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EARTH SCIENCE 9: CHAP 1-3 Final Unit Test Review Questions

Terms in this set (78)

Deserts are simply barren areas of land where little precipitation takes place, so hot and cold places have these requirements.
-Hot Deserts - are found on every continent around latitudes about 30degrees north and south
-Rainfall < 25 cm annually
-Temp: Hot days =38degC; cold nights=7degC
-Physical Features: Soil: Salty soil because minerals do not get washed away
-Plant adaptations: few plant species in hot
-spiny cacti have thick, fleshy stems that conserve water are common. Their roots extend metres away from the plant to absorb water
-other plants have small, thick, waxy leaves that also store water
- many plants have spines or produce chemicals that protect them from being eaten
PLANT ADAPTATIONS; reptiles are common and have thick skin and scales that prevent water loss.
- animals, such as desert spadefoot toads and scorpions, bury themselves in the ground and sleep during timems of heat and drought
- include the Kalahari and Sahara of Africa, Simpson of Australia, the Atacama of SA, and the Sonoran (USA)

-COLD Deserts - found in dry regions in the interior of continents above 30 deg north latitude and below 30deg south latitude and in the shadows of mountains
-Rainfall < 25 cm annually
-Temp: Summer days av 21-26degC
Winter days av -2to-4deg C
-Physical Features: Soil: most precipitation falls as snow but there is fain in the spring
- soil is salty and little water erosion occurs
Plant Adaptation: only a few plant species in cold deserts
- most are less than 1 m tall
- many plants, such as sagebrush, are deciduous and have spiny leaves
- sagebrush roots can exten 30m and absorb water when available
Animal Adaptation: fan-throated lizards, small mammals such as foxes, coyotes, jackrabbits and pocket mice burrow to escape the cold
-include Great Basin Desert of North America (which includes Canada's Pocket Desert), the Patagonian Desert of Argentina and the Gobi Desert of central Asia
A symbiotic relationship in which both organisms benefit.
-in some mutualistic relationships, 2 species are unable to survive without each other
ie: between certain plants and bees, bats or other pollinators
-moth-pollinated plants often have spurs or tubes that are the exact length of a certain moth's feeding tube
-snapdragon flowers only open for bumblebees that are of a specific mass
-Western red squirrels and northern flying squirrels of the boreal forests of British Columbia feed on an
underground fungus that is critical to the trees' ability to
absorb water and nutrients. After eating the fungus, the
squirrels spread fungal spores in their droppings over the forest floor. The dispersal and growth of the fungus promotes the growth of young tree seedlings.
-In another type of mutualism, one species defends another
species against attacks in return for food and shelter. For
example, in savanna (tropical grassland) biomes, a species of aggressive ant lives in the hollow thorns of the bullhorn acacia bush. The ants sip nectar from the tips of the bullhorn acacia's leaflets. In return for food and shelter, the ants protect the plant by aggressively fighting off other insects and animals by stinging them.
-The most famous example of mutualism is that of lichens. Over 2500 types of lichens exist, and they can be found
in every biome on Earth. Each lichen has an alga (plural: algae) and a fungus that live in a mutualistic relationship with each other. The alga produces sugars and oxygen for the fungus through photosynthesis. In return, the fungus provides carbon dioxide, water, minerals, and protection from dehydration for the alga.
A symbiotic relationship in which one species benefits while the other is harmed.
-Parasites are usually much smaller and more numerous
than their hosts.
-Parasites may live in or on a host and obtain food from
the host's blood or body tissues.
-Usually, the host is not killed, but a parasite can cause a great deal of damage to a host's body and organs,
weakening it and sometimes causing it to die.
-Some parasites can live on different hosts.
-Other parasites can live on only one host.
-There are about 3200 species of parasites that can infect
humans, and 100 of these species are worms.
ie: a type of worm that infects both humans and dogs is called a hookworm. Ancylostoma caninum is the species that infects dogs. Hookworms live in soil and animal feces. When dogs are exposed to soil or feces contaminated with hookworms, these bloodsucking microscopic parasites can penetrate their skin. The hookworm enters the bloodstream and travels to the intestine where it attaches by its teeth to the intestinal wall.
-The mountain pine beetle is a well-known insect parasite that is devastating the lodgepole pine and white pine forests of BC
-Not all parasites are small ie: In the jungles of southeast Asia lives a type of parasitic flowering plant called Rafflesia arnoldii. This plant produces the world's biggest flower, and it lives only on the tetrastigma vine. Rafflesia arnoldii has no leaves or stem, but it has strands of tissue called filaments that grow into the tetrastigma vine to obtain food, which weakens the vine.
1. Herbivores eat large quantities of plants
and carnivores eat many times their body weight of prey during their lifetimes. For this reason, even small concentrations of chemicals in producers
and primary and secondary consumers can build up to cause problems at higher trophic levels.
iE: A red tide is caused by an algae bloom in
which the algae become so numerous that they can turn coastal seawaters red. Red tides produce toxic organic chemicals that can affect organisms such as clams, mussels, and oysters. As the shellfish eat the algae, the toxins
bioaccumulate to a level that is poisonous to other organisms such as fish, humans, and other mammals. If eaten, these shellfish can cause paralytic shellfish poisoning, which can result in serious illness or death
2. PERSISTENT ORGANIC POLLUTANTS (POB'S)
A. . PCBs and Orcas
PCBs (polychlorinated biphenyls) are synthetic chemicals that were widely used from the 1930s to the 1970s in industrial products such as heat exchange fluids, paints,
plastics, and lubricants for electrical transformers. In 1977, they were banned in North America as concerns grew about their impact on the environment and human
health.
-Many synthetic chemicals such as PCBs that bioaccumulate and biomagnify also have a long half-life. Half-life is the
time it takes for the amount of a substance to decrease by half.
-PCBs stay in organisms and the environment a very long time, suppress the immune system, and probably cause cancer in humans. Aquatic ecosystems and species that feed on aquatic organisms are especially sensitive to the effect of PCBs.
Hardest hit of all are orcas (Figure 2.54). One study found that PCBs will interfere with the reproductive success of British Columbia's resident orcas until at least 2030. Even though these chemicals have been banned for decades, orcas retain high levels of PCBs, especially the calves
-Figure 2.55 shows how biomagnification occurs in an orca. -Even if the PCBs enter the food chain at a relatively low level, by the time they get to the orca, they are highly concentrated in the blubber.
-When salmon stocks are low, magnification is increased, since blubber is then burned for energy. The PCBs are released into the orca's bloodstream where they interfere with immune function, making the orca more susceptible to disease.
B. DDT's - One well-known POP is the insecticide DDT (dichlorodiphenyl trichloroethane).
-DDT was introduced in 1941 to control disease-carrying mosquitoes. Although now banned in many countries because it biomagnifies, it has a long half-life and persists in the environment. DDT binds strongly to soil particles and persists for as long as 15 years.
- Bound in soil, DDT begins to bioaccumulate in plants and then in the fatty tissue of the fish, birds, and animals that eat the plants. Washed into streams and lakes, it affects aquatic food chains by first accumulating in plankton.
In Table 2.2, you can see how low levels of DDT become magnified through the food chain.
- Chemical accumulation is measured in parts per million
(ppm). One ppm means one particle of a given substance
mixed with 999 999 other particles, which is equivalent to one drop of dye mixed with 150 L of water (about what a home hot-water tank holds).
-DDT is considered toxic or harmful at levels of 5 ppm. In animals, DDT is changed into a chemical form that bioaccumulates in fat tissue and can cause nervous system, immune system, and reproductive disorders.
3. HEAVY METALS
A. Lead - the lead found in landfills (Figure 2.57).
Lead is extremely toxic. It has an accepted toxic level of
0.0012 ppm, although it is not considered safe at any level.
Lead particles can be ingested (eaten), absorbed through
the skin, or inhaled. Harmful effects in humans may include
anemia (a blood condition), nervous system damage,
sterility in men, low fertility rates in women, impaired
mental development, and kidney failure. Similar effects are
seen in fish and birds.
B. Cadmium - Cadmium is found in Earth's crust and is released into the environment through rock weathering, volcanoes, and forest fires. (The cadmium stored in trees is released into the air when trees burn.)
-Cadmium is also released in the manufacture of plastics and nickel-cadmium rechargeable batteries, and it enters soil and water through zinc production and phosphate ore mining.
-Cadmium is strongly chemically attracted to
organic matter in soil. When present in soil, it can be extremely dangerous, as plants take up the cadmium in their roots and animals eat the plants. Cadmium is highly toxic to earthworms and other soil organisms at very low levels. In fish, it is associated with higher death rates and lower reproduction and growth rates.
-Electronics waste has introduced a large amount of lead into ecosystems.
-For humans, the most serious source of cadmium poisoning is smoking, as tobacco plants easily absorb the metal. Cadmium can accumulate in lung tissue, causing lung diseases such as cancer. Non-smokers ingest cadmium mainly through foods such as mushrooms, shellfish, fish, and seaweed.
-Cadmium moves from the digestive system to the liver and then to the kidneys.
-The half-life of cadmium in the kidneys and in bone tissue is 30 years.
-Cadmium exposure can lead to infertility and damage to the central nervous system, immune system, and DNA.
C. Mercury - Every year, up to 6000 tonnes of mercury are released through natural sources such as volcanoes, geothermal springs, and rock weathering.
-In the last 150 years, this annual amount has doubled through the burning of fossil fuels, waste incineration, mining, and industrial uses such as the manufacture of batteries (including the kind many of us throw out each
week).
-Coal burning accounts for more than 40 percent of mercury released into the atmosphere
-Mercury returns to the Earth in rainfall and dust and binds to soil particles to form compounds that are then transported by air and water.
-Organisms also circulate mercury through the food chain. Some bacteria in soils change compounds such as mercury sulfide into methylmercury, a highly toxic compound that bioaccumulates in the brain, heart, and kidneys of vertebrates.
-In humans, methylmercury is absorbed during digestion, then enters the blood and is stored in the brain. It affects nerve cells, the heart, kidneys, and lungs and suppresses
the immune system.
-In fish, levels of methylmercury depend on what they
eat, how long they live, and how high they are in the food chain.
Marine sediments and sedimentary rock.

The largest long-term stores of carbon are found in marine sediments and sedimentary rock.
Sedimentation is the process that contributes to the formation of sedimentary rock. During sedimentation, soil particles and decaying and dead organic matter accumulate in layers on the ground or at the bottom
of oceans and other large bodies of water. These layers are turned into rock by slow geological processes that take place over long periods of time.
-Some marine sediments and sedimentary rock form from the shells of marine organisms such as coral and clams. These shells contain calcium carbonate (CaCO3). Carbonate is a combination of carbon and oxygen (CO32) that is dissolved in ocean water. -other marine organisms that have shells containing calcium carbonate. The shells accumulate on the ocean floor when the organisms die and form carbonate-rich deposits. In time, the carbonate is changed into limestone, which is a sedimentary rock.

A> SHORT-TERM STORES - found in vegetation on
land, in plants in oceans, in land-based and marine
animals, and in decaying organic matter in soil.
-Carbon
is also found in the atmosphere as carbon dioxide gas
(CO2) and is stored, in its dissolved form, in the top
layers of the ocean (Figure 2.19).
B. LONGER-TERM STORES
a: OCEANS - found in intermediate (middle) and deep ocean waters as dissolved carbon dioxide. In cold ocean waters, this carbon will sink to the ocean floor
and remain for 500 years.
-Eventually, it may be used by bacteria and released again.
b. LAND: On land, long-term stores of carbon are found in
coal deposits and in oil and gas deposits, which formed million of years ago.
-Coal, oil, and natural gas are fossil fuels that are formed from dead plants and animals.
What is Nitrogen fixation?
1) Nitrogen fixation is the process in which nitrogen gas (N2) is converted into compounds that contain nitrate (NO3) or ammonium (NH4).
-Both of these compounds are usable by plants.

In what three ways does nitrogen fixation occur?
Nitrogen fixation occurs in three ways:
1. in the atmosphere
2. in the soil
3. in water bodies

How does atmospheric nitrgen fixation occur?
1) Atmospheric nitrogen fixation occurs when
nitrogen gas (N2) is converted into nitrate
(NO3) and other nitrogen-containing
compounds by lightning (Figure 2.31).

What is lightning and what does it do?
1) Lightning is an electrical discharge of static
electricity in the atmosphere.
2) It provides the energy that is necessary for nitrogen to react with oxygen to form these compounds.
3) Nitrate and other nitrogen-containing
compounds enter terrestrial and aquatic
ecosystems in rain.
-Only a small amount of nitrogen-containing compounds are fixed in the atmosphere as a result of this process.
Figure 2.30 Nitrogen is found in the
proteins that are required for this
skateboarder's muscles to function

How does nitrogen fixation occur in the soil?
1) Nitrogen fixation in the soil occurs when nitrogen gas
(N2) is converted into ammonium (NH4) by bacteria
during the decomposition process.
2) Certain species of bacteria, called nitrogen-fixing bacteria, play a significant role in nitrogen fixation.
-i.e. Rhizobium is a species of nitrogen-fixing bacteria that lives in the root nodules of legumes and some other plants.

What are legumes and what do they do?
1) Legumes are pod-producing plants such as peas, beans, clover, and alfalfa.
2) These plants supply nitrogen-fixing bacteria with sugars, and the bacteria supply the host plants with nitrogen in the form of ammonium (NH4).
-Other plants, such as red alder trees, are also important to nitrogen fixation. Red alder trees live in association with nitrogen-fixing bacteria and are an important tree in forest ecosystems in British Columbia.

How does nitrogen fixation occur in water bodies?
1) Certain species of cyanobacteria in aquatic ecosystems also fix nitrogen into ammonium (NH4).
-Cyanobacteria, as you have learned, are bluegreen bacteria that manufacture their own food during photosynthesis.
-Nitrogen-fixing cyanobacteria make these nitrogen compounds available to plants in the surface waters of oceans, wetlands, and lakes.
Human activities have
1. doubled the available nitrogen in the biosphere in
the past 50 years.
- Millions of tonnes of nitrogen are added to the atmosphere annually in the form of nitrogen oxide (NO) and nitrogen dioxide (NO2) as a result of fossil fuel combustion in power plants and processes such as sewage treatment. Nitrogen is also released during the
burning of fossil fuels in cars, trucks, and other motorized forms of transportation.
-Clearing forests and grasslands by burning also releases trapped nitrogen into the atmosphere. These compounds eventually return to terrestrial and aquatic ecosystems as acid precipitation. Acid precipitation (or acid rain) is formed from dissolved nitrogen compounds in the moisture in clouds and falls back to Earth as nitric acid (HNO3).

2, The use of chemical fertilizers began in the 1800s, expanded in the 1940s, and has grown rapidly since to meet the demands of an increasing human population (Figure 2.39).
-Chemical fertilizers are made through industrial processes that fix atmospheric nitrogen (N2) into nitrogen compounds that crops can assimilate.
-However, crops do not assimilate all of the fertilizer they receive. As a result, excess nitrogen in the form of ammonium (NH4) and nitrate (NO3) can escape back into
the atmosphere as ammonia (NH3) or can be washed or leached from the soil by rain or irrigation water. (Leaching is removal by water of substances that have dissolved in moist soil.)
-Ground water run-off containing these compounds enters lakes and streams. This increased amount of dissolved nitrogen causes eutrophication in aquatic ecosystems. Eutrophication is the process by which excess nutrients result in increased plant production and decay.
-Run-off from acid precipitation also contributes to eutrophication.

3. In a nitrogen-rich, or eutrophic, environment, algae grow
very quickly.
-Excessive algae growth (Figure 2.40) deprives other
aquatic plants of sunlight and of oxygen as algae undergo cellular respiration. When the algae die, the oxygen used in
decomposition also deprives aquatic animals of oxygen and can lead to the death of all fish in a lake.
-Some algae blooms produce neurotoxins that are transferred through the food web to shellfish, seabirds, marine mammals, and humans.

4. In addition to using fertilizers globally, humans are planting large areas to grow single crops of soybeans, peas, alfalfa, and rice.
- Since these crops fix atmospheric nitrogen, they greatly
increase the rate of nitrogen fixation in these areas.
1) Weathering releases phosphate into the soil.
-Weathering is the process of breaking down rock into smaller fragments (Figure 2.43).
A. -Chemical weathering and physical weathering are two types of weathering involved in the phosphorus cycle. In chemical weathering, a chemical reaction causes phosphate rocks to break down and release phosphate into soil. Acid precipitation and the chemicals released by lichens can cause chemical weathering.
B. -In physical weathering, processes such as wind, rain, and freezing release particles of rock and phosphate into soil.
-On land, plants quickly take up phosphate through their roots and animals obtain phosphate by eating the plants.
==> The action of decomposers breaks down animal waste and dead organisms, which returns phosphorus
to the soil to become available for producers again.
How does phosphate enter aquatic ecosystems?
1) Phosphate enters aquatic ecosystems as a result of erosion, leaching, and run-off (Figure 2.44).
2) Water plants take up some dissolved phosphate and pass it through the aquatic food chain (Figure 2.45).
3) However, most phosphate in run-off settles on lake and ocean bottoms and will not enter the biotic community unless the sediment is disturbed.
4) The sediment will eventually form sedimentary rock, and the phosphorus will remain trapped for millions of years.
When is phosphorous made available again when it is stored in rock layers?
1) Only when the rock layers are exposed through a process called geologic uplift will phosphorus be made available, and then the cycle of weathering can begin again.
HEAVY METALS = metallic elements with a high density that are toxic to organisms at low concentrations.
-Within the biosphere, they do not degrade and cannot be destroyed.
-Some heavy metals such as copper, selenium, and zinc are essential to human health in very small quantities.
-Heavy metals can be found in water and air and are taken in through the food chain.
-They can bioaccumulate within organisms and biomagnify,
moving up the food chain like POPs.

The three most polluting heavy
metals are:
1. Lead - the lead found in landfills (Figure 2.57).
Lead is extremely toxic. It has an accepted toxic level of
0.0012 ppm, although it is not considered safe at any level.
Lead particles can be ingested (eaten), absorbed through
the skin, or inhaled. Harmful effects in humans may include
anemia (a blood condition), nervous system damage,
sterility in men, low fertility rates in women, impaired
mental development, and kidney failure. Similar effects are
seen in fish and birds.
2. Cadmium - Cadmium is found in Earth's crust and is released into the environment through rock weathering, volcanoes, and forest fires. (The cadmium stored in trees is released into the air when trees burn.)
-Cadmium is also released in the manufacture of plastics and nickel-cadmium rechargeable batteries, and it enters soil and water through zinc production and phosphate ore mining.
-Cadmium is strongly chemically attracted to
organic matter in soil. When present in soil, it can be extremely dangerous, as plants take up the cadmium in their roots and animals eat the plants. Cadmium is highly toxic to earthworms and other soil organisms at very low levels. In fish, it is associated with higher death rates and lower reproduction and growth rates.
-Electronics waste has introduced a large amount of lead into ecosystems.
-For humans, the most serious source of cadmium poisoning is smoking, as tobacco plants easily absorb the metal. Cadmium can accumulate in lung tissue, causing lung diseases such as cancer. Non-smokers ingest cadmium mainly through foods such as mushrooms, shellfish, fish, and seaweed.
-Cadmium moves from the digestive system to the liver and then to the kidneys.
-The half-life of cadmium in the kidneys and in bone tissue is 30 years.
-Cadmium exposure can lead to infertility and damage to the central nervous system, immune system, and DNA.
3. Mercury - Every year, up to 6000 tonnes of mercury are released through natural sources such as volcanoes, geothermal springs, and rock weathering.
-In the last 150 years, this annual amount has doubled through the burning of fossil fuels, waste incineration, mining, and industrial uses such as the manufacture of batteries (including the kind many of us throw out each
week).
-Coal burning accounts for more than 40 percent of mercury released into the atmosphere
-Mercury returns to the Earth in rainfall and dust and binds to soil particles to form compounds that are then transported by air and water.
-Organisms also circulate mercury through the food chain. Some bacteria in soils change compounds such as mercury sulfide into methylmercury, a highly toxic compound that bioaccumulates in the brain, heart, and kidneys of vertebrates.
-In humans, methylmercury is absorbed during digestion, then enters the blood and is stored in the brain. It affects nerve cells, the heart, kidneys, and lungs and suppresses
the immune system.
-In fish, levels of methylmercury depend on what they
eat, how long they live, and how high they are in the food chain.
a. Natural selection -The process that makes change possible in living things is called natural selection. In natural selection, members of a species having certain characteristics that give them an advantage over
other members of that species will be in better condition to mate.
-These individuals then may pass these favourable characteristics on to their offspring. For example, the slimmer, streamlined shape of the open-water
stickleback is more efficient for escaping predators.
- One of the most famous examples of natural selection is the Galapagos finches. Biologists believe that all 13 species of finches that now inhabit the Galapagos Islands developed from a single species from the mainland of South America

adaptive radiation - Scientists use the term adaptive
radiation to describe the change from a common ancestor into a number of different species that "radiate out" to inhabit different niches. Each species of Galapagos finch is adapted to a particular niche on the ground
or in the trees, and each species gathers and eats a different type of food.
-Finches that are seed eaters, cactus eaters, fruit eaters, and
insect eaters have different beak sizes and shapes, which are adapted for different food sources.
-Another example of adaptive radiation is the cichlid fish of Lake Victoria in Africa More than 300 species of cichlid once lived in this lake. Scientists have researched these species extensively and have determined that they also developed from a single species.
-The development of different species of sticklebacks is also an example of adaptive radiation, as new species of sticklebacks in North America developed from an ancestral species.
b. Primary succession - occurs in an area where no soil exists, such as on bare rock.
-Natural events such as retreating glaciers can scrape existing rock bare, or new rock can form when lava cools after a volcanic eruption. Wind and rain carry the spores of organisms such as lichens to these rocks.
-Earlier in this unit, you learned that a lichen is an organism
that consists of a fungus and an alga. You also learned that lichens obtain nutrients from rock by secreting chemicals that break down the rock. The weathering caused by lichens and by processes such as wind, rain, and
freezing begin the formation of soil.
-As dead lichens decay, they also add organic matter to the developing soil. In time, soil slowly accumulates, a
process that may take hundreds of years in some locations

-pioneer species - is the term scientists use to describe the lichens and other plants that are the first organisms to survive and reproduce in an area.
-Pioneer species change the biotic and abiotic
environment in a variety of ways. They decay and create
more soil. They also make the soil more fertile and increase
its ability to hold moisture. Pioneer species provide food for
insects and other organisms, introducing animals into the
community.
-Each stage in primary succession is gradual and
introduces different populations of micro-organisms, plants,
and animals that compete for nutrients, moisture, and
sunlight. As each generation of plants and animals dies off,
they decompose and contribute more organic matter to an increasing soil layer.
-Eventually, the seeds of trees, which have been transported by animals or carried by wind or water, will germinate.
-The first trees to grow usually require a lot of light, such as deciduous trees in a boreal forest. The shade they cast will change the abiotic conditions again because the soil will become cooler and moister beneath them.
-Only shade-tolerant plants will then be able to survive on the forest floor. As more niches are created, there is greater variety, or diversity, in animals, micro-organisms, fungi, and bacteria. This diversity creates more complex food webs.
Although the types of species differ even in similar zones, scientists have found that primary succession occurs in much the same way in different par.,ts of the world. For example, coniferous forests eventually
form in northern latitudes, deciduous forests form in temperate zones, and tropical forests form in tropical zones.
1. Flooding - occurs in coastal areas, rivers, and lakes, when the volume of water exceeds the ability of the water body to contain it.
-Flooding can be part of a normal cycle or the result of heavy rainfall, increased run-off from melting snow, or an extreme natural event such as a tsunami.
-Flooding can result in soil erosion and soil pollution if toxic chemicals are present in floodwaters.
-Flooding can also cause widespread disease among humans when toxins or harmful bacteria from untreated sewage enter drinking water supplies
-Climate change may be causing an increase in flooding in some parts of the world, such as West Africa, where heavier annual rains are occurring.

2. Tsunamis -Tsunami is the term used to describe a huge, rapidly moving ocean wave.
-Tsunamis are usually caused by large earthquakes or underwater volcanic eruptions.
-On land, the force of the huge wave carries away or destroys plants and animals, disrupting habitats and food webs. The large volume of salt water that is carried onto the shore can also change the composition of
the soil.
- As a result, plants that cannot survive in a salty environment are unable to grow.

3. Drought - is a recurring event in many parts of the world.
-usually occurs when there is a below-average amount of precipitation in an area over a period of many months or years.
-Most often, an ecosystem can recover from drought once normal precipitation patterns are re-established. However, the effects of prolonged drought can destroy habitats when water becomes scarce and plants and animals die. -Drought can result in crop failures and livestock deaths. -Many parts of the world, such as Australia, western Europe, and Africa south of the Sahara Desert, have recently
experienced drought conditions
-These droughts may also have been made worse by climate change.

4. Insect Infestations - Insects play a major role in the natural succession of a forest.
-In a mature coniferous forest, for example, the mountain pine beetle destroys older, weaker pines. The dead trees provide food and shelter for some species, and eventually the nutrients of the tree are recycled in the soil.
-Spruce, fir, and younger pines, which are unaffected by the beetles, thrive in the openings left by dead, fallen trees.
-The beetle is also an important food source for other insects, birds such as woodpeckers and nuthatches, and
for some mammals.
-Younger, healthy trees are better able to defend against beetle infestations by producing resin. Resin traps and flushes the adult beetles out of the tree, which is effective when only a few beetles attack a tree.
=However, if many insects attack, or if the tree is stressed from overcrowding, drought, or grazing by animals, resin flow is reduced.
-The pine beetle has evolved a symbiotic relationship with the blue stain fungus. The beetle carries the fungus from tree to tree in its mouthparts. The fungus destroys plant tissue and prevents the host tree from using resin to sweep away both invaders.
-Events that used to keep the pine beetle population in
check, such as cold winters, are no longer occurring. With the warming trend in the climate, British Columbia's forests are no longer exposed to sustained periods with temperatures below -30°C, which would be required to kill the beetle larvae.
-Human suppression of forest fires has resulted in the retention of large numbers of host trees for the beetles.
Because of their large populations, the pine beetles are now attacking younger trees as well. Since mountain pine beetle populations are no longer in check, their impact on lodgepole pine forests is devastating
- With large losses to the forest canopy, many bird and
mammal nests have been lost.
-The economies of many forest-dependent communities have also been affected.
In northeastern Brazil, the owners of a coffee farm practise
sustainable agriculture and work hard to protect biodiversity.
The coffee plants grown on this farm are thriving in their
natural habitat—in the shade of many fruit and tropical
hardwood trees (Figure 3.24). Growing among a variety of
other plants in a method called polyculture (the prefix
"poly-" means many), these coffee plants benefit from
cooler, moister, and more productive soil. Polyculture
increases the amount of nutrients and helpful microorganisms in soil.
-It also reduces soil erosion and weed invasions. Such plant diversity also protects the coffee plants from the pests and diseases that tend to attack monocultures (single plant crops).
-The variety of plant species on this farm provides food and habitat for native animals and financial security for the
owners because they are not dependent on only one crop.
-Many of the coffee farms in countries such as Brazil have been developed on land that once was lush tropical rainforest.
-Deforestation is the practice in which forests are logged or cleared for human use and never replanted
-Deforestation, especially of tropical rainforests, continues at an alarming rate in many parts of the world.
-reduces the number of plants and animals living in an ecosystem
- results in soil degradation.
-Soil degradation can occur when water and wind erosion removes topsoil from bare land. Topsoil is the upper layer of soil, which is made mostly of humus (decomposed organic matter), minerals, water, and air.
-Most plants require adequate amounts of topsoil in which to grow. Deforestation causes erosion because few plants are left to hold the soil in place. When topsoil erodes, nutrients are taken with it.
-Resource use is also referred to as resource exploitation.
-Examples include harvesting fish and timber, mining coal
and minerals, and extracting oil and gas.
-We depend on resource exploitation to build our homes, put food on our tables, and provide energy to run our cities and industries.
-Resource exploitation also provides jobs for millions of
people around the world
However, exploitation of resources, as you have seen,
can cause habitat loss and soil degradation.
-Resource exploitation such as mining can also affect ecosystems by contributing to ground water and surface water contamination. Contamination is the introduction of
chemicals, toxins, wastes, or micro-organisms into the
environment in concentrations that are harmful to living things.
-For example, cyanide, which is used in silver and gold mining, may enter streams and rivers. Cyanide prevents cellular respiration from occurring in living organisms and is deadly in small doses.
-chemicals used in copper mining are collected in treatment ponds.
-Mine reclamation usually involves the restoration of land and the development of water treatment facilities to remove heavy metals draining from the mine site.
At Britannia Beach, a water treatment facility treats about 12 million litres of run-off daily from the closed copper mine. This process removes about 454 kg of copper and an even greater quantity of other metals each day. It also adjusts the pH of the run-off to acceptable levels. The flow of ground water and surface water from the mine is used to power the treatment plant.
-Mine reclamation often involves the use of plants to restore the land and decontaminate soil and water
Table 3.2 lists some plants that can tolerate contaminated soil. These plants absorb contaminants through their root systems and stabilize the soil to prevent contaminants from leaching into water.
-Ecosystems are negatively affected when resources are overexploited.
-Overexploitation is the use or extraction of a resource until it is depleted.
-Overexploitation can result in extinction. Extinction is the dying out of a species.
Ie: Passenger pigeons, which numbered about 5 billion, were brought to extinction by early North American settlers hunting them for food.
-Overfishing of yellowfish tuna and Atlantic cod during the past few decades has reduced the numbers of these species by 90 percent.
-Overexploitation of species not only affects their numbers, it also results in a loss of genetic diversity. This means that populations are less resistant to disease and less able to adapt to changes in their environment.

The effect of overexploitation on food webs
Overexploitation affects many interactions in food webs, and sometimes the effects take decades to appear.
-The destruction of the kelp forests of the north Pacific Ocean is an example (Figure 3.32).
-Kelp forms dense forests that are important to marine ecosystems because they provide hiding places for many marine animals. Scientists believe that overhunting
of sperm whales and baleen whales in 1946 resulted in the decline of the kelp forest almost 50 years later.
-Sperm and baleen whales were once preyed upon by orcas. Scientists believe that overhunting of whales caused orcas to seek new prey, such as harbour seals, fur seals, sea lions, and sea otters. In the 1970s, the population of harbour seals declined, which was followed in the 1980s by
a decline in fur seals. The food web continued to be affected throughout the 1990s, when the numbers of sea lions and then sea otters decreased.
-By the late 1990s, low numbers of sea otters resulted in an explosion of sea urchins, a primary food source for sea otters.
-With the loss of the sea otter, which is a keystone species, sea urchins reproduced rapidly and have since destroyed the kelp forests.
-Biologists estimate that, at some locations, the average rate of kelp loss due to sea urchin grazing is as high
as 45 percent in one day
1. Eurasian milfoil - likely brought to North America in the late 1800s and was first identified in British Columbia in 1970 in Okanagan Lake.
-It is highly adaptable and thrives in disturbed and contaminated waters. It forms wide, dense mats at lake surfaces, cutting off sunlight to organisms below and interfering with recreational activities.
-It can grow from plant fragments, which are often spread by boats. In the Okanagan, the plant is controlled by rototilling to cut out roots from lake bottoms.
-A native weevil that eats milfoil shows promise as a biological control. The weevils must be cultivated and brought into infested areas in large numbers to be effective.
2. Norway rat
These invaders may have escaped from early European explorer and fur-trading ships. They
are extremely well adapted to almost every environment and feed on almost any food
source, including meat, grain, seeds, fungi, land and marine invertebrates, fish, and birds.
A female rat can produce up to 72 young per year. On Queen Charlotte Islands (Haida
Gwaii), they have caused a decline in ground-nesting sea birds, such as ancient murrelets
and puffins, by eating their eggs and young. Efforts are currently under way to control rat
populations by using poisons in affected areas.
3. American bullfrog
Bullfrogs were brought to British Columbia in the 1930s as a source of frogs' legs for
restaurants. Released into the wild when the industry failed, bullfrogs caused no problems
until about 1990, when they began to breed rapidly. They have since taken over habitats in
the southwest and have eaten so many native frogs that they have made the red-legged
frog an endangered species. Bullfrogs can grow as big as dinner plates and will even
attack ducks and small mammals. On southern Vancouver Island, bullfrogs and their
tadpoles are removed as quickly as possible from an area. It is hoped that this action will
block further spread into a sensitive watershed.
4, European starling
The starling has caused the decline of several bird species including the yellow-billed
cuckoo, western bluebird, and band-tailed pigeon. In the late 1800s, 50 breeding pairs
were brought to North America, and their ability to outcompete native birds for nesting
sites has led to their spread across North America, including tundra biomes. Starlings are a
fast-growing species that exploits many types of nesting sites as well as types of food in a
wide variety of ecosystems. In British Columbia, starlings outcompete western bluebirds for
nesting habitat. They also can devastate fruit crops and grain crops. In some agricultural
areas, the introduction of barn owls has helped control starling populations.

-Sea lamprey -
-Zebra mussels - brought in by boats
-coat bottom of ocean and make phytoplankton die by
One of the most famous examples of natural selection is the Galapagos finches.
-Biologists believe that all 13 species of finches that
now inhabit the Galapagos Islands developed from a single species from the mainland of South America. Scientists use the term adaptive radiation to describe the change from a common ancestor into a number of different species that "radiate out" to inhabit different niches.
-Each species of Galapagos finch is adapted to a particular niche on the ground or in the trees, and each species gathers and eats a different type of food.
-Finches that are seed eaters (Figure 3.3), cactus eaters, fruit eaters, and insect eaters have different beak sizes and shapes, which are adapted for different food sources



On his visit to the Galapagos Islands, Charles Darwin discovered several species of finches that varied from island to island, which helped him to develop his theory of natural selection.

The Galapagos Islands are an archipelago of 13 major islands and more than a hundred smaller islands that straddle the equator off the Ecuadorian coast. They are home to an amazing array of unique animal species: giant tortoises, iguanas, fur seals, sea lions, sharks, rays, and 26 species of native birds--14 of which make up the group known as Darwin's finches. These finches are considered to be the world's fastest-evolving vertebrates because their appearance and behavior quickly adapted to this closed and rapidly changing environment.

Today, Darwin's finches are under attack from an introduced parasitic fly. Earthwatch volunteers helped to catch finches in mist nets (thin nets invisible to birds), measured them, took genetic samples, and recorded damage caused by the parasite before setting them free. They recorded and tested the function of finch song, collected data on the behavior of free-living wild finches, and helped determine the current numbers of finches on the islands. They also helped investigate evolutionary changes in Darwin's finches. All of these activities provided vital information for the action plan being implemented by the Galapagos National Parks to ensure the survival of these iconic finches.