5. Ecology and evolution

IB DIPLOMA PROGRAMME
THE IB LEARNER PROFILE:
-Inquires: They develop their natural curiosity. They acquire the
skills necessary to conduct inquiry and research and show
independece in learning.They actively enjoy learning and this
love of learning will be sustained troughout their lives.
-Knowledgeable: They explore concepts, ideas and issues that
have local and global significance. In so doing, they acquire in
depth knowledge and develop understanding across a broad
and balanced range dsciplines.
-Thinkers: They excercise initiative in applying thinking skills
critically and creatively to recognize and approach complex
problems, and make reasoned,ethical decisions.


Communicators: They understand and express ideas and information confidently and creatively in
more than one language and in a variety of modes of communication. They work effectively and
willingly in collaboration with others

-Principled: They act with integrity and honesty, with a strong sense of fairness, justice, and respect for
the dignity of the individual, groups, and communities.They take responsibility for their own actions
and the consequences that accompany them.

-Open minded: They understand and appreciate their own cultures and personal histories, and are open
to the perspectives, values, and traditions of other individuals and communities. They are
accustomed to seeking and evaluating a range of points of view, and are wiling to grow from the
experience.

-Caring: They show empathy, compassion, and respect towards the needs and feelings of others. They
have a personal commitment to service, and act to make positive difference to the lives of others
and to the environment.

- Risk takers: They approach unfamiliar situations and uncertainty
with courage and forethought, and have the independence of spirit
to explore new roles, ideas, and strategies. They are brave and
articulate in defending their beliefs.

- Balanced: They understand the importance of
intellectual, physical, and emotional balance to achieve personal
well-being for themselves and others.

- Reflective: They give thoughtful consideration to their own learning
and experience. They are able to assess and understand their
strenghts and limitations in order to support their learning and
personal development.

TOPIC 2: ECOLOGY AND
EVOLUTION

2.1.- COMMUNITIES AND ECOSYSTEMS
WORD DEFINITION
Habitat: The environment in which a species normally lives, or the
location of a living organism.
Species: A group of organisms that can be interbreed and produce fertile
offspring.
Population: A groups 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.
Ecosystem: A community and its abiotic environment.
Ecology: The study of relationships between living organisms and
between organisms and their environment.

ECOLOGY:
• Living organisms do not live in isolation. If we study
organisms in their natural habitat, we invariably find that
they live with other members of their species and with
populations of other species, in what ecologists refer to as
a community.
• Living organisms depend on their environment, whether it
consists of air, water, soil or rock. There are many types of
relationships between organisms and their environment.
• The community of organisms in an area and their non-living
environment can be considered to be a single higly complex
interacting system, known as ecosystem

2.1.1.- Food Sources
WORD DEFINITION
Autotroph: An organism that synthesizes its organic molecules from simple
inorganic substances
Heterotroph: An organisms that obtains organic molecules from other organisms
Consumer: An organism that ingests organic matter that is living or recently
killed
Detritivore An organism that ingests non-living organic matter
Saprotroph: An organism that lives on or in non-living organic matter, secreting
digestive enzymes into it and absorbing the products of digestion

2.1.1.- Food Sources
All organisms need a supply of organic molecules, such as glucose and aminoacids.
They are needed for growth and reproduction.

Methods of obtaining organic molecules:
1.- Some organisms make their own organic molecules from carbon dioxide and other
simple inorganic substances: Autotroph organisms (self feeding)
2.- Some organisms obtain their organic molecules from other organisms and of
digesting it so that it can be absorbed:
2.1.: By ingesting organisms and digesting them inside the gut, these organisms are
called consumers
2.2.: By ingesting dead organic matter derived from living organisms and by
digesting it inside the gut, these organisms are called detritivores
2.3.: By secreting digestive enzymes into dead organic matter derived from living
organisms and by absorbing the products of externl digestion, these organisms are
called saprotrophs

2.1.2.- Food chains
• A food chain is a sequence of organisms, each of which feeds on the
previous one.
• There are usually between 2 and 5 organisms in a food chain
• Producers are autotrophic. They are usually photosynthetic
organisms, such as terrestrial green plants and phytoplankton. As
theydo not obtain food from other organisms, producers are always
the first organisms in a food chain.
• The subsequent organisms are consumers. Primary consumers feed
on producers, secondary consumers feed on primary consumers,
tertiary consumers feed on secondary consumers and so on.
• Consumers obtain energy from the organic matter of the organisms
on which they feed. The arrows in a food chain therefore indicate
the diretion of energy flow

2.1.3.- Trophic levels
• The categories of organism, producer, primary
consumer, secondary consumer and so on, are
called TROPHIC LEVELS.
• The word trophic means “nourishment” in old
Greek.
• Trophic levels:
- Producer
- Primary consumer
- Secondary consumer
- Terciary consumer …..

2.1.3.- Food webs
• Trophic relationships within ecological
communities tend to be complex and web-like.
This is because most species fed on by more than
one species and most consumers feed on more
than one species.
• When a food web is constructed, organisms at
the same trophic level are often shown at the
same level in a web. This isn’t always possible, as
some organisms feed at more that one trophic
level.

2.1.4.- Energy flow in food chains
• For most biological communities, the initial source of
energy is LIGHT captured by plants undergoing
photosynthesis.
• Plants convert light into chemical energy.
• A portion of this energy is used by the plant in cellular
respiration and is ultimately released as waste heat to the
environment.
• Energy stored in plant tissues is passed to the next trophic
level, if plant matter is eaten by primary consumers.
• Also a portion of the plant’s material may become detritus,
in which case stored energy can be passed on to
Saprotrophs or Detrivores.

• The energy stored in plant matter eaten by
primary consumers can be used directly as a
source of energy for cellular respiration. This
energy can also be released as waste heat, from
the primary consumers.
• The alternative is that organic matter containing
stored energy in the primary consumer can be
eaten by a secondary consumer.
• In addition, undigested plant matter released as
feces by the primary consumer contains available
energy for saprotrophs and detrivores to use.

• Energy is passed from consumer to consumer in a
food chain, but with every transformation energy
is lost from the community in heat generated by
respiration.
• One of the laws of physics states that energy
transformations are never 100% efficient.
Further, when an animal eats, a portion of its
food is never absorebed and is egested as feces.
• Some material such as bones or air, may not be
eaten. That energy can be used by decomposers.

2.1.5.- Pyramids of energy
• The amount of energy converted to new biomass
during a given time period by each trophic
level, in an ecological community, can be
represented by a pyramid of energy.

• The width of the bars is proportinal to the energy in
that trophic level.
• There’s always loss of energy trough the food chain.
• To be more accurate, the boxes should be drawn to
have relative widths that match the relative energy
content at each trophic level.
• Pyramids of energy show how much energy is lost
between trophic levels. Typically only between 5% and
20% of the energy in one trophic level is passed on to
the next.
• As a result there is less and less energy available to
each succesive trophic level. Eventually there is too
little energy to sustain a population, that is why food
chains are limited in lenght.

2.2. POPULATIONS
• 2.2.1. POPULATION GROWTH:

• Population studies, often focus on variables
such as population size, density, growth and
the interaction of the population with the
biotic and abiotic factors of the habitat it
occupies

Sigmoid S-Shaped growth curve
• The figure, shows the population growth of a
group of organisms, kept in controlled conditions,
including a constant supply of food. The figure
illustrates a pattern called the Sigmoid or S-
Shaped, growth curve.
• The S-curve is representative of what happens
when a population colonizes a new habitat. With
limited environmental resistance, a population
will growth exponentially. At this stage, birth rate
(natality) is higher than death rate (mortality).

• As population density increases, various
density- dependent factors begin to limit
population growth.
• Examples of such limiting factors include:
1.- Competition for resources
2.- toxic products of metabolism
3.- Increase in predation
4.- Increase in the incidence of disease.
The initial result is that natality slows in
relation to mortality. This is the transition
phase of the curve.

• The maximum size of a population that and
environment can support is its carrying
capacity *
• In the sigmoid growth pattern, when a
population reaches its carrying capacity, the
population will stop growing and natality and
mortality will be equal. This is referred to as
the plateau phase on the S-curve.
* The carrying capacity of a biological species in an environment, is the
population size of the species that the environment can sustain
indefinitely, given the food, habitat, water and other necessities
available in the environment.

• Some populations can overshoot the carrying
capacity of the environment. The result is a
“boom-and-bust” pattern.

DATA BASES IN ECOLOGICAL RESEARCH:
Advances in technology have meant that the
creation and publication of data is increasingly
exceeding the rate at which it can be analysed.
Hypothesis testing is increasingly possible by
extracting data from a database rather than the
researcher directly collectong the data
themselves.

• Unlike energy, which flows through an ecosystem
and must be constantly replenished, nutrients are
recycled within ecosystems. Nutrients are
chemicaql elements such as carbon, nitrogen and
phosphorus. The basic pattern of nutrient cycles
involves three stages:
1.- There is an inorganic reserve of each element in
the ecosystem, for example carbon dioxide in the
atmosphere. Autotrophs abosrb the element
from this reserve and convert it into organic
compounds, for example nitrate is converted into
amino acids.

2.- Consumers obtain the element in organic form, by
feeding on autotrophs or other consumers.For
example, elephants obtain amino acids, containing
nitrogen, from the plants that they eat.
3.- Dead organic matter, containing the element is
released when organisms excrete or egest waste
material or they die. The element would remain locked
up in the organic matter if it were not for the activity of
saprothophs (fungi, bacteria) or detritivores. These
organisms therefore, have a crucial role in recycling.
For example: saprotrophs release nitrogen in the form of
ammonia, which is converted by bacteria into nitrates.

2.3.1.- THE CARBON CYCLE
• As life is based on carbon compounds, the
carbon cycle is especially important. In marine
and aquatic ecosystems, the inorganic reserve
of carbon is: dissolved cabron dioxide and
hydrogen carbonate, which is absorbed by
producers, and by various means is released
back into the water.

2.3.2.- THE GREENHOUSE EFFECT
• In a greenhouse, light enters and warms up
the solid surfaces.The glass prevents the heat
from escaping and the temperature inside the
greenhouse rises. A similar sequence of events
happens inside an automobile with its
windows closed, when it has been parked in
full sunlight. The rise in temperature is known
as the greenhouse effect. It also occurs in the
Earth’s atmosphere.

• Much of the light from the sun has short
wavelenghts and high energy, and it passes
through the atmosphere, to the Earth’s
surface.
• The warm surface of the Earth re-emits
energy, but with much longer wavelenghts,
and lower energy than the light from the sun.
• Most of this re-emitted energy is infrared
radiation. Certain gases in the atmosphere
absorb infrared radiation and re-emit it, some
towards the Earth.

• Certain gases in the atmosphere absorb
infrared radiation and re-emit it, some
towards the Earth. The effect is GLOBAL
WARMING and makes the Earth habitable.
• Without the Greenhouse Effect it is estimated
that the mean temperature at the Earth’s
surface would be about -18ºC.
• The main gases that contribute to the global
warming, known as greenhouse gases, are
carbon dioxide, methane and oxides of
nitrogen.

2.3.3.- The enhanced greenhouse
effect
There is a considerable evidence that the Earth
is becoming warmer.

• An obvious explanation for the global warming is
an enhanced greenhouse effect caused by human
additions of greenhouse gases to the
atmosphere, mostly trough fossil fuel burning.
• Now we know that the atmospheric levels of
carbon dioxide have grown since the past
century; due to the increase of industralization.
• Carbon dioxide is not the only greenhouse gas
and the concentrations of others, including
methane and nitrogen oxides, have also been
rising as a result of human activities.

• ALMOST ALL CLIMATE SCIENTISTS AGREE THAT
THESE RISES ARE NOT MERELY CORRELATED
WITH GLOBAL WARMING, THEY ARE THE
CAUSE OF IT.

2.3.4. The precautionary principle
• Governments are responsable for protecting
when assessing new techonolgies. This requires a
balance between encouraging innovation and
minimizing risk. Scientists are often asked to
advise governments about risks.
BUT HOW SHOULD GOVERNMENTS ACT WHEN
SCIENTISTS OFFER INCOMPLETE INFORMATION
OR CONTESTED KNOWLEDGE?

• Traditional risk analysis involves assessing the
likelihood that new technologies will harm the
public. This puts the burden of proof on those
who are concerned about the risk. However,
damage may already have been done long before
evidence harm exists.
• A contrasting approach is the precautionary
approach. In the late 1970s, when private
landowners in Germany observed that significant
tracts of forest were being killed. There was not
yet scientific proof that ACID RAIN was the cause,
but the government acted to regulate power-
plant emissions. more strictly anyway

Precautionary principle
vs.
Anti-precautionary principle
EXAMPLE:
In 1997, The European Union banned the import of products from
cattle that had been treated with bovine somatotropin (BST), a
hormone that when given to cattle, increases milk yields by about
10%. The USA inmediately appealed to the World Trade
Organization (WTO). They argued that there was no known example
of humans being affected by BST. The WTO gave EU a year to
privide evidence of harm to humans. If they could not do this, the
ban would have be lifted. The WTO was applying what we might call
the anti-precautionary principle: it is for society to show that
something is dangerous, instead of requiring the perpetrator to
show it is safe.

Excersice: Thinking about science
DRUG TESTING
• The precautionary principle argues that the action to protect must
precede certainty of risk. The principle is particularly relevant when
the potential consequences of the activity are catastrophic. Some
drugs have had catastrophic effects when they were introduced
without effective testing.
• In some jurisdictions, a relatively conservative protocol has emerged
for approval of drugs so that they become available for later than in
other jurisdictions. Patient advocacy groups often exert pressure for
the process to be expedited. Tests and trials make drugs less risky,
but the risk is never removed entirely. Urging that drugs be made
available earlier is equivalent to urging that grater levels of risk be
accepted.

QUESTIONS:
• 1) Can it be argued that there is a scientific
standard for acceptable levels of risk?
• 2) If there were a shortage of milk produced
globally, would that make the possible risk from
BST more acceptable?
• 3) If there are no effective treatments forb a
disease, does that make it more acceptable to
release a drug for use, before it has been
subjected to all normal testing protocols?

The precautionary principle applied to
the grenhouse effect
• The UN Framework Convention on Climate
Change made the case in 1992 that: Parties
should take precautionary measures to
anticipate, prevent or minimize the causes of
climate change and mitigate its adverse
affects. Where there are threats of serious or
irreversible damage, lack of full scientific
certainty should not be used as a reason for
postponing such measures.

• Given the dependence of current economic systems on
fossil fuels, others argue that the data to support the
benefit of significant reductions in carbon dioxide
emissions is insufficient to justify the economic
consequences. It is not certain that adverse effects on
the environment would occur if no such action was
taken, neither can we be certain that limiting emissions
would be sufficient to slow current global warming
trends.
• Those who support the precautionary principle argue
that there ir enough preliminary evidence of both the
likely harm of emissions continuing to increase and the
benefits of limiting emissions, to promt action. Most
reasonable scientist agree that the impacts of
greenhouse gas emissions on climate change are
significant and potentially catastrophic.

• One politician representing the island state of
Vanuata, Ambassador to the UN Robert van
Lierop, puts it as follows:
For us, the precautionary principle is much more
than a semantic or theoretical excercise. It is
and ecological and moral imperative. We do
not have the luxury of waiting for conclusive
proof, as some have suggested in the past. The
proof we fear will kill us.

2.4. EVOLUTION
• The word EVOLUTION, has several different meanings.
1) Biological meaning: evolution is the process by which
living organisms are formed, by gradual change, from
previous organisms.

As currently understood, the process takes many
generations and works at the level of a population.
Individual organisms cannot evolve because the
characteristics that they acquire during their lifetime
cannot be inherited by the next generation.

Charles Darwin

12 February 1809 – 19 April
1882; was an English
naturalist. He established
that all species of life
have descended over
time from common
ancestry, and proposed
the scientific theory that
this branching pattern of
evolution resulted from a
process that he called
natural selection

Charles Darwin
• Charles Darwin proposed a mechanism for evolution:
NATURAL SELECTION. He probably developed this theory in
the late 1830s, but did not publish it for 20 years.

• Historians of science have claimed that the delay was due
to Darwin being nervous about hostile reactions, but his
letters and other writings do not suggest this.

• The real reasons are probably that he wanted to amass as
much evidence for natural selection as he could before
publishing, and also that Darwin was very busy with other
work!

• It was a letter from Alfred Wallace, suggesting a similar
theory, that finally stimulated Darwin to make public
his ideas.
• Darwin and Wallace presented their papers jointly to a
learned society in London in July 1858, and in the
following year he published his great work, THE ORIGIN
OF SPECIES.
• Much of it, is concerned with evidence for evolution by
natural selection: These are the main types of
evidence:
1) Breeding of domesticated animals and crop plants
2) Fossils
3) Homologus structures
4) Geographical distribution of animals and plants.

Darwin’s caricature from Punch’s
Almanack- 1882

2.4.1.- Evidence for evolution
• 1) DOMESTICATED ANIMALS
Humans have deliberatly bred and used particular animal
species for thousands of years. If modern breed of
livestock are compared with the wild species that they
most resemble, the differences are often huge.
Consider the differences between modern egg-laying
hens and the jungle fowl of Southern Asia, or between
Belgian Blue cattle and aurochs of Western Asia. There
are also many different breeds of sheep, cattle and
other domesticated livestock, with much variation
between breeds.

• It is clear that domesticated breeds have not always
existed in their current form. The only credible
explanation is that the change has been achieved
simply by repeadly selecting for breeding the
individuals most suited to human uses. This process is
called artificial selection.
• The effectiveness of artificial selection is shown by the
considerable changes that have occured in
domesticated animals over periods of time that are
very short, in comparison to geological time. It shows
that selection can cause evolution, but it does not
prove that evolution of species has actually occured
naturally, or that the mechanism for evolution is
natural selecion.

2) FOSSIL RECORD:

In the first half of the 19th century, the sequence in which
layers or strata of rock were deposited was worked out
and the geological eras were named. It became
obvious that the fossils found in the various layers were
different; there was a sequence of fossils. In the 20th
century, reliable methods of radiosotope dating
revelaed that ages os the rock strata an of the fossils in
them. There has been a huge amount of research into
fossils, which is the branch of science called
paleontology. It has given us the strong evidence that
evolution has occured.

Fossil evidence:
The sequence in which fossils appear matches
the sequence in which they would be
expected to evolve:
- Bacteria and simple algae appearing first
- Fungi and worms later
- Vertebrates then: fish  amphibians 
reptiles birds  mammals.

3) Homologus structures
Darwin pointed out in the Origin of the species that some
similarities between organisms are superficial.
Similarities like those between the tail fins of whales and
fishes are known as analogus structures. When we
study them closely we find that these structures are
very different. An evolutionary interpretation is that
they have had different origins and have become
similar because they perform the same or similar
function. This is called CONVERGENT EVOLUTION.

Homologus structures are the converse of this. They
are structures that may look superficially
different and perfomr a different function, but
they have a “unity type”. These limbs, include the
same bones, in the same relative positions,
despite on the surface appearing completely
different.
The evolutionary explanation is that they have had
the same origin, from an ancestor that had a
pentadactyl or 5 digit limb, and that they have
become different because they perform different
functions. This is called adaptive radiation.

There are many examples of homologus structures. They
do not prove that organisms have evolved or had a
common ancestry and do not reveal anything about
the mechanism of evolution; But they are difficult to
explain without evolution.
Particulary interesting are the structures that serve no
function. They are called VESTIGIAL ORGANS, and
examples of thme are the beginning of teeth found in
embryo baleen whales; despite adults being toothless.
Another example is the appendix in human being.
These structures are easily explained by evolution as
structures that have lost their function and so are
being gradually lost.

NATURAL SELECTION
• Darwin developed his understanding of
evolution over many years after returning to
Englad from his voyage around the world.
• He probably developed the theory of natural
selection in 20 or 30 years.
• Observations and deductions of this theory:

Observation  Deduction
1)Populations tend to reproduce rapidly and if
every individual survived, there would be a
geometrical or exponential increase in the
population. On the other hand, when natural
populations are studied, they tend to remain
stable. There are natural checks to increases in
population, for example, food supplies for
animals. There is a limit to the size of population
of a species that the environment can support 
THERE IR A STRUGGLE FOR EXISTANCE, IN
WHICH SOME INDIVIDUALS SURVIVE AND SOME
DIE.

2) Organisms vary- there are differences between
individual organisms even if they are members of
the same species. These differences affect how
well suited of fiited and organism is to its
environment and model of existence. This is
called adaptation. Some individuals are better
adapted that others because they have the
favourable variations.  IN STRUGGLE FOR
EXISTENCE, THE LESS-WELL ADAPTED
INDIVIDUALS WILL TEND TO DIE AND THE BETTER
ADAPTED WILL TEND TO SURVIVE. THIS IS
NATURAL SELECTION.

3) Much of the variation between individuals can be
passed on to offspring: it his heritable 
BECAUSE THE BETTER- ADAPTED
INDIVIDUALS SURVVE, THEY CAN
REPRODUCE AND PASS ON THEIR
CHARACTERISTICS TO THEIR OFFSPRING. THE
GREATER SURVIVAL AND REPRODUCTIVE
SUCCES OF THESE INDIVIDUALS LEADS TO
AND INCREASE IN THE PROPORTION OF
INDIVIDUALS IN THE POPULATION THAT
HAVE THE FAVOURABLE VARIATIONS.

Linked concepts in Darwin’s theory of
evolution
1.- Population growth
2.- Resource limitation
3.- A struggle for existence
4.- Variation
5.- Adaptation
6.- Differential reproduction
7.- Natural selection
8.- Descent with modification
9.- Origin of species
10.- Extinction of species.

GALAPAGOS FINCHES- Evolution in
action

• Darwin visited the Galápagos Islands in 1835 and
collected specimens of small birds, which were
subsequently identified as finches. There are 14
species in all. Darwin observed that the sizes and
shapes of the beaks of the finches varied, as did
their diet.
• From the overall similarities between birds and
their distribution over the Galàpagos islands,
Darwin hypothesized that “ one might really
fancy that from an original paucity of birds in this
archipielago, one species had been taken and
modified for different ends”

• Characters and diet are closely related and
when one changes, the other does also.
• Variation in the shape and size of the beaks is
mostly due to genes, though the environment
has some effect.
P=G+E
The proportion on the variation due to genes is
called the heritability

Antibiotic resistance
Evolution in action
• After an antibiotic is introduced and used on
patients, bacteria showing resistance appear
within a few years.
• Resistance to the antibiotic spreads to more and
more species of pathogenic bacteria.
• In each species the proportion of infections that
are caused by a resistant strain increases
• Strains of bacteri appear that are resistant to
more and more different antibiotics; this is called
MULTIPLE RESISTANCE.

• There has been very widespread use of
antibiotics, both for treating diseases and in
animal feeds used in farms.
• Bacteria can reproduce very rapidly, with a
generation time of less than an hour.
• Populations of bacteria are often huge, increasing
the chance of a gene for antibiotic resistance
being formed by mutation.
• Bacteria can pass genes on to other bacteria in
several ways, including useing plasmids, which
allow one species of bacteria to gain antibiotic
resistance genes from another species.

2.5.- CLASSIFICATION
• It is natural for humans to recognize the features of living organisms
and to use these features to put organisms into groups. At a basic
level, simple observation shows that there are often many
organisms of the same type.
• If we agree on a name for a groups of organisms, we can the talk
about them.
• Naming organisms is called NOMENCLATURE.
• The idea of a group of organisms of the same type has developed
into the biological concept of the species.
• In every language, names have been chosen for species, but science
is an international venture and so names are needed to be
understood throughout the world.

Biological system
The system that biologists use is called
BINOMIAL NOMENCLATURE  scientific name
of 2 words: Linnaea borealis.

1) First name: Genus name  Genus is a group
of species that share the same
characteristics.
2) Second name: Species or specific name

Binomial Nomenclature’s Rules:
1) The genus name begins with an upper-case
(capital) letter and the species name with a
lower-case (small) letter.
2) In typed or printed text, a binomial is shown in
italics.
3) After a binomial has been used once in a piece
of text, it can be abbreviated to the initial letter
of the genus name with the full species name.
Ex: L. borealis.
4) The earliest published name for a species, from
1753 onwards, is the correct one.

2.5.1.- The hierarchy of taxa
Taxon: things that are arranged into a group
Taxa: Plurarl of taxon
1) KINGDOM: Animalia
2) PHYLUM: Chordata
3) CLASS: Mammalia
4) ORDER: Carnivora
5) FAMILY: Canidae
6) GENUS: Canis
7) SPECIES: lupus

Canis lupus.

Dichotomus keys: How to classify
organisms

Kingdom: Plantae
Characteristics:Photosynthetic, Chlorophyll, Cellulose, cell wall, Vacuoles
permanent,Store starch

5. Ecology and evolution

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5. Ecology and evolution