1. Interactions in ecosystems

2. habitat
Combined biotic and abiotic factors found in the area where an organism lives

3. Ecological niche
All of the physical, chemical, and biological factors that a species needs to survive, stay healthy, and reproduce in an ecosystem
Food
Abiotic factors
Behavior
The physical characteristics of the area where the species lives
Size
Location
Temperature pH
The function of the species in the biological community

4. Fundamental Niche
The largest ecological niche where an organism or species can live without competition

5. Realized Niche
As a result of competition in the species’ fundamental niche, a realized niche is the:
Range of resources that a species uses
Conditions that the species can tolerate
Functional roles that the species plays

6. Competitive exclusion
Theory that states that no two species can occupy the same niche at the same time
Niche partitioning: two species naturally divide different resources based on competitive advantages
Evolutionary response: two species may have experienced divergent evolution

7. Competitive Exclusion
The exclusion of one species by another due to competition
When can competitors coexist?
If they use a realized niche as opposed to a fundamental niche

8. Realized Niche/Fundamental Niche
2 species of barnacles that grow on the same rocks on the coast of Scotland
Chthamalus stellatus lives in shallow water, exposed to receding tides
Semibalanus balanoides lives lower down on the rocks, rarely exposed to the atmosphere
When Semibalanus is removed from the deeper zone, Chthamalus occupies the vacant surfaces
Chthamalus’ fundamental niche includes the deeper zone
When Semibalanus was reintroduced, it out-competed Chthamalus for the deeper zone
Semibalanus, in contrast, could not survive in the shallow-water habitats when Chthamalus was removed
Competition can limit how a species uses its resources

9. Realized Niche/Fundamental Niche

10. Ecological equivalents
Organisms that share a similar niche but live in different geographical regions

11. Competition & predation are two important ways in which organisms interact

12. Competition
The relationship between species that attempt to use the same limited resource
Resources often competed over:
Food
Nesting sites
Living space
Light
Mineral nutrients
Water

13. predation
Process by which one organism hunts and kills another organism for food

14. Symbiosis
Ecological relationship between members of at least two different species that live in direct contact with one another

15. Symbiosis: Mutualism
A relationship between two species in which both species benefit
Example: ants and aphids
Aphids give ants food
Ants give aphids protection from predators

16. Symbiosis: Commensalism
A relationship between two organisms in which one organism benefits and the other is neither harmed nor helped
Example: tropical fishes and sea anemones
Fish are protected
Anemone is neither harmed nor helped

17. Symbiosis: Parasitism
One organism feeds on and usually lives on or in another, typically larger organism
Do not usually kill their prey (“host”)
Depend on the host for food and a place to live
Host often serves to transmit the parasite’s offspring to new hosts

18. Symbiotic relationships

19. Population Density
The number of individuals of the same species that live in a given unit of area
If the individuals of a population are few and are spaced widely apart, they may seldom encounter one another, making reproduction rare

20. Geographic dispersion of a population shows how individuals in a population are spaced

21. Survivorship curves help to describe the reproductive strategy of a species
Type I
Common in large mammals
Low infant mortality
Many survive to old age
Parental care
Type II
Reptiles (including birds), small mammals
At all times species have equal chance for living and dying
Type III
Invertebrates, fishes, amphibians, plants
High infant mortality
Few survive to adulthood

22. r-strategists
A species that is adapted for living in an environment where changes are rapid and unpredictable; characterized by:
Rapid growth
High fertility
Short life span
Small body size
Exponential population growth
Example: insects

23. k-strategists A species characterized by:
Slow maturation
Few young
Slow population growth
Reproduction late in life
Population density near the carrying capacity of the environment
Examples: bears, elephants, humans

24. Population growth patterns

25. Changes in a population’s size are determined by…
Immigration
Births
Emigration
Deaths

26. Population growth is based on available resources

27. Population Model Hypothetical model of the population
Attempts to exhibit the key characteristics of a real population
By making a change in the model and observing the outcome, demographers can predict what might occur in a real population

28. Growth Rate In a given period of time a population…
Grows when more individuals are born than die (Born > Die)
Reduces in size when more individuals die than are born (Born < Die)
Stays the same size when the number of individuals that are born equal the number that die (Born = Die)

29. Population Growth
A population model describes the rate of population growth
The difference between the birthrate and the death rate
Birthrate – Death rate

30. Population Growth Models
Simple Model (Part I): Calculating the population growth rate
r(rate of growth) = birthrate – death rate
Simple Model (Part II): Exponential growth curve
∆ N (change in population) = rN
More realistic model: Logistic model
∆ N = rN (K-N)/K

31. Exponential Growth Curve
Dramatic increase in population over a short period of time
A single bacteria cell that divides every 30 minutes will produce more than 1 million bacteria after only 10 hours

32. Exponential Growth Curve
The number of individuals that will be added to the population as it grows
Multiply the size of the current population (N) by the rate of growth (r)

33. Logistic growth
Population growth that is characterized by a period of slow growth, followed by a period of exponential growth, followed by a period of almost no growth

34. Logistic Model A model of population growth that assumes:
Finite resource levels limit population growth
Birthrates and death rates vary with population size
When a population is below carrying capacity, the growth rate is rapid

35. Logistic Model
As the population approaches carrying capacity, death rates begin to rise and birthrates begin to decline…the rate of growth slows
The population eventually stops growing when the birthrate equals the death rate
In real situations, the population may, for a short time, exceed the carrying capacity

36. Logistic Model
If this happens, deaths will increase and outnumber births until the population falls down to the carrying capacity
Many scientists are concerned that Earth’s human population may have exceeded its carrying capacity (reached 6 billion in 1999)

37. Carrying Capacity (K)
The largest population that an environment can support at any given time
Populations do not usually grow unchecked

38. Carrying Capacity (K) Growth is limited by: Predators Disease
Availability of resources

39. Population crash
Dramatic decline in the size of a population over a short period of time

40. Ecological factors limit population growth
Limiting factor: environmental factor that limits the growth and size of a population

41. Density-dependent limiting factors
Environmental resistance that affects a population that has become overly crowded
Competition
Predation
Parasitism and disease
Resources in short supply eventually become depleted as a population grows
Examples: food and water

42. Density-independent limiting factors
Environmental resistance that affects a population regardless of population density
Unusual weather
Natural disasters
Human activities
Mosquito populations increase in the summer while the weather is warm, but decrease in the winter

43. Succession occurs following a disturbance in an ecosystem
Sequence of biological changes that regenerate a damaged community or start a community in a previously uninhabited area

44. Succession
The replacement of one type of community by another at a single location over a period of time
Species replacement

45. Pioneer Species
A species that colonizes an uninhabited area and starts an ecological cycle in which many other species become established
Occurs when a volcano forms a new island, a glacier recedes and exposes bare rock, or a fire burns all of the vegetation in an area…
Pioneer species tend to be small, fast-growing plants
They make the ground more hospitable for other species

46. Primary Succession
Succession that begins in an area the previously did not support life

47. Secondary Succession
The process by which one community replaces another community that has been partially or totally destroyed