1. food and drink

Bio 20c Fall 2014 Final
Name/SID Key
The figure on the right shows a simplified food
chain for a lake that lacks large piscivorous (fish
eating), fish (top) and for a lake that has large
piscivorous fish (bottom). Both lakes have
phytoplankton, herbivorous zooplankton, and
zooplankton eating fish (zooplanktivores). Both
lakes are large with maximum bottom depths of
well over 100 feet and with rooted vegetation
extending down only to 30 feet. What category
of freshwater biome do lakes such as this belong
to? (1)
Lentic system
In the space to the right, sketch a cross section of
the lake and label all of the distinct horizontal and
vertical zones that would be found in this lake. (2)
What two factors have the most influence on
regulating productivity in this system? (2)
1 sunlight
2 nutrients
What type of food web would this food chain be
part of? (1)
Grazing food web
What is the trophic status of each of the following in this food chain? (2)
Piscivore (fish eating fish) tertiary consumer or apex predator
Zooplankton primary consumer
Zooplanktivore (zooplankton eating fish) secondary consumer
Algae primary producer
Indicate which type of lake, Piscivores present or Piscivores absent, the following would occupy a
greater portion of their fundamental niche: (3)
Zooplankton piscivores present
Zooplanktivores piscivores absent
Phytoplankton piscivores absent
Water fleas of the genus Daphnia are one of the common species of herbivorous zooplankton in both
lakes. In order to avoid visual predators, they undergo daily movements from depth during the daytime
to the surface layer during nighttime and laboratory experiments have shown them to swim actively
away from the light. What type of behavior does this describe (be as specific as possible) (1)
phototaxis
Name one fitness benefit and one fitness cost that results from this behavior (1)
Benefit – decreased predation pressure
Cost – less time grazing/energetic cost of swimmin
The population of Daphnia in a lake with piscivores present is 20,346 in January and the following
February it is 42,634. What would be the simplest expression for both the discrete growth rate () and
the instantaneous growth rate (r) demonstrated by this population over this time period. (2)
N0 = 20,346, N1 = 42,634  = N1/N0 thus  = 42,643/20,346
 = er thus ln() = r thus r = ln(42,643/20,346)
Daphnia rarely live more than 6 months and during that time they produce multiple clutches of 20-40
eggs every 6-10 days if conditions are right. Most offspring do not survive to become mature adults.
What type of survivorship curve would best characterize Daphnia? (1)
Type III
What term would best characterize the life history characteristics of Daphnia? (1)
r selelected
Now consider the graph on the right showing data
for zooplanktivore abundance in lakes that have
either had piscivores removed and/or nutrients
added and unaltered (control) lakes. Which
treatment (if any) suggests that zooplankton
abundance is subject to top down control? (1)
Piscivores removed
Which treatment (if any) suggests that zooplankton
abundance is subject to bottom up control? (1)
Nutrients added
Which of the above factors (if any) has a greater
influence on regulating zooplankton abundance? (1)
Top down
Now consider the graphic on the right showing the
relative biomass of three trophic levels in lakes that lack
piscivores. Briefly explain how this pyramid could be
ecologically sustainable when zooplankton standing stock is
higher than phytoplankton standing stock (2)
The production rate of phytoplankton is higher than that of
zooplankton which allows the higher zooplankton biomass to
be sustained.
For each of the following organisms indicate which type of
lake (piscivore present or piscivore absent) would most likely demonstrate logistic growth for
populations of this type of organism (3)
Phytoplankton piscivores present
Zooplankton piscivores absent
Zooplanktivores piscivores present
Bonus question 1: Which circulation cell occur? Between 30 and 60 degrees latitude? Ferrell Cell
Name/SID
Tropical savannas such as those found in East Africa are characterized by expanses of grasslands and
grass like plants surrounding scattered individual trees made up primarily of several species of Accacias.
They tend to relative warm year round but have moderate annual precipitation with most of the rainfall
occurring in the summer months and relatively dry conditions in the winter time. While they resemble
temperate grasslands in some ways they also differ in several key aspects. What factor may account for
the presence of trees in this system as compared to the lack of trees in temperate grasslands? (1)
there is more annual rainfall than temperate grasslands thus they can
which can sustain trees
East African savannas are home to a variety of both grazing animals
such as the Impala gazelle, and predators of grazers such as leopards.
Recent studies have shown that impalas aggregate in open grassy
areas over more wooded areas in order to avoid predation by
leopards. Aggregating increases the ability of impala to detect a
predator as there are more eyes watching out while staying in the open also makes it harder for a
leopard to ambush their prey. Two main species of acacia tree occur
in
East African savannas, A. etbaica and A. brevispica. A. etbaica has
long thorns used to defend against grazers while A. brevispica has
much smaller thorns that are less effective as a defense. What term
best characterizes the type of defense these thorns represent? (1)
Constitutive defense
As previously mentioned, impala will largely avoid wooded areas
where their risk of leopard predation is much greater and in such areas A. brevispica is the dominant
species, while A. etbaica is more common interspersed in the more open grass dominated areas. Also in
areas where predators are absent, impala will spend more of their time within wooded regions grazing
on trees and in such areas A etbaica abundance is markedly increased. Use the information in the
preceding paragraph to answer the following questions:
For each of the following indicate what type of interspecific interaction is occurring making sure to also
indicate whether it is direct or indirect: (4)
Leopard/Impala antagonistic (predation) - direct
Impala/ grass antagonistic (herbivory) - direct
Leopard/A. etbaica either commensalism (direct) or ammensalism (indirect)
A. etbaica/A. brevispica competition (direct)
For each of the following indicate in which scenario – Leopards present (LP) or Leopards absent (LA) –
the following would occupy a greater portion of their fundamental nice (3)
A. etbaica LA
A. brevispica LP
Impala LA
Both leopards and impala tend to maintain stable populations over long timeframes and reproduce
multiple times in their lives giving birth to a few offspring each time. What type of population growth
does this suggest these animals demonstrate? (1) logistic
What type of survivorship curve would best characterize them? (1) type I
What term would best describe the life history strategy of both these species? (1) K selected
Many species of ants have a special relationship with certain acacia species in which trees will provide
shelter and sometimes food to ant colonies while ants will defend their home trees from grazers and
even assist in seed dispersal. One such ant-plant interaction exists between the whistling thorn tree
(Acacia drepanolobium) and the biting ant (Crematogaster spp). The tree provides the ants with
hollowed out thorns called domatia which are specifically adapted for habitation by ants. The tree also
provides nectar, which the ants collect from specialized non flowering structures at the bases of Acacia
leaves. In return for this investment, ants protect the tree from browsing mammals such as giraffes by
aggressively swarming against anything that disturbs the tree. What type of interspecific interaction is
occurring between: (2)
Ants and acacia mutualism
Ants and giraffes competition
After experiencing grazing, some acacias produce leaf tannin in quantities that can be lethal to the
browsers. They also can emit ethylene into the air which can travel up to 50 yards. The ethylene warns
other trees of the impending danger, which then step up their own production of leaf tannin within just
five to ten minutes. What type of defense best characterizes tannin production in such trees? (1)
inducible
What type of behavior is the plant engaged in when it releases ethylene into the air (be as specific as
possible) (2) communication via olfactory signal
Crematogaster ants produce a chemical in the presence of predators such as birds that causes ants to
actively retreat inro their protective domatia. What type of behavior does this represent (be as specific
as possible)? (2) communication via olfactory signal
How might you test whether the chemical releasing behavior of ants in response to a predator is innate?
(2) rear ants in isolation and then subject them to predators and see if they release chemicals.
Acacia flowers produce nectar in order to attract pollinators such as bees, but ants will vigorously
defend acacia trees from other insects. Acacia flowers can also produce a chemical that mimics the
warning chemical released by ants in the presence of predators. How does this behavior differ from the
release of the warning chemical by ants and what term would best describe this behavior? (2)
deceptive communication via olfactory signal
(give 1 point for Batesian mimicry)
Crematogaster ants display an unique form of eusociality due to their sex determination mechanism
known as haplodiploidy. This leads to worker and soldier ants which are full sisters sharing ¾ of their
genes while daughters of worker ants would only share ½ of their genes with their mothers. As a result,
workers do not reproduce but rather help the queen to produce and raise more full sisters. What type
of altruistic behavior are these ants displaying and how does Hamilton’s rule help explain why females
will help the queen raise more sisters rather than reproduce for themselves? (2)
They are engaged in kin selection and the degree of relatedness (r) is greater between sisters than it
would be between mother/daughters thus they increase their fitness more by helping make more sisters
BQ 2: What one component is found in true (bicoordinate) navigation that is not a component of
compass navigation knowledge of your geoposition
Name/SID:
Glacier Bay National Park is located in the Alaskan
panhandle west of the state capital Juneau. The
upper regions of the park are dominated by mosses,
lichens and shrubs with no trees. Lower down the
valley the plant communities are characterized by a
mixture of alder, cottonwood, and sitka spruce trees
while the regions of the valley floor, nearest to the
ocean, are characterized by dense stands of Sitka
spruce and Hemlock evergreen coniferous trees.
Which of the six terrestrial biomes presented in class
best represent: (2)
The upper region: tundra
The valley floor: taiga
Temperatures do not get as cold in the region of
the valley floor as they do in the upper regions
of the valley even though they are roughly at the
same latitude. What factor mentioned above
might account for this? (2) the high heat
capacity of the nearby ocean buffers the
temperature and keeps it from getting as cold
The glacier in Glacier Bay has been receding
steadily over the last two hundred years and
exposing the underlying soils. New plant
communities then developed in these exposed
soils over time. Consider the illustration to the
left that provides a synopsis of succession
following the glacier’s retreat the when answering the following questions: What type of succession
does this represent? (1)
Primary succession
What must the initital disburbance do in order to cause this type of succession (2)
It must remove all the organisms and the propagules etc in the soil
What term would best characterize the fireweed and moss life history strategy? (1)
r selected
What term would best characterize mature spruce life history strategy? (1)
K selected
Alder trees increase the nitrogen content of the soil and spruce trees grow significantly faster in the
presence of alder trees. What type of successional interaction is occurring between the alder and
spruce? (1) facilitation
Spruce shade alder trees when they grow higher than them and prevent new alder trees from sprouting.
What successional interaction are spruce and alder engaged in here? (1) inhibition
In the second example above, what type of competition are spruce and alder engaged in and is it
symmetric or asymmetric? (2)
Interference competition - it is asymmetric
In mature forests of 150 years or more, which tree, alder or spruce would occupy a greater portion of its
fundamental niche? (1)
spruce
In the space below, sketch the logistic growth curve making sure to label the axes as well as K and then
indicate which portion of the curve would most likely represent the population growth of 1) moss and
fireweed in newly exposed soils and 2) spruce trees in mature spruce forests. (5)
a = fire moss, b = spruce tree
The regions of the valley are subject to various types of disturbance such as avalanches, snow creep and
flooding. These tend to be highest in the upper valley, lowest in the lower valley and somewhere in
between in the middle of the valley. Based on this information, where would you expect to find the
highest diversity of plant species (upper, middle or lower valley)? (1)
Middle valley
What mechanism would likely cause your prediction above (2)
Intermediate disturbance would result in a mix of r and K selected species and overall higher diversity
What term(s) describe the relative mix of plant species found at the (3)
Upper valley mainly r selected
Mid valley mix of r and K selected
Lower valley mainly K selected
BQ3: What is Net Primary Productivity? The amount of primary producer biomass available to grazers
and decomposers
Name/SID
Kelp forests grow predominantly on the Pacific Coast, from Alaska and
Canada to the waters off Baja California. Tiered like a terrestrial
rainforest with a canopy and several layers below, the kelp forests along
Central and Southern California are dominated by the giant kelp:
Macrocystis pyrifera. Kelp forests grow along rocky coastlines in depths
of about 2 m to more than 30 m. Which marine biome would best
characterize where kelp forests are found? (1)
Neretic zone
Giant kelp is a perennial (i.e. it lives for several years) and has a twostage life cycle. They start as spores, released by the millions from the parent kelp known as a
sporophyte. A very small number of spores grow into a tiny male or female plant called a gametophyte,
which produces either sperm or eggs. After fertilization occurs, the embryos may grow into mature
plants (sporophytes), completing the life cycle. This happens throughout the year in most kelp forests.
What type of reproductive strategy does this represent? (1)
iteroparous continuous
Kelp forests provide critical habitat to a number of organisms. In
addition to kelp, a variety of other algal species can be found growing
underneath the kelp canopy. Herbivores such as urchins and abalones
consume this algae and a number of predators including sheephead
fish, octopus, and of course sea otters can be found in this system as
well. The figure on the right depicts a simplified food web for a typical
kelp forest. Is this an example of a grazing or decomposing food web?
(2) grazing food web
What is the trophic status of the following: (3)
Kelp primary producer Sheephead secondary consumer Sea otter secondary or tertiary consumer
Indicate which food chain in this web would transfer the least amount of energy to its top by recreating
it in the space below (1)
Kelp – abalone – octopus – sea otter
Which food chain, the one above or the one consisting of the grasses/acacia, impala, and leopard from
the second two pages of the exam would have a higher transfer tropic efficiency? (1)
Kelp – abalone – octopus – sea otter would have a higher trophic transfer efficiency
What might explain this (hint it is something to do with the nature of the consumers in each system) (2)?
The production efficiency of the consumers would be lower in the savanna as both consumers are warm
blooded and have higher metabolic costs
Sheephead fish are predators of sea urchins and in the course of eating them grind up their calcium
carbonate shells to form carbonate sediments. Using this information as well as the information above
and your general knowledge, identify one of each of the following types of reserves that carbon can be
found in this system: (3)
Biotic in the tissues of any of the organisms of this system
Chemical dissolved in seawater (either accept CO2 or bicarbonate/carbonate ions
Geologic calcium carbonate sediments
As stated above, sea otters are active predators on urchins. In the space below sketch all the
interactions that occur between otters, urchins and kelp. Indicate direct interactions with solid lines and
indirect interactions with dashed lines and be sure to indicate what the fitness consequences (+,-,0) are
to each organism involved in the interaction. (3)
When otters are present in kelp forests, urchins are mostly
restricted to protective cracks and crevices safe from the reach
of otters and they rely on drift (detached) algae which they
grab for food. In the absence of sea otters, urchins increase in
number, emerge from their protective retreats, and form
grazing fronts that can literally remove much of the algal
growth in the forest and turn it into an urchin barren. In which
situation – otters present or otters absent do urchins occupy a larger portion of their fundamental
niche? (1)
Otters absent
Using the information above and the food web in the previous page state for each of the following what
type of interaction is occurring between urchins and each of the following organisms, whether it is direct
or indirect, and what the fitness effect (+,-,0) is on 1) the organism in question and 2) the urchin (2)
Organism:
Interaction:
Direct/Indirect:
Effect on: organism
urchin
Sheephead
antagonistic(predation)
direct
__+__
_-___
Abalone
_competition
direct
__-__
__-__
Would it be correct to call kelp a keystone species and why or why not (2)?
No because although it has a big effect on the community it comprises a large portion of the
community’s biomass
Giant kelp can be detached from the bottom during storms or by large waves. When this occurs, a light
gap similar to those that occur in tropical wet forests forms and a distinct successional process ensues.
Among the first organism to recruit to the light gap are fast growing algal species. One such species is
Desmerestia which secretes hydrochloric acid to prevent other species of algae from recruiting the
space around it. Eventually larger algae such as understory kelps are able to overgrow Desmerestia and
other bottom algae and these in turn are overgrown and shaded out by giant kelp. The only algae that
can persist on the mature forest floor are low light tolerant species such as red coralline algae. What
type of succession does this represent? (1)
secondary
Using the previous information on kelp forest succession, indicate which type of the three possible
successional interactions is occurring between the following organism pairs: (2)
Desmarestia and understory kelps inhibition
Giant kelp and coralline algae tolerance
BQ4 With respect to disturbance, what does the term resistance mean? The amount that a disturbance
impacts a community