Ecology

Ecology and Interdependence

Ecology is the study of the interactions between organisms and their environment.◦ Interdependence is a key

theme found throughout ecology.

◦ Living things depend on each other in complex ways for survival.

◦ Ecological models can be used to study this complexity.

Levels of Organization The hierarchy of environmental

organization from largest to smallest is: Biosphere, Ecosystems, Communities, Populations, and Organisms.◦ Biosphere —thin zone of the Earth that

supports life.◦ Ecosystem —all living and nonliving

parts of an ecosystem Biotic factors—living organisms Abiotic factors—nonliving parts.

Communities and Populations

◦Community—all the organisms living in a certain area.

Example: pond community◦Population—all the

organisms of the same species living in the same area.

Example: frogs in a pond

Strategies for Tolerance Two strategies exist to deal with fluctuations

in environments. ◦ Conformers—organisms who do not regulate

their internal conditions; they change with the environment. Ex: ectothermic animals

◦ Regulators—organisms that use energy to control some of their internal conditions.

Ex: endothermic animals

Escaping Unfavorable Conditions Sometimes, adjusting isn’t possible and

organisms must temporarily escape.Ex: Lizard hiding in the shade

Seed dormancy or animal hibernation Migration

Sunlight is the main source of energy in most ecosystems

Energy flows from sunlight through producers (make food) and consumers (eat food)

Energy and the Environment

Types of Producers Photoautotrophs—

use solar energy (photosynthesis) to produce sugar

Chemoautotrophs—use energy stored in inorganic molecules (chemosynthesis) to produce carbohydrates

Consumers Consumers—get food by

eating other organisms or organic wastes. (Heterotrophs)

Four types:

Herbivores—eat producers

Carnivores—eat other consumersOmnivores—eat producers and consumers

Detritivores--feed on “wastes” (dead plants, animal wastes, and dead animal carcasses.) ◦ A few are specifically classified as decomposers

because they cause decay and return important nutrients to the soil.

DetritivoresDecomposing Detritivores

Energy Flow

Energy flow through an ecosystem can be illustrated using trophic levels (shows an organism’s position in a sequence of energy transfers)

1st level = producers 2nd level = herbivores 3rd and higher levels =

predators

Consumers are also grouped into feeding or trophic levels according to the foods they eat.

Many organisms feed at more than one level, especially omnivores.

C1—first level consumers: eat plants

C2—second level consumers: eat C1 consumers

C3—third level consumers: eat C2 consumers

C1 C2

C3

A food chain is a model of the flow of energy through theOrganisms of an ecosystem.

Food Webs Food web —many food

chains combine to form a food web.

Gives more information.◦ The members can be

identified by their trophic level.

◦ Many organisms function on more than one trophic level. Which is a producer?

Which are C1 consumers?Which are C2 consumers?Which is a C3 consumer?Which is a C4 consumer?

A complex food web from an aquatic ecosystem

Energy Pyramid An energy pyramids --show

how the amount of energy available decreases at each level of the food chain.

Cycles in Nature

Many of the abiotic factors in an ecosystem pass through cycles that allow the substances to be used and reused.

Four important cycles of abiotic substances include:◦ Water cycle◦ Carbon cycle◦ Nitrogen cycle◦ Phosphorus cycle

Water Cycle Water passes through both living and

nonliving parts of the environment. The water cycle is maintained by evaporation, transpiration, condensation and precipitation.

Carbon Cycle Photosynthesis and cellular respiration

form the basis of the carbon cycle. In the past 150 years, atmospheric carbon

dioxide has risen more than 30%..mostly due to the burning of fossil fuels

Nitrogen Cycle Air is 78% nitrogen gas. Most organisms cannot use nitrogen in

this form. Nitrogen-fixing bacteria change nitrogen gas into nitrates which

can be used by living things to make proteins and nucleic acids. ◦ Live in the soil and on the roots of certain plants (beans, peas,

clover and alfalfa). ◦ Receive carbohydrates from plants and produce nitrogen for

plants ◦ Release extra nitrogen into the soil.

Decomposers--make the nitrogen from decaying organisms and wastes available in the soil by turning it to ammonia (NH3) which changes in the soil to ammonium (NH4

+) in a process called ammonification.

Soil bacteria turns ammonium into nitrites (NO2-) and nitrates

(NO3-) in a process called nitrification. Plants can use the nitrates

and then animals can eat the plants. Anaerobic bacteria return nitrogen to the air by breaking down

soil nitrates in the process of denitrification.

Phosphorus Cycle Phosphorus is necessary for healthy bones, teeth, and the

formation of DNA and RNA. The erosion of rocks is important in adding phosphorus to

the soil and water. Excreted wastes and decaying organisms also add

phosphorus to soil and water. Plants absorb phosphorus. Animals get phosphorus from

plants.