3-1
WHAT IS ECOLOGY?
- The scientific study of interactions among and
between organisms and their environment
Biosphere
- the portion of the planet where all life exists
- it includes: land, water, and the atmosphere
- within the biosphere, organisms interact and
become dependent on each other and the environment
Ecological Levels of Organization
- range from the study of an individual organism to
populations, communities, ecosystems, biomes and finally
the biosphere
species
- groups of organisms similar enough to breed and
produce fertile offspring
populations
- individuals that belong to the same species and live in
the same area
communities
- groups of different populations living in a particular
region
ecosystem
- a collection of all the organisms of a particular place
along with their non-living (physical) environment
biome
- a group of ecosystems with the same climate and
similar dominant communities
all biomes are found within the biosphere
Ecological Levels of
Organization
3-2 Energy Flow through the
Ecosystem
A. Producers
- sunlight is the main energy source of life used by
plants, algae, and some bacteria and they are called
autotrophs or producers
- some organisms like certain types of bacteria obtain
energy from other sources such as energy stored in inorganic
chemical compounds such as hydrogen sulfide
(chemosynthesis)
Ex. Mineral water from hot springs or underwater
sea vents
- producers are necessary to the flow of
energy through the biosphere
Energy from the sun
- energy is obtained through photosynthesis
- light energy powers chemical reactions to change
carbon dioxide and water into oxygen and carbohydrates
such as sugar and starch
- photosynthesis adds oxygen and removes carbon
dioxide from the atmosphere and the autotrophs provide the
oxygen that we need
The main autotrophs are:
1. plants – land
2. algae – upper layers of ocean and freshwater
ecosystems (lakes, rivers, etc.)
3. photosynthetic bacteria – found in tidal flats and salt
marshes
B. Consumers
- organisms who cannot get energy directly from the
environment
- includes animals, fungi, and some bacteria
- acquire energy and food from other organisms and
are called heterotrophs or consumers
Examples:
1. herbivores – eat only plants; cows, deer
2. carnivores – eat animals; snakes, dogs, owls
3. omnivores – eat plants and animals; humans, bears,
crows
4. detrivores – eat decaying, dead matter (detritus);
earthworms, snails, crabs, mites
5. decomposers – break down organic matter; bacteria
and fungi
C. Feeding Relationships
- Energy flows through the ecosystem in one direction
Sun and
inorganic compoundsautotrophsheterotrophs
(producers) (consumers)
1. Food chain
- a series of steps in which organisms transfer energy
by eating and being eaten
2. Food Webs
- show more complex feeding relationships among
organisms in an ecosystem
- they link all the food chains in an ecosystem Fig. 3-8
3. Trophic Levels
- represent each step in a food chain
- producers are on the first trophic level
- consumers are on the second, third, or higher trophic
levels
- each consumer depends on the level below it for
energy
Trophic Levels
D. Ecological Pyramids
- diagrams showing amounts of energy or matter
contained in each trophic level in a food chain or web
3 Types of pyramids:
1. Energy Pyramid
- shows the amount of energy available at each
trophic level
- organisms use only 10% of this for life processes;
the rest is lost as heat
- the more levels that exist, the less energy that
remains from the original amount
Energy Pyramid
2. Biomass Pyramid
- shows the amount of living organism matter in each
trophic level with greatest biomass at the base
- represents the amount of potential food available at
each level
3. Pyramid of Numbers
- shows the number of individual organisms at each
trophic level
3-3 Cycles of Matter
A. Recycling in the biosphere
- matter is recycled differently than energy
- it is recycled within and between ecosystems
- elements, compounds, and other forms of matter are
passed from one organism to another and from one
biosphere to another through biogeochemical cycles
• connect biological,
geological, and chemical parts of the biosphere
Water Cycle
- water moves between the ocean, atmosphere, and
land
- involves evaporation and transpiration
Nutrient Cycles
- like water, nutrients are passed between organisms
and the environment through biogeochemical cycles
- nutrients are chemical substances that an organism
requires to live; the body’s “building blocks”
Carbon Cycle
- carbon is the key ingredient in all living organisms
- it is found in the oceans, air, and certain rocks
Four processes are involved in the carbon cycle:
1.
-
Biological Processes
photosynthesis (removes carbon dioxide)
respiration (adds carbon dioxide)
decomposition of plants and animals
2. Geochemical Processes
- release of carbon dioxide gas into the atmosphere by volcanoes
3. Mixed biogeochemical processes
- burial of carbon-rich remains of organisms and their conversion into coal and
petroleum (fossil fuel)
4.
-
Human activity
mining
burning of fossil fuels
cutting and burning of forests
Fig. 3-13
Carbon Cycle
The Nitrogen Cycle
- atmosphere is the main reservoir of nitrogen in the
biosphere
- it cycles through soil and tissues of living organisms
- nitrogen is required to make amino acids (the building
blocks of proteins)
- only certain forms of bacteria can use nitrogen gas; they
live in soil and roots of legumes (beans and peas)
- these bacteria convert nitrogen gas to ammonia (nitrogen
fixation)
- other bacteria in the soil convert the ammonia into nitrates
and nitrites which can be used by producers
- some bacteria convert nitrates and nitrites into nitrogen
gas (denitrification); the gas is released back into the atmosphere
Nitrogen Cycle
Phosphorous cycle
- Phosphorous is essential because it forms important
molecules found in DNA and RNA
- It is not common in the biosphere
- It does not enter the atmosphere; it is found in rocks
and minerals on land, and in ocean sediment
- Phosphate is released as rocks and sediments wear
down; it washes into and dissolves in streams and rivers and
finds its way to oceans where it is used by marine organisms
Phosphorous Cycle
Nutrient Limitation
Primary productivity of the ecosystem
- the rate at which organic matter is created by producers
- controlled by the available nutrients
- the limiting nutrient is a single nutrient that is scarce or
cycles very slowly
- causes farmers to add fertilizer to increase crop
production
- fertilizers contain nitrogen, phosphorous, and potassium
- In oceans the limiting nutrient is nitrogen or sometimes
silica or iron
- In fresh water, the limiting nutrient is phosphorous
Algal Blooms
- increase in algae in aquatic ecosystems
- the result of runoff from heavily fertilized fields
- sometimes upsets the health of the ecosystem
Red Tide