Also topic G.5
Readings
 IB Book pages 112 – 133, 142 – 150, 589 – 595
Topic 5.1 Communities and
Ecosystems
5.1.1 Key Terms
 Species
 Habitat
 Population
 Community
 Ecosystem
 Ecology
4 main components of the
environment
 Hydrosphere – water
 Atmosphere – air
 Lithosphere – rocks/soil
 Biosphere – all living organisms
 The first 3 are abiotic (nonliving) and include things
such as light, heat, minerals, humidity, oxygen
 Biosphere is biotic (living)and includes plants,
animals, bacteria, fungi, protists
Feeding methods
 Autotroph – synthesize organic molecules from
simple inorganic substances.
 Involves photosynthesis as well as chemosynthesis (a
process found in a few extremophile bacteria)
 Because they make food that other organisms use they
are known as producers. Ex) plants, algae, cyanobacteria
 Heterotrophs – obtain organic molecules from other
organisms (autotrophs or other heterotrophs)
 Referred to as consumers
 Include parasites, omnivores, carnivores, herbivores,
detritivores, saprotrophs
 Detritivores eat nonliving organic matter such as feces.
carcasses, dead leaves
 Saprotrophs live on or in non-living organic matter.
Secrete enzymes into the organic matter and absorb
products of their digestion. AKA decomposers. Ex)
bacteria, fungi
Food Chains
 A sequence showing the feeding relationships and
energy flow between species.
 Arrows show who gets eaten by whom
 Ex) herring  seal herring gets eaten by seal
 Food web – an interconnecting series of food chains.
 Food webs illustrate the fact that an animal may eat (or
be eaten by) more that one animal.
Trophic Levels
 T1 - producer
 T2 – primary consumer
 T3 – secondary consumer
 T4 – tertiary consumer
 T5 – quaternary consumer
 Typically only 10% of the energy from one trophic level
is incorporated into the next
Pyramid of Energy
IMPORTANT!! Correct IB unit
for this pyramid is kilojoules
per square meter per year,
kJ/m-2y-1. Use this if you have
to draw a pyramid of energy!!!!
Why is energy lost?
 100% of the food source may not be swallowed (bones
etc…)
 Not all of the food is digestible
 Not all organisms are eaten. They may just die and
decay
 A great deal of energy is lost as heat during cellular
respiration
 Identify the trophic level of each organism in the food
webs on slides 9 and 10.
 Most food chains have 4 trophic levels although they
can have as many as 6.
 Click on the link below to create your own food web.
After placing the animals in the correct trophic level
DO NOT view the web until you have drawn it!
http://www.gould.edu.au/foodwebs/kids_web.htm
Some last words about energy!
 Producers are the most important organism in the
food chain. Sunlight is the initial source of energy for
all communities.
 Sunlight is converted into chemical energy by
producers and transferred to consumers in the various
trophic levels.
 Remember that most of the energy fixed by producers
is lost as heat as it passed from one trophic level to the
next.
Nutrients
 Organisms must recycle the C, N, S, and other
elements necessary for life to exist. These elements as
well as others are trapped in the cells of the organisms
body.
 Decomposers (saprotrophs and detritivores) break
down dead organisms and their wastes and make
recycling of the nutrients possible
5.2 – The Greenhouse Effect
Where is carbon found
 In the biosphere?
 In the lithosphere?
 In the atmosphere?
 In the hydrosphere?
Carbon cycles between these 4
locations
 Photosynthesis – fixes atmospheric carbon into the
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bodies of plants and algae. This carbon is converted
directly into glucose and then into proteins, lipids, and
carbohydrates
Cellular Respiration – organic molecules are broken
down and carbon dioxide is released.
Feeding – carbon is moved from one part of the food
chain to another
Fossilization – carbon is trapped in sediment as coal
and oil
Combustion – burning of biomass and fossil fuels.
5.2.1
 Draw and Label a diagram of the carbon cycle to show
the processes involved.
5.2.3
 Explain the relationship between rises in greenhouse
gases and the enhanced greenhouse effect.
Carbon dioxide levels have been
rising:
 Use of machines, factories, transportation
 Burning of forests to clear land for farming
 Burning of wood or coal for energy
 In general, CO2 levels have risen as much as 25% since
the industrial revolution.
 Look at the graph on page 124. What causes the
fluctuations in the graph?
Greenhouse gases
 Carbon dioxide – produced from burning of fossil fuels
 Methane – produced from cattle ranching,
decomposition of organic waste, production and
distribution of natural gas
 Oxides of nitrogen – made from burning fossil fuel,
use of organic and commercial fertilizers, industrial
processes
How a greenhouse works
 As light penetrates the walls of a glass greenhouse the
light strikes the plants and is transformed into heat.
 Heat has longer wavelengths than light
 Greenhouse glass is not as transparent to heat energy
as it is to light energy so heat is trapped inside keeping
air inside the greenhouse warmer that that outside.
 Carbon dioxide and water vapor are the “glass” of the
earth’s atmosphere.
 See page 125 for an explanation!
The greenhouse effect
a) Short wave solar radiation (light)
b) light penetrates the atmosphere and
passes through the molecules of the
atmosphere
c) Absorption by the ground and conversion
to long wave infrared radiation (heat)
d)This warms the planet
e) Some infrared is lost to space as heat
f) Atmospheric gases particularly water
vapour, carbon dioxide, methane and CFC's
g) Greenhouse gases absorb infra-red
radiation and scatter this rather than letting
it escape to space. In effect this traps the
heat energy.
h) Some light reflects off the outer surface of
the atmosphere and never enters
Enhanced greenhouse effect
 The increase in greenhouse gases will intensify the
Earth’s natural greenhouse effect.
 The Earth’s average temperature will rise
 What impact does the enhanced greenhouse effect
have on the planet?
The impact of greenhouse gases
 As human activity generates more greenhouse gases,
more heat is retained causing earth’s temperature to
rise.
5.2.4-5.2.5 Precautionary Principle
 http://click4biology.info/c4b/5/eco5.2.htm#four This
link has a great explanation of the precautionary
principle. Read it AND the supplemental reading at
the links on the page.
 Basically this is an ethical theory which states that we
should always attempt to prevent harm even if there is
not sufficient data to prove that the activity will have
severe negative consequences.
 Without this principle industry proceeds with
activities until it becomes clear that harm is being
done.
5.2.6 Arctic Ecosystems
 http://click4biology.info/c4b/5/eco5.2.htm#six
 Read both your book (pages 129-130) as well as the
article at click 4 biology. I also have a link to the
article at our wiki.
 Your assessment statement says you must OUTLINE
the consequences of a global temperature rise on arctic
ecosystems.
5.3 Populations
5.3.1 Population Dynamics
 Population size is affected by four main factors:
 Natality – number of new members due to reproduction
 Mortality – number of deaths
 Immigration – members arriving from other places
 Emigration – members leaving the population
5.3.2 Population Growth Curve
__________________________K
This sigmoid curve shows the changes
in population size vs. time. In this
model the population is expanding
into a habitat offering initial low
resistance or low limiting factors.
Note the 3 stages in population
growth: exponential, transitional, and
plateau.
Causes of exponential phase
 Under ideal conditions population growth would be
exponential (2n where n= number of generations or
1,2,4,8,16,32,64….)
 Causes:
 Plentiful resources
 Little or no competition from others
 Favorable abiotic factors such as T, dissolved oxygen
 Little or no predation or disease
Causes of transitional phase
 Increasing competition for resources
 Predators attracted to the growing food supply in the
area
 More disease due to crowding in limited space
 There will not just be a reduced rate of population
growth but also a selection (survival and reproduction)
of these individuals within the population best suited
to using, accessing the resources. Natural Selection is
occurring.
Carrying capacity
 The maximum number of individuals a habitat can
support. Is represented by the letter K.
 Carrying cappacity is defined by limiting factors which
may include:
 Availability of resources
 Build up of wastes (excrement and CO2)
 Predation
 Disease
What is the carrying capacity of
the earth?
 It seems that the human population is continuing to
increase. Is there evidence that the earth is nearing its
carrying capacity for humans? Explain your answer in
a 3-5 paragraph essay. Be sure to cite sources that you
use.
G5 – Population Ecology
G.5.1 – G.5.4
r and K strategists
 r strategy refers to species who produce “disposable offfspring!”
Most invertebrates and “lower” vertebrates can be classified as r
strategists. Offspring are many, require little or no care, mature
rapidly. Die quickly. Opportunistic. Ex.) bacteria
 K strategy refers to species who produce few offspring and
nurture them. The time and effort invested in the young
increases the probability that they will survive
 Study the life history table on pg. 590 of your text and be able to
compare r and K strategy species.
 In unstable environmental conditions, is it better to be
a r or K strategist? Why?
 Ecological disruption favors r strategists. The
organisms that can successfully survive the disruption
are often considered pests by humans. Invasive
species are also typically r strategists.
Estimating population size
 Scientists use the capture-mark-release-recapture
method to do this.
 Animals are captured and marked in some way then
released. A second sample is captured in which some
of the animals will be marked and others will not be
marked.
 See formula on page 591 to calculate population size
 Lab!!!
G.5.4 Estimating size of
commercial fish stock
 How do scientists gather quantitative data about
commercially important fish?
 Survey fishermen
 Research vessels
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Random sampling
Echo sounding
Measuring age of caught fish – otoliths, scales
Coded tags
Mathematical models
Maximum sustainable yield
 The highest proportion of fish that can be removed
from the total population without jeopardizing the
maximum yield in the future.
 What problems exist if the fish stock is too small or too
large?
Promoting fish conservation
 Fish stocks are declining. Commercial fishing may
become nonexistent. Read page 594.
 NOAA Fishwatch link from Hotlink 18.25a
http://www.nmfs.noaa.gov/fishwatch/
 Example: Brown shrimp
http://www.nmfs.noaa.gov/fishwatch/species/brown_
shrimp.htm
 Marine stewardship link from Hotlink 18.25b
http://www.msc.org/