Chapter 3 Notes
Ecology – the scientific study of interactions among organisms
and between organisms and their environment
Levels of Organization
Species – a group of organisms so similar to one another that they can
breed and produce fertile offspring
Populations – groups of individuals that belong to the same species and
live in the same area
Communities – assemblages of different populations that live together in
a defined area
Ecosystem – a collection of all the organisms that live in a particular
place, together with their nonliving environment
Biome – group of ecosystems that have the same climate and similar
dominant communities
Biosphere – contains the combined portions of the planet in which all of
life exists, including land, water, and air –extends 8 kilometers
above Earth’s surface to as far as 11 kilometers below the
surface
Autotroph – capture energy from sunlight and use that energy to produce
food; also called producers; plants, some algae, and certain bacteria
*autotrophs use photosynthesis to make energy rich carbohydrates such as
sugars and starches
Photosynthesis
light energy
CO2 + H2O
*on land, plants are main autotrophs
*in water, algae are main autotrophs
C6H12O6 +O2
Heterotroph – organism that relies on other organisms for their
energy and food supply; also called consumers
Types of Heterotrophs
1. Herbivore – eat only plants
examples: cows, caterpillars, deer
2. Carnivore – eat animals
examples: snakes, dogs, owls
3. Omnivore – eat both plants and animals
examples: humans, bears, crows
4. Detrivore – feed on plant and animal remains and other dead matter
examples: mites, earthworms, snails, crabs
5. Decomposer – break down organic matter
examples: bacteria and fungi
Energy flows through an ecosystem in one direction
Sun
autotrophs
heterotrophs
producers
consumers
Food chain – a series of steps in which an organism transfers energy by eating
and being eaten
Possible prairie food chain
GRASS
Food web – a network of food chains
Antelope
Coyote
herbivore
carnivore
Trophic level – each step in a food chain or food web
algae
zooplankton
small fish
trophic
trophic
trophic
level
level
level
squid
shark
trophic
trophic
level
level
Ecological pyramid – diagram that shows the relative amounts of energy or matter
contained within each trophic level
3 Types:
1. energy pyramids
2. biomass pyramids
3. pyramids of numbers
Energy Pyramid
Hawk .1%
Snakes
1%
Mice 10 %
Grass 100%
* Only about 10% of the energy available within one trophic level is
transferred to organisms at the next trophic level.
More than 95% of our body is composed of just four elements:
*oxygen
*carbon
*hydrogen
*nitrogen
Recycling in the Biosphere
Biogeochemical cycle – molecules pass around again and
again within the biosphere
Example: the same oxygen (O2) you inhale might have been inhaled by
dinosaurs millions of years ago
The Water Cycle
How does water travel?
Evaporation – water changes from liquid form to an atmospheric gas
Ocean
gas
H2O
evaporation
transpiration – water evaporating from leaves
gas
transpiration
Water vapor (gas) cools and
condenses into droplets that form
clouds
Large droplets become precipitation
(snow, rain, sleet, or hail)
Warm air meets cold air
Condensation
precipitation
- precipitation runs into rivers or streams or oceans
- rain seeps into the soil
- some rain becomes ground water
- water in the soil is taken up by plant roots
Nurtrient Cycles
1.
Carbon Cycle
- Carbon is a key ingredient in all living organisms
- Bilogical processes, such as photosynthesis, respiration, and decomposition of plants and
animals
- Geochemical processes (CO2 released by volcanoes)
- Burial of organisms which contain lots of carbon; convert into coal and petroleum (fossil
fuels)
- Human activity (burning of fossil fuels, cutting, and burning forests)
2.
Nitrogen Cycle
- all organisms require nitrogen to make amino acids, which in turn are used to
build proteins
- certain types of bacteria which live in the soil and on the roots of plants convert
nitrogen gas into ammonia (nitrogen fixation)
- other bacteria convert ammonia into nitrates and nitrites
- producers use nitrates and nitrites to make proteins
- consumers eat producers and reuse the nitrogen to make their own proteins
- organisms die and decomposers return nitrogen to the soil as ammonia
- ammonia may be taken up again by producers
- other soil bacteria convert nitrates into nitrogen gas thus releasing nitrogen into
the atmosphere again (denitrification)
3. Phosphorus Cycle
- forms part pf DNA amd RNA
- remains mostly on land in rock and soil minerals, and ocean sediments
- plants absorb phosphate from the soil or from water, the plants bind the
phosphate into organic compounds