Community Ecology (W11)

Question 1

List of Models that explain the nature of communities? (2)

Answer 1

• Organismic model.
• Individualistic model.

Question 2

Organismic model attributes? (3)

Answer 2

• Plant communities are closely integrated systems with numerous “emergent properties”, and are analogous to a “super-organism”.

• Communities function as an organism & ultimately mature (climax community).

• Climatic climax communities.

Question 3

Individualistic model attributes? (6)

Answer 3

• Emphasises species individuality with each having its Abiotic living requirements.

• Communities are there by chance.

• Don’t function as an organism.

• Chance occurrence of species that have similar ecological requirements.

• Emphasises environmental gradient nature of communities.

• Juxtaposition of individuals of the same/different species.

Question 4

Explain Organismic model graph?

Question 5

Explain Individualistic model?

Question 6

Succession?

Answer 6

= the evolution of community structure over time leading to a stable community.

Question 7

Succession attribute?

Answer 7

Communities develop gradually during this process.

Question 8

Types of succession? (2)

Answer 8

• Primary succession.
• Secondary succession.

Question 9

Primary succession?

Answer 9

= occurs in a lifeless area (soil-forming processes with no seed bank or reserve for vegetative propagules in the substrate).

Question 10

Secondary succession?

Answer 10

= occurs in areas after disturbances (small-scale disturbancessuch as fire in grasslands, or flooding event).

Question 11

Primary succession process?

Question 12

Secondary succession process?

Question 13

Paper to read for Observed patterns of succession?

Answer 13

Olivier et al, 2012.

Question 14

Mechanisms fo plant succession? (3)

Answer 14

• Facilitation hypothesis.
• Tolerance hypothesis.
• Inhibition hypothesis.

Question 15

Facilitation hypothesis?

Answer 15

= early species prepare ground for later species.

Question 16

Tolerance hypothesis?

Answer 16

= early species modify the environment, but it does not affect the recruitment & growth of later species.

Question 17

Inhibition hypothesis?

Answer 17

= early colonists secure the space/resources & thus inhibit the invasion of subsequent colonists.

Question 18

Resource Ratio model of succession attributes? (2)

Answer 18

● Assumes that each plant species is a superior competitor for a particular proportion of the limiting resources.

● Predicts that community composition should change whenever the relative availability of two or more limiting resources changes.

Question 19

Disturbance?

Answer 19

= events that change the biological communities by removal of nutrients.

Question 20

Disturbance attribute?

Answer 20

Influences succession & species richness.

Question 21

Explain how Disturbance influences succession & species richness? (2)

Answer 21

• Low disturbance, late successional species dominate.

• High disturbance, allows early successional species to persist.

Question 22

Hypothesis for Disturbance?

Answer 22

Intermediate disturbance hypothesis (IDH).

Question 23

Explain Intermediate disturbance hypothesis graph? (6)

Answer 23

● x-axis = disturbance frequency and/or amplitude.

● y-axis = species diversity.

● Dotted line = exponential decrease.

● Dashed line = exponential increase.

● Solid upside down U.

● All lines cross each other.

Question 24

Explain IDH graph:

Dotted line? (4)

Answer 24

• Low DEM (growth rate).
• Low disturbance at high point.
• Starts at y axis.
• Ends at tip of solid upside-down U.

Question 25

Explain IDH graph: Dashed line? (4)

Answer 25

• High DEM (growth rate). • High disturbance. • Starts at tip of solid line (left). • Ends at right.

Question 26

Explain IDH graph: Solid upside-down U line? (3)

Answer 26

• Intermediate growth rate (IDH = DEM). • Moderate disturbance. • High species richness.

Question 27

Explain The IDH & Plant invasion graph? (6)

Answer 27

● x-axis = ¹ disturbance frequency (low to very high). ² strength of competition (high to very low-left to right). ● y-axis = species diversity (low to high- bottom to top). ● Two graphs that why you have 2 x-axes. ● Light line = historical disturbance gradient. ● Dark line = human disturbance. ● Dashed line = diversity of an alien plant in high disturbance.

Question 28

Hypothesis relating to Invasive species?

Answer 28

The Invasibility theory.

Question 29

Invasibility theory?

Answer 29

= a plant community becomes more susceptible to invasion wherever there is an increase in the number of unused resources.

Question 30

Invasibility?

Answer 30

= the susceptibility of an environment to invasion by non-resident species.

Question 31

Invasibility theory attributes? (2)

Answer 31

• Agrees with Gleason's idea of the nature of a community. • Fargione & Tilman, 2005.

Question 32

Interactions among communities?

Answer 32

= when members in a community engage in interspecific interactions.

Question 33

Interspecific interactions?

Answer 33

= relationships with individuals of other species in a community.

Question 34

Interspecific interactions attribute?

Answer 34

May have a helpful or harmful impact.

Question 35

Interspecific competition?

Answer 35

= negative interaction between two or more species in the same guild or trophic level.

Question 36

Interspecific competition attribute?

Answer 36

Manifests itself to reduce abundance & fitness of the other species.

Question 37

Why does interspecific competition manifest? (2)

Answer 37

• To reduce the abundance of the species. • To reduce the fitness of the other species.

Question 38

Competition?

Answer 38

= occurs when two or more species want to use the same resource at once.

Question 39

Competitive exclusion hypothesis?

Answer 39

= when competition between between species with overlapping niche may lead to competitive exclusion.

Question 40

Competitive exclusion person?

Answer 40

Gause.

Question 41

Mechanisms of interspecific competition person?

Answer 41

Schoener.

Question 42

Mechanisms of interspecific competition? (6) [COPATE]

Answer 42

• Consumption. • Overgrowth. • Preemption. • Allelopathy. • Territoriality. • Encounter competition.

Question 43

Consumption?

Answer 43

=

Question 44

Eg of Consumption?

Answer 44

Competition between granivorous rodents & ants for seeds.

Question 45

Overgrowth?

Answer 45

= when one organism grows directly over another, with or without physically contacting the other organism.

Question 46

Preemption?

Answer 46

= occurs when a physical resource, like an open space required for settlement, is occupied by one organism & made unavailable to others.

Question 47

Where does Preemption occur?

Answer 47

Among sensible organisms.

Question 48

Eg of Overgrowth?

Question 49

Eg of Preemption?

Question 50

Allelopathy?

Answer 50

= interaction using chemicals which allow a plant to compete better in an environment.

Question 51

Eg of Allelopathy?

Answer 51

Invasive plants (Lantana).

Question 52

Territoriality?

Answer 52

= results from the aggressive behavioural exclusion of organisms from specific units of space that are defended as territories.

Question 53

Eg of Territoriality?

Answer 53

Lions.

Question 54

Encounter competition?

Answer 54

= occurs when non-territorial encounters between foraging individuals result in negative effects on one or both of the interacting individuals.

Question 55

Eg of Encounter competition?

Question 56

Adaptations to reduce competition? (2)

Answer 56

• Resource partitioning. • Character displacement.

Question 57

Resource partitioning?

Answer 57

= natural selection that will force competitors to use resource differently.

Question 58

Resource partitioning attribute?

Answer 58

It's a way to avoid competition between species & allow for coexistence.

Question 59

Egs of Resource partitioning? (3)

Answer 59

• Warbler birds in trees. • Plant roots. • Anolis lizards.

Question 60

Explain Warbler birds in the tree?

Answer 60

Where the different warbler birds use different sections of the tree to avoid competition.

Question 61

Explain Plant roots? (2)

Answer 61

● Relates to varying soil depths. ● Smart weed roots (deep); Indian mallow roots (middle) & Bristly foxtail roots (shallow).

Question 62

Explain Anolis lizards? (3)

Answer 62

● Dominican Republic lizards occupy different preferred porches. ● One on perches on shady branches (A. insolitus). ● One on fence posts & other sunny surfaces (A. distichus).

Question 63

Character displacement?

Answer 63

= trait evolution stemming from selection to lessen resource competition between species.

Question 64

Character displacement attribute?

Answer 64

Acts on traits associated with resource use.

Question 65

Egs of Character displacement? (3)

Answer 65

• Morphological structures such as beaks & jaws. • Galapagos finches. • Mussels (barnacles).

Question 66

Explain Galapagos finches?

Answer 66

Initially, one finch from Los Hermanos with a small beak and one from Daphne Major islands with a large beak occur separately (allopatric) but when both occur in the same area, San Cristobal islands (sympatric), the former develops a smaller beak size than before & the latter one develops a larger beak than before.

Question 67

Explain Mussels (barnacles)? (2)

Answer 67

● Niche separation in space. ● Chthalamus & Semibalanus, where the former is higher up (dominant) in the tide, while the latter is lower down (dominant) in the tide.

Question 68

Fundamental niche?

Answer 68

= conditions & resources that are available to an organism in the absence of interaction with other organisms.

Question 69

Realized niche?

Answer 69

= conditions & resources that are available to an organism in the presence of interacting species (competitors & predators).

Question 70

Fundamental niche is AKA?

Answer 70

Where they CAN occur.

Question 71

Realized niche is AKA?

Answer 71

Where they CHOOSE to occur.