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3.3 Threats to Biodiversity
Section 1:
1. Five mass extinctions
2.
3. Ordovician-Silurian extinction: 85% of all Ordovician species
Devonian: 70-80% of all animals present during that time period
Permian: 90% of marine species and 70% of terrestrial species died out
Triassic: 76% of all marine and terrestrial species and about 110% of all
taxonomic families
K/T: approximately 80% of all species of animals at or very close to the
boundary between the Cretaceopus and Paelogene periods
4.
About 8.7 million (6.5 on land, 2.2 in oceans); no as there are many places in the planet
that are home to species we do not have a means of access to like the deep bottom of an ocean.
5.
The Holocene extinction, otherwise referred to as the Sixth extinction or Anthropocene
extinction, is a name for the ongoing extinction event of species during the present Holocene
epoch (since around 10,000 BCE) mainly due to human activity (habitat destruction, invasive
species, pollution, human overpopulation and over-harvesting). The large number of extinctions
span numerous families of plants and animals including mammals, birds, amphibians, reptiles
and arthropods. We're currently experiencing the worst spate of species die-offs since the loss of
the dinosaurs 65 million years ago.
6.
According to the species-area theory and based on upper-bound estimating, the present
rate of extinction may be up to 140,000 species per year, making it the greatest loss of
biodiversity since the Cretaceous–Paleogene extinction event. Overall, there has been a humandriven decline in the populations of all species by 25% over the past 500 years, but not all groups
have suffered equally. Up to a third of all species of vertebrates are now considered threatened,
as are 45% of most species of invertebrates. Among the vertebrates, amphibians are getting
clobbered, with 41% of species in trouble, compared to just 17% of birds—at least so far. The
various orders of insects suffer differently too: 35% of Lepidopteran species are in decline,
which sounds bad enough, but it’s nothing compared to the similar struggles of nearly 100% of
Orthoptera species (crickets, grasshoppers and katydids, look your last). The problem with such
estimate is that with widespread degradation of highly biodiverse habitats such as coral reefs and
rainforest, as well as other areas, the vast majority are thought to be undocumented( so the rate is
not completely accurate as it is an estimate).
7.
Dramatic change in climate and rate of change in nature's ability to adapt are the two
main reasons. Often times it is a slow buildup like the buildup of CO2 in the ocean, however
there has been a time where the extinction occurred due to a meteorite. Overall, mostly in the
past extinctions occurred due to natural disasters such as massive floods of lava erupting in the
The End Triassic extinction. Current extinctions, however, are being caused by human activities.
8.
Over millions of years, the average time between mass extinctions is 2 to 10 million
years.
9.
One species per million species per year compared to the 2 to 10 million year time frame
between organisms in the past. (i couldn't find anything but this)
10.
Biodiversity recovers 5 to 10 million years after the extinction event. In the most severe
mass extinctions it may take 15 to 30 million years.
Section 2:
1. Hunting
2. Invasive Species
3. Pollution
4. Population Growth
5. Overharvest
Section 3
1. When another plant or animal not native to a location or habitat goes to that habitat and
disrupt the natural order, affecting the food chain, environment, health, and can lead to
the endangerment of other species.
2. Some are deliberately introduced such as rabbits from Normandy, some are unwanted
immigrants or aliens. They can move as their habitat is destroyed and they seek new
ones, or weather causes them to move, or humans move them for trading to deal with a
problem.
3. Destruction of environments, endangering species, changing the habitat, competition,
habitat changes, disrupting natural order, changing food chains, spreading disease.
4. There are programs dedicated to spreading awareness, protections sites are made to limit
the impacts, illegal to bring in certain species in certain areas, captivity sites, community
support, but anything natural is difficult and hard to manage.