Natural Selection and Evolution in Bears
Natural selection is "the gradual, non-random process by which biological traits become either more or less common in a population as a function of differential reproduction of their bearers"[1]. This means that natural selection is a long lasting process where organisms with the most useful traits survive and reproduce. Natural selection goes through for stages. 1)Variation. 2) Differential Reproduction 3) Heredity 4)Trait takes over. Bears have been around for about 20 million years. The earliest bear is known as the Ursavus (Dawn Bear). About five million years ago the black bear split off from a common ancestor. This common ancestor may have been the Ursus abstrusus, a bear with very similar fossils to a black bear. The black bear survives many environmental changes such as the ice age. Their survival compared to two other carnivorous bears the Arctodus simus and the Tremarctus floridanus during the ice age might be due to the fact that black bears are omnivores and can eat both vegetation and meat. An example of natural selection in the American black bears might be that the bear's claws adapted to climb trees and rip logs over a long time. The long claws that they have in present day possibly suggests that the black bears who could climb trees were able to survive and pass on their traits. Possibly by being able to get food or protection that was on the tree or in log.
Sources:
-[1]http://en.wikipedia.org/wiki/Natural_selection
-http://evolution.berkeley.edu/evolibrary/article/evo_25
-http://en.wikipedia.org/wiki/American_black_bear#Taxonomy_and_evolution
-http://books.google.com/books?---id=mTPI_d9fyLAC&pg=PA105&lpg=PA105&dq=nervous+system+of+black+bears&source=bl&ots=vKifG-zTdS&sig=oO3kWKyd6BIFntLvLcwbxflLW6Q&hl=en&sa=X&ei=ngu6UazbI6fo0gGd_ICICw&ved=0CDkQ6AEwAQ#v=onepage&q=nervous%20system%20of%20black%20bears&f=false
Speciation in the Black Bear
Speciation is the making of a new species through evolution. There's four ways to undergo speciation but these two are the most important: Allopatric, which is the divergence of a species and sympatric speciation, which are organisms that are similar to each other but not related because they live in the same environment. The American black bear is in the Ursidae family is in a suborder Caniformia. This includes pinnipeds and canids. What sets the black bear apart from these species are having an alisphenoid canal (in the middle of the skull), lacrimal bone (next to eye sockets) is not used anymore and carnassials (ripping meat teeth) are level.
Source:
http://en.wikipedia.org/wiki/Bear#Fossil_bears
Sources:
-[1]http://en.wikipedia.org/wiki/Natural_selection
-http://evolution.berkeley.edu/evolibrary/article/evo_25
-http://en.wikipedia.org/wiki/American_black_bear#Taxonomy_and_evolution
-http://books.google.com/books?---id=mTPI_d9fyLAC&pg=PA105&lpg=PA105&dq=nervous+system+of+black+bears&source=bl&ots=vKifG-zTdS&sig=oO3kWKyd6BIFntLvLcwbxflLW6Q&hl=en&sa=X&ei=ngu6UazbI6fo0gGd_ICICw&ved=0CDkQ6AEwAQ#v=onepage&q=nervous%20system%20of%20black%20bears&f=false
Speciation in the Black Bear
Speciation is the making of a new species through evolution. There's four ways to undergo speciation but these two are the most important: Allopatric, which is the divergence of a species and sympatric speciation, which are organisms that are similar to each other but not related because they live in the same environment. The American black bear is in the Ursidae family is in a suborder Caniformia. This includes pinnipeds and canids. What sets the black bear apart from these species are having an alisphenoid canal (in the middle of the skull), lacrimal bone (next to eye sockets) is not used anymore and carnassials (ripping meat teeth) are level.
Source:
http://en.wikipedia.org/wiki/Bear#Fossil_bears
Darwin's Finches
Darwin noticed allopatric speciation on the Galapagos islands.
Cladogram of a American Black Bear
Taxonomy Of the American Bear Black
Kingdom: Animalia
Phylum: Chordata
Class: Mammals, Fish, Amphibian, Reptiles, Aves (birds)
Order: Rodentia (Rats), Marsupiala (kangaroo), Primates (monkey), Carnivora, Cetacea (whales), Pinnepedia (sea lions), Chiroptera (bats)
Family: Ursidae, Tremarctos ornatus (spectacled bears), Melursus ursinus (sloth bears), Helarctos malayanus (sun bears).
Genus/species: Ursus americanus (American Black Bears), Ursus arctos arctos (European Brown Bears), Ursus maritimus (Polar Bears).
Phylum: Chordata
Class: Mammals, Fish, Amphibian, Reptiles, Aves (birds)
Order: Rodentia (Rats), Marsupiala (kangaroo), Primates (monkey), Carnivora, Cetacea (whales), Pinnepedia (sea lions), Chiroptera (bats)
Family: Ursidae, Tremarctos ornatus (spectacled bears), Melursus ursinus (sloth bears), Helarctos malayanus (sun bears).
Genus/species: Ursus americanus (American Black Bears), Ursus arctos arctos (European Brown Bears), Ursus maritimus (Polar Bears).
Sources:
http://www.enchantedlearning.com/subjects/mammals/classification/
http://animaldiversity.ummz.umich.edu/accounts/Ursus_americanus
http://www.enchantedlearning.com/subjects/mammals/classification/
http://animaldiversity.ummz.umich.edu/accounts/Ursus_americanus