1. Chapters 52-54 Biology – Campbell • Reece
Ecology
Chapters 52-54
Biology – Campbell • Reece

2. Ecology and the biosphere

3. Ecology
The scientific study of interactions between organisms and the environment
Organismal
Population
Community
Ecosystem
Landscape
Global

4. Biotic & Abiotic Factors
Living factors
All the organisms that are part of the individual’s environment
Pathogens, parasites, predators, competitors, food availability
Abiotic
Nonliving factors
All the chemical and physical factors
Temperature, light, water, and nutrients

5. Are you still awake?
Identify 5 biotic and 5 abiotic factors in the school.

6. Climate The long-term, prevailing weather conditions in an area
Temperature, precipitation, sunlight, and wind
Influences the distribution of organisms
Global climate patterns are determined primarily by solar energy and planetary movement
Local climate patterns are influenced by proximity to water and landscape

7. Ocean Currents

8. Sunlight Intensity

9. Mountains

10. Are you still awake?
How can climate influence where organisms live?

11. Community ecology

12. Trophic Structure Feeding relationships in a community
Autotrophic organisms – primary producers
Herbivores – primary consumers
Carnivores – secondary, tertiary, and quaternary consumers
Decomposers
Food chain – transfer of energy from one organism to another
Food web – all of the feeding relationships within a community

13. Food Chains and Webs

14. Limits on Food Chain Length
Energetic hypothesis – food chains are limited by the inefficiency of energy transfer from organism to organism
Only about 10% of the energy is passed to the next trophic level
Dynamic stability hypothesis – long food chains are less stable than short chains
Population fluctuations at lower levels are magnified at higher levels
Top predators are most affected
N → V → H → P
N ← V ← H ← P

15. Just checking…
In this food web, what would happen to the other organisms if squids were removed from the ecosystem?

16. Species Diversity
The variety of different kinds of organisms that make up the community
Species richness – the number of different species
Relative abundance – the proportion of each species

17. Species with a Large Impact
Dominant species – most abundant or have the highest biomass
Invasive species – organisms that are introduced into a nonnative habitat
Keystone species – has a pivotal ecological niche
Foundation species (ecosystem ‘engineers’) – alter the physical environment

18. Keystone Species

19. Interspecific Interactions
Competition
Predation
Herbivory
Symbiosis
Parasitism
Mutualism
Commensalism

20. Competition
Individuals of different species compete for the same limited resources (food, water, shelter, etc.)
-/-
Competitive exclusion – two species competing for the same resource cannot coexist in the same place
One species will use the resources more efficiently and reproduce more rapidly

21. Ecological Niche A species use of the biotic and abiotic resources
Resource partitioning – use of different niches to avoid competition

22. Realized vs. Fundamental Niche
Fundamental niche – the niche potentially occupied by a species
Realized niche – the niche actually occupied by a species

23. Predation One species (predator) kills and eat the other (prey) +/-
Predators have adaptations to help the catch and kill their prey
Prey have adaptations to avoid capture
Cryptic coloration (camouflage), aposematic (warning) coloration, Batesian mimicry, Müllerian mimicry

24. Defensive Coloration

25. Herbivory An organism eats parts of a plant or alga +/-
Many herbivores have special adaptations to identify whether or not plants toxicity and nutrition
Plants use defenses such as toxins or structures (spines, thorns)

26. Symbiosis Two or more species live in direct contact with each other
May be harmful, helpful, or neutral
Parasitism
Mutualism
Commensalism

27. Parasitism
One organism (parasite) obtains nutrients from another organism (host) which is harmed
+/-
Endoparasites – live inside the host
Ectoparasites – live on the surface of the host
Parasites can significantly affect the survival, reproduction, and density of the host species

28. Mutualism Both species benefit +/+
Obligate mutualism – one species cannot survive without its partner
Facultative mutualism – both species can survive alone

29. Commensalism
One species benefits and the other is neither helped nor harmed
+/0
Difficult to identify in nature because there may be a slight benefit or slight harm

30. Does it make sense?
Is predation a type of symbiosis? Why or why not?

31. Ecological Succession
The series of changes that occurs in a community over time
Primary succession – occurs in an area where no life previously existed (no soil)
New volcanic island, receding glacier
Secondary succession – occurs when an existing community has been cleared by a disturbance (soil is intact)
Fire, hurricane, tornado, human activity

32. Primary Succession

33. Secondary Succession

34. Quick question…
Did the eruption at Mt. St. Helens, which included spewing of ash, but no lava, lead to primary succession or secondary succession? Explain.
Mt. St. Helens

35. Population ecology

36. Density and Dispersion
Population – a group of individuals of the same species living in the same area
Density – the number of individuals per unit area or volume
Number of bacteria per milliliter
Affected by emigration and immigration
Dispersion – the pattern of spacing
Clumped, uniform, random

37. Dispersion

38. Demography and Survivorship
Demography – the study of the vital statistics of a population and how they change over time
Survivorship curve – a plot of the proportion or numbers of individuals still alive at each age

39. Change in Population Size
Change = (births + immigrants) – (deaths + emigrants)
Demographers usually look more at birth and death rate to determine overall population growth
r (rate of increase) = births – deaths
r > 0 the population is growing
r < 0 the population is declining
r = 0 the population is stable (zero population growth)

40. Exponential Growth
A population whose members all have access to abundant food and reproduce at their reproductive potential
The population will increase exponentially
J-shaped curve

41. Logistic Growth
As population density increases, individuals have less access to resources
Carrying capacity (K) – the maximum population that an environment can support
S-shaped curve

42. What do you think?
Which type of population growth do humans exhibit? Explain.

43. Life Histories K-selection (density-dependent)
high density
high levels of competition and therefore, evolution will favor organisms with:
low reproductive rate
high survival rate
r-selection (density-independent)
low density
low levels of competition and evolution will favor organisms with a high reproductive rate

44. Limiting Factors
Density independent factors – the population is affected regardless of population size/density
Ex. Natural disasters, clear cutting a forest
Density dependent factors – the death rate rises or the birth rate falls as density rises
A population may change as a result of a combination of the two

45. Limiting Factors

46. Density-Dependent Factors
Competition for resources
Territoriality
Disease
Predation
Toxic wastes

47. Predator-Prey
Predators that rely heavily on a single prey may exhibit a fluctuating population

48. Human Population Growth

49. Growth Rate is Decreasing

50. Demographic Transition
Four stages of demographic transition:
Both birth & death rates are high, the population grows slowly
When health care improves, population size increases
Birth rates fall until they roughly equal death rates, population growth slows down and stops
Birth rate drops below replacement level, so population begins to decrease

51. Demographic Transition

52. Hmmm…
In which stage of the demographic transition is the United States? Explain.
Why is our population still increasing?

53. Age Structure
The distribution of ages in a specific population at a certain time
Can be graphed in a population pyramid

54. Declining Death Rates
Death rates have declined mainly because more people have access to adequate food, clean water, safe sewage disposal, and medicines
Life expectancy – the average number of years members of a population are likely to live
Most affected by infant mortality

55. Infant Mortality and Life Expectancy

56. Global Carrying Capacity
~10-15 billion people
World Population Clock
Based on many factors including amount of habitable land, available food (including farmland, average yield of crops, diet)
Ecological footprint estimates the amount of land and water area required by each person