2－Basics of Ecological

8/6/2019 2 Basics of Ecological

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Chapter 2Chapter 2Basics of EcologicalBasics of Ecological

The natural world is organized interrelated units called ecosystemThe natural world is organized interrelated units called ecosystem

LOGO

School of Life Science


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Contentsontentsontentsontents

Ecosystem andEcosystem and EcoenvironmentEcoenvironmentSection 1Section 1

Biological Community Structure and CharacteristicsBiological Community Structure and CharacteristicsSection 2Section 2

Ecological Factor andEcological Factor and EcologicalEcological EffectEffectSection 3Section 3

Section 4Section 4

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1. Ecosystem

atmosphere that surrounds it is much too complex to study at onetime. Even a single forest may cover thousands of square

ometers an conta n t ousan s o erent types o p ants ananimals living together. In order to separate these large systemsinto smaller areas that can be studied more precisely, ecologistswork with manageable units such as a hillside, a forested valley, alake, or a field.


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An ecosystem consists of all the different organisms living in

an area, as well as their physical environment. Because these alln erac w eac o er an c ange one ano er, e s u y oecosystem is a complex undertaking. We usually regard anecosystem as an isolated unit, but this is merely a useful

simplification. In reality, ecosystems always interact with oneanother. For instance, plants, animals, and materials move fromone ecosystem to another, as when soil and leaves wash from aforest into a lake, or birds migrate between their summer and winterhomes.


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.

of Ecosystem


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Producer

onsumer

Decomposer


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ProducerProducer

Environment Consumer

ecomposer


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. tructures o cosystem

( )

ecomoser


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Food ChainAs one organism feeds on another organism, energy flowsthrough the series. This is called a food chain .

Food WebWhen several food chains overlap and intersect , they make

up food web

ecomoser

Page 96-97


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Food Chain As one organism,

energy flows through the

series. This is called a foodchain. Pa e 97


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cavengers


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Parasites


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en severafood chains

overlap and,make up afood web


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Marine Ecosystems


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Lake Ecosystems


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50%

a/t/km 2 b/t/km 2 a/b

610 60 10

410 250 1.6


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. erac ca ruc ure o cosys em


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cell

n v ua

o ulation

community ( )


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(Density

m

1hm 2 350t


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Age structure/Age Distribution( )


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Age Distribution in Human Populations (Page 139)


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Sex ratio ( ) (Page 136)

The sex ratio refers to the relative numbers of malesand females .

Earthworm and most plants , have both kinds of sex organs in thesame body, sex ratio are no meaning for these species..

Monogamous species , a male and female pair up , mate and raisetheir young together.

Game animals the males are shot and the females are not.Social insect (bees, ants and wasps ), the number of femalesgreatly exceeds the number of males at all times, though most of thefemales are sterile.In humans , about 106 males are born for every 100 females, by thetime people reach their mid-twenties, a higher deathrate for maleshas equalized the sex ratio.


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Birth rate and death rate ( )


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Effect of Birthrate and Death Rate on Po ulation Size For a o ulation to row, thebirthrate must exceed the death rate for a period of time. These three human populations

illustrate how the combined effects of births and deaths would change population size ifbirthrates and deathrates were maintained for a five-year period .(Page 137)


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(2)Population Growth Curve

Populations have a inherent tendency to increase in size. However manyfactor influence the rate at which a population can grow.


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Inherent Growth Curve A

N dN/dt=rN


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J shape curve(J )


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A Typical Population GrowthCurve In this mousepopulation, these is littlegrowth during the lag phase.During the exponential growthphase , the population risesrapidly as increasing numbersof individual reachreproductive age. Eventually,the population reaches astable equilibrium phase ,

ur ng w c e r ra eequals the death rates.(Page 140)


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la hase)

exponential phase( )

Stable=

K

s(Logistic)


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Carrying Capacity A number offactors in the environment, suchas oxygen supply, food supply,diseases, predators, and space,determine the number oforganisms that can survive in agiven area---- the carrying capacityof that area. The environmentalfactors that limit populations areknown collectively asenvironmental resistance.

w en a popu a on con on orfactor can be identified as a keycomponent that limits the size of a

,

limiting factor .(Page 141)


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Carrying Capacity A number offactors in the environment, suchas oxygen supply, food supply,diseases, predators, and space,determine the number oforganisms that can survive in agiven area---- the carrying capacityof that area. The environmentalfactors that limit populations areknown collectively asenvironmental resistance.

w en a popu a on con on orfactor can be identified as a keycomponent that limits the size of a

,

limiting factor .(Page 141)


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Logistic Equation ( )

K K

N N/K

(1 N/K)


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(1 N/K)

N 0, 1,N K

N 0 K (1 N/K) 1

l/K

(N/K)

N0


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3. (Community)


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130

(species richness) (

Heterogeneity)


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dominant species


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(Positive association)

(negative association)


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Succession of Community

Primarysuccession

r mary success on s a success onaprogression that begins with a totallack of organisms and bare mineral

succession

Secondarysuccession

econ ary success on s muc morecommonly observed and generallyproceeds more rapidly ,because it

eg ns w e es ruc on ordisturbance of an existing ecosystem


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Terrestrial Primary Succession (page 109)


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Aquatic Primary Succession (page 111)

A shallow pond will fill slowly with organic matter from producers in the pond.Eventually a wet soil will form and grasses will become established. In many

areas, this be succeeded by a climax forest.


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Except for the oceans, most aquatic ecosystems areconsidered temporary. Certainly, some are going to be

,disappear and be replaced by terrestrial ecosystems as a

ecosystems receive a continuous input of soil particlesand organic matter from surrounding land, which resultsin the gradual filling in of shallow bodies of water likeponds and lakes.


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Secondary Succession from a Beaver Pond (page 112)

A colony of beavers can dam up streams and kill trees by the flooding

that occurs and by using trees for food. Once the site is abandoned, it willslowly return to the original forest community by a process of succession.


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1. Ecological Effect of Main Ecological Factors


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(2)Sunlight and Radiation

( ) (


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(4)Air

CO 2

2

CO 2


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(5)Soil


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2.Common Characteristics of Ecological Factors

(1)

(3)


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3.Mode of Ecological Factor Effect

(1)


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(3)


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4.Laws of Ecological Factor Effect


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limiting Factors In aquatic habitats, the amount of oxygen dissolved in

the water is often a limiting factor for many species of fish. Cool, highly

oxygenated water, which is typical of the rapidly flowing upper sections of

a river system, supports trout, but warmer, less oxygenated water is

unsu e or rou . er s , w c are more o eran o ow eve s o

oxygen, such as bass, catfish, bullheads, and carp, occupy the lower, , ,

river contains silt and other soil particles. Each of these species has a

s ecific ran e of tolerance to ox en concentrations and water

temperatures . Thus, low levels of oxygen and high temperatures are

limiting factors for the distribution of trout. (Page 84-85)


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(2)


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1. Organism Production


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( )

P G

P NG a N G a N a


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2. Energy Flow through Ecosystem

(1)

20. cm m n

46

1


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A.

1

.

C.

10%

90%Lindeman

10%


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Energy Flow Through an Ecosystem As energy flows through anecosystem, it passes through several levels known as trophic levels . Eachtrophic level, approximately 90% percent of the useful energy is lost , usuallyas heat to the surroundings. Therefore, in most ecosystems, higher trophiclevels contain less energy and fewer organisms .(page 96)


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Second Law of Thermodynamics Whenever energy is converted from one formto another , some useful energy is lost, usually in the form of heat. The conversionof fuel to electricit roduces heat which is lost to atmos here. As the electricitmoves through the wire, resistance generates some additional heat. When theelectricity is converted to light bulb, heat is produce as well. All of these steps

produce low quality heat in accordance with the second law ofthermodynamics .(page 77)


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3.Material Cycles in Ecosystem

(1)


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Carbon Cycle(Page 100)


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Nitrogen Cycle

(Page 102)


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Phosphorus Cycle(Page 103)


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e ows o a oms roug an ecosys em nvo ves a e organ smsin the community. The carbon, nitrogen, and phosphorus cycles areexamples of how these materials are cycles in ecosystem.A population is a group of organisms of the same species thatinhabits an area.

and death rate. Most organisms have a biotic potential much greaterthan that needed to replace dying organisms.Interactions among individuals in a population, such as competition,predations and parasitism, are also important in determiningpopulation size.

A typical population growth curve shows a lag phase followed by anexponential growth phase and a stable equilibrium phase at the

.limiting factors that are collectively known as environmental

resistance.


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.2.3. 4.

5.

6.7.

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2－Basics of Ecological