density
![Page 21: Chapter 20](https://reader036.vdocuments.site/reader036/viewer/2022070319/55825fddd8b42a09258b5422/html5/thumbnails/21.jpg)
![Page 22: Chapter 20](https://reader036.vdocuments.site/reader036/viewer/2022070319/55825fddd8b42a09258b5422/html5/thumbnails/22.jpg)
Logistic Growth Model
Logistic model-builds on the exponential model but adds the limiting factors.
Carrying capacity (K)- the number of individuals the environment can support over a long period of time
Once carrying capacity is reached, the population remains constant
![Page 23: Chapter 20](https://reader036.vdocuments.site/reader036/viewer/2022070319/55825fddd8b42a09258b5422/html5/thumbnails/23.jpg)
![Page 24: Chapter 20](https://reader036.vdocuments.site/reader036/viewer/2022070319/55825fddd8b42a09258b5422/html5/thumbnails/24.jpg)
Population Regulation
Density-independent factors-weather, flood, fires; these reduce the population regardless of size
Density-dependent factors- food, nesting sites, illness; these occur as a result of population size
![Page 25: Chapter 20](https://reader036.vdocuments.site/reader036/viewer/2022070319/55825fddd8b42a09258b5422/html5/thumbnails/25.jpg)
Perils of small populations- Inbreeding
The rapidly growing human population has caused extreme reductions in the populations of some other species and subspecies.Fewer than 200 Siberian tigers remain in the wild due to over hunting and habitat destructionThe California condor is down to 9 individuals.Fewer individuals means inbreeding or mating with relatives.This mean the babies will be more likely to have defects or diseases.