BIO 171 (2025) comprehensive questions and verified answers ( detailed & elaborated) ACTUAL EXAM
2025 TEST!!
Describe the dominant latitudinal pattern associated with species diversity and explain
potential causes - correct answer Biotic (mutualists, competitors, herbivores, predators) and
abiotic (temp, precip, soil type) factors affect community composition
But also size of area, latitude, disturbance history
Latitudinal Pattern:
as you move away from equators species richness declines, species is richest in tropics , true for
most group of animals
5 main hypothesis for latitudinal pattern:
1. High primary productivity: tropical areas are warm and have lots of precipitation, so ideal
conditions for plants and photosynthesis, have highest rates of PP, so it supports high numbers
of consumer and decomposer species
2. Tropics as cradle: tropical areas have high speciation rates and have had more time for
speciation to occur (glaciers caused lots of extinction)
3.Tropics as museum: lower extinction rates in tropics because climate is more stable
4. Stronger biotic interactions: predator/prey and same drives coevolution which drives
speciation
5. Terrestrial tropical areas have larger area which means more niches which mean more
species
not mutually exclusive
all else being equal (areas of the same latitude), the larger the geographic area of a community,
the greater the number of species.
,BIO 171 (2025) comprehensive questions and verified answers ( detailed & elaborated) ACTUAL EXAM
2025 TEST!!
Increases species richness because larger area has more different kinds of habitats which allows
for more niches and more species
and/or because large areas have higher colonization rates and lower extinction rates (more
resources)
Define species richness and evenness, and explain how each contributes to biodiversity -
correct answer species diversity:
1. species richness (# of species)
2. species evenness (relative of abundance of each species)
- A community is more bio-diverse if it has more species and those species are abundant
richness contribution to biodiversity - increase number of species and plant biomass (primary
productivity) increases but then levels off.
evenness contribution to biodiversity -
Describe and explain the setup, results and conclusions of Tilman's experiments on the
importance of biodiversity - correct answer Tilman wanted to test if species richness and
functional diversity of species affected primary production.
Setup up research plots in grassland ecosystems - cedar creek
Measured aboveground biomass
Found that if you increase species richness and functional diversity then you increase plant
biomass (and thus primary productivity which effects all other trophic levels) but then it levels
off
Describe an ecological disturbance and give examples of a few disturbances - correct answer
Disturbances: factors that open up physical space in a habitat
most are abiotic factors (natural disasters) and are density-independent
Categorized by two factors: intensity and frequency of the event (most severe have high
intensity and high freq and vice versa)
Glen arbor disturbance, severe storm, disturbance exceeded normal regime and followed by
disturbance
, BIO 171 (2025) comprehensive questions and verified answers ( detailed & elaborated) ACTUAL EXAM
2025 TEST!!
Forest Fires: shows on tree rings, trees can survive fires, in Yellowstone there are fire adapted
fire which have cones that open from fire and germinate. Elk eat burned bark so they come
back then flowers regenerate that are fire adaptive, which support pollinators which support
other organisms and the fire allowed cones to open and seeds exit and the fire allows the seeds
to germinate
Describe the similarities and differences between primary and secondary succession - correct
answer Succession: the pattern of species composition changing following a disturbance
Primary succession: occurs after a disturbance event destroys the soil/soil community (bacteria,
archae, fungi) soil formation needed for community needs breakdown of rock and microbe
colonization causes accumulation of organic matter then colonization of plant and other
organisms, which causes glacier moves soil or volcanic eruption bc lava covers soil, lava
hardens, and destroys soil community
Secondary succession: occurs after a disturbance removes much or all of the vegetation in an
area, but leaves soil community intact
-fire, hurricanes, flood
Explain how disturbances and succession impact the nature of biological communities - correct
answer Secondary succession
pioneering species should have high dispersal ability, tolerant of disturbed habitat and can
handle harsh conditions
some of the early colonizers improved conditions for later-arriving species -> facilitation
can also make conditions worse for later arriving species -> inhibition
both lead to succession because they improve nutrient level of soil so more organisms can
come in later
Define microbiome and explain how humans and other organisms harbor unique ecosystems -
correct answer Microbiome: all the microorganisms living in association with an organism
skin gut mouth urinary genital tract microbiome
Functions of human microbiome:
-provides a barrier to invasion by pathogens (organisms that cause disease)
2025 TEST!!
Describe the dominant latitudinal pattern associated with species diversity and explain
potential causes - correct answer Biotic (mutualists, competitors, herbivores, predators) and
abiotic (temp, precip, soil type) factors affect community composition
But also size of area, latitude, disturbance history
Latitudinal Pattern:
as you move away from equators species richness declines, species is richest in tropics , true for
most group of animals
5 main hypothesis for latitudinal pattern:
1. High primary productivity: tropical areas are warm and have lots of precipitation, so ideal
conditions for plants and photosynthesis, have highest rates of PP, so it supports high numbers
of consumer and decomposer species
2. Tropics as cradle: tropical areas have high speciation rates and have had more time for
speciation to occur (glaciers caused lots of extinction)
3.Tropics as museum: lower extinction rates in tropics because climate is more stable
4. Stronger biotic interactions: predator/prey and same drives coevolution which drives
speciation
5. Terrestrial tropical areas have larger area which means more niches which mean more
species
not mutually exclusive
all else being equal (areas of the same latitude), the larger the geographic area of a community,
the greater the number of species.
,BIO 171 (2025) comprehensive questions and verified answers ( detailed & elaborated) ACTUAL EXAM
2025 TEST!!
Increases species richness because larger area has more different kinds of habitats which allows
for more niches and more species
and/or because large areas have higher colonization rates and lower extinction rates (more
resources)
Define species richness and evenness, and explain how each contributes to biodiversity -
correct answer species diversity:
1. species richness (# of species)
2. species evenness (relative of abundance of each species)
- A community is more bio-diverse if it has more species and those species are abundant
richness contribution to biodiversity - increase number of species and plant biomass (primary
productivity) increases but then levels off.
evenness contribution to biodiversity -
Describe and explain the setup, results and conclusions of Tilman's experiments on the
importance of biodiversity - correct answer Tilman wanted to test if species richness and
functional diversity of species affected primary production.
Setup up research plots in grassland ecosystems - cedar creek
Measured aboveground biomass
Found that if you increase species richness and functional diversity then you increase plant
biomass (and thus primary productivity which effects all other trophic levels) but then it levels
off
Describe an ecological disturbance and give examples of a few disturbances - correct answer
Disturbances: factors that open up physical space in a habitat
most are abiotic factors (natural disasters) and are density-independent
Categorized by two factors: intensity and frequency of the event (most severe have high
intensity and high freq and vice versa)
Glen arbor disturbance, severe storm, disturbance exceeded normal regime and followed by
disturbance
, BIO 171 (2025) comprehensive questions and verified answers ( detailed & elaborated) ACTUAL EXAM
2025 TEST!!
Forest Fires: shows on tree rings, trees can survive fires, in Yellowstone there are fire adapted
fire which have cones that open from fire and germinate. Elk eat burned bark so they come
back then flowers regenerate that are fire adaptive, which support pollinators which support
other organisms and the fire allowed cones to open and seeds exit and the fire allows the seeds
to germinate
Describe the similarities and differences between primary and secondary succession - correct
answer Succession: the pattern of species composition changing following a disturbance
Primary succession: occurs after a disturbance event destroys the soil/soil community (bacteria,
archae, fungi) soil formation needed for community needs breakdown of rock and microbe
colonization causes accumulation of organic matter then colonization of plant and other
organisms, which causes glacier moves soil or volcanic eruption bc lava covers soil, lava
hardens, and destroys soil community
Secondary succession: occurs after a disturbance removes much or all of the vegetation in an
area, but leaves soil community intact
-fire, hurricanes, flood
Explain how disturbances and succession impact the nature of biological communities - correct
answer Secondary succession
pioneering species should have high dispersal ability, tolerant of disturbed habitat and can
handle harsh conditions
some of the early colonizers improved conditions for later-arriving species -> facilitation
can also make conditions worse for later arriving species -> inhibition
both lead to succession because they improve nutrient level of soil so more organisms can
come in later
Define microbiome and explain how humans and other organisms harbor unique ecosystems -
correct answer Microbiome: all the microorganisms living in association with an organism
skin gut mouth urinary genital tract microbiome
Functions of human microbiome:
-provides a barrier to invasion by pathogens (organisms that cause disease)
