chapter 10

Question 1

The number of species in a community is referred to as

Answer 1

species richness

Question 2

Assume that resources for a community of species are available on a continuum. A common species of bird utilizes a particular portion of this continuum. The term …………. defines the length of the portion of resources that this bird uses

Answer 2

“niche breadth”

Question 3

Large circular current in the middle of the ocean

Answer 3

gyre

Question 4

diversity within a community

Answer 4

Alpha diversity

Question 5

Environments that are dominated by an extreme abiotic factor such as temperature or acidity are often called

Answer 5

harsh environments

Question 6

the diversity between two different regions, each with many communities.

Answer 6

Gamma diversity

Question 7

Enrichment of a water body with plant nutrients

Answer 7

eutrophication

Question 8

a measure of atmospheric energy

Answer 8

Potential evapotranspiration

Question 9

the study of distribution of species and community composition on islands.

Answer 9

Island biogeography

Question 10

diversity between communities.

Answer 10

Beta diversity

Question 11

the general pattern of increase in species richness with increasing area of observation.

Answer 11

species area relationship

Question 12

bottom-dwelling organisms (in aquatic systems)

Answer 12

Benthic organisms

Question 13

Species richness can be influenced by climatic factors that vary spatially. The …………….. hypothesis explains how environmental temperature may affect a community of organisms

Answer 13

Energetic hypothesis

Question 14

The intermediate …………… hypothesis suggests that local species diversity is maximized when ecological disturbance is neither too rare nor too frequent.

Answer 14

disturbance hypothesis

Question 15

The …………. gradient in species richness refers to the increase in species richness if you move from the Arctic to the equator.

Answer 15

latitudinal gradient

Question 16

The equilibrium theory of island biogeography was developed by MacArthur and …………

Answer 16

Wilson

Question 17

Species richness

Answer 17

the number of species in a community

Question 18

Shannon-Weaver diversity index (H):

Answer 18

H = -ΣPilnPi

Where Pi: proportion of species i

Question 19

modelling species richness

Answer 19

Available resources (R)
Niche breadth (n)
Niche overlap (o)

Question 20

influences on species richness

Answer 20

• More species because greater range of resources (larger R)
• More species because each is more specialised (smaller n)
• More species because each overlaps more with its neighbours (larger o)
• More species because resource axis is more fully exploited

Question 21

What determines species richness?

Answer 21

1. Productivity and resource richness
2. Predator intensity
3. Spatial heterogeneity
4. Environmental harshness
5. Climate
6. Disturbance
7. Evolutionary history

Question 22

1. Productivity

Answer 22

• In most studies, diversity and productivity are related
• Productivity ~ available environmental energy

Question 23

productivity

PET

Answer 23

Potential evapotranspiration:
*the amount of water that could be evaporated and transpired if there was sufficient water available
* Represents crude atmospheric energy (Solar energy and wind energy)
* Unit: mm

Question 24

productivity

why would animal species richness be related to PET?

Answer 24

• Higher plant species richness → higher animal species richness
• Higher temperature → more efficient resource utilization → faster population growth → larger populations → species with narrow niches can persist

Question 25

Paradox of enrichment

Answer 25

* Agricultural runoff causes eutrophication of coral reefs * Species richness declines * Eutrophication of lakes leads to a decrease in species richness * Why would increased productivity lead to decreased species richness? * High productivity → rapid populatiopn growth → competitive exclusion

Question 26

# 2. Predation intensity Predator-mediated coexistence:

Answer 26

the predator provides a space for the competitively weaker species

Question 27

# 3. Spatial heterogeneity

Answer 27

* Heterogeneous environments can accommodate more species * E.g. hilly landcapes provide more niches (w.r.t. irradiance, moisture, wind, hiding places etc.) than flat landscapes

Question 28

# 4. Environmental harshness extreme conditions

Answer 28

Extreme” conditions: those that require a morphological structure or biochemical mechanism that is not found in most related species and that is costly

Question 29

5. Climate

Answer 29

* Seasonal cycles provide more different niches * More species might be expected to live in a seasonal environment, compared to a non-seasonal environment?? * Non-seasonal environments provide many opportunities for specialisation * More species might be expected to live in a nonseasonal environment, compared to a seasonal environment??

Question 30

# climate stable environments

Answer 30

* stable environments support speciallized species * Stable environments are more likely to be saturated with species * In stable environments, species are more likely to be excluded by competition

Question 31

# Disturbance Intermediate disturbance theory:

Answer 31

biodiversity is highest when disturbance is neither too rare nor too frequent

Question 32

Evolutionary history

Answer 32

“older” areas may be more saturated with species E.g. the tropics

Question 33

# Island biogeography Why does the immigration rate decrease?

Answer 33

* With increasing species number, the change of a new arrival will decrease * The number of free niches will decrease

Question 34

# island biogeography Why is the immigration rate larger at close or large islands ?

Answer 34

* Colonizers have a greater change of reaching an island that is close to the source * At large islands, the changes of an immigrant “hitting the target” are larger

Question 35

# Islanf biogeography Why does the extinction rate increase?

Answer 35

* As species arrive, competition for resources increases * As a results, average population size decreases * Small populations are vulnerable to random extinction events

Question 36

# Islanf biogeograohy Why is extinction rate larger at small islands?

Answer 36

* At small islands, populations will be smaller * Small populations are vulnerable to random extinction events

Question 37

# Island biogeography about remote islands

Answer 37

Many remote islands carry less species than they could support, because they have not reached equilibrium species richness yet

Question 38

# islanf biogeography large remote islands

Answer 38

In large, remote islands, speciation is a larger source of new species than immigration (s > E)

Question 39

Latitudinal gradients

Answer 39

Usually species richness decreases with latitude Possible explanations: * Specialized predators (Parasites) * Increased productivity * Lack of seasons * Greater evolutionary age * Past fragmentation * Higher mutation rate

Question 40

Gradients with altitude

Answer 40

* Usually species richness decreases with altitude * High altitude communities occupy smaller areas * Island effect * Less productivity * More seasonality

Question 41

Gradients with depth

Answer 41

* In lakes and oceans, species richness usually decreases with depth * However there are many exceptions * The proportion of undescribed species may be high in the deep sea

Question 42

Species richness during evolution

Answer 42

* Processes that explain current patterns in species richness may also be applied to evolutionary patterns in species richness * Possible explanation: Introduction of herbivory (by single celled protists) * E.g. Butterfield: introduction of moving predators speeds up evolution by a factor 10 * Extinction of large mammalian herbivores is strongly size-dependent * Extinction of large animals coincides with the arrival of humans