1. Topic 2: Ecosystems and Ecology
2.1 Species and Populations

2. Significant Ideas
A species interacts with its abiotic and biotic environment, and its niche is described by these interactions.
Populations change and respond to interactions with the environment.
All systems have a carrying capacity for a given species

3. Application and Skills
►Interpret graphical representations or models of factors that affect an organism’s niche. Examples include: prey-predator relationships; competition; and organism abundance over time. ►Explain population growth curves in terms of numbers and rates.

4. Knowledge & Understanding
A species is a group of organisms that interbreed and produce fertile offspring. Species share common characteristics.
A habitat is the environment in which a species normally lives.
A niche describes the particular set of abiotic and biotic conditions and resources to which an organism or population responds.
The fundamental niche describes the full range of conditions and resources in which a species could survive and reproduce. The realized niche describes the actual conditions and resources in which a species exists due to biotic interactions.
The non-living, physical factors that influence the organisms and ecosystems (temperature, sunlight, pH, salinity, precipitation) are termed abiotic factors.

5. Knowledge & Understanding
The interactions between the organisms (predation, herbivory, parasitism, mutualism, disease, competition) are termed biotic factors.
Interactions should be understood in terms of the influences each species has on the population dynamics of others, and upon the carrying capacity of the others’ environment.
A population is a group of organisms of the same species living in the same area at the same time, and which are capable of interbreeding.
S and J population curves describe a generalized response of populations to a particular set of conditions (abiotic and biotic factors).
Limiting factors will slow population growth as it approaches the carrying capacity of a system.

6. Tips Use named examples to illustrate concepts or arguments.
Always give the full name of the animal or plant your are mentioning, for example say, ‘Atlantic Salmon’ instead of ‘fish.’
Whey you use a habitat or local ecosystem as an example, give as much detail as possible, for example not ‘beach’ but ‘rocky shore, north-facing, at Robin Hood’s Bay, North Yorkshire, UK’.

7. Ecology
The study of the relationships between living organisms (biotic environment) and between organisms and their physical (abiotic) environment.
The word ecology is derived from the word ‘oikos’ or home. Ecology is the study of the (our) home.
The word ‘environment’ refers to everything which surrounds an organism. The environment includes:
The Hydrosphere: Water
The Atmosphere: Gases
The Lithosphere: Rocks
The Biosphere: All Living Things

8. Terrestrial (Land) Ecosystems
Key Abiotic Factors
Terrestrial (Land) Ecosystems
Sunlight, Water, Wind, Disturbances, Soil, Temperature, Gases, Humidity, Nutrients, Minerals, Climate.
Aquatic Ecosystems
Temperature, Water Quality/Salinity, Light Penetration, Dissolved Gases, Minerals, Nutrient Availability all determine where organisms can live in the water.

9. The study of ecology includes various levels of organization and complexity
Species: a group of organisms sharing common characteristics that can normally interbreed and produce fertile offspring. Population: a group of organisms of the same species living in the same area at the same time, and which are capable of interbreeding. Ecosystem: A community AND its abiotic (non-living) environment.

10. How is a Species Name Different From a Common Name?
The scientific name contains two parts:
The genus name (1st letter of the word capitalized).
Epithet (2nd name – not capitalized).
The scientific name (species) includes both the genus and epithet names.

11. Habitat vs. Niche How much space there is.
While a habitat is the environment in which a species normally lives, a niche is how an organism makes a living (its role). Any habitat contains a number of niches.
(Explanatory Video)
A niche includes:
Biotic Factors
Relationships the organism may have with other organisms.
How it responds to available resources, to predators, and to competition.
How the organism alters its environment.
Abiotic Factors
How much space there is.
Availability of light, water, nutrients, etc.
The competitive exclusion principle states that no two organisms can inhabit the same ecological niche in the same place at the same time and compete for the same resource.

12. Population Interactions
A Biological Community is a group of interacting populations living in the same area at the same time.
All organisms in an ecosystem compete (directly or indirectly) with other organisms.
Interactions between organisms include intraspecific competition and interspecific competition.
1. Intraspecific Competition: Between members of the same
species.
2. Interspecific Competition: Competition between members
of different species.

15. Fundamental vs. Realized Niche

16. Interspecific Competition
Competition (-/-) is a form of negative feedback that can stabilize population numbers and keep populations in check.
Examples of Interspecific Competition Include:
Predation: One animal (predator) eats another (prey). (+/-)
Herbivory: An animal eating a plant. (+/-).
Parasitism: One species lives in/on another. (+/-)
Mutualism: Both species benefit. (+/+)
Commensalism: One species benefits while the other is neither helped nor harmed. (+/0)

17. Symbiotic Relationships Among Organisms
(Close relationship between two or more organisms)
Symbiotic
Relationships
Commensalism
(+/0)
Mutualism
(+/+)
Parasitism
(+/-)

18. Commensalism (+/0)
The shrimp is immune to the stinging tentacles of the sea anemone. By hiding in the sea anemone, the shrimp is protected from predators.

19. Mutualism (+/+) Crocodile and Egyptian Plover
Green alga and fungus (lichen)
A green alga and fungus are dependent on each other. The fungus gains nutrients synthesized from the alga, and the alga receives water and nutrient salts from the fungus.
Crocodile and Egyptian Plover
The Egyptian plover feeds on leeches and other scraps of food in the crocodile's mouth. The crocodile benefits because the plover cleans its teeth.

20. Rhizobium Bacteria and Soybean Plant
The bacteria found on the roots of a soybean plant fix atmospheric nitrogen and make it available to the plant. The bacteria receives carbohydrates from the plant.

21. Focus on Parasitism (+/-)

22. Mind-Control Parasites

23. Population Dynamics
Population: A group of individual of the same species living in a defined area that have the potential to interbreed and produce fertile offspring.

24. Quick Definitions
Population: Members of the same species living in the same area at the same time.
Population Density: The # of organisms per unit area (ex. People per km2).
The study of human population size, density, distribution, movement, and birth and death rates is demography

25. In ecosystems, population sizes fluctuate (change) over time for a variety of reasons: 1. Natality: Birth Rate 2. Mortality: Death Rate 3. Immigration: Members arriving from other places. 4. Emigration: Members leave the population.

26. Density Independent vs. Dependent Variables
Density independent and Density dependent variables can affect population sizes in addition to the aforementioned factors.
What’s the difference?
Density Independent Factors: factors like drought, fire, intense weather, hurricanes, etc. that will reduce population size independent of population density.
Density Dependent Factors: factors like competition, disease, predation, and parasitism that tend to increase with increasing populations numbers.

27. Mount Saint Helens Eruption – 1980

28. Then & Now

30. S-Shaped Growth Curve
The Exponential or Logarithmic Growth Phase: The number of individuals increases at a faster and faster rate. Causes:
Abundant food, space, or light.
Little or no competition for resources.
Favorable abiotic factors like temperature or dissolved oxygen levels.
Little or no predation or disease.
The Transitional Phase: The growth rate slows down considerably—the population is still increasing but at a slower and slower rate. Causes:
More individuals means more competition for resources, limited space, faster spread of disease.
More individuals means more predators.
The Plateau or Stationary Phase: The number of individuals has stabilized—there is no more growth. Causes:
Predators and disease increase mortality.
Food supply is limited so organisms have fewer offspring.
The number of births + immigrations is balanced with the number of deaths + number of emigrations.

31. An illustration of the power of exponential growth
Brain Teaser
An illustration of the power of exponential growth

32. Exponential Growth

33. Human Population Growth

34. Human Population Calculator & (What’s Your Number?)

35. Carrying Capacity (K)
Populations cannot continue to grow and grow forever. Population numbers will eventually stabilize. Carrying Capacity (K): The maximum number of individuals that a particular habitat can support.

36. Limiting Factors: Those factors in an environment/ ecosystem that set limits to population growth.
Examples of limiting factors for ANIMAL populations
Food availability
Availability of mating partners
Presence of parasites and/or disease
Predation and competition
Available space (nesting, breeding, feeding, etc.)
Examples of limiting factors for PLANT populations
Light Intensity
Temperature
Carbon dioxide levels
Nutrient availability
Predation

37. The Curious Case of the Lemmings