Populations

1. Populations Growth and What We Can Learn From Studying Them

2. Population growth: A case Study • Current estimates put the rabbit population in Australia at close to 200 million. • What does this mean to us? • Can this really be meaningful? This is “information”. Factual. No relevance though. TIME (Year)

3. Population growth: A case study • In the 1920’s there were an estimated 10 billion rabbits. • Current estimates put the rabbit population in Australia at close to 200 million. • Does this new information change anything? (represented graphically) • Can we say this is now meaningful? 2 data points. We can see a change. We can start identifying causes and effects. If the trend continues, we can predict. TIME (Year)

4. Population growth: A Case Study • Rabbit are not native to Australia. • Two dozen (24) rabbits were introduced to Australia in 1850. • By the 1920’s there were an estimated 10 billion rabbits. • Current estimates put the rabbit population in Australia at close to 200 million. • What do you think know? TIME (Year)

5. Studying populations: A Case Study. • In the 1850’s, an English man introduced two dozen (24) rabbits to his new home in Australia, “to remind him of home”. • By the 1920’s there were an estimated… 10. BILLION. RABBITS! • After spiking, efforts to reduce the rabbit populations started making an impact, but current estimates are still close to 200 million. • How does more information change your interpretation? • Do you think that the rabbit population had/has an affect on their new ecosystem? What affect? How do we know? • Think about these for a minute.

6. Essential Question • We often hear about how populations are being impacted. • “Humans are impacting (fill in the blank) (fill in the way)”… • Is this positive? • Is this negative? • Essential Question: • How do we know if a population is being effected? • We’re going to spend the next week or so looking at this, populations.

7. Guiding Questions First: What is a “population”? How do we know if a population is being effected? • Before we can determine is a population is being effected, we have to break this question down a little more and examine the parts like we did last section. Next: How can we determine the measurable characteristics of a population? Also: How do we determine what “effected” means? Also: What does it look like when multiple populations are interacting? In addition: What are causes that could have “effects”? Last: How does human population growth look like and what can we learn from it?

8. Defining Terms: What is a “population” • In our lives we use words that don’t really mean what they truly mean and most of the time that doesn’t matter. • Populations and communities are two words that apply. • It’s important that science is disciplined in its activities so that its conclusions can be taken seriously and confusion is reduced. • Terminology is foundational. • A population is a group of organisms that are the same species, living in the same place at the same time, and interbreed. • All of these details matter for various reasons, but we at least need to know what a population is before we can start analyzing one or more. • As opposed to community. A community is considered all the living things in an ecosystem, all the biotic factors in an area, the collection of all populations in an ecosystem.

9. Cleaning up Terminology • We’re going to be using some terminology that needs to be formalized so we don’t get confused about what we’re talking about. • When we talk about “populations” in ecology I don’t want you to be confused with “communities”. • When I talk about a “biome” I don’t want you to get confused with an “ecosystem”. • The following slides will clear this up.

10. Levels of Organization • Living systems are organized starting with each individual playing their part. • Individual = one living being. • Every living being is a member of a larger group, called a species. • Species are defined by all individuals that are capable of reproducing to make offspring that are able to, themselves, have more offspring. • Sometimes, organisms of different species can reproduce, but they produce sterile offspring. • Ligers, tigons, mules. • This elk, pictured here, is one individual.

11. Levels of Organization • Individuals of the same species organize to form a population. • Population = all individuals of the same species that coexist within the same ecosystem. • Sometimes multiple populations of the same species are isolated from one another due to geography. • The three elk, pictured here, represent part of a population because they are all the same species. • If these elk were separated by a land mass they would be the same species but different populations.

12. Levels of Organization • It is difficult to find any ecosystem where there exists only one type of organism. • They do exist though (chemoautotrophs) • In all other instances, multiple populations (species) exist within the same ecosystem. • This forms a community. • Elk, bear, owls, rabbits, and the various plants populations represent the community in this ecosystem. • Community = the combination of all the living species within an ecosystem.

13. Levels of Organization • In an ecosystem, there is a lot going on. • Once we expand outward, we start to look at all the factors that influence the living things. • Both the living (communities, biotic factors) and the non-living. • If we add in the climate, soil, nutrient cycles, etc, we could define the ecosystem. • Ecosystems include variable habitats • Ecosystem = a system including all the biotic and abiotic factors interconnected within same region by the cycling and transfer of energy and nutrients.

14. Levels of Organization • If we expand the scope of organization beyond life we start to see themes that exist in major areas due to the major climate patterns of that region. • Plants and animals that exist in dry climates have particular traits that make living possible. • If you were to place these living things in an alternative environment their success would decline. • A Biome is a formation of plants and animals that have common characteristics due to similar climates.

15. Interactions. • It should be understood from out last section that organisms in communities interact with each other. • Grass (population1)  deer (population 2)  wolves (population 3) • This is about getting energy and matter. • Part of our EQ is to determine “HOW” changes happen. • As our rabbit example helped illustrate, words, an often just the numbers don’t help a low. • Populations are illustrated graphically so we identify trends so we can defend claims for why a population is changing. • Just what do these populations look like, graphically?

16. Graph Your Data For a Deer Population RANGE OF DV Why start at zero? RANGE OF IV STALK YOUR GRAPH SCALE TITLE AXES LABLES KEY What depends on the other; population or time? ______________ depends on ______________. That makes ____________________ the “dependent” variable. The dependent variable always goes on the Y axis. The other variable is the independent variable. This variable is usually graphed on the X-axis.

17. Population of Deer (1935-1980) Population growth Relevant TITLE Population of Deer (Individuals) 0 50 100 150 200 250 300 DV LABEL SCALE KEY only needed if there are multiple data sets. N/A here. DV on Y AXIS SCALE IV LABEL • ’40 ’50 ’60 ’70 ’80 ‘90 • TIME (Year) IV on Y AXIS

18. Population Growth • Population Growth is the quality of population change over time. • Is it solved by identifying the difference in the population at one time versus a time in the past or future, a change from some existing state. • Growth is calculated by using the equation… • Growth = Population2 – Population1 • The quality of the change over time can be determined as… • Positive (+) Negative (-) or Neutral (0)

19. Population Growth • Population is determined a variety of ways but Populations Change occurs because of… • Unfortunately, it’s difficult to identify trends revealed in raw data so it needs to be graphed. • Once population changes are graphed over an extended period, we can analyze the trends present and determine if the growth is healthy or not. • “Healthy” is a feature we’ll develop. And can be compared to Growth Models, which are types of generic growth.

20. Population growth… How do Populations Grow? How does the size of your population grow? Growth = Population2 – Population1 = Population change Population change = (Births + Immigration) – (Deaths + Emigration) Population of Deer (Individuals) 0 50 100 150 200 250 300 • ’40 ’50 ’60 ’70 ’80 ‘90 • TIME (Year)

21. Population growth… Positives Why Rapid Growth? Population of Deer (Individuals) 0 50 100 150 200 250 300 Why (+) Growth? Many births more than the parents: Example: 10 offspring Or many mating couple Why Slow Growth? B+I > D+E A few births more than the parents: Example: 3 offspring Or a few mating couples • ’40 ’50 ’60 ’70 ’80 ‘90 • TIME (Year)

22. Population growth… Negative growth? Why Negative Growth? Population of Deer (Individuals) 0 50 100 150 200 250 300 B+I <D+E Fewer births than parents. Example. Only 1 child. Or high mortality. • ’40 ’50 ’60 ’70 ’80 ‘90 • TIME (Year)

23. Population Growth Models Linear Growth • Once graphed, population growth helps reveal trends, which can help us determine the health of a population or understand the root causes or effects. • Model 1: Linear Growth: • This is standard growth. • Like a paycheck or a recurring bill • For populations, predictions, such has how often a population doubles, is always the same amount of time. • Linear growth is a line • This growth can be • (+) • (-) • Neutral (0) as well

24. Population Growth, continued • Model 2: Exponential growth occurs when numbers increase by a certain factor in each successive time period. • For example: • Y (# of individuals) = X2 (time) • This type of increase gives the J-shaped curve of exponential growth. • In exponential growth, population size grows slowly when it is small (called the lag phase). • But as the population gets larger, growth speeds up dramatically. • You will see that there are issues we need to consider if a population grows this way.

25. Population Growth • Model 3: Logistic growth is population growth that starts with a minimum number of individuals and reaches a stabilized population. There are three growth rates in logistical growth. • Lag Phase = Initial slow growth • A stage of exponential growth • Stabilization Take note of the shape. What does it look like? Stabilization

26. Population growth Which growth model does our graph MOST look like? Population of Deer (Individuals) 0 50 100 150 200 250 300 EXPONENTIAL STABLIZATION LAG • ’40 ’50 ’60 ’70 ’80 ‘90 • TIME (Year)

27. Population growth Population of Deer (Individuals) 0 50 100 150 200 250 300 Why Stabilization? = B+I = D+E What should be noted is though our graph isn’t exactly like the model, it is still logistic. Why? Because only logistic growth achieves some sort of stability, even if it isn’t perfect. • ’40 ’50 ’60 ’70 ’80 ‘90 • TIME (Year)

28. Population growth: Predictions 4. What can account for why the population declined? What become problems as populations increase? Population of Deer (Individuals) 0 50 100 150 200 250 300 • ’40 ’50 ’60 ’70 ’80 ‘90 • TIME (Year)

29. Population growth: Predictions Population of Deer (Individuals) 0 50 100 150 200 250 300 5. What can account for why the population rebounded? What were problems but are not anymore? • ’40 ’50 ’60 ’70 ’80 ‘90 • TIME (Year)

30. Population growth: Predictions Population of Deer (Individuals) 0 50 100 150 200 250 300 What happens at the peak that goes away as population decreases? Answer = COMPETITION. • ’40 ’50 ’60 ’70 ’80 ‘90 • TIME (Year)

31. Population growth: Predictions Population of Deer (Individuals) 0 50 100 150 200 250 300 6. What are going to be issues to regardless of population size?... • ’40 ’50 ’60 ’70 ’80 ‘90 • TIME (Year)

32. How would these examples impact a population? How would the population influence these factor’s impact? • This list are things that have positive and negative impacts on life. • Read the list and determine if the event is living (BIOTIC = B) or not (ABIOTIC = A). • Then determine if a population size • makes this event more impactful (DENSITY DEPENDENT = DD) or • Is irrelevant (DENSITY INDEPENDENT = DI) • Earthquake • Poaching • Shelter • Not much food • Water • Invasive species • Many Mates • Few Mates • Lots of predators • Clear-cutting • High rainfall • Contagious viral infections • Building a mall • Lots of rain • Few predators • Contagious bacterial infections • Drought • Forest fire • Genetic disorder • Bunch of extra food • Restricted hunting • Logging

33. Food Mates Number of Offspring Predation Contagious bact. Invasive species + Human impact: Responsible farming Logging Controlled burns Factors Affecting Population: Complete your chart. • Nesting Sites (shelter) • Water • Camouflage • Contagious viral infections • Depends on how you define these: • Natural Disaster impact? • Drought? (if a drought happens in the central US for 8 years or so, does the effect not depend on how much agriculture is effected?) • High rainfall? DENSITY DEPENDENT Non-living Living ABIOTIC FACTORS BIOTIC FACTORS Whether or not population matters • Weather • Climate • Natural Disaster • Flash flood • Fires • Earthquake • Drought • High rainfall - Human impact: Clear cutting, Deforestation Genetic disease Hunting DENSITY INDEPENDENT

34. What’s Limits Population Growth? • Population growth takes many forms; can keep growing, usually slows, may stabilize, or even crash. • …due to increased competition as demand for density-dependent factors increases. • This illustrates an ecosystem can support only so many organisms due to limited DENSITY DEPENDENT FACTORS. • Whatever the case, the largest population that an environment can sustain (support for long periods of time) at any given time is called the carrying capacity. • When the carrying capacity of an ecosystem is reached, one characteristic exists… • death rate (& other negatives) equals the birthrate (& other positives) = ZERO GROWTH over extended periods. • But the question is, how to determine (K)? (K) • Natural populations usually fluctuate as they stabilize around the carrying capacity of the environment and reach a balance between the organisms and the resources in the area.

35. Bacterial Growth curve. Incubated in a nutrient-rick medium: An isolated ecosystem. What is (K)? (K)? (K)? (K)?

36. Case Study: Lesson of the Kaibab • You are going to go through this process again, but independently, using a classic case study, the deer of the Kaibab National Forest in Northern Arizona. • Working together with a partner • 1. Construct your graph of the Kaibab deer • STALK your graph. What does this mean? • Analyze the data • Part of your grade will be a properly constructed graph. • 2. Draw conclusions from this. • Complete sentences. • Think and apply the concepts we discussed in class. • Ask questions as needed. • Due Monday. 25pt Lab.

37. Kaibab Deer Population (1905-1939) • Scale = 6000 deer per line. Deer Population (x1000) 0 6 12 18 24 30 36 42 48 54 60 66 72 78 84 90 96 102 • │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ ││ │ (K)Deer = determine by ecologists │ │ │ │ │ │ │ │ 1905 1910 1915 1920 1925 1930 1935 1940 Time (Years) Scale = 1 year per line.

38. Question: Are populations independent? • What does this mean, “independent”? • It means that two or more variables do not have an impact on each other. • Do you think two or more species will impact each other? • How and Why? • One goal is to be able to understand how this interaction can be illustrated graphically and what they allows us to conclude, so we can defend claims that one population impacts another. • Let’s look at a simulation, Predator-Prey. • The goal here is to illustrate how populations could theoretically be shown to interact.

39. Summary • EQ: How do we determine if a population is effected? • Populations = same species, same place, same time (frame) • Ecologists study population change over time to identify cause and effects of the relationships between organisms or organisms and their environments. • Growth is the quality of population change (over time). • Can be positive, negative, or stable (no growth) • Growth is calculated = [Births + Immigration] – [Deaths + Emigration] • Growth typically falls into growth models; linear, exponential, or logistic. • Factors influence births, deaths, immigration, and emigration. • These can be abiotic, biotic, density-dependent, or density-independent. • Understanding these dynamics helps us understand our impacts and influences or decision-making.

41. Practice Analysis • Is this graph reliable? What’s up with the graph? Where did we get the data? • What does the y axis on the left represent? What does the y axis on the right represent? • Why would we graph both together? • For both y axes, what value do the numbers on the axes need to be multiplied by in order to represent the real population? (for example, “80” on the hare graph really means what?) • What is the approximate population of snowshoe hares in 1865? • What is the approximate population of lynx in 1865? • What is (k) for hares? (label it) • What is (k) for lynx? (label it) • What kind of population growth is displayed in the graph & why? (linear, exponential, logistic) • On average, what was the period of oscillation (the time it takes to rise and fall) of the lynx population? • On average, what was the period of oscillation of the hare population? • On average, do the peaks of the predator population match or slightly precede or slightly lag those of the prey population? If they don't match, by how much do they differ? (Measure the difference, if any, as a fraction of the average period.) • Does the graph show that there is a relationship between lynx and hare? How do you know? • What is meant by “pure” predator-prey interactions? • What does this type of exercise help us do in ecosystems? For example, what should we think if we saw 35,000 lynx or 500 hare? Anything else?

42. Deer Population (1930-1985) 3. Density-dependent 4. Too many deer for the ecosystem to support: competition likely increased– though we don’t know for sure. The population was able to grow past what the ecosystem could support because the deer didn’t immediately die. Population of Deer (Individuals) 0 50 100 150 200 250 300 2. Sustain? 6. Carrying capacity (K) = about 200 deer 1. Logistic Growth 5. As the population shrank (negative growth), competition likely decreased and resources likely became more numerous – though we don’t know for sure. Once survivors were able to have offspring the population went back up. In 2019, we’d expect to find roughly 200 deer here. If we didn’t, we’d know there’s some other factors impacting this population. More ?s Need exploration. • ’40 ’50 ’60 ’70 ’80 ‘90 TIME (Year)

43. Populations. REcap • Your goal is to answer the EQ: How do we know if a population is being impacted or effected? • To answer that: • We’ve defined what a population is Population = Counted by various techniques, sampling, tagging, etc. • We’ve illustrated that we use growth to determine how populations can be effected; either positively, negatively, or stabilized. • We’ve quantified change in population (known as GROWTH) as evidence for an effect by using the equation… GROWTH (how to know is it’s effected) = Population 2 – Population 1… = Population Change = (Births + Immigration) – (Deaths + Emigration) • We’ve examined how to determine positive and negative growth and the factors (biotic, abiotic, density dependent, or density independent) that influence positives and negatives and • Factors that become significant as populations grow.

44. Populations. REcap • Your goal is to answer the EQ: How do we know if a population is being impacted or effected? • To answer that: • We’ve also examined population growth models to determine the basic types, trends that we see in growth • Linear, exponential, logistic • We’ve plotted and analyzed • Single-population growth models (Deer) • Natural single population growth (Kaibab Deer) • Simulated 2-species interconnected growth (Predator-Prey Simulation) • Natural 2-species interconnected growth (Hudson Bay Lynx-Hare) • We’ve seen how population growth models are used to estimate CARRYING CAPACITY and how (K) can be used to establish if a population size has changed from normal or sustainable.

45. Populations. The last step • Your goal is to answer the EQ: How do we know if a population is being impacted or effected? • Why “we” in the general public care about this is for one primary reason. • Though there may be more. • We should want to know what evidence is there that would suggest human activity is affecting natural populations. • Evidence of this should probably be best used to inform our personal decisions to minimize any additional negative impact we might be having. • The last step in examining population growth is to analyze human growth and see what growth models exist to help us understand • What does human growth (or at least what we know about it) look like? • How do the lessons of other natural populations teach us what dangers we might want to consider as our populations grow?

46. Human Population Growth Models • Human Population Growth: What you should get out of this activity. • Graph human growth to determine what the human growth model looks like. • Compare human growth to other population growth models. • Understand the reasons why human growth looks like it does. • Make predictions on… • What is the earth’s (K) for humans? • What becomes more impactful as human population increases? • You will also break down human growth a little by country to identify: • Is human population growth equal across all countries? • Why? • Why does this matter? • Due Block Day (40pts HW). Work independently and try to complete as much as you can today. You will have a lengthy Warm Up tomorrow and will be quizzed on this block day. Be prepared to answer questions. • Online, you will find some additional resources (like this ppt.) on the subject of population growth and a more thorough explanation of population pyramids that I encourage you to look into.

47. What About Our Growth? • Compare these graphs. • The top is a normal growth curve. • The middle is the growth curve for recorded human history. • The bottom is that of a bacterial infection. • What is similar? • What is different? • What is concerning? • We haven’t really reached our carrying capacity yet. • In any event, it’s important to consider the causes and effects of population growth. What happens in bacterial growth when they grow beyond their environment’s capability to sustain them

48. Human Population Growth E. ASIA & PACIFIC • The population of all humans is indeed growing. • In this class alone, there has been hundreds of new humans added to the Earth. • But, is growth occurring at the same rate around the world? • Where should our concerns and efforts be placed? • What are the causes and effects? N. AMERICA

49. Population Pyramids • To breakdown population growth into more specific terms we can use population pyramids to see where exactly the growth is occurring. • Population pyramids break down populations by age and sex by region to see exactly how these pieces of data compare to other regions. • They can indicate whether or not a population is growing, shrinking or stabilized and help us determine where our focus should be. • Population of a Stable Country • Factors to consider: • Everyone will die but what is the oldest age achieved and how many live to see old age? • The middle-aged people are the one who have children. How many children are being born? • Children will soon grow to reproductive age, contributing to the population growth if trends continue.

50. Population Pyramids • To use population pyramids you need to understand how they’re built and what they mean for the future. • Which country is stable? • Which country should experience rapid growth? Indication of life spans Parents having more babies than parents. Babies eventually grow to have babies.