Ecology Unit Notes

Ecology is the study of the interactions of organisms with each other and their environment

A key theme of ecology is “Everything is connected to everything else.”

This is also referred to as interconnectedness or interdependence

Why should scientists study ecology in the first place?

“We’ve made some big mistakes in the past”

Examples: DDT use, extinction of many species, contamination of groundwater, destruction of the ozone layer, global warming; Others??

There are three research methods used in the study of ecology:

Observation: We have to know what the heck is going on out there!

Experiment: Let’s test our ideas!

Models: Models help us understand the environment around us. A greenhouse is an ecological model, the aquarium is a “model” of the school pond, there are mathematical models of how populations grow, etc.

Key ecology terms:

1. population = all the individuals of a species that live together in one place at one time. Characteristics of populations include pop. size and density.

Population Densities of selected countries (2004 estimates)

Country

/ Population / Area (km2) / Density (#/km2)
Australia / 19,913,144 / 7,686,850 / 2.6
Mexico / 104,959,594 / 1,972,550 / 53.2
The Bahamas / 299,697 / 13,940 / 21.5
Brazil / 184,101,109 / 8,511,965 / 21.6
Lithuania / 3,607,899 / 65,200 / 55.3
U. S. / 293,027,571 / 9,629,091 / 30.4

Growth Rates of selected countries (2004 data)

Country / Birth Rate / Death Rate / Growth Rate
U. S. / 14.1 / 8.3 / 5.8
Germany / 8.4 / 10.4 / -2.0
Italy / 9.1 / 10.2 / -1.1
France / 12.3 / 9.1 / 3.2
Population: / 7,781 / Land Area: / 4.10 miles2
Population Density: / 1,895.50 per mi2

Plymouth’s Population Density740 per km2

2. habitat = the location where a population lives

3. community = the sum of all the populations living together in a habitat

4. abiotic factors = the physical aspects of a habitat (soil, water, climate)

5. biotic factors = the living aspects of a habitat

6. ecosystem = (community + habitat) or (abiotic + biotic factors)

The flow of energy is the most important factor that controls what kinds of organisms live in an ecosystem

A. Producers capture light energy by photosynthesis (usually plants). An exception to this is the chemosynthetic bacteria.

B. Consumers are all of the other organisms in an ecosystem.

Food Web in a coniferous forest

Energy Pyramid in a coniferous forest

B. Trophic levels are the relative feeding positions for each population in an ecosystem

  • food chains illustrate the path of energy through the trophic levels of an ecosystem
  • Producers are at the base, or lowest level, of food chains
  • herbivores are consumers that eat producers, and are at the second level of food chains
  • carnivores are consumers that eat other consumers, and are at the third or higher level of food chains
  • detritivores obtain energy by ingesting organic wastes and dead bodies of other organisms
  • decomposers obtain energy by absorbing organic wastes and dead bodies of other organisms
  • food webs are the complicated, interconnected group of food chains in an ecosystem

II. Energy is lost in a food chain

A. During every transfer of energy within an ecosystem, energy is lost as heat

  • energy transfer, the energy from one trophic level that is captured by the next trophic level, is often about 10%
  • 90% of the energy in a trophic level is lost to the environment

B. Pyramids of energy illustrate the flow of energy through ecosystems

  • the quantity of energy in each trophic level is represented by a block
  • the blocks are stacked on top of each other, forming a pyramid

C. Trophic levels are limited to 3, 4 or sometimes 5

  • the major food produced by humans are grains: rice, wheat, corn
  • eating primarily grains, consuming at the 2nd trophic level, feeds many more people since so much more energy is available
  • eating large quantities of meat, consuming at the 3rd trophic level, feed far fewer people since so much energy (90%) is lost in the energy transfer from grains to farm animals
  • pyramids of the number of organisms in trophic levels are also used to describe ecosystems
  • pyramids of the biomass (the dry weight of organic matter) of organisms in trophic levels are

Biogeochemical Cycles


Water cycle (precipitation, evaporation, condensation)

Nitrogen cycle (N2 GAS, NO2, NH4) role of bacteria


Carbon cycle

(emphasis on the cellular respiration and photosynthesis connection)


Global Warming

Global warming sites

Graph 1

Graph 2

“Anti”- global warming article

Greenhouse effect: A “normal “ part of the Earth’s dynamics. Benefit: keeps the earth at a stable temperature.

Global Warming: An increased greenhouse effect caused by an increase in CO2 gases in the atmosphere. Major contributor to the increase in CO2 gases is the burning of fossil fuels.

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Now, for a totally different topic:

The Hole in the Ozone Layer!

Ozone functions to block UV rays, preventing damage to DNA – damage to DNA can lead to mutations, which can lead to skin cancer.

Formation of Ozone

Why is there a hole in the ozone layer? CFC’s (chlorofluorocarbons) found in aerosol cans and some manufacturing processes destroy natural ozone.

THE HOLE