why do species become rare and extinct? the answer is people. the main reasons for the rarity and...
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Why do species become rare and extinct?• The answer is people. The main reasons for the rarity and
extinction of species are:• uncontrolled commercial hunting.• loss of habitats.
Rarity and extinction
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Rarity and extinction
How species become depleted and extinct?1. Rise and fall of species • Extinction is a natural process. As the planet’s surface and climate
have changed over million years, species have disappeared and new ones have evolved to take their places.
• Evidence indicates that over the past 600 million years, there have been: periods of mass extinctions that have reduced Earth’s
biodiversity. periods of radiations that have increased the diversity of life.
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Rarity and extinction
How species become depleted and extinct?2. Extinction of species today• Past mass extinctions, 600 million years ago, took place slowly
enough to allow new forms of life to arise as adaptations to an ever-changing world.
• Since agriculture began about 10,000 years ago, the rate of species extinction has increased sharply as human settlement have expanded worldwide.
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Rarity and extinction
How species become depleted and extinct?2. Extinction of species today• Scientists warn that if deforestation and desertification, and
destruction of wetlands and coral reefs continue at their present rate, within the next few decades we will lose at least 2% and perhaps 25% of Earth’s species forever.
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Rarity and extinction
How species become depleted and extinct?Differences between the present mass extinction and those in the past
Such rapid present extinction cannot be balanced by speciation because it takes between 2,000 and 100,000 generations for new species to evolve.
Point of differences Present mass extinction
Past mass extinction
Cause It is caused mainly by human activities.
It is caused by catastrophes.
Length of time It takes place in only a few decades.
It takes place in thousands to millions of years.
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Rarity and extinction
How species become depleted and extinct?Endangered and threatened species today
Point of differences Endangered species Threatened species
Number is few individual survivors, below its natural range, so that the species could soon become extinct .
is still abundant in its natural range but is declining in numbers and likely to become endangered.
Examples Javan rhino (60 left), California condor in the US (only 2 in the wild), giant panda in china (1,000 left), snow leopard in central Asia (2,500 left).
Bald eagle, grizzly bear.
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Rarity and extinction
How species become depleted and extinct?Threatened species today
Grizzly bearBald eagle
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Rarity and extinction
How species become depleted and extinct?Endangered species today
Giant pandaSnow leopard
California condor Javan rhino
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Loss of (threats to) biodiversity
How biodiversity become lost?Introduction• Species loss may be 1,000 times higher than at any time in the past
100,000 years.• Extirpation (local extinction) is the loss of a single population of a
species.• Extinction is the irreversible loss of all populations of a species.
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Loss of (threats to) biodiversity
How biodiversity become lost?1. Habitat (ecosystem) loss• The greatest threat to most wild species is destruction and
fragmentation of their habitats.• Deforestation is the greatest cause of the decline in or loss of
biodiversity.
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Loss of (threats to) biodiversity
How biodiversity become lost?1. Habitat (ecosystem) loss• Rapid urban development threatens biodiversity and ecosystem
services.
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Loss of (threats to) biodiversity
How biodiversity become lost?2. Commercial hunting and poaching• There are three main types of hunting:
1. Subsistence hunting: is the killing of animals to provide enough food for survival.
2. Sport hunting: is the killing of animals for recreation.3. Commercial hunting: is the killing of animals for profit from
sale of their furs or other parts of the body.• Illegal commercial hunting or fishing is called poaching.
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Loss of (threats to) biodiversity
How biodiversity become lost?2. Commercial hunting and poaching• Commercial hunting and poaching of the African elephants are
reaching crisis levels.• In 1970, there were about 4.5 million African elephants.• By 1990, there were only about 650,000 left.• Gabon has lost a third of its forest elephants over the past decade.• Elephants are killed for their tusks.
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Loss of (threats to) biodiversity
How biodiversity become lost?3. Pest control• Extinction or near extinction can
also occur when people attempt to exterminate (destroy) pest species that compete with human for food.
• For example, fruit farmers exterminated the Carolina parakeet in the US around 1914 because it fed on fruit crops.
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Loss of (threats to) biodiversity
How biodiversity become lost?4. Decorative plants• Some species of plants, especially orchids and cacti are endangered
because they are gathered illegally for decoration in houses and offices.
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Loss of (threats to) biodiversity
How biodiversity become lost?5. Invasive (alien or exotic) species• Invasive species are species that are intentionally or accidently
introduced to new geographical regions.• Invasive species
• compete with native (original) species.• prey on native species.• parasitize native species.
• This allows invasive species to dominate their new ecosystem and cause the extinction or near extinction of native species.
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Loss of (threats to) biodiversity
How biodiversity become lost?6. Pollution, global warming and climate change• Human activities produce diverse pollutants that affect biodiversity:
• The water cycle transfer pollutants from terrestrial to aquatic ecosystems.
• The release of chemicals into the atmosphere promoted the thinning of the ozone layer.
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Loss of (threats to) biodiversity
How biodiversity become lost?6. Pollution, global warming and climate change• Increased global temperatures (global warming) caused by rising
concentrations of greenhouse gases are changing the climate.• Wildlife and even best-protected and best-managed wildlife
reserves are affected by the climatic changes caused by global warming.
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Loss of (threats to) biodiversity
How biodiversity become lost?6. Pollution, global warming and climate change• Global warming is also caused as a result of burning of fossil fuels.• High levels of CO2, methane and nitrous oxide produced from
burning of fossil fuels trap heat, causing global warming.
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Loss of (threats to) biodiversity
How biodiversity become lost?6. Pollution, global warming and climate change• Climate changes cause catastrophic wildfires.
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Loss of (threats to) biodiversity
How biodiversity become lost?6. Pollution, global warming and climate change• Earlier arrival of warm temperatures in the spring is disrupting
ecological communities:• Birds and frogs have begun their breeding seasons earlier.• Migratory birds may experience mismatches, arriving after
peak food availability has already passed. • The range of disease-carrying mosquitoes has increased.
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Conservation Biology
Conservation biology is the science that seeks to• understand the loss of biodiversity.• assess the threats posed by human activities.• protect populations and endangered species
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Conservation Biology
Approaches to wildlife conservation and management• Conservation efforts are increasingly aimed at sustaining
• species (species approach).• ecosystems and landscapes (ecosystem approach).
• Landscapes are interacting ecosystems.• wildlife management.• human development
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Conservation Biology
Sustaining species seek to• preserve endangered species by identifying them and giving them
legal protection in their native habitats.• propagate species in captivity and reintroducing them in their
natural habitats.• preserve organisms of critically endangered species by establishing
gene banks, botanical gardens and zoos.
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Conservation Biology
Approaches to wildlife conservation and managementSustaining ecosystems seek to• preserve balanced populations of species in their native habitats.• protect habitats by establishing legally protected parks, wilderness
areas, protectorates and other reserves.• eliminate invasive species.
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Conservation Biology
Approaches to wildlife conservation and managementSustaining ecosystems• Movement corridors connecting isolated habitats may be helpful to
fragmented populations.
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Conservation Biology
Approaches to wildlife conservation and managementSustaining wildlife management seeks to• Manage species for sustained yield by using laws to regulate
hunting.• Manage migratory birds by preserving their routes of migration and
preventing overhunting.
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Conservation Biology
Approaches to wildlife conservation and managementSustaining development seeks to• improve human condition.• increase ecological knowledge and the values of linking human with
biosphere.
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Conservation Biology
Approaches to wildlife conservation and managementSustaining development • We are most likely to
• appreciate what we understand.• Save what we appreciate.
• Now is the time to work toward long-term sustainability.
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Conservation Biology
You should now be able to• Describe the components of biodiversity.• Describe the significance of biodiversity.• Describe the greatest current threats to biodiversity.• Describe the causes and consequences of global warming.• Explain why the efforts to save threatened and endangered species
from extinction.• describe the efforts to maintain and conserve biodiversity. • Explain why sustainable development should be the ultimate goal
for the long-term maintenance of human societies and the ecosystems that support them.