1. An Introduction to Ecology and the Biosphere
Chapter 50
An Introduction to Ecology and the Biosphere

2. Overview: The Scope of Ecology
Ecology is the scientific study of the interactions between organisms and the environment
These interactions determine distribution of organisms and their abundance
Ecology reveals the richness of the biosphere

4. Concept 50.1: Ecology is the study of interactions between organisms and the environment
Ecology has a long history as a descriptive science
It is also a rigorous experimental science

5. Ecology and Evolutionary Biology
Events that occur in ecological time affect life on the scale of evolutionary time

6. Organisms and the Environment
The environment of any organism includes:
Abiotic, or nonliving, components
Biotic, or living, components
All the organisms that are part of the individual’s environment are collectively called the biota
Environmental components affect the distribution and abundance of organisms

7. LE 50-2 Kangaroos/km2 > 20 10–20 5–10 1–5 0.1–1 < 0.1 Limits of
distribution
Tasmania

8. Ecologists use observations and experiments to test explanations for the distribution and abundance of species

9. Subfields of Ecology
Organismal ecology studies how an organism’s structure, physiology, and (for animals) behavior meet environmental challenges

10. LE 50-3a
Organismal ecology

11. Population ecology focuses on factors affecting how many individuals of a species live in an area

12. LE 50-3b
Population ecology

13. Community ecology deals with the whole array of interacting species in a community

14. LE 50-3c
Community ecology

15. Ecosystem ecology emphasizes energy flow and chemical cycling among the various biotic and abiotic components

16. LE 50-3d
Ecosystem ecology

17. Landscape ecology deals with arrays of ecosystems and how they are arranged in a geographic region

18. LE 50-3e
Landscape ecology

19. The biosphere is the global ecosystem, the sum of all the planet’s ecosystems

20. Ecology and Environmental Issues
Ecology provides the scientific understanding underlying environmental issues
Rachel Carson is credited with starting the modern environmental movement

22. Most ecologists follow the precautionary principle regarding environmental issues
It states that humans need to be concerned with how their actions affect the environment

23. Concept 50.2: Interactions between organisms and the environment limit the distribution of species
Ecologists have long recognized global and regional patterns of distribution of organisms within the biosphere
Many naturalists began to identify broad patterns of distribution by naming biogeographic realms

24. LE 50-5 Palearctic Nearctic Tropic of Cancer (23.5°N) Oriental
Ethiopian
Equator
Neotropical
(23.5°S)
Tropic of
Capricorn
Australian

25. Biogeography is a good starting point for understanding what limits geographic distribution of species

26. LE 50-6 Species absent because Yes Area inaccessible
or insufficient time
Yes
Dispersal
limits
distribution?
Habitat selection
Yes
Predation, parasitism,
competition, disease
Behavior
limits
distribution?
Chemical
factors No
Biotic factors
(other species)
limit
distribution?
Water
Oxygen
Salinity pH
Soil nutrients, etc. No
Abiotic factors
limit
distribution? No
Temperature
Light
Soil structure
Fire
Moisture, etc.
Physical
factors

27. Dispersal and Distribution
Dispersal is movement of individuals away from centers of high population density or from their area of origin
Dispersal contributes to global distribution of organisms

28. Natural Range Expansions
Natural range expansions show the influence of dispersal on distribution

29. LE 50-7
New areas
occupied
Year
1996
1989
1974

30. Species Transplants
Species transplants include organisms that are intentionally or accidentally relocated from their original distribution
Species transplants can disrupt the communities or ecosystems to which they have been introduced

31. Behavior and Habitat Selection
Some organisms do not occupy all of their potential range
Species distribution may be limited by habitat selection behavior

32. Biotic Factors
Biotic factors that affect the distribution of organisms may include:
Interactions with other species
Predation
Competition

33. August 1982 February 1983 August 1983 February 1984
LE 50-8
100
Sea
urchin
Both limpets
and urchins
removed 80
Only
urchins
removed 60
Seaweed cover (%)
Limpet 40
Only limpets removed 20
Control (both
urchins and
limpets present)
August
1982
February
1983
August
1983
February
1984

34. Abiotic Factors Abiotic factors affecting distribution of organisms:
Temperature
Water
Sunlight
Wind
Rocks and soil

35. Temperature
Environmental temperature is an important factor in distribution of organisms because of its effects on biological processes

36. Water
Water availability in habitats is another important factor in species distribution

37. Sunlight Light intensity and quality affects photosynthesis
Light is also important to development and behavior of organisms sensitive to photoperiod

38. Wind
Wind amplifies effects of temperature by increasing heat loss from evaporation and convection
Wind can change morphology of plants

40. Rocks and Soil
Many characteristics of soil limit distribution of plants and thus the animals that feed upon them:
Physical structure pH
Mineral composition

41. Climate
Four major abiotic components of climate: temperature, water, sunlight, and wind
Climate is the prevailing weather in an area
Macroclimate consists of patterns on the global, regional, and local level
Microclimate consists of very fine patterns, such as those encountered by the community of organisms underneath a fallen log

42. Global Climate Patterns
Global climate patterns are determined largely by solar energy and the planet’s movement in space

43. Sunlight intensity plays a major part in determining the Earth’s climate patterns

44. LE 50-10a
North Pole
60°N
Low angle of incoming sunlight
30°N
Tropic of
Cancer
Sunlight directly overhead at equinoxes
0° (equator)
Tropic of
Capricorn
30°S
Low angle of incoming sunlight
60°S
South Pole
Atmosphere

45. Seasonal variations of light and temperature increase steadily toward the poles

46. LE 50-10b
March equinox: Equator faces sun directly; neither pole tilts toward sun; all regions on Earth experience 12 hours of daylight and 12 hours of darkness.
60°N
30°N
June solstice: Northern Hemisphere tilts toward sun; summer begins in Northern Hemisphere; winter begins in Southern Hemisphere.
0° (equator)
30°S
December solstice: Northern Hemisphere tilts away from sun; winter begins in Northern Hemisphere; summer begins in Southern Hemisphere.
Constant tilt
of 23.5°
September equinox: Equator faces sun directly; neither pole tilts toward sun; all regions on Earth experience 12 hours of daylight and 12 hours of darkness.

47. Global air circulation and wind patterns play major roles in determining climate patterns

48. LE 50-10c 60°N 30°N 0° (equator) 30°S 60°S Descending dry air absorbs
moisture
Descending
dry air
absorbs
moisture
0° (equator)
Ascending
moist air
releases
moisture
30°S
60°S
30°
23.5° 0°
23.5°
30°
Arid
zone
Tropics
Arid
zone

49. Arctic Circle 60°N Westerlies 30°N Northeast trades Doldrums 0°
LE 50-10d
Arctic
Circle
60°N
Westerlies
30°N
Northeast trades
Doldrums 0°
(equator)
Southeast trades
30°S
Westerlies
60°S
Antarctic
Circle

50. Regional, Local, and Seasonal Effects on Climate
Various features of the landscape contribute to local variations in climate
Seasonal variation also influences climate

51. Bodies of Water
Oceans and their currents and large lakes moderate the climate of nearby terrestrial environments

53. Mountains Mountains have a significant effect on
The amount of sunlight reaching an area
Local temperature
Rainfall

54. Wind direction East Pacific Ocean Sierra Nevada Coast Range
LE 50-12
Wind
direction
East
Pacific
Ocean
Sierra
Nevada
Coast
Range

55. Seasonality
The angle of the sun leads to many seasonal changes in local environments
Lakes are sensitive to seasonal temperature change and experience seasonal turnover

56. LE 50-13 Winter Spring Autumn Thermocline Summer O2 (mg/L) O2 (mg/L) 44 8 12 4 8 12
Lake depth (m)
Lake depth (m) 8 8 16 16 0° 4° 2° 4° 24 4° 4° 24 4° 4° 4° 4°
4°C
4°C
O2 concentration
High (>8 mg/L)
Medium (4–8 mg/L)
Low (<4 mg/L)
O2 (mg/L)
O2 (mg/L) 4 8 12 4 8 12
Lake depth (m)
Lake depth (m) 8 4°
22° 8 4°
20° 4°
18° 16 4° 8° 4° 6° 16 5° 24
4°C
4°C 24
Autumn
Thermocline
Summer

57. Microclimate
Microclimate is determined by fine-scale differences in abiotic factors

58. Long-Term Climate Change
One way to predict future global climate change is to study previous changes

59. Current range Predicted range Overlap 4.5°C warming over
LE 50-14
Current
range
Predicted
range
Overlap
4.5°C warming over
next century
6.5°C warming over
next century

60. Concept 50.3: Abiotic and biotic factors influence the structure and dynamics of aquatic biomes
Varying combinations of biotic and abiotic factors determine the nature of biomes
Biomes are the major ecological associations that occupy broad geographic regions of land or water

61. Aquatic biomes account for the largest part of the biosphere in terms of area
They can contain fresh water or salt water
Oceans cover about 75% of Earth’s surface and have an enormous impact on the biosphere

62. LE 50-15 30°N Tropic of Cancer Equator Continental shelf Tropic of
Capricorn
30°S
Key
Lakes
Rivers
Estuaries
Abyssal zone
(below oceanic
pelagic zone)
Coral
reefs
Oceanic
pelagic zone
Intertidal
zone

63. Many aquatic biomes are stratified into zones or layers defined by light penetration, temperature, and depth

64. Littoral zone Limnetic zone Photic zone Pelagic zone Benthic zone
LE 50-16a
Littoral
zone
Limnetic
zone
Photic
zone
Pelagic
zone
Benthic
zone
Aphotic
zone
Zonation in a lake

65. (deepest regions of ocean floor)
LE 50-16b
Intertidal zone
Neritic zone
Oceanic zone
Photic zone
200 m
Continental
shelf
Pelagic
zone
Benthic
zone
Aphotic
zone
2,500–6,000 m
Abyssal zone
(deepest regions of ocean floor)
Marine zonation

66. Major aquatic biomes:
Lakes
Wetlands
Streams and rivers
Estuaries
Intertidal zones
Oceanic pelagic biome
Coral reefs
Marine benthic zone

77. Video: Clownfish and Anemone
Video: Coral Reef
Video: Flapping Geese
Video: Hydrothermal Vent
Video: Shark Eating a Seal
Video: Tubeworms

78. Concept 50.4: Climate largely determines the distribution and structure of terrestrial biomes
Climate is very important in determining why terrestrial biomes are found in certain areas

79. Climate and Terrestrial Biomes
Climate has a great impact on the distribution of organisms, as seen on a climograph

80. Annual mean temperature (°C)
LE 50-18
Desert
Temperate grassland
Tropical forest 30
Temperate
broadleaf
forest 15
Annual mean temperature (°C)
Coniferous
forest
Arctic and
alpine
tundra
–15
100
200
300
400
Annual mean precipitation (cm)

81. LE 50-19 30°N Tropic of Cancer Equator Tropic of Capricorn 30°S
Chaparral
Key
Tundra
Temperate grassland
High mountains
Tropical forest
Temperate broadleaf forest
Polar ice
Savanna
Coniferous forest
Desert

82. General Features of Terrestrial Biomes
Terrestrial biomes are often named for major physical or climatic factors and for vegetation
Stratification is a key feature of terrestrial biomes
Terrestrial biomes usually grade into each other, without sharp boundaries
The area of intergradation, called an ecotone, may be wide or narrow

83. Major terrestrial biomes:
Tropical forest
Desert
Savanna
Chaparral
Temperate grassland
Coniferous forest
Temperate broadleaf forest
Tundra

92. Video: Swans Taking Flight