1. Unit 2
Ecology
Chapter 3 – The Biosphere

2. Introduction to Ecology
Ecology - the scientific study of interactions among organisms and between organisms and their physical environment.
Ecologist - a scientist who studies organisms as they interact with other organisms within an ecosystem

3. Levels of Organization
Individual Organism
Population—a group of individuals that belong to the same species and live in the same area
Community—an assemblage of different populations that live together in a defined area
Ecosystem—all the organisms that live in a place, together with their physical environment
Biome—a group of ecosystems that share similar climates and typical organisms
Biosphere—our entire planet, with all its organisms and physical environments

4. Types of Ecosystems Natural Ecosystems Self sustaining
Precipitation
Sunlight
All resources to support life
Destroyed by natural disasters (fires)
Human-Made Ecosystems
Not self sustaining
Farms
Cities
Flower gardens
Aquariums
Zoo
Huge inputs of resources and energy

5. Relationships Within an Ecosystem
An ecosystem is a group of organisms that live together and interact with each other and their environment.
Organisms respond to their environments and can change their environments, producing an ever-changing biosphere.

6. Biotic Factors Abiotic Factors Anything non- living!
List three example of abiotic components in an ecosystem and why they are important?
Anything living in an ecosystem!
List three example of biotic components in an ecosystem and how they interact?

7. Biomes
A large geographic region determined by climate, soil type and plant life.
Why is plant life so important to an ecosystem?

8. Biomes Arctic Tundra Northern Coniferous Forest or Taiga
Temperate Deciduous Forest
Temperate Grasslands or Prairie
Desert
Tropical Savanna
Tropical Rain Forest

9. Population Studies: factors that affect the size of a population
Carrying capacity:
The maximum size of the population that an ecosystem can hold
Limiting factors:
Anything that prevents the
population size from increasing
Examples ?

10. Food Chains and Food Webs
How does energy flow through ecosystems?
Energy flows through an ecosystem in a one-way stream, from primary
producers to various consumers. Energy moves from the “eaten” to the “eater.” Where it goes from there depends on who eats whom!

11. The arrow must point toward the “eater”.
Food Chain
The arrows in a food chain show what eats what. The arrow replaces the phrase “is eaten by”.
The arrow must point toward the “eater”.
Leaf  Grasshopper  Frog  Heron

12. Food Webs
This is who eats who or what in the ecosystem. Each organism has a “job title” that describes their role. Anything that affects one level will probably affect the entire ecosystem!

13. Food Web
A food web shows the many possible food chains that exist in an ecosystem.

14. Food Webs “Job Titles”
Producers- Plants. They are the basis for life in the ecosystem.
These organisms are also called autotrophs.

15. Most Producers get Energy From the Sun
The best-known and most common primary producers harness solar energy through the process of photosynthesis.
Photosynthesis captures light energy and uses it to power chemical reactions that convert carbon dioxide and water into oxygen and energy-rich carbohydrates. This process adds oxygen to the atmosphere and removes carbon dioxide.
Most photosynthesis occurs in plants on land and algae in water ecosystems.

16. Life Without Light
Deep-sea ecosystems depend on primary producers that harness chemical energy from inorganic molecules such as hydrogen sulfide. The use of chemical energy to produce carbohydrates is called chemosynthesis.

17. Food Webs “Job Titles”
Consumers- these organism eat other organisms. They can not make their own food, therefore, they must “order out”!
Organisms that must acquire energy from other organisms by ingesting in some way are also known as heterotrophs.

18. Food Webs “Job Titles”
Consumers may be herbivores (plant eaters), carnivores (meat eaters) or omnivores (both)
Carnivores are usually referred to as predators!

19. Food Webs “Job Titles” 1st or PRIMARY level consumers are herbivores
2nd or SECONDARY level consumers are carnivores or omnivores and eat 1st order consumers
What are 3rd order (level) consumers?

20. Food Webs “Job Titles”
Decomposers- These are the recycling centers of the ecosystem. They break-down dead organisms into nutrients in the soil that plants can use as vitamins.
Bacteria and Fungus
Detritivores, feed on detritus particles (what is left from the decomposers,) often chewing or grinding them into smaller pieces.
giant earthworms

21. Food Webs “Job Titles”
Scavengers- Similar to decomposers because they eat already dead organisms and return nutrients to the soil.
Animals, birds, insects

22. Trophic Levels and Ecological Pyramids
Each step in a food chain or food web is called a trophic level.
Primary producers always make up the first trophic level.
Various consumers occupy every other level. Some examples are shown.
Ecological pyramids show the relative amount of energy or matter contained within each trophic level in a given food chain or food web.

23. Advantages and Disadvantages of the Pyramids
Pyramids of numbers and biomass can sometimes be inverted due to certain situations within ecosystems
These inverted pyramids then lose their ability to accurately represent the passage of energy from one trophic level to the next

24. Pyramid of Numbers
This represents the number of organisms that occupy each trophic level

25. Pyramids of Energy
Pyramids of energy show the relative amount of energy available at each trophic level.
On average, about 10 percent of the energy available within one trophic level is transferred to the next trophic level.
The more levels that exist between a producer and a consumer, the smaller the percentage of the original energy from producers that is available to that consumer.

26. Pyramid of Biomass
The total amount of living tissue within a given trophic level is called its biomass.
A pyramid of biomass illustrates the relative amount of living organic matter at each trophic level.

27. Recycling in the Biosphere
Unlike the one-way flow of energy, matter is recycled within and between ecosystems.
Elements pass from one organism to another and among parts of the biosphere through closed loops called biogeochemical cycles, which are powered by the flow of energy.
Biogeochemical cycles of matter involve biological processes, geological processes, and chemical processes.

28. Recycling in the Biosphere
As matter moves through these cycles, it is never created or destroyed—just changed.
Biogeochemical cycles of matter pass the same atoms and molecules around again and again.

29. Water Cycle Also called the Hydrologic Cycle
Movement and storage of water on the planet
Total amount of water doesn’t change – it is transported around the earth
Energy to run the cycle comes from the sun

30. Water vapor (gaseous state) returns to the atmosphere
Water re-enters that atmosphere by two processes
Evaporation changes surface water (lakes, rivers, oceans) to water vapor
Water vapor (gaseous state) returns to the atmosphere
Transpiration is the loss of water vapor from the leaves of plants
Stomata are openings in leaves which allow the water vapor out of the plant

31. Condensation
As the water vapor rises in the atmosphere, it looses energy (cools down)
Water droplets are formed from the water vapor
Precipitation
When the water droplets get too heavy it falls from the sky
Weather conditions determine the type of precipitation – rain, snow, sleet

32. Some precipitation re-evaporates before it reaches the ground
Most precipitation falls into existing bodies of water
70% of the earth’s surface is water
The rest falls on land
Absorbed into the soil or flows over the surface as Runoff (back to the oceans/lakes)
Infiltration is the process of water entering the ground

33. The cycle begins again:
Evaporation and transpiration
Condensation
Precipitation
Runoff and Infiltration
The amount of precipitation is an important factor in the type of ecosystem and the population of organisms it can support

34. Nutrient Cycles
The chemical substances that an organism needs to sustain life are called nutrients.
Every organism needs nutrients to build tissues and carry out life functions.
Nutrients pass through organisms and the environment through biogeochemical cycles.

35. The Carbon – Oxygen Cycle
Carbon is a major component of all organic compounds, including carbohydrates, lipids, proteins, and nucleic acids.

36. The Carbon – Oxygen Cycle
Plants take in carbon dioxide during photosynthesis and use the carbon to build carbohydrates.
Carbohydrates then pass through food webs to consumers.
Organisms release carbon in the form of carbon dioxide gas by respiration.

37. The Nitrogen Cycle
All organisms require nitrogen to make amino acids, which are used to build proteins and nucleic acids, which combine to form DNA and RNA.

38. The Nitrogen Cycle
Nitrogen-containing substances such as ammonia (NH3), nitrate ions (NO3), and nitrite ions (NO2) are found in soil, in the wastes produced by many organisms, and in dead and decaying organic matter.

39. The Nitrogen Cycle
Nitrogen gas (N2) makes up 78 percent of Earth’s atmosphere.
Although nitrogen gas is the most abundant form of nitrogen on Earth, only certain types of bacteria that live in the soil and on the roots of legumes can use this form directly.
The bacteria convert nitrogen gas into ammonia, in a process known as nitrogen fixation.

40. The Nitrogen Cycle
Other soil bacteria convert fixed nitrogen into nitrates and nitrites that primary producers can use to make proteins and nucleic acids.
Consumers eat the producers and reuse nitrogen to make their own nitrogen-containing compounds

41. The Nitrogen Cycle
Consumers eat the producers and reuse nitrogen to make their own nitrogen-containing compounds.
Decomposers release nitrogen from waste and dead organisms as ammonia, nitrates, and nitrites that producers may take up again.

42. The Nitrogen Cycle
Other soil bacteria obtain energy by converting nitrates into nitrogen gas, which is released into the atmosphere in a process called denitrification.
A small amount of nitrogen gas is converted to usable forms by lightning in a process called atmospheric nitrogen fixation.
Humans add nitrogen to the biosphere through the manufacture and use of fertilizers. Excess fertilizer is often carried into surface water or groundwater by precipitation.

43. The Phosphorus Cycle
Phosphorus forms a part of vital molecules such as DNA and RNA.
Although phosphorus is of great biological importance, it is not abundant in the biosphere.
Phosphorus in the form of inorganic phosphate remains mostly on land, in the form of phosphate rock and soil minerals, and in the ocean, as dissolved phosphate and phosphate sediments.

44. The Phosphorus Cycle
As rocks and sediments wear down, phosphate is released
Plants bind phosphate into organic compounds when they absorb it from soil or water.
Organic phosphate moves through the food web, from producers to consumers, and to the rest of the ecosystem.

45. Nutrient Limitation
Ecologists are often interested in an ecosystem’s primary productivity—the rate at which primary producers create organic material.
A nutrient whose supply limits productivity is called the limiting nutrient.
All nutrient cycles work together like the gears shown.
If any nutrient is in short supply—if any wheel “sticks”— the whole system slows down or stops altogether.

46. Nutrient Limitation in Aquatic Ecosystems
Sometimes an aquatic ecosystem receives a large input of a limiting nutrient—for example, runoff from heavily fertilized fields.
The result of this runoff can be an algal bloom—a dramatic increase in the amount of algae and other primary producers due to the increase in nutrients.

47. Energy flow in ecosystems

48. What is an ecosystem?
System = regularly interacting and interdependent components forming a unified whole
Ecosystem = an ecological system;
= a community and its physical environment treated together as a functional system

49. OR, MORE SIMPLY
an ecosystem is composed of the organisms and physical environment of a specified area.
SIZE: micro to MACRO

50. Attributes of Ecosystems
Order
Development
Metabolism (energy flow) 10% RULE
Material cycles
Response to the environment
Porous boundaries
Emphasis on function, not species

51. ENERGY FLOW IN ECOSYSTEMS
All organisms require energy, for growth, maintenance, reproduction, locomotion, etc.
Hence, for all organisms there must be: A source of energy
A loss of usable energy

52. Types of energy heat energy
mechanical energy (+gravitational energy, etc.)
chemical energy = energy stored in
molecular bonds

53. Transformations of energy
How is solar energy converted to chemical energy?

54. An ecosystem has abiotic and biotic components:
ABIOTIC components:
Solar energy provides practically all the energy for ecosystems.
Inorganic substances, e.g., sulfur, boron, tend to cycle through ecosystems.
Organic compounds, such as proteins, carbohydrates, lipids, and other complex molecules, form a link between biotic and abiotic components of the system.

55. BIOTIC components:
The biotic components of an ecosystem can be classified according to their mode of energy acquisition.
In this type of classification, there are:
Autotrophs
and
Heterotrophs

56. Autotrophs photoautotrophs
Autotrophs (=self-nourishing) are called primary producers.
Photoautotrophs fix energy from the sun and store it in complex organic compounds
(= green plants, algae, some bacteria)
light
simple
inorganic
compounds
complex
organic
compounds
photoautotrophs

57. and produce complex organic compounds.
Chemoautotrophs (chemosynthesizers) are bacteria that oxidize reduced inorganic substances
(typically sulfur and ammonia compounds)
and produce complex organic compounds.
oxygen
reduced
inorganic
compounds
complex
organic
compounds
chemoautotrophs

58. Chemosynthesis near hydrothermal vents

59. Other chemoautotrophs:
Nitrifying bacteria in the soil under our feet!

60. Heterotrophs heterotrophs
Heterotrophs (=other-nourishing) cannot produce their own food directly from sunlight+ inorganic compounds. They require energy previously stored in complex molecules.
heat
complex
organic
compounds
simple
inorganic
compounds
heterotrophs
(this may include several steps, with
several different types of organisms)

61. Heterotrophs can be grouped as:
consumers
decomposers

62. Consumers feed on organisms or particulate organic matter.
Decomposers utilize complex compounds in dead protoplasm.
Bacteria and fungi are the main groups of decomposers.
Bacteria are the main feeders on animal material.
Fungi feed primarily on plants, although bacteria also are important in some plant decomposition processes.

63. Energy flow Simplistically: heat Producers Consumers
This pattern of energy flow among different organisms is the TROPHIC STRUCTURE of an ecosystem.
heat
Producers
Consumers
Decomposers
heat

64. It is useful to distinguish different types of organisms within these major groups, particularly within the consumer group.
Consumers

65. Terminology of trophic levels
We can further separate the TROPHIC LEVELS, particularly the Consumers:
Producers (Plants, algae, cyanobacteria; some chemotrophs)--capture energy, produce complex organic compounds
Primary consumers--feed on producers
Secondary consumers--feed on primary consumers
Tertiary consumers--feed on secondary consumers

66. More trophic levels:
Detritivores--invertebrates that feed on organic wastes and dead organisms (detritus) from all trophic levels
Decomposers--bacteria and fungi that break down dead material into inorganic materials

67. Alternate Terminology
Producers = plants etc. that capture energy from the sun
Herbivores = plant-eaters
Carnivores = animal-eaters
Omnivores--eat both animals and plants
Specialized herbivores:
Granivores--seed-eaters
Frugivores--fruit-eaters

68. Together, these groups make up a FOOD CHAIN
E.g., grass, rabbit, eagle
Producer
Carnivore
Herbivore

69. Carnivores Carnivores can be further divided into groups:
quaternary carnivore (top)
tertiary carnivore
secondary carnivore
primary carnivore
The last carnivore in a chain, which is not usually eaten by any other carnivore, is often referred to as the top carnivore.

70. Food chains

71. Problems
Too simplistic
No detritivores
Chains too long

72. Rarely are things as simple as grass, rabbit, hawk, or indeed any simple linear sequence of organisms.
More typically, there are multiple interactions, so that we end up with a FOOD WEB.

74. Energy transfers among trophic levels
How much energy is passed from one trophic level to the next?
How efficient are such transfers?

75. Biomass--the dry mass of organic material in the organism(s).
(the mass of water is not usually included, since water content is variable and contains no usable energy)
Standing crop--the amount of biomass present at any point in time.

76. Primary productivity
Primary productivity is the rate of energy capture by producers.
= the amount of new biomass of producers, per unit time and space

77. Ecological pyramids
The standing crop, productivity, number of organisms, etc. of an ecosystem can be conveniently depicted using “pyramids”, where the size of each compartment represents the amount of the item in each trophic level of a food chain.
Note that the complexities of the interactions in a food web are not shown in a pyramid; but, pyramids are often useful conceptual devices--they give one a sense of the overall form of the trophic structure of an ecosystem.
producers
herbivores
carnivores

78. Pyramid of energy
A pyramid of energy depicts the energy flow, or productivity, of each trophic level.
Due to the Laws of Thermodynamics, each higher level must be smaller than lower levels, due to loss of some energy as heat (via respiration) within each level.
Energy flow in :
producers
herbivores
carnivores

79. Pyramid of numbers
A pyramid of numbers indicates the number of individuals in each trophic level.
Since the size of individuals may vary widely and may not indicate the productivity of that individual, pyramids of numbers say little or nothing about the amount of energy moving through the ecosystem.
# of carnivores
# of herbivores
# of producers

80. Pyramid of standing crop
A pyramid of standing crop indicates how much biomass is present in each trophic level at any one time.
As for pyramids of numbers, a pyramid of standing crop may not well reflect the flow of energy through the system, due to different sizes and growth rates of organisms.
biomass of carnivores
biomass of herbivores
biomass of producers
(at one point in time)

81. Inverted pyramids
A pyramid of standing crop (or of numbers) may be inverted, i.e., a higher trophic level may have a larger standing crop than a lower trophic level.
This can occur if the lower trophic level has a high rate of turnover of small individuals (and high rate of productivity), such that the First and Second Laws of Thermodynamics are not violated.
biomass of carnivores
biomass of herbivores
biomass of producers
(at one point in time)

82. Pyramid of yearly biomass production
If the biomass produced by a trophic level is summed over a year (or the appropriate complete cycle period), then the pyramid of total biomass produced must resemble the pyramid of energy flow, since biomass can be equated to energy.
Yearly biomass production
(or energy flow) of:
producers
herbivores
carnivores

83. Note that pyramids of energy and yearly biomass production can never be inverted, since this would violate the laws of thermodynamics.
Pyramids of standing crop and numbers can be inverted, since the amount of organisms at any one time does not indicate the amount of energy flowing through the system.
E.g., consider the amount of food you eat in a year compared to the amount on hand in your pantry.

84. Ecological Interactions and Interdependence
Population – group of individuals of the same species
living in the same area, potentially interacting
Community – group of populations of different species
living in the same area, potentially interacting
What are some ecological interactions?

85. Why are ecological interactions important?
Interactions can affect distribution and abundance.
Interactions can influence evolution.
Think about how the following interactions can affect
distribution, abundance, and evolution.

86. competition predation parasitism mutualism commensalism symbiosis
Types of ecological interactions & interdependence
competition
predation
parasitism
mutualism
commensalism
symbiosis

88. Competition – two species share a requirement for a
limited resource  reduces fitness of one or both species

89. Predation – one species feeds on another  enhances
fitness of predator but reduces fitness of prey
herbivory is a form of
predation

90. Parasitism – one species feeds on another  enhances
fitness of parasite but reduces fitness of host

91. Mutualism – two species provide resources or services
to each other  enhances fitness of both species

92. Commensalism – one species receives a benefit from
another species  enhances fitness of one species; no
effect on fitness of the other species

93. Symbiosis – two species live together  can include
parasitism, mutualism, and commensalism

94. + 0 - + - Organizing ecological interactions & interdependence
effect on species 1
predation
herbivory
parasitism + -
commensalism
mutualism
effect on
species 2
competition