Transcript 16 The Biosphere and Ecological Relationships

The Biosphere
A Thin Layer of Life
The biosphere is the thin continuous layer around earth’s surface in
which organisms thrive. This layer is about 20 km thick (10 km above
sea level to 10 km below sea level) and has two divisions: the
terrestrial biosphere (organisms on land) and the aquatic biosphere
(organisms in marine or freshwater). The skin of an apple is like the
biosphere on earth.
Ecosystems
The basic unit that living things are found in is called an ecosystem. An
ecosystem is the living community and the non-living environment the
community lives in a defined place. It has a living part referred to as
the biotic part and a non-living part referred to as an abiotic part. An
ecosystem can be as small as a decomposing log and as large as a lake
or forest.
The Biosphere and Other Spheres
The biosphere, more recently called the ecosphere, is found in and
sustains itself from the other spheres (hydrosphere, lithosphere and
atmosphere).
Ecosphere
The term ecosphere refers to the global ecosystem, the complex web of interactions
between all living organisms on our planet and the non-living environments they
interact with. It’s a term which suggests that our planet is like a living entity which
balances itself to maintain its life support systems. An older term, Gaia, was used to
refer to our planet as this entity. Since Gaia was the pagan goddess representing
mother earth, many scientists have found the term somewhat new-age religious and
have replaced it with the more neutral term, ecosphere, the living planet with
systems to maintain itself.
Biological Organization: 1 Organisms
The basic unit of life is the organism, a single living thing.
Biological Organization: 2 Populations
A population is all the organisms of one kind in a certain area at a
certain time.
Biological Organization: 3 Communities
A community is all the living things in an area at a certain time.
Biological Organization: 4 Ecosystems
An ecosystem includes the living community and the non-living
environment in an area at a certain time.
Biological Organization: 5 Biomes
Biomes are large regions (the size of provinces or larger) with similar
kinds of vegetation and animals. A kind of biome is a boreal
coniferous forest or a desert or a grassland.
Ecology
Ecology is the study of levels of life organization above the organism.
It sometimes is referred to as skin-out biology because it focuses on
living relationships outside of an organism like those between
organisms of the same kind, different kinds or relationships with nonliving parts of the environment.
Skin-out Biology vs
Skin-in Biology
Any study of the insides of
an organism are skin-in
Biology while ecological
studies are skin-out studies.
Food Chains
A food chain shows a limited eating relationships of a few organisms. All
food chains begin with a producer (green plant) or detritus (wastes or
remains or an organism). A consumer is an organism that must eat another
organism or detritus. An herbivore eats plants only. A carnivore eats
animals only. An omnivore eats both plants and animals. The arrows in a
food chain point towards the eater, away from the eaten. Each eating level is
referred to as a trophic level.
Energy Chains
Organisms make and eat food for energy to stay alive. Thus a food
chain really shows how energy is passed from the source (the sun)
through the organisms in an environment.
Detritus Food Chains
When a food chain begins with organic wastes or dead remains
(detritus), it is called a detritus food chain.
Energy is Lost in Food Chains as Heat
Since organisms use energy to digest, absorb, and live (giving it off as heat)
and since all the organisms at one tropic level are not eaten by the next
highest trophic level, the energy passed on to each higher trophic level is
about only 10% of what the lower trophic level had. Organisms eating at the
highest trophic level have the lowest amount of energy available to them.
Why Energy is Lost from Lower to Higher Trophic Levels
An organism uses energy to stay alive so this is not passed on. An
organism gives off food wastes so the energy in them is not passed on.
Finally, not all organisms of a trophic level are eaten so the energy in
the survivors is not passed on to the next highest tropic level.
Food Webs
A food web shows the eating relationships for a large number of
different species in a given ecosystem. Single organisms are really
part of many interconnected food chains.
Food Webs Provide Stability
Because of food webs with many interconnecting food chains, an organism
can adjust to eating other food sources if some particular food source
becomes scarce. This allows the scarce food organism to recover in
numbers. Thus a food web helps to bring stability and balance to an
environment, helping to keep all organisms alive and thriving.
Greater Food Web Complexity Provides Greater Stability
The more complex the food webs in an environment, the more stabile
the environment will be in terms of providing food for all organisms
and keeping their numbers in balance.
Unstable Human-made Environments
The most common way to grow agricultural crops is to grow them in
massive fields which makes it easy to harvest with machines. These
environments tend to be unstable because there is little or no food
web but rather, one food chain. To maintain a single food chain,
humans use chemical pesticides (to kill insect pests) and herbicides (to
kill competing weeds
Unstable Human-made Environments
If agriculture developed food webs rather than food chains, the
systems would be much more stable, requiring no chemical poisons.
Food Pyramids
A food pyramid is a
graphical representation of
all the organisms in an area
for each of the trophic levels
in that area.
Pyramid of Numbers: Its Inaccuracy
Food pyramids of numbers of organisms in each tropic level do not show the
true importance of each tropic level because a single individual of one tropic
level is given equal importance with a single individual in another tropic
level. A single tree is much more significant than a single small aphid yet
they count the same in a pyramid of numbers.
Pyramids of Biomass: Equate the Biomasses of Different Species
A pyramid of biomass equates 1 g of a producer with 1 g of a consumer.
Biomass pyramids give a more accurate picture of the relationship between
trophic levels but it can also give an inaccurate picture if a herd of bison
suddenly eats lots of the grasses which would make the second trophic level
(herbivore weight) larger than the first trophic level (grass weight) in the
environment at this moment in time.
Energy Pyramids : Most Accurately Show Trophic Relationships
Energy pyramids measure the
energy (kcal) found at each
trophic level. This is the most
accurate comparison because 1
kcal of producer is equivalent to
1 kcal of consumer (1 kcal in one
thing is the same amount of
energy as 1 kcal in another
thing). Energy pyramids always
have the largest values for the
lowest trophic levels
(producers), tapering to smaller
and smaller values
(approximately a 90% reduction
for each trophic level – each
level having approximately 10%
of the level below it).
Comparison of Food Pyramids
A food pyramid best shows the true relationship between trophic
levels when it is an energy pyramid.
Why are the largest animals herbivores?
Large animals (like elephants) are herbivores because, being large,
they require large amounts of energy and there is more energy at the
herbivore trophic level than the carnivore trophic level.
Why do top carnivores have smaller litters than herbivores?
Because top carnivores have less energy available due to eating at the
top of the energy pyramid, they tend to have smaller litters (typically
one or two, depending on food availability) while herbivores eating at
lower trophic levels have enough energy to have larger litters (six or
more is common for rabbits).
Human Diet and Trophic Levels
When humans feed as herbivores (vegetarian diet), they have more
energy available for their populations. When humans feed as
carnivores (meat diet), less energy is available for the entire
population since energy has been used by the animals that are eaten.
The Energy and
Material to Make a
Hamburger
Meat costs more and
uses more energy and
materials to produce
than grain.
Why are the world’s largest populations more vegetarian?
India and China have the world’s largest populations. Their diets are
more vegetarian than meat-based. Why? There is not enough energy
in the domestic animals of these countries to support their large
populations but as they eat plants and plant products, there is more
energy available to support their large populations.
Vegetarians Save Food Energy and Reduce CO2 and CH4 Emissions
By consuming plants rather than consuming an animal that eats
plants, vegetarians are saving food energy. In addition, vegetarians
reduce their carbon footprints (amount of CO2 and CH4 produced to
sustain a person over a year) which helps reduce global warming.
Polenta – corn dish
Vegetarian Diets Are Healthy
Vegetarian diets have been shown to have benefits for a person’s
circulatory system, improving circulation, reversing problems (see
insert on coronary angiogram) and helping to reduce weight.
Reasons Why People Choose More Vegetarian Diets
The majority of persons who begin to eat more vegetarian do so in
order to be more healthy. A second reason is that they are concerned
about the way farmed animals are treated or they may feel that they
do not want to eat other sentient beings, that can sense and feel.
Risks With the Typical North American Diet – Fat and Sugar
The typical North American diet which included many sugary and fatty foods
(cookies, muffins), many deep-fried foods (fries, chicken, fish, donuts), many
sugary drinks (juices, soda pops), many salty and fatty foods (potato chips,
munchies) and many meat-based dishes contributes to obesity and many
health problems like circulatory diseases (heart attacks), stroke, diabetes,
and kidney disease.
How well do you understand energy relationships?
Imagine yourself in a space ship travelling with just chickens, their eggs and
some popcorn seeds to feed the chickens. These items are your only food.
As an astronaut aboard this ship, you can choose what to eat and in which
order to eat the corn, chickens or eggs. What order of eating these three
items would be the best order to sustain you the longest on your space
voyage?
Energy and Matter Movements in an Ecosystem
Energy flows through ecosystems, powering weather, powering living
things, turning to heat and then escaping to space. Energy has an
overall linear flow, sun to earth systems/living things to space. Matter
on earth cycles from one form to another and eventually can come
back to its original form, being used again and again.
Biogeochemical Cycles
A biogeochemical cycle is a pathway that a particular element
(nutrient) takes through the biosphere, the lithosphere, hydrosphere
and atmosphere. The cycle of a nutrient shows how it is used and
passed on from one place on earth to another until eventually is
returns to where it began. These cycles involve biological, geological
and chemical processes so the terms biogeochemical cycle is used.
Carbon
Carbon atoms are a fundamental unit in cells of all living things. Carbon
is also an essential part of chemical processes that sustain life.
Plants are made of carbon
Animals are made of carbon:
Carbon Storage
Carbon is stored in
many different
locations. Short-term
shortage is found in
aquatic and terrestrial
organisms, and in CO2
in the atmosphere
and top layers of the
ocean. Longer-term
storage is found in
middle and lower
ocean layers as
dissolved CO2, and in
coal, oil and gas
deposits in land and
ocean sediments.
(c) McGraw Hill Ryerson 2007
Trapped Carbon
Sedimentation traps
many long-term
stores of carbon.
Layers of soil and
decomposing organic
matter become
buried on land and
under the oceans.
(c) McGraw Hill Ryerson 2007
Trapped Carbon Changes to Fossil Fuels
Slowly, under great pressure over many years, coal, oil and
gas
form.
Carbon
stores are also known as carbon sinks
(c) McGraw
Hill Ryerson
2007
Carbon can become Rocks
Carbonate rocks (like
limestone) are another
form that carbon takes
when carbon dioxide
reacts with water and
dissolved minerals like
calcium or
magnesium.
Layers of shells also are
deposited in
sediments on the
ocean floor, forming
carbonate rocks like
limestone over long
periods of time.
(c) McGraw Hill Ryerson 2007
Plants Absorb Carbon in the form of Carbon Dioxide
Plants perform photosynthesis in which energy from the sun puts
together CO2 and H2O to form glucose, a sugar, a carbohydrate.
• CO2 + H2O + sunlight  C6H12O6 + O2
• Photosynthesis also occurs in cyanobacteria and algae in
oceans.
(c) McGraw Hill Ryerson 2007
Carbon from plants to animals to the air
Cells perform respiration in which they use oxygen to burn glucose and
release its energy for them to use.
C6H12O6 (from plants) + O2  CO2 (to air) + H2O + energy
The energy released is used for growth, repair and other life
processes.
(c) McGraw Hill Ryerson 2007
Carbon Cycles (Is Used and Reused Over and Over)
Carbon moves from air to plants to animals to dead remains in ponds,
lakes and oceans to rocks to fossil fuels to cars and factories to the air
again.
Decomposer Role in Carbon Cycle
Decomposers
break down the
carbon
compounds in
organic wastes
and dead
organisms.
Carbon is
released from
decomposition
as CO2 gas.
Carbon Cycling Through Ocean Currents
Ocean Processes: CO2 dissolves in cold, northern waters and sinks.
These currents move into the tropics and rise to replace warm surface
waters in the tropics which then move towards the north pole. This
process is called ocean mixing.
(c) McGraw Hill Ryerson 2007
Volcanoes and Fires Cycle Carbon
Volcanic eruptions
release CO2 from
earth rocks.
Forest fires also
release CO2 from
organic matter.
(c) McGraw Hill Ryerson 2007
Human Influence on the Carbon Cycle
Since the start of the Industrial Revolution (160 years ago), CO2 levels
have increased by 30% from the increased burning of fossil fuels.
The increase in CO2 levels in the previous 160 000 years was 1% 3%.
(c) McGraw Hill Ryerson 2007
Human Influence on the Carbon Cycle
Carbon is being removed from long-term storage more quickly than
it naturally would as we mine coal and drill for oil and gas.
(c) McGraw Hill Ryerson 2007
Human Influence on the Carbon Cycle
CO2 is also a greenhouse gas, which traps heat in the atmosphere.
(c) McGraw Hill Ryerson 2007
Human Influence on the Carbon Cycle
Greenhouse gases allow shorter wavelengths of light energy through
but reflect longer wavelengths (infrared). When sunlight energy is
absorbed, shorter wavelength light is converted into longer
wavelength light which is reflected back by greenhouse gases.
(c) McGraw Hill Ryerson 2007
Human Influence on the Carbon Cycle
Clearing land for agriculture and urban development reduces
plants that can absorb and convert CO2. Farmed land does
not remove as much CO2 as natural vegetation does.
(c) McGraw Hill Ryerson 2007
The Carbon Cycle
The greatest carbon sink (storage form)is in rocks of the earth’s crust.
The next largest carbon sink is in deep ocean sediments.
The Oxygen Cycle
Air is about 21% oxygen gas, O2 . Oxygen gas in the stratosphere reacts with high
energy radiation to form ozone, O3 . Oxygen gas is used by respiring organisms to
form carbon dioxide gas (CO2 ) and water (H2O) . Oxygen gas also reacts with rocks
to weather them, forming oxide compounds. When organisms die, their dead bodies
have compounds with oxygen in them and these may be buried in sediments which
slowly release oxygen over time in the forms of carbon dioxide, oxygen gas or other
compounds. The oxygen cycle is in many places linked with the carbon and nitrogen
cycles.
The Element Nitrogen
Nitrogen is very important in the structure of DNA and proteins. In
animals, proteins are vital for all functions, especially muscle
function. In plants, nitrogen is important for functions like growth.
(c) McGraw Hill Ryerson 2007
Forms of Nitrogen on Earth
The largest store of nitrogen is in the atmosphere in the form gaseous
N2. Approximately 78% of the Earth’s atmosphere is N2 gas. Nitrogen
combines with oxygen to form nitrates (NO3- ) and with hydrogen to
form ammonia (NH3) and the ammonium ion (NH4+). It is made into
proteins, DNA and RNA by plants and animals. In these various
forms, nitrogen is found in oceans and soil. Smaller nitrogen stores
are found in terrestrial ecosystems and waterways.
(c) McGraw Hill Ryerson 2007
Nitrogen Fixation
A group of land plants called legumes can change air N2 into
the plant nutrient, nitrate (NO3-). In natural waters,
cyanobacteria convert N2 into nitrate. Nitrate is a plant
nutrient absorbed from the soil by plant roots. Legumes
have special bacteria in their roots that make nitrates from
nitrogen gas in the soil.
(c) McGraw Hill Ryerson 2007
Nitrogen is cycled through processes
involving plants
1. Nitrogen fixation occurs when a legume plant allows itself
to become infected with the rhizobium bacteria. The
legume plant feeds the rhizobium bacteria and the
bacteria makes the legume nitrates from nitrogen gas.
The swellings on legume roots where rhizobium bacteria
live are called nodules.
(c) McGraw Hill Ryerson 2007
Nitrogen is cycled through processes
involving plants
1. In nitrogen fixation there is a mutualistic relationship
between the Rhizobium bacteria and the legume plant since
they both help each other.
(c) McGraw Hill Ryerson 2007
Nitrogen is cycled through processes
involving plants
1. Different legumes have a common flower structure. They do not require
fertilizers like other agricultural crops. Legumes put nitrates back into the soil
so they naturally make soil more fertile. Legume plants include beans, peas,
clovers, alfalfas, peanuts, broom, lupines, locust trees etc.
(c) McGraw Hill Ryerson 2007
Nitrogen is cycled through processes
involving plants
1. Nitrification is a process in which special soil bacteria change ammonia
and nitrite into nitrate which is then absorbed (uptake) by plants.
(c) McGraw Hill Ryerson 2007
Nitrogen Fixation by Lightning
• The energy in a lightning flash converts some N2
in air into nitrate which dissolves in and falls
with atmospheric rain.
(c) McGraw Hill Ryerson 2007
Fires and the loss of nitrates.
• Forest and ground fires heat up the soil,
converting nitrates back into nitrogen gas, N2 .
Volcanoes also convert nitrates in magma into N2
.
(c) McGraw Hill Ryerson 2007
The Nitrogen Cycle (continued)
• Excess nitrogen dissolves in water, enters the
waterways, and washes into lakes and
oceans.
 The nitrogen
compounds
eventually
become trapped in
sedimentary rocks,
and will not be
released again until
the rocks weather.
See page 81
(c) McGraw Hill Ryerson 2007
Human Impact on the Nitrogen Cycle
• Due to human activities, the amount of nitrogen in the ecosystem has
doubled in the last 50 years. Burning fossil fuels and treating sewage
releases nitrogen oxide (NO) and nitrogen dioxide (NO2). Burning also
releases nitrogen compounds that increase acid precipitation in the
form of nitric acid (HNO3).
(c) McGraw Hill Ryerson 2007
Human Impact on the Nitrogen Cycle
• Agricultural
practices often
use large
amounts of
nitrogencontaining
fertilizers.
Fertilizers
change to
nitrates and
these add
nitrogen to
water run-off
from the fields
which gets into
rivers and
streams.
(c) McGraw Hill Ryerson 2007
Human Impact on the Nitrogen Cycle:
Eutrophication
This promotes huge growth in aquatic algae = eutrophication. These algal
blooms use up all CO2 and O2 and block sunlight, killing many aquatic
organisms. The algal blooms can also produce neurotoxins that poison
animals.
(c) McGraw Hill Ryerson 2007
The Phosphorus Cycle
• Phosphorous is essential for life processes in plants and animals.
– Phosphorous is a part of the molecule, ATP, that carries energy in living cells.
– Phosphorous promotes root growth, stem strength and seed production.
– In animals, phosphorous and calcium are important for strong bones.
(c) McGraw Hill Ryerson 2007
The Phosphorus Cycle
Phosphorous is not
stored in the
atmosphere. Instead, it
is trapped in phosphates
(PO43–, HPO42–, H2PO4–)
found in rocks and in the
sediments on the ocean
floor.
(c) McGraw Hill Ryerson 2007
The Phosphorus Cycle
• Weathering releases phosphates from rocks.
• Weathering is the breakdown of rocks mainly
through the action of water and oxygen.
– Chemical weathering, via acid precipitation or
lichens, releases phosphates.
(c) McGraw Hill Ryerson 2007
The Phosphorus Cycle
Physical
weathering, is
where wind,
water and
freezing release
the phosphates.
Phosphates are
then absorbed by
plants, which are
then eaten by
animals.
Weathering
doesn’t occur
until there is
geologic uplift,
exposing the rock
to chemical and
physical
weathering.
(c) McGraw Hill Ryerson 2007
The Phosphorous Cycle
• Humans add excess phosphorous to the
environment through mining for fertilizer
components.
• Humans
can also
reduce
– Extra phosphorous, often with extra
potassium,
then
phosphorous
enters the ecosystems faster than methods
cansupplies.
replenish
 Slash-and-burning of
the natural stores.
forests removes
phosphorous from trees,
and it then is deposited as
ash in waterways.
See page 85
(c) McGraw Hill Ryerson 2007
Imitating God’s Way: Recycle
God has established cycles in nature so that there is no overall build-up of
wastes. All living things are created to depend on each other. We are NOT
independent or self-sufficient.
(c) McGraw Hill Ryerson 2007
Imitating God’s Way: Recycle
When a person presumes to dispose or “throw away” wastes, there is no
“away”. When too much of a nutrient is piled up somewhere, the overall
balance is destroyed.
(c) McGraw Hill Ryerson 2007
Imitating God’s Way: Recycle and
Don’t Plunder the Planet
Humans need to reduce their use of nutrients (reduce what we buy and the
wastes we produce) and they need to recycle materials just like God has them
recycle in His creation.
(c) McGraw Hill Ryerson 2007
A
A
A
A
A
A
A
A
A
A
A
A
A
A