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BIOL 3130 Study Guide - Midterm Guide: Reproductive Isolation, Mate Choice, Molecular Evolution

Course Code
BIOL 3130
Andrew Mac Dougall
Study Guide

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Midterm Outline:
16-18 short answer questions (point form acceptable)
first sentence = answer, following sentences = details, if relevant, use a case study to illustrate your point
Question 1: What are the major challenges of conservation biology?
Conservation Biology = response by the scientific community to the environmental crisis: pollution, loss of
biodiversity, loss of ecosystem services
oMost extinctions occur unknowingly
oMost forms of conservation management occur unknowingly
oMost species have not been formally classified, and
oThe range and abundances of most classified species are poorly understood.
Human population growth and the corresponding increase in human consumption rate are contributing to
biodiversity degradation and loss - and will only continue to do so as the human population continues to
Anthropogenic climate change is rapidly altering ecosystems and will force what may currently be functional
natural resource management plans to adapt
Question 2: What do past extinctions say about present-day concerns of an impending extinction crisis?
extinction is a natural phenomenon, it occurs at a natural “background” rate of about one to five species per
year. Scientists estimate we’re now losing species at 1,000 to 10,000 times the background rate
extinctions tend to be followed by bursts in speciation, but speciation occurs at unpredictable rates (e.g.
explosive vs gradual)
Large fauna (mostly found in Africa) and endemic species are going to be particularly vulnerable
5 riders of the apocalypse: habitat loss, fragmentation/isolation, climate change, over-exploitation
[population size], species invasions
Question 3: Define and explain the primary mechanisms of speciation. How might they be affected by various
forms of global change, and what forms of conservation management could be used to counter these
Allopatric: population splits into two geographically isolated populations (e.g. continental drift, creation of
mountain ranges)
Peripatric: a subform of allopatric speciation where a new population is established by a very small number
of individuals from a larger population (founder effects, bottlenecks)
Parapatric: only partial geographical separation of the zones of two diverging populations -- individuals may
come in contact, but reduced offspring fitness leads to selection of mechanisms that prevent inter-breeding
Sympatric: two or more descendant species from a single ancestral species all occupying the same
geographic location
Question 4: What forms of speciation occur without complete isolation?
Parapatric and Sympatric speciation both occur without complete isolation
Question 5: Do different forms of speciation lead to different degrees of extinction vulnerability?
Endemic species or populations that are restricted to a relatively small area, such as an island, are
inherently more vulnerable to extinction
oessentially, allopatric speciation and peripatric speciation make species more vulnerable to
Question 6: Define and explain reverse speciation.
Speciation occurs as a by-product of divergent adaptation in heterogenous environments
Reverse speciation occurs when environments are homogenized increase gene flow, weaken ecological
selection, or both
Conditions under which reverse speciation can occur: a) when species are not geographically isolated or b)
have not been isolated by selection and/or mate choice long enough
oIntrogressive Hybridization A: the elimination of habitat isolation (two different habitats becoming
homogenized into a single habitat) drives reduced diversity
oIntrogressive Hybridization B: the elimination of geographical isolation (two different habitats
become connected) brings into contact otherwise allopatric species

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Outbreeding depression: when offspring from crosses between individuals from different populations have
lower fitness than progeny from crosses between individuals from the same population
Question 7: What is Transcendentalism and how does it represent a change in views on wilderness
compared to earlier centuries in colonial North America?
Transcendentalism = the belief that there is a parallel between the materialistic world and the upper world of
spiritual truths
ocontrasted Romanticism’s view of seeing only the wild’s aesthetic appeal, and the previous pioneer
views that nature was something to be conquered
oinstead, thought that things in nature reflected “universal spiritual truths”, and placed emphasis on
the good of man and of nature
Thoreau was a transcendentalist, he disliked society’s “commercial spirit” and emphasized wilderness had
mental and spiritual value, saw nature as a place to explore oneself
Question 8: What are the management assumptions of community or ecosystem-scale conservation
management, and what are the potential flaws with these assumptions?
Assumption: satellites and computers (GIS) can capture multiple species, and the processes that maintain
oFlaw: there are many different theorized processes and mechanisms that explain the loss of
species diversity, and satellite imagery can’t necessary show us what those are
Question 9: Why is area important for speciation? Give at least 3 explanation for how area can affect rates of
speciation. Mayr said isolation in small areas was the “crucible for speciation” and he wasn’t wrong -
reconcile this statement with the importance of area.
1. Larger ranges offer larger targets for geographical isolating barriers (allopatric speciation)
2. Widespread species have more genetic variability than narrowly distributed species
3. The larger the area covered by a species' range, the less chance that range will suffer permanent or
temporary obliteration, and the less vulnerable that species is to extinction
Mayr argues that reproductive isolation is the basis for defining a species, and this occurs by isolating
populations geographically. This relates to peripatric speciation were many small, geographically isolated
populations lead to speciation
Question 10: Explain the 7 hypotheses for tropical diversity, and why they cannot fully account for the high
diversity in the tropics.
1. History Hypothesis: the tropics are more species rich because they’ve had more time to establish
complete colonization and facilitate more evolution of new species
oSupporting evidence: the tropics have never experienced glaciation
oProblem: no region of the planet was free from the effects of glaciation (melting ice caps change
rainfall patterns & sea levels, OR frozen water in the north leads to desertification in the south)
2. Disturbance Hypothesis: the tropics are less disturbed than temperate regions
oSupporting evidence: disturbances kill biological life, thereby reducing rates of speciation
oProblem: disturbance can be a critical mechanism for maintaining or even increasing biological
diversity - aka the intermediate disturbance hypothesis
3. Habitat Heterogeneity Hypothesis: southern regions tend to have more environmental complexity per unit
area (e.g. mountains, rainforest, desert)
oSupporting evidence: allows for a wide variety of different niches
oProblem: works for mammals, but not so much for plants or birds. Also area is correlated with too
many other factors - some gradients are longitudinal
4. Available Energy Hypothesis: because the tropics receive more direct solar radiation than any location on
the planet, they have more energy available for ANPP (annual net primary production)
oSupporting evidence: greater sunlight = longer growing season = greater seasonal stability =
greater ANNP
oProblem: Principle of Competitive Exclusion, more resources means more to go around, but also a
greater likelihood of intense competitive interactions that may decrease biological diversity
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