Ecosystems: Concepts and FundamentalsChapter 6

6.1 The Ecosystem: Sustaining Life on Earth

• Ecosystem: a ecological community of living and non-living attributes. It is the minimum system that includes and sustains life.

6.1 The Ecosystem: Sustaining Life on Earth•Ecosystems have two major parts: living and nonliving•Ecological community: the living part of the ecosystem

6.1 The Ecosystem: Sustaining Life on Earth

• Two major functions in an ecosystem: • Cycling of chemical elements• Flow of energy• Ecosystems include some sort of fluid

medium (air, water, both)•We will learn about cycling of chemical

elements in the next chapter.

6.1 The Ecosystem: Sustaining Life on Earth

• Cycle: wastes are converted into food, which is converted into wastes, which must be converted once again into food, etc.• For this to take place, many species have

to interact with each other• The simplest ecosystem has one species

that produces its own food and another that decomposes the waste of the first species and a fluid medium

6.2: Ecological Communities and Food Chains

• Food chains: The linkage of who feeds on whom• Food webs: more complex linkages• Trophic level: all organisms in a food web

that are the same number of feeding levels away from the original energy source

6.2: Ecological Communities and Food Chains

• Photosynthesis: process of using sunlight to create food• Autotrophs: an organism that produces its

own food• Heterotrophs: Organism that cannot make

its own food so it lives by feeding on another

6.2: Ecological Communities and Food Chains• Herbivores: an organism that feeds on an

autotroph• Carnivores: Eat heterotrophs• Omnivores: Eat both autotrophs and

other heterotrophs

6.2: Ecological Communities and Food Chains

• Ex: Yellowstone National Park (Wyoming) – geyser basins• Photosynthetic bacteria and algae make

up the spring’s first trophic level.

6.2: Ecological Communities and Food Chains• Ephydrid flies (herbivore) make up the

second trophic level• Dolichopodid fly: feeds on the eggs and

larvae of the ephydrid flies (carnivore)

6.2: Ecological Communities and Food Chains

• Ex: Yellowstone National Park (Wyoming) – geyser basins• The herbivorous ephydrid flies have

parasites, so they would be on the third trophic level• Decomposers would be the fourth

trophic level, because they feed on all of the dead wastes

6.2: Ecological Communities and Food Chains

• Ex: Yellowstone National Park (Wyoming) – geyser basins• The community is dependent on

1. Sunlight2. Constant flow of hot water

• Without these, they cannot survive.

6.2: Ecological Communities and Food Chains

• Case Study: Sea Otters• Keystone species: if this species declines,

the whole ecosystem falls apart.

6.2: Ecological Communities and Food Chains• Food webs in the oceans generally involve

more species.• Pelagic ecosystem (open ocean ecosystem)• In the hot springs example, the food webs

and trophic levels were neat. In reality, this is not true • Ex: harp seal (see figure)

6.2: Ecological Communities and Food Chains

6.3 Ecosystems as Systems

• Ecosystems are open systems: energy and matter flow into and out of them• Where does an ecosystem start and where does

it end?• Commonly used way of determining where a

boundary of an ecosystem on land is is the watershed.• All rain that reaches the ground from any

source and flows out into one stream.

6.4 Biological Production and Ecosystem Energy Flow• Ecosystem energy flow: movement of

energy through an ecosystem from the external environment• The issue is that energy is a difficult and

abstract concept. It is invisible to us and especially hard to measure with ecosystems

6.4 Biological Production and Ecosystem Energy Flow•What limits the amount of organic matter in living things?•Entropy: there is a decrease in order, and energy is disorganized

6.5 Biological Production and Biomass• Biomass: total amount of organic matter in any

ecosystem• Biological production: capture of usable energy

from the environment to produce organic matter• Gross production: the increase in stored energy

before any is used• Net production: the amount of newly acquired

energy stored after some energy has been used.

6.5 Biological Production and Biomass• Primary production: production carried out by

autotrophs• Secondary production: the production carried

out by heterotrophs• Chemoautotrophs: organisms that create energy

from chemicals

6.6 Energy Efficiency and Transfer Efficiency• No system can be 100% efficient.• Energy efficiency: ratio of output to input,

and is usually further defined as the amount of useful work obtained from some amount of available energy

6.7 Ecological Stability and Succession• Ecosystems change and recover and overcome these changes• Ecological succession: the process of ecosystems recovering

6.7 Ecological Stability and Succession

6.7 Ecological Stability and Succession

6.7 Ecological Stability and Succession

6.7 Ecological Stability and Succession

6.7 Ecological Stability and Succession

6.7 Ecological Stability and Succession

6.8 Chemical Cycling and Succession

6.8 Chemical Cycling and Succession

6.8 Chemical Cycling and Succession

6.8 Chemical Cycling and Succession

6.8 Chemical Cycling and Succession

6.8 Chemical Cycling and Succession

6.8 Chemical Cycling and Succession

6.8 Chemical Cycling and Succession

6.9 How Species Change Succession

6.9 How Species Change Succession

6.9 How Species Change Succession

6.9 How Species Change Succession