Which of these Extinctions are Baulderdash ?.
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Extinction is a natural feature of evolution because for some species to succeed, others must fail. Since life began, about 99 percent of the earth's species have disappeared and, on at least five occasions, huge numbers have died out in a relatively short time. The most recent of these mass extinctions, about 65 million years ago, swept away the dinosaurs and many other forms of life. However, despite such catastrophes, the total number of living species has, until recently, followed a generally upward trend. Today, the extinction rate is increasing rapidly as a result of human interference in natural ecosystems. Primates, tropical birds, and many amphibians are particularly threatened. For the foreseeable future, this decline is set to continue because evolution generates new species far more slowly than the current rate of extinction....and thus it is believed by many that we are currently witnessing the sixth mass extinction.
Photo: American Bison skulls, mid-1870s, waiting to be ground into fertilizer. Courtesy of the Burton Historical Collection, Detroit Public Library.
As a group read the background of the extinct species on the cards provided to you.
Every person at the table should come up with a feasible alternative explanation for the extinction of the species. In doing so you should consider the following:
- The information provided regarding ecology, biology and history of the species.
- The content of lectures regarding extinction and diversity
- Your own background knowledge and creativity.
As a group choose the best two explanations on the table.
Write the true explanation and the two false ones on a piece of paper.
Read explanations to all groups. All groups (one vote per group) are to cast a vote on the best explanation for extinction of each species. A score will be tallied and the group with the most points is the winner.
Scoring – Each vote for the true explanation is awarded to the votee table. Each vote for a false explanation is awarded to the creators table.
Habitat loss and fragmentation – The single largest cause of extinctions currently is due to the disappearance of suitable habitat to sustain viable populations of a species. Small fragments or pockets that are conserved do not consider the habitat requirements of animals when dispersing for breeding and determination of territories or for simple requirements such as adequate nesting sites and food resources to sustain a viable population.
Co-extinction –Organisms that have co-evolved and have a mutuallistic or symbiotic relationship are both at risk of extinction if either is threatened.
One example is the near extinction of the plant genus Hibiscadelphus as a consequence of the disappearance of several of Hawaiian honey creepers, its pollinators. Besides this example, there are several instances of predators and scavengers dying out following the disappearance of species which represented their source of food
Invasive alien species – Invasive alien species may fill a similar niche to an endemic species and cause reduction and extinction through competition for resources. Alternatively alien species may serve as predators to endemic species which have not adapted to the presence of such a predator in their habitat.
Over exploitation – There are many examples of humans over exploiting live animal resources, whether it be for food, fur, feathers, fuel, labour and other precious resources.
Pollution – Which results in direct reduction in the population of a species via toxic effects OR habitat destruction.
Climate change – This is happening already,causing change in micro- and macro- habitat conditions which effectively reduce habitat or cause its loss altogether (e.g pacific islands and glaciers ).
Wildlife diseases – particularly a problem when there is reduced diversity in the gene pool, which can occur due to founder effects, bottle necks or huge reductions in population. The Tasmanian Devil has low diversity within their gene pool and is currently under threat of extinction due to one of the only contagious cancers currently known to science, Devil Facial Tumor Disease (DFTD).
The Quaggawas once found in great numbers in the drier areas on the grassy areas of Southern Africa, but is now extinct. Like Zebras they were social animals living in hierarchical groups.
Because of the great confusion between different zebra species, particularly among the general public, the quagga had become extinct before it was realized that it appeared to be a separate species. The last specimen in captivity died on August 12, 1883 at the ArtisMagistra Zoo in Amsterdam.
It was the first extinct animal to have its DNA studied, which is how researchers determined that in fact it was a sub-species of the plains Zebra and not a separate species as originally thought. Currently there is a breeding project underway to selectively breed the Quagga from Zebras.
What happened to the Quagga?
TRUE EXTINCTION: The quagga had been hunted to extinction for meat, hides, and to preserve feed for domesticated stock. The last wild quagga was probably shot in the late 1870s.
The Passenger Pigeon lived in Eastern North America and was considered the most numerous bird to have ever lived. It bred in large colonies, with up to 100 nests in a single tree. Nesting colonies could cover from 30 up to 850 square miles of forest. The nest was loosely made of small twigs.
One egg was laid and incubated by both parents. Both parents tended the chick, but after 2 weeks, the chick, unable to fly, would be abandoned. The entire flock would depart, and the chicks would drop to the ground. After a few days, the chicks would begin to fly and to care for themselves.
The last nesting birds were reported in the Great Lakes region in the 1890’s and the last individuals reported in Ohio in 1900. The last Passenger Pigeon, named Martha, died alone at the Cincinnati Zoo at about 1:00 pm on September 1, 1914. Who could have dreamed that within a few decades, the once most numerous bird on Earth would be forever gone?
TRUE EXTINCTION: Hunting for sport was probably the main factor that doomed this species, with one report of a hunter tallying 30 000 birds before winning a competition.
Steller's Sea Cowwas discovered in 1741 by the naturalist George Steller., in small populations that lived in the arctic waters around Bering Island. Fossils indicate that Steller's Sea Cow was formerly widespread along the North Pacific coast reaching south to Japan and California.
Up to 7.9 metres long and over four tonnes. Their skin was black and thick like the bark of an old oak. They had no teeth or tusks, only two large bony grinding plates for eating sea grasses in the cold shallow waters they inhabited. Individuals spent the majority of their time feeding or resting.
Gregarious groups of males and females were seen herding and protecting juveniles. Females produced only one calf per breeding attempt with gestation thought to be over one year.
Steller(1751) noted that individuals or herds were often found near the mouths of streams or rivers, which suggests they could not tolerate drinking marine water.
By 1768, less than 30 years after it had been discovered, Steller's Sea Cow was extinct.
TRUE EXTINCTION: They were wiped out quickly by the sailors, seal hunters, and fur traders who hunted them both for food and for their skins. Their fat was used as a butter substitute because it did not go off quickly
ADDED EXTRA: It has also been noted notedthat the intense hunting of sea otters on the Bering Sea islands may have contributed to the final extinction of the Steller's Sea Cow. It is known that sea urchin populations can severely deplete sea grass and algae communities when otters are removed, and as this happened on the Bering Sea islands, the sea cows would have faced a new competitor for food.
Steller's Sea Cow
Dodo’s once inhabited the forests of the islands of Mauritius, 500 miles east of Madagascar. They were monogamous, mating for life and breeding all year. Nesting involved laying a single egg on the grassy parts of the forest floor, which hatched after 49 days, after which both parents were involved in parental care.
In addition to a diet of seeds and fruits, there are sailor accounts of dodos wading into water-pools to catch fish, describing them as "strong and greedy" hunters.
The dodo could not fly and apparently ‘toddled ‘in a stiff way. There aren't many bones preserved today, and only one complete skeleton, which makes it difficult to estimate true proportions but estimates do show that reports of clumsiness were probably exaggerated.
The Dodo was naive to humans and approached visitors without fear. Sailors frequently fed on wildlife from Mauritius while staying there, although it has been said that dodo meat was not particularly tasty
TRUE EXTINCTION - The birds were killed for food by the thousands. The effects of invasive species and the continued use of the birds for food led to its total extinction.
ADDED EXTRA: Ships brought cats, dogs, pigs and monkeys. Which quickly invaded the forests, trampling the nests, frightening the birds and devouring the eggs and young.
At 75-cm the Great Auk was the only auk that was unable to fly due to the atrophy of its wings. They were known as the 'penguin of the north‘ because of their resemblance.
During the winter the Great Auk was at sea and seldom seen. They came ashore on rocky offshore islands only to breed, when they lived in large colonies.
Before 1300, the Great Auk had already disappeared from Norway. By the late 1600s the Great Auk population had dramatically declined due to commercial exploitation for feathers oil and meat. The last Great Auks in Greenland were seen in 1815. After this the only remaining breeding place was the small island of Geirfuglasker off south-western Iceland, which was named after the Great Auk (Geirfugl).
TRUE EXTINCTION: In 1830 the rocky stack of Geirfuglasker, in a blaze of volcanic glory, sank beneath the waves. The last remaining two birds were found nesting on a nearby island and clubbed to death for a collector and their egg stepped on by a sailor in 1844.