1

Mon. Tues. Wed. Thurs. Fri.

Week ofNov. 17

River ecology lab – dress for weather

LabExam(bring calc.)

Week ofNov. 24

No lab – Thanksgiving

Nolecture

Week ofDec. 1

Independent project presentations

Exam 3

Week ofDec. 8

FinalExam Dec. 11

2

Sp. interactions – 1718 (through fig. 18.7),1920 (only covering p. 391)

Community ecology – 2122

Don’t read 23,25, and 26 just yet

3

Structure of course

Environmental variability

Organisms

Ecosystems

Populations

Species interactions

Communities

Applied Ecological Issues

4

Communities

What is a community?

How are communities described?

How are species organized within a community?

How do communities change over time?

5

cod

seals

6

How are species organized within a community?

Webs!

Connectedness webs

Energy webs

Functional webs (interaction webs)(these are what we drew when talking

about species interactions)

7

Figure 21.12

8

Connectedness web

Starfish

Snail

Chitons Limpets Mussels Barnacles

9

Energy web

Starfish

Snail

Chitons Limpets Mussels Barnacles

10

Functional/interaction web

Starfish

Snail

Chitons Limpets Mussels Barnacles

11

How are species organized within a community?

Webs

Keystone species

Top-down vs. bottom-up

12

Keystone species – species that have large

impacts on structure of the community they

inhabit despite having relatively low biomass

13

Imp

act

of

spec

ies

Proportional biomass of species

14

Figure 21.15

bottom-up

top-down

Trophiccascade

What is size of trophic level determined by?

15

Bottom – up – increasing primary producer increases production at all levels

Top-down – increasing biomass of top consumerincreases production in every other level

16

Communities

What is a community?

How are communities described?

How are species organizedwithin a community?

How do communities change over time?

17

Succession – gradual change in plant and

animal communities in an area following a

disturbance or the creation of a new substrate

primary vs. secondary

18

Primary succession – occurs on new

geological substrates

Secondary succession – occurs after

destruction of aboveground community but

substrate is still intact

Examples??

19

Figure 22.2

20

New substrate

Climaxcommunity

Disturbed area

Multiplesuccessional

stages

Multiplesuccessional

stages

Primarysuccession

Secondarysuccession

21

Figure 22.9

22

Figure 22.5 Lake Michigan

23

Why does succession occur???

1. Organisms change environment during succession - how?

2. Organisms face trade-offs

24

Why does succession occur???

1. facilitation

2. inhibition

3. tolerance

Mechanisms for species establishment

25

Figure 22.11

26

Figure 22.10

27

Why does succession occur???

1. facilitation

2. inhibition

3. tolerance

Mechanisms for species establishment

28

Figure 22.13

29

Why does succession occur???

1. facilitation

2. inhibition

3. tolerance – establishment not dependent on which species are already there

Mechanisms for species establishment

30

31

1. Annual plants

2. Herbaceous perennials

3. Early sucessional trees/shrubs

4. Late successional trees

Succession on abandoned fields

32

Figure 22.12

toleranceinhibition