Coexistence, Biodiversity + Ecosystem Services Flashcards
What is the paradox of the plankton
how is it possible for many species to coexist in an unstructured population while all competing for the same resources
What is interference competition vs. exploitation/scramble competition
interference = direct competition (ex. fighting)
exploitation = indirect competition by depleting shared limited resources
What does it mean that competition is often considered antithetical to coexistence
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
What is Gause’s Competitive Exclusion Principle
where 2 species compete for the same limiting factor, they cannot coexist and only one species will persist
Define ecological niche
the species abiotic and biotic environment that it can tolerate
As niches become more similar between competing species, how does it affect competitive exclusion and coexistence
competitive exclusion increase
coexistence decreases
What 3 reasons allow for species coexistence in light of the competitive exclusion principle
- resource partitioning
- importance of influential species
- disturbance
What is resource partitioning
if species niches are sufficiently different and not overlapping, the species may be able to coexist despite competition
Explain the example of warblers as resource partitioning
individuals of different species forage for food on the same tree, BUT specialize on different branch heights
Explain the example of cutthroat trout and dolly varden charr as resource partitioning
when found together, dolly varden charr do not utilize the bottom-dwelling food compared to when the trout are absent, they do.
Evolution can lead to greater partitioning via ____. How?
character displacement
an evolutionary divergence of niche traits. the individuals are selected for on the opposite “sides” of the niches
Explain character displacement in darwin’s finches
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
What are the two categories of “species” that have a greater influence on their community than others
- dominant species
- keystone species
Define dominant species
species that have greater abundance/biomass compared to other species and exert influence because of the fact that they are so large
Example of a dominant species
giant kelp
What allows a species to dominate
- 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
- resistant of natural enemies ex. can grasses dominate if unpalatable to grazers and if chosen to not be eaten
Define keystone species
species that exert a strong influence on their community even though they don’t dominate and often promote biodiversity
Explain ochre stars as a keystone species
in an experiment, the removal of sea stars caused the mussels to dominate and take up to 60-80% of the space
How do keystone species promote biodiversity
- prevent others from becoming dominant
- prevent others eliminating/decimating lower trophic levels
Explain grey wolves as keystone species
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)
What are the 3 classifications of keystone species
- ecosystem engineers
- mutualists
- hosts
Define ecosystem engineers and an example
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
Define mutualists and an example
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
How are hosts keystone species
they provide shelter to many species
ex. cacti
Explain how disturbances can occur on many scales
big scale = forest fire
smaller scale = a tree fall that opens up a small canopy gap in a forest is also disturbance!
Explain why disturbance might not always be bad for biodiversity
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)
What is the intermediate disturbance hypothesis
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
What are the 3 main arguments for why biodiversity is valuable
- individually important species
- biodiversity is also important (functions)
- intrinsic value of biodiversity
What are examples of why species are individually important
crops for food, textiles, drugs
What are the 3 main reasons to support why biodiversity is important
- ecosystem services
- productivity
- ecosystem stability
Explain ecosystem services to support the importance of biodiversity
pollination services, climate regulation (peat bogs store lots of carbon), flood mitigation services
Explain productivity to support the importance of biodiversity
more diverse ecosystems are more productive
and are also more stable
Explain the advantages of intercropping
(growing more than 1 crop species in one location)
- complementary use of resources (ex. spatial = different root depths, temporal = faster and slower growth)
- may increase yield per unit area
- may protect against disease
- may augment native biodiversity
Explain the argument of intrinsic value of biodiversity
believing it is intrinsically valuable regardless of its human utility
