1. Populations
Population- the number of individuals of a species that inhabit a particular area at the same time.

2. 2 characteristics of populations
Population Density
Population dispersal

3. Population Density
The number of individuals of a population that inhabit a certain area (land or water)
Example) there is a population of 10 million people in los angeles
Give 3 examples of population density

4. Population Dispersal
How individuals in a population are dispersed or spread out in an area.

5. 3 ways populations can be dispersed
1. Random- location of organisms is random and not dependent on other members of the species
Ex) dandelion seeds being randomly spread in a field
VERY RARE

6. 2. Clumping – Individuals of a population clump or flock together
2. Clumping – Individuals of a population clump or flock together ** most common kind**
Ex) fish swim in schools or groups
In this kind of dispersion animals “clump” near resources

7. 3. Uniform- members of population are
3. Uniform- members of population are uniformly spread out in region or area
results from competition for resources, members of a population need to spread out because of limited resources
Farmers create artificial uniform distribution

8. Factors Controlling Distributions
In eastern Connecticut, The Black-capped Chickadee’s moves its geographic range south in winter (summer left, winter right; darker colors are denser populations) because its physiological need for a warmer climate is better met there.
Winter
Summer

9. You do!
What are two important characteristics of populations- explain each
Name and describe three kinds of population dispersion & explain them
Population density and dispersal
Random, uniform, clumping
Population density and dispersal
Clump, uniform, random

10. Population Growth Questions we need to be able to answer
How do populations grow?
What determines if populations grow or not?
What patterns are there for population growth?

11. 2 Factors that regulate population growth
Density-dependent factors- certain factors limit growth. These include disease and availability of food and living space. As populations increase, mortality increases
Density-independent factors- other factors influence populations regardless of their size. These include storms, forest fires, geologic events, minimum winter temperatures and snowfall amounts.

13. Two main kinds of populations: r and K Strategists/organisms
r-selected/ r-strategist
K-selected/k-strategist
Reproduce early in life
High reproductive growth
Don’t care for young
(bacteria, amoebas)
Reproduce late in life
Have few young
Devote much time and energy to survival of young
Humans, tigers, dogs

14. Words and concepts we need to know:
Biotic Potential-The amount that a population would grow if there were unlimited resources in the environment
Are there unlimited resources in an environment? What keeps populations from reaching their biotic potential?
Start here for babies

15. Resources ARE limited in ecosystems so populations DO NOT reach their biotic potential.
Organisms reach “carrying capacity”

16. Carrying Capacity (K)
The maximum population size that can be supported by the available resources in an area.
Different ecosystems have different Carrying capacities for different species because all species have different requirements for life!

17. You do
In a forest what populations would have a high carrying capacity? Why
What is the difference between biotic potential and carrying capacity?
Give an example of an r-strategist
Give an example of a K-strategist
What species would have a lower carrying capacity- why?

19. 4 stages of population growth

20. 1. Lag phase- population grows slowly
2.Exponential Phase- population grows rapidly/ exponentially (growth exceeds death rate)
3.Stationary Phase – Population stops growing and stays relatively stable. (equal numbers of birth and death)
4.Death phase- more members are dying than being born or moving in (immigration) so the population is decreasing

21. Showing carrying capacity

22. RULE OF 70
The rule of 70 tells us how long it will take a population to double in size
Formula divided by the current growth rate
Example) The growth rate of a population is 5% per year. How long will it take for the population to double
70/5= The population will double in.

23. Everyone Practice!
US population =311 million, growth rate is How long will it take US to double?
World population is 7 billion growth rate is 1.2 How long till we double?
What happens then?
70/ = 79 years
70/1.2 = 58 years

24. Patterns of Population Growth
1. Logistic Population Growth- population grows fast at first then becomes stable and remains at carrying capacity- S shaped curve

25. Population cycles in ecosystems
In nature populations generally follow one of two patterns

26. Boom and Bust cycle
Common among r-strategists Rapid increase followed by rapid decrease- cyclical

27. Predator prey cycle

28. Predator Prey Cycle
Populations of predator and prey influence each other
Prey population grows rapidly
Predator population grows after prey is established
Prey begin to die out
Predators die out
Cycle continues.

29. Your turn:
Find the doubling rate for a population that has a growth rate of 1.5
What two cycles of population growth exist in nature
Name the 4 stages of population growth and give an example of each

30. Human Population Dynamics

31. How do populations change
Immigration – movement of people or species into a population
Emmigration – movement of people or other species out of a population
** In general these are not significant factors in population size& DO NOT affect global population ***

32. Fertility Rates Replacement level fertility (RLF)
Number of children a couple must have to replace themselves
2.1 in developed countries (DCs) in some less-developed ones (LDCs)
Have to take infant mortality into account

33. *** TFR = most significant addition to human population******
Total Fertility Rate The number of children a woman will bear during her lifetime.
Total Fertility Rate is decreasing globally however world population is still increasing.
*** TFR = most significant addition to human population******

34. Projected Birth Rates by Region

35. World Population Growth Rate

36. Goal Total fertility rate = replacement rate
Still does not equal zero population growth because of people living longer

37. Factors that affect the growth rate of Human Populations
Anything that impacts TFR (total fertlility rate) impacts population growth.
Examples>
Availability of birth control
Demand for children in the labor force
Urbanization (rural communities have children for labor)
Base level of education for women
Religious beliefs, customs and traditions

38. You do Identify and describe two factors that affect TFR
Explain the difference between TFR and RLF

39. Factors not related to TFR that affect population
DEATH RATE ALSO AFFECTS population!!!!
The reason the worlds population has grown in the past 100 yrs is due more to later death rate than higher birth rate

40. Why are people living longer?
Industrial Revolution improved standard of living
Clean water
Better sanitation (fewer diseases)
Dependable food supply
Better health care

41. 2 generalization about population
The more industrialized or developed the nation the longer the life span
Overall health of a population can be estimated by looking at lifespan AND mortality rate of infants.
Life span: Afghanistan = 44yrs. Japan = 80yrs
Infant Mortality: Afghanistan=121/1000
US= 6/1000

42. Age Structure pyramids

43. Exit ticket Name three factors that affect TFR
What are two generalizations you can make about populations?
What can age structured pyramids tell you- give at least two things.

44. Age Structured worksheet here!

45. Demographic Transitions!

46. Demographic Transition Model
Used to predict population trends based on birth and death rates of a population.

47. Environmental Resistance- anything that slows a population’s growth – such as harsh living conditions, lack of clean water, lack of medical care etc.

48. Zero population growth occurs when either:
High birth rates and high death rates
Low birth rates and low death rates.
Demographic Transition - When a population moves from situation a- to situation b

49. There are 4 stages that occur before a demographic transition happens!!
Pre Industrial State-
Slow growth
High birth rate
High death rate
Harsh living conditions

50. 2. Transitional State-
RAPID population growth
High birth rates
Lower death rates due to food, clean water, and improved health care

51. 3. Industrial State: SLOW population growth Birth rate drops
Birth rate and death rate are close but not equal
*** Developing countries are in this state**

52. 4. Post Industrial State
Population approaches or reaches zero population growth!!!!
Populations can drop below zero population growth (negative growth) (russia)

53. You Do
Describe in your own words the stages of the demographic transition model
What stage has high birth and low death? WHY
Why do countries tend towards zero population growth when industrialization occurs? Identify and describe 2 reasons.

54. Endangered/extinction
One reason so many big cats are endangered
Habitat destroyed
Prey dies
Predator has no food
Species without food go extinct