Introduction to Ecology
eg. temperature
as far as we know; only earth harbors life
! range over ~100º in most places, in universe can vary
over millions of degrees
one of the most basic characteristics of life is that
living organisms are constantly interacting with
their environment and with each other
eg. atmospheric pressure
!changes due to weather are only a small % of this
eg.
can’t study the diversity of life on earth without
knowing something about a few ecological
principles that affect them
gravitational force
!the same over the entire biosphere
eg. chemical composition of atmosphere
even on earth, life is contained within a thin veneer
near the earth’s surface = Biosphere
! main variable is water vapor which varies only 0 to 4%
(4% = 100% relative humidity)
Biosphere:
eg. chemical composition of open ocean
=the total living world and all aspects of the
nonliving environment with which life directly
interact
! salinity fairly constant 33-35 ppt, similar proportions of
salts throughout the ocean
these general conditions have molded life
along similar patterns & designs
from ~ 7 miles (11,000M) below the surface of ocean
to ~ 6 miles (9,000M) above sea level
within the limits set by conditions in the biosphere all
organisms have certain essentialrequirements for
life
eg. if earth were the size of an apple the biosphere would
be the thickness of its skin
all life evolved on earth and as such all life is
subjected to a similar range of conditions
in general, simpler organisms (bacteria, fungi) are much more
tolerant of extremes in these conditions than larger, more
complex organisms (plants, animals)
environmental characteristics of the biosphere remain
fairly constant over the surface of the earth and
over time
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Ecology: 1409 Introduction to Ecology, Ziser, Lecture Notes, 2013.10
! there can be no metabolism
eg. tundra, boreal forests have very short growing seasons
Some of the most basic
requirements for life
freezing also kills because sharp ice crystals expand
and break the cells open
1. Liquid Water
some organisms are able to survive below freezing
as long as they can keep some of the water
liquid
all life is made mostly of water
eg. humans 60-70 %
water is kept liquid by
life requires liquid water
! high salts (eg. making ice cream or salt
melting snow ! keeps water liquid below
freezing temperatures)
life is basically a series of chemical reactions
=metabolism
eg. there are a few brackish pools in Anarctica
where water remains fluid at –5º F (-20.6º C )
and you cant have chemical reactions unless the
chemicals are dissolved in liquid
! “antifreeze” compounds like glycerol (car
antifreeze) or other alcohols
!no water ! no metabolism
eg. numerous insects survive freezing in tundra by
producing glycerol in their cells
eg. seeds, cysts, etc
eg. some animals can temporarily stop metabolism
eg. human, after 7 hrs exposure to freezing temperatures
whose body temp fell to 77ºF, were revived; such
survivors were often drunk
eg. tardigrades, nematodes
the vast majority of life, especially more complex
organisms, occurs between 68-104ºF (20º-40ºC)
above boiling point (212º F
frozen water is the same as no water at all
Ecology: 1409 Introduction to Ecology, Ziser, Lecture Notes, 2013.10
eg. some bacteria have been kept alive and active in
cultures of water & glycerol down to -4º F (–20º C)
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Ecology: 1409 Introduction to Ecology, Ziser, Lecture Notes, 2013.10
(100º C))water
boils away
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but a high water pressure can prevent water from
boiling
what chemicals an organism is made of is roughly
equivalent to the kinds of nutrients the
organism will need
eg. hydrothermal vents
any chemical that an organism “needs” (cant make
itself) is an essential nutrient
but even temperatures below boiling can be
dangerous
these chemicals can be individual elements
some of the large, complex organic molecules
(eg. proteins and DNA) are very sensitive to
higher temperatures:
individual elements: eg. iron, copper, zinc, carbon
or whole molecules (inorganic or organic)
!above ~ 120ºF (50º C) proteins are destroyed and
cell membranes begin to break down
organic molecules = large molecules containing
lots of carbon atoms; eg proteins, sugars
!DNA melts above 150ºF (65-75º C)
inorganic molecules = small molecules with few
or no carbon atoms; eg O2, H2O, CO2
simpler organisms (eg. bacteria) usually have
wider tolerance ranges for temperature
and other environmental factors
molecules: eg. water, oxygen gas, amino acids, vitamins
!less complex structure, can mutate
and adapt more quickly
at least 25 essential nutrients are universally
required for all life forms
2. Nutrients
but the actual number varies with different
organisms
all life is essentially a collection of chemicals that
react and interact with each other
eg. humans require 45-50 specific individual nutrients
all organisms must be able to take in nutrients to
synthesize the proteins, sugars, starches, fats and
nucleic acids they need to survive, repair their
cells & reproduce
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Ecology: 1409 Introduction to Ecology, Ziser, Lecture Notes, 2013.10
this process of releasing energy from organic molecules is called
Respiration
eg. plants & animals also require O2, many bacteria do not
eg. animals usually require certain small organic molecules such
as vitamins and certain amino acids
some organisms (eg. us) get these organic molecules
from the foods they eat (eg. sugars, starches,
proteins and fats) and then break them down for
energy
some nutrients are easier to get in some environments than in others
eg. rich soils have an abundance of nitrogen and phosphorus for
plants to grow
! heterotrophs
but Austin soils have very little of these nutrients so
growing non-native plants here requires fertilizers
other organisms can use energy from the sun to
make these organic food molecules
3. An Energy Source
a process called photosynthesis
all life requires a continuous input of energy to
preserve its basic structure
sunlight
the basic “work” of the cell = metabolism
CO2 + H20
sugars
then these sugars can be broken
down later as needed for energy
metabolism requires lots of energy
the energy that drives cell activities in all living
organisms comes from the breakdown of sugar
or other “organic” molecules
organisms that are able to use solar energy to
make organic molecules
! autotrophs
when a cell needs energy it will break down these organic
molecules into smaller, simpler inorganic molecules
4. Salt /Water Concentration of ~3%
CO2 + H20
the relative concentration of salt in water is referred to
as its salinity
ENERGY is released
Ecology: 1409 Introduction to Ecology, Ziser, Lecture Notes, 2013.10
H,C,O,N, P, Ca ! comprise 99% of most living
organisms
as chemical bonds are broken, energy is released for the cell’s
activities
Most animals also require some essential molecules
sugar
of all elements required for life, the bulk of all
living matter consists of only 6 elements:
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ocean water has a salinity of 3%
5. Pressure Range Near 1 atm
the cells of most organisms living in the ocean also
contain about 3% salt
~ air pressure at sea level
the main effects of lower pressures is the amount
of O2 available to air breathing organisms
!too little salts causes imbalances within a cell and it can no
longer function properly
!too much salt destroys proteins and causes dehydration
! too little pressure ! not enough O2
eg humans water intoxication, dehydration
the lowest pressure humans can survive is about 1/5th of an
atmosphere ! would become starved for oxygen
in environments with too little or too much salt
organisms will die without special adaptations
eg. few animals are able to live above 22,000 ft elevation
the main effect of higher pressures is felt on gasses
trapped in lungs and air sacs of animals
microorganisms (mainly bacteria) can withstand wide
variations in salt concentrations where they live
eg 0.3% to 33% salt
! too much pressure pushes extra gasses into blood
nitrogen narcosis
more complex organisms require much narrower ranges
! too quick of a return to lower pressures produces gas
bubbles in blood
eg. marine animals generally can’t tolerate
freshwaters and freshwater animals generally
cannot tolerate ocean water
but deep diving mammals can collapse their lungs to prevent
these problems
very few organisms can live in high salt concentrations
6. pH Range near Neutral
eg. the great salt lake, the dead sea
pH is a measure of the balance between acids and
bases
salts are abundant in the ocean but organisms that
live in freshwaters and on land often have trouble
getting enough salt
examples of acids: lemon juice, carbonated drinks, coffee,
battery acid, etc
eg. large land animals such as deer tend to congregate at
“salt licks”
examples of bases: bleach, drain cleaner, oven cleaner
cement,
hunters put out salt to attract deer
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a pH of 7 is neutral
other terms for ecosystems: biomes, ecoregions,
life zones
!above 7 means more bases, fewer acids
different ecosystems are usually easily recognizable
!below 7 means more acids, fewer bases
fluid inside most living cells is near neutral
eg. rainforest, desert, tundra, etc
like salts, too much or too little acidity can affect large
organic molecules
the study of these distinctive patterns throughout the
biosphere is called “ecology”
ecology: the study of organisms’ interactions with
their environment & with each other
eg. destroys proteins
eg. humans body fluids pH=7.4; <7.0 and >7.8 ! death
General Kinds of Ecosystems
but some bacteria can live in pH of 1 to 13
more complex organisms are more restricted in pH tolerance
all the world’s ecosystems can be grouped into just a
two broad categories that share many similar
characteristics that life in them must adapt to:
animals can rarely grow in environments above pH of 10.5
acid rain in northern lakes kills fish and aquatic
fauna; kills trees in northern forests
A. Aquatic Ecosystems
Ecosystems
(~73% earth’s surface)
B. Terrestrial Ecosystems
variations in the above factors (and others),
throughout the biosphere produce distinctive
sets of environmental conditions and results in
distinctive living communities
(27% earth’s surface)
A. Aquatic Ecosystems
water based
most stable overall (most of ocean is 2º C)
ie, ecosystems
buoyancy of water reduces need for support
an ecosystem is a portion of the biosphere with
similar environmental conditions supporting a
characteristic and distinctive group of species
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Ecology: 1409 Introduction to Ecology, Ziser, Lecture Notes, 2013.10
less oxygen in water than in air
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!larger animals need more efficient extraction
Freshwater Ecosystems
eg. streams, rivers, lakes, ponds
eg. gills
(<2% earth’s surface = less than the area of Europe)
heavy dependence on chemical senses and ability to
detect vibrations in water
more variable in temperature, amount of light,
nutrients, etc than marine
water is an ideal medium for reproduction
spawning
motile larvae for dispersal
doesn’t require internal fertilization
very few salts in water
FW systems are disproportionately rich in species and
disproportionately imperiled
two different kinds of aquatic ecosystems:
1. Marine
2. Freshwater
FW ecosystems encompass <2% of earth’s surface
!they contain 12% of all animal species
Marine Ecosystems
! including 41% of all fish species
eg. oceans, seas, bays, estuaries, intertidal shores,
deep trenches
but a much greater proportion of fw species are now
endangered, threatened or at risk
oceans dominate the biosphere:
eg.
eg.
eg.
eg.
71% of area of earth; 99% of volume of biosphere
salt concentration roughly the same as most cells
[compare to terrestrial:eg. 17% of mammals; 11% of birds
are at risk]
! no need for salt/water regulation
B. Terrestrial Ecosystems
most of the ocean gets NO light from the sun
(~27% earth’s surface)
eg. forests, marshes, deserts, rainforests, savannahs, praries,
etc
algae, seaweeds, and blue green bacteria
are only found in the upper layers
Ecology: 1409 Introduction to Ecology, Ziser, Lecture Notes, 2013.10
20-36% of all fw fish species
67% fw clams
64% crayfish species
35% amphibians
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Ecology: 1409 Introduction to Ecology, Ziser, Lecture Notes, 2013.10
harshest, most variable environment
ocean temperatures are constant
organisms living on land must be resistant to drying
or be able to store water
land has harsh cycles of freezing and drying
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on land reproduction become more complicated
oxygen more freely available
plants and animals must be able to get sperm cells
to egg cells
plants do this by producing producing pollen
that travels by wind or insects to the
female flower
eg. air contains 20x’s more oxygen than water
but respiratory organs must be protected inside
body to avoid drying out
eg. lungs, book lungs, tracheae
animals must find mates
on land organisms need considerably more support
! often more elaborate mating behaviors
than in aquatic animals
water is 800x’s more dense than air
water is harder to move through but does buoy
up the body
Community Interactions
in addition to interactions between the living and
nonliving parts of an ecosystem, there are also
numerous interactions between the living
organisms themselves
the largest animals that ever existed are aquatic animals
land plants need solid tissues (wood) to grow tall and
hold leaves up
land animals need strong skeleton & muscular
system to get around
plants vs herbivores
predators vs prey
land based live must adapt to extreme changes in
temperature throughout the seasons
symbiosis = when two organism are usually found
together and are interdependent on each other
water fluctuates little in temperature
not the same as predator/prey or food chain relationships
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eg. many gut bacteria
is a closer more specific kind of interdependence
c. Parasitism
ALL living organisms including all animals form
symbioses with other animals and other lifeforms
Kinds
a.
b.
c.
most common form of symbiosis
there are parasitic bacteria, protists, fungi,
plants and animals
of Symbioses
mutualism
commensalism
parasitism
eg. 20-50% of all animal species are parasitic
one organism benefits at the other’s expense
a. Mutualism
ie. the other is harmed in some way
both organisms benefit from the relationship
eg. tapeworms, liver flukes, fleas, ticks, etc
biologists estimate that virtually every species
participates in some form of mutualism
eg. symbiotic algae in corals and sponges
eg. protozoa in gut of termite
eg. flowering plants trade nectar for pollination
services
eg. symbiotic bacteria and fungi provide essential N &
P for room & board
b. Commensalism
one organism benefits, the other neither benefits
nor is harmed (neutral effect)
eg. follicle mites
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