Ecology (Population & Community)

Question 1

What is species diversity?

Answer 1

Species diversity of a community is the variety of organisms that make up the community.

Question 2

What are the two components of species diversity?

Answer 2

1. Species richness
2. Relative abundance

Question 3

What is species richness?

Answer 3

The total number of different species in the community.

Question 4

What is relative abundance?

Answer 4

The proportion each species represents of the total individuals in the community.

Question 5

How can species diversity across communities be directly compared?

Answer 5

To directly compare species diversity across communities (in time or space), we can use indices of diversity, such as the Shannon diversity index (H).

Question 6

What do larger values in the Shannon diversity index indicate?

Answer 6

Larger values mean more diversity (greater evenness of species abundances).

Question 7

How is the Shannon diversity index calculated?

Answer 7

Multiply the relative abundance of species A by the natural log of that relative abundance and add this term to the same calculation done for each species. Then, the sum is multiplied by -1.

Question 8

How can microbial diversity be determined using molecular tools?

Answer 8

The number and abundance of the different sequences of a particular gene (e.g. ribosomal DNA) in a sample can be used to approximate the number and abundance of microbial species in a sample. Through PCR and sequencing samples from different microbial communities, we can estimate and compare their diversities.

Question 9

What are the characteristics of communities with higher diversity?

Answer 9

Communities with higher diversity are:
1. More productive (yield more biomass) and more stable in their productivity.
2. Better able to withstand and recover from environmental stresses.
3. More resistant to invasive species

Question 10

What is trophic structure?

Answer 10

The feeding relationships between organisms in a community–key for community structure.

Question 11

What is a food chain?

Answer 11

The transfer of energy up the trophic levels is referred to as a food chain.

Question 12

How can food webs be simplified?

Answer 12

1. Grouping species with similar trophic relationships into broad functional groups (e.g. phytoplankton)
2. Isolating portions of the web that do not interact much with the rest of the web.

Question 13

What is the energetic hypothesis?

Answer 13

The length of the food chain is limited by the inefficiency of energy transfer along the chain.

Question 14

About what amount of energy stored in the organic matter at one trophic level is converted to organic matter at the next trophic level?

Answer 14

Only about 10% of the energy. (e.g. 100 kg of plant material can support 10 kg of a herbivore and 1 kg of a carnivore)

Question 15

What are dominant species?

Answer 15

Those that are most abundant or have the highest biomass.

Question 16

What are keystone species?

Answer 16

Keystone species exert strong control on a community by their ecological roles, or niches (not necessarily abundant in the community).

Question 17

What are foundation species?

Answer 17

Foundation species exert their influence on the community by dramatically altering the physical environment.

Question 18

What is the traditional view of how biological communities establish equilibrium?

Answer 18

Most biological communities are in a state of equilibrium (“balance of nature” view). Community functions as an integrated unit. Following a disturbance, the community will bounce back.

Question 19

What is the current view of how biological communities establish equilibrium (non-equilibrium model)?

Answer 19

Most biological communities are chance assemblages of species, not integrated units. Following a disturbance, the community will change and not return to original state.

Question 20

What is a disturbance?

Answer 20

An event, such as a storm, fire, flood, drought, or human activity that changes a community by removing organisms from it or altering resource availability.

Question 21

What does the intermediate disturbance hypothesis suggest?

Answer 21

Moderate levels of disturbance can foster greater diversity than either high or low levels of disturbance. High levels of disturbance exclude many slow-growing species. Low levels allow dominant species to exclude less competitive species.

Question 22

What is ecological succession?

Answer 22

The sequence of community and ecosystem changes after a disturbance.

Question 23

What is succession?

Answer 23

The result of changes induced by the vegetation itself.

Question 24

What is primary succession?

Answer 24

Primary succession occurs where no soil exists when succession begins.

Question 25

What is secondary succession?

Answer 25

Secondary succession begins in an area where soil remains after a disturbance.