Transcript Diapositiva 1

HUMAN ACTIVITIES
AND
THE LOSS OF DIVERSITY
1. Direct Harvesting
• It is the process of collecting or removing animals and plants
from their habitats
Cause:
•Overhunting & overfishing
•Clearing of forests for agriculture
Effects:
• It leads to the extinction or endangered of a species
• Loss of biodiversity
• Disruption of food chains
Examples:
•passenger pigeons (extinction);
•lion, blue whale, tiger, panda…(endangered species)
Positive actions:
•Laws & legislation to protect endangered species
Passenger pigeon
3 billions to 5 billions is the estimated population when Europeans arrived America
Overhunting, and the clearing of forest for agriculture.
Because passenger pigeon was a colonial and gregarious bird and needed
large number of breeding conditions
September 1st, 1914
It disrupted food chains in which passenger pigeons were important part of.
Predators of passenger pigeons decreased in population size, and producer
populations increased.
Endangered Species
Mountain lions and big horn sheep are part of the natural food web in the Sierra
Nevada mountains. The Fish and Wildlife Service recently declared these sheep
an endangered species. This action could lead to the shooting of mountain lions.
1) State one reason placing these sheep on an endangered species list could
lead to the shooting of mountain lions where the sheep live.
To increase the sheep population, the population of its predator, the mountain
lion, would need to be reduced.
OR In order to protect the endangered sheep, any mountain lion found to be
attacking sheep may be shot.
2) State two reasons some people would oppose the shooting of the mountain
lions.
Mountain lions may become extinct.
OR There would be an increase in
competition between sheep and other
herbivores.
OR Ethics because it's not right to kill one
animal to benefit another.
OR It may disrupt the food chain.
3. How might the lack of genetic diversity found in populations of endangered
species hinder their recovery?
If all of the individuals in the small endangered species population are
genetically very similar none may have the particular combination of traits
needed to survive if the environment changes, leading to the loss of the
entire species.
2. Habitat destruction and deforestation
• It occurs when people take over land and forest for their
own use, and species have nowhere to live.
• Cause:
• Human population growth
• Natural resources, land, space and needs increase
• Effects:
•Extinction or endangered of a species
• Loss of biodiversity
•Example: pandas & tigers.
strip mining
Graze
livestock
wildfire
draining a marsh
Human Activities that
Destroy habitats
Logging
clearing woodland
to grow crops
Deforestation
Deforestation of the Rainforest
How the rainforest is destroyed?
•Timber logging
•Plants being burned to clear the land.
How does rainforest deforestation
affect organisms?
•Loss of biodiversity
•Disrupting food chains
•Killing predators, leading to increases
in some animals' populations.
How this destruction can be limited?
•Using better farming methods on land that
is already cleared
•Reforestation
•Laws & legislation to set up protected
areas
a) Two human activities that contribute to the destruction of this habitat
The rainforest is being destroyed by
a) timber logging or deforestation
b) plants being burned to clear the land
d) strip mining
e) graze livestock
b) Three ways the destruction of this habitat has affected plants, humans,
and other animals
These activities affect organisms by:
a) Loss of biodiversity
b) Extinction or endangered of species
c) killing predators, leading to increases in some animals' populations.
d) disrupting food chains and destroying their food supply
c) Two ways to limit further destruction of this habitat
This destruction can be limited by
a) using better farming methods on land that is already cleared
b) Establishing laws and legislation to protect the rain forest
c) Reforestation
The Pine Barrens is a government-protected
environment located on the eastern end of Long
Island.
A proposal has been made to allow a shopping
mall to be built in the middle of the Pine Barrens.
Although the developer has promised jobs for
people in the surrounding communities, some
community members oppose the building of the
mall due to the negative effects it would have on
this fragile ecosystem.
Identify two negative effects this mall would most likely have on the Pine Barrens.
•Clearing the land for the mall would cause a decrease in the amount of plant life or
biodiversity.
•Destroying the plants would reduce the habitat available for some animals.
•The mall will attract more automobile traffic to the area, increasing the amount of
air pollution
Amphibians have long been considered an indicator of the health of life on Earth. Scientists
are concerned because amphibian populations have been declining worldwide since the
1980's. In fact, in the past decade, twenty species of amphibians have become extinct and
many others are endangered.
Scientists have linked this decline in amphibians to global climatic changes. Warmer weather
during the last three decades has resulted in the destruction of many of the eggs produced by
the Western toad. Warmer weather has also led to a decrease in rain and snow in the
Cascade Mountain Range in Oregon, reducing the water level in lakes and ponds that serve
as the reproductive sites for the Western toad. As a result, the eggs are exposed to more
ultraviolet light. This makes the eggs more susceptible to water mold that kills the embryos by
the hundreds of thousands.
3) The term used to identify the worldwide climatic changes referred to in the passage is
A) global warming B) industrialization C) deforestation
D) mineral depletion
4) State two ways the decline in
amphibian populations could disrupt
the stability of the ecosystems they
inhabit.
•Prey populations increase.
•Predator populations decrease
•It reduces the biodiversity in these areas.
•Food chains are disrupted.
3. Imported species
Biodiversity is often reduced when people import an release a species from one
environment into another.
• Cause: They often have no natural enemies in their new environment and
rapidly overpopulate the area
• Effect: Many species become pests
•Loss of biodiversity, endangered species, and extinction
• Examples: rabbits in Australia, Japanese beetles, gypsy moths
How to fight a pest?
• Spraying chemical pesticides
• Introducing a predator species of the pest species
• Finding a disease organism that only affects the imported species
• Setting traps that use chemical scents to attract insects
In July 1997, about 25,000 Galerucella pusilla beetles were released at
Montezuma Wildlife Refuge in western New York State. These beetles eat purple
loosestrife, a beautiful but rapidly spreading weed that chokes wetlands. Purple
loosestrife is native to Europe, but here it crowds out native wetland plants, such
as cattails, and does not support wildlife the way the native plants do. Purple
loosestrife grows too thick to allow birds to nest. Most native insects do not eat it,
leaving little for insect-eating birds to eat. Bernd Blossey, a professor at Cornell
University, spent 6 years in Europe trying to find out what limited the loosestrife
population there.
1) Explain why the introduction of the Galerucella pusilla beetle is an advantage
over the use of herbicides to control the purple loosestrife population.
It will cause water and land pollution
The herbicides might kill other plants besides purple loosestrife
2) Describe one possible environmental problem that may result
from the introduction of the Galerucella pusilla beetle.
The beetle might overpopulate the area and become a pest
The beetle might eat a lot of the other plants instead, and the
native species would not have enough food.
3. How can the introduction of a foreign species lead to the
extinction of species that are native to an area?
•Foreign species may be better adapted.
• Increase of competition
•No natural predators of the foreign species
•Foreign species may carry disease or parasites.