Download Answer Scheme GEO601

College of Humanities and Education
School Of Education
Lautoka
P.O. Box 5529, LautokaFIJI.Telephone:8658128
Website: www.fnu.ac.fj
GEO 601: Biogeography
Trimester 2, 2014
Time Allowed: 3 hours
Reading time: 10 minutes
Total Marks: 100
Note: Answer of some questions may not be identical but it should be in the same frame
work. The examples and analysis may vary from student to student. So it is not possible to
send all answer. Some time it depends on the evaluator perception to catch the theme of
analysis, critics or explanations.
SECTION A
1.
1.
2.
3.
4.
5.
6.
7.
CONCEPTS
Autecology
Autecology is the study of relationships of individual species to its environment.
Synecology
Ans. Synecology is the study of complex interrelationships of groups of organisms known as
biological community because organism affect each other in reciprocal manner and interact with the
habitat or natural environment.
Ecology by E.P. Odum
Ans. E.P. Odum: Ecology is ‘the study of the structure and function of ecosystems’ or the ‘study of
structure and function of nature’.
Saprotrophs
Heterotrophic organisms who secrete digestive enzymes onto dead organism matter and absorb the
digested material. (e.g. fungi, bacteria)
Niche
An organism’s habitat + role + tolerance limits to all limiting factors
The niche of a species consists of:
Its role in the ecosystem (herbivore, carnivore, producer etc)
Its tolerance limits (e.g. soil pH, humidity)
Its requirements for shelter, nesting sites etc, all varying through time
The compétitive exclusion principle
In ecology, the competitive exclusion principle, sometimes referred to as Gause's law of competitive
exclusion or just Gause's law, is a proposition that states that two species competing for the same
resources cannot coexist if other ecological factors are constant. When one species has even the
slightest advantage or edge over another then the one with the advantage will dominate in the long
term. One of the two competitors will always overcome the other, leading to either the extinction of
this competitor or an evolutionary or behavioral shift toward a different ecological niche. The principle
has been paraphrased into the maxim "complete competitors cannot coexist".
Biome (climatically and geographically).
Biomes are climatically and geographically defined as contiguous areas with similar climatic
conditions on the Earth, such as communities of plants, animals, and soil organisms, and are often
referred to as ecosystems.
Biomes are defined by factors such as plant structures (such as trees, shrubs, and grasses), leaf types
(such as broadleaf and needleleaf), plant spacing (forest, woodland, savanna), and climate.
Biomes are often identified with particular patterns of ecological succession and climax vegetation
(quasiequilibrium state of the local ecosystem).
8.
Biomagnification or biological magnification
There are several pesticides, heavy metals and other chemicals which are non-biodegradable in nature.
Such chemicals are not decomposed by microorganisms and they keep on passing from one trophic
level to another. At each successive trophic level, they keep on increasing in concentration. This
phenomenon is known as biomagnification or biological magnification
9.
* This is the idea for this question. Students may write any way.
Ans. Holocene is that portion of geologic time that postdates the latest episode of continental glaciation.
The Holocene Epoch is synonymous with the Recent or Postglacial interval of Earth's geologic history and
extends from 10,000 years ago to the present day. It was preceded by the Pleistocene Epoch and is part of
the Quaternary Period, a time characterized by dramatic climatic oscillations from warm (interglacial) to
cold (glacial) conditions that began about 1.6 million years ago. The term Holocene is also applied to the
sediments, processes, events, and environments of the epoch.
As the interval of time closest to us, the Holocene Epoch is very convenient to study. Holocene sediments
cover virtually every part of the Earth's surface and represent almost every environment of deposition. With
the development of 14C dating (a method of age determination based on the measurement of radioactive
carbon decay), Holocene sediments are relatively easy to date. From a scientific standpoint, the Holocene
Epoch is of great interest because it provides a recent analog for past environments and processes. Its
sediments and landforms provide important clues to changes that occurred as a result of the last shift from
the glacial to the nonglacial climatic mode. See also Depositional systems and environments; Radiocarbon
dating.
The Pleistocene/Holocene transition was a time of dramatic environmental change. The huge ice sheets that
had developed over the northern and western parts of North America (Laurentide and Cordilleran,
respectively) and most of Scandinavia were at their maximum geographic extent about 18,000 14C years
B.P. (before present, where present is defined as the year 1950) and in full retreat by 14,000 14C years B.P.
By 10,000 14C years B.P., the Laurentide ice sheet had withdrawn from the Great Lakes. The ice sheets
survived in the northern latitudes for another 3000 14C years or so. The progress of deglaciation was
complex, because the overall glacial meltback was interrupted by intervals of glacier readvance. It remains
unclear whether these readvances were synchronous on a hemispheric or global scale and what role ice
sheet/oceanic interactions played in the deglaciation.
The early phase of the Holocene was geologically the most eventful. The periglacial (near the edge of the
ice) landscape was unstable and very dynamic. As the Pleistocene ice sheets melted, enormous volumes of
water, stored as glacier ice for many thousands of years, returned to the oceans via meltwater streams or by
way of ice streams that flowed directly to the ocean.
As the ice sheets shrank, sea level rose an average of 130 m (426 ft), drowning the continental margins and
closing many land bridges, including the land bridge across the Bering Strait between Asia and North
America that had enabled humans to migrate to the Americas. In parts of Canada and Scandinavia,
temporary marine invasions occurred when the ice melted from low areas where the Earth's crust had been
depressed by the weight of the ice sheets.
http://www.answers.com/topic/holocene
10. A biodiversity hotspot is a biogeographic region with a significant reservoir of biodiversity that is under
threat from humans. The concept of biodiversity hotspots was originated by Norman Myers in two articles
in “The Environmentalist” (1988), & 1990 revised after thorough analysis by Myers and others in
“Hotspots: Earth’s biologically Richest and Most Endangered Terrestrial ecoregions”. To qualify as a
biodiversity hotspot on Myers 2000 edition of the hotspot-map, a region must meet two strict criteria: it
must contain at least 0.5% or 1,500 species of vascular plants as endemics, and it has to have lost at least
70% of its primary vegetation. Around the world, 25 areas qualify under this definition, with nine other
2.
possible candidates. These sites support nearly 60% of the world's plant, bird, mammal, reptile, and
amphibian species, with a very high share of endemic species.
Island biogeography examines the factors that affect the species richness of isolated natural communities. •
The field was started in the 1960s by the ecologists Robert MacArthur and E.O. Wilson, who coined the
term island biogeography. The basic theory says that on larger islands there is a larger number of species,
while smaller islands have less species diversity.
Theory of Island Biogeography
It proposes that the number of species found on an undisturbed island is determined by immigration and
extinction.
•Distance effect: Immigration and emigration are affected by the distance of an island from a source of
colonists. Islands that are more isolated are less likely to receive immigrants than islands that are less
isolated.
• Area effect or the species‐area curve: The rate of extinction once a species manages to colonize an island
is affected by island size. Larger islands contain larger habitat areas and opportunities for more different
varieties of habitat. Larger habitat size reduces the probability of extinction due to chance events.
Habitat heterogeneity increases the number of species that will be successful after immigration. Over time,
the countervailing forces of extinction and immigration‐‐‐ result –an equilibrium level of species richness.
• Other things that affect species diversity include time, isolation, and climate. The distance of an island or
other isolated habitat from other habitats is an important contributor to the levels of immigration and
emigration.
• Later expansions of the theory: animal body size and the effects of human activity on the species diversity
of a given area.
Modifications of Island Biogeography
• Rescue effect: Populations on islands that are less isolated are less likely to go extinct because individuals from
the source population and other islands can immigrate and “rescue” the population from extinction.
• Target effect: Species may actively target larger islands for their greater number of resources and available
niches; or, larger islands may accumulate more species by chance just because they are larger.
SECTION B
GEOGRAPHICAL SKILLS
This section is skill part. Some parts may vary from student to student
SECTION C
BRIEF ANSWERS
1. The sequence of eating and being eaten in an ecosystem is known as food chain.
A caterpillar eats a plant leaf, a sparrow eats the caterpillar, a cat or a hawk eats the sparrow and when they
all die, they are all consumed by microorganisms like bacteria or fungi (decomposers) which break down
the organic matter and convert it into simple inorganic substances that can again be used by the plants-the
primary producers
2.
Graphic representation of trophic structure and function of an ecosystem, starting with producers at the
base and successive trophic levels forming the apex is knows as an ecological pyramid. Ecological
pyramids are of three types:
a. Pyramid of numbers
b. Pyramid of biomass
c. Pyramid of energy
Pyramid of numbers
It represents the number of individual organisms at each trophic level. We may have upright or
inverted pyramid of numbers, depending upon the type of ecosystem and food chain
Pyramid of numbers in grassland
3.
Geological time scale embracing the history of the earth from its physical origin to the present day. Hence
Earth history is organized in hierarchical fashion into named subdivisions. The names of these divisions, at
the highest levels, form the standard vocabulary of geology.
Geological time is traditionally divided into eons (Archaean or Archaeozoic, Proterozoic, and Phanerozoic
in ascending chronological order), which in turn are subdivided into eras, periods, epochs, ages, and finally
chrons.
The terms eon, era, period, epoch, age and chron are geochronological units representing intervals of
geological time. Rocks representing an interval of geological time comprise a chronostratigraphic (or
timestratigraphic) unit.
4.
C‐S‐R Triangle
External factors which limit plant biomass may be classified as either stress or disturbance. Stress refers to
those conditions that restrict production, such as low light, insufficient water or nutrients, or suboptimal
temperature. Disturbance is the partial or total destruction of the plant biomass arising from herbivores,
pathogens, humans, wind damage, frost, desiccation, erosion, or fire.
Plants respond to these limiting factors with three types of strategies: stress‐tolerant, ruderal, and
competitive.
Using Grime's (1977) scheme, these relationships can be arranged in a triangle known as the C‐S‐R model.
Grime (1979) considers it highly unlikely that plants can tolerate extremes of both stress and disturbance.
Competitors: moderate to long life spans, relatively low reproductive efforts, high potential relative growth
rates, high dense canopies of leaves, abundant litter, and high morphological plasticity.
Stress tolerators: long life span, low reproductive effort, but low potential relative growth rates, little but
persistent litter.
Ruderals: more like competitors, but very short life spans, high reproductive rates.
5.
6.
7.
8.
9.
Ans. Pressure centre
plant ecology and animal ecology
True
True
True
10.
11.
12.
13.
c. This is because food webs give greater stability to the ecosystem
1-d, 2-b, 3-a, 4-c
Simple conical (One standard parallel)
The understory trees usually receive very dim sunlight. They usually develop dark green leaves with high
chlorophyll content so that they can use the diffused sunlight for photosynthesis.
The shrub layer receives even less sunlight and the ground layer commonly known as forest floor receives
almost no sunlight and is a dark layer. What is Wallace line and what is the importance of this line?
Wallace's Line delineates Australian and Southeast Asian fauna. The probable extent of land at the time of
the last glacial maximum, when the sea level was more than 110 m lower than today, is shown in grey. The
deep water of the Lombok Strait between Bali and Lombok formed a water barrier even when lower sea
levels linked the now-separated islands and landmasses on either side.
The distributions of many bird species observe the line, since many birds do not cross even the smallest
stretches of open ocean water. Some bats have distributions that cross the line, but other mammals are
generally limited to one side or the other; an exception is the crab-eating macaque. Other groups of plants
and animals show differing patterns, but the overall pattern is striking and
14. The Wallace Line or Wallace's Line is a faunal boundary line drawn in 1859 by the British naturalist Alfred
Russel Wallace that separates the ecozones of Asia and Wallacea, a transitional zone between Asia and
Australia. West of the line are found organisms related to Asiatic species; to the east, a mixture of species
of Asian and Australian origin is present. The line is named after Alfred Russel Wallace, who noticed this
clear division during his travels through the East Indies in the 19th century. The line runs through
Indonesia, between Borneo and Sulawesi (Celebes), and through the Lombok Strait between Bali and
Lombok. The distance between Bali and Lombok is small, about 35 kilometers (22 mi). The distributions of
many bird species observe the line, since many birds do not cross even the smallest stretches of open ocean
water. Some bats have distributions that cross the line, but other mammals are generally limited to one side
or the other; an exception is the crab-eating macaque. Other groups of plants and animals show differing
patterns, but the overall pattern is striking and reasonably consistent.
15. Two basic population strategies depend on how long a habitat is favourable. i.e, a population’s generation
time compared with the “life‐span” of a stable habitat. Short lived habitats tend to be occupied by
exploiters or opportunists and boom‐and bust
population dynamics. Such opportunists species are called r‐strategists, after the intrinsic growth rate, r, in
population growth equation.
Opportunist or r‐selected species
Each species has a characteristic mode of reproduction.
At one extreme are species that reproduces early and put most of their energy into reproduction.
They have many (usually small) offspring each time they reproduce; reach reproductive age rapidly; have
short generation time; give their offspring little or no parental care of protection to help them survive; and
are short‐lived (usually with a life span of less than a year).
Most offspring die before reaching reproductive age
Small adults
Adapted to unstable climate and environmental conditions
High population growth rate (r)
Population size fluctuates wildly above and below carrying capacity (K)
Generalist niche
Low ability to compete
Early successional species
Species with this reproductive pattern overcome the massive loss of their offspring by producing so many
unprotected young that a few will survive to reproduce many offspring to begin the cycle again.
Algae, bacteria, rodents, annual plants (such as dandelions) and most insects are examples of rselected
species.
Most r‐selected species or opportunist species go through irregular and unstable boom‐burst cycles in their
population size.
To survive, opportunists must continually invade new areas to compensate for being displaced by more
competitive species.
Competitor or K‐selected species
At the other extreme are Competitor or K‐selected species.
These species
• put fairly little energy into reproduction;
• tend to reproduce late in life;
• have few offspring with long generation times;
• put most of their energy into nurturing and protecting
their young until they reach reproductive age.
Typically these offspring
• develop inside their mothers (where they are safe),
• are fairly large
• mature slowly
• are cared for and protected by one or both parents until they reach reproductive age.
• High parental care and protection of offspring
• Most offspring survive to reproductive age
• Larger adults
• Adapted to stable climate and environmental conditions
• Lower population growth rate (r)
• Population size fairly stable and usually close to carrying capacity (K)
• Specialist niche
• High ability to compete
• This reproductive pattern results in a few big and strong individuals that can compete for resources and
reproduce a few young to begin the cycle again.
• Such species are called K‐selected species because they tend to do well in competitive
conditions when their population size is near the carrying capacity (K) of their environment.
Examples are most large mammals, birds and large and long‐lived plants (such as the saguaro cactus, oak
trees, redwood trees, and most tropical rain forest trees).
• Many K‐selected species, especially those with
long generation times and low reproductive rates (such as elephant, shark, and rhinocroses), are prone to
extinction.
16. Principles of Animal Distribution
• Jordan and Kellog proposed three laws that govern distribution and postulated that every species should
be found everywhere unless:
‐‐It was unable to reach the place where it is absent due to barriers.
‐‐It was unable to stay and adapt there because of unfavourable conditions.
‐‐It became modifies into another species due to directional selection.
SECTION D
LONG ANSWER
There are 3 questions. Choose any 2 questions to answer.
Marking Criteria: Relevance and Content – 5, Examples – 3, Clarity – 2, Total = 10 marks.
1. An ecosystem is dynamic and changes its structure as well as function with time. These
changes are very orderly and can be predicted
Ecological succession is defined as -
“An orderly process of changes in the community structure and function with time mediated
through modifications in the physical environment and ultimately culminating in a
stabilized ecosystem known as climax”.
The whole sequence of communities which are transitory are known as Seral stages or seres
whereas the community establishing first of all in the area is called a pioneer community.
Ecological successions starting on different types of areas or substrata are named differently
as follows:
(i) Hydrarch or Hydrosere: Starting in watery area like pond, swamp, bog
(ii) Mesarch: starting in an area of adequate moisture.
(iii) Xerarch or Xerosere: Starting in a dry area with little moisture. They can be of the
following types:
– Lithosere : starting on a bare rock
– Psammosere : starting on sand
– Halosere : starting on saline soil
The process of succession takes place in a systematic order of sequential steps as follows:
(i) Nudation: It is the development of a bare area without any life form. The bare area
may be caused due to◦ Topographic factor like landslides, Volcanic eruption etc.
◦ Climatic factor like drought, glaciers, frost etc.
◦ Biotic factors like overgrazing, disease outbreak
◦ Agricultural/ industrial activities
(ii) Invasion: It is the successful establishment of one or more species on a bare area
through dispersal or migration, followed by ecesis or establishment.
◦
Dispersal of the seeds, spores etc. is brought about by wind, water, insects or
birds.
Then the seeds germinate and grow on the land. As growth and reproduction start,
these pioneer species increase in number and form groups or aggregations
(iii) Competition and coaction: As the number of individuals grows there is
competition, both inter-specific (between different species) and intra-specific (within
the same species), for space, water and nutrition.
◦ They influence each other in a number of ways, known as coaction.
(iv) Reaction: The living organisms grow, use water and nutrients from the
substratum, and in turn, they have a strong influence on the environment which is
modified to a large extent and this is known as reaction.
◦ The modifications are very often such that they become unsuitable for the
existing species and favour some new species, which replace them.
◦ Thus, reaction leads to several seral communities.
◦ (v) Stabilization: The succession ultimately culminates in a more or less stable
community called climax which is in equilibrium with the environment.
The climax community is characterized by maximum biomass and symbiotic
(mutually beneficial) linkages between organisms and are maintained quite efficiently
per unit of available energy.
Ex- Consider very briefly a type of succession
Hydrosere (Hydrarch): This type of succession starts in a water body like pond.
A number of intermediate stages come and ultimately it culminates in a climax
community which is a forest. The pioneer community consists of phytoplanktons,
which are free floating algae, diatoms etc. Gradually these are replaced by rooted
submerged plants followed by rooted-floating plants. Growth of these plants keep on
adding organic matter to the substratum by death and decay and thus a layer of soil
builds up and shallowing of water takes place. Then Reed swamp (marshy) stage
follows in which the plants are partly in water and partly on land. This is followed by
a sedge meadow stage of grasses then by a woodland consisting of shrubs and trees
and finally by a forest acting as climax.
Ecological succession: A hydrach—from lake to woodland community.
(a) Open water body (lake), sediment
brought in by river.
(b) Sediment accumulation continues,
organic debris from plants too add to soil
formation and shrinking of water body
occurs.
(c) A mat of vegetation covers the water
which is mostly a marshy habitat now,
with a small part as aquatic system.
(d) Eventually the former lake is covered
by
climax
woodland
community,
representating a terrestrial ecosystem.
3. Describe and explain any two functional attributes of the ecosystems with suitable
example and diagram
10 Marks
The major functional attributes of an ecosystems are as follows:
(i) Food chain, food webs and trophic structure
(ii) Energy flow
(iii) Cycling of nutrients (Biogeochemical cycles)
(iv) Primary and Secondary production
(v) Ecosystem development and regulation
TROPHIC STRUCTURE
The flow of energy is mediated through a series of feeding relationships in a definite
sequence or pattern which is known as food chain.
Nutrients too move along the food chain.
The producers and consumers are arranged in the ecosystem in a definite manner and their
interaction along with population size are expressed together as trophic structure.
Each food level is known as trophic level and the amount of living matter at each trophic
level at a given time is known as standing crop or standing biomass.
FOOD CHAINS
 The sequence of eating and being eaten in an ecosystem is known as food chain.
 A caterpillar eats a plant leaf, a sparrow eats the caterpillar, a cat or a hawk eats the
sparrow and when they all die, they are all consumed by microorganisms like
bacteria or fungi (decomposers) which break down the organic matter and convert it
into simple inorganic substances that can again be used by the plants-the primary
producers
 Some common examples of simple food chains are:
 Grass
grasshopper
Frog Snake Hawk (Grassland ecosystem)
 Phytoplanktons
water fleas small fish Tuna
(Pond ecosystem)
 Lichens reindeer
Man (Arctic tundra)
 Each organism in the ecosystem is assigned a feeding level or trophic level
depending on its nutritional status.
 Thus, in the grassland food chain, grasshopper occupies the Ist trophic level, frog the
IInd and snake and hawk occupy the IIIrd and the IVth trophic levels, re-spectively.
 The decomposers consume the dead matter of all these trophic levels.
Food WEB
Food chains in ecosystems are rarely found to operate as isolated linear sequences.
They are found to be interconnected and usually form a complex network with several
linkages and are known as food webs.
Thus,
“Food web is a network of food chains where different types of organisms are connected at
different trophic levels, so that there are a number of options of eating and being eaten at
each trophic level”.
*Likewise students can discuss any of the above 5 points
4. Explanation may vary from student to students according to the area chosen.