Title: Ecology
1Ecology is The study of the distribution and
abundance of organisms, AND the flows of energy
and materials between abiotic and biotic
components of ecosystems.
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7Ecology is an integrative/ interdisciplinary
science -Understanding of the biological
(biotic) and physical (abiotic)
sciences -Provides a context for the reductionist
sciences in biology -Closely tied to genetics and
evolution -Ecology can be studied at different
spatial and temporal scales -Includes the role of
humans in their environment ( global change)
8Factors to consider
- Non living (abiotic) factors such as light,
temperature, salinity, water, oxygen. - Living factors (biotic) such as competition,
predation, symbiosis, disease, mating, camouflage
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10Abiotic Factors
- Light necessary for photosynthesis, affects
distribution and growth of plant and animals.
Adapt to low levels of light. - Temperature affect metabolic rate, most organisms
cannot adapt to extreme temperatures and seasonal
changes (eg. Plant wilt, animals hibernate) - Water necessary for life (metabolism), adquate
supply necessary. Xerophytes (plants) and desert
animals have adaptations to low levels of water.
Hydrophytes are adapted to high water conditions - Oxygen necessary for metabolism, adaptations to
receive oxygen (Pneumatophores in magrove) fishes
have gills and come to the surface.
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12Salinity important for water organisms (high
salt, low salt). Microbes have contractile
vacuole to pump out excess water. Fishes have
adaptations to extreme salinity. pH value is
important, for ponds and streams, the pH value
can change whether plants absorb CO2 or give off
CO2. (more acidic)
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161. Camouflage
- Cryptic coloration
- a. Hides from predators.
- b. Example English Peppered Moth
172. Aposematic
- Bright colors
- a. Advertises noxious trait
- b. Example Monarch Butterfly
183. Mimicry
- Two examples
- 1. Mullerian Mimicry when two unpalatable
species mimic each other in the same habitat. - 2. Batesian Mimicry palatable species mimic
unpalatable species.
19Symbiotic Relationships
- Help structure communities.
- Three examples
- 1. Parasitism
- 2. Commensalism
- 3. Mutualism
201. Parasitism
- Symbiotic relationship which benefits one
organism and harms the other. - Example
- 1. Tick on a coyote
- 2. Tapeworm in a dog
- 3. Flea on a cat
212. Commensalism
- Symbiotic relationship which benefits one
organism while the other is unaffected. - Example
- 1. Cattle egrets and cattle in field
223. Mutualism
- Symbiotic relationship which benefits both
organisms. - Examples
- 1. Acacia ants and acacia tree
- 2. Termites and gut protozoa
- 3. Legumes and nitrogen-fixing bacteria
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25Scales of Ecological Organization
26Scales of Ecological Organization
Organism Survival and reproduction unit of
natural selection
27Individuals
- Important to ecologists who study
- Behavioral ecology
- Feeding patterns of predators feeding optimally
- Symbioses
- Lichens are partnerships between an alga and a
fungus
28Scales of Ecological Organization
Population Population dynamics unit of
evolution demography sex ratios
29Population
- A group of individuals, all belonging to just one
species - A community may have several populations
30Scales of Ecological Organization
Community Interactions among populations specie
s diversity, trophic dynamics competition,
succession
31Community
- All of the living species in an area
- These species may interact
- DOES NOT include abiotic factors
32Scales of Ecological Organization
Ecosystem Energy flux and nutrient cycling,
primary productivity material fluxes
33Ecosystem
- The largest unit of biological organization
- Includes both the biotic (living) and the abiotic
(non-living) factors in an area - Biotic all the plants, animals, bacteria, fungi,
molds - Abiotic temperature, wind, soil nutrients, fire,
flood, rain
34Scales of Ecological Organization
Biosphere Global processes includes biotic and
physical systems oceans, atmosphere, geology
35Biosphere
- Includes all of Earths resources and life forms
- A large variety of habitats
- Important to ecologists who study distribution of
organisms (biogeographers)
36Ecosystem Services
the processes and conditions provided by
ecosystems that are beneficial to humans and
other organisms
the processes and conditions provided by
ecosystems that are beneficial to humans and
other organisms
37Ecosystem
-- a community of animals and plants interacting
with one another and their physical environment
-- includes physical and chemical components such
as soils, water, nutrients that support the
organisms that live within them, ranging from
bacteria to rainforest trees to elephants and
humans too
38Food Chains and Food Webs
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40Food Webs
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42Global Cycles
43Ecosystem Ecology
- Definition All the organisms living in a
community AND the abiotic factors with which they
interact - Scale depends on questions asked
- One, small habitat, up to
- The biosphere
- Energy flow through trophic levels
- Biogeochemical cycling
- Carbon (climate change)
- Inorganic nutrients (eutrophication)
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46Ecosystem Dynamics
54.1
- Energy flows through ecosystems
- ultimately lost as heat
- Matter cycles around ecosystems
- Elements are not lost but cycle through pools
Heterotrphs
Fig. 54.1
47Energy Flow
- 1st Law of Thermodynamics
- Energy is conserved
- Ecosystems
- energy in from outside sources
- passed from trophic level to trophic level
- 2nd Law of Thermodynamics
- Energy transformation is not 100 efficient
- Ultimately all lost as heat
- Trace energy flow
- Outside source to heat
- Compute energy budgets at each transfer
Fig. 54.1
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50Trophic Structure
- The different feeding relationships that
determine the route of energy flow and the
pattern of chemical cycling. - According to the rules of ten, approximately
10 of the potential energy stored in the bonds
of organic molecules at one trophic level fuels
the growth and development of organisms at the
next trophic level.
51Trophic Structure
- Five examples
- 1. Primary Producers
- 2. Primary Consumers
- 3. Secondary Consumers
- 4. Tertiary Consumers
- 5. Decomposers and Detrivores
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55NICHE
In ecology, a niche is a term describing the
relational position of a species or population in
an ecosystem. All living things have their
niches. A niche is the role and position of a
species in nature. Another way of looking at it
is that a niche is basically an organism's "job"
in nature. Two different populations can not
occupy the same niche at the same time, however.
The description of a niche may include
descriptions of the organism's life history,
habitat, and place in the food chain. The full
range of environmental conditions (biological and
physical) under which an organism can exist
describes its fundamental niche. As a result of
pressure from, and interactions with, other
organisms (e.g. superior competitors) species are
usually forced to occupy a niche that is narrower
than this and to which they are mostly highly
adapted. This is termed the realized niche.
56Ecological Adaptations
- 1. Camouflage (Cryptic) 2.
Disruptive Markings 3. Warning
Coloration 3. Mating
Coloration 5. Batesian
Mimicry 6. Automimicry
57 Camouflage Cryptic Concealing form and
coloration which enables a species to avoid its
natural predators by camouflage. Good examples of
this adaptation are the katydid, walking stick
and tomato hornworm. The spittlebug secretes a
foamy mass to conceal itself on a branchlet. An
interesting resident bird of the alpine tundra is
remarkably camouflaged by seasonal coloration.
During the summer months the plumage is a mottled
brownish color. During winter, when the ground is
covered with snow, the plumage is snow white.
Two examples of camouflage in San Diego County A
canyon tree frog (Hyla arenicolor) on
granodiorite canyan wall (left) and a desert
horned lizard (Phrynosoma platyrhinos) on a sandy
riverbed.
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59Disruptive Markings
- Disruptive Markings The markings on some
insects, reptiles and mammals make it difficult
to distinguish them from shadows and branches or
from other members clustered together. The
stripes on a zebra may appear quite distinctive,
but to a colorblind lioness it is difficult to
single out an individual zebra among a dense
population in the African grasslands.
60Warning Colouration
- Insects with an obnoxious quality (at least to
would-be predators), such as bad taste, bad smell
or powerful sting, often exhibit bright colors to
warn of their presence. Warning coloration is
well developed in the insect order Hymenoptera,
including bees and wasps. Small poison dart frogs
of the tropical rain forest also exhibit warning
coloration. These frogs contain very toxic
neurotoxic alkaloids in their skin. Their
coloration (called aposematic coloration) is an
adaptation for diurnal foraging in which
predators can easily recognize and avoid these
posonous amphibians.
61Mating Colouration
Bright colorations among the males of some
animals (particularly the plumage of birds) gives
the male a definite advantage in sexual selection
and mate attraction. Mating coloration and
behavior of the most "fit" and aggressive males
serves to stabilize the population density
because only the most sexually select males are
able to mate with females of the species.
Left A male frigatebird (Fregata magnificens)
photographed on North Semour Island in the
Galapagos Archipelago. The male uses his bright
red, inflated throat pouch (gular sac) to attract
a female. The male sits in the branches of a tree
or shrub and waits for a female to fly over. On
sighting a female he turns his head up to expose
his red pouch, shakes his wing vigorously and
makes a loud, resonating courtship call. If the
female is impressed she will land next to him.
62Batesian Mimicry
- Mimicry One insect (called a mimic) that is
perfectly palatable to its predator resembles
another insect (called the model) that is quite
disagreeable to the same predator. There are
actually two types of mimicry Batesian and
Mullerian. Mimicry in which the mimic is
essentially defenseless is called Batesian
Mimicry. A harmless moth (Aegeria) is a Batesian
mimic because it is incapable of stinging another
animal, but yet it resembles the yellow jacket
wasp (Vespula). Mimicry in which the mimic shares
the same defensive mechanism as the model is
called Mullerian mimicry. The yellow jacket wasp
and bumblebee (Bombus) are Mullerian mimics
because they both have bright yellow and black
colors and use powerful stings as a defensive
mechanism.
63Automimicry
- In automimicry, an animal mimics parts of its own
body. For example, some snakes have a tail that
resembles their head and a head that resemble
their tail. A predatory bird swooping down on its
prey might miss its capture when the prey
suddenly moves in an unexpected (backwards)
direction. Automimicry is well developed in
Malaysian lanternflies of the large insect order
Homoptera. Since they are not true flies of the
order Diptera, the word fly is not written as a
separate word. If they were true flies, their
common name would be written as lantern fly.
Some of these remarkable insects have tails with
false eyes and antennae, and heads with false
tails. The false tail is actually a long
extension of the head between the eyes. What
appears to be the front is really the rear end
and vice versa. When the insect moves it appears
to jump backwards.
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65POPULATION DYNAMICS
- Introduction to population dynamics
- Intraspecific competition
- Interspecific competition
- Predator Prey Dynamics
66Introduction to Population Dynamics
- Our working definition for a population is a
group of individuals of the same species that are
capable of interacting with each other in a
localised area. Four fundamental processes
determine the change in population size (births,
deaths, immigrations and emigrations). Knowing
this, we can write the fundamental equation of
population change as - Nt1Nt births - deaths immigration -
emigration. - This equation reads as the numbers at time t1
(Nt1)are determined by the numbers at time t
(Nt) plus births and immigrants - deaths and
emigrants. This equation always predicts the
population change from one time step to the next.
Five concepts are at the centre of population
ecology. These are 1) population growth, 2)
population equilibrium, 3) limitation, 4)
regulation and 5) persistence. Population growth
is defined as the change in population size from
one generation to the next. A population is at
equilibrium if it does not change in size through
time. Limitation is the processes that set the
equilibrium and regulation is the process by
which a population returns to its equilibrium.
The regulatory processes act in a density
dependent manner. That is deaths increase and/or
births decrease with increasing density.
Population persistence requires that density
dependent processes operate.
67Intraspecific Competition
- Intraspecific competition occurs when two or more
individuals of the same species strive for the
same resource. Intraspecific competition can be
of scramble (resources divided equally) or
contest (resources divided unequally). Under
scramble competition, all individuals suffer
equally as resources become depleted. Under
contest competition, there are winners and
losers. Intraspecific competition has effects on
individuals that cascade up to the population
level. At the individual level, competition for
resources can affect development, fertility and
survival. At the population level, intraspecific
competition for resources can give rise to
"logistic" population growth. However, this
density dependence is only a necessary condition
for population stability. It is not sufficient to
always lead to stable population dynamics.
Changes in the strength and/or type of the
intraspecific competitive process can lead to a
range of population dynamics from stable
equilibrium to stable limit cycles and chaos. The
effects of intraspecific competition can be
observed in many populations. For example, in the
winter annual Vulpia fasciculatus increases in
density lead to a reduction in seed production.
The effect of density dependent regulation leads
to a predicted population of about 3,500 plants.
Under low seed survival (a density-independent
process) the equilibirum population size can be
reduced to about 100 plants. This highlights the
role that density-dependent and
density-independent process have on limiting
(setting) the equilibrium of a population.
68Interspecific Competition
- Interspecific competition when individuals from
different species compete for a single resource.
Under interspecifc competition both species may
suffer reductions in growth rate or only one
species may be affected (amensalism). Extensions
of the logistic population growth model show that
the effects of interspecific competition can be
described by competition coefficients. This is
the ratio of the decrease in growth (of species
1) due to species 2decrease in growth (of
species 1) due to species 1. If the ratio is less
than one then a species inhibits its population
growth more than the population growth of its
competitors. Under this condition coexistence is
possible. Zero-isoclines and phase-plane analysis
can be used to determine the outcome of
interspecific competition. - There are four possibilities 1) species 1
outcompetes species 2, 2) species 2 outcompetes
species 1, 3) the outcome depends on initial
abundances of species 1 and 2 and 4) the outcome
is coexistence. One prediction is that species
that share the same ecological niche can coexist
unless the intraspecific competitive effects
outweigh the interspecific effects. Additional
ecological factors such as the presence of
natural enemies (e.g. predators, parasites) or
the availability of refuges can mitigate the
outcome of interspecific competition. Mechanistic
models of interspecific competition predict that
the best competitor is the one that is most
efficient at harvesting the limiting resource.
69Predator Prey Interactions
- The key questions in predator-prey interactions
are firstly whether predators limit prey
populations and secondly whether predators
regulate prey populations. Two theoretical
frameworks have been developed to explore
predator-prey interactions. The discrete-time
Nicholson-Bailey model was formulated
specifically to examine the interaction between
insect hosts and their specific natural enemies,
parasitic wasps. This model predicts diverging
oscillations in the dynamics of host and wasp
populations. These oscillations are the result of
the lag in the response of the wasp population to
changes in the host population (the numerical
response). Lotka and Volterra independently
formulated a more general continuous-time
predator-prey model. This model predicts neutral
cycles in which the predator population lags the
prey population by 1/4 of a cycle. Again, the
oscillatory dynamics arise due to the numerical
response of the predator to prey. Although
predators limit prey populations, they do not
regulate prey to a stable point. Additional
ecological processes such as prey intraspecific
competition, complex functional responses or prey
refuges are necessary for stable predator-prey
interactions. More complex predator-prey
interactions such as apparent competition,
intraguild predation and trophic cascades require
an understanding of the processes and mechanisms
of predation and interspecific competition.
70Population Growth
- All populations undergo three distinct phases of
their life cycle - growth
- stability
- decline
- Population growth occurs when available resources
exceed the number of individuals able to exploit
them. Reproduction is rapid, and death rates are
low, producing a net increase in the population
size. - Population stability is often proceeded by a
"crash" since the growing population eventually
outstrips its available resources. Stability is
usually the longest phase of a population's life
cycle. - Decline is the decrease in the number of
individuals in a population, and eventually leads
to population extinction.
71Factors influencing population growth
- Nearly all populations will tend to grow
exponentially as long as there are resources
available. Most populations have the potential to
expand at an exponential rate, since reproduction
is generally a multiplicative process. Two of the
most basic factors that affect the rate of
population growth are the birth rate, and the
death rate. The intrinsic rate of increase is the
birth rate minus the death rate.
Two modes of population growth. The Exponential
curve (also known as a J-curve) occurs when there
is no limit to population size. The Logistic
curve (also known as an S-curve) shows the effect
of a limiting factor (in this case the carrying
capacity of the environment).
72Energy flow Primary production
54.2
- Primary Production
- Nonorganic source energy converted to organic
chemical energy by autotrophs - Measurement (per unit area per unit time)
- Energy (Joules / m2 / yr)
- Biomass - organic molecule dry weight (g Carbon /
m2 / yr) - Primary production sets the spending limit for
the ecosystems energy budget - 1 of the available visible light energy is
converted to chemical energy by photosynthetic
organisms! - A few systems depend entirely on chemosynthetic
primary production
73II. Energy and the ecosystem
- Primary production capture of light energy and
its conversion into energy of chemical bonds in
carbohydrates by plants, algae, and some bacteria - Primary productivity rate at which primary
production occurs - Gross primary productivity (GPP) the total
energy assimilated by plants through
photosynthesis - Net primary productivity (NPP) the total energy
assimilated by plants through photosynthesis
minus energy used in respiration - ? NPP represents energy in an ecosystem
available to consumers - ? NPP usually expressed in g/m2/year
- incorporation of any material into the
tissues, cells and fluids of an organism
74Trophic Levels - Definitions
1 Primary producer Autotrophs that support all
other trophic levels by synthesizing sugars and
other organic molecules using light energy.
2. Primary consumers Herbivores that consume
primary producers.
3. Secondary consumers Carnivores that eat
herbivores.
4. Tertiary consumers Carnivores that eat other
carnivores.
5. Detritivores Consumers that derive energy
from organic wastes and dead organisms.
75II. Energy and the ecosystem
- Ecological pyramid of energy
- ? width of each bar represents the net production
of each trophic level - ? ecological efficiency of energy transferred
across trophic levels - ? efficiencies are 20, 15 and 10 between
trophic levels
76Biomass Pyramid
77Trophic pyramids
- Trophic efficiency (TE) of production
transferred from one trophic level to the next - TE less than PE because 2 losses arent included
for PE - energy produced by the next lower level but not
actually consumed - unassimilated food at the present level (lost in
urine, feces) - 80-95 of energy is lost between each level not
consumed, not digested, respired - Compounding of loss throughtrophic pyramid
explains why food webs usually have only four or
five trophic levels
Fig. 54.11
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79Number pyramids
- Predators are usually larger than the prey they
eat - Limited biomass at the top of an ecological
pyramid is concentrated in a relatively small
number of large individuals - Top predators are particularly vulnerable to
extinction
Fig. 54.13
80Energy Flow in Ecosystems
Ecological efficiency Ratio of net
productivity at one trophic level compared to net
productivity at the level below. Ecological
efficiencies are 5-20
81Energy flow through trophic levels
54.3
- Secondary production
- Chemical energy in consumers food converted to
new chemical energy (growth of new consumer
biomass) - Amount ultimately determined by
- NPP
- Efficiency of energy transfer between trophic
levels, usually 5-20
82Secondary Production
- Production efficiency
- of a consumers assimilated food that goes into
growth - Range 1 to 40
- Ex PE 33/10033
- Unassimilated food doesnt count in calculation
because it is available to other consumers
Heat
eaten by caterpillar
Detritivores
Fig. 54.10
83II. Energy and the ecosystem
- Only 5 to 20 of energy passes between trophic
levels - ? net production of one trophic level becomes
the ingested energy of the next higher level - ? amount of energy reaching each trophic level
depends on - NPP at the base of the food chain
- efficiencies of energy transfer at each
trophic level -
-
Ricklefs Fig. 6.2
84Production efficiencies
PE 1-3
PE 10
PE 40
85Energy Budget
primary producers 15-70 of assimilated energy
used for maintenance
herbivores and carnivores 80-95 of
assimilated energy used for maintenance
86Energy Budget
Net production efficiency () growthenergy
in offspring assimilated energy
birds lt 1 small mammals up to 6 cold blooded
animals 75
87General Rules for Energy Flow through Ecosystems
1) Assimilation efficiency increases at higher
trophic levels
2) Net and gross production efficiencies decrease
at higher trophic levels
3) Ecological efficiencies average about 10
Thus, only about 1 of NPP ends up as production
in the third trophic level
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89WATER CYCLE
90- The Water Cycle (also known as the hydrologic
cycle) is the journey water takes as it
circulates from the land to the sky and back
again. The Sun's heat provides energy to
evaporate water from the Earth's surface (oceans,
lakes, etc.). Plants also lose water to the air
(this is called transpiration). The water vapor
eventually condenses, forming tiny droplets in
clouds. When the clouds meet cool air over land,
precipitation (rain, sleet, or snow) is
triggered, and water returns to the land (or
sea). Some of the precipitation soaks into the
ground. Some of the underground water is trapped
between rock or clay layers this is called
groundwater. But most of the water flows downhill
as runoff (above ground or underground),
eventually returning to the seas as slightly
salty water.
91CARBON CYCLE
92- Carbon exists in the nonliving environment as
- carbon dioxide (CO2) in the atmosphere and
dissolved in water (forming HCO3-) - carbonate rocks (limestone and coral CaCO3)
- deposits of coal, petroleum, and natural gas
derived from once-living things - dead organic matter, e.g., humus in the soil
93- Carbon CycleThe movement of carbon, in its many
forms, between the biosphere, atmosphere, oceans,
and geosphere is described by the carbon cycle,
illustrated in the adjacent diagram. In the cycle
there are various sinks, or stores, of carbon
(represented by the boxes) and processes by which
the various sinks exchange carbon (the arrows). - We are all familiar with how the atmosphere and
vegetation exchange carbon. Plants absorb CO2
from the atmosphere during photosynthesis, also
called primary production, and release CO2 back
in to the atmosphere during respiration. Another
major exchange of CO2 occurs between the oceans
and the atmosphere. The dissolved CO2 in the
oceans is used by marine biota in photosynthesis.
94- Two other important processes are fossil fuel
burning and changing land use. In fossil fuel
burning, coal, oil, natural gas, and gasoline are
consumed by industry, power plants, and
automobiles. Notice that the arrow goes only one
way from industry to the atmosphere. Changing
land use is a broad term which encompasses a host
of essentially human activities. They include
agriculture, deforestation, and reforestation.
95- Before the Industrial Revolution the release of
carbon from fossil fuels was very low. - Now deforestation and burning of fossil fuels.
Has upset the carbon Cycle and caused a sudden
increase in atmospheric CO2.
96NITROGEN CYCLE
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98- Nitrogen is essential to all living systems,
which makes the nitrogen cycle one of Earth's
most important nutrient cycles. - Eighty percent of Earth's atmosphere is made up
of nitrogen in its gas phase. - Atmospheric nitrogen becomes part of living
organisms in two ways. The first is through
bacteria in the soil that form nitrates out of
nitrogen in the air. The second is through
lightning. During electrical storms, large
amounts of nitrogen are oxidized and united with
water to produce an acid that falls to Earth in
rainfall and deposits nitrates in the soil.
99- Plants take up the nitrates and convert them to
proteins that then travel up the food chain
through herbivores and carnivores. When organisms
excrete waste, the nitrogen is released back into
the environment. When they die and decompose, the
nitrogen is broken down and converted to ammonia.
Plants absorb some of this ammonia the remainder
stays in the soil, where bacteria convert it back
to nitrates. The nitrates may be stored in humus
or leached from the soil and carried into lakes
and streams. Nitrates may also be converted to
gaseous nitrogen through a process called
denitrification and returned to the atmosphere,
continuing the cycle
100- Both atmospheric and soil phases.
- Plants cant use Nitrogen out of the air. It must
be in mineral form. - Ammonium ions (NH4-)
- Nitrate ions (NO3-)
- Many bacteria and cyanobacteria convert N2 to
ammonia (NH3). This process is called Nitrogen
Fixation. - Rhizobium bacteria lives in the root nodules of
legumes (peas, beans) and fixes N2 (symbiosis). - Some nitrogen is also fixed by lightning.
- Other bacteria reconverts nitrogen compounds back
to N2 gas.
101- Nitrification
- By aerobic bacteria
- NH3 ? NO2- (ammonia ? nitrite (toxic)
- NO2- ?NO3- (nitrate ? nitrate (plant nutrient))
- Nitrogen compounds ? usable organic molecules
?eaten - Ammonification
- Decomposers convert complex compounds to ammonia
and ammonium ions. - Denitrification
- Anaerobic bacteria convert N2 compounds to N2
gas and nitrous oxide (N2O) ? atmosphere
102Human Effect on the Nitrogen cycle.
- Nitric acid (HNO3) from acid rain.
- Nitrous Oxide from manure and inorganic
fertilizers. - Nitrous Oxide is a greenhouse gas and depletes
the ozone layer. - Mining
- Nitrogen runoff into water can trigger algal
blooms. - Eutrophication.
103Deforestation
- Deforestation is the permanent destruction of
indigenous forests and woodlands. The term does
not include the removal of industrial forests
such as plantations of gums or pines.
Deforestation has resulted in the reduction of
indigenous forests to four-fifths of their
pre-agricultural area. Indigenous forests now
cover 21 of the earth's land surface.
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108- Deforestation is brought about by the following
- conversion of forests and woodlands to
agricultural land to feed growing numbers of
people - development of cash crops and cattle ranching,
both of which earn money for tropical countries - commercial logging (which supplies the world
market with woods such as meranti, teak, mahogany
and ebony) destroys trees as well as opening up
forests for agriculture - felling of trees for firewood and building
material the heavy lopping of foliage for
fodder and heavy browsing of saplings by
domestic animals like goats. - To compound the problem, the poor soils of the
humid tropics do not support agriculture for
long. Thus people are often forced to move on and
clear more forests in order to maintain
production.
109- CONSEQUENCES OF DEFORESTATION Alteration of
local and global climates through disruption of - a) The carbon cycle. Forests act as a major
carbon store because carbon dioxide (CO2) is
taken up from the atmosphere and used to produce
the carbohydrates, fats, and proteins that make
up the tree. When forests are cleared, and the
trees are either burnt or rot, this carbon is
released as CO2. This leads to an increase in the
atmospheric CO2 concentration. CO2 is the major
contributor to the greenhouse effect. It is
estimated that deforestation contributes
one-third of all CO2 releases caused by people. - b) The water cycle. Trees draw ground water up
through their roots and release it into the
atmosphere (transpiration). In Amazonia over half
of all the water circulating through the region's
ecosystem remains within the plants. With removal
of part of the forest, the region cannot hold as
much water. The effect of this could be a drier
climate.
110- Soil erosion With the loss of a protective
cover of vegetation more soil is lost. - Silting of water courses, lakes and dams This
occurs as a result of soil erosion. - Extinction of species which depend on the
forest for survival. Forests contain more than
half of all species on our planet - as the
habitat of these species is destroyed, so the
number of species declines (see Enviro Facts
"Biodiversity").
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112Water pollution is a large set of adverse effects
upon water bodies (lakes, rivers, oceans,
groundwater) caused by human activities. Although
natural phenomena such as volcanoes, storms,
earthquakes etc. also cause major changes in
water quality and the ecological status of water,
these are not deemed to be pollution. Water
pollution has many causes and characteristics.
Increases in nutrient loading may lead to
eutrophication. Organic wastes such as sewage and
farm waste impose high oxygen demands on the
receiving water leading to oxygen depletion with
potentially severe impacts on the whole
eco-system. Industries discharge a variety of
pollutants in their wastewater including heavy
metals, organic toxins, oils, nutrients, and
solids. Discharges can also have thermal effects,
especially those from power stations, and these
too reduce the available oxygen. Silt-bearing
runoff from many activities including
construction sites, forestry and farms can
inhibit the penetration of sunlight through the
water column restricting photosynthesis and
causing blanketing of the lake or river bed which
in turns damages the ecology.
113- Principal sources of water pollution are
- Litter in the Water in the U.K.
- industrial discharge of chemical wastes and
byproducts - discharge of poorly-treated or untreated sewage
- surface runoff containing pesticides
- slash and burn farming practice, which is often
an element within shifting cultivation
agricultural systems - surface runoff containing spilled petroleum
products - surface runoff from construction sites, farms, or
paved and other impervious surfaces e.g. silt - discharge of contaminated and/or heated water
used for industrial processes - acid rain caused by industrial discharge of
sulfur dioxide (by burning high-sulfur fossil
fuels) - excess nutrients added by runoff containing
detergents or fertilizers - underground storage tank leakage, leading to soil
contamination, thence aquifer contamination.
114- Many causes of pollution including sewage and
fertilizers contain nutrients such as nitrates
and phosphates. In excess levels, nutrients over
stimulate the growth of aquatic plants and
algae. Excessive growth of these types of
organisms consequently clogs our waterways, use
up dissolved oxygen as they decompose, and block
light to deeper waters. This, in turn, proves
very harmful to aquatic organisms as it affects
the respiration ability or fish and other
invertebrates that reside in water. - When natural bacteria and protozoan in the water
break down organic material that is run off into
streams, lakes and rivers, they begin to use up
the oxygen dissolved in the water. Many types of
fish and bottom-dwelling animals cannot survive
when levels of dissolved oxygen drop below two to
five parts per million. When this occurs, it
kills aquatic organisms in large numbers which
leads to disruptions in the food chain
115Contaminants Contaminants may include organic and
inorganic substances. Some organic water
pollutants are insecticides and herbicides, a
huge range of organohalide and other chemicals
bacteria, often is from sewage or livestock
operations food processing waste, including
pathogens tree and brush debris from logging
operations VOCs (Volatile Organic Compounds,
industrial solvents) from improper storage Some
inorganic water pollutants include heavy metals
including acid mine drainage acidity caused by
industrial discharges (especially sulfur dioxide
from power plants) chemical waste as industrial
by products fertilizers, in runoff from
agriculture including nitrates and phosphates
silt in surface runoff from construction sites,
logging, slash and burn practices or land
clearing sites
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117- Oil pollution is a growing problem, particularly
devestating to coastal wildlife. Small
quantities of oil spread rapidly across long
distances to form deadly oil slicks. In this
picture, demonstrators with "oil-covered" plastic
animals protest a potential drilling project in
Key Largo, Florida. Whether or not accidental
spills occur during the project, its impact on
the delicate marine ecosystem of the coral reefs
could be devastating.
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122Air Pollution
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125- What is air pollution?
- There are several main types of pollution and
well-known effects of pollution which are
commonly discussed. These include smog, acid
rain, the greenhouse effect, and "holes" in the
ozone layer. Each of these problems has serious
implications for our health and well-being as
well as for the whole environment .
126One type of air pollution is the release of
particles into the air from burning fuel for
energy. Diesel smoke is a good example of this
particulate matter . This type of pollution is
sometimes referred to as "black carbon"
pollution. The exhaust from burning fuels in
automobiles, homes, and industries is a major
source of pollution in the air. Another type of
pollution is the release of noxious gases, such
as sulfur dioxide, carbon monoxide, nitrogen
oxides, and chemical vapors. These can take part
in further chemical reactions once they are in
the atmosphere, forming smog and acid rain.
127- Smog is a type of large-scale outdoor pollution.
It is caused by chemical reactions between
pollutants derived from different sources,
primarily automobile exhaust and industrial
emissions. Cities are often centers of these
types of activities, and many suffer from the
effects of smog, especially during the warm
months of the year.
128- Another consequence of outdoor air pollution is
acid rain. When a pollutant, such as sulfuric
acid combines with droplets of water in the air,
the water (or snow) can become acidified . The
effects of acid rain on the environment can be
very serious. It damages plants by destroying
their leaves, it poisons the soil, and it changes
the chemistry of lakes and streams. Damage due to
acid rain kills trees and harms animals, fish,
and other wildlife.
129- The Greenhouse Effect, also referred to as global
warming, is generally believed to come from the
build up of carbon dioxide gas in the atmosphere.
Carbon dioxide is produced when fuels are burned.
Plants convert carbon dioxide back to oxygen, but
the release of carbon dioxide from human
activities is higher than the world's plants can
process. The situation is made worse since many
of the earth's forests are being removed, and
plant life is being damaged by acid rain. Thus,
the amount of carbon dioxide in the air is
continuing to increase. This buildup acts like a
blanket and traps heat close to the surface of
our earth. Changes of even a few degrees will
affect us all through changes in the climate and
even the possibility that the polar ice caps may
melt.
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134- Ozone depletion is another result of pollution.
Chemicals released by our activities affect the
stratosphere , one of the atmospheric layers
surrounding earth. The ozone layer in the
stratosphere protects the earth from harmful
ultraviolet radiation from the sun. Release of
chlorofluorocarbons (CFC's) from aerosol cans,
cooling systems and refrigerator equipment
removes some of the ozone, causing "holes" to
open up in this layer and allowing the radiation
to reach the earth. Ultraviolet radiation is
known to cause skin cancer and has damaging
effects on plants and wildlife
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139Conservation
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142- Conservation biology is the protection and
management of biodiversity that uses principles
and experiences from the biological sciences,
from natural resource management, and from the
social sciences, including economics. The
conservation movement seeks to protect plant and
animal species as well as the habitats they live
in from harmful human influences . The term
"conservation biology" refers to the science and
sometimes is used to encompass also the
application of this science. The concern of this
branch of biology is to help save the diversity
of life on Earth through applied conservation
research. In the realm of research, biologists
seek creative and effective ways to address a
wide diversity of ecological problems, ranging
from endangered species to regional conservation
planning. This translates to developing better
conservation tools, analyses, and techniques.
143Good conservation policy
- Protection laws for sustainable areas to support
viable populations. - Limit use of areas for particular
industrial/resource use - Prohibit importing of foreign plants/animals,
control measures - Pest education about dumping of household garden
refuse. - Captive breeding programs
- Feral pests/disease controls
- Reduction of introduced species, removal of these
animals from areas - Sufficient water levels/waterways for natural
fish movement. - Rehabilitation of degraded area
- Limit human use and impact on these areas
- Ongoing research on factors affecting these areas
- Animal/plant control, firefighting, education and
sufficient funds for these activities - National parks, nature reserves
- Culling programs
- Decrease and control pollution/dumping into
natural waterways - Control gas emissions and burning
- Control use of chemical affecting the
environment, increase awareness
144Land clearing
145Ecological impact of clearing land
- Breaks landscape into isolated areas that are not
sustainable - Affects water movement increase run off from
surface and waterways - Increase erosion by wind and water
- Affects water table increasing soil salinity and
waterlogging - Breakdown of soil structure and nutrient
depletion - Desertification and local climate change
- Decreased bio-diversity and increase danger of
extinction
146Reafforestation
147Reafforestation reasons
Reduce soil salinity, water tables Prevent
erosion, nutrient leeching Conserve endangered
species, biodiversity Aesthetics (picnic areas,
natural beauty) Improve water quality
(reservoir) Reestablish area after logging,
mining Cultural heritage issues Ethics rights
to destroy other species? Ecosystem stability
food web, nutrient
cycles, mutalism, clean air Source of
medicines or industrial raw materials
148Reafforestation program features
Survival of species adapted to that area Species
with high rate of survival Local species to
support local animal populations Disease
resistant strains Variety of species that
naturally grow together.