Populations and Communities

1. Populations and Communities Organisms interacting with each other in many ways.

2. Ecology is the study of interactions between organisms and their environments. This unit will focus on: • Populations • Communities

3. Unit 10: Concepts • Populations (E) • Communities (E) • Terrestrial and aquatic biomes (I)

4. Essential question 1.1: How do changes in size, density and dispersion affect the health of a population?

5. A population is defined as all the individuals of a species that live together in one place at one time. • The humans in Mechanicsburg in 2001. • The bacteria in your colon during adolescence. • The grass on your front lawn this summer.

6. Ecologists study three key features of populations • Population Size • Population Density and Distribution • Population Growth

7. Population size is the number of individuals in a population. • Large populations are more stable since small populations may be easily affected by the environment and the mechanisms of evolution due a lack of variety in the gene pool. • If environmental conditions fluctuate, large populations with a lot of variation are easily adaptable. • In small populations, inbreeding causes a disproportionate increase in unfavorable characteristics.

8. Population density is the number of individuals that live in a given area. • Defined as: “one mountain lion per square mile” • Being spread out may be good or bad. • This can be used to determine a species health. • This is generally determined by random sampling.

9. Dispersionis the way that individuals of a population are arranged in space. • Clumped • Even spacing • Random

10. Question: Identify at least one example for each of the three population dispersions. Random: Maple trees (or any wind dispersed plant). Even Spacing: Mountain lions maintaining a specific range (Or any large predator). Clumped: A herd of Buffalo (Or any herd animal).

11. Essential question 1.2: How do ecologists calculate rates of change in populations?

12. Models are used to explain how a population grows. • A population model is a hypothetical population that attempts to exhibit the characteristics of a real population. • The models are built mathematically, often using a computer simulation. • The model may be manipulated to study the effects of a change. • The more data that are include, the more predicative the model will become. Click to view model live Image captured 9/11/11 11am

13. There are several key variables to consider when attempting to model the growth rate of a population. • Natality - birth rate • Mortality - death rate • Immigration - individuals entering population • Emigration - individuals leaving the population

14. If resources are unlimited, a population should grow exponentially.

15. In reality, resources ARE limited so exponential growth is not sustainable in nature. Factors affecting population growth

16. DENSITY-DEPENDENT FACTORS • Density-dependent factors are regulated by the density of a population. • As population size increases, density-dependent factors become a problem. • Growth rate will slow when a population reaches it’s carrying capacity. • Carrying capacity is defined as the maximum sustainable number of individuals that the ecosystem can support. • If a population exceeds its carrying capacity, the population size will decrease as density-dependent factors limit survival. • This type of growth is called logistical growth. • Some density-dependent factors: • Competition for food, shelter, and mating sites • Accumulation of wastes • Parasites • Disease

17. K-strategists live in very stable environments. Because K-strategists live in stable environments, they are able to exist in populations that are near their carrying capacity.They posses characteristics such as: • Slow generation time. • Reproduce late, and in small numbers. • High degree of parental care. • Long living organisms like whales and gorillas.

18. Logistic growth curve Beginning growth Rapid growth Growth slows Carrying capacity Fluctuations 5. 4. 3. 2. 1.

20. Question: What’s in store for the human population? • Scientists had predicted 12 billion people by 2030. • Since HIV has become a major global killer, and consequently and important limiting factor, current projections show a continued increase of population (but a steady decline in the population growth rate) with the population to reach between 7.5 and 10.5 billion by the year 2050.

21. DENSITY-INDEPENDENT FACTORS • Density-independent factors like weather and climate limit many populations from approaching their carrying capacity. • r-strategistslive in rapidly changing environments. They reproduce rapidly when conditions are favorable, then die back to reasonable levels as conditions worsen. To compensate for these limitations, r-strategists possess certain characteristics: • Quick generation time. • Reproduce early, and prolifically (with many young). • Little to no parental care. • Examples: insects, weeds and other pests.

22. The effect of weather (density independent) on an Aphid population

23. Question: Are humans r-strategists or K-strategists? Humans are K-strategist animals that are growing like r-strategists. At some point in the near future, we will witness a sharp decline in the human population.

25. Sustainable human population projections Population estimates vary for both peak and sustainable populations depending on consumptions levels and climate change.

26. Question: Which population has the biggest potential for growth in years to come? Question 2: Which country has higher natality? Mortality ? What accounts for these differences?

27. Population Growth Histograms What do these histograms indicate about future growth rate?

28. Demographic Transition - Industrialization

29. Unit 10: Concepts • Populations (E) • Communities (E) Unit 10 Test

30. Essential question 2.1: How are symbiotic relationships important in biological communities?

31. Communities Two or more interacting species in a defined habitat constitute a community. • An example of a community can be witnessed on the island of Isle Royale, Lake Superior Michigan. • Vegetation provides cover and food for birds. • Moose feed on trees changing the vegetation. • Wolves prey on Moose. • Fox scavenge of remaining carcasses • Ticks infest Moose and Wolves.

32. Communities Species can interact with each other in three main ways: • Competition • Predation • Symbiosis

33. Competition Competitionis the ecological interaction in which individuals compete for resources in the same habitat. Interspecific competitionCompetitionfor shared resources between two or more different species. (food, sunlight, living space, etc.) Intraspecific competitionCompetition for shared resources between individuals of the same species. (food, space, mate, sunlight, etc.)

34. Predation • Predation occurs when one organism kills and eats another organism. • Predator-Prey relationships come about through co-evolution. Very often, both species benefit from the relationship.

35. Question: Why do predators and prey need each other? Predators need the prey as their food source. Without plentiful numbers, their population will decline. Prey need predators to keep their number limited. If unlimited growth occurs, the species will die back as resources are devoured.

36. Question: How is the coevolution of predators and prey similar to the Cold War between the United States and Russia? Biologists have often described the coevolution of predators and their prey as an “arms race”. During the Cold War, the U.S. and Russia competed in an arms race that saw them consistently attempt to gain an advantage over the other by developing newer, more powerful weapons.

38. Coevolution occurs when two different organisms make the back-and-forth adjustments necessary to continue their relationship.

39. Activator • While walking his dog this morning, Mr. Brown saw this animal crossing the street. The coyote was half way between Mr. Brown and five high school students waiting for the bus. Squirrels were playing on the ground and a groundhog was munching on some grass nearby. • You have 3 minutes to write what happens next in this story and you must use either competition or predation in your story.

40. Activator • While walking his dog this morning, Mr. Brown saw this animal crossing the street. The coyote was half way between Mr. Brown and five high school students waiting for the bus. Squirrels were playing on the ground and a groundhog was munching on some grass nearby. • How could you edit the story to include cooperation for survival?

41. Symbioticrelationshipsexist when organisms live in close proximity for their entire lives. There are 3 types of symbiotic relationships that we will focus on in this unit. • Mutualism • Commensalism • Parasitism

42. Mutualism occurs when both organisms benefit.

43. Commensalismoccurs when one organism benefits and the other is neither harmed nor helped (Dung beetles and elephants).

44. Parasitismoccurs when one organism benefitswhile it hurts the other (Ticks and you!).

45. Practice time… • Get a laptop and go to the following website: https://bit.ly/2Csi8MX • Once there, select one of the six videos that begin with “Symbiosis.” While watching, determine which symbiotic relationship is represented. • Then, record the details of your example in the appropriate location on your organizer.

46. Give one – Get one • When you have finished watching your video clip and have gathered the details for your example, find a classmate for each of the two remaining symbiotic relationships that you are missing. • Share and discuss your video clips and record the details on your organizer. • When you have all three symbiotic relationships accounted for, return to your seats and work in your unit guide on pages 19-21. • .

47. Your turn… • Return to the website you used to select your video example. https://bit.ly/2Csi8MX • Watch the video clip “Summarizer - Leaf Cutter Ants Symbiotic Relationships” • While watching, answer the questions and record the interactions between each of the species involved in this ecological relationship. • When finished, label the diagram at the end of the organizer with each of the ecological relationships demonstrated in the video.

48. Summarize • You have five minutes to list the three types of symbiotic relationships you learned today, describe an example for each that is found in the leafcutter ant video clip, and explain why that example represents the symbiotic relationship that you identified. • This will be collected at the end of class and will count for a 3 point quiz grade so do your best work!

49. Leaf cutter ants harvest leaves and feed them to colonies of fungus that produce a useful food resource. • Leaves are mulched and used to grow “fields” of fungi. • The fungi in turn produce specialized hyphal tips called gongylidia which the ants consume and feed to their larvae • A third layer of symbiosis exists, as colonies of bacteria on the ants bodies provide protection from mold infections that might harm the ants “crops” • This form of agriculture developed long before the first human farmers sowed their first seeds. • The needs of both the ants and the fungi are so specific that neither can survive without the other.

50. Essential question 2.2: How is the niche of an organism related to the other organisms in the community?