Midterm 2 Study Guide Flashcards

Question

What is meant by the term “ecological release”? Provide an example to support your answer.

Answer 1

Ecological release= relaxation of selective pressures. Resources might be abundant and competition reduced when a species disperses to an uninhabited island, so they can experience ecological release (even reverse selection) result= population in a species-poor enviro with little competition will occupy a broader range of their fundamental niche Example: Voles and shrews Shrew density is much higher in a habitat where voles are not present: they experience ecological release when voles aren’t present - Niche shift in presence or absence of another species

Answer 2

1. Endemism: species are unique to that location (not found anywhere else) - The more isolated the island, the higher number of endemic species 2. Reduced dispersal: for example, flightless species: a bird might disperse to an island, then experience no competition, so lose the ability to fly because there is no need to. This prevents further dispersal - Also, plants on an island can usually only disperse WITHIN that island 3. Gigantism and Dwarfism: Island Rule: trend towards medium size (dwarfism in large species and gigantism in small species) Bergmann’s Rule: body mass increases with latitude Cope’s Rule: trend towards larger body size (and range of sizes) during the evolutionary diversification of a lineage

Answer 3

The more isolated the island, the higher number of endemic species

Answer 4

On very isolated islands nearest to the equator - Because increase in isolation= increase in endemic species - And islands are biodiversity hotspots, & the highest biodiversity is near the equator

Answer 5

Lots of birds - The ancestral population can fly, which is how they originally disperse - They experience several generations with no predators on the new island, so have no need to fly → lose ability to fly Eventually, dispersal is reduced because they can no longer fly Also plants: Can only disperse within the island they’re on, unless a vector brings their seeds somewhere else (likely how they dispersed in the first place)

Answer 6

Island Rule= trend towards medium-sized organisms (dwarfism in large species and gigantism in smaller species) Little things get bigger (because of ecological release) Big things get smaller (because of ecological release from competitors and resource limitation) Bergmann’s Rule= body mass increases with latitude Cope’s Rule= trend towards larger body size (& range of sizes) during the evolutionary diversification of a lineage

Answer 7

Because the theory behind actual islands also applies to any isolated area (that acts as an island). For example, chains of lakes and forest fragments are isolated similarly to an actual island, and the phenomena observed are the same Example: If there is a chain of lakes that aren’t connected, the aquatic organisms cannot move from one lake to another. This has the exact same implications as a typical island

Answer 8

A fragmented piece of land (a forest, for example) acts as an island, especially to smaller organisms, because it may be impossible for that organism to get from one forest patch to another.

Answer 9

1. Bigger islands have more species 2. The greater the distance to the island (from mainland) = fewer species

Answer 10

There are usually more species on a bigger island simply because there is more land, so more potential niches to fill

Answer 11

More isolated islands are a further distance from the mainland, creating physical barriers to dispersal. For example, having to swim or fly 1000 km to an isolated island may be impossible for many species, but possible for only a couple. If it was only 500 km, more species would be able to make the trek, so the nearer island would be able to have more species

Answer 12

*be able to draw graph on the exam* - Proposed in 1967 by MacArthur and Wilson - Proposed the # of species inhabiting an island represents a dynamic equilibrium b/w opposing rates of immigration and extinction - Dynamic b/c immigration and extinction are recurrent, opposing processes, maintaining a relatively stable species # despite ongoing changes in species composition - Simply: --> Distance of an island from a source pool will affect immigration rate --> Area of an island will affect extinction rate --> A near island should return to equilibrium more rapidly than a distant island of = size b/c it should have a higher immigration rate but the same extinction rate

Answer 13

They simply stated 3 phenomena exhibited by islands: - Species-area relationship: species richness increases with increasing area - Species-isolation relationship: species richness decreases with increasing isolation - Species turnover: the rate of replacement as colonizing species replace those that have gone extinct

Answer 14

Does not account for: - Interspecific differences and interactions (species differences- this model is species-neutral) - Succession or disturbance (time) - Shape and other habitat complexity (such as edge effects) - Equilibrium state is rarely attained in nature (succession and disturbance)

Answer 15

be able to draw graph on exam Proposed there are 3 equilibriums for species number on an island During each phase, something different is happening More complex than the original theory of island biogeography

Answer 16

Understand the graph, but don’t need to draw it This model accounts for geophysical effects that might drive immigration and extinction (like land bridges, volcanoes, etc)

Answer 17

The original equilibrium theory was the first to explain how islands were colonized, but it did not account for many complexities that the other 2 models did (eg. edge effects, interspecies differences, etc) Wilson and Simberloff’s model proposed 3 equilibriums, which was a unique idea - More complex: accounted for interactions b/w species Robert Whittaker’s model accounts for geophysical effects that drive immigration/ extinction, suggests a maximum topographic complexity (carrying capacity)

Answer 18

Challenging to survey and sample marine environments Difficult to determine barriers b/w areas or distribution Oceans are massive Marine species are often morphologically similar → differences have to be determined by genetics, which is expensive (hard to determine if they’re related by just looking at them)

Answer 19

Most organisms live in the pelagic zone (open ocean) Advantages to living in pelagic zone: - Access to light still (important for photosynthetic organisms) - High primary productivity (= food for consumers) - Warmer temps= don’t need to be adapted to live in cold-water environments Disadvantages to living in pelagic zone: You don’t get the stability that comes with living in the benthic zone! - Little shelter from storms - Benthic has more supply of organic matter (falls through column) - Pelagic has less habitat than benthic zone