IB Biology Review Chapter 53: Community Ecology 8

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IB Biology Review

• Chapter 53 Community Ecology

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Definitions

• Community
• consists of all the organisms of all the species
  that inhabit a particular area
• it is an assemblage of populations of many
  different species
• Community Ecology
• deals with the whole array of interacting species
  in a community
• This area of research focuses on how
  interactions such as predation, competition, and
  disease, as well as abiotic factors such as
  disturbance, affect community structure and
  organization

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Habitat Realized Niche Detritivore
Autotroph Biodiversity Symbiosis
Ecological Niche Saprotroph
Interspecific Competition Heterotroph
Competitive Exclusion Biomass
Fundamental Niche

• 1.________________ is a particular environment,
  the typical location of a particular species. It
  is the organisms address
• 2.________________ is the totality of an
  organisms relationships with all the biotic and
  abiotic factors which make up the organisms
  habitat
• 3._______________ is when two species compete or
  interact for a resource
• 4.______________ is the strong competition that
  can lead to the local elimination of one of the
  two competing species the result is detrimental
  to both species (-/-) such as when two different
  species compete for a resource that is in short
  supply
• 5.______________ is a special type of
  interaction, where one organism lives on or in
  another and does not harm the host
• 6.______________ is the total mass of all
  individuals in a population
• 7. ______________ is the number of different
  species in a given geographical area
• 8.________________ is the niche potentially
  occupied by that species
• 9.________________ is the niche a species
  actually occupies in a particular environment
• 10._____________ is an organism that synthesizes
  its organic molecules from simple inorganic
  molecules
• 11._____________ is an organism that obtains
  organic molecules from other organisms
• 12._____________ is an organism that ingests
  non-living organic matter
• 13._____________ is an organism that lives on or
  in non-living organic matter, secreting digestive
  enzymes into it and absorbing the products of
  digestion

Habitat
Ecological niche
Interspecific comp.
Comp. Exclusion
Symbiosis
Biomass
Biodiversity
Fundamental niche
Realized niche
Autotroph
Heterotroph
Detritivore
Saprotroph
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MC-1.
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Define the term niche.

• Within a specific habitat of an organism it is
  the species role/profession
• An organisms unique ability to survive in its
  habitat
• For example,
• nutrition/what it eats
• feeding habits (like the Nuthatch hammering
  the seeds)
• interactions with other species
  (aggression/competition)
• the time of day or night that it feeds
• breeding site

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Describe fundamental niches and realized niches.

• Fundamental Niche
• All the habitat the organism could live in if
  there were no competing species
• Realized Niche
• The habitat that the organism actually inhabits
  due to competition for similar space from other
  species

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MC-2. Prairie dogs once covered the expanses of
the Great Plains. Their grazing made the grass
more nutritious for the huge herds of bison, and
a variety of snakes, raptors, and mammals preyed
on the rodents. In fact, the black-footed ferret
(now endangered) specialized in prairie dog
predation. Today, growing neighborhoods have
covered many prairie dog towns. Which of
thefollowing statements about prairie dogs is
not true?

• A. Their realized niche has diminished.
• B. They are commensals with the bison.
• C. They are reasonably considered a keystone
  species.
• D. Their fundamental niche remains unaltered.
• E. Their fundamental niche has diminished.
• Correct answer E

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Competitive Exclusion Principle

• No two species can coexist in the same niche
• One is out-competed and displaced/eliminated
  through strong competition
• Reduces competing species space from the
  fundamental niche to the realized niche
• Use in an answer barnacle competition from Figure
  53.2 in text

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CC 53.1 According to the competitive exclusion
principle, what outcome is expected when two
species compete for a resource? Why?

• One of the competing species will become locally
  extinct because of the greater reproductive
  success of the more efficient competitor.

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Definitions

• Intra-specific competition
• interactions between individuals of a population
  of just one species
• Inter-specific competition
• interactions between populations of two species

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Types of Inter-specific Interactions

• 0 No effect
• Positive effect
• - Negative effect

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MC-3. Evidence shows that some grasses benefit
from being grazed. Which of the following terms
would best describe this plant-herbivore
interaction?

• A. mutualism
• B. commensalism
• C. parasitism
• D. competition
• E. predation
• Correct answer A

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MC-4. Which of the following is least likely to
kill the organism it feeds on?

• A. herbivore
• B. predator
• C. seed eater
• D. carnivore
• E. parasite
• Correct answer E

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Definitions

• Trophic structure
• The feeding relationships between species of a
  community
• Trophic levels
• The different groups of organisms in a community
• Arranged as
• Producers
• 1st Order Consumers
• 2nd Order Consumers
• 3rd Order Consumers
• 4th Order Consumers

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What are the trophic levels?
3rd Order Consumers
2nd Order Consumers
1st Order Consumers
Producers
Plants
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Why does the energy pyramid look like it does?

• Energy transfer between trophic levels is never
  100 efficient. Only 10-20 of energy is
  transferred
• How is the other 90 of energy lost?
• Heat loss through cellular respiration
• Not all organisms in lower trophic levels are
  consumed
• The whole mass of the prey is not assimilated
  into the predators body
• Energy lost through the metabolic processes of
  the prey before they are consumed

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MC-5. Consider a field plot containing 300 kg of
plant material. Approximately how many kg of
second-order consumer can be supported?

• A. 300
• B. 100
• C. 30
• D. 3
• E. 0.3
• Correct answer D
• 300 x 0.10 30 x 0.10 3

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Definitions

• Food chain
• a single pathway of feeding relationships among
  organisms in an ecosystem that results in energy
  transfer
• Food web
• complex feeding relationships among all the
  organisms in an ecosystem that results in energy
  transfer

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Be able to construct/draw an Antarctic food web
with the following species or groupsFishes,
Copepods, phytoplankton, leopard seals, elephant
seals, baleen whales, sperm whales, birds, krill,
carnivorous plankton, crab eater seals, smaller
toothed whales, humans, squids.Make sure arrows
are going in the right direction.Be able to
identify one or more food chains within this food
web of at least 4 species long.
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What is the benefit of a more complex food web?

• biodiversity
• More stability because predators have a variety
  of choices for prey
• So if one prey species dies out, the predator can
  feed on other species

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MC-6. In a food web with deer, clover, rabbits,
and wolves, wolves would be the

• A. producers
• B. primary consumers
• C. secondary consumers
• D. tertiary consumers
• Correct answer C

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MC-7. Which of the following conditions would
result from a more complex food web?

• A. lower rates of mortality
• B. stability
• C. high reproductive rates
• D. lower natality rates
• Correct answer B

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Ecological Succession

• Primary succession
• the creation of soil in a virtually lifeless area
  where there was no soil before
• Examples after a volcanic eruption, or after a
  retreating glacier
• Secondary succession
• occurs when an existing community has been
  cleared by some disturbance that leaves the soil
  intact
• Examples after a fire, flood, hurricane, or
  tornado

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How does primary succession occur?

• 1. Often the only lifeforms initially present
  are autotrophic prokaryotes existing in shallow
  puddles.
• 2. Lichens and mosses come next, which grow from
  windblown spores
• Soil develops gradually, as rocks weather and
  organic matter accumulates. Lichens secrete
  acidic products that help to break down the rock.
• From the decomposed remains of these early
  colonizers soil is formed.
• 3. Once soil is present, the lichens and mosses
  are usually overgrown by grasses,
• 4. Then shrubs,
• 5. Then trees that sprout from seeds blown in
  from nearby areas or carried in by animals.

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4
3
2
1
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CC 53.3 How do primary and secondary succession
differ?

• The initial absence of soil in primary succession
  and its presence at the beginning of secondary
  succession.

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1. Explain the niche concept using a named
organism. (5 marks)
IB Exam Question

• Within a specific habitat it is the species
  role/profession
• It allows different species to co-exist with each
  other by reducing competition
• For example, the white-breasted nuthatch shares
  temperate forest habitat with many species
• Nuthatches go down a tree in search of insects
  hiding under bark unlike most species which go up
  the tree looking for insects. In this way, it is
  able to get insects that others miss.
• Another aspect of its unique niche is that takes
  seeds, wedges them into a crevice of tree bark
  and then hammers the bark this opens the
  seeds for eating.
• Yet another aspect of this birds niche is that it
  flocks together with black-capped chickadees and
  titmice. In this way, it is protected
  frompredators by being able to hear the warning
  calls of these species when predators approach

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2. Explain the significance of the principle of
competitive exclusion.
(3 marks)
IB Exam Question

• no two species can coexist in same niche
• one is displaced / one survives
• one species has an advantage over competitor /
• species compete with each other

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3. Explain how parasitism differs from mutualism
with reference to named organisms. (5
marks)
IB Exam Question

• Parasitism is a type of interspecific interaction
  where one organism benefits and one suffers
• whereas Mutualism is when both benefit (neither
  suffer)
• An example of parasitism is a tapeworm in its
  human host
• The parasite gains food and energy whereas the
  human host loses food
• Because of this, the host suffers weight loss and
  impaired nutrition
• In a mutualistic interaction such as green algae
  and fungi in lichens
• The algae gains protection
• Whereas the fungi gains carbon compounds through
  the algaes photosynthesis

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4. Explain reasons for the shape of the energy
pyramid. (5 marks)
IB Exam Question

• Energy transfer efficiency between each trophic
  levels is (approximately) 10 from one level to
  the next (in other words, 90 is lost at each
  level)
• heat loss through cellular respiration
• not all organisms in lower trophic levels are
  consumed
• the whole mass of the prey is not assimilated
  into the predators body (waste is produced)
• energy lost through the metabolic processes of
  the prey before they are consumed

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5. Explain why there are limits on food chain
length by describing how energy enters, moves
through, and exits a food chain in an ecosystem.
(8 marks)
IB Exam Question

• energy enters from (sun)light
• autotrophs capture (sun)light
• energy flows through the trophic levels / stages
  in food chain (eg.
• ProducergtgtPrimary ConsumergtgtSecondary
  consumergtgt Tertiary ConsumergtgtQuarternary
  Consumer)
• energy transfer efficiency between each trophic
  levels is (approximately) 10 from one level to
  the next (in other words, 90 is lost at each
  level)
• energy loss through cellular respiration
• Energy is lost through heat
• Energy is lost because not all material is
  consumed
• Energy is lost because food that is not all
  assimulated and is lost as waste
• Include a labeled energy pyramid (using kJ per
  square meter per year as x axis (kJ/m2/yr))

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6. Outline the changes in species diversity and
production during primary succession (5
marks)
IB Exam Question

• Species diversity is very low in the early stages
  of primary succession
• This is because few species can tolerate the
  barren conditions
• However, as primary succession continues,
  species diversity increases
• Gross Production is also very low in the early
  stages of primary succession but increases during
  primary succession
• This is because small plants are replaced by
  larger plants with more leaf surface area to
  photosynthesize
• Gross production eventually stabilizes

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7. In communities, groups of populations live
together and interact with each other. Outline
the importance of plants to populations of other
organisms in a community. (6 marks)
IB Exam Question

• light is the initial source of energy for almost
  all communities
• plants absorb light and use it in photosynthesis
• plants produce food / organic matter
• plants are the main producers in most
  communities
• energy flows along food chains / webs from
  plants
• first consumers eat plants / producers
• second consumers eat first consumers that have
  eaten plants / producers
• plants produce oxygen
• oxygen needed for cell respiration by many
  organisms
• dead plants / parts of plants available to
  saprotrophs / fungi and bacteria / detritivores

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8. Distinguish between primary and secondary
succession using an example of each. (6 marks)
IB Exam Question

• Primary succession occurs after a disturbance
  that leaves no soil
• An example is a cooled lava flow
• Primary succession occurs slowly
• Secondary succession occurs after a disturbance
  that leaves the soil intact
• An example is a forest fire
• Secondary succession can occur very rapidly

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9. Explain the effects of living organisms on the
abiotic environment, with reference to the
changes occuring during primary succession.
IB Exam Question

• An area with no vegetation such as volcanic rock
• Lichens and mosses are the first to colonize
  these areas
• Lichens break down the rock chemically
• Over time, dead lichens and mosses decompose,
  mixing with the decaying rock to form soil
• These pioneer species are gradually replaced by
  others
• Over time, the decaying plants improve soil
  structure
• Eventually a stable community develops