Coexistence, Biodiversity + Ecosystem Services

Question 1

What is the paradox of the plankton

Answer 1

how is it possible for many species to coexist in an unstructured population while all competing for the same resources

Question 2

What is interference competition vs. exploitation/scramble competition

Answer 2

interference = direct competition (ex. fighting)
exploitation = indirect competition by depleting shared limited resources

Question 3

What does it mean that competition is often considered antithetical to coexistence

Answer 3

species on their own can survive, but when species are both present together they are not able to both coexist, it is the opposite of coexistence

Question 4

What is Gause’s Competitive Exclusion Principle

Answer 4

where 2 species compete for the same limiting factor, they cannot coexist and only one species will persist

Question 5

Define ecological niche

Answer 5

the species abiotic and biotic environment that it can tolerate

Question 6

As niches become more similar between competing species, how does it affect competitive exclusion and coexistence

Answer 6

competitive exclusion increase
coexistence decreases

Question 7

What 3 reasons allow for species coexistence in light of the competitive exclusion principle

Answer 7

1. resource partitioning
2. importance of influential species
3. disturbance

Question 8

What is resource partitioning

Answer 8

if species niches are sufficiently different and not overlapping, the species may be able to coexist despite competition

Question 9

Explain the example of warblers as resource partitioning

Answer 9

individuals of different species forage for food on the same tree, BUT specialize on different branch heights

Question 10

Explain the example of cutthroat trout and dolly varden charr as resource partitioning

Answer 10

when found together, dolly varden charr do not utilize the bottom-dwelling food compared to when the trout are absent, they do.

Question 11

Evolution can lead to greater partitioning via ____. How?

Answer 11

character displacement
an evolutionary divergence of niche traits. the individuals are selected for on the opposite “sides” of the niches

Question 12

Explain character displacement in darwin’s finches

Answer 12

when found alone, one species had small beaks, the other had medium.
found together, the medium then evolved to have much larger so the character displacement increased

Question 13

What are the two categories of “species” that have a greater influence on their community than others

Answer 13

1. dominant species
2. keystone species

Question 14

Define dominant species

Answer 14

species that have greater abundance/biomass compared to other species and exert influence because of the fact that they are so large

Question 15

Example of a dominant species

Answer 15

giant kelp

Question 16

What allows a species to dominate

Answer 16

1. effective competitors (they are able to successfully out compete others) ex. sugar maples that effectively shade others, but also tolerate shade and grow quickly is possible
2. resistant of natural enemies ex. can grasses dominate if unpalatable to grazers and if chosen to not be eaten

Question 17

Define keystone species

Answer 17

species that exert a strong influence on their community even though they don’t dominate and often promote biodiversity

Question 18

Explain ochre stars as a keystone species

Answer 18

in an experiment, the removal of sea stars caused the mussels to dominate and take up to 60-80% of the space

Question 19

How do keystone species promote biodiversity

Answer 19

1. prevent others from becoming dominant
2. prevent others eliminating/decimating lower trophic levels

Question 20

Explain grey wolves as keystone species

Answer 20

they were previously extirpated, but were reintroduced.
with the reintroduction it decline the elk population and changed their behaviour which results in the increase in biodiversity (increase beaver, fish, duck abundance)

Question 21

What are the 3 classifications of keystone species

Answer 21

1. ecosystem engineers
2. mutualists
3. hosts

Question 22

Define ecosystem engineers and an example

Answer 22

they change the environment and use the new environment to live where they wouldn’t be able to without those changes
ex. beaver construction of dams

Question 23

Define mutualists and an example

Answer 23

beneficial to both
ex. pollinators change the environment and without pollination, species wouldn’t be able to use the plants which affects the overall ecosystem

Question 24

How are hosts keystone species

Answer 24

they provide shelter to many species
ex. cacti

Question 25

Explain how disturbances can occur on many scales

Answer 25

big scale = forest fire
smaller scale = a tree fall that opens up a small canopy gap in a forest is also disturbance!

Question 26

Explain why disturbance might not always be bad for biodiversity

Answer 26

there is a tradeoff between competitive ability and colonization ability so at the right frequency or intensity it may promote biodiversity (low diversity/colonization ability at high competitive ability)

Question 27

What is the intermediate disturbance hypothesis

Answer 27

intermediate rates of disturbance allow for a mix of species that have life-history characteristics between the two extremes of:
lots of disturbances = few colonize and grow
not many disturbances = favour a few long living and competitively dominant species

Question 28

What are the 3 main arguments for why biodiversity is valuable

Answer 28

1. individually important species
2. biodiversity is also important (functions)
3. intrinsic value of biodiversity

Question 29

What are examples of why species are individually important

Answer 29

crops for food, textiles, drugs

Question 30

What are the 3 main reasons to support why biodiversity is important

Answer 30

1. ecosystem services
2. productivity
3. ecosystem stability

Question 31

Explain ecosystem services to support the importance of biodiversity

Answer 31

pollination services, climate regulation (peat bogs store lots of carbon), flood mitigation services

Question 32

Explain productivity to support the importance of biodiversity

Answer 32

more diverse ecosystems are more productive
and are also more stable

Question 33

Explain the advantages of intercropping

Answer 33

(growing more than 1 crop species in one location)

1. complementary use of resources (ex. spatial = different root depths, temporal = faster and slower growth)
2. may increase yield per unit area
3. may protect against disease
4. may augment native biodiversity

Question 34

Explain the argument of intrinsic value of biodiversity

Answer 34

believing it is intrinsically valuable regardless of its human utility