True or False?True or False?True or False?True or False?

“Survival of the Fittest” means that the strongest,

fastest, smartest organisms will survive and reproduce.

“Survival of the Fittest” means that the strongest,

fastest, smartest organisms will survive and reproduce.

Consider the following…..

The The OpossumOpossum

A SurvivorA Survivor

The Survivor• Opossums are one of the oldest mammal species

on Earth.• Fossil records show the opossum species has

lived on Earth for more than 100 million years.• Opossums walked (well, waddled) with dinosaurs.

The Virginia The Virginia OpossumOpossum

"Opossum" is derived "Opossum" is derived from the Algonquin from the Algonquin Indian word Indian word apasumapasum, , meaning "white animal." meaning "white animal." A creature without A creature without specialized body specialized body structure or food structure or food preference, the preference, the opossum thrives in opossum thrives in many settings.many settings. It is It is found throughout found throughout Massachusetts, where it Massachusetts, where it is classified as a is classified as a furbearer.furbearer.

The Virginia The Virginia OpossumOpossumDidelphis virginiana

Marsupials• The opossum is a marsupial (like kangaroos).

Marsupials are born before they are fully developed, and continue their growth and development in a pouch on their mother's abdomen.

• There is only 1 species of marsupial in North America: the Virginia OpossumVirginia Opossum.

• Most marsupials were confined by continental drift to the “island continents” of Australia & South America.

• There are over 200over 200 species of marsupials in AustraliaAustralia, including the kangaroo, koala, Tasmanian devil and the wombat.

The female opossum has a pouch like that of a kangaroo. After the baby opossums are born, they spend about 2 months2 months in the mother’s pouch feeding on her milk. Then they move out of the pouch to their mother's back where they spend 4 to 6 weeks4 to 6 weeks.

The opossumThe opossum’’s s wide distribution wide distribution shows that it is shows that it is very successful very successful in (well-suited in (well-suited to) a wide range to) a wide range of environments. of environments.

What are 2 types What are 2 types of environments of environments that do that do notnot have have opossum opossum populations?populations?

Distribution of the

Opossum in North

America

Reasons Why the Opossum Should Be Extinct

So how has the opossum species So how has the opossum species survived for more than 100 million years?survived for more than 100 million years?

It isIt is slowslow-- top speed of 1.7 mph-- top speed of 1.7 mph

It isIt is smallsmall ( 6 to 12 pounds)( 6 to 12 pounds) It isIt is not smartnot smart (one of the smallest brain-(one of the smallest brain-to-body ratios of any land mammal).to-body ratios of any land mammal). It It has tiny teeth & claws has tiny teeth & claws-- -- (not equipped for fighting or self-defense)..

Is it because we’re so

cute?

Nope.

How has the opossum survived ?

1.1. They'll They'll eat anythingeat anything ((theythey’’rere scavengers scavengers). ). They are not food specialists, they are food food generalistsgeneralists..

2.2. TheyThey’’re unusuallyre unusually disease-resistantdisease-resistant..

3.3. They are veryThey are very resistant to resistant to snake venomsnake venom - a dose of - a dose of rattlesnake venom that will kill a rattlesnake venom that will kill a horse barely affects an opossum.horse barely affects an opossum.

4. They have a prehensile tail (able to grasp or hold objects), which they use

for balance and to carry materials.

Opossum carrying nesting materialOpossum carrying nesting material

Baby opossums hanginBaby opossums hangin’’ outout

5. They have an opposable thumb on their hind feet, which makes them good climbers.

6. They are nocturnal (active at night), and are experts at hiding during the day.

7. And…. when threatened by predators, they play dead.

No, itNo, it’’s not really dead. Looks like it, though, doesns not really dead. Looks like it, though, doesn’’t it?t it?

Playing Dead When an opossum is threatened it When an opossum is threatened it hisses and growlshisses and growls, emits a, emits a foul foul orderorder, , vomitsvomits, or, or defecatesdefecates to repel to repel the enemy.the enemy. If these tactics donIf these tactics don’’t work, the opossumt work, the opossum passes outpasses out.. ItIt’’s not an act! Its not an act! It’’s an involuntary s an involuntary reaction to overwhelming danger. The opossum reaction to overwhelming danger. The opossum goes into a goes into a shock-like stateshock-like state; the ; the heart rate heart rate dropsdrops, , body temperature decreasesbody temperature decreases, the , the tongue tongue hangs outhangs out, it, it droolsdrools, it appears dead, it appears dead.. Most Most predators wonpredators won’’t eat dead animalst eat dead animals.. They They’’ll ll sniff around, then leave it alone.sniff around, then leave it alone. After a while After a while (from a minute up to 6 hours) (from a minute up to 6 hours) thethe opossumopossum wakes up & waddles away wakes up & waddles away..

Survival of the FittestSurvival of the FittestSo, the next time someone says, “Survival of the Fittest means the strongest, smartest, fastest organism survives,” remember the

Opossum!!!Opossum!!!

T.Rex (strong)T.Rex (strong) and velociraptors (fast, velociraptors (fast, smart)smart) are extinctextinct, but the opossum lives on!

Survival of the Fittest means the organism that is best suited (is the best match) to its environment will survive and reproduce.

Short-tailed Short-tailed opossum from opossum from BrazilBrazil

Brushtail opossum, Brushtail opossum, TasmaniaTasmania

Murine Murine Mouse Mouse Opossum, Opossum, South South AmericaAmerica

AustraliAustralianan honey honey opossuopossumm

Other Opossum species…

Sugar glider, Sugar glider, AustraliaAustralia

Talking Opossums (not Talking Opossums (not really)really)

Baby opossum swimming Opossum playing dead opossum