Chapter 13: Principles of Ecology

Honors Biology 2010-2011

What is Ecology?Eco comes from Greek word “oikos” –

house -logy comes from “logos” – study of Ecology means “study of the house” as

coined by Ernst Haeckel

Ecology – the study of interactions among organisms (plants and animals) and their environment

Levels of Organization (page 397 Figure 13.2)From individual to global: Organism—individual living thing (ex.

Lion)

Levels of OrganizationPopulation—group of same species that live in

one area (ex. Pride of lions)

Levels of OrganizationCommunity—collection of interacting

populations (ex. Lions, antelope, zebras, elephants, grasses, etc…)

Levels of OrganizationEcosystem—interactions of biotic and

abiotic factors in an areaBiotic factors—living or once living

things (ex. Animals, plants, microorganisms, etc…)

Abiotic factors—nonliving things (ex. Sunlight, temperature, soil, etc…)

Levels of OrganizationBiome—regional or global community of

organisms which is usually characterized by the climate conditions and plant communities that thrive there

Section 13.2In an ecosystem, each living thing depends

on an array of biotic factors and abiotic factors in the ultimate web of life.

A single change in that web can lead to minor or major changes.

A keystone species is one that has an unusually large effect on its ecosystem. (ex. Beaver) (ex. Killing too many deer during hunting season)

Section 13.3 Energy in Ecosystems (page 406)Autotrophs—“self feeder”Heterotrophs—“different feeder”

Producers —obtain energy from the sun (by photosynthesis pg 407) or chemicals (by chemosynthesis pg 407) and convert it to a useable form of energy (like food, sugar, carbohydrates)

What kind of feeders are these?

Section 13.3*All ecosystems depend on producers,

because they provide the basis for the ecosystem’s energy.

Consumers—get their energy by eating other living or once-living organisms (like autotrophs and/or other heterotrophs)

What kind of feeders are these?

Types of consumers: (page 409)Herbivores—obtain energy from eating

plantsOmnivores—obtain energy from eating

plants and animalsCarnivores—obtain energy from eating

animals

Types of ConsumersDetritivores—obtain energy from eating

detritus or dead organic material (ex. Earthworm)

Decomposers—obtain energy from breaking down organic matter (dead) into simpler molecules that can be more easily absorbed by decomposers and by other organisms

Why would they by important? Important in an ecosystem to return vital

nutrients back into the environment

Section 13.4 Food Chains and Food WebsTo show energy transfer between different

species, a food chain can be constructed. A food chain is a linear sequence that links

species by their feeding relationships. Matter and energy move through an ecosystem

by use of arrowsExample:

autotroph→heterotroph→decomposer*Heat energy is lost in each step

Trophic LevelsTrophic levels are the levels of nourishment

in a food chainExample: producer→herbivore→carnivore

Chain has 3 trophic levels

1st trophic level producer (base)2nd trophic level primary (1’) consumer

(herbivore), first order3rd trophic level secondary (2’) consumer

(omnivore/carnivore), second order4th trophic level tertiary (3’) consumer

(omnivore/ mostly carnivore), third order (top level)

Energy flows through an ecosystem in ONE direction

Food web- links all the food chains in an ecosystem

The stability of any food web depends on the presence of producers, as they form the base of the food web

Section 13.6 Pyramid ModelsEach level in the food chain contains much

less energy than the level below it. The sun continually pumps new energy into the system to continue life.

Only about 10% of the available energy is transferred to the next trophic level. Maximum number of organisms in a food chain is 5 because of energy loss.

Where does the rest of the energy go?

An energy pyramid compares energy used by producers, primary consumers, and other trophic levels (in units of kilocalories, kcal) see figure 13.17 on page 418

A biomass pyramid provides a picture of the mass of producers needed to support primary consumers, the mass of primary consumers required to support secondary consumers, and so on. 

A pyramid of numbers shows the numbers of individual organisms at each trophic level in an ecosystem.

Biomass pyramids and pyramids of numbers may occur in an inverted, or upside down formation. What might this indicate about that ecosystem?