IB Biology Ecology

1. Topic 5 - Ecology
Including Evolution.

2. 5.1 Communities and Ecosystems
Define:
Ecology—the study of relationships between living organisms and
between organisms and their environment.
Ecosystem—a community and its abiotic environment.
Population—a group of organisms of the same species who live in the
same area at the same time.
Community—a group of populations living and interacting with each
other in an area.
Species—a group of organisms which can interbreed and produce
fertile offspring.
Habitat—the environment in which a species normally lives or the
location of a living organism.

3. 5.1 Communities and Ecosystems
5.1.2
autotroph (producer) – organisms that use
an external energy source to produce
organic matter from inorganic raw
materials
Examples: trees, plants, algae, blue-green
bacteria

4. 5.1 Communities and Ecosystems
heterotroph (consumer) – organisms that
use the energy in organic matter,
obtained from other organisms
Three Types:
1. consumers
2. detritivores
3. saprotrophs

5. 5.1 Communities and Ecosystems
1. Consumers – feed on other living things
2. Detritivores – feed on dead organic
matter by ingesting it
3. Saprotrophs (decomposers) – feed on
dead organic material by secreting
digestive enzymes into it and absorbing
the products

6. 5.1 Communities and Ecosystems
5.1.4
Describe what is meant by a food chain
giving three examples, each with at least
three linkages (four organisms).
A food chain is a sequence of relationships
between trophic levels where each
member feeds on the previous one.

7. 5.1 Communities and Ecosystems
5.1.5
Describe what is meant by a food web.
A food web is a a diagram that shows the
feeding relationships in a community. The
arrows indicate the direction of energy
flow.

8. 5.1 Communities and Ecosystems
5.1.6
Define trophic level.
A trophic level is where an organism is
positioned on a food web.
Producer
Primary consumer
Secondary consumer
Tertiary consumer

9. 5.1 Communities and Ecosystems
5.1.7
Deduce the trophic level of organisms in a
food chain and a food web. (3)
• The student should be able to place an
organism at the level of producer, primary
consumer, secondary consumer etc, as
the terms herbivore and carnivore are not
always applicable.

10. 5.1 Communities and Ecosystems
5.1.8
Construct a food web containing up to 10
organisms, using appropriate information.

11. 5.1 Communities and Ecosystems
5.1.9
State that light is the initial energy source for
almost all communities.
• xref- Photosynthesis

12. 5.1 Communities and Ecosystems
5.1.10
Explain the energy flow in a food chain.
• Energy losses between trophic levels
include material not consumed or material
not assimilated, and heat loss through cell
respiration.

13. 5.1 Communities and Ecosystems
5.1.11
State that when energy transformations take
place, the process is never 100% efficient

14. 5.1 Communities and Ecosystems
5.1.12
Explain reasons for the shape of pyramids
of energy.
• A pyramid of energy shows the flow of
energy from one trophic level to the next in
a community. The units of pyramids of
energy are therefore energy per unit area
per unit time, e.g. KJ m-2
yr-1

15. 5.1 Communities and Ecosystems

16. 5.1 Communities and Ecosystems

17. 5.1 Communities and Ecosystems
5.1.13
Explain that energy enters and leaves ecosystems,
but nutrients must be recycled.
Energy enters as light and usually leaves as heat.
Nutrients do not usually enter an ecosystem and
must be used again and again (nutrient cycles).
Nutrients can be substances such as Carbon
dioxide, Nitrogen, and Phosphorus

19. Key processes in the Carbon cycle
• Combustion
• Cell respiration
• Photosynthesis
• Fossilisation
• Interaction between living organisms

20. The layers of
the
atmosphere
The troposphere is the part of the
atmosphere in the biosphere
The stratosphere contains the
ozone layer
The stratosphere is also a zone of
warm air that keeps a lid on the
troposphere. It does not mix with
the upper atmosphere
© Windows to the Universe© Text 2007 Paul Billiet ODWS

21. The Greenhouse Effect
• Earth has a natural greenhouse effect
• This is important to prevent large
fluctuations in temperature
• Without a greenhouse effect on Earth, we
would not have life as we know it.

23. Greenhouse Effect
Light from the sun has short wavelengths
and can pass through most of the
atmosphere.
This sunlight warms the Earth which in turn
emits long wave radiation.
This long wave radiation is bounced back by
the greenhouse gases, such as carbon
dioxide, methane, CFCs, water vapour,
and sulphur dioxide

24. The Greenhouse Effect
• The molecules of some gases in the
atmosphere absorb heat energy and
retain it
• This can be a good thing
• Without an atmosphere the Earth would
have same temperature as the moon
• Moon mean surface temperature -46°C
• Moon temperature range: -233 to +123°C
© 2007 Paul Billiet ODWS

25. The Greenhouse Gases
• H2O vapour
• CO2
• CH4
• NOx
• CFC
© Oceanworld 2005 Robert R Stewart
© Text 2007 Paul Billiet ODWS

26. The Greenhouse Gases
• Water vapour in the atmosphere is stable
• The atmosphere is saturated
• CO2 levels are currently rising
• They have varied in the past
• Methane levels are increasing:
as more cattle are farmed, as more paddy
fields are planted, as permafrost melts
• NOx levels increase due to increased
circulation of motor vehicles
© 2007 Paul Billiet ODWS

27. Mauna Loa Observatory
© Mauna Loa Observatory Site
© Earth System Research Laboratory
© Earth System Research Laboratory

28. Carbon dioxide a greenhouse
gas
© Mauna Loa Observatory Site

29. South Pole Data

30. Samoa data

31. © Australian Antarctic Division
© New Scientist : Environment

32. Levels during the last ice age
© Dennis Hartmann: Universoty of Washington: Department of Atmospheric Sciences

33. Out of the ice age

34. Since the Industrial
Revolution
Concentration of Carbon Dioxide from trapped air measurements for the DE08 ice core near the summit
of Law Dome, Antarctica. (Data measured by CSIRO Division of Atmospheric Research from ice cores supplied by
Australian Antarctic Division)

35. Is it really getting warmer
1979 2003
© NASA

36. 5.2 The ENHANCED greenhouse
effect
Phenomenon
The mean global temperature has
risen about 1 degree Celsius since
1856. We saw an increase
between 1910 and 1940, and from
1970 onwards.

37. 5.2 Enhancing the greenhouse
Effect
Human Activities
• Increased burning of fossil fuels releasing greenhouse
gases (CO2, oxides of Nitrogen)
• Deforestation – less trees to convert CO2 back to O2
• Raising cattle and paddy fields release methane
• CFCs were used as a propellant in aerosols and as a
coolant in refrigerators, freezers and air conditioning
units. Old cooling machinery can still leak CFCs and
need to be disposed of carefully – CFCs are persistent
• Other industrial activities that release other
greenhouse gases

38. The Precautionary Principle
• The precautionary principle holds that, if the
effects of a human-induced change would be
very large, perhaps catastrophic, those
responsible for the change must prove that it
will not do harm before proceeding.
• This is the reverse of the normal situation where
those who are concerned about the change
would have to prove that it will do harm in order
to prevent such changes going ahead.

39. Evaluate the precautionary
principle…
• …..as a justification for strong action in response to the
threats posed by the enhanced greenhouse effect
• Economic harm Vs harm to environment for future
generations
• Should the health and wealth of future generations be
jeapardised?
• Is it right to knowingly damage the habitat of species
other than humans? Cause extinction?
• Need for international cooperation
• Inequality between those contributing most to the harm,
and those who will be most harmed

40. The consequences
• Sea level rise
Changing sea ice...
• Flooding coastal areas
Reduced agricultural land
Displacement of populations
• Climate change and changing weather patterns
• Displacement of ecosystems
Change in range of insect vectors of pathogens
Reduced biodiversity
© 2007 Paul Billiet ODWS

41. The consequences
• Increased rates of photosynthesis
• Increased agricultural production at high
latitudes
• BUT faster growth means:
less protein in cereals
trees taller and more exposed to storm
damage
© 2007 Paul Billiet ODWS

42. Knock-on effects
• Increased temperature melts the permafrost
• Frozen plant remains decompose
• More methane released
• Similarly soils will lose organic carbon (humus)
more rapidly in a warmer climate
• Ice caps melt more sea exposed
• Snow reflects light (high albedo)
• Water absorbs light, increases warming
• More CO2 dissolving in water lowers pH
• Currently this is buffered and remains stable
• Eventually pH will drop sea life will die CO2
produced as organisms decompose© 2007 Paul Billiet ODWS

43. What can be done?
Reduce carbon emissions
• Improve mass transport systems (public
transport)
• Design more efficient motors
• Design alternative power sources
• Hydrogen powered motors
BUT problems of fuel reservoir, delivery,
fabrication
• Renewable energy (wind, tidal, hydro,
geothermal, biomass)
BUT growing crops for biofuel reduces farmland
available for food
Hydroelectric dams disrupt river ecosystems
• Nuclear power© 2007 Paul Billiet ODWS

44. What can be done?
Increase natural CO2 sequestering
• Reduce deforestation
• Increase reforestation
© 2007 Paul Billiet ODWS

45. What can be done?
Artificial CO2 sequestering
• Filter CO2 sources using hydroxide
scrubbers
• Injection of CO2 into deep ocean layers
Forms CO2 reservoirs
Impact on sea life unknown
• Injecting CO2 into disused oil wells
• Mineral deposition as carbonates
© 2007 Paul Billiet ODWS

46. The bottom line
Two factors will ultimately govern what happens:
1. Human population growth
More people means greater demand for non-
renewable resources
2. The ecological footprint of each individual
human
Higher standards of living usually means higher
consumption of fossil fuels
The planet will look after itself in the end
There are plenty of examples where human
communities have disappeared because they
outstripped the environmental resources
© 2007 Paul Billiet ODWS

47. The planet will look after itself in the
end
• Easter Island (Rapanui) in
the Pacific
• Settled between AD900 and
1200
• Community in severe
decline AD 1700
• Cause: excessive
deforestation
© Text 2007 Paul Billiet ODWS
The Moai statues, Easter Island © Martin Gray, World
Mysteries

48. The planet will look after itself in the
end
• Chaco Canyon, New
Mexico
• Anasazi culture
• AD 850 – 1250
• Cause: Deforestation
combined with a
decline in rainfall
© New Mexico Tourism Department
© Text 2007 Paul Billiet ODWS

49. The planet will look after itself in the
end
• Mesopotamia
• Sumerian civilization
• 3100 – 1200 BC
• Increased salt levels
in soil due to irrigation
systems & arid
environment
• Reduced food yield
© Text 2007 Paul Billiet ODWS
© Asociación Cultural Nueva Acrópolis en Barcelona

50. The planet will look after itself in the
end
• Greenland
• Viking colony
• AD982 – 1350
• Cause: Deforestation,
soil degradation &
cooling of the climate
© Emporia State University
© Text 2007 Paul Billiet ODWS

51. forumpolitics.com/pics/earth-photo.jpg
Who’s next?
© NASA

52. 5.3 Populations
5.3.1
Outline how population size is affected by
natality, immigration, mortality and
emigration.

53. 5.3 Populations
• Natality – offspring are produced and
added to the population
• Mortality – individuals die and are lost
from the population
• Immigration – individuals move into the
area from somewhere else and add to the
population
• Emigration – individuals move out of the
area and are lost from the population

54. 5.3 Populations
5.3.2
Draw a graph showing
the sigmoid (S-
shaped) population
growth curve.

56. 5.3 Populations
5.3.3
Explain reasons for the exponential growth
phase, the plateau phase and the
transitional phase between these two
phases.

58. 5.3 Populations
Exponential Phase
Population increases exponentially because
the natality rate is higher than the mortality
rate. This is because there is an
abundance of food, and disease and
predators are rare.

59. 5.3 Populations
Transitional Phase
Difference between natality and mortality
rates are not as great, but natality is still
higher so population continues to grow,
but at a slower rate.
Food is no longer as abundant due to the
increase in the population size. May also
be increase predation and disease.

60. 5.3 Populations
Plateau Phase
Natality and mortality are equal so the population
size stays constant.
Limiting Factors:
• shortage of food or other resources
• increase in predators
• more diseases or parasites
If a population is limited, then it has reached its
carrying capacity

61. 5.3 Populations
Carrying capacity
The maximum population size that can be
supported by the environment

63. 5.3 Populations
5.3.4
List three factors which set limits to
population increase.
Limiting Factors:
1. shortage of food or other resources
2. Increase in predators
3. More diseases or parasites

64. 5.3 Populations
Random sample
In a random sample, every individual in a
population has an equal chance of being
selected.

65. 5.3 Populations
The population size of an animal species can be estimated
a capture-mark-release-recapture method.
• Various mark and recapture methods exist.
• The Lincoln index states that
population size =
where . . .
• n1= number of individuals initially caught, marked and released
• n2 = total number of individuals caught in the second sample
• n3 = number of marked individuals in the second sample
3
21
n
xnn

66. 5.3 Populations
• Random sampling of plant species usually
involves counting numbers in small,
randomly located, squares within the total
area.
• These squares are called QUADRATS
and are used to compare the population
numbers of two plant species.

67. 5.3 Populations
1. mark out gridlines along two edges of the
area

70. 5.3 Populations
1. mark out gridlines along two edges of the
area
2. use a calculator or tables to generate two
random numbers to be used as co-
ordinates. Place a quadrat at the co-
ordinates
such as 14, 31

72. 5.3 Populations
2. use a calculator or tables to generate two
random numbers to be used as co-
ordinates. Place a quadrat at the co-
ordinates
3. count how many individuals are inside the
quadrat. Repeat 2 and 3 as many times
as possible

74. 5.3 Populations
3. count how many individuals are inside the
quadrat. Repeat 2 and 3 as many times
as possible
4. Measure the total size of the area
occupied by the population, in square
meters

75. 5.3 Populations
4. Measure the total size of the area
occupied by the population, in square
meters
5. calculate the mean number of plants per
quadrat. Then calculate the population
size using the following equation:

76. 5.3 Populations
quadrateachofarea
areatotalquadratpernumbermean
sizepopulation
×
=

77. 4.5 Human Impact
4.5.1
Outline two local or global examples of
human impact causing damage to an
ecosystem or the biosphere. One example
must be the increased greenhouse effect.

78. 5.4 Evolution
5.4.1
Define Evolution—the process of cumulative
change in the heritable characteristics of a
population.
Macroevolution – the change from one species to
another. i.e. – reptiles to birds
Microevolution – the change from one variation
within a species to another. i.e. – a Chihuahua
and a Great Dane

79. 5.4 Evolution
Evidence for evolution….
• Fossil record
• Selective breeding of domesticated
animals
• Homologous structures

80. The Fossil Record
• Darwin first collected convincing evidence for biological
evolution
• Earlier scholars had recognised that organisms on Earth had
changed systematically over long periods of time.
• Because bottom layers of rock logically were laid down earlier
and thus are older than top layers, the sequence of fossils also
could be given a chronology from oldest to youngest.
• Today, many thousands of ancient rock deposits have been
identified that show corresponding successions of fossil
organisms.
• Hundreds of thousands of fossil organisms, found in well-dated
rock sequences, represent successions of forms through time
and manifest many evolutionary transitions.

81. Life Form Millions of Years
Since First Known
Appearance
• Microbial (procaryotic cells) 3,500
• Complex (eucaryotic cells) 2,000
• First multicellular animals 670
• Shell-bearing animals 540
• Vertebrates (simple fishes) 490
• Amphibians 350
• Reptiles 310
• Mammals 200
• Nonhuman primates 60
• Earliest apes 25
• Ancestors of humans 4
• Modern humans 150,000 years

82. Archaeopteryx

83. Selective breeding

84. Homologous structures
• Inferences about common descent are reinforced by
comparative anatomy. For example, the skeletons of
humans, mice, and bats are strikingly similar, despite the
different ways of life of these animals and the diversity of
environments in which they flourish.
• The correspondence of these animals, bone by bone, can
be observed in every part of the body, including the limbs;
yet a person writes, a mouse runs, and a bat flies with
structures built of bones that are different in detail but
similar in general structure and relation to each other.
• Scientists call such structures homologous structures
and have concluded that they are best explained by
common descent.

85. The pentadactyl limb

86. 5.4 Evolution
5.4.3
Populations tend to produce more offspring
than the environment can support.

87. 5.4 Evolution
5.4.4
• The consequence of the potential
overproduction of offspring is a struggle
for survival.
• More offspring are produced than can be
supported, therefore there is a struggle to
survive, where some live and some die.

88. 5.4 Evolution
5.4.5
Members of a
species show
variation.

89. 5.4 Evolution
5.4
Explain how sexual reproduction promotes
variation in a species.
• Independent assortment
• Crossing over
• Random fertilisation
• Mate selection

90. Natural selection – the mechanism
of evolution
• Since organism’s traits vary, some
organisms are more adapted to survival
than others.
• When there is a struggle to survive those
with favorable traits tend to survive long
enough to pass them on.
• Those that have less favorable traits die
before being able to pass the traits on.

91. 5.4 Evolution
5.4.7
Explain how natural
selection leads to
evolution
• The Darwin–Wallace
theory is accepted by
most as the origin of
ideas about evolution
by means of natural
selection

92. • 1854 - Wallace left Britain on a collecting expedition to the Malay
Archipelago (now Malaysia and Indonesia). He spent nearly eight years
in the region collecting almost 110,000 insects, 7500 shells, 8050 bird
skins, and 410 mammal and reptile specimens, including over a
thousand species new to science; some of his specimens can be seen
in the Sarawak museum.
• His best known discoveries are probably Wallace's Golden Birdwing
Butterfly Ornithoptera croesus
• The book he wrote describing his work and experiences, The Malay
Archipelago, is the most celebrated of all travel writings on this region,
and ranks with a few other works as one of the best scientific travel
books of the nineteenth century.

93. • In February 1855, whilst staying in Sarawak,
Wallace wrote what was to become one of the
most important papers on evolution.
• Wallace's "Sarawak Law" paper made a big
impression on the famous geologist Charles
Lyell.
• Soon after Darwin had explained his theory of
natural selection to Lyell (during a visit he
made to Down House in April 1856) Lyell sent
a letter to Darwin urging him to publish the
theory lest someone beat him to it.
• Darwin began to write On the Origin of
Species.

94. • 1858 - the idea of natural selection as the
mechanism of evolutionary change
occurred to Wallace .
• He wrote out his ideas in full and sent them
off to Charles Darwin, who he thought
might be interested.
• Unknown to Wallace, Darwin had in fact
discovered natural selection about 20 years
earlier, and was part way through writing
his "big book" on the subject.
• Darwin was therefore horrified when he
received Wallace's letter, and appealed to
his influential friends Charles Lyell and
Joseph Hooker for advice on what to do.
• Lyell and Hooker presented Wallace's
essay, along with two excerpts from
Darwin's writings on the subject, to a
meeting of the Linnean Society of London
in July 1858.
• These documents were published together
in the Society's journal on 20 August of the
same year as the paper

95. 5.4 Evolution
5.4.8
Explain two examples of evolution in
response to environmental change; one
must be multiple antibiotic resistance in
bacteria…..
Evolution in bacteria
and the peppered moth (Biston betularia) is
another good example!.....

96. Example 1:’Peppered Moth’

101. Example 2:Resistance to
antibiotics in bacteria.
• If a culture of bacteria (eg.within a sick patient) is treated
with antibiotics, Most of the bacteria are killed. A small
number that naturally have genes resistant to antibiotics
will survive.
• It is important to note that these bacteria did not "learn" to
resist antibiotics. These bacteria have mutated genes that
somehow allowed them to resist antibiotics.
• These surviving bacteria will reproduce and pass on their
resistant genes. Natural Selection “chose” the antibiotic
resistant ones because the rest of bacterial population is
killed by the antibiotic.
• These surviving Mutant bacteria can become a problem
when trying to kill a bacterial infection in a patient, because
if the bacterium is resistant to the antibiotics given, then it
can't be killed.
• Someone has to come up with a new antibiotic that it is not
resistant to, which can be a difficult expensive process

102. 5.5 Classification
5.5.1
Outline the binomial system of nomenclature
(also referred to as a scientific name)
Swedish botanist, Carolus Linnaeus (1707-
1778)
Internationally recognised name for each
species

103. 5.5 Classification
Rules for binomial nomenclature:
1. The first name is the Genus name
2. The Genus name is CAPITALISED
3. The second name is the species name
4. The species name is not capitalised
5. Italics are used if the name is printed
6. The name is underlined if handwritten
Homo sapiens, Panthera leo, etc.

104. 5.5 Classification
5.5.2
List the seven levels in the hierarchy of taxa
- use an example from two different
kingdoms for each level.

105. Kingdom
Phylum
Class
Order
Family
Genus
Species
Animalia
Chordata
Mammalia
Cetacea
Balaenopteridae
Balaenoptera
musculus
Plantae
Coniferophyta
Pinopsida
Pinales
Taxodiaceae
Sequoia
sempervirens
Kings Play Chess On Folding Glass Stools
Blue Whale Coast Redwood
King Phillip Came Over For Good Soup
KissingPrettyCuteOtterFeels
GrossSometimes
or make your own!

106. Bryophyta – mosses and liverworts
(0.5m)
• No roots, just rhizoids
• Small
• Spores produced in capsules
Mosses have simple
leaves and stems
Liverworts have
a flattened “thallus”

107. Filicinophyta – ferns (<15m)
• Roots, leaves and short (non-woody)stems
• Pinnate leaves
• Curled up in buds
• Spores in sporangia (underside of leaves)
shallow roots

108. Coniferophyta – conifers (100m)
• Shrubs or trees with roots, leaves and woody
stems
• Produce seeds in female cones
(Male cones  pollen)

109. Angiospermatophyta – flowering
plants (100m)
• Roots, stems and leaves
• If shrubs or trees, woody stems
• Produce seeds inside ovaries.
Fruits develop from
ovaries, to disperse
seeds

110. Porifera (sponges)
• Poriferans don't have mouths;
instead, they have tiny pores in
their outer walls through which
water is drawn.

111. Cnidaria (corals, anemones and jellyfish)
• Single opening to stomach, that functions as both
mouth and anus
• It has radial symmetry
• Armed with stinging cells called nematocysts.

112. Platyhelminths (flatworms)
• Bilaterally
symmetrical
• Triploblastic
(composed of three
fundamental cell
layers)
• no body cavity other
than the gut and lack
an anus

113. Annelida (segmented worms)
• Segmented, long body
• Mouth and anus

114. Mollusca
• The body has a head, a
foot and a visceral mass,
covered with a mantle
that typically secretes the
shell.
• The buccal cavity, at the
anterior of the mollusc,
contains a radula — a
ribbon of teeth
• The ventral foot is used in
locomotion.
• Molluscs are coelomate.

115. Arthropoda
• Exoskeleton made of chitin (may be
strengthened with calcium carbonate)
• Jointed limbs

116. Design a dichotomous key for 8
organisms