Transcript Chapter 18: The Biosphere and Human Effects

Chapter 18: The Biosphere and
Human Effects
The Biosphere
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The biosphere is the sum of all places where we find life on Earth.
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Humans pollute the environment, depositing high amounts of wastes, toxins like mercury
and pesticides, as well as greenhouse gases.
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We cover more and more of the land with our homes, factories and farms, leaving less
habitat for animals.
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We compete with other species for resources, overharvest resources, and introduce
exotic species to nonnative habitats.
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Are we the first species to have a profound impact on impact on the environment? NO!!!
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But we are the first to have the capacity to recognize our role in this fast-paced change
and do something about it.
Factors Affecting Climate
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Global Air Circulation Patterns
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Climate refers to the average weather conditions over a long period
 Latitude ( distance north or south) determines how much sunlight a region receives (equator receives
more than poles)
 These differences in sunlight and, therefore, warming of the surface, results in global patterns of air
circulation and rainfall.
1.
At the equator, intense sunlight warms air and causes evaporation of ocean water.
2.
Air expands due to heating and rises and flows north and south.
3.
As air travels away from the equator, it cools, which means it can hold LESS moisture.
4.
Moisture then leaves the air, supporting tropical rainforests.
5.
When air reaches about 30 north and south latitude, it has cooled (causing it to sink downward)
and lost most of its moisture. As a result, deserts form around 30 latitude.
6.
As air travels, it begins to pick up heat and moisture. At a latitude of 60, the air is warm and
moist and so it rises again, dropping moisture in the process.
7.
By the time it reaches the polar regions, it has cooled again and lost most of its moisture,
resulting in sparse precipitation and vegetation, forming polar deserts (arctic tundra).
Air Circulation Patterns
Factor Affecting Climate
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Ocean Currents
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Water, like air, expands when it is warmed.
Since it is heated more at the equator, sea level at the equator is about 3 inches higher
than at the poles.
The water, from this slope, begins to move “downhill” from the equator toward the
poles.
This causes the circulation of the ocean currents.
In addition, the force of major winds, Earth’s rotations, and underwater mountains and
trenches determine the direction that these currents move.
Surface currents circulate clockwise in the Northern Hemisphere and counterclockwise
in the Southern Hemisphere.
These ocean currents affect climate.
Ocean Circulation Patterns
Types of Ecosystems
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A biome is a large-scale ecosystem characterized by specific climate conditions and main
types of vegetation.
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These different types of plant life, in turn, determine the kinds of animals that can be
found in a particular biome.
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Each type of biome can be found on more than one continent.
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There are typically 6-7 types of biomes:
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Deserts
Grasslands and Chaparrals
Tropical Rain Forests
Deciduous Broadleaf Forests
Coniferous Forests
Tundras
Deserts
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Cover about 1/5 of Earth’s land
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Less 30 cm (11 inches) of rainfall annually
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Most common plants include cacti and succulents that store water in their
tissues or shrubs with deep roots
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Animals possess adaptations that reduce water loss, include reptiles,
insects, birds, small mammals
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Low humidity results in rapid heating and cooling (unlike other biomes
whose moisture in the air slows heating and cooling)
Desert
Grasslands and Chaparrals
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Grasslands
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Present on interior of continents between deserts and temperate forests
Examples include shortgrass and tallgrass prairies
Warm summers and cold winters
25-100 cm (10-40 inches) of rainfall annually- too little to support a forest
Grazing animals and periodic fires keep trees and and shrubs from taking hold
Low growing plants that tolerate high winds and periodic droughts
Chaparrals
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Also called dry shrublands
Mild, rainy winters and dry summers
Shrubs adapted to withstand fires caused by lightning (seeds only germinate after exposure
to heat or smoke so that, when they sprout, they have little competition)
Grassland
Chaparral
Tropical Rain Forests
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High temperatures and plentiful rain throughout the year
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Dominated by broad-leaf trees (leafy year-round)
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Layered structure with many vines and epiphytes
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About half of all animal species live in tropical rain forests
Tropical Rain Forest
Deciduous Broadleaf Forests
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Occur in regions where trees can only grow part of the year
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Trees shed their leaves all at once and become dormant during unfavorable
conditions
Temperate Deciduous Forest
Coniferous Forests
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Conifers are the main plants (pines, cedars, and other evergreen plants)
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Conifers have needle-shaped leaves, thick cuticle, and stomata below leaf
surface to help conserve water during drought of when water is frozen
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Conifers can tolerate poor soil and drier habitats
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Boreal forest (or taiga): summers are rainy, winters are long, cold, and dry
(ex. Russia)
Coniferous Forest
Tundras
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Arctic tundra: forms between polar ice caps and boreal forests in Northern Hemisphere
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Snow covered for up to nine months of the year
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Less than 25 cm (10 inches) of rain/snow annually
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Brief summers during which plants grow quickly under continuous sunlight
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Shallow-rooted, low-growing plants since only surface layer of soil thaws during summer (underneath is a layer of
permafrost: a frozen layer of soil up to 500 meters, or 1600 feet, thick)
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Permafrost prevents drainage, so surface layer stays continuously water-logged.
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These conditions result in the anaerobic gradual decay of remains, leading to a build-up of decaying remains.
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Migratory birds nest during the summer when lots of insects fill the air
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Alpine tundra: at high elevations, trees can’t grow, nutrient-poor thin soils so water drains quickly, strong winds,
lichens, mosses, grasses, small-leafed shrubs are the main vegetation
Tundra
Aquatic Ecosystems
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Freshwater Ecosystems: LAKE
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Near shore: sunlight penetrates, aquatic plants and algae attached to bottom
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Open waters: upper well-lit zone (where producers reside= grazing food chain)
and a zone where light does not penetrate (consumers feed on organic debris that
drift down from above = detrital food chain)
Freshwater Ecosystems: STREAMS and RIVERS
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Shallow water flowing rapidly holds more oxygen than slower moving deep water,
cool water holds more oxygen than warm water. This determines the kind of life
that can live in different parts of the stream/river.
Aquatic Ecosystems
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Marine Ecosystems: ESTUARY
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Enclosed coastal region where seawater (salty) mixes with freshwater from rivers
and streams
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Water inflow ensures rich nutrients so estuaries contain many producers
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Serve as marine nurseries for invertebrates and fishes
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Serve as rest stops for migratory birds
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Are threatened by the human diversion of freshwater since they need a constant
supply of freshwater to remain healthy.
Aquatic Ecosystems
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Marine Ecosystems: OCEAN SHORE
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Organisms adapted to mechanical force of waves
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Species underwater during high tide but exposed to air during low tide
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On rocky shores, waves prevent detritus from piling up
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Producers are algae that cling to rocks
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On sandy shores, algae can’t take hold so organic debris from land or
offshore begin detrital food chains
Aquatic Ecosystems
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Marine Ecosystems: CORAL REEFS
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Warm , shallow, well-lit, tropical
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Formations of calcium carbonate secreted by coral (which are invertebrate
animals)
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Wide assortment of species
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Main producers are photosynthetic dinoflagellates
Aquatic Ecosystems
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Marine Ecosystems: PELAGIC ZONE
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Ocean open waters
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Upper brightly lit waters contain photosynthetic algae and bacteria as the
producers= grazing food chain
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Further down, organisms live in constant darkness and organic materials
form the basis of detrital food chains
Aquatic Ecosystems
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Marine Ecosystems: BENTHIC ZONE
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Ocean bottom with its rocks and sediments
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Largely unexplored species rich region at places like seamounts and
hydrothermal vents
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Seamounts are tall underwater mountains that attract many fishes and
invertebrates, many that evolved there and live nowhere else.
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Areas around hydrothermal vents contain great diversity since prokaryotes can
use the mineral deposits from these vents for energy and these serve as the
producers for underwater food webs including invertebrates such as tubeworms
and crabs.
BENTHIC ZONE
Human Effects on Biosphere
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Increased species extinctions:
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The success of humans is currently causing a mass extinction
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Endangered species: a species that aces extinction
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Threatened species: likely to become endangered in the near future
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Nearly all endangered and threatened species hold this status due to human activity.
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We overharvest animals (more rare species go for a higher price on the black market).
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We destroy, degrade, and fragment habitats.
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An endemic species (one that is confined to limited area in which it evolved0 is more
likely to go extinct than one that is widely distributed.
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We introduce exotic species that outcompete native ones.
Human Effects on Biosphere
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Desertification:
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Plowing under natural grasslands for farming or using them for livestock grazing
causes the grassland to develop desert-like conditions. This process is called
desertification.
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Loss of vegetation results in topsoil being blown away.
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Also, with fewer plants, less water enters the air and local humidity and rainfall
decrease, resulting in drought.
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This is what caused the Dust Bowl in the 1930’s.
Human Effects on Biosphere
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Deforestation: removal of trees threatens forest biomes
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There is a staggering loss of tropical forests in Asia, Africa and Latin America
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This results in extinction of forest species and flooding and landslides
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This will have an effect in highly industrialized nations as well since we use products
from these rainforests.
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The disappearance of tropical rain forests could also alter the global atmosphere since
there will be decreased use of CO2, resulting in a buildup of this greenhouse gas in the
atmosphere.
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Ironically, concerns about greenhouses gases released by burning fossil fuels is
encouraging rainforest destruction since large areas of rainforest are being cut down to
grow soybeans and palms to produce biodiesel.
Human Effects on Biosphere
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Acid rain
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A pollutant is a natural or man-made substance released into soil, air, or water in
greater than natural amounts. It disrupts the physiological processes of organisms.
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Coal burning power plants and factories emit sulfur dioxides into the air. Vehicles and
power plants that burn gas and oil release nitrogen oxides into the air.
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In moist air, these oxides combine with water and form acid rain and snow.
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Typically, rainwater has a pH of about 5. Acid rain can have a pH of 3-4, meaning it is
10 to 100 times more acidic than normal rainfall.
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Aquatic organisms cannot tolerate such a drastic change in pH, causing fish species
such as those over 200 lakes in the New York Adirondack Mountains to disappear.
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Acid rain also burns the leaves of trees and changes the composition of the soil, which
weakens and kills plants.
Human Effects on Biosphere
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Water pollution
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Industrial chemicals, fertilizers, animal wastes, sewage, and other pollutants wash into rivers,
lakes, and streams.
Some of these pollutants come from a point source, or a source that is easily identifiable and
easier to control.
Others, however, come from a nonpoint source, such as pollution from cars. These sources of
pollutants are harder to control because it takes the cooperative action of many people.
These chemicals disrupt the metabolic activities of organisms.
Also, due to bioaccumulation, these toxins become increasingly concentrated as they move up
the food chain.
Eutrophication, the nutrient enrichment of aquatic ecosystems, usually due to fertilizer runoff,
sewage, and animal waste that enter water, can cause “explosions” of algae and other
photosynthetic protists, which can deplete the water of oxygen when the protists die and
aerobic bacteria in the water use up all of the oxygen feeding on their remains.
Sediments from runoff from deforested areas can clog gills and choke filter feeders. They can
also prevent light from entering the water, preventing photosynthesis.
Human Effects on Biosphere
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Trash
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Chemicals from buried trash contaminate groundwater.
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Trash dumped in the ocean disturbs marine ecosystems.
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In 2006, the U.S. produced 251 million tons of garbage, about 4.6 pounds per
person.
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Very little of this is recycled.
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Much of it ends up in the ocean due to runoff.
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Once in the ocean, it persists for a very long time.
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A disposable diaper or fishing line will last for more than 100 years, a plastic bag
will last more than 5o years, and a cigarette filter will last more than 10 years.
Human Effects on the Biosphere
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Air Quality
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Burning of fossil fuels and industrial processes sends a constant stream of particles into the
sky.
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These particles are then breathed in by animals all the way into the lungs.
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This burning of fossil fuels also increases the amount of ozone (O3) in the air near the
ground, which irritates the eyes, increases the effects of allergens, and slows plant growth.
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Ozone forms when nitrogen oxides and volatile organic compounds are exposed to sunlight.
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Warm temperatures speed up this process, resulting in ground level ozone concentrations
being higher during the day and in the summer.
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Some of this ozone production can be averted by filling your gas tank and driving or using
gas-powered machines during the evening, when there is less sunlight to catalyze the
formation of ozone.
Human Effects on the Biosphere
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The Ozone Hole
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Ozone is “bad nearby, but good up high.”
Essentially, this means that, while there are problems associated with ground level
ozone, ozone is very beneficial to us in the atmosphere.
Between 17 and 27 kilometers above sea level there is a very high concentration of
ozone in the atmosphere. Scientists call this the ozone layer.
This layer benefits us in that it absorbs most of the UV radiation from the sun.
Since this UV radiation is mutagenic, it is very beneficial that the ozone layer keeps it
from reaching the Earth.
In the mid-1970’s, scientists noted that the ozone layer was beginning to become
thinner from year to year.
By the mid-1980’s the ozone layer had become so thin over Antarctica, it became
known as the “ozone hole”.
Human Effects on the Biosphere
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The Ozone Hole
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This ozone hole allows more UV radiation to reach Earth, causing more skin
cancers for us and also harming wildlife and plants.
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Chlorofluorocarbons, or CFC’s, are the main chemicals that destroy ozone.
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Due to the thinning of the ozone, countries worldwide agreed in 1987 to phase
out the production and use of CFC’s.
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However, since these chemicals degrade so slowly, scientists expect that their
levels will remain high enough in atmosphere to impair the ozone layer for several
decades.
The Ozone Layer and the Ozone Hole
Human Effects on the Biosphere
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Global Climate Change
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The warming of our climate worldwide is affecting ecosystems.
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Weather patterns are changing as temperatures rise.
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Warmer temperature result in extremely heavy rains followed by periods of
drought.
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Warmer seas result in more violent hurricanes.
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Scientists have correlated the rise in temperature that being observed worldwide
with a rise in greenhouse gases in our atmosphere.
Global Climate Change
Human Effects on the Biosphere
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Effects of Climate Change
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Rises in sea level due to melted glaciers and increased volume due to expansion of
water as temperatures rise put coastal communities at increased risk for flooding
and erosion.
It also causes seawater to seep into aquifers that provide fresh drinking water to
these coastal areas.
In fact, sea level has risen 10-20 cm (4-8 inches) during the 20th century.
Scientists predict that sea level could rise up to two feet during the next century if
the trend continues.
In the U.S., that would put over 5,000 square miles of land under water at high
tide.
Human Effects on the Biosphere
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Effects of Climate Change
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Warming in temperate and polar latitudes is more pronounced that at the equator
and this warming is having a more dramatic effect in these areas.
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Warmer springs are causing deciduous trees to sprout leaves earlier and flowers
to flower earlier.
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Animal migration and breeding times are also shifting.
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Species diversity is also changing in areas since warmer temperatures are allowing
some species to move to higher latitudes.
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Animals that cannot move will be driven to extinction by these higher
temperatures. (ex. Coral)
Maintaining Biodiversity
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Includes the genetic diversity, species diversity, and ecosystem diversity in a region
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Healthy diverse ecosystems are essential to our survival.
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We depend upon other species for our food, oxygen, as well as topsoil, and removal of
wastes.
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Other species give us medicines and help us to improve our crops.
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A decline in biodiversity is a warning to us that out natural support system is in trouble.
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Indicator species, species that are especially sensitive to environmental changes, can be
monitored to inform us about environmental health.
Maintaining Biodiversity
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Biodiversity is currently in decline at all three levels in all regions.
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The goal of conservation biology is to find ways to maintain diversity and use it to benefit
humans.
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Conservation biologists have to do a sort of “triage” by identifying hot spots that are richest in
native species and are under the greatest threat.
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These hot spots take precedence in worldwide conservation efforts. There have been 867
identified so far.
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The goal is to save representatives of all of Earth’s existing biomes in an effort to maintain
ecosystem processes that naturally sustain biodiversity.
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Some people oppose environmental protections for fear of economic consequences.
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However, these environmental protection efforts can actually help to create new jobs in the
form of, for example, tourism, to keep an area’s economy strong.
Maintaining Biodiversity
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Ecological restoration is designed to restore ecosystems that have suffered such
damage that conservation is not enough.
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An example would be the coastal wetlands in Louisiana.
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These marshes (or bayous) have been damaged by dams and levees built
upstream that hold back sediments that would normally replenish those lost to
the sea.
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Channels have been cut through the bayous to be used for oil exploration and
production, encouraging erosion.
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Rising sea levels threaten to flood the bayous and destroy plant species, as well.
Maintaining Biodiversity
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Ultimately, our goal should be sustainable development.
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Sustainable development involves meeting the needs of the present generation without
sacrificing the needs of future generations.
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In the U.S., the average size of a family has declined while the average size of the home has
doubled since the 1950’s.
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These homes use materials from the environment. For example, the average home contains
500 pounds of copper in its wiring and plumbing
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Nonrenewable mineral resources are used to produce electronic devices. Therefore, trading
up for the newest device is bad for the environment.
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We should reduce consumption and recycle.
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We should also reduce our energy use because even renewable energy resources can harm
species and ecosystems.
Maintaining Biodiversity
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Truly, the unthinking actions of billions of people are the greatest threat to
biodiversity.
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Our collective behavior will determine the future of the planet.
Homework
1.
Pick one biome and draw a food web that contains at least 2 each of
producers, herbivores, carnivores, detritivores and decomposers that live
in that biome. (You don’t have to draw pictures of the organisms, just list
their specific names.)
2.
Discuss the kind of food chain that can be found in a shallow body of
water or at the top of a deep body of water versus the kind of food chain
that can be found at the bottom of a deep body of water. Explain why the
difference in food chains exists in these water ecosystems.
3.
Pick one human activity that you think harms ecosystems the most and
explain why you picked that activity as most harmful.