1. Comparison of Growth Curves
Exponential population growth results in a J-shaped curve. The J-shaped curve of exponential growth characterizes some rebounding populations. For example, the elephant population in Kruger National Park, South Africa, grew exponentially after hunting was banned. The logistic model describes how a population grows more slowly as it nears its carrying capacity. Exponential growth cannot be sustained for long in any given population.
The logistic model of population growth produces a sigmoid (S-shaped) curve. A more realistic population model limits growth by incorporating carrying capacity. Carrying capacity (K) is the maximum population size the environment can support. Carrying capacity varies with the abundance of limiting resources. This figure shows population growth predicted by the logistic model. The growth of laboratory populations of paramecia fits an S-shaped curve. These organisms are grown in a constant environment lacking predators and competitors.

2. Population Reproductive Strategies
r-selected (opportunistic)
Short maturation & lifespan
Many (small) offspring; usually 1 (early) reproduction;
No parental care
High death rate
K-selected (equilibrial)
Long maturation & lifespan
Few (large) offspring; usually several (late) reproductions
Extensive parental care
Low death rate
Emphasize that these r-selected and opportunistic are synonyms as are K- selected and equilibrial. It’s the synonyms that will give students fits when they are reading and interpreting test questions!

3. How Well Do These Organisms Fit the Logistic Growth Model?
Have students examine the graph of Paramecium. What is the carrying capacity of the population in the lab? About 900.
How long does it take the Paramecium to reach K? About 10 days.
Have students examine the graph of the Daphnia.
What is the carrying capacity of the population in the lab? About 90.
How long does it take the Paramecium to reach K? About 135 days.
Some populations overshoot K before settling down to a relatively stable density
Some populations fluctuate greatly and make it difficult to define K

4. Age Structure Diagrams: Always Examine The Base Before Making Predictions About The Future Of The Population
Rapid growth
Afghanistan
Slow growth
United States
No growth
Italy
Male
Female
Age
85+
80–84
75–79
70–74
65–69
60–64
55–59
50–54
45–49
40–44
35–39
30–34
25–29
20–24
15–19
10–14
5–9
0–4
Male
Female
Age
85+
80–84
75–79
70–74
65–69
60–64
55–59
50–54
45–49
40–44
35–39
30–34
25–29
20–24
15–19
10–14
5–9
0–4
Male
Female
Age-structure pyramids for the human population of three countries (data as of 2009). Emphasize to students that they should start their analysis at the BASE of these diagrams since that represents the most current population. Also emphasize they respect the vertical line on these diagrams that delineate male vs. female. Briefly explain why the predictions above each graph are likely to hold true. 10 8 6 4 2 2 4 6 8 10 8 6 4 2 2 4 6 8 8 6 4 2 2 4 6 8
Percent of population
Percent of population
Percent of population 4

5. Natural Selection
This includes describing how organisms respond to the environment and how organisms are distributed.
Events that occur in the framework of ecological time (minutes, months, years) translate into effects over the longer scale of evolutionary time (decades, centuries, millennia, and longer).
LO 1.2 The student is able to evaluate evidence provided by data to qualitatively and quantitatively investigate the role of natural selection in evolution
SP 2.2 The student can apply mathematical routines to quantities that describe natural phenomena
SP 5.3The student can evaluate the evidence provided by data sets in relations to a particular scientific question

6. of the species involved
Community Ecology
Ask students to cite examples of what they think would be classified as interspecific interactions. Possible answers include: competition, predation, herbivory, symbiosis (parasitism, mutualism and commensalism), and facilitation. Throughout this discussion, we’ll use + and − to indicate how each interaction affect the survival AND reproduction of the two interacting species. For each of the interactions students come up with ask them to apply the +/− to each interaction.
Populations are linked by interspecific interactions that impact the survival & reproduction
of the species involved

7. Community Structure
Community−an assemblage of populations living close enough together for potential interaction
Dominant Species−most abundant, highest biomass, powerful control over occurrence and distribution of other species… VA Sugar Maple
Keystone Species−NOT necessarily most abundant, exert strong control due to their ecological roles or niches… Sea Otters!!!
Richness number of species & abundance
Species diversity older = greater diversity larger areas = greater diversity climate = solar input & H2O available
Dominant species are exerting powerful control over occurrence and distribution of other species. They are the most abundant or have the highest biomass. Have students suggest WHY one species dominates an ecological community. Plausible hypotheses include: are competitive in exploiting resources OR are most successful at avoiding predation among others.
Keystone species are not necessarily the most abundant, but exert strong control over communities due to their ecological roles or niche.

8. Biodiversity Communities with higher diversity are
More productive and more stable regarding their productivity
Better able to withstand and recover from environmental stresses
More resistant to invasive species, organisms that become established outside their native range
LO 4.21 The student is able to predict consequences of human actions on both local and global ecosystems.
Ask students to first identify some “human actions” that affect ecosystems. Possible answers will most likely include pollution of all sorts or destruction of habitat such as deforestation or damage to coral reefs. Once students identify a “human action”, have them predict and explain the consequences of the human action.

9. Sample Data
The data below represents the abundance of macro-invertebrates taken from three different river communities in Georgia. A variety of diversity indices may be used to calculate species diversity. Based on the data below, which community has the greatest diversity?
LO 4.21 The student is able to predict consequences of human actions on both local and global ecosystems.
Species diversity is related to both species richness and relative abundance. Species richness is the number of different species in the community and relative abundance is the proportion each species represents of all individuals in the community.
Answer: Community A has more species than either communities B or C. Community B is more abundant in leeches, but has no water penny. Community C only has two species, thus is low with regard to species richness.

10. Indirect Effect on the Community
A keystone species is one that has a strong effect on the composition of the community
Removal of keystone species causes a decrease in species richness
Sea otters eat sea urchins which are fierce competitors having a diet of kelp
Sea otters and the kelp forest ecosystem have a strong relationship with one another. The strength or robustness of one, often influences the productivity of the other. Often then, are sea otters considered a keystone species, an important species vital to the overall health of ecosystems. ASLC collaborators are currently investigating the benthic invertebrate communities to better understand the overall ecosystem health and how it relates to otter populations in the Aleutian and Commander Island chains.

11. Sea Urchin Population vs. Kelp Density
Ask students to examine and interpret the data shown.
When the otters are removed from the community, their main prey, the sea urchin is able to expand their population. Sea urchins are predators of Kelp. The graph above shows the impact on the community when otters are removed. The kelp population is essentially depleted since the sea urchins are unchecked in the community.

12. Factors that Impact Communities
1. Disease
2. Interspecific Interactions:
Competition
Predation
Symbiosis
Mutualism − mycorrhizae
Commensalism
Ask students to use the +/- notation with regard to the bullets on this slide.
Disease -/-
Interspecific Interactions: Competition +/- Predation +/-
Symbiosis: Mutualism − mycorrhizae +/+ (is a symbiotic (generally mutualistic, but occasionally weakly pathogenic) association between a fungus and the roots of a vascular plant) AND Commensalism +/0

13. Defense Mechanisms
Mullerian-Two or more unpalatable, aposematically colored species resemble each other
Batesian-palatable/ harmless species mimics an unpalatable/ harmful model
Cryptic-camouflage
Aposematic-warning
Cryptic Coloration: -camouflage Aposematic-warning
Mimicry superficial resemblance to another species
Mimicry: Batesian-palatable/ harmless species mimics an unpalatable/ harmful model
Mullerian-Two or more unpalatable, aposematically colored species resemble each other

14. Ecological Niches
An organism’s niche is the specific role it plays in its environment…its job!
All of its uses of biotic and abiotic resources in its environment
Ex: oak tree in a deciduous forest
Provides oxygen to plants, animals
Provides a home for squirrels
Provides a nesting ground for blue jays
Removes water from the soil
Ecological niche is a term describing the way of life of a species. Each species is thought to have a separate, unique niche. The ecological niche describes how an organism or population responds to the distribution of resources and competitors (e.g., by growing when resources are abundant, and when predators, parasites and pathogens are scarce) and how it in turn alters those same factors (e.g., limiting access to resources by other organisms, acting as a food source for predators and a consumer of prey).

15. Ex: Barnacle species on the coast of Scotland
The Niche
Ecological niche is the total of an organism’s use of biotic and abiotic resources in its environment
Ex: Barnacle species on the coast of Scotland

16. Competitive Exclusion Principle
Sometimes referred to as Gause's law of competitive exclusion states that two species competing for the same resources cannot coexist if other ecological factors are constant.
The competing species that has even the slightest advantage will dominate in the long term and emerge the victor.
The loser will either relocate or become extinct.
The principle has been paraphrased as "complete competitors cannot coexist".
The competitive exclusion principle, sometimes referred to as Gause's law of competitive exclusion or just Gause's law, is a proposition which states that two species competing for the same resources cannot coexist if other ecological factors are constant. When one species has even the slightest advantage or edge over another, then the one with the advantage will dominate in the long term. One of the two competitors will always overcome the other, leading to either the extinction of this competitor or an evolutionary or behavioral shift towards a different ecological niche. The principle has been paraphrased into the maxim "complete competitors cannot coexist".

17. Succession Pioneer organisms = bacteria, lichen, algae
Ecological succession− transition in species composition over ecological time
Pioneer organisms = bacteria, lichen, algae
Climax community = stable
Primary− begun in lifeless area; no soil, perhaps volcanic activity or retreating glacier.
Secondary an existing community has been cleared by some disturbance that leaves the soil intact
The pictures are of Yellowstone Park – on the left after the fires of 1988 and on the right the exact same area after recovering through the process of secondary succession a year later.
Common Misconception- “fire is bad” (it is a natural phenomena in nature). As a matter of fact when this fire started in 1988, the rangers told visitors that it was their policy not to put out fires in the park. The fire expanded through Yellowstone more than they anticipated and by the end of the summer, they began working to put the fire out.
Suggestion: The Succession Game

18. Human Impact on Ecosystems
Humans are the most widespread agents of disturbance
Reduces diversity
Prevent some naturally occurring disturbances

19. Human Impact on Ecosystems
Combustion of Fossil Fuels
Leads to acid precipitation
Changes the pH of aquatic ecosystems and affects the soil chemistry of terrestrial ecosystems
Chemical compounds that are nonmetal oxides react with water to form acids and are called acid anhydrides. The generic formula for such compounds are COx , SOx , NOx, and POx. When these compounds are expelled as exhaust from automobile or industrial sources, they react with water in the atmosphere and make acid rain. All of the acids formed are “weak” acids (don’t completely dissociate in water), but cause much damage none the less.