3. 5.1 Ecological Concepts
Environment everything that affects an
organism during its lifetime.
• Abiotic factors: Nonliving things that influence an
organism
– energy, nonliving matter, living space, and ecological
processes
• Biotic factors: All forms of life with which the
organism interacts.
5. Limiting Factors
Limiting factors - factors whose shortage or
absence restricts species success.
• Scarcity of water or specific nutrients (plants).
• Climate, availability of a specific food (animals).
6. Limiting Factors
Range of tolerance - indicates a range of
conditions in which an organism can survive.
• Some species have a broad range of tolerance, while
others have a narrow range of tolerance.
8. Habitat—place
The habitat
• space in which an organism lives
• defined by the biological requirements of each particular
organism
• Usually highlighted by prominent physical or biological
features.
10. Niche--role
The niche
• functional role (profession) the organism has in its
surroundings
• Includes:
– all the ways it affects other organisms
– how it modifies its physical surroundings
13. A species
Species
• population of all the
organisms
• potentially capable of
reproducing naturally
among themselves
• and having offspring that
also reproduce.
14. 5.2 The Role of Natural Selection and
Evolution
Natural selection
• process that determines which individuals within a
species will reproduce and pass their genes to the
next generation.
• Mechanism that causes Evolution
Evolution
• Changes in genes and characteristics within
successive generations of a population over time
15. Natural Selection
Steps in natural selection:
Excess number of individuals
Results in a shortage of specific resources
Some individuals have a greater chance of obtaining
needed resources and
have a greater likelihood of surviving and reproducing than
others.
18. Natural Selection in Action
• Examples of natural selection include:
– Pesticide-resistant insects
– Antibiotic-resistant bacteria
– Drug-resistant strains of HIV
– http://www.pbs.org/wgbh/evolution/educators/teachstuds/svide
19. 5.3 Kinds of Organism Interactions
Predation
• interaction in which
one animal kills/eats
another.
• Predator benefits from
food.
• Prey have higher
reproduction rate
– (field mice 10 to 20
offspring/year)
20. Competition
Competition
interaction in which two
organisms strive to obtain
the same limited resource.
Intraspecific competitionbetween members of same
species.
Interspecific competitionbetween members of different
species.
21. Symbiotic Relationships
Symbiosis
• close, long-lasting, physical relationship between two
different species
• At least one species derives benefit from the interaction.
23. Symbiotic Relationships
Parasitism
• relationship in which one organism (parasite) lives in
or on another organism (host)
• which it derives nourishment
25. Symbiotic Relationships
Mutualism
• relationship in which both species benefit.
• The relationship is obligatory in many cases, as
neither can exist without the other.
• Mycorrhizae
26. 5.4 Ecosystem Interactions
An ecosystem
• defined space in which interactions take place
between a community and the physical environment.
• Ecologists have divided organisms’ roles in
ecosystems into three broad categories:
– 1. Producers
– 2. Consumers
– 3. Decomposers
27. 5.4 Ecosystem Interactions
Producers:
Organisms that are able to use sources of energy to make
complex organic molecules from simple inorganic
substances in their environment.
28. Major Roles of Organisms in Ecosystems
1. Consumers:
Organisms that require organic matter as a
source of food.
They consume organic matter to provide
energy, growth and survival.
29. Major Roles of Organisms in Ecosystems
•
Consumers can be further divided into categories based
on the things they eat and the way they obtain food.
–
–
–
Primary consumers, or herbivores, eat plants as a source
of food.
Secondary consumers, or carnivores, are animals that eat
other animals.
Omnivores consume both plants and animals.
30. Major Roles of
Organisms in
Ecosystems
Decomposers
use nonliving organic matter as a
source of energy and raw
materials to build their bodies.
Many small animals, bacteria,
and fungi fill this niche.
31. Keystone Species
A keystone species plays a critical role in the
maintenance of specific ecosystems.
33. Energy Flow Through Ecosystems
Each step in the flow of energy through an
ecosystem is known as a trophic level.
As energy moves from one trophic level to the
next, most of the useful energy (90%) is lost as
heat (second law of thermodynamics).
37. Food Chains
A food chain
series of organisms occupying
different trophic levels
through which energy passes as
a result of one organism
consuming another
Some chains rely on detritus.
38. Food Web
A food web
series of multiple,
overlapping food
chains.
• A single predator can
have multiple prey
species at the same
time.
39. Nutrient Cycles in Ecosystems—
Biogeochemical Cycles
Organisms are composed of molecules and
atoms that are cycled between living and nonliving portions of an ecosystem.
These nutrient cycles are called biogeochemical
cycles.
40. Carbon Cycle
1. Producers: Plants use carbon dioxide during
photosynthesis to produce sugars.
Oxygen is produced as a by-product.
1. Consumers: Herbivores eat plants
break down the complex organic molecules into simpler molecular
building blocks
incorporate those molecules into their structure.
Respiration produces CO2 and water and releases
those compounds back into the atmosphere.
41. Carbon Cycle
3. Decomposers: The decay process of
decomposers involves respiration
Release of carbon dioxide and water
Dead organisms are recycled
4. Carbon sinks
processes or situations that remove atoms
from active, short-term nutrient cycles
Ex: long-lived trees, fossil fuels
43. Human Impact on the Carbon Cycle
Burning fossil fuels takes carbon atoms that were
removed temporarily from the active, short-term
carbon cycle and reintroduces them into the active
cycle.
Converting forests (long-term carbon storage) to
agricultural land (short-term carbon storage) has
increased the amount of carbon dioxide in the
atmosphere.
44.
45. Nitrogen Cycle
The nitrogen cycle involves the cycling of nitrogen
atoms between abiotic and biotic ecosystem
components.
• Producers are unable to use atmospheric N.
– Must get nitrate (–NO3) or ammonia (NH3.)
• Nitrogen-fixing bacteria convert nitrogen gas N2 into
ammonia.
– Plants construct organic molecules.
– Eaten by animals.
46. Nitrogen Cycle
Decomposers also break down nitrogen-containing
molecules, releasing ammonia.
Primary sink for nitrogen is the atmosphere
48. Human Impact on the Nitrogen Cycle
If too much nitrogen or phosphorus is applied as
fertilizer, or if it is applied at the wrong time,
much of the fertilizer is carried into aquatic
ecosystems.
• The presence of these nutrients increases the growth
rate of bacteria, algae, and aquatic plants.
– Toxic algae can kill fish and poison humans.
– An increase in the number of plants and algae results in
lowered oxygen concentrations, creating “dead zones.”
49. Summary
An organism’s environment can be divided into
biotic (living) and abiotic (nonliving) components.
The space an organism occupies is its habitat, and
the role it plays is its niche.
Organisms interact with one another in a variety of
ways. Symbiotic relationships are those in which two
species live in physical contact and at least one
species derives benefit from the relationship.
In an ecosystem, energy is trapped by producers
and flows from producers through various trophic
levels of consumers.
50. Summary
The sequence of organisms through which
energy flows is called a food chain.
Multiple interconnecting food chains constitute a
food web.
The flow of atoms through an ecosystem
involves all the organisms in a community. The
carbon, nitrogen, and phosphorus cycles are
examples of how these materials are cycled in
ecosystems.
Notas do Editor
Figure 13.UN3 Summary: Darwin's observations and conclusion
Student Misconceptions and Concerns
1. Students must understand that the environment does the selecting (editing) in natural selection. Species do not evolve because of want or need. Biological diversity exists and the environment selects. Evolution is not deliberate, it is reactive.
2. A related point is what we learn from extinction. As Darwin noted, species become extinct because they do not get what they want or need!
3. The authors note that evolution is not goal directed and does not lead to perfectly adapted organisms. These excellent points represent two misunderstandings: 1) Instructors need to be clear that evolutionary change is a consequence of an immediate advantage, not a distant goal. Three-chambered hearts in amphibians evolved from two-chambered fish hearts because the three-chambered hearts conveyed an advantage, not because evolution was directed toward producing a four-chambered heart! 2) Evolutionary change only reflects improvement in the context of the immediate environment. What is better today may not be better tomorrow. Thus, species do not steadily get better, they respond to the environment or go extinct.
Teaching Tips
1. An analogy might be made between the specialized functions of finch beaks and the many types of screwdrivers that exist today. Each type of screwdriver (Phillips, flathead, long-handled, interchangeable tips) represents a specialization for a particular job.
2. Based upon the human condition, students are likely to think that reproduction is largely a choice, and less a consequence of good health or other adaptations. Yet, in our natural world, there are thousands of examples of the overproduction of offspring and resulting death or failure to reproduce. Thousands of acorns hanging from one tree, spores escaping from a puffball, or a salmon spawning thousands of eggs, are all easy examples of overproduction. Bring a few solid illustrations from your geographic region to bring home this point.