1

Mon. Tues. Wed. Thurs. Fri.

Week ofNov. 10

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

2

Ecology does not roll over into Genetics

Last chance to take Genetics.

3

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

Community ecology – 2122

4

Structure of course

Environmental variability

Organisms

Ecosystems

Populations

Species interactions

Communities

Applied Ecological Issues

5

+

+

Mutualistic interactions

A B

6

Different types of mutualisms

1. Those involving energy, nutrients, and/or water

(Trophic mutualisms) Examples?

2. Those involving defense(Defensive mutualisms) Examples?

3. Those involving dispersal(Dispersive mutualisms) Examples?

7

Lichens

8

Obligate mutualism – species are so dependent

on each other that they cannot live without each

other

9

Acacia trees andacacia ants

10

Trees withoutants

Treeswithants

% o

f sh

oo

ts w

ith

her

biv

ore

s o

n t

hem

11

May25

June16

Aug.03

Aca

cia

hei

gh

t (c

m)

0

120

60

12

Which are more general? seed dispersal or pollination mutualisms

13

Figure 20.16

14

Structure of course

Environmental variability

Organisms

Ecosystems

Populations

Species interactions

Communities

Applied Ecological Issues

15

Communities

What is a community?

How are communities described?

How are species organized within a community?

How do communities change over time?

16

Community: an association of populations of

different species living in a particular area

Community ecology: focus is understanding the

diversity and relative abundance of species in

the community

17

Questions asked by community ecologists

What determines the number of species in a community?

How does disturbance affect community structure?

Does adding new species change the way a community functions?

18

19

Figure 21.6a

Ecotone- zone oftransition between 2 distinct communities

20

Figure 21.9 boundaries less distinct

21

Communities

What is a community?

How are communities described?

How are species organizedwithin a community?

How do communities change over time and space?

22

How are communities described?

number of species = species richness

evenness = # individuals/species

diversity = richness and evenness

relative abundance

23

Figure 21.18

Relative abundance

fewdominant

many rare

24

5 specieshigh evenness

5 specieslower evenness

25

Diversity = combination of richness and evenness

- contribution of species weightedby relative abundance

26

5 specieshigh evenness

5 specieslower evenness

Which hashigher diversity?

27

What determines diversity of a community?

28

What determines diversity of a community?

1. diversity is related to area

2. diversity is related to variability

Lots of other theories that attempt to explain controls on diversity

29

Figure 21.20

one of the mostcommon patterns in ecology

30

What determines diversity of a community?

1. diversity is related to area

2. diversity is related to variability

Lots of other theories that attempt to explain controls on diversity

31

Figure 23.5

32

Hard to separate variability and area - typically larger areas have more habitat variability

Lesser Antilles – island size and habitat diversity vary independently

- two kinds of islands- tall volcanic – diverse habitats- low raised seabed – 1 habitat

- both kinds of islands come in all sizes

33

Figure 21.21

34

Communities

What is a community?

How are communities decribed?

How are species organizedwithin a community?

How do communities change over time?

35

How are species organized within a community?

36

Suppose there are 3 species in a community,

species A, B, and C. When you remove

species A from the community, species C

goes extinct. What can you conclude

about the relationship between species?

a. Species A is a predator of species B.

b. Species A is a prey of species C.

c. Species B is a competitor of species C.

d. All of these are possible.

37

Figure 21.12

38

Connectedness web

Starfish

Snail

Chitons Limpets Mussels Barnacles

39

Energy web

Starfish

Snail

Chitons Limpets Mussels Barnacles

40

Functional/interaction web

Starfish

Snail

Chitons Limpets Mussels Barnacles