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Ecology > Chapter 16 > Flashcards

Chapter 16 Flashcards

1
Q

Define community

A

Group of species inhabiting a given area and interacting (directly or indirectly)

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2
Q

The concept of a community is _____. What does this mean?

A

spatial. The species all live in a particular place with a defined boundary

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3
Q

What are the 3 specific attributes of a community?

A

-species richness & relative abundance
-physical structure (usually defined by plant forms)
-species interactions

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4
Q

Define relative abundance

A

The proportion of individuals of 1 species relative to the total number of individuals of all the species

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5
Q

What is the relative abundance equation?
What do the variables mean?

A

p = n/N
p - proportion of individuals of species x
n - number of individuals of species x
N - total number of individuals of all species

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6
Q

What is a rank abundance diagram?

A

It plots rank abundance (x) against relative abundance (y). Provides information on 2 features of community structure and diversity (species richess and evenness)

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7
Q

What is rank abundance?

A

The species rank of abundance. On a diagram, it is ordered by the most abundant species to the least abundant species.

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8
Q

What is species richness?

A

(S). The number of species in the community

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9
Q

What is species evenness?

A

How equally individuals are distributed among the species

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10
Q

What can you interpret from the curves on a rank abundance diagram?

A

Steep curve: Indicates that a few species dominate - suggests low species evenness
Shallow/Flat curve: Species abundance is more even – suggests high species evenness
Curve length: number of points on the x-axis indicates species richness. A long curve suggests higher species richness.

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11
Q

What are the 2 components of species diversity in a community?

A

Species richness & species evenness

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12
Q

What is Simpson’s Diversity Index?

A

(D). Used to quantify biodiversity by taking into account species richness and evenness. It reflects the probability that 2 randomly selected individuals from a sample will belong to the same species.

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13
Q

What is the formula for Simpsons Index (D)?
What do the variables represent?

A

D = (sum total of)p^2
p = proportion of total individuals in a community represented by species 1
^^ remember relative abundance formula
Add together all the p^2 values to get the D-value

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14
Q

What can you interpret from the D value? Why is this the interpretation?

A

As D approaches 1, there is less diversity.
The probability of selecting the same species is higher = less species to choose from
As D approaches 0, there is more diversity.

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15
Q

What is Simpson’s Reciprocal Index Formula and interpretation?

A

1/D
Higher values = Higher diversity

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16
Q

What is Simpson’s Index of Diversity Formula and interpretation?

A

1-D
The likelihood that 2 individuals randomly chosen belong to different species.
A higher value means a higher likelihood that they belong to different species.

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17
Q

How can you calculate species evenness using the D-value? What do the variables mean? How can you interpret this?

A

ED = (1/D) / S
E(subscriptD) = value of evenness
S = species richness
The closer the value of evenness is to 1, the closer to equal abundance of species.
S is the maximum value of the index (since it is the amount of species present in a community)

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18
Q

Define the Shannon Index

A

A widely used index of diversity to consider species richness and evenness

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19
Q

What is the formula for the Shannon Index? What do the variables represent?

A

H = -(sum total of)(p)(LNp)
p = proportion of community made up of species x
n = number of individuals in species x
LN = natural log

20
Q

What are the minimum/maximum values of the Shannon Index?

A

Minimum = 0, where this only 1 species present
Maximum = lnS (natural log of S). This value shows all species in equal numbers.

21
Q

What does the maximum value of H for Shannon Index tell us?

A

It tells us what a community’s maximum potential diversity is, and allows us to see how close the actual community’s diversity is to this value.
Can set (H’) / (Hmax) to find species evenness

22
Q

What are dominants in a community?

A

Species that predominate within a community. Most often defined separately/in different groups within the community
ex. A community may have a dominant tree species and a dominant small mammal species.

23
Q

Does abundance sufficiently measure dominance?

A

No. Different species may have different relative abundance compared to relative biomass. It is better to define dominance by using a combination of different characteristics.

24
Q

What is a keystone species?

A

A species that has a disproportionate impact on the community relative to its abundance.They function in a unique/significant way within a community.

25
Q

What determines if something is a keystone species (2 factors):

A
  • their effect must be greater and disproportionate to their numerical abundance
    -Role may be to create/modify habitats or influence species interactions.
26
Q

What could the removal of a keystone species result in?

A

Changes in community structure and/or loss of biodiversity

27
Q

How can keystone herbivores modify the community?

A

By reducing certain plant density and creating habitats for smaller animals.

28
Q

What is a food chain?

A

Representation of feeding relationships within a community.

29
Q

Define primary producer

A

Photosynthetic organism. Forms base of the food web.

30
Q

Define primary consumer

A

Heterotroph. Transfers energy from the producers to the rest of the food web.

31
Q

Define a food web

A

Diagram that represents the interactions between predators and prey in a community. A mesh of different food webs.

32
Q

Define a link on a food web

A

Arrows from the consumed to the consumer

33
Q

Define a basal species

A

Autotrophs (A) that do NOT feed on other species but are fed on by other species

34
Q

Define an intermediate species.

A

Either Herbivores (H) or Carnivores (C). That feed on other species AND are the prey of other species.
Can also be an omnivore

35
Q

Define a top predator

A

(P) Feed on intermediate and sometimes basal species, but are NOT preyed upon.

36
Q

How many trophic interactions were found in a caribbean marine food web between how many species?

A

3313 trophic interactions aong 249 species.

37
Q

How was this food web compartmentalized to make it understandable?

A

They categorized all organisms into 5 compartments based on their:
1) differences in body size
2) range of prey sizes
3) shore VS off-shore habitat
4) associated predators.

38
Q

Do community dynamics only involve direct species interactions?

A

No. A predator can reduce competition between 2 prey species by keeping their population sizes below carrying capacity.

39
Q

Define autotroph

A

Primary producer. Derive energy from sunlight.

40
Q

Define heterotroph

A

Consumer. Derive energy from consuming plant and animal tissues.

41
Q

Define trophic levels

A

A functional classification that define groups of species based on the way they acquire their energy.

42
Q

Define guilds

A

A subdivision of trophic levels. Species in the same guild exploit a common resource in a similar way.

43
Q

What do guilds create the potential for?

A

Strong interactions between species in the same guild (as they are competing for the same resources), and weaker interactions with the rest of the community.

44
Q

What characteristics of a species’ groups them together as a functional type group (4)?

A
  • common responses to the environment
  • life history characteristics
  • role within the community
  • photosynthetic pathway/shade tollerance (PLANTS)
45
Q

How is the physical structure of a community influenced?

A

By abiotic and biotic factors

Ecology (20 decks)

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