UNIT 2 NOTES
ABIOTIC AND BIOTIC FACTORS OF THE ENVIRONMENT
I.
Abiotic and Biotic
 Abiotic factors of the environment are nonliving factors, such as temperature,
precipitation, rock bed, salinity, sunlight etc.
 Biotic factors of the environment are living factors, such as predators, food sources,
interspecific and intraspecific competition, parasite, disease causing agents
II.
Climate
 Climate – the long-term prevailing weather conditions in a particular area, we are
talking about long time periods
 Weather – includes temperature, precipitation, cloud conditions, light conditions at a
given time
 Climate is determined by a wide range of factors:
i. Sun light and heat that it generates
ii. Atmosphere composition
iii. Surface conditions
iv. Pressure
v. Wind
 Because the Earth is a sphere, regions around the equator receive sunlight at a 90°
angle, while the areas on the South and North receive the light at a lower angle. This
lower angle reduces the energy that reaches these locations
 Seasons are due to the tilted angle of the Earth’s rotational axis around the sun.
 Ocean currents and wind patterns also influence temperature and precipitation all
around the world.
 Climate is also affected by topography. As moisture filled air moves up on high
mountains, it cools down and forms droplets of water that fall as rain. However, as the
air moves down the mountain, it does not bring any more moisture. So the downwind
side of mountains is dry.
Climate and Human Influence
 Climate change is any change in global temperature and precipitation patterns. Earth
naturally has fluctuations in these patterns over very long time periods, hundreds of
thousands to millions of years.
 Anthropogenic climate change – alterations in long-term atmospheric conditions cause
by human activity. Evidence suggests that today’s climate change is so fast, it cannot be
caused by natural conditions alone. It is mostly due to human activities.
 Greenhouse gases play a major role in determining the earth’s climate. These are
compounds in the atmosphere that absorb heat that radiates from the earth’s surface
and reradiate it back to the surface – greenhouse effect
III.
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Greenhouse gases include water vapor, CO2, CH4, NO, and some other products like
chlorofluorocarbons. Human activities, such as burning fossil fuels, industrial activities
and agriculture increased the concentration of these gases in the atmosphere. Figure 4
and Figure 5 in Module 178.
Bioskill – Interpreting Graphical Data of Atmospheric CO2 Concentrations – Figures 6, 7
and 8 in Module 178
Consequences of the climate change:
i. Glaciers and sea ice shrink
ii. Snow and sea ice melts earlier each year
iii. Decreased reflection of the white snow and ice cover decreases solar radiation
which increases temperature even more – positive feedback mechanism –
accelerating mechanism in which the consequences push a mechanisms to go
even faster
iv. Increased surface temperatures
v. Changes in weather patterns and precipitation
vi. Permafrost melts and releases more greenhouse gases – yet another positive
feedback
vii. Increased precipitation may increase erosion in some areas
Figure 9 – Module 178
IV.
Terrestrial Biomes
 Biome – a large geographical area that contains a unique collection of naturally
occurring animals and plants. Biomes are categorized as aquatic and land biomes.
You need to understand how climate and other factors influence biomes and how their
biodiversity can be useful for us.
Figure 2 – Module 179
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Main environmental factors that determine the nature of a biome are average yearly
temperature (°C) and the annual precipitation (cm). These are the most important
abiotic factors of terrestrial biomes.
Forest biomes usually require substantially more yearly precipitation than grassland
biomes.
Higher annual temperatures with lower precipitation can lead to deserts, while very low
temperatures result in tundras.
Climatographs are used to show the temperature and precipitation in a given are broken
down by month.
Major human activities such as deforestation, overwatering and habitat destruction
endangers terrestrial biomes.
Figure 6 – Module 179
V.
Aquatic Biomes
 Aquatic biomes are divided into two major types: freshwater and marine biomes.
 They make up about 3/4th of the earth’s surface.
 They are interconnected with the terrestrial biomes because of the water cycle.
 Most important abiotic factors in aquatic biomes:
o Salinity – salt content (fresh water, brackish water, salt water, brine)
o Nutrient content (oligotrophic water, eutrophic water)
o Light intensity (photic and aphotic zones)
o Temperature stratification (thermocline)
o Bottom surface (benthic zone)
Figure 4 – Module 176 as an introduction to the case study.
As a conclusion of the case study:
Many abiotic factors can interact to cause various changes in the environment. For example, oxygen
concentration can be depleted in aquatic biomes by warming water, increased number of decomposers
that use up the oxygen, increased salinity, less turbulence and too high nutrient concentration.
Eutrophication – a dangerous condition in both fresh water and marine biomes. Because of increased
nutrient wash off from farms and possibly sewage from cities, aquatic biomes become eutrophic. Algae
and bacteria can reproduce at a higher pace by using the nutrients from the wash off. The
consequences:
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Higher number of heterotroph bacteria use up the oxygen in the water
Algae and bacteria cover the surface of the water so photosynthetic organisms in the
water don’t get sunlight and die
Toxins are produced by certain algae and bacteria that can harm other living organisms
in the water
Higher number of dead organisms increase the number of decomposing organisms and
they also use up the oxygen in the water
POPULATIONS
I.
Human Population Growth
 Populations can increase their numbers by the following:
o Increasing birth rate
o Decreasing death rate
o Increasing immigration and/or decreasing emigration
II.
Estimating Populations:
 Population ecology studies the number, composition, growth rate, dispersion and
environmental factors of populations.
 Populations: all living organisms that belong to the same species and live in the same
area.
 The number of organisms in a population can be estimated or calculated by using:
o Density – number of organisms per unit area or per volume. Fairly constant
density over time is an indication of a healthy population.
o Dispersion – The changes of density of a population across its range. Can be
clumped (herds of grazing animals or schools of fish grouping around a food
source), uniform (creosote bushes in the desert because of the limited water
supply, artificially planted farm trees in an orchard), random (usually for no
particular reason, birds flying in the wind or insects flying, weeds as their seeds
were dispersed)
o Demography – calculations to account for the birth, death rate and immigration
and emigration data. Life tables or survivorship curves are used to describe the
demography of populations. Survivorship curves show how mortality varies
with age of the individuals in a population. Type I survivorship – organisms
rarely die when young, parents take care of their young and organisms tend to
die in large numbers when old. Type II survivorship – organisms have an equal
chance of dying when young or old. Type III survivorship – organisms die in an
early age but the ones that survive, can live for a long time.
Figure 3 and Table 3 in Module 179
III.
Growth of Populations Over Time
 Death, birth, immigration and emigration changes population numbers.
 The number of organisms in a population will be limited by various environmental
factors, such as food, nesting place, water supply etc. The maximum number of
individuals an environment can support over time is called its carrying capacity (K).
 Exponential growth is where the growth rate increases exponentially. This is due to
having plenty of resources available for all new organisms. How many new organisms
are added into the population by each already present organism in a given time period
is called the per capita increase (rmax), this multiplied by the population size (N), gives us
IV.
the population growth or decline over time (G). G = r(max) N (G can also be represented
by dN/dt)
 Logistic growth is when the resources start to limit the growth of the population
because the carrying capacity of the environment is reached by the individuals in the
population. As the population size (N) gets larger, the per capita increase (rmax ) gets
smaller, because fewer offspring are born or can survive. In this case, G=rmax N (K-N/K)
(G can also be represented by dN/dt) In this case, r = rmax (K-N/K)
K and r Selection
 Evolution of populations developed different ways of dealing with the varying carrying
capacity of the environment.
 K selection is a process in which organisms produce fewer offspring, later in their lives
because the environment cannot support many new offspring. These organisms care
for their young.
 r selection is a process in which organisms produce lots of offspring, reproduce fast,
from a young age but do not care for their young. These organisms have a different
strategy to assure reproductive success.
Think back to evolutionary fitness. The goal is to reproduce
V.
Factors that Regulate Population Size
 Once the carrying capacity of the population is reached, various environmental factors
will limit the number of organisms in the population – density-dependent factors affect
the population only at certain densities. Examples of these are food sources, water
sources, nesting place, spread of disease causing agents, etc.
 Density-independent factors impact the population regardless of its density. Examples:
weather conditions, volcanic eruption etc.
 Because these conditions change over time and the carrying capacity of the
environment can change with it, population numbers fluctuate greatly over time.
Figures 9 and 10 Module 178
http://www.pbs.org/wgbh/nova/earth/global-population-growth.html
http://www.youtube.com/watch?v=sc4HxPxNrZ0 – 7 billion
 Due to better healthcare, humans live longer today than ever before in human history.
As a consequence, human population exploded since the nineteenth century.
VI.
Evolution of Life History Strategies
 Each species confronts a trade-off between parental investment and the number of
offspring it produces. Some species may have only a few offspring and takes good care
of them (great investment), while others may have many offspring but invest little
energy into taking care of them. Each strategy has its advantages and drawbacks.
 Most species has a life history strategy that is in between the two extremes.
Complete the case study on Population Dynamics and the concept map.
COMMUNITIES – SPECIES INTERACTIONS
I.
II.
Introduction
 Communities – all living organisms in a given area that interact with each other. This
interaction can be two basic types:
i. Intraspecific interaction – the interacting organisms belong to the same species
ii. Interspecific interaction – the interacting organisms belong to different species
 Ecological Niche – Every species has a determined set of behaviors, resources and
environmental factors that they can tolerate. Fundamental niche describes all limiting
factors and resources that a species can possibly utilize. Realized niche describes all
factors that it does utilize in the presence of biotic interactions with competitors and
predators.
Interspecific Interactions
 There is a wide range of interactions between species. The following list shows the
most common types (+ means beneficial interaction, - means harmful interaction, 0
means neutral or no interaction):
i. Competition (-,-) because it is harmful for both parties, competition limits the
number of individuals in each population and also drives evolutionary fitness
because the organisms of the two parties compete with each other for
resources. (Ex. Plants competing with other plants for sunlight in a forest,
zebras and antelopes compete for grass on the savannah). Figure 2 – Module
185. Competitive exclusion principle states that in a community, where two
species compete for the same limiting factors, they cannot coexist and only one
species will survive. If two species compete with each other for the same
resources, they may be forced to divide up the available resources with each
other – resource partitioning. In this case, evolution may benefit organisms
that have more different traits from the competition.
ii. Predation, herbivory, parasitism (+,-) – feeding relationships, where one
organism benefits by consuming the other organism or its parts. However,
these relationships can also be beneficial for the entire ecosystem, when for
example herbivores are controlled by predators, so plants can survive.
Coevolution of both parties is also very powerful. List some adaptations below
of each party:
Adaptations of
predators
Enhancement
of senses,
agility, sharp
teeth, claws,
strong
muscles, bones
Adaptations of
prey
Forming packs,
playing dead,
warning signals
(behavioral
adaptations),
cryptic
coloration
(camouflage),
warning
coloration,
toxins,
unpleasant
taste,
Mimicry
(Batesian –
harmless
copies
harmful,
Mullerian—
harmful and
harmful look
similar)
Adaptations of
plants
Toxins, thorns,
unpleasant
taste, fast
growth,
Adaptations of
herbivores
Modified
digestive
system, strong
teeth, tough
lips, long legs
and necks to
reach trees,
resistance to
toxins
Adaptations of
parasites
Behavioral –
parasitic
wasps, social
parasitism –
cuckoos,
Structural—
resistance to
stomach acid
and enzymes
by forming
thick outer
covering,
Fast
reproduction
Adaptations of
hosts
Immune
response
against the
parasite, acids
and digestive
enzymes
against
parasites in the
digestive
system
The following relationships are all considered symbiotic relationships – a relationship between two
species that live in intimate contact.
III.
iii. Amensalism (-,0) occurs, when one species inadvertently harms another.
Usually occurs when a metabolic waste is secreted by one organism that is
harmful for another (break mold secretes penicillin, that harms bacteria but
does not directly benefit the bread mold either)
iv. Mutualism (+,+) Sometimes mutualistic relationships are obligate, neither party
can survive without the other, but sometimes facultative, they can survive
without each other but they are both better off with each other. (Termites and
wood digesting protists in their digestive system – obligate, clownfish and sea
anemones – facultative).
v. Commensalism (+/0) Includes organisms that use another one for
transportation (mites sitting on a beetle)
Dominant and Keystone Species
 Dominant species have a disproportionately larger influence on the community because
of their large biomass in that particular community. (Ex. Kelp in kelp forests because
although there are other algae, kelp is the most common there. Dominant grass species
in the savannah.)
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Keystone species – Species that may not have the largest biomass in the community,
but they influence the community food chains or webs more than others. (Ex. Starfish in
coastal areas are influential because they keep mussel numbers under control. Sea
otters in kelp forests are influential because they keep the sea urchin populations under
control that otherwise would destroy the kelp.)
Please review food chains and food webs. We don’t spend any time on it in class.
IV.
Disturbance and Succession
 Disturbance is a discrete event in time that causes stress and mortality or both to at
least some species in the community and results in change in the community. Ex. Fires,
hurricanes, human activities such as clearing a land for farming.
 Ecosystems tend to follow predictable and directional change in species composition
and environmental factors. Immediately after the disturbance, the community is
dominated by species that are rapid colonizers and grow very fast, but are less
successful at competitions for nutrients and light. Later on these species are
outcompeted by slower growing but more dominant species and finally a climax
community is reached – today it is considered the most diverse community that can
potentially exist in a given area.
 Primary succession – occurs on habitats that had been unavailable for life previously, so
they don’t have soil for plants to grow on. These communities start with bacteria,
lichens, mosses.
 Secondary succession – occurs on land that was previously cleared of most species.
Because soil exists on these, weeds, flowering plants that are fast growing can take root
very quickly.
Do Figures 4 and 5 activites
ECOSYSTEMS – ENERGY
I.
II.
Laws of Thermodynamics That Guides Energy Transfer in Ecosystems
 Ecosystem – group of organisms and all of their abiotic surroundings in a given area.
 The first law of thermodynamics – energy can change from one form to another but cannot
be created or destroyed.
 The second law of thermodynamics – energy transfers are never 100% efficient, so some of
the energy is always lost as heat and not usable for living organisms any more. For example,
only 0.1% of energy from the sun that hits the earth is used by autotrophs for
photosynthesis.
 Free energy – a term that we use to describe all available energy sources for living
organisms.
Energy Flow in Ecosystems
 Energy always flows through the ecosystem and does not get recycled back into it.
 Energy enters food chains and webs through photosynthesis by producers. They convert
the light energy of sunlight into chemical energy. This energy is used by all other organisms
in a given area.
 Special graphs called pyramids are used to depict the transfer of energy and matter within a
given food chain. Types of pyramids:
i. Energy pyramid – shows the energy content of each trophic level in an ecosystem.
The unit can vary but usually includes energy and an area component, sometimes
even a time component.
ii. Pyramid of biomass – shows the energy content on each trophic level but in mass
unit, as the energy content of organic matter.
iii. Pyramid of numbers – shows the number of organisms on each trophic level. Less
informative from the energy standpoint, because a large tree can support several
different primary consumers.
Figure 3 activity in Module 190
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The first two pyramids clearly show major losses of energy and biomass on each trophic
level. The reason for this is the second law of thermodynamics. The energy is lost as heat
during the various chemical reactions on each trophic level to build the actual organism and
perform its life processes. Very little energy is actually passed from one trophic level to the
next. Some of the energy that is lost as waste matter can be used by decomposers but lots
of it is lost as heat and cellular respiration.
Figure 4 – Module 190
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III.
The flow of energy can also vary depending on various limiting factors. See later
Invasive Species and Their Influence On Energy Flow
 Invasive species – species that are moved into new ecosystems usually by humans,
intentionally or unintentionally. Most of these species die out because they are not adapted
to live in the new environment. However, some become so successful that they threaten
the native species because they don’t have natural predators/herbivores or competition in
the new ecosystem. Examples: kudzu, Asian carp, Burmese python etc.
 Invasive species can shift the energy flow in the new ecosystem, because they pass less
energy up on the trophic levels. They usually don’t have natural predators or herbivores, so
they can spread and only decomposers can get the energy from them.
IV.
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Limits of Primary Production
Ultimately the base of an energy pyramid determines the available energy source for all
organisms in a given ecosystem. Photosynthesis is the main process that takes in the energy.
Primary production – the mass or energy of biomass that is produced by the producers in a
given area at a given time period.
o Gross primary production (GPP) – refers to the total mass or energy of biomass that
plants produce by photosynthesis
o Net primary production (NPP) – refers to the mass or energy of biomass that is
available for the next trophic level after cellular respiration.
NPP = GPP – CR
Measuring Biomass Using Satellite Imagery Figure 6, Module 190
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Some nutrients such as nitrogen and phosphorous limits primary production because they tend
to run out of the soil the fastest. Farmers use fertilizers to replace these nutrients if they are
depleted in the soil.
However, fertilizers can wash into lakes and rivers and make them eutrophic – eutrophication.
Review notes on Gulf of Mexico Case Study
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V.
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Primary production in terrestrial ecosystems is also increased with increasing temperature and
precipitation. – Explain why.
Energy Transfer Among Trophic Levels
Consumers already take in substantially less energy than plants produce by gross primary
production. Than on each consumer level, substantial energy is lost for cellular respiration and
as waste.
Figures 11 and 12 – Module 190
Production efficiency – the efficiency with which a consumer creates biomass using the energy
from its food
Trophic efficiency – a measure of the percentage of production at any trophic level compared to
the production at lower trophic levels. Basically this is the mass or energy of biomass that is
passed on from one trophic level to the next.
ECOSYSTEMS – MATTER
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Cycling of Materials:
While energy flows through the ecosystem, matter always gets recycled back into it. When
complex organic molecules are broken down by decomposers, the atoms of those molecules
are released back into the environment than can be used again by producers.
The Law of Conservation of Mass – states that matter cannot be created or destroyed only
changed into new forms.
The earth is basically considered a closed system when it comes to matter recycling. Some
matter escapes the atmosphere and some matter comes to the earth by meteors, but for
the most part the matter is the same as it has been for millions of years.
Biogeochemical cycles are changes in the form of elements. Bio refers to the appearance in
living organisms or organic matter, geo refers to the appearance of matter in rocks and
minerals, chemical refers to the appearance of matter in other chemical forms.
The Water Cycle
All chemical reactions in living organisms take place in aqueous solutions so all living organisms
need water.
Most of the water on the planet is salt water and only usable for marine organisms. The fresh
water can also be unavailable, because it is in frozen forms in arctic ice or glaciers.
Main storage areas that are available for living organisms are: water vapor in the atmosphere,
lakes, rivers and ground water trapped underground.
All living organisms are able to take in water once it falls as precipitation from the atmosphere.
The excess water can run off of surfaces, evaporate back into the atmosphere or is stores in
aquifers.
The Carbon Cycle
Every organic compound contains carbon, so the carbon cycle is required to build all of our
molecules.
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Main reservoirs of carbon are CO2 in the atmosphere, in rocks as CO32- ions, in the oceans as
dissolved CO2, in fossil fuel reserves as unavailable sources until we burn those and turn them
into CO2 again.
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Producers such as algae, plants and some bacteria are able to trap CO2 from the atmosphere or
from the ocean by photosynthesis and convert it to organic matter during assimilation. Once
the organic matter is formed, carbon can move up in the trophic levels to the consumers and
decomposers. Producers, consumers and decomposers all return carbon to CO2 during cellular
respiration. The rest of the organic matter is broken down by decomposers and also returned to
CO2.
Carbon reserves in rocks are only available after weathering of rocks so they can be trapped for
a long period of time.
Organic matter that did not decompose can turn into fossils by fossilization or to fossil fuels over
a long period of time. However, once fossil fuels are burned, they are released again into the
atmosphere as CO2.
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VI.
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The Nitrogen Cycle
Nitrogen is required for all living organisms to build their proteins and nucleic acids.
Major reservoir of nitrogen is in the atmosphere where it is found as N2 78% of the atmosphere.
However, N2 is very hard to break down because of its triple bond.
Nitrogen fixation – N2 is converted into NH4+ by nitrogen fixing bacteria. Some of these bacteria
live in the soil, others live in the root nodules of legume plants (such as beans, peas and lentils).
Once it is in ammonium form, nitrogen is available for other bacteria to use it.
Nitrification – is a process that converts NH4+ to NO2- or NO3- (nitrite and nitrate) done by
nitrifying bacteria that mostly live in the soil.
Assimilation – Once the nitrogen is in a water soluble nitrite and nitrate form, plants and other
autotrophs are able to take it in and convert it to organic matter such as proteins and nucleic
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VII.
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acids. Some plants are also able to take in ammonia and assimilate that into their organic
matter. This conversion process is called assimilation.
Animals take in organic matter from plants and build their proteins and nucleic acids.
Decomposition(ammonification) – breaks down proteins, nucleic acids and their monomers into
ammonium (NH4+) and returns it into the soil. Decomposers also include many bacteria, fungi
and some other organisms.
Denitrification – converts nitrates (NO3-) to nitrogen gas (N2). This process is done by
denitrifying bacteria. These bacteria generally live under anaerobic conditions in water, like
swamps.
The Phosphorous Cycle
Main reservoir of phosphorous is in the lithosphere, in the form of phosphate in rocks.
Weathering of rocks and erosion release these phosphates into water soluble forms. Mining
and fertilizers containing phosphorous are also used.
The water soluble form of phosphorous can be taken in by plants and used to synthesize organic
matter such as nucleic acids, nucleotides (like ATP, NAD, NADP, FAD etc.) and phospholipids.
Dead organisms and waste than decomposed by decomposers and the phosphorous is released
back into the soil. However, water soluble phosphate usually washes out of the soil into lakes,
rivers etc. and is used in aquatic ecosystems. Dead organisms can also settle on the bottom of
rivers, lakes and can became compacted to form new rocks.
The release of phosphorous again can take for a long time, so this cycle is a lot slower than the
others.
Both nitrogen and phosphorous runoff into waterways contribute to eutrophication – here we go again.
Role of decomposition in the biogeochemical cycles – figures 15 and 16.
THE BIODIVERSITY ISSUES
I.
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II.
How Did Humans Alter the Biogeochemical Cycles?
Alteration of the carbon cycle by humans
o consumption or deforestation of plants decreased NPP on terrestrial biomes by
about 40%
o burning fossil fuels increased CO2 concentrations in the atmosphere – global climate
change
o increased CO2 concentration in the oceans decreases the pH of ocean water
Alteration of the nitrogen cycle by humans
o Increased available nitrogen changed soil chemistry that reduced biodiversity
o Cultural eutrophication
Alteration of the atmospheric oxygen-ozone cycle
o The protective ozone layer is depleted by human made chemicals like CFC’s, which
decreases the UV protection of the planet Figure 8 – 192
Toxin release by humans
o Results in biomagnification (bioaccumulation) – the buildup of toxins in the tissues
of organisms, mostly on the higher trophic levels
Habitat degradation
o Habitat destruction is the complete removal of a habitat by human activities
o Habitat degradation is the decrease of the quality of a habitat due to human
activities, such as pollution, overfishing, selective deforestation, fragmenting the
habitat etc.
BIODIVERSITY ISSUES
In groups of 3-4 you will use various sources to discuss and answer the following questions:
1. What is biodiversity? Besides the definition, find out how many different species of organisms
we estimate lives on the planet today.
2. Explain why biodiversity is important for (use specific examples)
a. Ecosystem stability
b. For humans
c. For planetary concerns
3. What is extinction? Name some major reasons for extinctions of specific species. Describe the
consequences of one specific extinction event.
4. Describe three government actions, organizations or laws that helped to slow the extinction rate
on the planet.
ANIMAL BEHAVIOR
I.
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II.
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III.
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Behavior As An Adaptation For Survival
Behavior – actions to address particular stimuli for their survival and reproduction
Behaviors can influence a species’ response to external environmental stimuli to obtain
food, avoid predators, find mates, raise the young etc. These behaviors influence the
evolutionary fitness of organisms.
Fixed action patterns – an innate response that directly results from the detection of a sign
stimulus. This type of response does not require any previous experience to learn and once
the specific action is triggered, it will be completed even if the sign stimulus disappears. (Ex.
Gulls roll their eggs back to the nest, gulls also regurgitate food when a red dot on their
beaks is pecked by chicks, sticklebacks attack any red-colored object or organism that enters
their territory etc.)
Learned behaviors -- Many types of behaviors are very complex and are triggered by a
combination of environmental factors and ingrained signals not just one single sign stimulus.
(Ex. Migration of birds, butterflies, salmon etc.)
Simple Behaviors
Taxes – simple movements that involve orientation and moving toward (+) or away (-) from
a certain stimulus.
Kinesis – random movement of an animal in which the rate of movement is related to the
intensity of the stimulus but not its direction.
See given handout for examples.
Forms of Communication of Animals
Communication, the transmission of information between animals of the same species is
essential to their survival and reproductive success. Effective communication relies on
being correctly understood so the messages are often highly ritualized so they are not easily
misinterpreted.
Types of communication among animals:
o Tactile messages – touching one animal by the other, like grooming behaviors of
primates, vibrations of the female spider web by male spiders
o Olfactory messages – Special scents are produced by some animals called
pheromones to warn competitors, advertise potential mates, mark territories (ex.
Dogs mark their territories, ants use pheromones to guide colony members etc.)
o Auditory messages – using sound signals to communicate danger, potential mates,
territories etc. (common among birds, chickadees, roosters, crows etc.)
o Visual communication – Brightly colored animals are usually avoided by others –
warning signals; animals also use visual clues to deceive others – eye spots on
moths; some animals have visual cues that are used to attract the other gender –
peacocks, lions etc.
o
IV.
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Complex forms of communication may combine many different types of
communication. Ex. Honey bees communicate the location of food sources to the
other workers in the colony by touching, waggle dancing and showing the direction
and the distance of food.
o Social animals, especially the ones that live in colonies or packs have usually a more
complex communication system.
Migration
Migration is an important response to environmental changes such as change in
temperature and day length. During true migrations, animals travel from one well-defined
region to another for a specific purpose, such as overwintering, breeding, seeking food.
These migrations can take place to very large distances.
Most migrating animals have internal clocks that are in coordination with environmental
changes. The timing of migration is very important, because of the great distances that
animals have to take when migrating.
If organisms get replaced because of lack of food but do not periodically migrate, these are
called dispersals.
Migratory organisms have complex navigation systems that frequently depend on using
built in compasses, such as sun compass, magnetic compass, star compass.
For examples and more details, see given handouts.