This document discusses key concepts in ecology, including the study of interactions between organisms and their environment. It defines biotic and abiotic factors, levels of ecological organization, habitats and niches. It also examines competition, predation, symbiosis, energy flow through ecosystems, trophic levels, food webs, and biogeochemical cycles of matter like carbon, oxygen, nitrogen and water. Maintaining balance through these processes is important for ecosystem health.

1. Principles of
Ecology
CH2

2. 2.1 Organisms and Their Relationships
Ecology: Study of interactions between
organisms and the living (biotic) and
nonliving (abiotic) components of their
environment.
Biotic Factors: in a pond, fish, algae, frogs,
insects, turtles, plants
Abiotic Factors: Temperature, air/water
currents, sunlight, soil type, precipitation,
nutrient availability.

3. LEVELS OF ORGANIZATION:
Population: All the interbreeding members
of a species in a community.
Community: All the species of organisms in
an ecosystem.
Ecosystems: Community of organisms and
non-living components in a particular place.
Ex:
pond, coral reef, mountain, desert Biome:
Group of ecosystems with similar climates &
communities. Biosphere:
Contains all life

5. ECOLOGY OF ORGANISMS:
Habitat: Where an organism lives
Niche: An organism’s role or way of life in the environment.
Fundamental: Where & how
organism could live Realized: Where & how it
actually lives in the face of competition.
Generalist: Broad niche, very
adaptable; Coyote, Hawk, rat.
Specialist: Very narrow niche; very limited. Koala
Abiotic factors change,and organisms that are adapted to
certain conditions may only survive where the environment
suits them.

6. A fundamental niche overlap results in two species using
the same resources; those organisms within the overlap
compete against their own & the other species; they are
eliminated, the species move apart, resulting in
character displacement.
COMPETITION

7. Resource partitioning in a tree. Species use different parts;
this allows greater numbers of individuals in each species,
and reduces the competition between species.

8. COMPETITION If more than one species uses
the same resource at the same time. More
efficient species may outcompete others.

9. Balanus removed: Chthamalus moves down; Chthalamus
removed, Balanus remained as it was; not adapted to life in
very dry areas.

10. COMPETITION:
Competitive
exclusion:
In using a
resource, more
efficient species
eliminates others
from the
community.

11. PREDATION
Natural selection favors predators with adaptations
that increase their efficiency in finding, capturing,
and killing prey.
Rattlesnakes have heat sensing pits, sharks sense
electrical impulses from victim’s muscles.
Both initiate hunt with excellent sense of smell.
Natural selection favors adaptations in prey
that help it escape predators.

12. In ecology, affecting one element of an
ecosystem will affect all other components, living
& non-living.
In Yellowstone, reintroduction of the wolf reduced
the number of deer in the park. Birch trees grew
along streams again, plants & animals associated
with Birch returned to the park.
Reintroduction of 1 species (wolf) resulted in
restoring proper ecologic balance to ecosystem,
and the reappearance of 200 associated species.

14. Torpedo Ray-
captures food by
electrocuting it
between its fins.
Glow worms attract
prey with light,
capture with silky,
sticky threads.

15. SYMBIOSIS: Organisms that are related
ecologically.
PARASITISM: Predator lives on/in prey,
weakens it.
MUTUALISM: 2 spp. Interact, help each
other.
COMMENSALISM: One benefits, other
unaware.

16. 2.2 Flow of Energy in an Ecosystem
PRODUCERS
Autotrophs: Make own food. Support whole
ecosystems by making organic molecules from
inorganic ones.
Photosynthesizers: Plants, algae, bacteria. Use
sunlight, CO2 , and H2O to make sugars.
Chemosynthesizers: Bacteria. Use
inorganic molecules to make sugars.
On land, plants are major producers. In aquatic
environments, algae and bacteria are major
producers.

17. CONSUMERS
Heterotrophs: Need to eat other organisms, or
organic wastes. All animals, most protists, all
fungi, many bacteria.
Herbivores: Eat plants; primary consumers.
Carnivores: Eat other consumers. Secondary
consumers
Omnivores: Eat producers and consumers.
Detritivores: consumers that eat dead
organisms, or their wastes.
Decomposers: Decay organic matter by
breaking down molecules; release nutrients into
the ecosystems.

18. PRODUCTIVITY:
Net Primary Productivity: Rate at which biomass
accumulates in a system.
Biomass: The organic material in an ecosystem
contained in living organisms. .

19. NET PRIMARY PRODUCTIVITY:

21. ENERGY FLOW
Trophic Level: An organism’s position in the
sequence of energy transfers. Energy is lost in
transfer from one level to the next.

22. FOOD WEB
Feeding relationships in an ecosystem; made up of
several overlapping food chains.

23. Pyramid of Biomass showing the relative
amounts of producers and consumers in an
ecosystem.

24. 2.3 Cycling of Matter
ECOSYSTEM RECYCLING
Biogeochemical Cycles: Substances moving
from abiotic portions of the environment, into
living organisms, and back again. Water,
Carbon, Oxygen, Nitrogen, and Phosphorus
cycles.

25. Water Cycle:
Water availability is a key factor regulating
ecosystem productivity.
Evaporation: Adds water vapor to atmosphere.
Transpiration: Water released from ground
through plants.
Precipitation: Water in atmosphere condenses,
and falls back to earth.

27. Carbon Cycle
Photosynthesizers use CO2 and water from
environment and sunlight to form sugars.
Sugars are stored in plants, algae, bacteria, and
are passed on as producers are eaten.
Sugars are broken down in producers and
consumers, usually with oxygen, to form CO2 and
water.

29. Oxygen is released into the atmosphere by
photosynthesis as sugars are made, and it is
removed by respiration, as sugars are broken
down.

30. Nitrogen Cycle
Nitrogen is needed by all organisms to make
DNA, RNA, and proteins.
Nitrogen gas is removed from the atmosphere
(78% N2 ) by nitrogen-fixing bacteria, which live in
soil and in the roots of some plants. These
bacteria convert N2 gas to ammonia, which is
then distributed throughout the ecosystem by
plant consumption & death. Nitrifying bacteria
convert ammonia to nitrates, which plants use to
grow.
Denitrifying bacteria release the nitrogen back
into the atmosphere,