1. Ecologists study how organisms interact with their environment at several levels
Individual organisms interacting with the environment
Population
Group of individuals of the same species living in a particular geographic area

2. Community
All the populations of different species that inhabit a particular area
Ecosystem
All the biotic and abiotic components in a certain area
Ecological research is conducted in the field as well as in the lab and with models

3. THE BIOSPHERE The biosphere is the total of all of Earth's ecosystems
The biosphere is the global ecosystem
Atmosphere to an altitude of several kilometers
Land down to 3,000 m beneath Earth's surface
Oceans to a depth of several kilometers
The biosphere is self-contained and characterized by patchiness

6. Environmental problems reveal the limits of the biosphere
Current awareness of the biosphere's limits stems from past environmental practices
Rachel Carson warned of the effects of pesticides in 1962

8. Physical and chemical factors influence life in the biosphere
Major abiotic factors determine the biosphere's structure and dynamics
Solar energy
Water
Temperature
Wind
Disturbances such as fire, tornadoes

10. Organisms are adapted to abiotic and biotic factors by natural selection
Species exist in a given place because they evolve there or disperse there
Unique adaptations that fit a particular environment allow organisms to survive there
Example: pronghorns
Organisms vary in their ability to tolerate changes in their environment

14. STRUCTURAL FEATURES OF COMMUNITIES
Key characteristics of a community
Species diversity: variety of different kinds of organisms
Species richness
Relative abundance

15. Dominant species
Response to disturbances
Trophic structure: feeding relationships among species

17. Competition may occur when a shared resource is limited
Interspecific competition may play a major role in structuring a community
2 species competing for the same limited resource
May inhibit growth of one or both species

18. Competitive exclusion principle
2 species cannot coexist in a community if their niches are identical
Niche: species' total use of biotic and abiotic resources
2 possible results
Less competitive species will be driven to local extinction
Resource partitioning may evolve

19. LE 37-2a

20. LE 37-2b

21. Video: Seahorse Camouflage
Predation leads to diverse adaptations in both predator and prey
Predation is an interaction between species in which predator kills and eats prey
Adaptations of both tend to be refined through natural selection
Camouflage
Chemical defense
Video: Seahorse Camouflage

24. Batesian mimicry Mullerian mimicry
Palatable species mimics an unpalatable model
Mullerian mimicry
Two unpalatable species mimic each other

27. Predation can maintain diversity in a community
Keystone species
Exerts strong control on community structure because of its ecological niche
Keystone predator
May maintain community diversity by reducing numbers of the strongest competitors
Removal can cause major changes in community dynamics

31. Herbivores and the plants they eat have various adaptations
Herbivores are animals that eat plants or algae
Have adaptations for locating and eating vegetation
Plants have evolved defenses against herbivores
Toxic chemicals
Physical defenses (spines, thorns)

32. Some herbivore-plant interactions illustrate coevolution
Reciprocal evolutionary adaptations
Change in one species acts as a new selective force on another species

33. LE 37-5
Eggs
Sugar
deposits

34. Symbiotic relationships help structure communities
Symbiotic relationship: interaction between two or more species that live in direct contact
Parasitism
Parasite lives on or near its host
Parasite obtains nourishment at the expense of host
Includes pathogens that may inflict lethal harm on host

36. Commensalism Mutualism
One species benefits without significantly affecting the other
Few absolute cases documented
Mutualism
Both partners benefit

38. Disturbance is a prominent feature of most communities
Disturbances are characteristic of most biological communities
Events such as fire, storms, floods
Damage communities
Remove organisms from communities
Alter the availability of resources
Can have positive effects

39. Ecological succession is a transition in community species composition following a major disturbance
Primary succession: gradual colonization of barren rocks
Secondary succession: occurs after a disturbance has destroyed a community but left the soil intact

40. LE 37-7 Retreating glacier with moraine in the foreground Dryas stage
Spruce starting to appear in the
alder and cottonwood forest
Spruce and hemlock forest

42. Trophic structure is a key factor in community dynamics
Trophic structure: a pattern of feeding relationships consisting of several different levels
Food chain: sequence of food transfer up the trophic levels
Moves chemical nutrients and energy

43. Producers Primary consumers
Autotrophs that support all other trophic levels
Plants on land
In water, mainly photosynthetic protists and cyanobacteria
Primary consumers
Herbivores that eat plants, algae, or phytoplankton

44. Video: Shark Eating Seal
Secondary, tertiary, and quaternary consumers
Eat consumers from the level below them
Detritivores (decomposers)
Animal scavengers, fungi, and prokaryotes
Derive energy from detritus produced at all trophic levels
Decomposition is essential for recycling nutrients in ecosystems
Video: Shark Eating Seal

45. A terrestrial food chain
LE 37-9
Trophic level
Quaternary
consumers
Hawk
Killer whale
Tertiary
consumers
Snake
Tuna
Secondary
consumers
Mouse
Herring
Primary
consumers
Grasshopper
Zooplankton
Producers
Plant
Phytoplankton
A terrestrial food chain
An aquatic food chain

46. Food chains interconnect, forming food webs
A food web is a more realistic view of trophic structure
Consumers usually eat more than one type of food
Each food type is consumed by more than one type of consumer

47. LE 37-10 Quaternary, tertiary, and secondary consumers Tertiary and
primary
consumers
Primary
consumers
Producers
(plants)

48. Chemical cycling Chemical energy Heat energy Chemical elements
flow
Chemical
energy
Light
energy
Heat
energy
Chemical elements

49. Primary production sets the energy budget for ecosystems
Primary production: amount of solar energy converted by producers to chemical energy in biomass
Biomass: amount of organic material in an ecosystem
Net primary production: amount of biomass produced minus amount used by producers in cellular respiration
Varies greatly among ecosystems

50. Average net primary productivity (g/m2/yr)
LE 37-12
Open ocean
Estuary
Algal beds and coral reefs
Desert and semidesert scrub
Tundra
Temperate grassland
Cultivated land
Boreal forest (taiga)
Savanna
Temperate deciduous forest
Tropical rain forest
500
1,000
1,500
2,000
2,500
Average net primary productivity (g/m2/yr)

51. Energy supply limits the length of food chains
Only about 10% of the energy stored at each trophic level is available to the next level
Pyramid of production shows loss of energy from producers to higher trophic levels
Amount of energy available to top-level consumers is relatively small
Most food chains have only three to five levels

52. Tertiary consumers Secondary consumers Primary consumers Producers
LE 37-13
Tertiary
consumers
10 kcal
Secondary
consumers
100 kcal
Primary
consumers
1,000 kcal
Producers
10,000 kcal
1,000,000 kcal of sunlight

53. A production pyramid explains why meat is a luxury for humans
Human meat or fish eaters are tertiary or quaternary consumers
Humans eating grain have ten times more energy available than when they process the same amount of grain through meat
Using land to raise animals consumes more resources than using the land to cultivate crops

54. Trophic level Secondary consumers Human meat-eaters Primary consumers
vegetarians
Cattle
Corn
Corn
Producers

55. Biogeochemical cycles
Cycle nutrients through both biotic and abiotic components
Can be local or global

56. Consumers Producers Detritivores Nutrients available to producers
Abiotic
reservoir

57. Water moves through the biosphere in a global cycle
Solar energy drives the global water cycle
Precipitation
Evaporation
Transpiration
Water cycles between the land, oceans, and atmosphere
Forest destruction and irrigation affect the water cycle

58. Transport over land Solar energy Net movement of water vapor by wind
LE 37-16
Transport
over land
Solar energy
Net movement of
water vapor by wind
Precipitation
over land
Precipitation
over ocean
Evaporation
from ocean
Evaporation and
transpiration from
land
Percolation
through
soil
Runoff and
groundwater

59. The carbon cycle depends on photosynthesis and respiration
Carbon cycles through the atmosphere, fossil fuels, and dissolved carbon in oceans
Taken from the atmosphere by photosynthesis
Used to make organic molecules
Decomposed by detritivores
Returned to the atmosphere by cellular respiration
Burning of wood and fossil fuels is raising the level of CO2 in the atmosphere

60. CO2 in atmosphere Photosynthesis Cellular respiration Burning of
LE 37-17
CO2 in atmosphere
Photosynthesis
Cellular
respiration
Burning of
fossil fuels
and wood
Higher-level
consumers
Primary
consumers
Carbon compounds
in water
Detritus
Decomposition

61. The nitrogen cycle relies heavily on bacteria
Atmospheric N2 is not available to plants
Soil bacteria convert gaseous N2 to usable ammonium (NH4+) and nitrate (NO3-)
Some NH4+ and NO3- are made by chemical reactions in the atmosphere
Human activity is altering nitrogen cycle balance in many areas
Sewage treatment and fertilization

62. Nitrogen in atmosphere (N2)
LE 37-18
Nitrogen in atmosphere (N2)
Nitrogen
fixation
Assimilation
by plants
Denitrifying
bacteria
Nitrogen-fixing
bacteria in root
nodules of legumes
Nitrates
(NO3–)
Detritivores
Decomposition
Nitrifying
bacteria
Ammonium (NH4)
Nitrogen-fixing
soil bacteria

63. The phosphorus cycle depends on the weathering of rock
Phosphorus and other soil minerals are recycled locally
Weathering of rock adds PO43- to soil
Slow process makes amount of phosphorus available to plants low
Human activity has created phosphate pollution of water

64. Rain Geologic Weathering uplift of rocks of rocks Plants Runoff
LE 37-19ECOSYSTEM
Rain
Geologic
uplift
of rocks
Weathering
of rocks
Plants
Runoff
Consumption
Sedimentation
Plant uptake
of PO43–
Soil
Leaching
Decomposition